RESEARCH

Healthy Reefs

Long Term Records to Strengthen Our Understanding of Coral Resilience

Coral reefs are the largest mass of construction workers on the face of the earth. They are natural architects in the shallow sea but only remain productive when juvenile corals are able to survive after recruitment onto the reef. At every dive location on the reef around Little Cayman, we see evidence of recruitment. This is a good sign for the future.

Using the AGRRA, Atlantic Gulf Rapid Reef Assessment protocol and collecting additional recruitment data, this project investigates the potential for juvenile corals to survive and replenish the local reefs. Results from this work will help generate an understanding of the mechanisms that are driving reef resilience.

AGRRA data on the benthic habitat and fish populations surrounding Little Cayman has been collected regularly since 1999. As CCMI researchers continue to collect this data annually, notes, reports, and peer reviewed journal articles are available online to scientists, policy-makers, and the general public. These surveys document patterns of local change over the last two decades and enable regional comparisons through the Healthy Reef Framework developed for evaluating the Mesoamerican Barrier Reef.

Key Results from the latest Little Cayman Reef Report Card (released 2023):

Of the reefs surveyed, 11% were in “very good” health in 2022, 78% were “good”, and 11% were “fair”.
At the bottom end of the health spectrum, we had no surveyed reefs listed as in “poor” health.
Composition of the coral community on the reef has shifted over time, from reefs dominated by massive boulder corals, such as Orbicella spp., to smaller, weedy corals such as Agaricia spp. and Porites spp.
The size of corals surveyed has decreased by 86% overall, which may indicate that the reefs are less structurally robust and capable of providing some of the important services we depend upon them for, such as storm protection and complex habitats for a variety of marine life.
New coral recruits, or baby corals, have declined. Within that, researchers also see that of the species of recruits recorded, there are almost no Orbicella spp recruits and no Montastrea spp recruits after 2017, both of which are important boulder corals.
Fish abundance (density), biomass and species richness have all increased overall, particularly following the enhanced protection of Nassau groupers in 2016, indicating a rebounding fish population and positive ripple effects on overall reef health as a result of the protection of this key species.
Fish biomass has been higher inside of Marine Protected Areas (MPAs) compared to outside throughout the 24 years of surveys.
Grouper density has rebounded following protections enacted in 2016.
Shifts in species contributions, colony size and recruitment indicate that while coral cover remains high, coral populations are vulnerable.
Local protections and low human impact have undoubtedly shielded Little Cayman from the extremity of global pressures that are heavily impacting reefs around the globe; however, changes are still occurring that put the reefs increasingly at risk.