Temporal patterns in phytoplankton, zooplankton and fish composition, abundance and biomass in Shirati Bay, Lake Victoria, Tanzania

Abstract

Shirati Bay is among the important breeding and nursery sites for major fish species in Lake Victoria. Weekly samplings were conducted to assess the temporal patterns in phytoplankton, zooplankton and fish composition, abundance and biomass in relation to prevailing water quality parameters. The study also determined the influences of plankton dynamics and water quality on the fish catch composition and biomass. It was hypothesized that temporal patterns in the composition, abundance and biomass in the plankton in the bay are controlled by water quality parameters that, in turn, affect the composition and biomass of fish catches. The phytoplankton comprised mainly cyanophytes and bacillariophytes, while the zooplankton were dominated by copepods. The heavy rain season exhibited a significantly higher plankton abundance and biomass than the dry season. The plankton abundances in both seasons exhibited significant positive correlations with water temperature and transparency. The phytoplankton community was controlled by calanoid and cyclopoid species. At higher trophic levels, Lates niloticus juveniles, Oreochromis niloticus juveniles and haplochromines controlled Cladocera and Cyclopoid copepods, while Tilapia rendalli juveniles controlled the Rotifera. This study revealed that Cyanophyta and Bacillariophyta are the dominant phytoplankton, whereas cyclopoids dominate the zooplankton species in the bay. These dominant plankton groups are partly controlled by rainfall, water temperature and transparency. Fish biomass, zooplankton and phytoplankton exhibit a typical predator-prey inverse relationship. Thus, evaluation of the plankton composition, abundance and biomass should be mandatory during fisheries stock assessments to effectively manage the fishery resources in the bay.

Modeling Dynamic Processes in the Black Sea Pelagic Habitat—Causal Connections between Abiotic and Biotic Factors in Two Climate Change Scenarios

“…The nutritional quality of phytoplankton significantly influences the food web, primarily through its relationship with zooplankton. Therefore, to ensure efficient stock management and optimize fishing resources, it is crucial to consistently assess the trophic interactions among phytoplankton, zooplankton, and fish within fishery management practices [99]. Diminished future phytoplankton biomass will favor the development of gelatinous food webs.…”

The dynamics of the plankton community on Lake Siombak, a tropical tidal lake in North Sumatra, Indonesia

“…Meanwhile, at low tide, the abundance of phytoplankton was affected by TSS, water transparency, BOD, and silica with an R square value of 0.97 and a correlation value of 0.95. Waya et al (2017) found that transparency significant effect on the abundance of plankton in the lake Lake Victoria, Tanzania. Furthermore, Takarina et al (2019) also found a strong relationship between phytoplankton and the intensity of sunlight and nutrients in the coastal waters of Banten.…”

Nutrient release from sediments and biological nitrogen fixation: Advancing our understanding of eutrophication sources in Lake Victoria, Tanzania

“…These levels indicate significant eutrophication possibilities because of nutrient enrichment (Dodds & Whiles, ). Lake Victoria has been defined by several authors as an eutrophic lake (Hecky, Mugidde, Ramlal, Talbot, & Kling, ; Mugidde, ; Waya, Limbu, Ngupula, Mwita, & Mgaya, ). However, the contribution of nutrients enrichment from sediments to eutrophication is currently unknown.…”