United States
Environmental Protection
Agency
Chesapeake Bay
Program
Annapolis MD 21401
Research and Development
EPA-600/S8-80-039   Nov. 1983
Project Summary
Distribution of  Submerged
Vascular Plants,  Chesapeake
Bay,  Maryland
Richard R. Anderson
  This research was initiated with the
overall objectives of determining past
and current (1978)  distribution of
submerged aquatic vegetation (SAV)
in Chesapeake Bay, Maryland, and to
formulate recommendations for fu-
ture surveys with regard to frequency
and methodology.
  Current distribution of SAV was
determined through interpretation of
1:24,000 scale black-and-white pho-
tographs taken from a seaplane during
the growing season. Distribution of
SAV was mapped on 1:24,000 U.S.
Geological  Survey (U.S.G.S.)  topo-
graphic map  mylars. A  total of 77
maps were produced. A photo-copy of
each map  is included in  the final
report. The minimum mappable bed
size was approximately 0.25 hecta res.
There were 16 quad sheets with no
mappable vegetation  present, and 24
sheets that had less than 10 hectares
of vegetation. Of the 40 sheets with
less than 10 hectares of vegetation,
11 were north of the  Chester/Mago-
thy Rivers and 21 were south of the
Choptank/Upper Patuxent  Rivers to
Smith Island  on the Eastern  Shore.
This indicates that the mid-portions of
Chesapeake  Bay were relatively
healthy with regard to distribution of
submerged vegetation.  This area of
the Bay also contained  the highest
diversity of submerged vegetation.
  Diversity declined rapidly from eight
to two to three species in the southern
portion of the Eastern Shore where
Zannichellia  palustris and Ruppia
maritima predominated.  Only a few
small areas of Zostera marina were
found in the lower Bay, in the South
Marsh Island area.
  Past distribution of SAV was deter-
mined through interpretation of archi-
val photographs of varying scale and
type. Distribution from 1952 to 1978
for various dates within that time
period was plotted for three areas in
the  upper Bay. These sites encom-
passed  the Chester River area, the
Eastern Bay area, and one site on the
western shore included Salt Peter and
Seneca Creeks.
  The Chester River site yielded the
best  photography, and the Eastern
Bay the worst. Trends in the Chester
River area indicate fluctuation in
distribution with time. The "bloom"
and consequent decline olMyriophyt-
lum spicatum over the whole Bay may
have accounted for some of this
fluctuation. There was a decline in the
1972 data probably as a result of a
hurricane during June. The 1978
survey  showed an encouraging  in-
crease in distribution.
  The Eastern Bay area  site yielded
very little distribution data although a
downward trend from 1970 to 1978
is indicated. The Salt Peter/Seneca
Creek area site was selected because a
thermal power generating station,
which began operation in 1962, dis-
charges heated water into Salt Peter
Creek.  SAV distribution data prior to
1960 and after 1964 indicate a
relatively stable situation. However,

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during that time, Myriophyllum "blooms"
occurred and might have masked the
absence of more thermally sensitive
species. A slight downward trend  in
distribution may have occurred from
1970 to 1978.
  Recommendations for future SAV
surveys  include larger-scale color
photography in areas  defined as
"critical," tq better define species
association and a frequency of at least
once every three years.
  This report was submitted in fulfill-
ment of Grant No. R 805977-01 -0 by
The American University under spon-
sorship of the U.S.  Environmental
Protection  Agency,  and covers the
period June 1,  1978 to January 31,
1980. Work was completed Septem-
ber 30, 1979.
  This Project Summary was devel-
oped by EPA's Chesapeake Bay  Pro-
gram,  Annapolis. MD. to  announce
key findings  of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
Introduction
  Over the last 10 years the Bay-grass
population  of the  Chesapeake has
declined dramatically. In an attempt to
better understand the trends in distribu-
tion and  abundance of  submerged
aquatic vegetation (SAV), aerial photog-
raphy was used to  establish an SAV
inventory of the Maryland portion of the
Bay. By interpreting these black-and-
white photos, investigators  hoped  to
focus on species concentrations and to
assess the usefulness of  photography
for estimating past and future trends.
   While  SAV beds  may seem bother-
some to boaters, their importance to the
Bay's ecosystem is seemingly limitless.
Grasses are a principal source of food
for  waterfowl and  some  herbivorous
fish species. SAV serves as a habitat for
species of copepods and mollusks and
as a nursery or shelter area for fish and
crabs. Grasses are the primary producers
of vegetative biomass: almost all of the
above ground crop is contributed to the
detrital food chain.  SAV has a wave-
dampening function as  it reduces
shoreline erosion and allows sediments
to settle. Bay grasses  also act  as
nutrient buffers and seasonally impor-
tant sources of dissolved oxygen.
  For these many  reasons this study
was conducted to determine past and
current distributions  of  SAV and  to
formulate recommendations for future
surveys.

Procedure/Methodology
  During the  summer of 1978, aerial
photographs  were taken of the Bay
shoreline where grasses  are found.
Fourteen percent of the area could not
be photographed due to military restric-
tions but field work  was substituted.
Field studies  were also conducted  in
other areas  to verify photographic
information and  to identify dominant
species.
  Information from the photographs
was then transferred to 77 U.S. Geolog-
ical  Survey  Maps;  17 of the  maps
covered areas with no mappable vege-
tation and 24 contained less than 10
hectares of grasses. To determine how
distribution and abundance have changed
over time, archival photos dating from
1952 to 1978 were analyzed. The
Chester River area,  the Eastern Bay
area, and Salt Peter and Seneca Creeks
were chosen to indicate historical
trends.

Results
  In interpreting the photographic
coverage of the Maryland portion of the
Bay, scientists determined that the mid-
Chesapeake is relatively healthy in both
diversity and abundance. Archival
photographs indicate that grasses in the
Chester River area increased until the
1960s, declined, and increased again
until a decline after a hurricane in 1972.
There seems to be a trend of increased
distribution in 1978.
  Archival  data  for the Eastern Bay
were  too insignificant  to draw any
meaningful conclusions. Salt Peter and
Seneca Creeks had a greater distribution
of SAV tha n i n the early 1970s but there
seems to be some stabilization in the
1978 survey.

Recommendations
  Broad SAV surveys should be  initi-
ated every  three years to record and
predict  trends. Yearly  monitoring  of
regionally representative areas  should
be  more complete,  including species
composition, percentage cover, and
seasonal growth characteristics. Color
photography should be used as it
enhances species distinctions.
  Lab and field studies should continue
so that the parameters of Bay-grasses,
with respect to light, temperature, and
other factors which may threaten SAV
populations, can  be determined. While
aerial reconnaissance maps distribution
and diversity, it does not ascertain
critical ranges.
  Richard R. Anderson is with the American University, Washington, DC 20016.
  William A. Cook was the EPA Project Officer (see below for contact).
  The  complete report, entitled   Distribution of Submerged  Vascular Plants,
    Chesapeake Bay. Maryland,"(Order No. PB 83-264 226; Cost: $14.50, subject
    to change) will be available only from:
          National Technical Information Service
          5285 Port Royal Road
          Springfield,  VA 22161
          Telephone: 703-487-4650
  For information contact David Flemer at:
          Chesapeake Bay Program
          U.S. Environmental Protection Agency
          2083 West Street, Suite 5G
          Annapolis MD 21403
                                            ftU.S GOVERNMENT PRINTING OFFICE 1983-659-01?/7219

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Environmental Protection
Agency
                                       Center for Environmental Research
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