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Why
is SAV important? |
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Submerged
aquatic vegetation (SAV), primarily eelgrass (Zostera marina)
and widgeon grass (Ruppia maritima), is an important component
of the Barnegat Bay-Little Egg Harbor ecosystem, serving as important
habitat for benthic epifauna and infauna (aquatic animals living
on or within the bottom of the bay). Some organisms graze on SAV
(e.g., gastropods, fish, duck, muskrats) and eelgrass also serves
as valuable spawning, nursery and feeding grounds for finfish populations.
SAV also stabilize the benthic habitat by baffling waves and currents
and alleviate substrate erosion.
*
*
reference at bottom of page
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Why
study it? Is the SAV in Barnegat Bay at risk? |
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Studies
were conducted due to the ecological importance of seagrass and
recent indications of dieback. These seagrasses are a sensitive
indicator of the bay's overall health.
Comparison
of the earlier maps with the 1990's survey shows an overall decrease
of approximately 2,000 to 3,000 hectares in the area of seagrass
beds. While there are indications of seagrass decline, due to the
great difference in mapping methods used for each of the surveys,
we are cautious in directly attributing the decrease in mapped eelgrass
acreage to a large-scale dieback.
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What
affects SAV occurrence and health? |
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The
occurence of SAV species in the bay strongly depends on environmental
conditions. Each species has its own requirements for and tolerances
of physical characteristics, such as temperature, salinity, sediment
composition, water velocity, and turbidity. The temporal and spatial
shifts of SAV in the Barnegat Bay ecosystem likely result from naturally
occurring cycles although human activities such as dredging, nutrient
loading, boating and the use of personal watercraft may be detrimental.*
The impact of increased development within the watershed coupled
with the possible recurrence of wasting disease has sparked concern
about the status of eelgrass (Zostera marina) and other seagrasses.
Wasting disease, presumably caused by the protist Labyrinthula
zosterae, is responsible for significant declines of seagrasses
during certain years.*
Barnegat Bay shows a pattern of higher water turbidity as well as
greater nutrient loading the northern bay which follows the pattern
of increased residential and commercial development.
*
reference at bottom of page
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How
were the SAV mapped? |
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The
'SAV MAPPING METHODS' section
describes the field and aerial surveys conducted by various government
agencies and scientists.
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What
is GIS? How were the SAV maps used by CRSSA with this technology? |
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Geographic
Information System (GIS) is a technology utilizing digital geographic
data and computer software/hardware to map, analyze, model and present
spatial information. In this case, the digital geographic
data is submerged aquatic vegetation.
The maps from the 1960's, 1970's, 1980's and 1990's were digitized
from their original paper map sources into the GIS. Once digitized,
the maps were analyzed by comparing the different time periods simultaneously;
additionally, using other data of turbidity and seagrass depth limits,
CRSSA was able to develop a model to predict the distribution of
potential seagrass habitat through Barnegat Bay under current and
theoretical conditions. These modeled distributions were then compared
to the mapped distributions then presented visually using the GIS.
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I
am a GIS user interested in obtaining the SAV data. Are they available? |
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Yes,
GIS users can download the data from the CRSSA Barnegat Bay Resources
web site (http://www.crssa.rutgers.edu/projects/runj/bbay.html)
>> then go to 'GIS Data Downloads').
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Are
these maps suitable for determining the presence or absence of SAV
at a particular site location? |
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These
maps, as presented on this web site, provide a regional picture
of SAV distribution at various points in time and are not intended
for site level permit applications or litigation purposes. These
maps and data, alone, are not sufficient to determine the presence
or absence of SAV. Conclusive evidence concerning the presence
or absence of SAV requires site inspections, preferably at several
points in time during the SAV growing season.
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*
text extracted from 'The Scientific Characterization of the Barnegat
Bay - Little Egg Harbor Estuary and Watershed' produced by the
Barnegat Bay Estuary Program |
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