The ratio between the Filtered and Community maximum bacterial abundance (a proxy for top-down control by protistan grazers) showed minimum values at the Seagrass site (1.05 ± 0.05) and maximum at the Phytoplankton site (1.24 ± 0.30), suggesting protistan grazing was higher in open waters, especially in the first half of the year. Since the Mangrove and Seagrass sites shared a similar bacterial diversity, the unexpected lack of bacterial response to predators removal at the latter site should be explained by differences in DOM characteristics. Nitrogen-rich DOM and fluorescent protein-like components were significantly associated with enhanced specific growth rates along the inshore-offshore gradient. Our study confirms the hypotheses that top–down factors control bacterial standing stocks while specific growth rates are bottom-up controlled in representative Red Sea shallow, oligotrophic ecosystems.Despite the key role of heterotrophic bacterioplankton in the biogeochemistry of tropical coastal waters, their dynamics have been poorly investigated in relation to the different dissolved organic matter (DOM) pools usually available. In this study we conducted four seasonal incubations of unfiltered and predator-free seawater  at three Red Sea coastal sites characterized by different dominant DOM sources: Seagrass, Mangrove, and Phytoplankton. Bacterial abundance, growth and physiological status were assessed by flow cytometry and community composition by 16S rRNA gene amplicons. The Seagrass site showed the highest initial abundances (6.93 ± 0.30 × 10 In the tropical, oligotrophic oceans the role of small autotrophic (mostly cyanobacteria) and heterotrophic (bacteria and archaea) prokaryotes is fundamental for carbon budgets and fluxes . In partResource availability (bottom–up control) and mortality by protistan grazers and viruses (top–down control), together with other environmental drivers among which temperature stands out, are the main factors constraining bacterial abundance and metabolism in aquatic ecosystems everywhere e.g., . HoweverThe Red Sea is one of those poorly studied oligotrophic regions. Its central part is generally characterized by low pelagic primary productivity , mostly a) concentrations. The prokaryotic community composition at the three sites was determined through the analysis of 16S rRNA genes. A research on the combined effects of mangrove- and seagrass-originated DOM and temperature in the Great Barrier Reef reported higher exoenzymatic activity, carbon fluxes and growth rates of bacteria exposed to those substrates, especially to mangrove-originated DOM  phytoplankton-originated DOM would yield the lowest BGE values.In order to improve our knowledge about how different autochthonous DOM sources affect bacterioplankton metabolism in the central Red Sea, we conducted four short-term (4–6 days) incubations of epipelagic samples from three sites, each dominated by one of the major DOM sources found in tropical regions , covering a full seasonal cycle, from February 2016 to December 2017. Incubations were performed with and without the presence of protistan grazers and other organisms larger than 1.2 μm in order to elucidate the relative importance of bottom–up and top–down controls on bacterioplankton standing stocks and the growth rates of different bacterial physiological groups . As possated DOM . Based oated DOM , our hypCymodocea serrulata seagrass meadows and the other in the vicinity of a patch of Avicennia marina mangroves) and the other one pelagic (phytoplankton). Hereinafter we will use the names Seagrass, Mangrove and Phytoplankton or their initials  when referring to each site. The Seagrass  and Mangrove  sites were located inside the coastal lagoon, with depths of 1.5–2 m, and the Phytoplankton  site was located offshore the lagoon entrance (Surface (ca. 0.5 m) water was collected from three different sites along an inshore-offshore gradient in a coastal lagoon (Al Monseini), situated between King Abdullah University of Science and Technology (KAUST) and King Abdullah Economic City (KAEC), in the eastern coast of the central Red Sea . The threntrance . Aiming in situ light  and in situ temperature conditions (which were adjusted for each site and season). The aim of the diel cycle of light and darkness in the Filtered treatment was to allow for photoheterotrophy of the natural bacterioplankton assemblages. Samples for inorganic nutrients, dissolved organic carbon (DOC) and nitrogen (DON) concentrations, DOM fluorescence (FDOM) components, bacterial abundance and bacterial physiological properties were collected twice per day to better capture the exponential phase of growth until the abundance of bacteria reached a plateau or started to drop . Incubations lasted up to 6 days, and were stopped when a stationary or decay phase was well-established. We focused on the initial responses and did not consider any secondary growth phases in our calculations, which were inconsistently detected.For each site, experimental incubations of 4–6 days were performed following the seawater culture method . Two difa (Chl a) concentration was measured at each sampling site after sequential filtration of 200 ml samples through polycarbonate (Isopore™ membrane filters) filters of 20, 2, and 0.2 μm pore-size in order to respectively retrieve the micro-, nano-, and picoplankton size-fractions. Filters were kept at –80°C until analysis. Chl a was extracted in 90% acetone for 24 h in dark conditions at 4°C. A Turner Trilogy fluorometer was used to measure Chl a, using the acidification method . Total Chl a was calculated by summing the three size-fractions.Ambient size-fractionated chlorophyll n method  calibrat® polycarbonate filters and stored frozen at –20°C until analysis. A segmented flow analyzer from Seal Analytical® was used to analyze nitrate (NO3–), nitrite (NO2–), and phosphate (PO43–). Detection limits were 0.2, 0.06, and 0.01 μmol L–1 for NO3–, NO2–, and PO43–, respectively. Standards were prepared with a nutrient-free artificial seawater matrix in acid-washed glassware. Consumption and production rates of inorganic nutrients (μmol L–1 d–1) were estimated as the slope of the linear model of nutrient concentrations vs. time during the bacterioplankton exponential growth phases. Positive and negative values correspond to production and consumption, respectively.Samples for nutrient analyses were collected in 15 mL sterile polypropilene Falcon tubes after being filtered through 0.2 μm Millipore® polycarbonate filters. To avoid contamination, filters were pre-washed with 50 mL of 1.2 mol L–1 hydrochloric acid and rinsed with abundant MQ before sample filtration. The initial filtrate was discarded and the subsequent filtrate was used for sample storage and analysis. Each filtered sample was acidified with H3PO4 and kept at 4°C until further analysis by high temperature catalytic oxidation (HTCO) using a Shimadzu TOC-L. Reference materials of deep-sea carbon (42–45 μmol C L–1 and 31–33 μmol N L–1) and low carbon water (1–2 μmol C L–1) were used to monitor the accuracy of DOC and TDN concentration measurements. DON concentrations were calculated after subtracting the dissolved inorganic nitrogen (DIN) to the TDN (DON = TDN – DIN), where DIN (μmol C L–1) = [NO3–] + [NO2–].Samples for DOC and total dissolved nitrogen (TDN) were filtered through 0.2 μm Millipore® polycarbonate filters and measured immediately after filtration. UV-VIS fluorescence spectroscopy was measured using a HORIBA Jobin Yvon AquaLog spectrofluorometer with a 1 cm path length quartz cuvette. Three-dimensional fluorescence excitation emission matrices (EEMs) were recorded by scanning with an excitation range between 240 and 600 nm and an emission wavelength range of 250–600 nm, both at 3 nm increments and using an integration time of 8 s. To correct and calibrate the fluorescence spectra post-processing steps were followed according to 1(Ex2)/Em 252(324)/397 nm /Em 252(366)/467 nm  were estimated as the slope of the fluorescence intensity vs. time during the exponential growth phases. Positive and negative values were considered as production and consumption, respectively. The percentage of protein-like compounds was calculated for each EEM as the sum of the fluorescence intensity of peaks C3 and C4 divided by the sum of fluorescence intensity of all peaks: (Fmax C3 + Fmax C4)/(Fmax C1 + Fmax C2 + Fmax C3 + Fmax C4) × 100.Samples for DOM fluorescence analyses were filtered through 0.2 μm MilliporeLive and Dead, respectively) and actively respiring cells (CTC+). LNA and HNA cells were differentiated according to relative nucleic acid content based on their green fluorescence signal after being stained with SybrGreen (Live) and membrane-compromised (Dead) cells were assessed by combining two nucleic acid stains, SybrGreen (Molecular Probes) and propidium iodide , yielding green and red fluorescence signals, respectively. PI can only penetrate into cells with large holes in their membranes. Live and Dead cells were analyzed in vivo as described in Live cells representing typically a subset of the HNA group. This group was analyzed in vivo after 90 min incubation in the dark with the compound. All samples were analyzed in a BD FACSCanto II flow cytometer.We followed the methodology described in more detail in ybrGreen . Samples–1 = 108.8 × [Bv]0.898 and then converted into μmol C L–1.The abundances of the five physiological groups were calculated after gravimetric calibration of the flow cytometer flow rates. Total bacterial abundances correspond to the sum of LNA and HNA cells described in the previous section. Filtration by GF/C filters resulted in an overall mean loss  of 26 ± 10% (SD) of the heterotrophic cells present in the Community treatment. From a seasonal perspective, retention was minimum in September (14 ± 9%) and maximum in February (32 ± 5%). Latex fluorescent beads of 1 μm diameter  were added to each sample as an internal standard. Side scatter  values relative to the fluorescent beads were converted into cell diameter following the empirical calibration of Live and CTC+ cells) were calculated as the slope of the natural logarithm of bacterial abundances vs. time during the corresponding exponential growth phases. Total heterotrophic bacterial growth rates correspond to the changes in abundance of total bacteria [LNA + HNA (reversed order for consistency)]. Viruses were unlikely to affect bacterial growth rates due to the short-time of the exponential growth periods  of four physiological groups , and ΔDOC/Δt is the carbon consumption (μmol C L–1 d–1) estimated from the decrease in total DOC.Bacterial growth efficiencies  were estimated by following changes in DOC concentrations (ΔDOC/Δt) and bacterial biomass (ΔBB/Δt), during the exponential growth phase, as shown in the following formula: BGE (%) = [(ΔBB/Δt)/(ΔDOC/Δt)] × 100, where ΔBB/Δt represents the increase of total bacterial biomass , frozen and extracted with the Power Soil DNAeasy kit (Qiagen). The regions V4-V5 of the 16S rRNA gene were amplified using the primers 515F-Y and 926R . Sequencpost hoc comparisons between levels were performed using R “psycho” package  software were used for statistical analyses. Repeated measurements analyses of variance (ANOVA), considering the month nested to station and  package . Two-way package  while di package .a concentrations were low to moderate (0.10–1.35 μg L–1), with the maximum observed at the Seagrass site in June and the lowest values systematically detected at the Phytoplankton site , but it made up to 74 and 87% inside the lagoon  in June.Warm temperatures were found year-round in the lagoon (Seagrass and Mangrove) and offshore water (Phytoplankton) sites, though showing a clear seasonality from 22.4°C in February to 33.3°C in September . Salinitton site . The con–1 there, with the Phytoplankton site consistently characterized by the lowest values . Overall, DOC concentration ranged between 77.2 and 137.3 μmol C L–1 . The concentration of DON .The minimum and maximum inorganic nutrient concentrations at the onset of the incubations were similar for both nitrate and phosphate, with minima in June at Seagrass and maxima in December at Mangrove . Contrarol C L–1  and it wp < 0.005, n = 30). A remarkable increase in the relative fluorescence of the C3 component was observed in December, reaching 62 and 74% at the Phytoplankton and Mangrove sites, respectively , while the Phytoplankton site never exceeded 4.5 × 105 cells mL–1. HNA cells dominated the community at all sites most of the time, except at the Phytoplankton site in February and December, when %HNA dropped to 47%. A clear seasonal pattern in %HNA emerged at the three sites, with minima in February and December and maxima close to 80% in September , exceeding on average by 4 and 10% the values of the Seagrass and Phytoplankton sites, respectively. Likewise total abundance, the Seagrass site also showed consistently higher abundance of Live cells (maximum of 5.14 × 105 cells mL–1), while the lowest abundances of membrane-intact cells were typically found at the Phytoplankton site (minimum of 1.91 × 105 cells mL–1). The contribution of Live cells (%Live) ranged from 84 to 98% (Live cells decreased significantly with increasing temperature only at the Seagrass site (5 cells mL–1 in September) with one order of magnitude lower minimum values found at the Phytoplankton site in December (1.50 × 104 cells mL–1). The contribution of CTC+ cells followed the same geographical pattern, ranging between 6.6 and 28.0%  ranged from 2.3 to 7.7 × 10eptember . %HNA ineptember . The Man4 to 98%  and no sass site . The abund 28.0% .5 cells mL–1 . The carrying capacity values were generally higher in the Filtered than in the Community treatment, although with some exceptions (Seagrass in June and December and Phytoplankton in September). The corresponding ratio of the Filtered to Community treatment carrying capacities (a surrogate for protistan grazers top–down control of heterotrophic bacterioplankton standing stocks) therefore ranged from 0.86 to 1.64, with the Phytoplankton site showing a different seasonal pattern to both lagoon sites  in the Filtered treatment without protistan grazers ranged one order of magnitude, from 3.23 to 10.8 × 10on sites , which son sites .t-test, p = 0.0013, n = 12) than the Community ones , similarly to carrying capacities. In the Community treatment we observed mostly positive net growth rates , except at the Seagrass site in February, where a decrease rather than an increase in abundance was recorded. In the Filtered treatment, specific growth rates ranged from 0.35 to 1.44 d–1 and differed seasonally . Although clear peaks were observed in June for the Mangrove and Phytoplankton sites, no significant correlations were found between specific growth rates and in situ temperatures either within individual sites or with all data pooled. Total specific growth rates showed, however, consistently negative relationships with the C:N ratio of DOM, which became significant at the Phytoplankton and Seagrass sites  in the Filtered treatments  showed consistently higher values  and maximum at the Phytoplankton site (1.05 d–1), both in June  and Mangrove (1.33 d–1) sites, respectively . Lack of sufficient CTC+ specific growth rate measurements precluded us from apprehending any general pattern besides the fact than values were generally low, never reaching 1 d–1  to 1.82 d in June . Similarectively . The speng 1 d–1 .–1 d–1 .Since production and consumption of DOC was concurrently occurring in the Community treatment, drawing any sound conclusion about its dynamics was precluded. On the contrary, with phytoplankton and protistan grazers excluded, DOC dynamics generally showed a decrease with time in the Filtered treatment , therefo–1 d–1 . Hereina–1 d–1) and maximum in June in the Mangrove site  and the Seagrass sites , but not at the Phytoplankton site. BGE was also significantly and negatively correlated with temperature at the Seagrass site  and with all data pooled .A small but variable part of the amount of DOC consumed by heterotrophic bacteria was used to build up their biomass. This increase in heterotrophic bacterial biomass was minimum in December at the Phytoplankton site  there  and at the Mangrove site , a relationship that held with all data pooled . Bacterial specific growth rate and BGE were both positively correlated to the production rate of C1 at the Seagrass site . BGE was also significantly and positively correlated to the consumption rate of C4  there. Consumption of inorganic nutrients was also observed in most incubations . At the Seagrass site no consumption of nitrate was observed. Changes in nitrite concentration were usually lower than for nitrate, except in February at the Seagrass site where a marked consumption was detected. Phosphate was consistently consumed at the Phytoplankton and Mangrove sites, peaking at −0.054 μmol L–1 d–1 in September (Mangrove). Phosphate consumption was only observed in September at the Seagrass site, with a maximum production of 0.075 μmol L–1 d–1 in December.The DOM fluorescent components C2 (humic-like) and C4 (protein [Tyrosine]-like) showed consistent consumption during the exponential phase of bacterial growth while C1 (humic-like) and less clearly C3 (protein [Tryptophan]-like) were mostly produced rather than taken up . Overallubations . The dynSynechococcus spp.) and Bacteroidetes (19%)  and different Proteobacterial groups, mainly in the Alphaproteobacteria class. The Seagrass and Mangrove sites had a higher percentage of the order Rhodospirilalles and Rhodobacteralles, while the Phytoplankton site had higher percentages of the SAR11 clade and Puniceispirillales (n = 12), nor was the Shannon index . The distribution of samples in a Principal Coordinates Analysis showed the existence of 2 clusters along the PCoA 1 axis . Overall, the most abundant phyla were Proteobacteria (49%), Cyanobacteria  . Althougrillales . OverallA 1 axis , one gatThe quality and quantity of DOM are considered the main factors limiting the growth of heterotrophic bacteria , with te5 cells mL–1 at the Seagrass site) were more similar to values previously reported across the Red Sea  was very similar to the annual averages of monthly samplings collected at KAUST Harbor (a (–1 only once at the Seagrass site. Although lower DOM (both DOC and DON) concentrations were consistently found at the Mangrove and Phytoplankton sites  has proven useful to understand the role of bacteria in marine food webs . In spitEven though individually it was only significant at the Seagrass site, a negative correlation was also found between BGE and temperature. This negative correlation is in agreement with the study by In conclusion, the location along the inshore-offshore gradient of a coastal Red Sea lagoon, aimed at covering the major microphyte and macrophyte sources of DOM in tropical shallow ecosystems, affected differently and coherently the specific growth rates of heterotrophic bacteria, while its effect on their maximum abundances was not that clear. In spite of high DOM concentrations, particularly in waters overlying seagrass meadows, bacterial specific growth rates were much lower than expected. This limited, seasonally invariant bacterial response suggests other nutrients may be limiting, reinforcing the hypothesis of bottom–up control of bacterial activity in shallow waters of the central Red Sea, but also the presence of possible antibacterial or antiprotistan compounds in seagrass meadows. Considering the three sites together, we have found additional evidence that DOM composition affects the specific growth rates and carbon conversion efficiencies of heterotrophic bacteria in shallow tropical waters more than bacterial community composition. In parallel, heterotrophic bacteria standing stocks, in particular at the Mangrove site year-round and the Phytoplankton site during the first half of the year , seemed The raw 16S rRNA gene amplicon data can be found in the European Nucleotide Archive, project number PRJEB49205. The rest of the data are included in the LS performed the experiments, analyzed the data, prepared The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Unwanted icing hasmajor safety and economic repercussions on humanactivities, affecting means of transportation, infrastructures, andconsumer goods. Compared to the common deicing methods in use today,intrinsically icephobic surfaces can decrease ice accumulation andformation without any active intervention from humans or machines.However, such systems often require complex fabrication methods andcan be costly, which limits their applicability. In this study, wereport the preparation and characterization of several slippery lubricant-infusedporous surfaces (SLIPSs) realized by impregnating with silicone oila candle soot layer deposited on double-sided adhesive tape. Despitethe use of common household items, these SLIPSs showed anti-icingperformance comparable to other systems described in the literature(ice adhesion < 20 kPa) and a good resistance to mechanical andenvironmental damages in laboratory conditions. The use of a flexibleand functional substrate as tape allowed these devices to be stretchablewithout suffering significant degradation and highlights how thesesystems can be easily prepared and applied anywhere needed. In addition,the possibility of deforming the substrate can “allow”the application of SLIPS technology in mechanical ice removal methodologies,drastically incrementing their performance. The most common commercialdeicing solutions consist of infrared or electrothermal melting,3 addition of low-freezing point agents,4 pneumatic actuation,5 and mechanical vibration,6 which requirea high energy demand and need to be engineered for specific applicationsrather than offering a broadband solution.Anti-icing surface technologies, which oppose ice formation andease its detachment, could have a huge impact on the global economy,affecting disparate aspects of our life such as transportation , energy production and distribution, infrastructuremaintenance and damage mitigation, and consumer goods.8 These “passive” methods solelyrely on the physical and chemical properties of the surface to obtainlow affinity to the forming ice, and thus, they can be highly cost-effective,environmentally friendly, and horizontally translated to many differentfields of application.9 Many differentapproaches were proposed during the years, each with their advantagesand drawbacks.9 For example, hydrophobicmaterials and coatings (including molecular monolayers), by loweringthe wettability of water, can promote passive ice slushing, althoughoften with limited performance.12In the past decades,however, research has instead focused on adifferent kind of anti-icing technology by devising intrinsicallyicephobic surfaces 1a.7,8 Th19 In addition, one can treat these surfaces in subsequent steps toincrease their performance further .20 However, such rough surfacesare fragile and prone to damage, and they favor heterogeneous icenucleation and increase the effective ice adhesion area once ice forms.21Nanostructured superhydrophobic surfaces (SHSs)can prevent iceformation by limiting the water contact time. Such properties arepurely morphological and thus can be obtained by etching, controlledgrowth, or lithographic approaches on a broad range of materials regardlessof their chemical nature.23 These consist of surfaces that are coveredwith a thin layer of lubricant, which lowers the surface energy andmakes it ultraflat. In this way, liquids can slip away at very lowtilt angles  and ice can detach with extremelylow forces.24 This observation is in agreementwith the equationW), the shear modulus of the substrate(G), and its thickness (h).7 In the case of LISs, with the substrate beinga liquid, G may be considered infinitesimally small,drastically reducing τ even for thin lubricant layers.An alternative solution could arise fromliquid-infused surfaces(LISs).Depending on where the lubricant reservoir is located, they canbe divided in two categories: alkane-infused gels (AIGs) and slipperyliquid-infused porous surfaces (SLIPSs).29 In these systems, the alkane wax, which could alsobe substituted with other compounds, such as (per)fluorinated liquids,29 to enhance the properties of the material, willtend to migrate toward the interface and form a thin icephobic layerthat can easily replenish itself when needed (in response to damageor lubricant leaching).30 AIGs are thereforevery robust systems also capable of achieving low ice adhesion forces.In addition, smart nanotechnological solutions can improve the performanceof these materials and the control on their properties even further.33The former consistsof soft polymer networks infused with longchain alkanes throughout their volume.34 They are commonly prepared from micro/nanostructured SHS by impregnationwith suitable high-boiling liquids that replace the air. The capillaryforces hold the lubricant in position, minimizing the flow and unwantedrelease. Moreover, the slippery properties can combine with othersurface behaviors like photothermal generation to increase the overallefficiency of the system.35Conversely, SLIPSs consist of highly porous nanostructuredmaterialswhere the lubricant fills the cavities and covers the surface, resultingin an interface very similar to that of AIGs.40 This versatility also translates in the possibility of preparingextremely low-cost designs, ideal for low-end applications.One advantageof SLIPSs over AIGs is that the former can be obtainedfrom a broad variety of nanostructured materials, such as polymers,carbon, metal oxides, metals, and even paper, and thus, they appearas a very versatile solution to achieve icephobicity in diverse applications.41 When deposited directly from the flame, it forms a complexnanostructured material characterized by a well-defined fractal structurethat renders the surface superomniphobic .43 Several groups already explored the anti-icingproperties of candle soot as an SHS,45 as a photothermal deicing platform,46 and as a host for fabrication of SLIPS,47 highlighting the stability of such systems, their simple fabricationprocedures, and their tolerance to damage. SLIPSs in particular aretolerant to several forms of damage because of their fractal structure,the mobility of the lubricant that can quickly fill vacancies, andthe interfacial forces between the lubricant and the soot that makesthe host matrix more tolerant to compression damage.48 Such characteristics suggest that by using a proper substrate, SLIPSsurfaces could deform and stretch to a certain degree without sufferingloss of performance, an incredible added value for the realizationof rapid and on-demand anti-ice fixings. However, to the best of ourknowledge, there are no examples of flexible SLIPSs in the literature,nor their possible advantages have been explored.A viable option in this sense is provided by candle soot, whichcan be obtained cheaply and reliably anywhere.In this study,we show how it is possible to realize a candle soot-basedSLIPS using stretchable double-sided tape as a support and siliconelubricant, thus resulting in a deformable icephobic coating that canbe applied on any structure on demand without altering its properties.Because of its simplicity, anyone can prepare such a system easilyand rapidly using common household items, thus making this approachincredibly useful for practical low-end applications. In addition,we investigate the effect of the addition of a fluorinated molecularmonolayer and the use of a halogenated lubricant on the overall anti-iceproperties and their stability under diverse types of stress. Finally,we show that the flexible nature of these SLIPSs, which in additionoffer an inherent low adhesion force, can produce the detachment ofthe ice employing extremely small strains and applied forces, underliningthe potential of this technology even for higher-end applications.22.1–1) and 1H,1H,2H,2H-perfluorooctyltriethoxysilane were purchasedfrom Merck. Halocarbon 6.3 oil  was kindly provided by Solvadis SpecialtiesGmbH (Germany).3M double-sided tape  and polyurethane-based double-sidedtape  were acquired on Amazon.it.Candles were obtained from a local hardware store in Pisa .Silicone oil , with 5 kV electronic beam acceleration at different magnifications.Optical profilometry was performed by a Leica DCM 3D Confocal Profilometerat 10× and 150× magnifications. The analysis of the opticalprofilometry images was performed using Gwyddion (v2.57). Water contactangle measurements were performed by means of an optical tensiometermodel Theta (Biolin Scientific). The droplets’ moving speedwas measured by analyzing video recordings (Adobe Premiere 2017) ofdroplets sliding on 5.5 cm-long flat SLIPSs with different inclinations.2.3A plasticEppendorf vial with a diameter of 1 cm and a height of3 cm was filled with water to the brim and placed upside down on thesamples. These were moved to a freezer at −21 °C, wherethe samples were left for at least 3 h. Shear force measurements wereperformed in the freezer directly or immediately after removal fromthe freezer using a dynamometer .2.4For eachtest, three samples were individually prepared and left for 10 min with a 40 g weight over them.2.4.5As-prepared SLIPSs werecovered with sand paper  with a 40 g weight over them. The sand paper was thenslit away with the weight still on.2.4.6As-prepared SLIPSswere covered with tape and left for 2 min with a 40 g weight overthem. The tape was then peeled.2.4.72) was applied on as-preparedSLIPSs for 1 min. The pressure was then released, and the sample wasrecollected.Employing a steel cylinder,100 kPa  beforebeing transferred to a rigid substrate to facilitate the measurement.2.5Figure S10a). The Young modulus of the 3M tape was set to 450 kPa, as definedby the supplier, while the ice properties were taken from the softwarematerials library. Both the 3M tape and the ice were modeled as homogeneous,linearly elastic materials. The right-end face of the tape was definedas a fixed constraint boundary, while the structure was pulled ata constant pressure, Ps, from the left side, as shownin Figure S10b. The displacement of thetape along the z axis was prevented by a roller constraintapplied to the bottom surface of the structure. A free tetrahedralnormal mesh was generated, and the number and size of the elementswere refined at the ice–tape interface. A stationary analysiswas performed using the default solver settings, and a parametricsweep was implemented to investigate the effect of varying Ps in the range of 10–100 kPa, with a step of 10kPa. A similar study was carried out with pressure applied at thebottom of the ice column, as reported in the Supporting Information.A 3D solidmechanics model was built in Comsol Multiphysics v5.6 to analyze theforce/strain necessary to detach the ice from the 3M tape. The geometryand material properties of the 3M tape and the ice column are reportedin the Supporting Information , characterized by a well-definedfractal structure of channels down to nanometric resolution. We reportan example of these surfaces in 46 The Minkowski–Bouligandfractal dimension associated with these surfaces was calculated tobe between 2.7 and 2.9 ,indicating its complex evolution in space.52 Such morphology is responsible for the observed superhydrophobicityof soot-covered substrates, which can trap air when immersed underwater, resulting in the mirror effect typical of the Cassie–Baxterregime .48 However, in the case of SLIPSs, it also aids in the dispersionand the retention of the lubricant by means of increased capillaryforces and a larger specific surface. In addition, the small channelslimit the flow of the lubricant, preventing dripping and reducingthe pressure damage .By exposing the tape to thetop part of the flame of a candle fora brief period of time (about 1 min), we obtained a black coatingof soot nanoparticles (diameter below 50 nm), which is about 12 μmthick S1, chara50 In our investigation, we decided to evaluate both a silicone oil(SO-SLIPS) and a commercially available fluorinated lubricant of similar viscosities in the fabrication of icephobic SLIPSs. Siliconeoil is commonly used in SLIPSs and AIGs as it readily forms slipperyflat surfaces and is immiscible with many liquids, while fluorinatedcompounds are known for their low surface energies and affinity towardboth organics and water.29Next to the host matrix, the choice of the liquid phase is alsoof paramount importance as it should not be readily miscible withwater and able to wet the porous surface.2 area: 202nm vs 437 nm of the Halo-SLIPS), pointing to the fact that the sootmatrix interacts better with the nonhalogenated lubricant. This lowroughness also correlates with the lower fractal dimension (of about2.1) calculated for SLIPSs when compared to as-deposited soot, indicatingan almost flat surface .In thecase of both liquids, it was possible to impregnate thesoot layer, obtaining smooth surfaces as shown in Figure S3. This observation also points to the fact that the advancingand receding contact angles are similar to their static value.53 One may use the values of θ to make considerationsabout the ice formation mechanism in the samples. For example, followingthe classical nucleation theory, one may describe the relation betweenthe free-energy barrier for heterogeneous and homogeneous nucleation using the equationr isthe nucleation germ radius, γiw is the surface energyat the water–ice interface, ΔvG is the volumetric free-energy variation that accompanies the iceformation, and f is a function that represents a geometrical correlation factorthat takes into account the effect of external bodies in facilitatingthe nucleation  at the waterinterface.55 The parameter m in the latter is related to the interfacial energies between theliquid water, ice, and the substrate, and it is proportional to cos(θ). R is a parameter that depends on the ratio between the sizeof the heterogeneous nucleation sites and the critical nucleationradius: for a flat substrate, as it is the case of SLIPS, R tends toward infinity and f can be considered a function of only θWe measured the water contact angles (θ) to be of about 106± 1° for all the SLIPS samples , similar to that of bare 3M and much lower than thatof as-deposited soot 2i. A minf approaches unity (homogeneous nucleationlimit), and the homogeneous and heterogeneous nucleation paths becomeenergetically equally probable. In the specific case presented here, f ≈ 0.7 forthe SO-SLIPS on 3M, thus showing that homogeneous nucleation is notenergetically prohibited.47 This valuefor the SLIPS is taken from experimental values of θ and, assuch, includes the presence of intrinsic defects on the surface .Figure S6), which are evidence of theworse wetting between the fluorinated host matrix and silicone oil. The SEM analysis, however, showed that the morphologyat the micrometer scale is not much different than that of the SO-SLIPS.The passivation with the silane also seemed to reduce the water contactangle in the case when halocarbon is used as the lubricant (G*heter ≈ 0.4 ΔG*homo).As anticipated, with the functionalization, the F-Halo-SLIPSresultedin a lower local roughness (342 nm). Conversely, the F-SO-SLIPS presentedan increased amount of corrugation and an increased number of defectsS6, which3.2As introduced previously, SLIPSand AIG interfaces are covered witha thin layer of lubricant that increases the smoothness and preventsice adhesion by reducing nucleation sites. This affects both frostformation and the shear force necessary to remove the ice.7 Such a methodis often used in the literature to compare the performance of icephobicsurfaces. The results we obtained are summarized in 30 Remarkably, the SLIPSsurfaces investigated in this study met this requirement despite beingfabricated from everyday household items such as double-sided tape,a candle, and lubricating oil. Notably, most times when removing theice column, we observed minimal soot transfer, indicating the stabilityunder these conditions . Thesilanization of the soot or change of the substrate to a differentkind of double-sided tape  did not affectsignificantly the icephobic properties of the SO-SLIPS system.Weevaluated the ice adhesion performance of all the surfaces discussedso far by measuring the shear force necessary to remove a column ofice with a diameter of 1 cm.Sab, which defines the tendencyof phase a to penetrate phase b, and it is expressed by the relationa andγb represent the surface energies of phases a andb, respectively, and γab is the interfacial energybetween them.58Sab < 0 indicates that the two phases do not penetrate eachother .59 Following the approach of Preston et al.,50 we could estimate the values of S for the different water–lubricant couples as+, and – superscripts represent the dispersionforces and polar (considered as Lewis acid–base interactions)contributions, respectively. For silicone oil–water, γlLW and γwLW of 20.1and 21.8 mN/m,50 respectively, for whichone can safely assume no polar contributions,50 we found Slw to be about +1.6 mN/m,indicating that a slight cloaking of the water droplets by the lubricantmay happen.23 This could also be the reasonwhy the tape–soot SLIPSs presented herein have slightly worseperformance than other similar soot-based ones (which have been shownto reach adhesion forces of about 2 kPa).47 Conversely, when halocarbon oil is considered, despite the higherγl (23 mN/m), the polar interactions between thelubricant and water  resultedin less performing surfaces, a reflection of the high number of defectsreported in the previous section, which offers a higher chance ofheterogeneous nucleation. Different from the SO case, for the halocarbon–sootsystem, the modification with the fluorinated alkylsilane sensiblyreduces the ice adhesion strength. However, such improvement is notsufficient to meet the 20 kPa target. The lower performance of halocarbonas the lubricant may be ascribed to the lower surface energy associatedwith fluorinated materials. While the latter is responsible for theinertness that makes such materials appealing, it also reduces theextent of interaction with the host matrix, allowing an easier displacementof the lubricant by the water. This can be rationalized with the spreadingparameter, 3.3For their plannedapplication, anti-icing surfaces are subjected to strong environmentalconditions, which may compromise their function. To address this issue,we performed several stability tests of our SLIPS, monitoring thechange in ice adhesion strength, and the results are summarized in Retentionof the lubricant is a major issue as, in the case of most SLIPSs,surface interactions are the only forces that prevent leaking. Candlesoot revealed to be a well-performing substrate for silicone oils,and even absorption tests performed using adsorbent paper resultedin a relatively small loss in performance, which could as well beattributed to mechanical damage.48 and even show self-healing properties.60 Mostly, they result from the tendency of the lubricant to migratefrom the reservoir to the surface to minimize its surface tension.27 We performed cut and abrasion tests as describedin Figure S8. While this mechanism canrepair small damages, it does not prevent the degradation of the sootmatrix. One can directly observe this from the lower and nonconstantsliding velocity of water droplets on the damaged surfaces , indicating a nonuniform surface.Indeed, direct mechanical solicitationscan damage the host structure,affecting the retention of the lubricant and smoothness of the surface.However, the mobile nature of the liquid phase and its affinity tothe soot matrix, together with the fractal structure of the latter,can adapt remarkably well to minor damagesFigure S4). In particular, such pressure wassufficient to compress and remove the soot layer alone; however, inthe case of a SLIPS, the damage was found to be much more contained.Application of high pressure (100 kPa) was found to not affectsignificantly the ice adhesion characteristics of the surfaces (20.2± 0.4 kPa). The presence of the lubricant in the soot matrix(rather than air) effectively makes it more tough and resilient, asit usually happens in composite materials, and thus better able towithstand pressure damage. Indeed, images comparing the depositedsoot and SLIPS surfaces after the application of a vertical forceshow the differences in the mechanical strength of these layers . Profilometryimages show that after the removal of tape, the surface appeared slightlysmoother (mean square roughness of 189 nm vs 202 nm of the SO-SLIPSas prepared), as if the adhesive tape could efficiently remove thesoot defects protruding from the lubricant. The anti-ice performanceof the SO-SLIPS was not affected by the peeling (even after multiplecycles). Thus, in principle, one may use adhesive tape to protectand store the tape–soot SLIPS between preparation and application.We also investigated the effects of adhesive tape on the SLIPSsurface since such a test is able to remove soot efficiently fromdifferent surfaces .Because of the interface dynamics discussed in the previous section,we studied the stability of the SO-SLIPS under water and ice for prolongedperiods of time. After being left for 2 weeks under water or solidice, the performance of the tape–soot SLIPSs resembled thatof the aforementioned mechanically damaged ones. In particular, treatmentwith water for prolonged periods seemed to affect the SLIPS propertiesthe most. We ascribed this evidence to the low value of Consecutive icing–deicing cyclesmay also affect the long-termstability by slowly removing the lubricant and damaging the soot structure.We therefore exposed the SO-SLIPS to sequential freezing cycles, continuouslymonitoring their performance. Notably, after 15 cycles, the ice adhesionstrength was still below 30 kPa, a value similar to those measuredfor the other types of damages but that still allows ice detachmentwith minimal effort. A closer look on the surface showed that theprotruding defects did not increase in height but rather became larger,as if they were slowly merging together over cycles 3e.47 However, in real applications, the propertiesand the stability of SLIPSs (including the ones presented herein)could differ as the mechanical stability of the soot matrix is limitedwhen compared to other anti-icing technologies (see Table S1).This performanceis comparable to what has been observed in similarsystems tested in laboratory conditions.Nonetheless, it is worth mentioning thatin the case of damagethat compromises the icephobic function of the coating, the cheapand rapid fabrication procedure allows for its swift substitution.Such an approach is not possible  in the case of SLIPSs or other icephobic surfaces with morecomplex fabrication methodologies, despite the fact that it mightshow better performance during the tests.3.4Figure S9) did not affect theice adhesion characteristics of the SO-SLIPS significantly. Opticalprofilometry data and SEM imaging support this finding, underliningthe limited effects of stretching on the surface morphology . This feature allows anyone to preparethe tape–soot SLIPS easily and apply on demand when and wheredeemed necessary, which is no different than the application of regulardouble-sided tape.One distinctive featureof the SLIPSs that use tape as a substrate is their intrinsic stretchability.Both the tape and the fractal micro/nanostructure of the soot caneasily sustain stretching and bending, and the addition of a lubricantis not expected to change this behavior. Remarkably, stretch cyclesup to 30% . The stress was maximized at theinterface between the two materials in the direction of applicationof the load. As reported in Figure S10),resulted in a von Mises stress of 77 kPa at the ice–tape interface. We triedto validate these findings experimentally; however, the strain valueswere too small to be measured as the ice columns would detach as westarted the drawing of the SLIPS. This observation, however, supportsthe results of the numerical calculations and shows the potentialof stretchable SLIPS to make practical ice removal technologies comparedto rigid surfaces.These observations pointto the fact that in the case of longitudinalstretch, a very small strain (less than 1%) is already enough to generatea force sufficient to detach the ice, making stretching a viable solutionfor ice detachment. Besides the longitudinal strain, we also investigatedother types of deformations, finding that they were equally efficientif not better performing as in the case of a force applied from belowthe surface .Finally, webelieve that the SLIPSs here presented offer a simpleand effective solution for an anti-icing system that can be appliedwhen and where needed with the simplicity of applying scotch tapewhile, at the same time, offering good performance.


SecSel, a protected-area prioritization tool, has been developed to help design areas that efficiently protect multiple features, including conservation of biodiversity and use of ecosystem services. The prioritization by SecSel is based on evaluation of the local units of each feature. The evaluation metrics should be quantitative but need not be ratio scale. The minimum requirement of the input data is that they are ordinal. The conservation target is the number of local units with high values of each feature to be protected in the area. SecSel can handle conflicts among features, including conflicts between conservation and utilization of land or specific ecosystem functions. Before the selection procedure, one of a conflicting pair of features in a site is discarded. That decision is based on the dispensability of the local unit to fulfilling the conservation target of each feature. SecSel also considers the cost of including each site in the protected area and the compactness of the area in terms of total boundary length or the distance to the nearest site. To demonstrate the functionality of Secsel, we used it to design land use in an alpine region of northern Japan where conservation of alpine vegetation and its recreational use are important considerations. Prioritization of conservation areas is one of the major conundrums in conservation ecology –3. VarioAppropriate design tools are chosen on the basis of available data and the purposes of the prioritization analysis. When detailed data are available, the protected area can be designed based on a quantitative evaluation of conservation effects. With less informative data, the evaluation of conservation effects is inevitably less quantitative. Binary presence-absence data for organisms, for example, do not include the quality of local populations. Inclusion of any local population is considered to contribute equally to the conservation of target species.Both of the widely used conservation prioritization tools, Marxan  and ZonaQuantitative data such as area covered by vegetation to conserve, population size, population density, and biomass meet this requirement. Binary data such as presence-absence, which provide limited information, also can be handled as ratio-type data and fed to Marxan and Zonation.It is often the case that non-ratio type data that provide more information than presence-absence data are available. A typical example is a rough evaluation of population size or quality . For exSecSel is a newly developed prioritization tool designed to handle rank-type data for prioritization analyses. SecSel selects areas for conservation that include local units that are highly ranked on the basis of multiple biodiversity features. Ecosystem functions and other purposes of land use may also be included in the analysis. In SecSel, a set of several local units with low ranks for a biodiversity feature is not a substitute for a single unit with a high rank. This limitation causes some inflexibility in site selection, but flexibility remains as long as there are ties between local units. Such ties occur in many cases when biodiversity features are roughly estimated.In many cases of conservation planning, conflicts between protection and other land use are inevitable. There are several approaches to finding compromises when such conflicts arise. For example, Chan et al. (2011)  have comIn SecSel, ecosystem functions are also features to be considered. It is sometimes the case that use of land to exploit ecosystem functions conflicts with conservation of some of the biodiversity features. In addition, other conflicts may occur between biodiversity features. For example, there may be pairs of biodiversity features for which conservation of one has a negative impact on the other. Examples include species of woodland animals and grassland animals, or aquatic species in eutrophic habitats and those in oligotrophic habitats.There are several approaches to resolving such conflicts. One approach is allocating an area for commercial land use beforehand and subsequently selecting an area for conservation from the remaining land. Such an approach is simple, but it may lead to deterioration of areas that are irreplaceable for the conservation of some features of biodiversity. Chan et al. (2011)  have useConflict.Before site selection, SecSel searches for conflicts between local units with incompatible features within sites. For every conflict, which of the incompatible local units has higher priority is determined. Features with lower priority are ignored in the subsequent selection procedure. The priority is greater when the local unit in the site has a relatively high rank. Details are described in section This paper provides an introduction to the basic purpose and rationale for SecSel. As an example of its application, we applied SecSel to the design of land use in an alpine region of northern Japan where consideration was given to conservation of several biodiversity features and their recreational use.http://www.nies.go.jp/biology/en/data/tool/secsel/index.html). Its function is controlled by a setting file, which is a text file that describes data file names and parameter settings. In the next sections, we define the basic terms used by SecSel, explain the required input data, outline the selection process, and describe the output data. A graphical summary of these workflow is provided in SecSel is coded in Python 3. It is open source and is available from the website  and the ranks of other local units are 3, 2 or 1, then the set is said to be top-3 included. This criterion is introduced to define the conservation/utilization target as described in the next section.If N for a given feature, the top-N of the units of the feature should be included. Based on this concept, the local units of the feature should be top-N included in the protected area. If the ranks are highly resolved and no local units have the same rank, the set with the minimum number of sites that fulfill the top-N included criterion of a feature is unique. If the resolution of the ranks is relatively low and ties are frequent, the selection of sites will be more flexible. This flexibility makes it possible to identify a compact set of sites that fulfills all the targets for multiple features.In SecSel, the targets for individual features are equated to the number of highly ranked units in a protected area. If the target is Resolution of conflicts.In SecSel, a conflict may occur in a pair of local units of features within a site. Local units of conflicting features are not conserved or used simultaneously within a site. Conflicts between incompatible features within sites are resolved before site selection. The local unit that is more critical for achieving the target of the feature has higher priority in resolving the conflict. A local unit of a feature is given lower priority than more critical units of other features. Because an explicit decision is made about which feature is given priority at a site, it is clear which features within a selected site are to be protected/used in the implementation of conservation design. The details of the decision process are described in section For each feature to be considered, data of evaluation for individual local units are necessary. Furthermore, there should be targets for individual features.Evaluation of local units within each site should be prepared for each feature. For the features to be protected, the evaluation is based on the conservation value. For the features to be used , the evaluation is based on the quality and/or quantity of the benefit the site would provide.The evaluation is quantified on an ordinal, interval or ratio scale. Binary data consist of 1 for presence and 0 for absence; three levels may be high, low, and no value; or there may be continuous values that describe the area of concern in an ecosystem or the size of a population. All these metrics meet the requirement of SecSel. There is no limitation on the resolution of the evaluation. On the one hand, the higher the resolution, the more precise the selection of the highest priority local units will be obtained. On the other hand, low resolution enables more flexible selection of local units. Flexibility makes it possible to select a compact set of sites to achieve targets for multiple features. Flexibility also facilitates selection of multiple protected areas that achieve almost the same conservation efficiencies.i is Ni, the target is achieved when the local units of this feature in the selected sites satisfy the top-Ni included criterion. It should be noted that collection of local units of low value is not a substitute for a highly prioritized local unit. Targets may or may not be the same among features. A target can be assigned to each feature independently.For every feature, the number of top local units to be included among the selected sites is specified as a target. For biodiversity features, the target is a conservation requirement. For features to be used, the targets are utilization requirements. If the target of feature In addition to the above-mentioned compulsory input data, SecSel can consider pre-reserved sites, conflicts among features, cost of conservation, and compactness of conservation area in the site-selection process.Sites that should be included in the protected area can be specified as pre-reserved sites. When the current protected area is to be expanded, sites included in the present protected area are specified as pre-reserved sites. SecSel decides which sites should be added to these pre-reserved sites.Resolution of conflicts describes the algorithm of the decision.As described above, conflicting features are those that cannot be conserved/used simultaneously in a site. To consider conflicts and avoid incompatibilities, data about conflicting pairs of features should be provided. SecSel decides which feature has higher priority and which has lower priority at each site where there is a conflict among local units of two or more features. Section Cost considerations explains the details of the cost consideration process.Secsel can consider the cost of including individual sites in the protected area. For example, the cost can be the amount of money paid to obtain the land and/or to perform conservation management in the site. Given cost data for individual sites, SecSel tries to find a set of sites with the lower cost. Like the data of the conservation/utilization values of local units of features, the cost data are on an ordinal scale with no specified degree of resolution. The cost data are used to determine which of the candidate sites of similar conservation efficiency should be selected. Subsection The cost of a site may depend on which feature is to be conserved/used in the site. SecSel does not handle such multiple cost criteria. If a special cost should be paid for a feature, the evaluation of the local units of the feature may be decided on the basis of the cost of conservation/utilization of the feature within each site.The length of the boundary shared by two sites can be used to select the set of sites that is less scattered. Like cost data, the length of the boundary is used to determine which of the candidate sites of similar conservation efficiency should be selected. There is no guarantee that the selected set of sites has the smallest perimeter.In the first step of the selection process, sites are selected to satisfy the top-1 included criterion for all features. Once that criterion is satisfied, sites are added to fulfill the top-2 included criterion for all features for which the target is 2 or larger. This process is continued by incrementing the number of top local units to be included. The process is terminated when the targets are fulfilled for all features of interest.N included criterion (N being incremented during the selection procedure) is calculated. The site with the maximum number of features that newly fulfill the top-N included criterion is the site to be added to the sites that have already been selected. If there are ties, one site is selected randomly.For each step of selecting a site to add, a greedy algorithm is employed. For each unselected site, the number of features that would fulfill the top-N included criterion. To place more emphasis on reducing cost in the selection process, candidate sites may include sites that are not necessarily among the sites that most effectively increase the number of features that fulfill the top-N included criteria. The number of candidate sites, including the less efficient but less costly sites, reflects the emphasis on cost reduction. The larger the number of candidate sites, the greater the odds that a less efficient site may be selected because of its small cost. This process may increase the number of sites required to achieve the targets of all features. The final set of sites is not necessarily the set of sites that minimizes the total cost irrespective of the number of candidate sites. This result is an inevitable consequence of a heuristic algorithm.When cost is to be considered, it is used to break ties between sites in the number of features that newly fulfill the top-A less-scattered set of sites can be selected in SecSel. SecSel implements two methods for this purpose.N included criterion, the site that causes the smallest increment to the total boundary length is selected.One of the methods considers boundary length. During the process of site selection, the total boundary length of the set of selected sites changes. It typically, but not necessarily, increases. The change in length by addition of a site depends on the geometrical relationship of the additional and already-selected sites. Addition of a site that shared a boundary with already-selected sites would increase the total boundary length less than addition of an isolated site. Thus, by considering the change of the total boundary length, sites adjacent to already selected sites are more likely to be selected. To break ties in the selection of sites based on the number of features newly fulfilled in the top-The other method considers the distance of a site to the nearest site among the other selected sites In this method, the distance to the nearest selected site is used to break ties in the same way that the boundary length method is used in the site-selection process. The site that lies the shortest distance from the selected site is chosen. The merit of this method is that it is applicable in a case when the sites naturally do not share a common boundary . This method helps to avoid selecting isolated sites that are distant from already-selected sites, and it is expected to reduce the maximum of “the distance to the nearest sites” within the conservation area.N inclusion requirement are not likely to be adjacent to each other as long as there is spatial autocorrelation in the distribution of each feature. Neighboring sites are likely to have more similar compositions than randomly selected sites, and they are less likely to complement each other. Scattering is therefore not likely to determine which of the tied sites should be selected. If there are differences in costs among sites, those differences could decide which site is selected. As more and more sites are selected, it becomes increasingly likely that candidate sites will share a boundary with or close to already-selected sites. The protected area thus expands by adding adjacent sites to low-cost, previously selected sites. If there is spatial autocorrelation of costs, the costs of the sites added to the low-cost sites are also expected to be low. The protected area is therefore likely to start from one or a few core areas in a low-cost region; adjacent sites are then added to expand the core areas. The final result is a less-scattered set of selected sites in low-cost regions.In the consideration of both the cost and scattering of sites, scattering is the first criterion used to break ties at each step of site selection. If there are still ties after consideration of scattering, then cost is considered. In the early stages of the site-selection processes, sites that are highly efficient with respect to fulfilling the top-Consideration of costs and scattering may lead to a protected area with a relatively large number of sites after the heuristic selection process. The number of sites varies between cases. If there are relatively large numbers of highly ranked local units with numerous features, there is more flexibility in site selection to achieve targets, and consideration of costs and scattering would have less of an effect on the final size of the protected area.S, is defined as follows:N is the target of the feature, and b is the position of the local unit within all local units of a feature in the descending order of value. If there is more than one local unit with the same rank, b is calculated as follows:k is the number of local units of the feature with higher ranks, and m is the number of local units with the same rank as the unit in the focal site. For example, if the top four local units have the same rank, all units are assigned b equal to the mean of 1–4, i.e., 2.5. If there are five rather than four tied local units, b is 3.0. A larger b results in a larger dispensability index, S. When more local units are available as substitutes for the one in the focal site, the local unit becomes more dispensable.When there are conflicting features within a site, Secsel determines which one of the conflicting features is to be ignored prior to site selection. To determine which feature is to be ignored, the dispensabilities of the local units of the individual feature toward achieving the target are compared. To enable this comparison, a dispensability index, S varies inversely with the target, N. The implication of a larger N is that the local unit in the focal site is less dispensable. Even when the b is the same among features, the one with the larger N requires more local units with high ranks, and the local unit in the focal site is thus less dispensable.The value of S values of conflicting local units within a focal site have been calculated, the local unit with the larger S is ignored. Because the omission of a local unit affects the S values of other units of the feature, the S values of remaining units are recalculated. The fewer local units that remain, the less dispensable will be the remaining local units.After the The output of SecSel is a set of selected sites listed in the order of selection. Additional information includes the features by which each site contributed to the achievement of targets. When conflicts among features are taken into account, the information used to ignore some features is provided. This information is crucial to deciding conservation/utilization practices within selected sites when there are local units of conflicting features.In addition, SecSel outputs the frequency with which each site is included in the selected area in multiple runs. There are some stochastic processes in the SecSel site selection. First, ties can occur when deciding which site contributes most to achieving targets. One of the sites that is tied is chosen randomly. Such ties occur frequently, especially when there is a low resolution of the local unit evaluation. It should be noted that low resolution leads to flexibility with respect to site selection, and it widens the range of variation of site selection in the process of tie breaking. There is another stochastic process in the resolution of conflict. When there is a tie in the dispensability index among local units with conflicting features, one of the units is randomly given priority. Ties can also occur in site selection during consideration of cost and scattering.A result of these stochastic processes is that site selection can vary between replicated runs of SecSel. The range of variation depends on the nature of the given data. The greater the probability of ties, the more likely that the variation of selected sites is large.SecSel automatically repeats the user-specified number of runs. The frequency with which each site is included in the selected area in multiple runs may be an indicator of the irreplaceability of the site. However, a combination of sites that are frequently selected does not necessarily result in protected areas that efficiently fulfill targets. This is because the sites in the set chosen in a single run complement each other to achieve the goal, and there is no guarantee that the goal will be achieved if the set is broken apart. Such properties are common to complementarity-based prioritization, and selection frequency results should be interpreted with caution in this regard.The Taisetsu Mountains in northern Japan are the site of the largest national park in the country . Many alNational parks in Japan are expected to play roles not only in biodiversity conservation but also in the provision of ecosystem services. Fields of alpine flowers attract visitors and are one of the most important resources for tourism.2. We then categorized the habitat quality of each grid cell for each vegetation type into four rank classes based on the area of the vegetation type within the cell , sites in the northern and southern parts of the Taisetsu Mountains were often selected as a whole, and sites in the central part were selected somewhat less frequently . In partThis pattern of selection likely resulted from the fact that there were many cells where shrubs grew, but the distribution of snow meadow, fellfield, and wilderness was more limited . AlthougWhen consideration was given to cost (cost-on in SecSel), the cost function worked as expected, and the selected sites concentrated close to the trail entrances . When thWhen consideration was given to the nearest-distance penalty (distance-on), there was an increase in the frequency with which sites in the central part of the Taisetsu Mountains were selected , in contExamination of the site-selection pattern for each run revealed that a small number of sites in the central part were consistently selected on all the example runs when the SecSel settings were cost-off, boundary-off, and distance-off  were selected for shrubs. The small flexibility for other types of vegetation was due to the flexibility in the process of resolving conflict between tourism and conservation. When there are conflicts with other conservation objectives, the priority of objectives may change at each iteration. The use of ranks as a measure of site quality increases the flexibility of prioritization by ignoring small differences in areas.In a review of conservation planning tools, Sarkar et al. (2006)  have proSecSel tries to find a minimum set of sites that meet the given multiple targets. If the cost of including each site is given, suppression of the total cost is considered. The algorithm used by SecSel is a greedy algorithm, which is heuristic and does not necessarily find the global minimum solution. However, the difference between the solutions of the greedy algorithm and the global minimum was not large in most cases . BecauseThe greedy algorithm allows SecSel to find a solution rapidly. For example, selection from 3000 sites to satisfy the top-3 of 150 features is repeated 100 within 10 seconds on a desktop PC. In the case of the Daisetsuzan National Park, it took no more than a few seconds for 100 iterations. The short time required for SecSel to find a solution allows SecSel to be used on-site for discussions in real time.The data used to evaluate features to be conserved/used need to be on an ordinal scale, but not necessarily on an interval or ratio scale. SecSel can handle semiquantitative data such as expert judgements. The resolution for the ordinal scale can be set arbitrarily. Furthermore, cost data do not need to be on an interval or ratio scale. The small constraints imposed by the data requirements provide high flexibility that is a distinct advantage of SecSel. In the example of Daisetsuzan National Park, we showed that SecSel could easily treat the course-time from the nearest trail entrance. That metric has qualitatively different units than the vegetation area metric.The logic for site selection in SecSel is straightforward. In every step, it is clear why the newly added site is selected: it makes the largest contribution to the achievement of targets. It is clear which of the features within the site contribute to the achievement of targets. This transparency is an advantage of the heuristic step-by-step approach. Furthermore, the transparency is also apparent in the process of resolving conflicts of features within a site. The logic of the resolution of conflicts is simple: local units that are more dispensable to the achievement of the feature are given lower priority. It is apparent from SecSel is not designed to solve specific problems. Any type of feature can be handled, as long as the conservation value of the local units of a feature is evaluated on at least an ordinal scale. SecSel assumes that the focal area consists of multiple ‘sites’. The sites are not necessarily of the same size, nor are they arranged in grids. A set of isolated ‘sites’ such as fragments of ecosystems is acceptable.The conflict resolution part, cost calculation part, and compactness evaluation part are implemented as separate class objects. These parts can be substituted by user-defined python objects. All input and output data are in the form of a simple text file. Data can be passed to and from other systems easily.a priori involvement before the use of the tool, interactive involvement during the use of the tool, and a posteriori involvement after the use of the tool [a priori involvement), the repetition of calculations while settings are manipulated (interactive involvement), and interpretation of the results of calculations (a posteriori involvement). In the following sections, we describe in more detail how stakeholders can be involved in each stage.Conservation planning tools are not expected to provide a final solution to be handed to practitioners for implementation. Rather, the tools are expected to be used repeatedly because they reflect stakeholders’ interests, values, and opinions. In the process of using conservation-planning tools, stakeholders can be involved in three stages; the tool . With Sea priori stakeholder involvement. For conservation of biodiversity features, options are numerus. The feature may be ecosystem types or some taxa. For the conservation of taxa, a decision should be made about which taxonomic group and taxonomic level is to be considered. Furthermore, the feature may be the target of conservation by itself, or a surrogate of something else that is the real conservation target. Stakeholders should be involved in selecting features to be handled with conservation tools.Selection of features to be conserved/used is the first step of The criteria for evaluating the features is another point to be considered before the collection of data. Acquiring detailed and/or quantitative data involves cost and effort. The trade-off of the cost and the quality of data should be considered, and an appropriate balance should be found among stakeholders.Stakeholders should reach an agreement about the appropriate conservation/utilization target for individual features. However, the target may be manipulated interactively, as described later in this section.If some of the sites of the focal area are designated as protected areas beforehand, SecSel starts site selection with those sites and then adds more. It is up to stakeholders to decide with which sites to start. They may be currently protected areas, or areas of special interest for reasons such as historical, social, or scientific value. Stakeholders are expected to provide a wide range of viewpoints.The high computational efficiency of SecSel is due to the heuristic algorithm that supports interactive stakeholder involvement. Stakeholders can try various settings and compare results. Settings to be changed include targets for individual features, conflicts to be considered, cost considerations, pre-reservation of sites, and so on. If the given target is too demanding, a compromise between costs and targets may be explored by manipulating targets. In this process, the consequences of lowering targets should be carefully considered, especially if the lowered target is suspected to be insufficient for sustainable conservation of biodiversity features.Resolution of the evaluation of local units can also be manipulated to control flexibility and get acceptable solutions. Higher-resolution data with more rank levels lead to a narrower range of variation of sets of sites to achieve targets. This is both an advantage and disadvantage. With higher resolution, full advantage can be taken of detailed data. However, a narrower range of variation of the selection leads to smaller flexibility. Reduction of resolution leads to more ties in the calculation process and can lead to larger variation of the results. An appropriate level of resolution may be found through repeated trials.Whether or not to incorporate costs and boundary length can be tested in repeated trials with SecSel. These factors may be considered or ignored. The results with or without their consideration will be compared during the interactive involvement process.a posteriori stakeholder involvement.A posteriori stakeholder involvement is the process that occurs after the tool proposes a protected area. Because of the stochasticity in the selection process, SecSel provides multiple sets of sites as land use alternatives. Stakeholders can compare them to find an acceptable solution. Stakeholders can assess the validity of the design from various points of views, which are not explicitly incorporated into the site selection by prioritization tools. The processes of selection by SecSel are straightforward. There is a clear reason for the addition of each site: its contribution to the achievement of targets. This clarity is an advantage in the a posteriori involvement can be fused.The high calculation efficiency of SecSel allows repeated trials of site selection, so that stakeholders can easily go back to the interactive involvement phase if needed. Interactive and Sharing and sparing are alternative approaches to the compromise of conservation and land utilization , 20. ShaSome prioritization tools resolve conflicts among features in different ways. In Zonation, sites suitable for purposes other than conservation are given negative values so that such sites will likely be omitted from protected areas. Marxan with zones , a derivThe appropriate balance between features that conserve biodiversity and the benefit obtained from land use depends critically on stakeholders’ interests and values. This dependence is also critical to the resolution of conflicts between features of biodiversity. SecSel does not provide a decision about which feature has higher priority globally. It compares the relative priorities of local units for the achievement of targets of individual features. There is no need to compare different features with a common currency. It is advantageous for stakeholders to reach agreement among themselves.S1 Fig(TIF)Click here for additional data file.