Funded by NOAA’s Coral Reef Conservation Program (CRCP), the goal of this project is to quantify the extent of chemical contamination in sediments and fish in Cocos Lagoon, Guam. Significant chemical contaminant issues have been identified in the area of Cocos Island, as a result of past land use activities. The project is providing an assessment of the spatial distribution of a suite of both organic and inorganic chemical contaminants in sediments, as well as contaminant body burdens in fish
Why We Care
Cocos Lagoon (Figure 1) is an atoll-like coral reef lagoon located on the southwestern coast of the island of Guam. The lagoon is separated from the open ocean by a series of fringing reefs and barrier islands, of which Cocos Island is the largest. Cocos Lagoon is a popular area for recreational activities including fishing, boating and diving, along with subsistence fishing.
Between 1944 and 1963, the US Coast Guard (USCG) operated a Long Range Navigation (LORAN) station on Cocos Island. Components from the LORAN station, including several transformers and capacitors containing polychlorinated biphenyls (PCBs), likely used in the operation of the station were found on land and in nearby waters. The Coast Guard has since removed the PCB containing transformers and capacitors, along with a substantial amount of contaminated soil, but there is evidence that these chemicals have migrated into several marine matrices including fish and nearshore sediments, which is of concern to local managers and to the public. Exposure to PCBs have been found to elicit a range of toxic responses in animal studies including reduced growth, reproductive impairment and vertebral abnormalities, and PCBs have been shown to cause cancer in animals. A fish consumption advisory was put in place in Cocos Lagoon in 2006, following detection of PCBs in fish through USCG-funded research. In 2015, local resource managers asked NCCOS for help in assessing chemical contaminants in sediments and fish to understand the extent of the contamination throughout Cocos Lagoon.
The analysis of samples from Cocos Lagoon is being conducted through the National Status and Trends (NS&T) Program. Since 1984, NOAA has maintained the NS&T Program, a nationwide long-term monitoring program that measures the spatial distribution, temporal (historical) trends, and effects of chemical contamination in US coastal waters. The NS&T Program is located within NOAA’s National Centers for Coastal Ocean Science, Center for Coastal Monitoring and Assessment. Results from the work in Cocos Lagoon will be compared with other data collected from the Nation’s coastal areas over the last 30 years, and with established guidelines.
For this project, we worked closely with the Guam Environmental Protection Agency, Guam Department of Agriculture, the University of Guam, and a local fisher, to design the sampling strategy and collect the samples from Cocos Lagoon. We also worked with NOAA National Marine Fisheries Service (NMFS) and CRCP scientists on Guam, in the planning and in the field effort. In addition to working with the partners in the design of the project, Guam EPA provided vessels and personnel for the fieldwork.
What We Did
For this project, we collected sediment samples (25 total) and eight species of fish (27 total) representative of those that are locally eaten. Fish were collected using a cast net (Figure 2) or hook and line. Sediment and fish tissue (whole fish) samples were analyzed for approximately 190 chemical contaminants, including 83 PCBs, petroleum hydrocarbons, heavy metals and several pesticides such as DDT (dichlorodiphenyltrichloethane). The contaminant analysis protocols were developed by NOAA’s NS&T Program, and have been used to monitor the health of the nation’s coastal waters for 30 years. Concentrations of chemical contaminants detected in sediments were compared to NOAA sediment quality guidelines. Concentrations of contaminants in the fish were compared with human health screening values (SV) developed by the USEPA. Risk as defined by the USEPA is one excess cancer case per 100,000 individuals that results from consumption of fish contaminated with PCBs over a 70-year lifetime. When SV are exceeded, more intensive site-specific studies are needed. Subsistence fisher SV are lower than recreational fishers. Subsistence fishers consume fish at a higher rate, and therefore would potentially accumulate higher amounts of the PCBs over time
What We Found
Sediments. Concentrations of chemical contaminants in sediments were low. One sediment sample near Cocos Island slightly exceeded a sediment quality guideline established by NOAA for the banned pesticide DDT. The sediments that occur throughout most of Cocos Lagoon consist of sand and coral gravel, which do not readily accumulate chemical contaminants.
Fish. Concentrations of total PCBs (sum of the 83 PCBs measured) were above EPA SV for some of the fish caught in Cocos Lagoon (Figure 3). Total PCB concentrations were above the EPA recreational SV in four species (banded sergeant, blackspot sergeant, convict tang, honeycomb grouper, and orange-striped emperor) from around Cocos Island. No fish from other locations were above the recreational PCB screening values. Four honeycomb groupers caught in other parts of Cocos Lagoon were above the recreational SV (Figure 3). DDT was found at concentrations above the recreational fisher SV for two fish species, and above the subsistence SV for four other species around Cocos Island. No fish from any other areas of Cocos Lagoon were above either SV for DDT. No other chemical contaminants analyzed for this project were above available USEPA SV.
NOAA will continue data analysis, working with Guam EPA, the USEPA, and the USCG. The USEPA has indicated that they will conduct further human health risk assessments using the NOAA data. A technical report on the results from the collection and analysis of sediments and fish is currently being developed by NOAA and will be ready in late 2017.
Preliminary approval has been received for an effort to look for PCBs in the water column around Cocos Island, using a series of passive water samplers. Sediments are typically a reservoir for many chemical contaminants that can accumulate in aquatic organisms, however, the sediments collected in Cocos Lagoon, including from around Cocos Island, contained very low levels of PCBs and other contaminants Because of this, sediments may not be the only source or medium through which contaminants are accumulating in the fish.
One possibility is that chemical contaminants like PCBs are being transported via water from Cocos Island (e.g., through surface water runoff or groundwater inputs) and then subsequently taken up by the fish. It is also possible that the fish are accumulating contaminants through the food chain, through the sediments or perhaps a combination of all three sources. To assess the possibility that the water column may be an important source of PCBs and other contaminants in the fish found adjacent to Cocos Island, NOAA in partnership with the USEPA and Guam EPA, is planning to deploy an array of passive water samplers known as PEDs or polyethylene devices, adjacent to Cocos Island, in mid to late summer of 2017.