Sea Grasses

The three most commonly found indigenous sea grasses in Dominica are Thalassia testudinum, Syringodium filiforme and Halophila decipiens which is a bit more inconspicuous.

   
Left: a mixed stand of Syringodium (thin rounded leaves)
and Thalassia (blade-like leaves). Right: Halophila

Thalassia is more dominant along the northern and eastern coast of Dominica, generally in sheltered bays and back reef areas (e.g. Anse Soldat, Calibishie, Hodges Bay , and Middle Bay in Marigot). Although it mostly occurs in combination with Syringodium it may occasionally also form monospecific assemblages. Syringodium on the other hand dominates west coast sea grass habitats, often in combination with Halophila which intermittently dominates smaller patches, but can also form mono-specific assemblages (e.g. Lamothe)

While the fringing reef systems of the north coast provide well flushed, yet protected (turbulence) back reef areas conducive to shallow water (0-4 meters depth) sea grass beds, the west coast with its lack of near shore energy-dissipating structures is not the ideal place for shallow water sea grass beds. Instead, sea grasses along the west coast are generally found in waters from 4-18 meters. In theses "deeper" depths, self-shading by sea grasses with blade-like leaves (e.g. Thalassia) would be a disadvantage and so the species with round leaves, Syringodium, dominate the west coast. Thalassia can occasionally be found in small patches along the west coast in protected shallow areas such as Cachacrou.

Throughout Dominican waters, sea grass stands do not stand tall (20 cm) in comparison to other Caribbean locations, and are also not extremely wide. This is due to the narrow and steep shelf where light becomes a limiting factor within a few 100 meters (or less) from shore. Moreover, the shelf morphology offers no dissipation of physical disturbance from waves and storms which also limits the expansion of these plant communities. Dynamic changes in the overall dimensions and density of Dominica's sea grass beds are visible to anyone that snorkels regularly. Changes in these parameters occur throughout the year as a result of the chronic seasonal changes or acute storm impacts.

Given the fact that the island's underwater topography is not one that provides ample environments suitable for sea grass development, associated organisms like the queen conch, Strombus gigas, were never abundant and not a key component in the local fisheries. Such biological parameters shape the artisanal fisheries of each island, a fact often omitted in direct comparisons of the fisheries from different regions.

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