The Oceans Nursery:
A Lesson in Mangrove Ecology
TEXT BY DAVID VERNON 1999
By David Vernon: member of Belize Tourism Board, renowned guide and naturalist, founder and chairman of Placencia Town "Clean and Green" Committee, and owner of Toadal Adventures out of Placencia.
I've always had a love of nature and earth's natural wonders. As a child, I accompanied my father out to the islands for fishing. Camping for weeks at a time with friends, we explored the islands and waters surrounding them searching out wildlife. I can vividly recall so many sharks in one bay that one could practically walk across their backs to the other side. These times sparked my interest in nature.
Most of the islands in Belize are "built" by mangrove and support an incredible diversity of marine life. I say "built" because that's exactly what happens. The mangrove roots are on a continuous seaward quest, and in some cases grow more than 300 feet in a year. Building up land mass as they extend outward.
The most unique aspect of the mangrove plant is its ability to flourish in conditions where almost all other plant species perish. One of the basic survival needs of plants is water, fresh water. Yet if we water our plants too much they die. If they are watered with salt water they also die, as salt dries out their cells. Why then are mangroves able to live partially submerged in salt water? To answer the question lets first find out what mangrove really is. They are halophytes. Halophytes are plants that are able to tolerate and thrive in a salty environment. Mangrove is actually adaptable and can live on fresh water as well. 50 year old specimens, watered with fresh water and living on dry land, can be seen at the U.S. Botanical Garden in Washington D.C. These halophylic plants are found in tropical regions throughout the world. The Pacific boasts a higher species diversity (60 species), while only 12 species occur in the new world tropics. Four can be found in Belize, Rhizophora mangle (Red Mangrove), Avicennia germinans, Lagunicularia racimosa and conocarpus erecta.
As the Red Mangrove is a particularly important specie, lets focus on it. The roots of the mangrove hold key to its ability to live in a coastal/island marine environment. The roots are equipped with membranes that block eighty percent of the salt from entering into the plant. The twenty percent that enters is then excreted through the most dispensable part of the plant, the leaves. The plant produces waxy leaves that prevent excessive water loss through evaporation. The ability to shed and reproduce leaves is an important part of this process with an estimated 3 tons per acre per year of dropped leaves.
The tons of bio mass produced over the course of a year are the basis of an elaborate food chain. Within 24 hours of falling, these leaves are attacked by fungi and bacteria that are in turn eaten by a hungry host of tiny marine animals, mostly nematodes, marine worms and microscopic crustaceans, the copepods. Smaller fish feed on these microorganisms giving us the proverbial big fish eats little fish scenario.
Another interesting aspect of the roots is key to understanding the mangrove's role as a nursery for marine life low on the food chain. Mangrove resides in anaerobic soil conditions which means that if the roots were all under the soil like most other plants there would be no exchange of oxygen and gases because the base of the plant is usually under water. The plant overcomes this by sending out what are called prop roots which arch outward from the main stem in a tangled network both above and below the water line, and extend down below the soil level. These roots not only stabilize the plant but provide shelter for many marine animals. Fish, shrimps, sponges, seahorses, brittle stars, urchins, tunicates and crabs, to name a few, all call mangrove home. Some of these animals use the mangrove as shelter until reaching adulthood upon which they venture out into the open ocean. Others provide valuable food sources for animals higher up on the food chain.
In addition to marine animals, other above water life forms depend on the mangrove. It provides crucial habitat for birds, lizards, spiders and a myriad of other aquatic species.
Mangrove habitat is crucial for the health of the ocean and industries that depend on its abundant life. As more and more is being cut down and filled in for development projects, fish and shrimp farms and firewood, the ramifications are being most acutely felt in the fishing industry and tourism. The mangrove hatcheries restock the ocean schools and are popular attractions for tourists on nature tours.
Meet David Vernon
Born and raised in Placencia, Belize, David has returned to his native home after some years in the States and currently resides there with his wife Deb and baby. Child rearing and running their lovely little four room inn, Deb and Daves Last Resort and tour company Toadal Adventures, keeps them busy.
Dave has always had a love of nature. From fishing trips with his father out to the Cay islands to camping trips for weeks on end with his friends exploring the mangroves and islands near his home, it was ingrained from an early age. He accompanied his family to California as an adolescent, attended school, and was introduced to the outdoors of a whole new environment. During his years there, he spent much time hiking in the mountains and deserts and exploring the ecology of the southwest U.S.
Having had enough of life in the fast lane of the U.S., David moved back home to Placencia and rediscovered the beauty of Belize. He attended the first nationally licensed tour guide training courses and landed a job with one of the most respected tour operators in Belize. After guiding natural history tours for them for over 10 years, he decided to go out on his own and create Toadal Adventures, an active adventure tour company.
David is for the most part a self-taught naturalist. His true passion is researching any new question about nature that may arise, either in his extensive library or out in the field. Over the years he has accumulated a wealth of knowledge about the natural history and archeology of Belize and is considered by many to be one of the premier naturalist/guides in the country.
Teaching is another of David's interests. Through guiding, he found enjoyment in sharing his knowledge with people. Many tours he does are educational groups studying the reef or rainforest. The Tourism Board has recruited him to teach tour-guide training courses for guides in Placencia and other areas of the country.
From the time he returned to Placencia 15 years ago he has been very active in the community and other wide-reaching affairs. He has served two terms on the Village Council, formed and currently chairs the "Clean and Green" Committee and currently serves on the board of directors at the Belize Tourism Board. He is encouraged by the environmental efforts of Placencia and by the direction eco-tourism is being taken in Belize but there is always more to do.
Make a point of getting down to southern Belize and have David show you all there is to offer, and look for future contributions on manatees and other amazing wildlife indigenous to Belize.
Deb and Dave's Last Resort and
Point Placencia, Belize, Cent. Am.
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