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Increasing dominance of small zooplankton with toxic cyanobacteria
Author(s) -
Jiang Xiaodong,
Xie Jinghua,
Xu Yao,
Zhong Wangfang,
Zhu Xiao,
Zhu Chengdan
Publication year - 2017
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/fwb.12877
Subject(s) - daphnia pulex , zooplankton , bosmina , dominance (genetics) , biology , cladocera , ecology , daphnia , pulex , copepod , abundance (ecology) , branchiopoda , cyanobacteria , microcystin , crustacean , biochemistry , bacteria , gene , genetics
Summary Cyanobacterial blooms are often associated with an increase in abundance of small‐bodied zooplankton. The hypothesis that toxic cyanobacteria lead to in the dominance of small‐bodied zooplankton was tested by investigating competitive outcomes with three common cladoceran species, analysing cladoceran remains in sediments, and identifying zooplankton resting eggs. Although the large‐bodied cladoceran Daphnia pulex outcompeted the medium‐sized cladoceran Simocephalus vetulus when fed green algae in laboratory experiments, the presence of toxic cyanobacteria completely altered this competitive outcome. Similar shifts in competitive dominance with the presence of cyanobacteria were observed when both D. pulex and S. vetulus competed with the small‐bodied cladoceran Bosmina longirostris . Sediment cores from Dianshan Lake, the largest shallow lake in Shanghai, and surface sediments from 10 random ponds and rivers in the area were collected to recover the cladoceran and total zooplankton communities. Microcystin concentrations in sediments were used as a proxy for cyanobacterial abundances in nature. Altogether, cladoceran remains representing 10 genera were recovered from the sediment samples. Microcystin concentrations in the Dianshan Lake sediment cores were positively correlated with Bosmina abundance, but negatively correlated with both Daphnia and Diaphanosoma abundance. The proportion of large‐bodied cladocerans significantly declined in relation to small‐bodied species with increasing microcystin concentrations in the lake sediments. Fifty‐eight types of zooplankton resting eggs were recovered in sediments from Shanghai waters and identified using DNA barcoding. The abundance of both a lecanid rotifer and total rotifers significantly increased with increasing cyanobacteria in the sediment cores, whereas the dominant copepod, Sinocalanus tenellu s, decreased. However, these trends were not observed in comparison of surface sediments from 10 ponds and rivers in the area. These results indicate that the presence of toxic cyanobacteria may have altered the zooplankton communities and contributed to increased dominance of small‐bodied species. This study also demonstrates that cladoceran remains and zooplankton resting eggs recovered from sediment cores are convenient natural archives for evaluating zooplankton responses to cyanobacterial blooms.