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Abstract
Ozbay,
G., M. Jackson, N. Munyei and M. Reiter. 2007. Temperature- and
salinity-dependent phytoplankton profiles for the St. Jones River Watershed, Delaware. JEMREST 4:29-38
Point and non-point pollution can
disrupt the ecological functions of a watershed, resulting in a decline in
water quality while creating suitable conditions for phytoplankton blooms. These blooms may be preceded by changes
in environmental variables impacted by heavy rains and agricultural or
industrial discharges. To study the
significance of such variables, phytoplankton distributions were analyzed
microscopically to determine assemblage characteristics in relation to
temperature and salinity changes at six selected study sites in the St. Jones
River Watershed, Delaware. In June, the phytoplankton assemblage
contained 17% Euglenoids, 51 % Bacillariophycaea, 23% Chlorophyta, 5%
Cyanophyta and 4% Cryptophyta while
other species and bacteria were less than 1% of the total species identified. In July and early August, samples
contained 5% Euglenoids, 46% Bacillariophycaea, 28% Chlorophyta, 17%
Cyanophyta, and 5% Cryptophyta while
other species and bacteria made up less than 1% of the total sample. The only significant differences
(P<0.05) were observed in Cyanophyta and Euglenoids distributions between
the study months of June and July. We
obtained more than three-fold increase in Cyanophyta concentrations from June
to July while Euglenoids decreased three-fold from June to July. Temperature
seems to have more of an effect on the phytoplankton distribution pattern in
St. Jones River Watershed. Bacillariophycaea were the most dominant
species in the watershed system during the study months. Class Pyrrhophyta was detected at
the tidal sampling stations where the salinity gradient was higher. Changes in salinity levels were minor in
five of the six study sites, so were unlikely to impact the phytoplankton
distributions. Species inhabiting the
watershed system appear to have a better tolerance for salinity fluctuations
as observed in previous studies. Such
analyses elucidate the phytoplankton dynamics of these waters and assist
state resource managers in making decisions concerning water use and management
of aquatic life.
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