Diverse coral communities in mangrove habitats suggest a novel refuge from climate change

[摘要] Risk analyses indicate that more than 90% of the world's reefs will bethreatened by climate change and local anthropogenic impacts by the year 2030under "business-as-usual" climate scenarios. Increasing temperatures andsolar radiation cause coral bleaching that has resulted in extensive coralmortality. Increasing carbon dioxide reduces seawater pH, slows coral growth,and may cause loss of reef structure. Management strategies includeestablishment of marine protected areas with environmental conditions thatpromote reef resiliency. However, few resilient reefs have been identified,and resiliency factors are poorly defined.

Here we characterize the first natural, non-reef coral refuge from thermalstress and ocean acidification and identify resiliency factors formangrove–coral habitats. We measured diurnal and seasonal variations intemperature, salinity, photosynthetically active radiation (PAR), andseawater chemistry; characterized substrate parameters; and examined watercirculation patterns in mangrove communities where scleractinian corals aregrowing attached to and under mangrove prop roots in Hurricane Hole, St.John, US Virgin Islands. Additionally, we inventoried the coral species andquantified incidences of coral bleaching, mortality, and recovery for twomajor reef-building corals, Colpophyllia natans and Diplorialabyrinthiformis, growing in mangrove-shaded and exposed (unshaded) areas.

Over 30 species of scleractinian corals were growing in association withmangroves. Corals were thriving in low-light (more than 70% attenuationof incident PAR) from mangrove shading and at higher temperatures than nearbyreef tract corals. A higher percentage of C. natans colonies wereliving shaded by mangroves, and no shaded colonies were bleached. Fewer D.labyrinthiformis colonies were shaded by mangroves, however more unshadedcolonies were bleached. A combination of substrate and habitat heterogeneity,proximity of different habitat types, hydrographic conditions, and biologicalinfluences on seawater chemistry generate chemical conditions that bufferagainst ocean acidification. This previously undocumented refuge for coralsprovides evidence for adaptation of coastal organisms and ecosystemtransition due to recent climate change. Identifying and protecting othernatural, non-reef coral refuges is critical for sustaining corals and otherreef species into the future.

[学科分类] 地球化学与岩石