Middleton, J.

Runoff and sewage discharge present serious consequences if left unchecked in coral reef ecosystems. Eutrophication and the introduction of harmful chemicals to the environment can lead to the destruction of coral reefs. Phosphates and polycyclic aromatic hydrocarbons (PAHs) are well known components of runoff that are detrimental to the reef ecosystem. As such, the ability to monitor the concentration and spatial distribution of these chemicals is of great interest. These pollutants may be detected using bioindicators. Bioindicators are organisms that can be used to monitor the health of an ecosystem. In this study, sponges were assessed as bioindicators for phosphate and PAHs in coral reef environments. Holopsamma helwigi, Ircinia strobilina, and Pseudoceratina crassa are common Leuconoid sponges that were tested for pollutant contaminations using fluorometric analysis. The sponges were collected along a transect spanning the northern coast of Kralendijk, Bonaire. A known runoff site at ‘Kas di Arte’ (12° 9' 19.9362" N, 68° 16' 44.5434" W) was selected as the starting point for the transect. The sponges bioaccumulated both phosphates and PAH compounds. Concentrations of the pollutants were not found to decrease as the distance from the runoff site increased suggesting that sponges assessed here are not capable of showing short-term variation in spatial trends of pollutant concentration. In order to better understand how the sponges accumulate pollutants, a thorough exploration of the kinetics of pollution bioaccumulation should be pursued in future studies.

This student research was retrieved from Physis: Journal of Marine Science XV (Spring 2014)19: 45-51 from CIEE Bonaire.

Abstract

The effect of recreational SCUBA diving on coral reefs is likely secondary to many of the commonly cited stressors that threaten the long-term survival of coral reefs, such as rising temperatures. However, recreational SCUBA diving has had documented effects on various benthic organisms. Most research on the effect of SCUBA divers has focused on broken and abraded benthic organisms or the rate at which divers contact the benthos. We tested for differences in the structural complexity and benthic assemblage between pairs of heavily and lightly trafficked dive sites in Bonaire, a popular Carribbean diving destination. There was roughly 10 % less structural complexity in areas of heavy traffic. This is alarming given that the structural complexity of shallow reefs in Bonaire is substantially lower than in the 1970s. Different functional groups of benthic organisms were affected differentially by diving traffic. For instance, massive corals such as Orbicella annularis were 31 % less abundant at heavy than light diver traffic areas, while gorgonians and sponges had similar abundances at heavy and light diver traffic areas. Our results match those of previous studies on the resistance and resilience of tropical benthic reef organisms to physical disturbances that suggest that stony corals are more prone to physical damage than gorgonians and sponges. We provide a number of possible management strategies that could reduce the effects of recreational SCUBA divers on Bonaire and elsewhere, including education/intervention by dive guides and concentration of diving traffic away from areas of stony coral abundance.