Mesophotic Coral Ecosystems Inside and Outside a Caribbean Marine Protected Area

Abstract

Recent widespread shallow coral reef loss has led to calls for more holistic approaches to coral reef management, requiring inclusion of all ecosystems interacting with coral reefs in management plans. Yet almost all current reef management is biased towards shallow reefs, and overlooks that many reef species can also be found on mesophotic coral ecosystems (MCEs; reefs 30 -150 m). This study presents the first detailed quantitative characterisation of MCEs off Cozumel, in the Mexican Caribbean and provides insights into their general state. We investigate whether MCEs within the marine park have similar ecological communities to mesophotic reefs outside protection, despite widely recognised shallow reef impacts outside the protected area. Results show some taxon specific differences in MCE benthic communities between sites within the protected area and areas outside; although overall communities are similar. Regardless of protection and location, and in contrast to shallow reefs, all observed Cozumel MCEs were continuous reefs dominated by calcareous macroalgae, sponges, octocorals, and black corals. Hard corals were present on MCEs, but at low abundance. We found that 42.5 % of fish species recorded on Cozumel could be found on both shallow reefs and MCEs, including many commercially-important fish species. This suggest that MCEs may play a role in supporting fish populations. However, regardless of protection status and depth we found that large-body fishes (>500 mm) were nearly absent at all studied sites. MCEs should be incorporated into the existing shallow-reef focused management plan in Cozumel, with well informed and implemented fisheries and harvesting regulations.