Chemical contamination assessment in mangrove-lined Caribbean coastal systems using the oyster Crassostrea rhizophorae as biomonitor species

This paper aims to contribute to the use of mangrove cupped oyster, Crassostrea rhizophorae, as a biomonitor species for chemical contamination assessment in mangrove-lined Caribbean coastal systems. Sampling was carried out in eight localities (three in Nicaragua and five in Colombia) with different types and levels of contamination. Oysters were collected during the rainy and dry seasons of 2012–2013 and the tissue concentrations of metals, polycyclic aromatic hydrocarbons (PAHs), and persistent organic pollutants (POPs) were determined. Low tissue concentrations of metals (except Hg) and PAHs; moderate-to-high tissue concentrations of Hg, hexachlorocyclohexanes (HCHs), and dichlorodiphenyl-trichloroethanes (DDTs); detectable levels of chlorpyrifos, polychlorinated biphenyls (PCBs) (mainly CB28, CB118, CB138 and CB 153) and brominated diphenyl ethers 85 (BDE85); and negligible levels of musks were recorded in Nicaraguan oysters. A distinct profile of POPs was identified in Colombia, where the tissue concentrations of PCBs and synthetic musk fragrances were low to moderate, and Ag, As, Cd, Pb, and PAHs ranged from moderate to extremely high. Overall, the values recorded for HCHs, DDTs and PCBs in Nicaraguan mangrove cupped oysters greatly exceeded the reference values in tissues of C. rhizophorae from the Wider Caribbean Region, whereas only the levels of PCBs were occasionally surpassed in Colombia. Different contaminant profiles were distinguished between oysters from Nicaragua and Colombia in radar plots constructed using the main groups of contaminants (metals, PAHs, musks, PCBs, and organochlorine pesticides (OCPs)). Likewise, integrated pollution indices revealed differences in the levels of contaminants. Moreover, the profiles and levels in oyster tissues also varied with season. Thus, principal component analysis clearly discriminated Nicaraguan and Colombian localities and, especially in Colombia, seasonal trends in chemical contamination and differences amongst localities were evidenced. The geographical and environmental disparity of the studied scenarios may represent to a large extent the diversity of mangrove-lined Caribbean coastal systems and therefore the present results support the use of C. rhizophorae as suitable biomonitor species at Caribbean regional scale, where seasonal variability is a major factor controlling pollutant mobility and bioavailability

Bonaire and Curacao

Bonaire and Curacao are oceanic islands surrounded by coral reefs on their leeward sides extending steeply down to mesophotic depths (30-150 m). Easy access from shore, as well as the geopolitical context of the two islands, has made the mesophotic coral ecosystems (MCEs) of Bonaire and Curacao among the most well studied in the world. MCE research has been conducted in the region since the 1970s, and ongoing research employs state-of-the-art exploration technologies such as manned submersibles, autonomous underwater vehicles, and mixed-gas, rebreather technology. Mesophotic coral communities in Bonaire and Curacao are typically dominated by agariciids, with Agaricia lamarcki and A. grahamae covering a substantial proportion of the substrate at upper mesophotic depths (30-60 m), while the lower meso-photic (>60 m) consists predominantly of A. grahamae and A. undata. Although much of the habitat is dominated by sediment with only patchy coral growth, in some locations coral assemblages can cover up to 100% of the sea-floor down to depths of 70-85 m. Recent biodiversity studies, mostly focusing on fishes, sponges, and corals, documented only limited overlap between shallow and mesophotic reef communities, and that MCE biodiversity is strongly structured by depth. Since MCEs in Bonaire and Curacao harbor highly specialized communities facing specific threats deriving from their proximity to urbanized land, these ecosystems warrant new management policies and conservation measures. These measures should protect the whole extent of these reefs, which rank among the healthiest in the Caribbean region