Abstract
Although it is well established that climate warming can reinforce eutrophication in shallow lakes by
altering top-down and bottom-up processes in the food web and biogeochemical cycling, recent studies
in temperate zones have also shown that adverse effects of rising temperature are diminished in fishless
systems. Whereas the removal of zooplanktivorous fish may be useful in attempts to mitigate eutrophication
in temperate shallow lakes, it is uncertain whether similar mitigation might be achieved in
warmer climates. We compared the responses of zooplankton and phytoplankton communities to
climate warming in the presence and absence of fish (Aristichthys nobilis) in a 4-month mesocosm
experiment at subtropical temperatures. We hypothesized that 1) fish and phytoplankton would benefit
from warming, while zooplankton would suffer in fish-present mesocosms and 2) warming would favor
zooplankton growth but reduce phytoplankton biomass in fish-absent mesocosms. Our results showed
significant interacting effects of warming and fish presence on both phytoplankton and zooplankton. In
mesocosms with fish, biomasses of fish and phytoplankton increased in heated treatments, while biomasses
of Daphnia and total zooplankton declined. Warming reduced the proportion of large Daphnia in
total zooplankton biomass, and reduced the zooplankton to phytoplankton biomass ratio, but increased
the ratio of chlorophyll a to total phosphorus, indicating a relaxation of zooplankton grazing pressure on
phytoplankton. Meanwhile, warming resulted in a 3-fold increase in TP concentrations in the mesocosms
with fish present. The results suggest that climate warming has the potential to boost eutrophication in
shallow lakes via both top-down (loss of herbivores) and bottom-up (elevated nutrient) effects. However,
in the mesocosms without fish, there was no decline in large Daphnia or in total zooplankton biomass,
supporting the conclusion that fish predation is the major driver of low large Daphnia abundance in
warm lakes. In the fishless mesocosms, phytoplankton biomass and nutrient levels were not affected by
temperature. Our study suggests that removing fish to mitigate warming effects on eutrophication may
be potentially beneficial in subtropical lakes, though the rapid recruitment of fish in such lakes may
present a challenge to success in the long-term
altering top-down and bottom-up processes in the food web and biogeochemical cycling, recent studies
in temperate zones have also shown that adverse effects of rising temperature are diminished in fishless
systems. Whereas the removal of zooplanktivorous fish may be useful in attempts to mitigate eutrophication
in temperate shallow lakes, it is uncertain whether similar mitigation might be achieved in
warmer climates. We compared the responses of zooplankton and phytoplankton communities to
climate warming in the presence and absence of fish (Aristichthys nobilis) in a 4-month mesocosm
experiment at subtropical temperatures. We hypothesized that 1) fish and phytoplankton would benefit
from warming, while zooplankton would suffer in fish-present mesocosms and 2) warming would favor
zooplankton growth but reduce phytoplankton biomass in fish-absent mesocosms. Our results showed
significant interacting effects of warming and fish presence on both phytoplankton and zooplankton. In
mesocosms with fish, biomasses of fish and phytoplankton increased in heated treatments, while biomasses
of Daphnia and total zooplankton declined. Warming reduced the proportion of large Daphnia in
total zooplankton biomass, and reduced the zooplankton to phytoplankton biomass ratio, but increased
the ratio of chlorophyll a to total phosphorus, indicating a relaxation of zooplankton grazing pressure on
phytoplankton. Meanwhile, warming resulted in a 3-fold increase in TP concentrations in the mesocosms
with fish present. The results suggest that climate warming has the potential to boost eutrophication in
shallow lakes via both top-down (loss of herbivores) and bottom-up (elevated nutrient) effects. However,
in the mesocosms without fish, there was no decline in large Daphnia or in total zooplankton biomass,
supporting the conclusion that fish predation is the major driver of low large Daphnia abundance in
warm lakes. In the fishless mesocosms, phytoplankton biomass and nutrient levels were not affected by
temperature. Our study suggests that removing fish to mitigate warming effects on eutrophication may
be potentially beneficial in subtropical lakes, though the rapid recruitment of fish in such lakes may
present a challenge to success in the long-term
| Original language | English |
|---|---|
| Pages (from-to) | 304-311 |
| Journal | Water Research |
| Volume | 144 |
| DOIs | |
| Publication status | Published - 01 Nov 2018 |
Keywords
- Climate warming
- Fish removal
- Eutrophication
- Top-down control
- Shallow lakes
- international