Ocean Warming and Acidification Modify Top-Down and Bottom-Up Control in A Tropical Seagrass Ecosystem

Abstract

Seagrass ecosystems are classified as one of the most productive ecosystems in coastal waters providing numerous of ecological functions, however various anthropogenic stressors including climate change are impacting these vulnerable habitats. Here, we investigated the independent and combined effects of ocean warming and ocean acidification on plant-herbivore interactions in a tropical seagrass community. Direct and indirect effects of high temperature and high pCO2 on the physiology of the tropical seagrass Thalassia hemprichii and sea urchin Tripneustes gratilla were evaluated. Productivity of seagrass was found to synergistically increase under the combination of high temperature and high pCO2, while sea urchin physiology including feeding rate decreased particularly under high temperature. The present study indicated that future climate change will affect the botom-up and top-down balance leading to a shift to a seagrass-dominated ecosystem, which potentially decrease biodiversity as well as ecosystem functions and services of tropical seagrass meadows.