This is stop #3.
The Indian River Lagoon is a biodiverse estuary, home to over 4,000 species. Biodiversity is a measure of how healthy ecosystems are and is assessed by counting the number of species present in an area over time. Many factors contribute to biodiversity.
Look over the railings on either side of the boardwalk and down into the water through the mysterious arches created by red mangrove prop roots.
Now these old mosquito control ditches are sheltered from the variable weather conditions found on the open lagoon and are a good example of a transitional zone habitat where the land and water meet.
Now look closely at the mangrove roots or branches. Can you find a mangrove tree crab? These crabs are small and brown, camouflaged to match the bark of mangrove trees. They sense vibrations with hairs on bodies and will quickly sneak behind a root or trunk if they pick up new noises in their habitat.
They use the mangrove roots as crab superhighways; climbing up and down the roots and trunks, feeding on mangrove leaves and insects and wetting their gills. Mangrove tree crabs are omnivores; they eat animals and plants. They are unusual because they eat living mangrove leaves which most animals find difficult to digest.
When the water is high, the crabs climb high into the trees to avoid aquatic predators like fish and blue crabs. When the water is low they climb down over the detritus (that’s nutrient rich mud) to forage and to wet their gills in the moist soil. Mangrove tree crabs must be careful when climbing up into the trees because they are also tasty morsels for raccoons or birds, such as the yellow crowned night heron.