Linking the dynamics
of nutrient cycling and primary producers to hypoxia in the Forge
River, Mastic, NY
Amanda M. Burson, Stephanie C. Talmage,
and Christopher J. Gobler
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 and anthropogenic nutrient loading. Research
was conducted to understand the role of eutrophication and primary
producers in the occurrence of hypoxic conditions of the Forge
River ecosystem. Bi-weekly time series water sampling, 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, productivity,
and nutrient concentrations. Surveys and experiments were conducted
to understand the role of Ulva lactuca in nutrient cycling and
hypoxia in the Forge River. From 2006 - 2008, the Forge River
experienced chlorophyll a levels exceeding 120 µg L-1 and
ammonium levels peaked at levels 47.0 µM, nitrate levels
at 20.0 µM, and phosphate at 4.50 µM through the summer
months. Bottom waters of the Forge remained hypoxic and/or anoxic
for extended periods of time during summer (i.e. several weeks
during July and August). In April, Ulva abundance peaked with
percent cover ranging from 45 - 97%. Ulva abundance then declined
dramatically at all sites during the summer months and then displayed
a minor increase peak in September and October (~2% coverage).
The decline in Ulva abundance during summer occurred when temperatures
exceeded 25ºC and when less light was unable to penetrate
to the bottom of the water column due to high pelagic chlorophyll
a levels. Experimental incubations demonstrated that decaying
Ulva both released nutrients and contributed to oxygen consumption.
Therefore, the seasonal decline in Ulva may supply regenerated
nutrients to pelagic algal blooms and may directly and indirectly
promote hypoxia in the Forge River.
Quantification of nutrient loads and their impact on cyanobacteria
blooms in a hyper-eutrophic freshwater system, Lake Agawam, Southampton,
NY, USA.
Matthew Harke, Tim Davis and Christopher
Gobler
Nuisance cyanobacteria blooms have plagued
Lake Agawam, Southampton, NY, for a number of years. Recent monitoring
has shown that during May through October, blooms are dominated
by Microcystis spp., and become nitrogen limited. Recent studies
have found toxins produced by Microcystis spp. and other cyanobacteria
within the lake and fish kills from low oxygen levels have also
been documented to follow bloom crashes. Here we report on a nutrient
budget constructed to quantify point and non-point sources for
nutrients entering the lake to assist in guiding lake remediation
efforts. Dissolved nitrogen was found to primarily originate from
groundwater, a storm drain at the north end of the lake and benthic
fluxes from sediments. Phosphorus inputs, both organic and inorganic,
mainly originated from sediments. These findings suggest that
remediation efforts should focus on relieving groundwater inputs
but as this can often prove too costly or politically difficult,
significant changes can be made by reducing storm water input
and possible dredging of the lake bottom. Nutrient dilution experiments
performed in 2007 demonstrated that reducing nutrients will not
only reduce algal biomass, but may also yield a shift in the phytoplankton
community away from cyanobacteria and toward non-blue green algal
species. Since cyanobacteria blooms are the cause of many environmental
problems in Lake Agawam, including fish kills, a focus on nutrient
reduction should be a part of any future management plan for Lake
Agawam.
The effect of water column circulators on algal blooms and water
quality in Mill Pond, Watermill, NY
Timothy W. Davis and Christopher J. Gobler
Harmful cyanobacteria blooms have become
common occurrences in some Long Island lakes to the ecological
detriment of these systems. Because such blooms are often associated
with poorly flushed waters, mixing surface waters with high densities
of cyanobacteria to deeper waters with low light levels has been
hypothesized to be a means of disrupting cyanobacteria blooms.
The goal of this study was to compare the algal dynamics and water
quality in Mill Pond, Watermill, NY, before (2005, 2006) and after
(2007) the installation of Solar Bee water column circulators.
Temperature, nutrient levels, and water clarity were not significantly
altered by the introduction of the circulators, although the average
dissolved oxygen concentration was significantly reduced (10.7
± 2.28 mg L-1 to 7.62 ± 2.85 mg L-1; p=0.003; t-test;
Table 1). While average chlorophyll a concentrations also decreased
from 220.0 ± 92.95 µg L-1 to 64.1 ± 14.05
µg L-1, total concentrations of the cyanobacteria (based
on phycocyanin levels) were unchanged. As such, the average phycocyanin:chlorophyll
ratio increased from 0.37 ± 0.05 to 0.90 ± 0.33,
suggesting an increase in the relative abundance of phycocyanin-containing
cyanobacteria among the phytoplankton community. The composition
of the cyanobacteria community was altered by the water mixers.
In 2007, Microcystis colony densities almost doubled (986 ±
253 to 1,816 ± 596 mL-1), Anabaena colony densities decreased
slightly (< 10%), while Aphanizomenion colony densities were
dramatically reduced to nearly undetectable levels (1,416 ±
673 to 1 ± 1 colonies mL-1; p< 0.001; Mann-Whitney rank
sum). In sum, increasing vertical water circulation alone did
not reduce blooms of cyanobacteria Mill Pond in 2007, perhaps
due to its shallow nature (< 4 m). Since our prior research
has demonstrated that nutrients stimulate cyanobacterial blooms
in Mill Pond, remediation efforts which target nutrient reductions
may have greater success in alleviating blooms.
The effect of tidal export from salt marsh ditches on estuarine
water quality and plankton communities
Florian Koch and Christopher J. Gobler
Salt marshes are an important transition
zone between terrestrial and marine ecosystems. In their natural
state they often function to cycle or trap important natural and
anthropogenic derived nutrients and pollutants. Many US east coast
salt marshes, including those on Long Island, were ditched during
the 20th century, potentially altering their function. The goal
of this study was to assess the impact of water from salt marsh
ditches across Long Island, NY, USA, on estuarine water quality.
We found that concentrations of inorganic nutrients (ammonium,
phosphate), dissolved and particulate organic nitrogen and carbon,
and coliform bacteria were significantly enriched in salt marsh
ditches compared to the estuaries they discharge into and became
more enriched in ditches as tidal levels decreased. Quantification
of nitrogen sources in Flanders Bay, NY, suggested salt marsh
ditches could represent a substantial source of N to this estuary
(6 - 20%). Bottle incubation experiments demonstrated that water
from salt marsh ditches was capable of significantly enhancing
the growth of multiple classes of phytoplankton, with large diatoms
and dinoflagellates being the groups which displayed the most
dramatic increases in growth. Experiments further demonstrated
that salt marsh ditches were capable of significantly enhancing
pelagic respiration rates, suggesting discharge from ditches could
effect estuarine oxygen consumption. In summary, this study demonstrates
that tidal draining of salt marsh ditches is capable of degrading
multiple aspects of estuarine water quality.
The role of sulfide toxicity among other
multiple stressors in Zostera marina populations in Long Island
South Shore Estuaries
Konstantine Rountos and Bradley J. Peterson
Eelgrass (Zostera marina) has been declining
in the south shore estuaries over the last several decades. This
loss has affected many of the functions that this plant provides
to the ecosystem. Like all plants, the primary limiting factors
for growth and survival are sufficient light and nutrient availability.
However, there are many areas of the south shore estuaries where
neither of these are limiting and yet there is no eelgrass. This
project explored the impact of sulfide toxicity and how reduced
light (and hence photosynthesis) might compound this toxicity
for eelgrass. A field survey of porewater sulfide was conducted
in Great South Bay. In addition, both a manipulative laboratory
and field experiment were conducted. The field survey demonstrated
that there are many areas in GSB where the porewater sulfide concentration
is above what has been found to be toxic to eelgrass. The laboratory
experiment showed that productivity was reduced at the highest
sulfide levels and that when present hard clams significantly
increased productivity at the highest sulfide levels. The field
experiment resulted in lowered productivity at the highest sulfide
concentration and significantly reduced standing crop. The negative
effects of sulfide were elevated when light availability was reduced.
The effect of nutrient loading and suspension-feeding
bivalves on water quality and estuarine resources: eelgrass, juvenile
fish, juvenile shellfish
Charles C. Wall, & Bradley J. Peterson,
Christopher J. Gobler,
Long Island estuaries previously supported high densities of eelgrass
(Zostera marina) and resource bivalves, such as hard clams (Mercenaria
mercenaria), eastern oysters (Crassostrea virginica), and bay
scallops (Argopecten irradians). Overfishing, eutrophication,
harmful algal blooms, and habitat loss have all taken their toll
on these populations, and many stake-holders would like to restore
these resources to local waters. Recent changes in land use and
wastewater treatment have reduced nutrient loading to these estuaries,
but eelgrass and bivalve populations have not recovered. We conducted
a series of mesocosm experiments to simultaneously test the effects
of nutrient loading and historic suspension-feeder densities on
the growth of eelgrass, juvenile bivalves, and juvenile fish (sheepshead
minnow, Cyprinodon variegatus). High nutrient loading rates (above
current management goals) led to higher chlorophyll a levels,
lower water clarity, and increased growth of juvenile bivalves
(hard clams and oysters) relative to controls with low nutrient
loads (ambient waters). Filtration by adult suspension-feeders
(M. mercenaria) decreased chlorophyll a levels, increased water
clarity and the growth of eelgrass, but significantly decreased
the growth of juvenile bivalves and fish relative to controls
with no filtration from adult suspension-feeders. These results
suggest that either nutrient loading or bivalve filtration or
both have the capacity to structure estuarine food webs and affect
the recovery of estuarine resources. Ecosystem-based approaches
will need to account for both anthropogenic nutrient-loading and
bivalve restoration to successfully manage our estuaries.
Estimating impacts of power plant water
withdrawal on fish populations: Developing a novel Bayesian approach
for calculating entrainment mortality
Santiago Salinas and Stephan B. Munch
The Indian Point and Northport power plants withdraw enormous
volumes of water from nearby river and estuarine habitats throughout
the year with the potential to heavily impact fish populations
through entrainment and impingement. To estimate the impact of
entrainment mortality on the local fish populations we collected
larvae at fourteen stations near each power plant from June through
October 2007. To analyze these data we developed a Bayesian population
dynamics model that accounted for both natural and entrainment
mortality. We applied this modeling framework to data for Bay
anchovy from the Hudson river and estimate that approximately
11 million larvae were killed by entrainment. Although large,
this number likely reflects only about 1% of the initial population
of Bay anchovy in the Hudson.
2006/2007
Research Projects
The effect of salt marsh ditches on
estuarine water quality
By Florian Koch and Christopher J. Gobler
Salt marshes are an important part of coastal ecosystems, representing
critical habitats and serving as filters for terrestrially-derived
nutrients and contaminants. Due to the threat posed by mosquito
born-illnesses, salt marshes lining many northeast US estuaries
have been drained of their standing water by "ditching"
for nearly a century. This activity can accelerate the flow of
water through salt marsh and to neighboring estuaries via tidal
exchange. The future of salt marsh ditches remains an open question,
as there are plans to re-excavate ditches which have filled in
via sedimentation, as well as plans to restore marshes via "plugging"
of the ditches (e.g. marsh reclamation project in Accabonac Harbor,
East Hampton). The objective of this study was to establish flux
rate of nutrients (especially nitrogen) from ditched marshes adjacent
to Flanders Bay (western Peconic Estuary) and in Accabonac Harbor
and determine the impact of exported ditch water on estuarine
phytoplankton communities. Through the summer of 2006, ditches
in Flanders Bay and Accabonac Harbor contained significantly higher
levels of total dissolved nitrogen (57 ± 14 M and 27 ±
4.7 µM) then adjacent estuarine waters in each system (21
± 2.7 M and 14 ± 4.0 µM; p < 0.05). The
tidal draining of the ditches accounts for a flux of >1,100
moles of N per day into Flanders Bay and > 450 moles of N per
day into Accabonac Harbor, suggesting ditch drainage may be a
major source of N to each system. Experimental incubations demonstrated
the ability of ditchwater to significantly (p < 0.05) enhance
phytoplankton biomass and growth rates in both estuarine systems.
Pigment analysis indicated that ditch water specifically increased
the growth of larger phytoplankton, such as diatoms and dinoflagellates,
in Accabonac Harbor. In Flanders Bay, these additions yielded
enhanced growth of all major phytoplankton groups, including those
implicated in the formation of harmful algal blooms (HABs). Managed
plugging of salt marsh ditches in either system will decrease
N fluxes, contributing toward the Peconic Estuary's Comprehensive
Management Plan to minimize N loads.
Effects of once-through cooling on fish
populations
Professor Steven Munch and Santiago Salinas
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.
Charles C. Wall, Christopher J. Gobler and Bradley J. Peterson
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
Amanda Burson and Christopher J. Gobler
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?
John Carroll, Christopher J. Gobler, Bradley J Peterson
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.
Burrow Competition Between the Native Fiddler Crab, Uca spp.,
and the Invasive Asian Crab, Hemigrapsus sanguineus. Alexa Fournier and Bradley J. Peterson
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.
Because Uca burrowing is known to influence primary production
in the salt marsh, the expansion of H. sanguineus into the salt
marsh could have wide-ranging effects on this ecosystem.
The effects of increased temperature and bioturbation on porewater
sulfide concentrations in Great South Bay (NY) sediment.
Konstantine Rountos and Bradley J. Peterson
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
to stimulate microbial sulfate reduction in sediments producing
sulfides, molybdate was used to inhibit sulfate reduction. Twelve
microcosms in both ambient and +4°C ambient temperature treatments
received 3 hard clams (shell length = 25mm), producing 16 different
treatments of 3 replicates each. Microcosms were exposed to a
10hr light - 14hr dark photoperiod and were sampled weekly using
porewater sipper devices to extract porewater at the desired depths.
Porewater was analyzed for total sulfide and total Fe concentrations
colorimetrically using a UV spectrophotometer. The influence of
multiple stressors (sulfide toxicity, habitat modification, increased
temperature) on eelgrass survival in GSB has not been adequately
assessed. This research provides insight into sulfide dynamics
in GSB sediments for a future comprehensive eelgrass field experiment.
Characterization, dynamics, and ecological
impacts of harmful Cochlodinium polykrikoides blooms on eastern
Long Island, NY, USA. Christopher J. Gobler, Dianna L. Berry, Amanda Burson, Florian
Koch, Brooke S. Rodgers, Lindsay K. Moore, Jennifer A. Goleski,
Bassem Allam, Yingzhong Tang
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.
2005 Research
Effects
of Tidal Discharge from Salt Marsh Ditches on Estuarine Ecosystems
By Tanya Reisenauer
Although salt marshes are critical habitats
in coastal ecosystems, anthropogenic activities threaten the natural
function of these systems. For nearly a century, 'ditching' of
salt marshes has been undertaken to reduce standing water and
mosquito populations in salt marshes. This practice concurrently
accelerates the flow of salt marsh water to neighboring estuaries
via tidal exchange. The objective of this study was to establish
flux rates of nitrogen and fecal coliform bacteria from salt marsh
ditches to estuaries and to determine the impact of salt marsh
ditch water on the growth of estuarine phytoplankton communities.
Mosquito ditches contained high levels of nitrogen (> 100 µM)
and fecal coliform bacteria (>2,000 per 100 ml). The draining
of mosquito ditches in Flanders Bay likely accounts for a flux
of > 1,200 moles of N per day and thus represents ~25% of the
N load to the southern portion of the bay and nearly 10% of the
N load to the entire bay. Partial and complete plugging of these
ditches can reduce these N fluxes by 50 - 100%. Experiments demonstrated
that ditch water is capable of enhancing phytoplankton growth
rates, in general, and the growth of harmful algae (i.e. Aureococcus
anophagefferens , Heterosigmna akishiwo, Prorocentrum minimum)
in particular. As such, mosquito ditches are a source of N and
fecal coliform bacteria which can degrade water quality in estuaries
such as Flanders Bay. Since the plugging mosquito ditches can
effectively eliminate ditch flow, such a practice seems warranted
in ecosystems such as the western Peconic Estuary where the primary
goal of the estuary's Comprehensive Management Plan is to minimize
N loads to this region.
________________________________________________________________
Eelgrass Growth Dynamics as a Function
of Nutrients Availability and Light Limitation in the Long Island
South Shore Estuary By Sara Petrochic
Eelgrass (Zoatera marina) meadows are important
ecological habitats that act as sediment stabilizers, nursery
grounds, and food sources for many marine organisms. Unfortunately,
eelgrass meadows have declined worldwide in temperate estuaries
in recent years. This study looked at how nutrients ease the stress
of shading, one possible reason for this decline. By marking and
collecting grass, and measuring leaf morphometrics from infield
experimental quadrants with differing levels of light and nutrients,
we determined that increased nutrients can ameliorate the stress
of shading. Nutrients added by natural sources, such as bivalves,
are significant enough to increase productivity and leaf area
in both shaded and non-shaded areas. Therefore, adding clams or
other bivalves could be one way to slow the decline of seagrass
meadows.
________________________________________________________________
An assessment of the environmental factors
that promote toxic cyanobacteria blooms in various Suffolk County
lakes
By Timothy Davis and Jennifer Goelski
Cyanobacteria or blue green algae are a
common family of photosynthetic organisms which can produce natural
biotoxins. The aim of this study was to assess the presence of
toxic cyanobacteria in lakes located in Suffolk County and to
assess factors which promote these blooms. Of the dozen lakes
sampled, all contained potentially toxic cyanobacteria (typically
Microcystis sp.) and levels of the hepatoxin, microcystin, which
exceeded levels permissible for drinking water by the World Health
Organization (WHO). Fortunately, Suffolk County residence rely
on these systems for recreation rather than drinking water, and
8 of the 12 lakes sampled were below the levels considered to
be a low recreational risk by the WHO. However, the remaining
four lakes monitored (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 1
mg L-1) and, in some cases, anatoxin-a (up to 1 µg L-1).
All of these systems except Lake Ronkonkoma are hypereutrophic
systems, with high levels of nitrogen and phosphorus, suggesting
nutrient loading may be promoting bloom occurrences. Incubation
experiments with natural communities confirmed this hypothesis,
demonstrating that at various times, nutrient loading enhanced
the biomass and toxicity of these lakes. Such a finding suggests
watershed management plans to restrict nutrient loading could
serve to limit the severity of toxic blooms. The finding that
warmer temperatures enhance cyanobacteria biomass suggests that
future global warming may increase bloom duration and intensity
if nutrient levels remained unchecked.
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The ameliorating effects of the hard
clam Mercenaria mercenaria on eelgrass Zostera marina during experimental
algal blooms By Molly Fox
A series of mesocosm experiments were conducted to evaluate the
potential for hard clams to increase light levels for eelgrass
productivity. Throughout all experiments, there was an increasing
trend of increased eelgrass productivity in mesocosms with hard
clams verses those without. Statistical analysis did not reveal
significant differences in eelgrass productivity. However, there
were clear trends in the reduction of the larger phytoplankton
by the hard clams. Mesocosms with and without clams were visibly
different from each other by day 4 of all of the experiments.
In those mesocosms that had clams, the bottom of the mesocosm
was visible, while it was not in those that lacked them. The first
set of experiments did not partition the chlorophyll by size fraction.
The second and third set of mesocosm experiments did. The subsequent
phytoplankton partitioning revealed that the larger sized phytoplankton
was significantly reduced in the clam treatments. However, it
appeared that the high water temperatures that were present for
the second experiment reduced the hard clam grazing rates and
thus their effect on the eelgrass. The third set of experiments
was conducted in late September and the lower light at that time
resulted in lower eelgrass productivity in both treatments, making
a statistically significant difference unachievable. Despite the
lack of statistical significance for these experiments, the strong
trend in the second experiment supports the original hypothesis
that hard clam grazing can enhance eelgrass productivity through
increasing water transparency.
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The occurrence and ecology of harmful
algae in the tributaries and estuaries of eastern Long Island
By Colleen Norman and Brian Gibbins
Harmful phytoplankton represent a serious
threat to coastal aquatic resources, and to date, but the documentation
of these events in eastern Long Island estuaries has been limited.
This study was designed to historically examine the types of phytoplankton
which have been present in the brackish Peconic River, and to
closely examine the dynamics of phytoplankton in multiple tributaries
on eastern Long Island in 2005. A secondary goal was to examine
the potential role of nitrogen and vitamins in promoting the occurrence
of harmful algal bloom events. Examination of phytoplankton samples
collected within the Peconic River from 2000 - 2005 indicated
the presence of more than a dozen harmful phytoplankton species.
Blooms were caused primarily by dinoflagellates which reached
densities exceeding 106 cells L-1 and most commonly bloomed during
late summer. Patterns among tributaries monitored were similar
in 2005 with multiple harmful dinoflagellates forming blooms in
August and September. Notably, a spectacular bloom of the red
tide dinoflagellate Cochlodinium polykrikoides began in the Peconic
River and Meetinghouse Creek in August and then spread throughout
the Peconic Estuary in September, to the detriment of multiple
species of shellfish. Observational and experimental data demonstrated
that both nitrogen and organic vitamins play a key role in promoting
these blooms. In summation, it seems that tributaries which have
high nutrient loads may serve as incubators for the growth of
harmful algae and are capable of seeding receiving estuaries with
massive blooms via tidal exchange. As such, more careful monitoring
and nutrient mitigation strategies in these tributaries are required
to minimize the impacts of these blooms on east end estuaries.
2004
Research
Lindsey
Rohrbach, class of 2005:Trace
metal burdens in liver samples from seals stranded on Long Island,
NY (1988-2004)
John Carroll,
class of 2004:
An assessment
of the eelgrass, Zostera marina, populations in Shinnecock
and Quantuck Bays, Long Island: limitations on growth
Jessica
Lucchini, class of 2005:Hypoxia
in the Peconic River Estuary and its effects on the benthic and
pelagic community
Melanie
Morin, class of 2005:
Optimal conditions for automated fragment analysis of Zostera
marina microsatellite PCR products
Brian
Gibbins, class of 2005:Effects
of pesticide application on Cyprinidonvariegatus
in a Salt Marsh ecosystem
Timothy
W. Davis, class of 2004:
Toxic cyanobacteria
blooms on Long Island, NY
2003
Research
Patrick Curran,
Class of 2004: Causes and impacts
of anthropogenic eutrophication in the Peconic River Estuary,
Long Island, NY
Laurie Mentzner, Class of 2003: Microsatellite
diversity and fitness in stranded juvenile harp seals (Phoca groenlandica)
Ray Patelli, Class of 2003: Tracing
the Movement of Water Through a Grid Ditched Salt Marsh
Matt Vilbas, Class of 2003:
The
Effects of Pesticide Application on Cyprinodon variegatus and
Mysidopsis bahia in Salt Marsh Ecosystems
Michelle Weiss, Class of 2004: A
Preliminary Study Assessing the Most Effective DNA Extraction
Protocol for Zostera marina Populations Present in Long Island,
NY Bays
