INTRA-CREATE SEED COLLABORATION

Background:

Ocean acidification, as a result of anthropogenic carbon emissions, threatens the survival of coral reefs, as well as that of many communities around the world whose livelihoods depend on healthy functioning coral reefs. Because we are still far from achieving a global reduction in carbon emissions, local-scale strategies have to be developed to mitigate ocean acidification impacts. This study examined the potential of using marine plants to create local pockets of refugia against ocean acidification for nearby coral reefs.

Results:

We found that seagrass in local waters can increase productivity with acidification (OA) and warming (+2°C), and their effect on seawater chemistry (for e.g. pH and dissolved oxygen (DO) levels) was strongly influenced by flow rates. Under simulated climate change – warming (OWA) and acidification (OA) – conditions, corals calcify at much slower rates. This could potentially affect the integrity of the coral reef structure. Within an aquaria setting, the presence of seagrass was able to maintain net calcification rates in the coral species that was more vulnerable to OWA and OA effects.

Field surveys were conducted to study the hydrological transfer of seawater from seagrass beds to adjacent coral reefs. Measurements of seawater chemistry in and around a seagrass bed off St John’s Island demonstrated differences in carbon dioxide concentration and pH between seagrass bed and adjacent sand areas. This suggested some degree of influence of marine plant on seawater chemistry within the seagrass bed. Year-long sampling revealed that the influence of seagrass on local seawater chemistry was dependent on daily tidal exchange as well as seasonal changes in longshore transport.

Conclusions:

Our study showed that marine plants can be a potential nature-based solution for mitigating OA impacts on nearby coral reefs. Singapore’s urbanised coastline hold great capacity for both human use and natural biodiversity. Adaptive and sensitive coastal planning can help protect the connectivity among local marine ecosystems, especially as climatic changes intensify, thus making future coastal works or marine operations more environmentally sustainable.