A decadal trend study (1998-2008) of POPs in marine sediments at the south of the Southern California Bight.

In this study we present a temporal analysis of two groups of persistent organic pollutants. We compare dichlorodiphenyltrichloroethane (DDT) collected in coastal sediment samples during 1998 and 2008 at the southern end of the Southern California Bight. Other group of organochlorine compounds (OCs) compared in this decadal analysis is the polychlorinated biphenyls (PCBs). For DDTs, the most abundant isomer was dichlorodiphenyldichloroethylene DDE followed by DDT. Although no statistically significant differences in total concentration were noticeable, composition-wise some differences were still observable. The fraction parameter FDDTe=p,p'-DDT/(p,p'-DDT+p,p'-DDE) used as a measure of freshness of DDT use, is utilized here to show changes in composition. These changes are due to natural degradation of p,p-DDT under mostly oxic conditions. These changes indicate a slow transformation of DDT residues to DDE. In addition, during 1998, several stations (12 stations) showed concentrations above Effect Range Low (ERL) for the sum of DDTs while only six showed exceedance during 2008. The number of extreme values was also less frequently found in 2008 samples. For PCBs, we detected statistically significant changes, however, in both years the most abundant congeners were mostly heavy congeners (>PCB # 77) which may indicate old residues. PCBs concentrations were found in very low concentrations and do not appear to represent a danger to ecosystems. Possible explanations are offered as to the lack of observable temporal changes in concentration for DDTs in this important region.

Trace metals in sediments and Zostera marina of San Ignacio and Ojo de Liebre lagoons in the central pacific coast of Baja California, Mexico.

San Ignacio and Ojo de Liebre lagoons in central Baja California, Mexico are nursery and grazing grounds for whales and turtles. Ojo de Liebre Lagoon also supports a salt mine operation. By concentrating trace metals via evaporation, this activity might harm biota. Consequently, salt mining might be incompatible with the lagoon's ecological role. Eelgrass can incorporate these elements and reroute them to other organisms. Trace metals in sediments (Cd, Co, Cu, Mn, Ni, Pb, Zn, and Fe) were measured at both lagoons. Some (Cu, Mn, Pb, and Zn) were also measured in Zostera marina patches at both lagoons. The results did not show elevated metal concentration at any lagoon, either for sediments or eelgrass. No statistically significant differences between lagoons were found. However, eelgrass at both lagoons showed larger concentration ranges than in sediments. Also, a correlation exists between sediment metal concentration and its concentration in eelgrass. Surprisingly, several sediment metal concentrations are higher than those considered as elevated for the Southern California Bight.