Enclosure (1) TO COMDTINST 16478.12
below the most stringent benchmarks for protection of sediment dwelling
organisms [ER-L, and the state No Observed Effects Level (NOEL) of 0.1 mg/kg].
In the area 10 to 20 meters from the AtoN, the average (about 0.06 mg/kg)
value is well below the NOEL, but about 9 percent of the individual samples
exceed the NOEL. The average value of the samples within 10 meters of the
AtoN (about 0.2 mg/kg) was above the NOEL, and about 40 percent of the
invidual samples were above the most protective. Between 75 and 100 percent
of the individual samples collected adjacent to batteries exceeded the NOEL.
Approximately half the samples adjacent to batteries exceeded the ER-M and the
state Probable Effects Level (PEL) of 1.4 mg/kg in the Alafia River area,
which has a higher mercury background do to watershed sources and sediment
characteristics. However none of the samples collected next to batteries
exceeded the PEL or ER-M at the mid bay AtoNs.
The sediment effects levels used for comparison are general and do not take
into account site specific conditions such as species present, sediment
characteristics, or bioavailability of mercury. Such general effects levels
tend to be more protective than levels developed for specific conditions and
areas. Even using possible overprotective effects levels for comparison, the
implication of the sediment concentration findings are that benthic species
density and diversity could be reduced to a measurable extent in the immediate
vicinity of the batteries. The could also be some effects on community
parameters within 10 meters of AtoNs. However there is very little potential
for environmental hazard beyond 10 meters from AtoNs. The effects anticipated
adjacent to batteries and to a lesser extend within the 10 meter radius are
not expected to be acute (e.g., mortality or gross histopathologic effects).
At the most, only chronic effects (e.g., measurable reduction in reproductive
rate) would be expected and since the effects would be over such a small area
no overall community or even population impacts would be expected.
Investigation of mercury concentrations in tissues of marine organisms in
Chesapeake and Tampa Bay was limited to collection of species of opportunity.
Animals attached to batteries and the AtoN structure were analyzed and
compared to background samles reported in the literature and at unlighted
AtoNs. In the Chesapeake the samples collected on batteries and attached to
lighted AtoNs were similar to specimens collected at the unlighted AtoN and
within the range of background values reported in the literature. The values
were also below concentrations reported in the literature associated with
adverse effects. However the comparisons were limited because the same
species could not be collected at every location and there were not values
reported in the literature for all species collected.
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