Influence of upwelling on coral reef benthic communities: a systematic review and meta-analysis

Highly competitive coral reef benthic communities are acutely sensitive tochanges in environmental parameters such as temperature and nutrient con-centrations. Physical oceanographic processes that induce upwellingtherefore act as drivers of community structure on tropical reefs. Howupwelling impacts coral communities, however, is not fully understood;upwelling may provide a natural buffer against climate impacts and couldpotentially enhance the efficacy of spatial management and reef conserva-tion efforts. This study employed a systematic review to assess existingliterature linking upwelling with reef community structure, and a meta-analysis to quantify upwelling impact on the percentage cover of coral reefbenthic groups. We show that upwelling has context-dependant effects onthe cover of hard coral and fleshy macroalgae, with effect size and directionvarying with depth, region and remoteness. Fleshy macroalgae were foundto increase by 110% on inhabited reefs yet decrease by 56% around one well-studied remote island in response to upwelling. Hard coral cover was notsignificantly impacted by upwelling on inhabited reefs but increased by150% when direct local human pressures were absent. By synthesizing exist-ing evidence, this review facilitates adaptive and nuanced reef managementwhich considers the influence of upwelling on reef assemblages