Ecological similarities and differences among littoral species of Ceriodaphnia
The occurrence of six littoral species of Ceriodaphnia (C. affinis, C. laticaudata, C. megops,C. reticulata, C. rotunda and C. setosa)living at the same time and locality is described.Basic population characteristics were studied in allspecies coexisting in the field, except for C. setosa, which was too scarce. Abundances,proportions of gamogenetic individuals, mean bodylengths and clutch sizes were compared among species.Dissolved oxygen, temperature, chlorophyll-a and totalseston volume were measured and related to populationchanges. C. laticaudata and C. rotundawere closely similar to each other in many featuresand showed significant differences to other species.C. reticulata and C. megops seem to besimilar in some features, while C. affinis wasecologically different.
Chitinous aquatic invertebrate assemblages in Quaternary lake sediments as indicators of past deepwater oxygen concentration
Abstract Chitinous aquatic invertebrate remains are abundant in late Quaternary lake sediment sequences. However, for standard analysis of invertebrate indicator groups usually only the remains of one particular invertebrate group (e.g. water fleas, midges) are systematically isolated from the sediments and analysed numerically. In a calibration study focusing on surface sediment samples from 36 small Swiss lakes, we show that the abundances of other chitinous aquatic invertebrate remains in samples prepared for chironomid analysis provide important information on in-lake oxygen conditions when assessed relative to and together with the overall number of chironomid remains. Our results show that particularly high abundances of chironomid and chaoborid remains are indicative for lakes with high and low deepwater oxygen concentrations, respectively, but that also the remains of other invertebrate groups such as Ceriodaphnia ephippia and Plumatella statoblasts tend to be more abundant in warm, stably stratified and anoxic lakes. Direct gradient analyses of the isolated invertebrate assemblages indicate that deepwater oxygen concentration during late summer is the strongest predictor for assemblage changes in our dataset, followed by variables representing temperature conditions (summer surface water temperature, altitude), summer stratification stability (temperature difference between surface and deepwater layers), water depth and the relative volume of the late summer hypoxic water layer. We show, based on invertebrate assemblages in a Lateglacial sediment sequence from Rotsee, Switzerland, that our new calibration data can provide information on past changes in deepwater oxygen availability from late Quaternary lake sediment sequences, when fossil invertebrate assemblages are added as passive samples to ordinations of the surface sediment calibration data. This provides a new approach for developing assessments of past changes in deepwater oxygen concentrations from late Quaternary sediment samples prepared for chironomid analysis. Such assessments can provide important supplementary information for e.g. interpreting palaeotemperature reconstructions based on chironomid remains.
Soil organic matter and microbiological development of technosols in the South Wales Coalfield
Abstract Degraded land (formerly ‘reclaimed’) after surface-coal-mining is a serious problem in South Wales. This project uses forestation to foster soil development on opencast coal-mine spoil technosols. It compares records of humification and the soil microbiological system (microcoenosis) using paired data from the same plantings in 1998 and 2018. Statistical analysis finds no significant difference between samples collected under trees planted by the pit-planting versus trench planting method or trees planted using organic or mineral fertilizer. However, there are strong significant differences in both soil organic matter and microflora components and significant correlations with time since tree planting. Most components of the soil organic carbon (TOC) and the microflora increase, often significantly. However, compared to 2018, 1998 samples contain significantly greater maximum levels of Insoluble Carbon while the microflora had significantly more Ammonifying bacteria. Decreases in Insoluble Carbon explain the relatively small increase in TOC between 1998 and 2018. The % extracted with 0.1 N H2SO4 is significantly larger in 2018, suggesting active weathering. Similarly, both the maxima and minima of total Humic and Fulvic acids content, extracted with 0.1 M Na4P2O7 + 0.1 M NaOH, are significantly greater in 2018. Total microflora shows significant positive correlations with time-since-tree-planting as do the proportions of bacilli and actinomycetes but the correlation with ammonifying bacteria is negative. In 1998, the microflora was dominated by non-spore-forming bacteria while, in 2018, bacilli and actinomycetes prevail; both are involved in the transformation of complex organic compounds and humification. This indicates active transformation of more complex organic compounds and advancing humification. In sum, forestation of these degraded, formerly reclaimed, opencast coal-mine spoils has resulted in a massive increase in both the size and functioning of the soil organic system.