A study of methods for the classification of bottom deposits of natural waters
The study of the role of bottom sediments of rivers and maturation ponds in the purification of polluted waters which flow over them has been handicapped by lack of suitable methods for classifying sediments according to their physical, chemical and biochemical characteristics . Bottom deposits of lakes, rivers and dams may be regarded as soils which have developed under humid and water-logged conditions . The judicious application of the methods developed by soil scientists for the assessment of agricultural soils to the evaluation of certain important characteristics of sediments is therefore a logical development. Pioneering work in this respect was done by ZULLIG (1955) who applied a number of the methods of soil analysis to bottom deposits of eutrophic and oligotrophic lakes in Switzerland and attempted to correlate the results with the degree of trophy of the lake. Both he and OHLE (1955) pointed out that bottom deposits have ion-exchange properties which can contribute to the removal of ions from the water phase into the muds, but neither of these workers attempted to measure the extent to which this occurs quantitatively. In the present study a number of methods used to determine chemical, physical and biochemical properties of soils have been applied to bottom sediments from the Apies River near Pretoria, including samples taken near its origin where it is free from pollution, below the point of discharge of treated effluent from the Pretoria Sewage Works, where considerable pollution occurs and further
Properties and distribution of sediment in the Salton Sea, California: an assessment of predictive models
The Salton Sea is the largest lake, on a surface area basis, in California (939 km2). Although saline (>44 g/l) and shallow (mean depth approximately 9.7 m), it provides valuable habitat for a number of endangered species. The distribution of sediments and their properties within the Salton Sea are thought to have significant influence on benthic ecology and water quality. Sediment properties and their distribution were quantified and compared with predicted distributions using several sediment distribution models. Sediment samples (n = 90) were collected using a regular staggered-start sampling grid and analyzed for water content, organic carbon (C), calcium carbonate, total nitrogen (N), total phosphorus (P), organic phosphorus, and other properties. Water content, total N, and total and organic P concentrations were all highly correlated with organic C content. The organic C concentration showed a non-linear increase with depth, with low organic C contents (typically 1–2%) present in sediments found in depths up to 9 m, followed by a strong increase in organic C at greater depths (to about 12% at 15 m depth). The models of Hakanson, Rowan et al., Blais and Kalff, and Carper and Bachmann yielded very different predicted critical depths for accumulation (10.5–22.8 m) and areas of accumulation (0–49.5%). Hakanson’s dynamic ratio model more reasonably reproduced the observed zone of elevated organic C concentrations in the Salton Sea than either exposure- or slope-based equations. Wave theory calculations suggest that strong winds occurring less than 1% of the time are sufficient to minimize accumulation of organic matter in sediments that lie at depths less than 9 m in this system.
Morpho-biometric Relationship, Relative Condition Factor and Meat Yield of Distant Scallop Bractechlamys vexillum (Reeve, 1853) in Asid Gulf, Philippines
Understanding the relationships of morphometric and biometric characters of a species allows the prediction of one trait from the other and generate a measure of relative condition. These relationships were studied for the Distant scallop Bratechlamys vexillum (Reeve, 1853) in Asid Gulf. Representative samples collected during the dry season (May 2018, n = 99) and wet season (September 2018, n = 100) were used to analyse these relationships through models of simple linear and power regression analyses, revealing allometric growth patterns. For both periods, it was revealed that shell width (SW) is a slightly better predictor than the height (SH) for total weight (TW) (R2 = 0.90 and 0.92) and the adductor muscle weight (AW) (R2 = 0.78 and 0.80). The strong functional relationship was also observed between TW and AW (R2 = 0.80 and 0.81). The relative condition factors (Kn) were high in both seasons. High meat yields were also observed in May (12.77 %) and September (14.26 %). The significant difference in meat yields (P < 0.05) can be a result of the seasonal difference manifested by the dynamics of energy partitioning during gametogenesis and spawning. These biological metrics are vital inputs in analysing mariculture prospects for the resource and a contribution to the scarce information on the biology of the species.