Linking seaweed farming with coral restoration: Bioremediation boosts early coral survivorship

Résumé fourni par la source

Abstract Rising atmospheric carbon dioxide and declining water quality threaten coral reef ecosystems. The aquaculture of select seaweed species has been suggested to be a key part of the solution to these pervasive challenges. However, there are no empirical investigations of the impact of seaweed farming on coral reefs. Here, we partnered with the 350‐year‐old Hawaiian fishpond Waikalua Loko Iʻa to examine if aquaculture of the seaweed Gracilaria tikvahiae can enhance Montipora capitata survival and growth across coral life stages (juvenile and clonal adult colonies). Tanks that contained seaweed showed improved water quality, specifically by increasing oxygen and pH and reducing dissolved inorganic nutrients such as ammonium. Remarkably, the observed remediation of seawater with seaweed led to 35% greater survival amongst cultured juvenile corals. While adult corals trended towards greater calcification and extension rates in tanks with seaweed, these patterns were statistically indistinguishable from tanks without seaweed; these findings suggest that in some situations, seaweed co‐culture may not adversely impact and may benefit coral growth. Synthesis and applications. These findings improve our understanding of seaweed cultivation on coral reefs, highlighting the ways in which farmed seaweed can improve water quality and enhance early coral survival. Linking coral restoration with a commercially viable seaweed industry creates a scalable, market‐driven mechanism to overcome costly post‐settlement survival bottlenecks in sexually propagated corals. This integrated aquaculture‐restoration model demonstrates how coupling ecosystem service provisioning with reef rehabilitation can simultaneously generate economic returns and increase the efficiency and resilience of coral recovery efforts under climate warming and eutrophication. Further, the management of local stressors (e.g. excess nutrients) can improve coral reef resilience against thermal stress, and the outcomes of our research are translatable to areas where increased nutrient loads from sewage and/or fertilizer runoff are degrading water quality and in turn, coral reef communities. Implementing targeted and locally informed seaweed aquaculture may be a solution to remediate coastal waters and to build coral reef resilience to environmental change.

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