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Water Quality Monitoring in Bermuda – General Information
The Bermuda Government initiated a water quality monitoring program
in September, 2007 at 17 sites with seagrass, which are spread across the
Bermuda Platform. At each of these sites chemical and physical water quality
characteristics are monitored monthly and a continuous temperature data logger
is deployed. At least one species of seagrass is present at each site.
Introduction
It has long been acknowledged that moorings, anchoring,
dredging, and dock construction have impacted Bermuda’s inshore seagrass beds
but recently it has been recognized that the extensive offshore beds are also
in decline. In 2004, intensive site surveys and mapping of Bermuda seagrass
meadows, by the Bermuda Reef Ecosystem Assessment and Mapping Programme (of the
Bermuda Biodiversity Project), documented a loss of about one-quarter of the
total area estimated from aerial images taken in 1997. Other minor studies
indicate a significant loss of seagrass area began about 1995 and was
precipitous between then and 1997; however, recent observations suggest this
loss is ongoing. This decline did not occur uniformly across the Bermuda
platform - and massive loss of area was only apparent in meadows far from
shore, which we think are removed from local anthropogenic impacts.
There are no comprehensive data or information we can use to explain
this decline, in particular there are no applicable data on nutrients,
temperature, and light penetration for any of the beds for periods relevant to
the onset of seagrass decline.
Water quality and physical characteristics of the water column
are among the ultimate limiting conditions for the presence of seagrass.
Transmission of light, temperature and the presence of adequate nutrients can
all determine survival of a seagrass bed. Mean salinity, salinity variability,
light transmission, and mean nutrient concentrations are important predictor
variables to models of landscape-scale changes of marine benthic habitats
(Fourqurean et al. 2003. Ecological Applications 13: 474-489). Nutrient levels
in the seagrass habitat, which includes both pore water and water column, are
the primary driving factors to degradation of seagrass beds in the conceptual
model of seagrass community dynamics, which underlies this program.
It has been clearly outlined in the Bermuda Seagrass
Conservation and Management Plan that comprehensive water quality monitoring is
an essential component of overall management of seagrass habitats in Bermuda.
Such a program did not exist in Bermuda until the Government initiated their
seagrass habitat studies. The water quality monitoring program also can provide
useful data to other management and monitoring issues in the marine
environment, including tracking terrestrial runoff and ground water and their
significance to nutrient loading.
Field protocols for water quality
sampling
Water quality samples are collected by staff of the Bermuda
Department of Conservation Services on a monthly basis, over a period of 1-3
days, from 17 permanent monitoring stations are sampled. Surface water
samples are collected to determine water column nutrient (dissolved inorganic
(DI) nitrate/nitrite, ammonium, reactive phosphorus, Total N, Total P,
silicate, DI carbon) and chlorophyll a concentrations. At the same time, PAR
attenuation profiles are obtained for the whole water column, salinity, oxygen
and turbidity values are collected for surface waters.