Page 56 - SOUTH GUANACASTE TOURIST GUIDE

Diving in Guanacaste
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The Islas Catalinas, with their ghostly manta rays that congregate from January to April, and the Islas Murciélagos, populated by bull sharks, remain the two most famous long-range dive sites in Guanacaste. However, many sites are located much closer: Punta Gorda, Bajo Tiburones, Virador and Los Meros are all about 10 kilometers offshore, and a 20-25 minute boat ride, a fairly short trip in dive circles.
What is the Dome? Where is it located?
The Costa Rica Thermal Dome (CRTD) is a unique oceanographic phenomenon, formed by the interaction of wind and ocean currents, and results in the upwelling of nutrient-rich deep waters, resulting in higher levels of biomass than in the surrounding tropical waters and making it one of the most productive area in the northeastern tropical Pacific.
It is located to the west of Central America and can measure between 300 and 1000 kilometers wide. The average position of the Dome core is near 9° N and 90° W, in areas outside national jurisdictions. Its diameter and position vary from year to year and over a characteristic annual cycle (Fiedler, 2002).
This oceanographic phenomenon results from the action of winds and ocean currents that vertically displace deep, cold, nutrient-rich waters towards the surface, creating an upwelling zone.
This upwelling mobilizes an enormous mass of water (about 3.5 million m3/s) to the surface.
The cold water mass is located close to 15 meters from the surface, but is much deeper around the CRTD. As they approach the surface, the nutrients in the cold water mass combine with sunlight to produce a large algae growth.
The greater presence of algae, the first step in the food chain, leads to greater food availability for zooplankton, causing a population explosion. This, in turn, is manifested in each link of the food chain, generating an oasis of resources in the sea.
Due to its high productivity, the CRTD is considered an important habitat for several species. The high presence of phytoplankton also leads to an abundance of zooplankton (1), euphausiids (krill) (2), and small squid, which form the basis of several food chains that are essential for migratory species that benefit from the Dome at various stages of their life cycles. These include manta rays, turtles, dolphins and whales, as well as marine predators including large pelagic fish such as billfishes and sharks. Finally, the area also attracts commercially valuable species such as tuna, mahi mahi and squid. Endangered
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