A systematic review and meta-analysis of the direct effects of nutrients on corals

Authors

Eileen M. Nalley, University of Hawai'i at Mānoa
Lillian J. Tuttle, University of Hawai'i at Mānoa, University of Hawai'i at Hilo
Emily E. Conklin, University of Hawai'i at Mānoa
Alexandria L. Barkman, University of Hawai'i at Mānoa
Devynn M. Wulstein, University of Hawai'i at Mānoa
Madeline C. Schmidbauer, University of Hawai'i at Mānoa
Megan J. Donahue, University of Hawai'i at Mānoa

Date of this Version

9-24-2022

Citation

Science of the Total Environment 856 (2023) 159093. http://dx.doi.org/10.1016/j.scitotenv.2022.159093

Comments

U.S. government works are not subject to copyright.

Abstract

Chronic exposure of coral reefs to elevated nutrient conditions can modify the performance of the coral holobiont and shift the competitive interactions of reef organisms. Many studies have nowquantified the links between nutrients and coral performance, but fewhave translated these studies to directly address coastal water quality standards. To address this management need, we conducted a systematic review of peer-reviewed studies, public reports, and gray literature that examined the impacts of dissolved inorganic nitrogen (DIN: nitrate, nitrite, and ammonium) and dissolved inorganic phosphorus (DIP: phosphate) on scleractinian corals. The systematic review resulted in 47 studies with comparable data on coral holobiont responses to nutrients: symbiont density, chlorophyll α (chl-α) concentration, photosynthesis, photosynthetic efficiency, growth, calcification, adult survival, juvenile survival, and fertilization. Mixed-effects meta-regression meta-analyses were used to determine the magnitude of the positive or negative effects of DIN and DIP on coral responses. Zooxanthellae density (DIN & DIP), chl-α concentration (DIN), photosynthetic rate (DIN), and growth (DIP) all exhibited positive responses to nutrient addition; maximum quantum yield (DIP), growth (DIN), larval survival (DIN), and fertilization (DIN) exhibited negative responses. In lieu of developing specific thresholds for the management of nutrients as a stressor on coral reefs, we highlight important inflection points in the magnitude and direction of the effects of inorganic nutrients and identify trends among coral responses. The responses of corals to nutrients are complex, warranting conservative guidelines for elevated nutrient concentrations on coral reefs.