Enclosure (1) TO COMDTINST 16478.12
The results of tissue analysis from Tampa Bay were generally similar to the
findings from Chesapeake Bay. Tissue levels were generally below values
considered background and below levels reported in the literature as being
associated with adverse effects. The findings did differ from those in the
Chesapeake in that there was an indication that animals attached to batteries
often had higher tissue concentrations than organisms of the same species
attached to AtoN structures. All of these findings are qualitative and
inconclusive because there were over a dozen species collected, most of which
had no background values reported in the literature or comparable samples at
unlighted AtoNs.
Based on the indication of possible elevated levels of animals close to
batteries found in Tampa, more rigorous biological investigations were
conducted in the Tennessee River and Puget Sound. Large amounts of sediment
was collected and seived for organisms from the areas where sediment for
mercury analysis was collected (i.e. at multiple locations at batteries and in
a random pattern around the AtoN). The animals from these locations were
analyzed for mercury. This approach allowed comparison of mercury levels in
the same species in relation to proximity to batteries.
In the Tennessee River, two species were collected at almost all locations so
the possible effects of mercury from batteries on sediment dwelling organisms
from could be made on a species basis. The investigation revealed no elevated
tissue concentrations compared to levels known to cause effects or background
concentrations for the area. The spatial cover of the sampling and
collocation with analytical samples permitted an evaluation of sediment
concentration distribution. This evaluation showed no correlation with
proximity to batteries or sediment concentrations. The lack of similarity
with sediment concentrations is attributable to the very low concentrations in
media and the high natural variability in sediment and biological tissue.
The biological investigation for Puget Sound revealed almost identical
conditions to those seen for the Tennessee River. The number of species
collected were more diverse but general comparisons could be made. There was
no indication of elevated tissue concentrations relative to batteries,
background concentrations, or levels known to cause effects. Based on these
findings it seems clear that mercury from batteries is not affecting biota at
the AtoNs included in the Puget Sound or Tennessee River investigations.
These results are supported by the low percentage of methylmercury found in
sediments at all AtoNs investigated. The highest percentage methylmercury
found was
4-9
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