Impacts of Seagrass on Benthic Microalgae and Phytoplankton Communities in an Experimentally Warmed Coral Reef Mesocosm

Fung-Chi Ko,Jing-O Cheng,Kwee Siong Tew,Pei-Jie Meng,Anderson B Mayfield,Pi-Jen Liu,Jimmy Kuo

doi:10.3389/fmars.2021.679683

Abstract

The effects of seagrass on microalgal assemblages under experimentally elevated temperatures (28°C) and CO2 partial pressures (pCO2; 800 μatm) were examined using coral reef mesocosms. Concentrations of nitrate, ammonium, and benthic microalgal chlorophyll a (chl-a) were significantly higher in seagrass mesocosms, whereas phytoplankton chl-a concentrations were similar between seagrass and seagrass-free control mesocosms. In the seagrass group, fewer parasitic dinoflagellate OTUs (e.g., Syndiniales) were found in the benthic microalgal community though more symbiotic dinoflagellates (e.g., Cladocopium spp.) were quantified in the phytoplankton community. Our results suggest that, under ocean acidification conditions, the presence of seagrass nearby coral reefs may (1) enhance benthic primary productivity, (2) decrease parasitic dinoflagellate abundance, and (3) possibly increase the presence of symbiotic dinoflagellates.

Highlights

Seagrass meadows are common in coastal waters (Unsworth et al, 2012, 2019b) and support diverse fish and invertebrate communities
At 25◦C, when CO2 was bubbled into the six mesocosms, all nutrient concentrations except NH3− were significantly higher in the seagrass group (Figure 3 and Table 1)
A previous study has shown that increasing CO2 may boost benthic microalgal primary productivity in coral reef ecosystem (Tew et al, 2017b)

Summary

Introduction

Seagrass meadows are common in coastal waters (Unsworth et al, 2012, 2019b) and support diverse fish and invertebrate communities (de los Santos et al, 2019; Unsworth et al, 2019a; Liu et al, 2020). They offer a number of ecosystem services to humans, including coastline protection, serving as habitats for commercially important food sources, and mitigation of climate change impacts. Algal blooms can reduce light intensity, which inhibits seagrass growth (Tiling and Proffitt, 2017) These studies highlight the complex dynamic between seagrass and Impacts of Seagrass on Microalgae

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Results

Conclusion