The impacts of climate change on plankton as live food: A review

Climate change is expected to warm up the ocean surface where majority of life inhabits. Ocean warming influences vertical mixing and stratification patterns, which alter nutrient cycle, plankton production, and aquatic food web. Plankton serves as the first food source for all larval organisms and the base of aquatic ecosystem. Zooplankton community is a crucial component of the aquatic food web. They are critical components in an ecosystem of aquatic and worldwide biogeochemical cycles. Zooplankton contributes as food source to economically valuable fishes, primary-production grazers, and carbon and nutrient cycle drivers. Climate change contributes to dire consequences by altering the baseline of aquatic food web structure. However, the ocean biota itself can influence climate change, and the implications of this are evident from the increase and decrease of wild fisheries production. This review highlights the effect of climate change on phytoplankton and zooplankton production.

Levels of selected pesticides and trophic transfer of DDTs through the aquatic food web in the Lake Ziway ecosystem

The levels of 27 selected pesticides and trophic biomagnification of DDT were investigated in biota samples of the Lake Ziway in the Rift valley region, Ethiopia. Pesticide residues were analyzed using gas chromatography coupled with mass spectrometry (GC MS). Carbon source and trophic position were calculated by using 13C and 15N stable isotopes, individually, and trophic magnification factors (TMFs) were inferred. Among pesticides analyzed, only DDT and its metabolites (o,pʹ-DDD, o,pʹ-DDE, p,pʹ-DDD, and p,pʹ-DDE) were quantified in biota samples. The most prominent metabolite was p,pʹ-DDE with mean concentration ranging from the 0.22-7.7ngg− 1 wet weight. Moreover, the ratio of DDT/DDD + DDE in all the biota samples was less than 1 signifying historical DDT application. The trophic magnification factor (TMF) for p,pʹ-DDE, and ΣDDT were 1.18 and 1.19 respectively. Regression of log [ΣDDT] vs TL (trophic level) among all biota species showed a significant correlation, indicating that DDTs are biomagnifying along with the food web of Lake Ziway. The concentrations of DDTs and other organochlorine pesticides found in biota from Lake Ziway were, in general, lower than studies found in previous studies carried out in the same lake.

Relative Abundance and Invasion Dynamics of Alien Fish Species Linked to Chemical Conditions, Ecosystem Health, Native Fish Assemblage, and Stream Order

The incidence and dispersal of invasive alien fish species (IAFS) have ecological impacts on biodiversity and environmental health at regional to global scales. We identified links between the presence of largemouth bass (Lb) and bluegill (Bg), and selected indicators of environmental water quality, trophic and tolerance guilds, ecological health factors, and stream order. We used the data collected from national biomonitoring study sites in four major rivers of South Korea. IAFS occurred in eutrophic waters (Lb = total phosphorus: 140 ± 170 µg/L, chlorophyll a: 16.7 ± 27.5 µg/L; Bg = total phosphorus: 160 ± 190 µg/L, chlorophyll a: 19.43 ± 28.05 µg/L) and dominated at higher ambient ratios of total nitrogen to total phosphorus (TN:TP). At TN:TP ≤ 100, the relative abundance of Lb and Bg was highest (95.3% and 96.0%, respectively). Concerning tolerance guilds, Lb (R2 = 0.78, p < 0.0001) and Bg (R2 = 0.59, p < 0.0001) had positive relationships with tolerant species in all four river watersheds and negative relationships with the percentages of insectivores and omnivores. This indicates the harmful impacts of IAFS on the aquatic food web. These invasive fish species also influenced stream health, particularly in the Nakdong and Yeongsan/Seomjin rivers. Our findings suggest that assessing chemical water quality can help identify the optimal and suboptimal survival and spread ranges of IAFS (Lb and Bg), as they directly influence tolerance and trophic guilds in the aquatic food web. In conclusion, these IAFS could be a major factor in the deteriorating ecosystem health, which had negative relationships with the abundance and occurrence of IAFS. Therefore, approaches that use appropriate water chemistry factors and species tolerance may provide critical insights into the efficient management of river health that has been perturbed by the presence of IAFS.