The New Carissa Spill:
Did it cause an Oyster Die off?
Introduction
What began as a newscast story this past week has raised serious questions in my mind. NWCN cable network news covered a nearly fogotten topic of the New Carissa and the effects of the spilled chemicals. The story was reported by KING-TV news reporter Josephine Cheng . She focused on allegations made by Clausen Oyster Farms in upper Coos Bay, that the New Carissa oil spill devastated their shellfish crops. Later in the report, after viewing many dead or malformed oysters, a company spokesperson, representing the grounded tanker commented that, "the science can't establish that the New Carissa was the probable cause of the mortality..." and instead blamed it on "record rainfalls." (1)
My skepticism: who to believe; science or the intuitive reasons and observations of an oyster grower? So I began to do some research. . . .
The Accident and Resulting Spill
A pacific storm blew the ship aground on February 6, 1999 and oil began seeping from cracks immediately. There was about 400,000 gallons of oil and fuels aboard. Efforts were made to pump oil off the ship and when about 170,000 gallons remained the decision was made to burn off the remaining oil. Thus continued a series of bungled procedures which ended up spilling over 70,000 gallons of various oil and fuels. (2)
Effects of Oil on Ecosystems
Hydrocarbons are the most simple and primitive of organic compounds, being made up only of carbon and hydrogen atoms, which link together to form straight, branched chains, or ring structures. All living organisms produce hydrocarbons. The most obvious example is carotene. Plants synthesize waxes containing hydrocarbons in order to prevent leaf surface decay. There are approximately 300,000 different natural hydrocarbon compounds, that mostly come from oil reservoirs or coal deposits. Examples of common hydrocarbons are: gasoline, diesel fuels, diesel oil, motor oils, motor fuels, marine oils, marine fuels, hydraulic fluids, crude oil and lubricating oils. (3)
The oils carried on the New Carissa would barely pour at 70 F. This
high viscosity results from a large composition of waxy hydrocarbons in the
range of C20 to C34. Because of it''s high viscosity and lack of volatile
components, the product will be difficult to ignite. With its high viscosity
and waxy hydrocarbon composition, this product will not spread or
significantly sheen but would tend to glob in the water.
With considerable wave energy, these globs of product
will break into tarball-sized globs retaining their high
stickiness. The oil has a density of 0.98 so it will float.
When tarball-sized globs strand on the beach, they may
pick up sand and become heavy enough to not float. If they are eroded from
the beach, they would accumulate in the nearshore subtidal, in the trough
between the beach and the offshore bar (located about twice the distance
offshore as the ship). This product will not be dispersable. Since it is so
viscous, it will not readily form water-in-oil emulsions. These products do not
contain significant quantities of BTEX (benzene, toluene, ethyl benzene, and
the xylenes), so the inhalation hazard for humans in open areas will be
minimal. Another oil onboard, BFO fuel, appears to be a unusual blend of a
diesel-like fuel and asphaltenes. (4)
Most bivalves are primary consumers, typically exploiting organic
material that floats by them. It is possible to monitor chemical concentrations
in water and in suspended particles, but for many technical reasons, it is
simpler to measure concentrations in mollusks. This, together with their
immobility, makes mussels and oysters ideal for monitoring changes in
chemical concentrations at fixed locations. Some Organic Compounds
measured are DDT (DDT) Chlordane (
Cdane) Dieldrin (
Dield)
Polychlorinated Biphenyls (
PCBs) Polycyclic Aromatic Hydrocarbons
(
PAHs) Butyltin (
BT). (5)
A study was conducted and funded by the US Department of the Interior to find out toxicity levels of shellfish to hydrocarbons. To expose the eggs and/or larvae of shellfish species and the shellfish themselves to two different Gulf of Mexico oils, dispersed oil mixtures, and a single dispersant in controlled, flow-through or static 96-hr acute toxicity tests. Oysters were exposed in static tests to the dispersant and to dispersed oil mixtures.
The dispersant was particularly toxic to the embryo/larval stages, Similarly, the dispersed oil mixtures had statistically significant effects at the lowest concentrations tested. Since, the oyster is procreates externally and produces pelagic larvae, they are very susceptible to the dispersant. (6)
My Conclusions
I personally feel that the people who worked the oyster beds are keenly aware of sudden ecological changes to their products. Oysters are not able to uproot themselves or swim to another area should their surroundings become uninhabitable. A sudden and massive die-off tells us instinctively that something is seriously wrong. If the chemicals cannot be blamed directly, it would help to look at how the oil may be affecting the food source, or the success of the larvae which may be much more sensitive to chemical changes. I have to admit that blaming dead oysters on too much rain seems unlikely to me.
Works Cited:
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