Proceedings of the 2007 Georgia Basin Puget Sound Research Conference
Session 3E: Seafood Safety and Human Health II
Chair: Vera Trainer
A Public Health Approach to Low Dissolved Oxygen in Hood Canal
Hood Canal in Puget Sound has a history of low dissolved oxygen and anecdotal information suggests periodic fish kills dating back to the early 1900s. Recent oxygen levels are the lowest in recorded history, resulting in fish kills in 2002, 2003 and 2006 and prompting concerns about long-term health of the canal.
A “Preliminary Assessment and Corrective Action Plan”, (PSAT, May 2004) (PACA) theorized nutrient contamination as a source of the dissolved oxygen problem because excess nutrients stimulate algal growth, which uses oxygen as it breaks down. The PACA used mathematical estimates to identify nitrogen from onsite sewage systems (OSS) as the major anthropogenic source to Hood Canal.
The Kitsap County Health District conducted a fecal coliform Pollution Identification and Correction project in 2005 to: protect public health by correcting failing OSS; assess the relationship between FC and nitrate+nitrite nitrogen in fresh water drainages, and determine net nutrient reductions after correcting failing OSS.
Twelve failing OSS were identified and corrected in nine miles of shoreline comprising 340 residences (4% failure rate). No statistical correlation between FC and nitrate+nitrite nitrogen was found. Shoreline flows demonstrated statistically significant nitrate+nitrite nitrogen reduction after correction at two OSS correction sites.
Tracking Bacteria Sources in Oakland Bay
Oakland Bay is located at the south end of Puget Sound. A very productive shellfish harvest is threatened by high bacteria levels from rural nonpoint pollution. Two areas are of immediate concern;a marine station at the upper end exhibits summer bacteria exceedances. No livestock are nearby and dye testing of nearshore on-site sewage treatment systems showed no failures. Nearby freshwater streams have relatively low bacteria levels and upwelling groundwater is bacteria free. Marine sediment has a significant bacteria reserve. In Chapman Cove, the exceedances are more closely linked to rainfall events. An obvious source is livestock grazing along the shoreline. A tributary to the cove, Uncle Johns Creek, has high bacteria levels. The local Health Department’s efforts to conduct dye testing of on-site systems have not been successful, but the conservation district has been actively working with livestock owners. A microbial source tracking study sponsored by EPA using Bacterioides has identified that both ruminant and human markers are ubiquitous. A separate study by the University of Washington is looking at F+RNA coliphage typing. Stakeholders continue to meet to address the issues. While the agriculture community is responsive to pollution control actions, on-site owners continue to resist inspection of their systems. Evaluation of incentive and enforcement options is ongoing, plus additional investigation of the role of sediment bacterial reserves.
BEACH Program - A Four Year Review of Data
High levels of enterococcus bacteria in marine waters can be indicative of an increased risk of illness for recreational beach users. The Beach Environmental Assessment, Communication, and Health {BEACH} Program is currently being implemented in Washington State in response to the BEACH Act which was passed by the US Congress in 2000 to create a uniform system to protect users of marine waters. The Departments of Ecology and Health implement the EPA funded program in collaboration with county health jurisdictions and volunteer organizations. This presentation will include a brief overview of the Program and an analysis of four years of beach results, focusing on beaches that have levels of enterococcus above background levels. Several factors are known to cause increases in enterococci in marine waters. These factors include proximity of known contamination sources, number of swimmers, freshwater input from streams and rivers, rainfall, and sediment type. The presentation will conclude with a few examples of how an increased level of bacteria at beaches has lead to remediation efforts.
Intrusion of Domoic Acid into Puget Sound, Washington State
Several species of the toxigenic diatom Pseudo-nitzschia, together with low concentrations of domoic acid in shellfish have been observed in Puget Sound, Washington State, since 1991. However, only recently have high-density blooms of Pseudo-nitzschia forced the closure of recreational, commercial, and tribal subsistence shellfish harvesting in northern Puget Sound. Here we report on the environmental conditions associated with shellfish closures in two Puget Sound embayments during the closure events in Fall 2005. In Sequim Bay, shellfish harvest losses occurred on September 12 following the measurement of elevated macronutrient levels on September 2, and a bloom of P. pseudodelicatissima (up to 13 million cells per L) on September 9. Ambient NH4 concentrations >12 µM (measured on September 2) were due to anthropogenic inputs, likely from farm runoff and/or sewage inputs near Sequim Bay. The closure of a Penn Cove commercial shellfish farm on October 16 was caused by a bloom of P. australis that followed a period of sustained precipitation, elevated Skagit River flow, and persistent southeasterly winds. The relative importance of a number of environmental factors, including ocean temperature, stratification caused by rivers, and nutrient inputs, whether natural or anthropogenic, must be carefully studied in order to better understand the recent appearance of massive blooms of toxigenic Pseudo-nitzschia in Puget Sound.
Alexandrium Cysts in Puget Sound, Washington, USA
Alexandrium catenella bloomed in central Puget Sound in late summer 2006. Toxin levels in blue mussels reached 17,000 ug/100g resulting shellfish closures (F. Cox, Washington Department of Health). Paralytic Shellfish Poisoning is often present in shellfish in Puget Sound, but little is known about the distribution and biology of either the motile cells or cysts of the major causative species, A. catenella. Our survey of 32 sites in March 2005 found cysts of A. catenella in surface sediments throughout Puget Sound. Sequim Bay with 200 cysts/ml sediment and Quartermaster Harbor with 12,000 cysts/ml sediment had the highest abundances; other areas ranged from <10 to about 100 cysts/ml. Sediment parameters--grain size, total organic carbon (TOC) content, and metal (Cu, Cd, Zn, As, and Pb) concentrations--were measured to evaluate correlations with cyst abundance. Initial results indicate that there is no correlation between grain size, TOC content or metal concentrations with cyst abundance. Cyst concentrations and 210Pb were measured in sediment cores from some sites to determine historical cyst presence. Cysts were present to the bottom of cores from Sequim Bay and Quartermaster Harbor in abundances consistent with surface sediment counts.
Climate Variability and Paralytic Shellfish Toxins in Puget Sound Shellfish
Long term observations of Paralytic Shellfish Toxins (PSTs) in Puget Sound shellfish from the WDoH Biotoxin Program are used as a proxy to describe bloom dynamics of the harmful dinoflagellate species Alexandrium catenella from 1957 to 2002. Observations are selected for trend analyses based on the ability of the shellfish species to retain or depurate PSTs, frequency of observations at individual sites, and consideration of timescales of selected climate forcings. On seasonal to interannual timescales, Blue Mussels are used to identify “PSP hot spots” at Mystery Bay, Discovery Bay, Dockton and Sequim Bay. Hot spots are used to indicate exceptionally toxic events for case studies of preceding environmental conditions, and to develop annual indices of A. catenella bloom behavior for quantitative comparison with regional and large scale climate forcings. On longer timescales, PST accumulation in Sequim Bay Butter Clams covaries with warm phases of the Pacific Decadal Oscillation and the window of optimal growth conditions for A. catenella as determined by warm sea surface temperatures. Results from this study of observed climate influences on PSTs will be used to develop PSP risk forecasts at seasonal to interannual time scales, and to evaluate the potential influence of global warming on intensity and duration of future toxic events in Puget Sound. Recommendations are made for future monitoring of shellfish toxicity and environmental parameters to improve forecasting skill.