Feeding response of the tropical copepod Acartia erythraea to short-term thermal stress: more animal-derived food was consumed.

Simin Hu,Sheng Liu,Lingli Wang,Hui Huang,Tao Li

doi:10.7717/peerj.6129

Abstract

The objective of this study was to explore the feeding response of tropical copepods to short-term thermal shock and provide insight into the potential impact of coastal power plants on the trophic dynamics of tropical coastal ecosystems. Feeding experiments were conducted at three different temperatures (29 °C, 33 °C, and 35 °C) using the copepod Acartia erythraea, collected from Sanya Bay, China. The grazing rate of A. erythraea decreased dramatically in the high temperature treatment. Analysis of 18S rDNA clone libraries revealed that the diet of copepods from different treatments was mainly comprised of diatoms, metazoans, and protozoans; A. erythraea exhibited an obvious feeding preference shift with temperature, with a change from a diatom-dominated diet at 29 °C to a metazoan-dominated diet at 35 °C, and the omnivory index shifted from 0.1 to 2.84 correspondingly. Furthermore, A. erythraea showed a positive feeding response to plant food (i.e., phytoplankton and land plants) in the control treatment (29 °C), but a positive response to animal prey (i.e., metazoans and protozoans) at temperatures exceeding 33 °C, as evaluated by the Ivlev’s selectivity index. Our results suggest that copepods could regulate their food intake by considering their energy demands when exposed to short-term thermal stress, which might influence the pathway of materials moving up the trophic system. However, further studies are required to elucidate the effects of elevated temperature on feeding of different organisms in order to predict the influence of thermal pollution on the food web of tropical coastal ecosystems.

Highlights

Demand for electrical energy generation is increasing in coastal areas due to growing urbanization
Compared with the control group (29 ◦C), the feeding of A. erythraea was increased slightly at 33 ◦C, with the grazing rate increasing from 40.04 ± 0.07 to 40.14 ± 0.11 cells ind−1 h−1 and the filter rate increasing from 2.59 ± 0.04 to 3.34 ± 0.11 mL ind−1 h−1, respectively
At 35 ◦C, the grazing rate of A. erythraea dramatically decreased to 28.20 ± 0.14 cells ind−1 h−1, and the filter rate decreased to 0.44 ± 0.11 mL ind−1 h−1

Summary

Introduction

Demand for electrical energy generation is increasing in coastal areas due to growing urbanization. Seawater-cooled power plants provide an economical way to generate electricity and growing numbers of power plants are operating in coastal areas, especially in subtropical and tropical regions (Poornima et al, 2006). Information on variations in trophic interactions under thermal stress is vital for understanding the functioning of coastal ecosystems, especially in tropical ecosystems where organisms generally live at ambient temperatures that are relatively close to their upper thermal limits (Hoegh-Guldberg, 1999; Worthington et al, 2015)

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