The coral reef at Parque Nacional Cahuita, Limón, Costa Rica, is a reef under stress due to siltation. The amount of suspended sediments is high and resuspension of bottom sediments is also high. Growth rates of corals, live coral coverage and diversity were low. Colonies are generally larger than in other areas studied, and recruitment of planulae seems to be low. Most of the corals present are good at rejecting sediments and morphologies of some change to better resist the sediments (vertical fronds of Agaricia agaricites) or to receive more light (shingles of Montastrea annularis and Porites astreoides).

Analyses of the currents and the type of minerals present in the noncarbonate fraction of the sediments at the reef point to Río La Estrella as the source of sediments. The amount of sediments carried by this river has probably increased recently as a result of watershed deforestation. The problem of siltation in reef environments is bound to increase as new areas in the tropics are being developed.

Sediments affect both the individual coral and the coral community. Whether a reef is (or was) under stress due to siltation, can be determined by analyzing the following: growth rates of the corals, amount of trapped sediments in the skeletons, live coral coverage, species composition and diversity, and morphologies.