Brief summary of listed presentationsJohn Toll - Aquatic ecological risks posed by tributyltin (TBT) in US surface waters
Toll
discussed the monitoring program for EPA and US Navy for TBT risks from pre-1989 to 1997. Areas of observation included - Puget Sound, San Diego, Pearl Harbor, Lake Erie, Norfolk, Galveston Bay and Narragansett Bay.
Risk
monitoring was broken into categories representing four types of locations - Shipyards, Harbors, Marinas, and Fisheries or Shellfish habitats.
In 1989, 25% of species at risk were above the toxicity
threshold. In 1997 4-5% of risk species were at or below the toxicity threshold in marinas, shipyards and harbors. Zero percent of risk species were at risk in fisheries and shellfish habitats, even those within 1 km of
other sites.
Toll concludes the studies prove risks have declined largely because of TBT limits set into effect from the U.S. Organotin Act of 1988. As of 1997, only the marina and shipyard categories in one U.S. location
(Galveston) approached the TBT toxicity threshold. All other locations were below toxicity thresholds for TBT in the water column. This conclusion is supported by similar data from monitoring programs in the UK, France and
Australia.
Mary Sue Brancato - Evaluation of risks to Pacific Coast otters exposed to tributyltin
Brancato studied sea otters to come up with a risk analysis determination for marine mammals to
TBT. Otters represent a high potential risk species because they eat bivalves as a part of their diet, and bivalves bioaccumulate TBT. Otters also live in coastal areas in close proximity to high levels of TBT.
Brancato's extensive analysis was based on very conservative worst case scenario. Using this conservative analysis, she determined that 99% of the northwest otter population was not at risk from TBT diet exposure.
Of the
one percent still at potential risk of TBT harm, that risk is possible only if the otters consume 70% of the bivalves in their diet directly within the marina, an unlikely possibility.
Brancato concludes that as a test species
for marine mammals, the sea otter population does not seem to be suffering harmful effects of TBT in the marine environment.
Note - To date, no study has shown a direct cause and effect relationship between TBT in the
marine environment and harm to marine mammals.
Mary Sue Brancato - Invasive Species - impacts from introduction via shipping
Brancato explained the shipping industry introduces nonindigenous
organisms via ballast water, tank sediments and ship hull fouling.
New 1999 data indicates ship fouling has a higher potential for exotic species introduction then previously believed. Reports from Germany and Australia
found over 400 species were introduced in waters directly from the fouled hulls of ships. About one third of the exotic marine species in Australia harbors are determined to have been introduced via hull fouling.
In the
Pacific Northwest and the Eastern US coast, the European green crab is a major nuisance species believed to have come from accumulated fouling on the hulls of ships. Washington State noted over 6,000 new introductions of this
aquatic pest. The green crab damages native bivalves through consumption and native shorebirds due to habitat destruction.
Currently, groups in Europe and the International Maritime Organization are looking to limit or ban
antifouling hull paints. Such a ban would surely increase the likelihood of exotic species into nonindigenous waters since antifouling hull paints reduce the numbers of live organisms on ships' hulls. Brancato urges us
to consider all sides of the problem when looking at establishing marine regulations.
