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2006/2007 Research Projects The effect of salt marsh ditches on estuarine
water quality Effects of once-through cooling on fish
populations Electric and nuclear power plants withdraw
large volumes of water from rivers and estuaries every year. This
water, used for cooling of the system, teems with eggs and larvae,
which are entrained and often killed by the water pumps. Entrainment
could then be another hurdle to recovery for declining fish populations.
This focus area of SCERP will estimate the number of fish and biomass
that would have reached adulthood had entrainment not occurred.
Several demographic and modeling approaches will be used (adult
equivalent loss, fecundity hindcast, empirical transport model)
to determine power plants' impact to a variety of commercially and/or
ecologically important species. Population abundances and number
of entrained larvae, necessary inputs to the models, will be assessed
through in-situ plankton net sampling Toxic blue green algal blooms on Long Island: Problems and potential solutions.Timothy W. Davis and Christopher J. Gobler Cyanobacteria or blue green algae are a common family of photosynthetic organisms which can produce natural biotoxins. During the past 4 years, the aim of this study has been to: 1. Assess the presence of toxic cyanobacteria in lakes located in Suffolk County, 2. Assess factors that promote these blooms, and 3. Assess methods which might be employed to alleviate bloom occurrence. All twenty lakes sampled contained potentially toxic cyanobacteria (typically Microcystis sp.) and detectable levels of the hepatoxin made by cyanobacteria, microcystin. Fifteen of the lakes had levels of microcystn exceeding levels permissible for drinking water according to the World Health Organization (WHO). Fortunately, Suffolk County residents use these systems for recreation, not potable water, and levels of toxin in 15 of the 20 lakes sampled were below levels considered to be a low recreational risk by the WHO. However, the remaining four lakes (Lake Agawam, Old Town Pond, Mill Pond, and Lake Ronkonkoma) all posed moderate-to-high risks to human health for recreation at various times during the study. Each system hosted elevated densities of multiple species of toxic cyanobacteria (up to 106 cells ml-1) and high levels of microcystin (up to 15 mg L-1) and, in some cases, anatoxin-a (up to 1 µg L-1). All of these systems except Lake Ronkonkoma are hypereutrophic, with high levels of nitrogen and phosphorus, suggesting a relationship between nutrient loading and bloom occurrence. In 2006, Mill Pond and Lake Agawam continued to have spectacular blooms, with levels of microcystin which far exceeded levels which represent a moderate recreational risk. Since incubation experiments with natural communities have demonstrated that nutrient loading can enhance the biomass and toxicity of these two systems lakes. This suggests watershed management plans to restrict nutrient loading could serve to limit the severity of toxic blooms. A final aspect of this project was to quantify toxic and non-toxic densities of Microcystis and to compare these densities to levels of microcystin. These results that toxin levels tracked densities of toxic sub-populations rather than total cell densities, indicating quantification of these populations may be more valuable that In 2007, two approaches will be tested as methods for reducing the occurrence of toxic blue green algae blooms. One approach, to be employed by the Mill Pond Homeowners association, will be the installation of water circulators which will push surface dwelling cyanobacteria to the bottom of the lake, potentially preventing bloom occurrence. The second approach will be a theoretical test of nutrient reductions in Lake Agawam. A nutrient budget will be constructed to determine the primary sources of nutrients to this system which should be targeted for reductions. In addition, experiments will be conducted to assess what impact nutrient loads will have on algal blooms. The facilitation of seagrass
(Zostera marina) productivity by suspension-feeding bivalves in
an experimental setting. Seagrasses and suspension feeders are both critical ecosystem engineers in estuaries. Seagrass beds are important structural habitats and suspension feeders, when abundant, can control phytoplankton densities. Furthermore, there may be mutual facilitation of growth and recruitment between seagrasses and suspension-feeding bivalves. In a series of mesocosm experiments, the effects of environmentally realistic densities of three different suspension-feeding bivalves (Mercenaria mercenaria, Crassostrea virginica, Mytilus edulis) on the growth of eelgrass (Zostera marina) in a eutrophied environment were examined. Experimental treatments with bivalves consistently had significantly lower chlorophyll a concentrations (p < 0.05), and most bivalve treatments also showed significant increases in light penetration (p < 0.05). Eelgrass growth was measured by leaf area productivity, and varied from 0.318 ± 0.018 cm2 shoot-1 d-1 to 0.832 ± 0.036 cm2 shoot-1 d-1 (mean ± SE); leaf area productivity was always significantly higher in the treatments with the highest density of bivalves compared to a control without bivalves (p < 0.05). The data indicate that clearance of the water column and the subsequent increase in light penetration was the primary mechanism by which suspension-feeding bivalves facilitated the growth of eelgrass. This finding has important implications for the conservation of estuarine seagrass habitats and shellfish populations, specifically suggesting that healthy populations of suspension-feeding bivalves can serve as a control on estuarine eutrophication and can help restore degraded, light-limited seagrass habitats. Eutrophication in the Forge River Estuary As coastal human populations expand globally,
adverse environmental impacts are being observed in estuaries. The
Forge River in Mastic, NY, is a brackish riverine estuary that has
gained recent attention due to reports of seasonal hypoxia and deaths
of multiple marine species. A major cause of hypoxia can be eutrophication,
which in turn can be stimulated by anthropogenic nutrient loading.
During 2006, research was conducted to understand the role of eutrophication
in the hypoxic conditions of the Forge River water column. Bi-weekly
time series water sampling, spatial cruises, light-dark respiration
experiments and a submerged water quality probe were used to collect
information about the water column's physical structure, phytoplankton
community biomass, diversity and productivity and nutrient concentrations.
The Forge River experienced chlorophyll a levels exceeding 400 µg
L-1 and dissolved inorganic nitrogen concentrations at >100 µM
through the summer and fall months. Bottom waters of the Forge remained
hypoxic for extended periods of time during summer (i.e. several
weeks during July and August). Phytoplankton communities included
several potentially harmful dinoflagellate species including A.
sanguinea, P. minimum and P. micans. Light-dark respiration experiments
indicated the water column was net heteritrophic, meaning oxygen
consumption strongly outweighed production in the Forge River. This
is likely caused by the great abundance of heterotrophic dinoflagellates
and bacteria and is a factor in the hypoxic conditions observed
throughout the summer. A reduction in nutrient concentrations in
the Forge may ease the occurrence of algal blooms and improve bottom
oxygen levels in the Forge River. Can hard clams (Mercenaria mercenaria)
ameliorate anthropogenic light stress for eelgrass (Zostera marina
) through increased nutrient availability? Eelgrass, Zostera marina, is a critical habitat in many estuarine systems, providing refuge from predation and nursery grounds for many commercially important fin and shellfish species. Positive interactions have been studied between seagrass and bivalves, including hard clams, Mercenaria mercenaria, often indicating the importance of grass to bivalve survival and growth. However, the coastal lagoons which make up the Long Island South Shore Estuaries (LISSE) have seen precipitous declines in both hard clam stocks and eelgrass. This study examined the distribution of seagrass and environmental characteristics along two bays of the LISSE, Shinnecock and Quantuck. A total of 81 randomly selected sites were chosen throughout the two bays, where the benthic plant community was surveyed, eelgrass standing crop was sampled, sediment cores were removed and hard clam densities were assessed. Concurrently, an in situ fertilization experiment was run at two light levels with the addition of a commercial fertilizer or a hard clam. In the survey, eelgrass was found at only 11 surveyed sites with a mean 65.4 ± 62.7 grams dry weight/m2. Hard clam stocks were estimated to be very low, 0.77± 1.03 clams/m2 over the whole study area. However, in the manipulative experiment, hard clams were shown to significantly increase leaf area productivity (cm2SS-1d-1) in shaded plots (p<0.001), indicating that clams are able to ameliorate light stress for eelgrass. These findings demonstrate a need for recognizing and understanding positive interactions in coastal marine ecosystems as they may be critical to restoring these systems.
Hemigrapsus sanguineus, the Asian shore crab,
was first observed on the Atlantic coast of the United States in
1989 and has since spread from Nova Scotia to North Carolina, becoming
the numerically dominant species in some rocky intertidal areas.
Recently, it has been observed outside of its native habitat, in
salt marshes on Long Island (NY) using algae and fiddler crab burrows
for shelter. The use of Uca burrows by the invasive, non-burrowing
crab may have an effect on the burrowing activity of Uca crabs,
which in turn could affect salt marsh functioning. Laboratory experiments
were performed to examine potential competition for burrows between
the native fiddler crab ( Uca pugnax and U. pugilator) and H. sanguineus.
Preliminary results indicate that H. sanguineus does compete with
Uca and is able to displace an established crab from its burrow.
Often, Uca showed aggressive behaviors toward H. sanguineus (claw
waving, repeated approaches to the burrow), yet only once in this
study was a fiddler crab able to re-take its burrow by ejecting
the Asian shore crab. These findings suggest that the expansion
of H. sanguineus into the salt marsh may cause changes in the burrowing
activity of Uca spp.
The effects of increased temperature and
presence of bioturbators ( Mercenaria mercenaria ) on sulfide (?H2S)
production in natural manipulated sediments was assessed in a 14-d
laboratory experiment. We hypothesized that increased temperature
and absence of hard clams would promote increased porewater sulfide
concentrations (z = 0-1, 5-6, 14-15 cm). Forty-eight microcosms
were filled with sediments collected in close proximity to Zostera
marina (eelgrass) beds near Fire Island, Great South Bay (GSB) NY.
Microcosms were randomly assigned to treatments of glucose enrichment
(high, medium, low), molybdate (presence/absence), hard clams (presence/absence),
and temperature (ambient/+4°C ambient). Three sediment perfusers
filled with glucose, filtered seawater, or molybdate were added
to sediments to create high (HG), medium (MG), low glucose (LG),
and molybdate (MB) treatments. Glucose was used Characterization, dynamics, and ecological
impacts of harmful Cochlodinium polykrikoides blooms on eastern
Long Island, NY, USA. We report on the emergence of Cochlodinium
polykrikoides blooms in the Peconic Estuary and Shinnecock Estuary,
NY, USA, during 2004 - 2006. Blooms occurred during late summer
when temperatures and salinities ranged from 20-25°C and 22-30
ppt, respectively. Bloom patches achieved cell densities exceeding
105 ml-1 and chlorophyll a levels exceeding 100 µg L-1, while
background bloom densities were typically 103 - 104 cells ml-1.
Light, scanning electron and ultrathin-section transmission electron
microscopy suggested that cells isolated from blooms displayed characteristics
of C. polykrikoides and provide the first clear documentation of
the fine structure for this species. Sequencing of a hypervariable
region of the large subunit rDNA confirmed this finding, displaying
100% similarity to other North American C. polykrikoides strains,
but a lower similarity to strains from Southeast Asia (88-90%).
Bioassay experiments demonstrated that 24 h exposure to bloom waters
(> 5 x 104 cells ml-1) killed 100% of multiple fish species (1-week
old Cyprinodon variegates, adult Fundulus majalis, adult Menidia
menidia) and 80% of adult Fundulus heteroclitus. Microscopic evaluation
of the gills of moribund fish revealed epithelial proliferation
with focal areas of fusion of gill lamellae, suggesting impairment
of gill function (e.g. respiration, nitrogen excretion, ion balance).
Lower fish mortality was observed at intermediate C. polykrikoides
densities (103 - 104 cells ml-1), while all fish survived for 48
hr at cell densities below 1 x 103 cells ml-1. The inability of
frozen and thawed-, or filtered (0.2 µm)-bloom water to cause
fish mortality suggested that the thick polysaccharide layer associated
with cell membranes and/or a toxin principle within this layer may
be responsible for fish mortality. Juvenile bay scallops (Argopecten
irradians) and American oysters (Crassostrea virginica) experienced
elevated mortality compared to control treatments during a nine-day
exposure to bloom water (~5 x 104 cells ml-1). Surviving scallops
exposed to bloom water also experienced significantly reduced growth
rates. Moribund shellfish displayed hyperplasia, hemorrhaging, squamation,
and apoptosis in gill and digestive tissues with gill inflammation
specifically associated with areas containing C. polykrikoides cells.
In summary, our results indicate C. polykrikoides blooms have become
annual events on eastern Long Island and that bloom waters are capable
of causing rapid mortality in multiple species of finfish and shellfish.
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