By: The Cayman Islands Department of Environment

The shallow, warm, crystal clear waters surrounding the Cayman Islands have provided us with one of nature's most spectacular marine ecosystems. The marine environment has always been important to the people of the Cayman Islands. The sea has been utilised for food, building materials, medicines and decorative objects, and, even to this day, provides some of the basic needs for the residents of our Islands. The marine environment also makes a major contribution to the economy through tourism and fisheries, and plays a critical role in shore protection. However, the economic and ecological importance of this environment is often undervalued.

Cayman's marine environment is a truly remarkable ecosystem. Although often thought of as separate ecosystems the coral reefs, seagrass beds and mangrove wetlands that make up the marine environment are in fact a single extremely tightly integrated system depending heavily on each of the components within it. Such close integration and the finely balanced nature of the marine environment mean that changes in one area, such as seagrass beds can have far reaching 'knock-on' effects in the other areas.

Mangroves
Mangrove wetlands form an important link between the terrestrial and marine environment. In Cayman three types of mangroves typically dominate forests: red, black and white mangroves, each of which has evolved unique characteristics to tolerate levels of salt, and lack of oxygen that would normally kill other plants.

White mangroves live furthest inland, secreting the salt they absorb from the waterlogged soil out through special "glands" at the base of their leaves. Black mangroves are able to live closer to the water making use of special roots that grow up vertically above the ground. These roots act like snorkels that allow the tree to absorb oxygen from the air when the ground is completely awash with salt water or soil is low on oxygen. Red mangroves are the best adapted for living in salt water and can be found at the most seaward margin, often actually growing in the water. The aerial prop roots of red mangroves give the impression of a tree on legs, which allow the tree to literally stand in the water.

Mangroves provide many important functions vital to the health of Cayman's marine environment, including providing an ideal habitat for birds, fish and a myriad of different invertebrate species. Cayman's parrots love to nest in the hollow trunk of dead black mangrove trees. Fish make their homes amongst the tangled roots of red mangroves, hiding from larger fish and feeding on smaller fish and creatures that also make their homes in the tree roots. Invertebrates such as the mangrove oyster, crabs, snails and shrimp actually make their homes on the submerged mangrove trees and roots, making these areas a spectacularly diverse and colourful environment for snorkelling.

In addition to the habitat they provide mangrove wetlands perform numerous other essential functions. The dense and extremely strong root systems form a perfect protection barrier against the large waves and storm surges that Cayman can experience during hurricanes and other storms. On a day to day basis the roots help to stabilise muddy and soft sediments that would be stirred up by wave activity causing shoreline erosion and murky waters devoid of marine life. Mangrove wetlands also act like large sponges absorbing large quantities of fresh water from heavy rains and releasing it slowly and harmlessly into the marine environment. Mangrove ecosystems are also important providers of nutrients that feed into surrounding ecosystems thereby making them healthier and more productive.

Seagrass beds
Moving seaward from the mangroves we typically find seagrass beds. Seagrasses are actually flowering plants that live in the water. In Cayman there are at least four different species of seagrasses although the most common is turtle grass. Turtle grass, which gets its name due to the fact that it is an important source of food for green turtles, is easy to identify with its broad flat green blades that make up lush meadows growing over the sea floor.

Turtle grass beds are an important component of the Cayman's marine environment. Like their relatives on land, seagrass root systems are able to bind loose sediments together and therefore prevent erosion of the sea floor. The wide flat blades of the turtle grass also dampen wave action and encourage silts suspended in the water to settle out more quickly, creating much clearer water. If not for healthy turtle grass beds many of our beautiful lagoons might not be as crystal clear as they are today.

Seagrass beds are also home to a huge diversity of marine life. Snails, juvenile fish, crabs, shrimp, juvenile lobsters and many other invertebrates live amongst the grass fronds or can be found buried in the silt held in place by the grass' root system. With their abundant supply of resources turtle grass beds are ideal feeding grounds for adult lobsters, large fish and green turtles. Indeed, some scientists consider healthy turtle grass beds to be the most productive marine ecosystems on the planet.

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