Home
--------------------------
Nahant
--------------------------
Narragansett Bay: Introduction
Water Quality
Methods
Observations
Results
Discussion
--------------------------
Bermuda: Introduction
Water Quality
Coral Disease
Aspergillosis
Hypothesis and Methods
Results
Discussion
--------------------------
Conclusions
--------------------------
References |
Bermuda
Water and Sewage
Treatment
Due
to the lack of a large source of freshwater, Bermuda relies on rainwater collection for
the majority of its freshwater, with a portion provided by underground
freshwater reservoirs, and an even smaller portion provided by seawater
desalination. Residences typically have their own filtration system for
collected rainwater, while water provided from underground reservoirs is
filtered and purified at a plant in Devonshire.
Residences usually use collected rainwater for tap water, and purified water
from the Devonshire
plant is pumped in or delivered for use in laundry, toilets, and showers (4).
Sewage
is directed into a cesspit or septic tank in every residence, which then
disperses through the limestone rock eventually into the ocean. In the city of Hamilton, pipes pump the city’s sewage into Seabright Outfall, located south of Hungry Bay in Paget. This outfall has a peak
flow of 500 thousand to 1 million gallons of sewage per day (5). The city of Hamilton
extended the Seabright Outfall from 1993 to 1994,
depositing the effluent approximately 700 meters offshore over a 60 foot deep
sandy area. The extension was made to reduce near shore impacts, but has
brought the effluent closer to deep offshore reefs. The city of Hamilton
asked BIOS to monitor this area for environmental impacts to both the
surrounding reefs and marine life in the sediment. BIOS determined that the
reefs are healthy, and effluent only passes over the reefs during infrequent
north winds (6). Over a 35-day monitoring period, BIOS found that there were only 2
days where shoreline impact was possible. Due to steady flow away from the
shore, BIOS found that it is unlikely for any discharge material to experience
long-term accumulation (7).
However, BIOS did
find an effect on marine life closer to the waste diffuser. Fish were observed
feeding off the waste stream, and particulate material was observed in patches
around the diffuser, but there was no evidence of any large mass of
organic material (7). BIOS also found that abundance and diversity of
fauna in the sediment was reduced significantly up to a distance of 10 meters
from the outfall, and is affected at a distance up to 50 meters from the source
(6). Monitoring sites located approximately 300 meters from the
sewage outfall, in the dominant flow direction of the waste stream, had "high percentage coral cover,
no obvious local absences/deficiencies in the major coral species or benthic
classes, and clustered tightly with the other comparable control
locations" (7). Furthermore, BIOS states that incidence of disease
was not higher nearer to the sewage outfall than other monitored areas (7).
Other Water Quality
Concerns
The
inability to establish wastewater and sewage treatment plants stems from both Bermuda’s isolation and population. Bermuda is 600 miles from the closest
continental landmass, causing localization of many waste management services.
Additionally, Bermuda
has a population density among the highest in the world, with an annual addition
of tourists six times that of the resident population. Pollution stems mainly
from disposing of the resident and tourist population’s waste, very little of
it being agricultural and industrial waste. Bulk waste, such as motor vehicles,
large appliances, and construction materials are dumped in a reclamation site
in an inshore basin at Castle Harbor,
adjacent to the international airport. Household waste is incinerated and mixed
with cement to form large blocks that are disposed of at this same location.
From the reclamation site, the nearest reefs are 200 meters away. This waste
site, along with possible groundwater contamination by pesticides, contribution
from cruise ships, and addition of sewage accounts for a potentially
significant source of pollution to the marine environment in Bermuda
(5).
BIOS is currently
addressing these issues and their potential impact on coral reefs. They are
also taking into consideration the knowledge that increased climate
stresses have already had deleterious affects on coral reefs, and that marine
pollution may serve to amplify these effects (5).
BIOS has conducted and is
currently conducting several projects regarding the effects of pollution on Bermuda's waters. BIOS established the Marine
Environmental Program (MEP) in 2004, under which BIOS conducts research on
water temperature and water quality to evaluate the relationship of these
factors with coral beaching events and disease outbreaks. The ecological
subprogram of MEP surveys and makes assessments of the flora and fauna at many
sites on the Bermuda platform in order to
identify if pollution, bleaching, and disease outbreaks are significant causes
of ecological change (8).
Conclusions drawn from this research are incorporated into BIOS's annual
report. The most recently published report (2005-2006) states that temperatures
of the inshore reefs vary greater temporally than temperatures at the offshore
reefs. Annual temperatures typically range between 14°C at inshore reefs (Tynes Bay),
and less than 11°C at offshore reefs. Water quality monitoring data shows that
nitrate, nitrite, and phosphate, and chlorophyll-a levels are noticeably
elevated at inshore areas during the summer months. According to this data,
BIOS states that locations of concern are Mill Creek due to its poor water
quality, Harrington Sound due to its unusual hydrography, and Hamilton Harbor
due to its connectivity with the Great Sound system. BIOS also determined that
one site, Tynes Bay, was anomalous to other sites that
were monitored for water quality and ecological changes. Tynes Bay
lacked many common coral species, possibly reflecting anthropogenic effects due
to close proximity of densely populated areas and shipping channels (7).
BIOS also preformed
photoquadrat surveys at two reefs close to the landfill adjacent to the
airport, and at other locations in Castle
Harbor. This data is
currently being analyzed, and no conclusions have yet been drawn from this
information (7).
Overall, Bermuda's isolation and lack of waste treatment facilities
elicits concern from public and scientific communities, and BIOS is taking
great strides to evaluate these anthropogenic effects on the marine
environment. Although not many conclusions have been drawn, the extent of
BIOS's research and their findings thus far shows that there is potential for Bermuda's pollution to have an affect on marine life.
|
