Cold water shock is linked to catastrophic coral collapse in the Eastern Pacific, according to a new study.
Climate change-related marine heat waves are recognized to be the cause of mass mortality in some of the world’s most famous coral reef systems.
Scientists have discovered, however, that the underlying cause of a catastrophic coral die-off event was an extreme weather event that resulted in rapid sea temperature drops of up to 10 degrees.
The extent of the coral reef collapse in Costa Rica’s Eastern Tropical Pacific in 2009 was abnormally high due to widespread increases in harmful algal blooms.
The two factors caused some locations’ coral cover to decline by 20% to 100%, and degrees of recovery have varied greatly in the years since.
Researchers claim that their results from a recent study, which was published in the journal PeerJ, show that upwellings, which cause water temperatures to suddenly drop, are an important aspect to take into account when attempting to manage reef systems.
An international team of scientists led by the University of Plymouth performed the study in collaboration with organizations including Raising Coral and ACG that support the conservation of Costa Rica’s coral reefs.
They used 25 years of reef survey and sea surface temperature data to document changes in coral cover and the composition of six marginal reefs in relation to thermal highs and lows.
In doing so, they were able to paint a comprehensive picture of local coral health status and quantify the magnitude of coral population declines while also establishing the implications for effective conservation and restoration strategies.
In the study, they say the lack of overall coral recovery in the decade since the initial event indicates the region’s ecosystem had reached a tipping point.
As a result, they propose a locally tailored – but globally scalable – approach to coral reef declines that is founded in resilience-based management and restoration but also informed by coral health dynamics.
Such measures, with careful management, could enable reefs to recover and continue supporting ecological and societal ecosystem services in spite of the escalating threats posed by climatic changes.
Dr. Robert Puschendorf, Lecturer in Conservation Biology at the University of Plymouth, said: “The demise of coral reefs is very much linked to global warming and marine heatwaves. However, local and tailor-made conservation strategies might help to conserve the remaining reefs in our ocean. If we involve local communities and improve governance on how we manage waste water and other factors, that can decrease the extent and intensity of the harmful algal blooms. The issues of global warming and extreme climate events are obviously something far bigger, but this study demonstrates the actions people can take in the meantime.”
Reference: “Cold water and harmful algal blooms linked to coral reef collapse in the Eastern Tropical Pacific” by Caroline Palmer, Carlos Jimenez, Giovanni Bassey, Eleazar Ruiz, Tatiana Villalobos Cubero, Maria Marta Chavarria Diaz, Xavier A. Harrison and Robert Puschendorf, 28 September 2022, PeerJ.