COSTA RICA THERMAL DOME
In the tropical East Pacific Ocean, off the coast of Central America, there is a phenomenon that is persistent enough from year to year to be considered as an oceanographic feature – it is referred to as the Costa Rica Thermal Dome (CRTD). The feature, which can be up to 1,000 km in diameter, results from the interaction of swirling wind and ocean currents that cause the vertical conveyance of cold, nutrient-rich waters from the deep ocean towards the surface. As this body of cold water bulges dome-like up into the water column, the warmer water above it is displaced laterally, resulting in a thinner layer of warm water above the upwelling than in surrounding areas. Where nutrient-rich cold water meets warmer water close to the sunlit surface, planktonic algae thrive, sustaining a food chain of grazing zooplankton, filter-feeding forage fish, their predators such as tuna fish and diving birds, followed by sharks, dolphins, rays and whales. The whole feature is an oasis of productivity and a biodiversity hotspot that attracts animals from far and wide, with many migratory animals using it as a staging post during their long journeys across the ocean.
The CRTD’s biological pulling power has not gone unnoticed by people in nearby countries of Central America. Consistent concentrations of usually well-dispersed animals so close to their shores has led to the establishment of several industries and activities that exploit such a seemingly dependable resource, including commercial and recreational fishing, and wildlife-based tourism. These industries are worth millions of dollars to the national economies and are prone to overexploitation. A less obvious threat to the ecological integrity of the CRTD is the incessant marine traffic that traverses the feature following one of the busiest maritime trade routes in the world, form North Asia and America towards the Panama Canal, and vice versa. Collisions with whales and pollution events from ships are likely to be far more numerous than presently recorded.
Whilst the existence of the CRTD has been known for some time, the realisation of its importance to both the ecosystem beyond its limits and to Central American society is only now starting to emerge. Relatively little is known about the full assemblage of species that utilise the CRTD, and whether any of those species depend directly on the feature for their continued survival. Even less is known about the fate of species should the feature’s persistence be compromised with the prospect of global climate change. The detrimental effects of human activities, both land-based and at sea, on the biodiversity and ecosystem services that are supported by the CRTD are poorly understood, especially whether such effects are acute, chronic or reversible. This work aims to catalogue all available information on the physical and biological characteristics of the CRTD, with the intention to fill the knowledge gaps identified. In parallel, it intends to publicise the ecological and economic importance of the CRTD to Central American society, emphasising the trade-off in benefits between the two, and to devise a governance scheme that will rebalance that trade-off in favour of a sustainable future for both.