Science Advisory Report 2009/002
Contaminant monitoring in the Gully marine protected area
- Known sources of contaminants for the Gully MPA include dry and wet atmospheric precipitation, transport of river-borne contaminants via coastal currents, transport of contaminants from oceanic waters via shelf edge water exchange, and more localized sources including the offshore oil and gas developments on Sable Bank and marine shipping.
- Some temporal trends in contaminants of relevance to the Gully MPA have been detected. For example, decreasing trends in PCB and DDT concentrations have been observed in Sable Island seals, which may spend some of their time in the Gully. However, samples from northern bottlenose whales that spend much of their time in the Gully indicated an increase in 4,4’-DDE and trans-nonachlor from 1996 to 2003. Decreasing trends in dissolved lead and zinc are evident across the Eastern Scotian Shelf, and large floating debris appears to have decreased over time in the Gully. However, no decreasing trend was seen in dissolved copper or smaller plastic debris.
- Dissolved metals measured in the Gully MPA are similar to these measured elsewhere on the Scotian Shelf. Chromium, copper, iron, vanadium and zinc in sediments of the Gully area show patterns that are indicative of natural concentrations. A small subset of samples has shown elevated levels of barium and lead.
- Aromatic hydrocarbons were not detected in sediment samples collected from feeder canyons to the Gully MPA in 2006, but the samples did contain total alkanes (C10-C35) at low concentrations. The source of these alkanes is unknown, though observations based on the analysis of individual alkanes suggests both biogenic and anthropogenic sources are possible. A small sample of Gully krill contained pristane but no other detectable alkanes and very low concentrations of alkylated and parental PAHs. Measurements of CYP1A1 protein expression in northern bottlenose whales indicated increased levels in 2003, which may be an indication of exposure to hydrocarbon contamination.
- Higher concentrations of a number of organochlorine compounds were observed in northern bottlenose whales from the Gully than in a population from the northern Labrador Shelf.
- Future contaminant monitoring within the Gully ecosystem should include: continuation of existing time series to establish long-term temporal trends, expanded sampling and analysis of Gully sediments to establish spatial patterns, and opportunistic sampling/analysis of relevant indicator species to determine contaminant levels and investigate potential biological effects. This monitoring should be conducted in conjunction with targeted research to better understand the ecosystem dynamics of the Gully, including geological and oceanographic processes.
- Potential indicator species for monitoring of contaminants and their biological effects in the Gully include flounder, snow crab, squid, krill/shrimp, corals and bottlenose whales. However, additional research is required to determine the feasibility of using any of these species for contaminant monitoring in the MPA and the potential usefulness of the results for management.
- There are a number of sources of uncertainty to be taken into account when considering the recommendations provided within this report. Only a small number of water, sediment and biota samples have been collected from the Gully MPA, and only a very limited analysis of the dynamics of the system has been conducted to date. Given the limited amount of site-specific data, observations made elsewhere on the Scotian Shelf have been used to provide context for the Gully MPA.
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