Spanning seagrass meadows, swaying with crash of the waves, provide an ideal nearshore environment for animal and plants alike. In fact, seagrass meadows are often under appreciated, but are key in anchoring sand and dissipating wave energy, both vital in protecting Bonaire’s delicate sandy beaches. In addition, seagrass provides vital habitat and feeding grounds while also working to filter the water, improving overall water quality for all of its inhabitants.
Seagrass beds are often found alongside coral reefs. Although they are much less charismatic and frequently overlooked, seagrass beds play a vital role in maintaining the health and diversity of adjacent coral reefs.
Seagrasses are not one but 50 species of flowering marine plants which usually form dense stands in the shallow, sandy bottom environments of back reef lagoons and semi-enclosed bays. They are bright sunlit fields of waving green fronds and are the favoured habitat of the globally endangered Green Turtle (Chelonia mydas) and Queen Conch (Lobatus gigas). Other common inhabitants are cushion stars, urchins and sea cucumbers. Scientists have found over 113 species of algae (marine plant) growing on seagrass leaves, not to mention sponges, hydroids, flatworms and tunicates.
Here on Bonaire we have four native seagrasses turtle grass (Thalassia testudinum), manatee grass (Syringodium filiforme), shoal grass (Halodule wrightii) and ditch grass (Ruppia maritima). In addition, since 2010, an invasive species from the Res Sea, Halophila stipulacea has been identified and spreading.
Similar to mangroves systems, seagrass beds provide an ideal hiding place for the young of many species of reef fish and other marine life. The queen conch (Lobatus gigas) hide for the first year of their life in the sand surrounding seagrass beds before emerging to forage and live. Adult parrotfish (Scaridae), surgeonfish (Acanthuridae) and porgies (Sparidae) are also frequent visitors, migrating into seagrass environments to feed.
Seagrasses thrive in sunlight rich waters, making water clarity vital to their survival. Pollution and over sedimentation can block sunlight, causing large areas of seagrass to dieback. Additionally, smothering by large influzes of sargassum as well as the deteriorated water conditions if sargassum is left to rot can not only wipe out seagrass, but all of its inhabitating populations.
One of the most remarkable things about seagrasses is their ability to spread and grow by sending out underground rhizomes (roots). It is also their greatest weakness as it makes them phenomenally vulnerable to trampling and physical damage. Protecting seagrasses not only means improving water quality but physical damage by respecting these fields and not walking through them.