Seagrasses meadows

Seagrass vegetation provides a number of services to the overall functioning of the coastal zone: (1) Seagrass meadows are known to enhance the biodiversity and habitat diversity of coastal waters. (2) They provide nursery habitat and foraging areas for a large number of commercially highly important fish and shellfish species. (3) Seagrasses play an important role in improving water quality by reducing the particle loads in the water and absorbing dissolved nutrients. (4) They are known to stabilise sediments, by reducing sediment resuspension, and dissipating wave energy before it reaches the shore. Seagrasses also develop a complex web of roots that bind the sediment and stabilises it thus acting as coastal defences. (5) Seagrasses meadows play a significant role in global carbon and nutrient cycling.

Over the last decade, eutrophication has arisen as one of the main threat to seagrasses meadows. Rapid population growth, increased tourism pressure together with the massive use of fertilisers ?e.g. golf courses - has led to the exponential rise in nutrient load to coastal zone. As nutrient inputs increase, microalgae and macroalgae proliferate, and carpets of epiphytes develop on their leaves, reducing the amount of light penetrating through the water column and being available to seagrasses for photosynthesis. Eutrophication also typically leads to reduced conditions in the sediment, anoxia of bottom waters and an increase in nutrient concentrations to potentially toxic levels. High soil erosion rates associated with changes in land use and clearing of land to provide new hotels and associated facilities and accommodate increasing numbers of tourists, have led to an increase in sediment transport. The increased silt transport results in a deterioration of the underwater light climate for seagrasses and partial burial of the plants.
Spaanse Water, Curaçao, is the second largest inner bay, with an area of 3.19 km2 and a mean depth of 5 m. The bay contains the largest seagrass areas (as well as algal and mangrove) of the Curaçao Underwater Park. It has also been identified as a priority area for conservation. However, seagrass meadows within Spaanse Water are threatened by increasing tourism development. The entire northern coastline of the bay has deforested in order to make place for tourist developments. Untreated waste, which is discharged into the bay and increased sedimentation present a serious threat to the fringing seagrasses meadows.

Dredging for the maintenance of shipping channels such as those associated with tourist marinas will have a direct mechanical impact on seagrass meadows, though losses may be small relative to damage due to increased water turbidity. Where small boat are numerous, the cumulative effect of boat moorings and propeller scars may result in considerable loss of vegetation.