Costa Rica Thermal Dome Adventure and the need for a strong High Seas Treaty

Date: 22nd June 2021

Author: Milla Heckler

In the Eastern Tropical Pacific, off the coast of Central America, there is a phenomenon that is persistent enough from year to year to be considered an oceanographic feature – it is referred to as the Costa Rica Thermal Dome and  is an incredible marine biodiversity hotspot. Due to its high levels of biodiversity, the Dome is ripe for scientific discoveries and learning. 

Credit: Milla Heckler

This oceanographic phenomenon can be found straddling Central American countries’ EEZs and  the high seas. The thermal dome is the result of wind and different ocean currents interacting with each other to  produce the vertical displacement of deep, cold, nutrient rich waters that approach the surface and create an upwelling system. The cycling and mixing of deep cold water and hot surface water create perfect conditions for phytoplankton and algae, both crucial species for biodiversity in the oceans. More algae means more food available for zooplankton, resulting in an explosion of zooplankton biomass, which is in turn manifested in each subsequent link of the food chain. The high productivity of the Dome makes it a distinct habitat and a biodiversity rich ocean oasis. 

Credit: Milla Heckler

As a young woman with big dreams of becoming a marine biologist and exploring the uncharted alien world under the sea, I got the chance to visit the Costa Rican Thermal Dome in April 2021. I was lucky enough to be invited on a youth research expedition with a wonderful organization called Fins Attached. The expedition was such an exciting trip because of the high primary productivity of the area. The Dome is a special place because of its importance to marine biodiversity in the Eastern Tropical Pacific and socioeconomic dynamics in the neighboring countries. I was able to dive with core emblematic species, including cetaceans, sharks, rays, turtles, pelagic fish, and seabirds. In addition, it was also very special to be in a place I know plays such a large role in carbon sequestration. 

During the research expedition, we made sure to take advantage of the magical and rare biodiversity of the Dome. We used acoustic tags to tag sharks, manta rays, and turtles to learn more about their migration patterns. More specifically we tagged 6 leatherback sea turtles, 4 white tip reef sharks, 5 smaller species of manta rays named M. alfredi, and 2 of the larger species named M. birostris. The Dome is a great place to tag animals because many migratory species use it as a staging post during their long journeys across the ocean, highlighting the interconnectivity of the high seas and coastal ecosystems. Using tags we are able to track the migration patterns of species. We can then bring this evidence to politicians to demonstrate where species live and the best locations for marine protected areas. 

Credit: Milla Heckler

During the expedition I was diving at least 3 times a day. I got to see many unique species, notably the puffer fish and barracuda. I was unable to see the endangered hammerhead shark and the vulnerable thresher shark due to their low population numbers from being overfished and regularly caught as bycatch. However, I made sure that while I was under the water I appreciated and took in every last second of the magic before my eyes, knowing that it could all disappear in the next couple decades if no action is taken. 

Due to the Dome’s high productivity and species richness, multiple industries and activities have developed in the region, such as commercial and recreational fishing, and wildlife-based tourism. Unfortunately, we live in a time where we cannot expect the natural beauty that we see to last forever – and the Costa Rica Thermal Dome is no exception. We need the proper legal and governance frameworks in order to conserve and sustainably use the ocean and its resources. Since parts of the Dome can be found in the high seas, the new High Seas Treaty offers an avenue to protect this critical ecosystem and its integral role in supporting key ocean species. 

Credit: Milla Heckler

The high seas area of the Dome extends over 530,000 km2 and is a breeding, feeding, and transit site for multiple species of ecological and commercial value. It is important to note that the high seas area of the Dome is often unaccounted for, with no legal framework to create marine protected areas (and a new High Seas Treaty would change this!). The Dome harbors five of the 7 known turtle species in the world, including the emblematic leatherback. The leatherbacks travel from Central to South America yearly, regularly moving from the high seas into coastal waters and back. The leatherbacks do not follow the artificial boundaries created by humans, as with many other migratory species. This is extremely important for two reasons: (i) it demonstrates the connectivity of coastal areas to the high seas and vice versa; and, (ii) in order to protect leatherbacks and other species that regularly move between the high seas and coastal waters, you need equal protections within both areas, i.e. measures to prevent the bycatch of leatherbacks won’t be successful if they aren’t applied to areas in the high seas. This is the same for many other ocean species, and years of studying the migration patterns of animals show that we must focus our attention to the entirety of the ocean, the high seas included. This is why we need a new High Seas Treaty. We cannot forget about sixty-four percent of the ocean. 

Credit: Milla Heckler

A robust High Seas Treaty can set up a win-win-win scenario for the ocean: we can responsibly protect and conserve high seas biodiversity, the benefits from which will  help us combat food insecurity and grow our blue economy. . Furthermore, better protection and management helps us leverage the power of a healthy ocean to fight the climate crisis.

Biodiverse ecosystems are being destroyed by human activities every day. We must return to our roots and repair our bond with nature. We have forgotten that Earth is one large organism and we must all work together to keep it healthy. If one thing fails, everything goes down with it. Let us remember the beauty that our planet holds and the complete gem it is in our vast solar system.

 Let’s transform the way we manage the ocean and the high seas by adopting a robust and ambitious high seas treaty as soon as possible. Not just for the turtles and sharks , but for our own survival.

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