Seasonal periodicity of plankton and benthic fauna community structure and diversity in a small North African reservoir

Abstract

Aquatic biota in terms of phytoplankton, zooplankton and benthic fauna were qualitatively and quantitatively followed seasonally during 2007 in a North African small reservoir, Aswan Reservoir. Simultaneously, seasonal variations in water quality were investigated in order to determine how far the aquatic biota could be altered by physicochemical and biotic factors. In phytoplankton of the investigated reservoir, 75 species belonging to four systematic groups were recorded, comprising 11 Cyanoprokaryota, 24 Bacillariophyceae, 2 Dinophyceae and 38 Chlorophyceae. Most numerous zooplankton were Rotifera (23 species). Cladocera and Copepoda were less numerous, with only seven and three species, respectively. Early development stages of copepods, nauplii and copepodites were sometimes recorded in considerable numbers. Twenty‐two invertebrate species related to five animal groups were exclusively benthic fauna: three Oligochaeta, nine Mollusca, seven larvae of Chironomidae, one Platyhelminthes, one Hirudinea and one Decapoda. Generally, the estimated values of phytoplankton species richness were relatively higher than those of zooplankton or benthic fauna. In particular, phytoplankton was influenced by physicochemical factors – water transparency, salinity and soluble reactive silica contents – as well as biotic factors – zooplankton and benthic fauna. Levels of pH value, Mg+2, NO3‐N and chlorophyll‐a contents appeared to be the most influential parameters dictating the pattern of seasonal periodicity of benthic fauna. Numerically, the phytoplankton was somewhat more abundant in winter and autumn than in spring or summer. The peak of zooplankton population densities was observed in spring season. Benthic fauna tended to be abundant in summer and autumn seasons, showing a reverse seasonal trend from that of zooplankton. Cyanoprokaryota and Bacillariophyceae were the most important groups that determined the seasonal fluctuation pattern of phytoplankton. Rotifera and Copepoda were the most predominant groups influencing the seasonal periodicity of zooplankton. Oligochaeta and Mollusca alternated the dominancy of benthic fauna community in Aswan Reservoir.

Dietary analysis of caprellids Caprella penantis and Caprella grandimana (Crustacea: Amphipoda) in southern Spain

“…The macroalgal contribution to the diet increased in both species from April to August, when maximum seaweed biomass occurs, whereas both species decreased their feeding on macroalgae during cold months when seaweed abundance was at its lowest. A similar seasonal abundance pattern has been confirmed for copepods in a number of freshwater (Iskaros and El-Otify 2012) and marine ecosystems worldwide (Jaschinski et al 2011;Kurt and Polat 2012;Rajkumar et al 2013). Therefore, the higher percentage of prey consumed during summer can be explained by an increase in crustacean availability from April to August.…”

Ecological studies on macrobenthic invertebrates in four northern Khors of Lake Nasser (Egypt); Community Structure, Relative Abundance and Diversity.

“…Train (1979) and Delince (1992) mentioned that pH range between 6.5 and 9.0 is more suitable for the aquatic fresh water life. Iskaros and El-Otify (2013) recorded the pH values in Aswan Reservoir between a minimum of 7.34 during winter and maximum of 7.95 in spring and found the increased density of macrobenthic invertebrates was usually accompanied with the increased pH values.…”