The health of the Rhode Island coastal lagoon
ecosystem is of importance due to its critical role as a
wildlife habitat and recreation destination. As human
population continues to expand along the coast, this
ecosystem will receive increasing pressure from
contaminants. In order to understand how the
ecosystem responds to such pressures, a multi-
disciplinary approach was employed to gauge the
extent and impact of chronic, low-level pollution,
examine how the ecosystem has changed and will
change over time, and to investigate methods to further
our ability to monitor change.

Three coastal lagoons along the southwest coast of
Rhode Island were selected for study: Ninigret,
Quonochontaug, and Winnapaug Ponds. They
represent a spectrum of conditions in terms of size,
volume, and human population densities, yet they are
all under similar pressures regarding future population
increase and tidal inlet modifications. The distribution of
organic and inorganic contaminants established that
these lagoons are not well mixed despite how shallow
they are. It was found that currently, these contaminant
concentrations are too low to cause any significant
biological impact.

Paleoproductivity studies were conducted in
Quonochontaug and Garden Ponds. Lithofacies
associated with hurricanes were identified. The
physical disruption or salinity alterations associated
with hurricanes appeared to have minimal impact on
long-term trends. However, sedimentation of the
lagoon’s tidal inlet leads to a freshening of the lagoon
and higher productivity. In contrast, a dredging project,
which opened the tidal inlet, led to an increase in
salinity within the lagoon and a decrease in
productivity. Anoxia was documented during a period
when the tidal inlet was closed.

Lastly, side-scan sonar technology was optimized to
accurately map critical geologic environments and
biologic habitats in Quonchontaug Pond in order to
provide a baseline to study future habitat alterations.
The 500 kHz side-scan survey was adequate to identify
eelgrass beds. Areas with boulders were at times hard
to differentiate from the eelgrass, necessitating
thorough groundtruthing with underwater video and
sediment grab samples. This method holds potential for
developing accurate estimates of eelgrass bed areal
coverage. Approximately eighty acres of eelgrass were
present in the lagoon.