The
top of an outfall riser, through which effluent is
discharged, is home to a rock crab, brown and white
sea anemones, and orange or bone white "sea peach"
tunicates. (See
larger image.)
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From
May through August 2003, the Massachusetts Water Resources
Authority conducted six nearfield and two farfield water column
surveys, and four bacteria surveys; three sediment flux and
two benthic fauna studies; and one sediment contamination
study. We deployed and collected mussels for our bioaccumulation
study. We also conducted an underwater inspection of the outfall
to ensure it was operating properly. (See
monitoring location map).
FINDINGS
In
this report, we examine general conditions,
Bacteria, Floatables,
Algae, Flounder,
Outfall inspection, Sediment
studies, and Marine mammal sightings.
General Conditions: Surface
waters continued to warm throughout the summer, strengthening
the stratification at all but the shallower harbor stations.
Bacteria: No bacteria were detected
in 82 of the 90 water samples analyzed. The highest count
was 8 colonies per 100 ml, below the stringent standard for
unrestricted shellfishing of 14/100 ml.
Floatables: No debris
of human origin was found in 4 of the 12 debris tows. Small
pieces of plastic, paper, or styrofoam were found in the remaining
8 tows. Small white bits of fat were found in 5 tows and were
observed on the surface in the vicinity of the outfall.
Phytoplankton (marine algae): After
a strong spring phytoplankton bloom, preliminary chlorophyll
data suggest summer surface values were moderately low, but
mid-depth chlorophyll was high in the nearfield throughout
the summer but especially in early July.
Our rapid
analyses, designed to identify only larger phytoplankton species,
reported consistently low numbers of a mixed diatom-dinoflagellate
assemblage throughout the summer.
Flounder:
Our survey
of winter flounder in the spring of 2003 showed no severe
liver disease (neoplasia) at any sampling site. The incidence
of centrotubular hydropic vacuolations, an early stage indication
of disease, was below the long term average at all sites.
In general,
contaminant levels in fish tissue were within the historical
range. Only mercury in liver and muscle tissue of flounder
collected at the outfall site fell slightly above previously
observed values.
During
the survey, field scientists observed that some flounder in
Western Massachusetts Bay had external lesions on the blind
(bottom) side. Additional studies are planned to better characterize
the nature and prevalence of these lesions, if they are observed
again.
| Battelle
Ocean Sciences conducts most of the Mass. Bay
monitoring for MWRA. (See
larger image). |
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Outfall
Inspection: In June, we carried out an inspection
of the Massachusetts Bay outfall, using a remotely operated
vehicle to inspect each diffuser riser for damage or fouled
discharge ports. The survey documented that the risers are
undamaged and working as designed.
Sediment
studies: Our
annual hardbottom monitoring survey was carried out in June,
in concert with the outfall inspection. No major changes were
observed in the 2003 survey; lush epifaunal (seafloor) communities
were observed on rock surfaces throughout the nearfield. Two
new stations were established this year. These two stations
are more distant from the outfall than are the other sites
sampled in this study, and will help us determine if any changes
that might be observed at sites close to the outfall are widespread.
In August,
we conducted our annual soft-sediment monitoring. While sample
analysis is ongoing, early observations indicate that sediments
near the outfall show no major changes. The depth of oxygen
penetration into the sediments (shallowing of that depth can
be an indicator of eutrophication) remains essentially unchanged
over the past few years, well within the range of conditions
observed during baseline, before the outfall was in use. These
observations are supported by available data from the sediment
nutrient flux surveys conducted in May, July, and August.
Marine Mammal Sightings:
A couple of minke whales and two pods of white-sided dolphins
were observed around the nearfield in mid-May. A finback whale
and another unidentified baleen whale were observed in early
August.
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