Abstract
Seagrass ecosystem is one of the most productive ecosystems in coastal waters providing numerous ecological functions and supporting a large biodiversity. 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 increase under 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 bottom-up and top-down balance, which potentially can modify the ecosystem functions and services of tropical seagrass ecosystems.
Highlights
Seagrass ecosystem is one of the most productive ecosystems in coastal waters providing numerous ecological functions and supporting a large biodiversity
There was a significant interaction between pressure of C O2 (pCO2) and temperature on leaf plastochrone interval (PL) of Thalassia hemprichii (GLM: F(1,20) = 4.627, p = 0.044) and the shortest PL (5.056 ± 0.952 days) was observed at high temperature and high pCO2 combined conditions (Tukey’s HSD post-hoc test: p < 0.05, Fig. 1a, Supplementary Table S1)
High pCO2 significantly increased Fv/Fm of T. hemprichii (two-way ANOVA: F(1,20) = 4.954, p = 0.038), while there was no significant effect of high temperature and interaction between pCO2 and temperature
Summary
Seagrass ecosystem is one of the most productive ecosystems in coastal waters providing numerous ecological functions and supporting a large biodiversity. Productivity of seagrass was found to increase under high pCO2, while sea urchin physiology including feeding rate decreased under high temperature. The present study indicated that future climate change will affect the bottom-up and top-down balance, which potentially can modify the ecosystem functions and services of tropical seagrass ecosystems. It can be suggested that the combined effects of ocean warming and acidification will alter the top-down control of herbivores and the bottom-up control by the seagrass, which may result in a change in the equilibrium regulating seagrass ecosystems. All studies are restricted to temperate species and there is no work addressing the effects of ocean warming and acidification on the tropical seagrass-herbivore interactions. Changes in seagrass abundances would have cascading effects over the entire ecosystem and it is essential to evaluate the effects of climate change on tropical species interactions
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