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Lake surfaces are warming worldwide, raising concerns about lake organism responses to thermal habitat changes. Species may cope with temperature increases by shifting their seasonality or their depth to track suitable thermal habitats, but these responses may be constrained by ecological interactions, life histories or limiting resources. Here we use 32 million temperature measurements from 139 lakes to quantify thermal habitat change (percentage of non-overlap) and assess how this change is exacerbated by potential habitat constraints. Long-term temperature change resulted in an average 6.2% non-overlap between thermal habitats in baseline (1978–1995) and recent (1996–2013) time periods, with non-overlap increasing to 19.4% on average when habitats were restricted by season and depth. Tropical lakes exhibited substantially higher thermal non-overlap compared with lakes at other latitudes. Lakes with high thermal habitat change coincided with those having numerous endemic species, suggesting that conservation actions should consider thermal habitat change to preserve lake biodiversity.

We compiled and analyzed long-term (1961–2005) zooplankton community data in response to environmental variations in Lake Biwa. Environmental data indicate that Lake Biwa had experienced eutrophication (according to total phosphorus concentration) in the late 1960s and recovered to a normal trophic status around 1985, and then exhibited warming since 1990. Total zooplankton abundance showed a significant correlation with total phytoplankton biomass. Following a classic pattern, cladoceran/calanoid and cyclopoid/calanoid abundance ratio was related positively to eutrophication. Zooplankton community exhibited a significant response to the boom and bust of phytoplankton biomass as a consequence of eutrophication-reoligotriphication and warming. Moreover, our analyses suggest that the Lake Biwa ecosystem exhibited a hierarchical response across trophic levels; that is, higher trophic levels may show a more delayed response or no response to eutrophication than lower ones. <br><br> We tested the hypothesis that phytoplankton community can better explain the variation of zooplankton community than bulk environmental variables, considering that phytoplankton community may directly affects zooplankton succession through predator-prey interactions. Using a variance partition approach, however, we did not find strong evidence to support this hypothesis. We further aggregate zooplankton according to their feeding types (herbivorous, carnivorous, omnivorous, and parasitic) and taxonomic groups, and analyzed the aggregated data. While the pattern remains similar, the results are less clear comparing with the results based on finely resolved data. Our research explored the efficacy of using zooplankton as bio-indicators to environmental changes at various data resolutions

From 3 to 6 November 2002, a colloquium was convened at the Benthos Laboratory of the Stazione Zoologica Anton Dohrn on Ischia, Italy, with the goal of evaluating the present status of the effects of diatoms on their main consumers, planktonic copepods, and to develop future research strategies to enhance our understanding of such interactions. These included (1) toxic effects of diatom metabolites on copepods, particularly reproduction, and (2) nutritional effects of diatoms on juvenile to adult copepods. Key issues involved in the impact of diatoms on the dynamics of natural plankton communities in situ were also addressed. During the plenary session, the most recent advances on this topic were presented. The plenary session was followed by 3 working groups on (1) production of aldehydes by phytoplankton, (2) toxic and nutritional effects of diatoms on zooplankton, and (3) the chemistry of diatom defense, as well as of their nutritional quality. These working groups focused on suggesting future research needs for the different topics. As a result, several recommendations were outlined, including experimental studies. It became evident that interdisciplinary efforts are needed, involving chemists, oceanographers and experimentalists, since many of the biological observations under controlled conditions and in situ require an integrated approach, including chemical causation. Extensive field observations based on common protocols are also recommended for investigation of the intrinsic variability of such effects and their environmental controls. Laboratory experiments are seen to be essential for the full understanding of environmentally occurring processes.

We compiled and analyzed long-term (1961–2005) zooplankton community data in response to environmental variations in Lake Biwa. Environmental data indicate that Lake Biwa had experienced eutrophication (according to the total phosphorus concentration) in the late 1960s and recovered to a normal trophic status around 1985, and then has exhibited warming since 1990. Total zooplankton abundance showed a significant correlation with total phytoplankton biomass. Following a classic pattern, the cladoceran/calanoid and cyclopoid/calanoid abundance ratio was related positively to eutrophication. The zooplankton community exhibited a significant response to the boom and bust of phytoplankton biomass as a consequence of eutrophication-reoligotriphication and warming. Moreover, our analyses suggest that the Lake Biwa ecosystem exhibited a hierarchical response across trophic levels; that is, higher trophic levels may show a more delayed response or no response to eutrophication than lower ones. <br><br> We tested the hypothesis that the phytoplankton community can better explain the variation of the zooplankton community than bulk environmental variables, considering that the phytoplankton community may directly affect the zooplankton succession through predator-prey interactions. Using a variance partition approach, however, we did not find strong evidence to support this hypothesis. We further aggregated zooplankton according to their feeding types (herbivorous, carnivorous, omnivorous, and parasitic) and taxonomic groups, and analyzed the aggregated data. While the pattern remains similar, the results are less clear comparing the results based on finely resolved data. Our research suggests that zooplankton can be bio-indicators of environmental changes; however, the efficacy depends on data resolution

Pelagic zooplankton samples from Lake Biwa, Japan, collected monthly since 1971, were analyzed for biomass and body size structure. Our aim was to clarify the relative effects of food availability and global warming vs. top‐down control by fish predation on long‐term trends. Annual mean biomass and density‐weighted body size were calculated and compared with water temperature, total phosphorus (TP), as a proxy of food amount, and catch per unit effort (CPUE) of Ayu (Plecoglossus altivelis altivelis), as a proxy of planktivorous fish predation pressure. Mean water temperature above 20 m increased by 0.94°C. TP increased until 1974 and then decreased until 1985, becoming stable after that. Ayu CPUE increased until 1987 and then declined. The study period can be divided into two nutritional phases: a high TP phase (1971–1985) and a low‐stable TP phase (1986–2010). Five zooplankton taxa, Eodiaptomus japonicus, Cyclopoida spp., Daphnia spp., Bosmina longirostris, and Diaphanosoma orientalis, were continuously dominant. Annual mean total crustacean biomass varied from 0.3 to 3.6 g dry weight m−2, slightly decreasing until 1993 but increasing thereafter. Generalized linear models showed that annual mean body sizes were affected by temperature and CPUE, whereas annual mean biomass was affected by TP and CPUE. These had no effect during the high TP phase, whereas only CPUE affected both traits during the low‐stable TP phase. We concluded that zooplankton biomass and body size long‐term trends were mostly influenced by fish predation and that eutrophication and global warming impacts might be affected by top‐down control.