The world’s coral reefs are at great risk because of changes to the marine environment caused by pollution, ocean warming, acidification and overfishing.
Coral Reefs in Crisis
In the Caribbean, Staghorn coral (Acropora cervicornis) is the main reef-building coral. There has been a decline of at least 80% in the Caribbean since the 1980´s, and in 2006 it was categorised as ‘Critically Endangered’ by International Union for the Conservation of Nature (IUCN) , just a category away from ‘Extinct in the Wild’
The work of Expedition Akumal aims to proliferate the native staghorn population, in order to replenish the reef locally and balance out the macroalgae : coral ratio to a healthier level. There are many other threats to the staghorn population… we aim to reduce their impact by increasing the Staghorn base population size.
The main threats to Staghorn coral in the Caribbean
Ocean warming is changing the marine enviornment globally. Extreme rises in temperature can lead to coral bleaching, when a coral expels it’s polyps in times of stress.
Acidification makes life harder for hard corals such as staghorn as their calcium skeleton is slowly dissolved in acidic conditions.
Sedimentation is a particular problem for staghorn because of this species dependence on sunlight and its inability to remove sediment. Land runoff is exacerbated by development and clearing of areas previously covered with vegetation, and the sediment carried in the water running off of the land is deposited onto the coral reefs close to the shore.
Land water runoff also carries fertilisers, insecticides and other organic material. This nutrient loading of the water causes algal blooms. High levels of microscopic algae (phytoplankton) in the water column decreases the sunlight available to the coral, whilst the thriving macroalgae can colonise dead corals and any other available substrate in the reef ecosystem.
Increased algal growth is exacerbated by the overfishing of herbivores which would usually keep the algal population under control.
Disease outbreaks such as White Band Disease (WBD) cause mass mortality events, changing the ecology of the coral reef.
Mass mortality of the once common herbivorous sea urchin Diadema has also had a substantial impact on the ecosystem balance.
The combination of all these factors has seen a recent phase shift on the reefs from a historical base of hard corals such as staghorn to one of algal dominance.
It is obvious to see the devastation of these mutiple threats. Here in Akumal there are large sandy spots full of the remnants of dead colonies. These areas were clearly once home to huge colonies of staghorn, providing habitat to many other species.