Project Description

Southwestern Puerto Rico contains a diversity of coastal habitats that provide multiple services to the environment and humans. The area contains functionally interconnected habitats such as coral reefs, mangrove forests and vast seagrass beds. The latter provide nourishment and protection for listed endangered species, such as manatee (Tricheccus manatus) and hawksbill turtles (Chelonia midas), as well as other keystone species. In addition, seagrass beds serve humans as important areas for fisheries, tourism and recreational activities. During recent years, there has been a significant increase in recreational boat traffic, especially on weekends and holidays when hundreds of boaters are apparent along the southwestern coast of Puerto Rico.

The recent boom in tourism/recreational activities has resulted in impacts to benthic habitats especially seagrass beds, which thrive in shallower water. Impacts take the form of mechanical disturbance to shallow seagrass beds due to anchoring, accidental grounding of boats and/or propeller plowing (scarring). Over time, these disturbances can be responsible for:

Increments in segregation that alter the distribution or diversity of benthic communities
Increased erosion and concomitant decreases in seagrass coverage
Changes in ecosystem nutrient management (potential population increases in macro- and epiphytic algae)
Detrimental impacts to critical habitat

Objectives

• Identify the intensity of impacts of boat traffic and priorities for management
• Provide a baseline in terms of the level of damage in specific seagrass beds for assessment of scar progression or healing of seagrass communities
• Estimate anthropogenic disturbance to seagrass beds that can be used by regulatory agencies in support of mitigation and management efforts
• Enhance existing GIS coverage and create new maps
• Serve as a model for quantifying anthropogenic impacts to seagrass beds and verifying (sea-truthing) seagrass extension

Study Area

Two field sites were selected, La Parguera and Guánica Natural Reserves, which are within the Southwest Special Planning Area (SSPA) of Puerto Rico. The area around Guilligan's Island in Guánica was selected for study because it is a popular tourist area that is managed to prevent boater encroachment into the shallows and project the seagrass beds, mangroves, and coral key while still allowing people to enjoy swimming, snorkeling, and picnicking on the island. In La Parguera, areas to concentrate field investigations were selected from the overflight based on visible evidence of scarring. These areas were mainly the coral keys closest to shore, namely Carcoles, Collao, La Gata, and Enrique, the entrances to Playita Rosada and Papayo, and the entrances to the area's two bioluminescent bays on the eastern and western sides of the reserve.

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