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1.
Peter G. Verity 《Estuaries and Coasts》2002,25(5):961-975
A sampling program was initiated in 1986 in the Skidaway River estuary, a tidally dominated subtropical estuary in the southeastern USA. Hydrography, nutrients, particulate organic matter (POM), and microbial and plankton abundance and composition were measured at weekly intervals at high and low tide on the same day at a single site. Hydrographic and nutrient data during 1986–1996 were given in Verity (2002); particulate organic carbon (POC), nitrogen (PON) and chlorophylla (chla) are presented here; plankton data will be presented elsewhere. Chla was fractionated into <8 μm and >8 μm size classes. All classes of POM exhibited distinct seasonal patterns superimposed upon significant long-term increases during the study period. Total chla, <8 μm chla, and >8 μm chla increased 36%, 61%, and 18%, respectively, however the fraction of total biomass attributable to small phytoplankton (<8 μm) increased 25%. The annual amplitude between minimum and maximum stock sizes increased significantly, meaning that bloom events became larger. POC and PON also increased 16% over the decade and, as observed with patterns in chla, exhibited increases in annual amplitude. The C:N ratio was typically 6.4–6.6 (wt:wt) and did not change significantly, while the annual mean C:Chla ratio decreased 19% from 165 to 140. These characteristics indicated highly labile POM composed of significant amounts of detritus, but which became increasingly autotrophic with time. Averaged over the decade, temperature explained 45–50% of the variance in POM. Nutrients were even better predictors of POM, as 60–75% of the variance in chla, POC, and PON were explained by ambient concentrations of DIN, or PO4. Combined with significant increases in NO3, NH4, PO4, Si(OH)4, and DON during 1986–1996, these data strongly suggest that anthropogenic activities contributed to increased loading of dissolved nutrients, which became incorporated into living and nonliving particulate organic matter. 相似文献
2.
Dinoflagellate Cysts in Coastal Sediments as Indicators of Eutrophication: A Case of Gwangyang Bay,South Sea of Korea 总被引:1,自引:0,他引:1
Diatom densities in the surface water and dinoflagellate cysts in bottom sediments of Gwangyang Bay were studied to determine
changes in the phytoplankton community structure in response to anthropogenic eutrophication and to assess the use of dinoflagellate
cysts as indicators of coastal eutrophication. Our results show that, in nutrient-enriched environments, diatoms are particularly
benefited from the nutrients supplied and, as a consequence, heterotrophic dinoflagellates that feed on the diatoms can be
more abundant than autotrophic dinoflagellates. In short-core sediment records, a marked shift in autotrophic–heterotrophic
dinoflagellate cyst compositions occurred at a depth of approximately 9–10 cm corresponding to the timing of the 1970s industrialization
around Gwangyang Bay. This tentatively indicates that diatom and dinoflagellate communities here have undergone a considerable
change mainly due to increased nutrient loadings from both domestic sewage effluent and industrial pollution. Our study suggests
a possible potential use of dinoflagellate cysts in providing retrospective information on the long-term effects of coastal
eutrophication. 相似文献
3.
Peter G. Verity 《Estuaries and Coasts》2002,25(5):944-960
The Skidaway River estuary is a tidally-dominated subtropical estuary in the southeastern USA surrounded by extensiveSpartina salt marshes. Weekly smapling at high and low tide began in 1986 for hydrography, nutrients, chlorophylla, particulate matter, and microbial and plankton biomass and composition; hydrographic and nutrient data during 1986–1996
are reported here. Salinity varied inversely with river discharge and exhibited variability at all time scales but with no
long-term trend. Water temperature typically ranged over 25°C and was without apparent long-term frend. Seasonal cycles in
concentrations of NO3, NH4, PO4, Si(OH)4, and DON were observed, with annual maxima generally occurring in late summer. Superimposed on seasonal cycles, all five
nutrients exhibited steady increases in minimum, mean, and maximum concentrations; mean concentrations increased c. 50–150%
during the decade. Nutrient concentrations were highly correlated with water temperature over the ten-year period, but weakly
related to salinity and discharge. Nutrients were strongly correlated with one another, and the relative ratios among inorganic
nutrients showed little long-term trend. Correlations among temperature and nutrient concentrations exhibited considerable
inter-annual variability. Major spikes in organic and inorganic nutrient concentrations coincided with significant rainfall
events; concentrations increased hyperbolically with rainfall. Although pristine compared to more heavily impacted waterways
primarily outside the region, residential development and population density have been increasing rapidly during the past
15–20 years. Land use is apparently altering nutrient loading over the long-term (months-years), and superimposed on this
are stochastic meteorological events that accelerate these changes over the short term (days-weeks). 相似文献
4.
Positive Relationship between Freshwater Inflow and Oyster Abundance in Galveston Bay,Texas 总被引:1,自引:0,他引:1
David Buzan Wen Lee Jan Culbertson Nathan Kuhn Lance Robinson 《Estuaries and Coasts》2009,32(1):206-212
Analysis of fisheries-independent data for Galveston Bay, Texas, USA, since 1985 shows eastern oysters (Crassostrea virginica) frequently demonstrate increased abundance of market-sized oysters 1 to 2 years after years with increased freshwater inflow
and decreased salinity. These analyses are compared to Turner’s (Estuaries and Coasts 29:345–352, 2006) study using 3-year running averages of oyster commercial harvest since 1950 in Galveston Bay. Turner’s results indicated
an inverse relationship between freshwater inflow and commercial harvest with low harvest during years of high inflow and
increased harvest during low flow years. Oyster populations may experience mass mortalities during extended periods of high
inflow when low salinities are sustained. Conversely, oyster populations may be decimated during prolonged episodes of low
flow when conditions favor oyster predators, parasites, and diseases with higher salinity optima. Turner’s (Estuaries and
Coasts 29:345–352, 2006) analysis was motivated by a proposed project in a basin with abundant freshwater where the goal of the project was to substantially
increase freshwater flow to the estuary in order to increase oyster harvest. We have the opposite concern that oysters will
be harmed by projects that reduce flow, increase salinity, and increase the duration of higher salinity periods in a basin
with increasing demand for limited freshwater. Turner’s study and our analysis reflect different aspects of the complex, important
relationships between freshwater inflow, salinity, and oysters. 相似文献
5.
Jennifer A. Goleski Florian Koch Maria A. Marcoval Charles C. Wall Frank J. Jochem Bradley J. Peterson Christopher J. Gobler 《Estuaries and Coasts》2010,33(5):1202-1215
Florida Bay is Florida’s (USA) largest estuary and has experienced harmful picocyanobacteria blooms for nearly two decades.
While nutrient loading is the most commonly cited cause of algal blooms in Florida Bay, the role of zooplankton grazing pressure
in bloom occurrence has not been considered. For this study, the spatial and temporal dynamics of cyanobacteria blooms, the
microbial food web, microzooplankton and mesozooplankton grazing rates of picoplankton, and the effects of nutrients on plankton
groups in Florida Bay were quantified. During the study, cyanobacteria blooms (>3 × 105 cells mL−1) persisted in the eastern and central regions of Florida Bay for more than a year. Locations with elevated abundance of cyanobacteria
hosted microzooplankton grazing rates on cyanobacteria that were significantly lower (p < 0.001) and less frequently detectable compared to sites without blooms. Consistent with this observation, cyanobacteria
abundances were significantly correlated with ciliates and heterotrophic nanoflagellates at low cyanobacteria densities (p < 0.001) but were not correlated during bloom events. The experimental enrichment of mesozooplankton abundance during blooms
yielded a significant decrease in the net growth rate of picoplankton but had the opposite effect when blooms were absent,
suggesting that the cascading effect of mesozooplankton grazing on the microbial food web was also altered during blooms.
While inorganic nutrient enrichment significantly increased the net growth rates of eukaryotic phytoplankton and heterotrophic
bacteria, such nutrient loading had no effect on the net growth rates of cyanobacteria. Hence, this study demonstrates that
low rates of zooplankton grazing and low rates of inorganic nutrient loading contribute to the persistence of cyanobacteria
blooms in Florida Bay. 相似文献
6.
To assess the importance of heterotrophic microplankton in the Wadden Sea, seasonal distribution and biomass of the main subgroups, that is, heterotrophic dinoflagellates, (separated into thecate and athecate forms), tintinnids, and aloricate ciliates, were studied in 1989 and 1990 in a total of six surveys covering the whole area of the northern German Wadden Sea. Heterotrophic microplankton biomass exhibited high spatial and temporal variation, ranging from 0 μg Cl?1 to 66 μg Cl?1, with maximum concentrations in spring., Mean stocks were lowest in winter (1.6 μg Cl?1) and highest in spring (11.7 μg Cl?1); intermediate concentrations were found in summer (8.5 μg Cl?1). In winter, the heterotrophic microplankton was dominated by tintinnids. In spring and summer, aloricate ciliates and dinoflagellates made up the largest part of the biomass. A pronounced feature was a shift within the dinoprotist group from athecate to thecate forms in summer. In spring, maxima of athecate dinoflagellate carbon were associated with blooms ofPhaeocystis globosa, indicating a close trophic relationship. From rough estimates of the daily grazing potential, based on microheterotrophic biomass and conversion factors from the literature, it may be concluded that heterotrophic microplankton temporarily share a main role in the transfer of food and energy to higher trophic levels within the pelagic system of the Wadden Sea. 相似文献
7.
We examined microbial processes and the distribution of particulate materials in the estuarine turbidity maximum (ETM, salinity 2–10 PSS) of northern San Francisco Bay on three cruises during the late spring of 1994 (low flow: April 19, April 28, May 17) and two cruises during the early summer of 1995 (high flow; June 13, July 18). Under low flow conditions, chlorophyll concentrations decreased by a factor of 2–4, bacterial abundance decreased by 20%, and L-leucine incorporation rate decreased by a factor of about 2 over a salinity range of 0–2 PSS, then remained relatively constant at higher salinities. Over this same salinity range under high flow conditions, chlorophyll concentration was c. twofold lower, bacterial abundance was c. threefold higher, and L-leucine incorporation rate was in the same range as during low flow. Under high flow conditions, chlorophyll concentration increased by 20%., bacterial abundance decreased by a factor of 2, and L-leucine incorporation rate decreased by half (June 13) or remained unchanged (July 19) with increasing salinity. Under low flow conditions the concentration of suspended particulate material (SPM), particulate organic carbon (POC), and particulate organic nitrogen (PON) increased 3–10 fold with salinity, to a maximum at intermediate salinities (c. 6 PSS). As a result, the contribution of phytoplankton to POC decreased from a maximum of 32% in fresh water to c. 6% in the ETM. The contribution of bacterial biomass similarly decreased from 5% in fresh water to 0.8% in the ETM. The C:N ratio of particulate material increased from <10 in fresh water to >12 in the ETM. High variability in abundance estimates confounded analysis of patterns in bacterial biomass partitioning between particle-associated and free-living fractions along the salinity gradient. However, the partitioning of L-leucine incorporation shifted dramatically from being predominantly by free-living cells in fresh water to being predominantly by particleassociated populations in the ETM. The metabolic fate of thymidine taken up differed, between particle-associated and free-living bacteria, suggesting some metabolic divergence of these assemblages. 相似文献
8.
Patricia M. Glibert Cynthia A. Heil Judith M. O'Neil William C. Dennison Mark J. H. O'Donohue 《Estuaries and Coasts》2006,29(2):209-221
Subtropical estuaries have received comparatively little attention in the study of nutrient loading and subsequent nutrient
processing relative to temperate estuaries. Australian estuaries are particularly susceptible to increased nutrient loading
and eutrophication, as 75% of the population resides within 200 km of the coastline. We assessed the factors potentially limiting
both biomass and production in one Australian estuary, Moreton Bay, through stoichiometric comparisons of nitrogen (N), phosphorus
(P), silicon (Si), and carbon (C) concentrations, particulate compositions, and rates of uptake. Samples were collected over
3 seasons in 1997–1998 at stations located throughout the bay system, including one riverine endmember site. Concentrations
of all dissolved nutrients, as well as particulate nutrients and chlorophyll, declined 10-fold to 100-fold from the impacted
western embayments to the eastern, more oceanic-influenced regions of the bay during all seasons. For all seasons and all
regions, both the dissolved nutrients and particulate biomass yielded N:P ratios <6 and N:Si ratios <1. Both relationships
suggest strong limitation of biomass by N throughout the bay. Limitation of rates of nutrient uptake and productivity were
more complex. Low C:N and C:P uptake ratios at the riverine site suggested light limitation at all seasons, low N:P ratios
suggested some degree of N limitation and high N:Si uptake ratios in austral winter suggested Si limitation of uptake during
that season only. No evidence of P limitation of biomass or productivity was evident. 相似文献
9.
We analyzed interannual variability in a long-term record of chlorophyll concentration and phytoplankton species composition
in the Rhode River, Maryland (USA). Over the approximately 30-year record, there was no long-term monotonic trend in phytoplankton
chlorophyll concentration, though temporary directional trends related to precipitation patterns sometimes persisted for a
decade before reversing. From counts on preserved samples, we estimated the dominance by different pigment-bearing groups
and size classes. Diatoms, dinoflagellates, and cryptophytes comprised about 80–97% of the annual averaged class-specific
biovolume. Cryptophytes dominated the first 2 years in the data set but displayed a long-term decline, after which diatoms
dominated in all but four consecutive years in which there were large dinoflagellate blooms. There was a long-term increase
in cells with equivalent spherical diameters from 4 to 10 μm, accompanied by declines in the proportion of cells in the 2-
to 4- and 10- to 20-μm size classes. The main cause of these changes in size classes was a long-term increase in Chroomonas sp. and Apedinella radians and long-term decline in Microcystis sp. and an unidentified cryptophyte, respectively. These taxa were cosmopolitan in their seasonal and spatial distributions,
and hence the long-term changes in taxa did not conform well with conceptual models based on succession of “life-forms.” The
segregation of diatoms and dinoflagellates expected on the basis of “life-forms” applied to seasonal and spatial patterns.
Characterizing the phytoplankton community in terms of diversity, size, and class-specific biovolume gave results that were
consistent with one another and added insight to the broad-scale changes in chlorophyll concentration. Subtle changes in the
size distribution of cryptophytes were not apparent from biovolume measures and would not have been apparent without microscopy.
Though causes of such shifts may be difficult to identify, identifying the causes and predicting potential consequences cannot
even be attempted without awareness of the phenomena. 相似文献
10.
Slavica Matijević Natalia Bojanić Grozdan Kušpilić Živana Ninčević Gladan 《Environmental Earth Sciences》2009,59(4):853-866
Phosphorus (P) species concentrations in 0–2 cm surface sediment layer were investigated monthly from November 2001 to December
2002 at the bay, channel and open sea stations in the middle Adriatic. Modified SEDEX method was used for inorganic phosphorus
species determination [P in biogenic (P-FD), authigenic (P-AUT), detrital apatite (P-DET) and P adsorbed on to iron oxides
and hydroxides (P–Fe)], and organic phosphorus (P-ORG). P-FD, P-AUT and P-DET concentration ranges (1.5–5.4, 0–2.7 and 0.4–3.4 μmol g−1, respectively) were similar at all stations, and showed no obvious common trend of seasonal changes. P–Fe ranged from 1.9
to 11.9 μmol g−1 with the highest values at bay station and higher seasonal oscillations than other inorganic P forms. P-ORG ranged from 0.3
to 18.7 μmol g−1 with higher concentrations at stations of fine-sized sediments and showed increased concentrations in warm part of the year
at all stations. Correlation between concentrations of P–Fe in the surface sediment layer and orthophosphate sediment-water
interface concentration gradients at bay and channel stations indicated to P–Fe importance in the orthophosphate benthic flux.
For the bay station, linkage between sediment P-ORG and chlorophyll a concentrations, primary production and microzooplankton abundance was established, indicating a 1 month delay of sediment
response to production fluctuations in the water column. 相似文献
11.
Phytoplankton seasonal and interannual variability in the Guadiana upper estuary was analyzed during 1996–2005, a period that
encompassed a climatic controlled reduction in river flow that was superimposed on the construction of a dam. Phytoplankton
seasonal patterns revealed an alternation between a persistent light limitation and episodic nutrient limitation. Phytoplankton
succession, with early spring diatom blooms and summer–early fall cyanobacterial blooms, was apparently driven by changes
in nutrients, water temperature, and turbulence, clearly demonstrating the role of river flow and climate variability. Light
intensity in the mixed layer was a prevalent driver of phytoplankton interannual variability, and the increased turbidity
caused by the Alqueva dam construction was linked to pronounced decreases in chlorophyll a concentration, particularly at the start and end of the phytoplankton growing period. Decreases in annual maximum and average
abundances of diatoms, green algae, and cyanobacteria were also detected. Furthermore, chlorophyll a decreases after dam filling and a decrease in turbidity may point to a shift from light limitation towards a more nutrient-limited
mode in the near future. 相似文献
12.
Baseflow and storm runoff fluxes of water, suspended particulate matter (SPM), and nutrients (N and P) were assessed in conservation,
urban, and agricultural streams discharging to coastal waters around the tropical island of Oahu, Hawai‘i. Despite unusually
low storm frequency and intensity during the study, storms accounted for 8–77% (median 30%) of discharge, 57–99% (median 93%)
of SPM fluxes, 11–79% (median 36%) of dissolved nutrient fluxes and 52–99% (median 85%) of particulate nutrient fluxes to
coastal waters. Fluvial nutrient concentrations varied with hydrologic conditions and land use; land use also affected water
and particulate fluxes at some sites. Reactive dissolved N:P ratios typically were ≥16 (the ‘Redfield ratio’ for marine phytoplankton),
indicating that inputs could support new production by coastal phytoplankton, but uptake of dissolved nutrients is probably
inefficient due to rapid dilution and export of fluvial dissolved inputs. Particulate N and P fluxes were similar to or larger
than dissolved fluxes at all sites (median 49% of total nitrogen, range 22–82%; median 69% of total phosphorus, range 49–93%).
Impacts of particulate nutrients on coastal ecosystems will depend on how efficiently SPM is retained in nearshore areas,
and on the timing and degree of transformation to reactive dissolved forms. Nevertheless, the magnitude of particulate nutrient
fluxes suggests that they represent a significant nutrient source for many coastal ecosystems over relatively long time scales
(weeks–years), and that reductions in particulate nutrient loading actually may have negative impacts on some coastal ecosystems. 相似文献
13.
Responses of Estuarine Bacterioplankton,Phytoplankton and Zooplankton to Dissolved Organic Carbon (DOC) and Inorganic Nutrient Additions 总被引:2,自引:0,他引:2
James N. Hitchcock Simon M. Mitrovic Tsuyoshi Kobayashi Douglas P. Westhorpe 《Estuaries and Coasts》2010,33(1):78-91
The response of planktonic bacteria and phytoplankton to various additions of dissolved organic carbon (DOC) as glucose, with
and without inorganic nutrients (nitrogen and phosphorus), was tested in the upper to mid Hunter Estuary, Australia. In situ
microcosms (1.25 L) were performed at two sites with varying salinities over three seasons. Analysis of variance showed a
significant difference among control and treatments for all seasons for the bacterial, dissolved oxygen and chlorophyll a responses (P < 0.05). A significant interaction between treatment and site was found in autumn for dissolved oxygen, autumn and spring
for bacterial and spring for chlorophyll a responses. At both sites for each season, and on nearly all occasions, bacterial surface area was enhanced by DOC addition
as indicated by both increased bacterial abundance and dissolved oxygen utilisation. DOC in combination with inorganic nutrients
sometimes further enhanced the bacterial response compared to DOC alone. Inorganic nutrients alone did not enhance growth
of the heterotrophic bacterioplankton. Addition of DOC alone led to decreased chlorophyll a relative to the control, probably due to competition for limited inorganic nutrients with the bacterioplankton DOC non-limiting
conditions. Results suggest that the heterotrophic community was limited by DOC at both sites and across seasons. An experiment
with a larger volume (70 L), performed over a longer time, compared a control with DOC addition. Increased bacterial biomass
as a result of DOC addition occurred at day 2. Chlorophyll a did not significantly differ between treatments. An increase in zooplankton density was recorded in the DOC treatment relative
to the control at day 10. This study supports the contention that increased DOC delivery with river inflows through environmental
flow allocations will stimulate heterotrophic bacterioplankton production in the upper Hunter Estuary. 相似文献
14.
Dynamics of transparent exopolymeric particles (TEP) and particle-associated carbohydrates in the Dona Paula bay, west coast of India 总被引:1,自引:0,他引:1
Surface seawater samples were collected over a period of 27 months at a shallow water station in Dona Paula bay from 1998–2000.
The samples were analyzed to assess the seasonal variations, inter-annual variability and the contributions of:
A distinct inter-annual variability was observed with an increase in the bacterial abundance, chlorophylla (Chl a), TEP and Sal-PCHO and their greater contribution to particulate organic carbon during May 1998–1999 than in June
1999–July 2000. Overall, there was no statistically significant correlation of TEP with phytoplankton biomass (Chl a), Sal-PCHO,
CPCHO and hydrodynamic conditions. A weak inverse correlation was observed between TEP and TBA (r = −0.397;p < 0.05) but the role of TEP as a C-source for bacteria was not evident. Both Sal-PCHO and CPCHO appeared to be two distinct
forms of carbohydrates. Unlike CPCHO, Sal-PCHO concentrations showed a positive trend with Chla and significant linear correlation with bacterial abundance (r = 0.44,p < 0.007,n = 48), indicating that Sal-PCHO as carbon source might have supported bacterioplankton abundance. The mean %TEP-C contribution
to the annual average organic carbon for 1998–2000 was 6.9% ± 5.8%, next only to phytoplankton-C (33.1 ± 22.1%) and greater
than bacterial-C (4.6% ± 4.6%) or carbohydrate-C (< 3.8%). Despite its greater contribution to the organic carbon pool, the
contribution of TEP-C to the benthic carbon demand and its fate in the study area could not be ascertained in this study. 相似文献
– | •transparent exopolymeric particles (TEP) concentration, |
– | •two forms of particle-associated carbohydrates — 1.5 M NaCl/saline extracted (Sal-PCHO) and 10 mM EDTA-extracted (CPCHO) and |
– | •total bacterial abundance (TBA) to particulate organic carbon pool. |
15.
Wim J. Kimmerer Nissa Ferm Mary Helen Nicolini Carolina Peñalva 《Estuaries and Coasts》2005,28(4):541-550
Egg production of planktonic copepods, is commonly measured as a proxy for secondary production in population dynamics studies
and for quantifying food limitation. Although limitation of copepod egg production by food quantity or quality is common in
natural waters, it appears less common or severe in estuaries where food concentrations are often high. San Francisco Estuary,
California, has unusually low concentrations of chlorophyll compared to other estuaries. We measured egg production rates
of three species ofAcartia, with dominate the zooplankton biomass at salinity above 15 psu, on 36 occasions during 1999–2002. Egg production was determined
by incubating up to 40 freshly collected individual copepods for 24 h in 140 ml of ambient water. Egg production was less
than 10 eggs female−1 d−1 most of the year, but as high as 52 eggs female−1 d−1 during month-long spring phytoplankton blooms. Egg production was a saturating function of total chlorophyll concentration
with a mean of 30 eggs female−1 d−1 above a chlorophyll concentration of 12±6 mg chl m−3. We take chlorophyll to be a proxy for total food ofAcartia, known to feed on microzooplankton as well as phytoplankton. These findings, together with long-term records of chlorophyll,
concentration and earlier studies of abundance of nauplius larvae in the estuary, imply chronic food limitation ofAcartia species, with sufficient food for maximum egg production <10% of the time over the last 25 yr. These results may show the
most extreme example of food limitation of copepod reproduction in any temperate estuary. They further support the idea that
estuaries may provide suitable habitat forAcartia species by virtue of other factors than high food concentration. 相似文献
16.
The composition of the zooplankton community in a macrotidal (8 m tidal range), tropical estuarine system (Darwin Harbour,
Australia; 12o28′ S, 130o50′ E) was studied over a 2 year period with the goal of describing biodiversity and determining the environmental factors
that have the greatest impact on community structure. Most (82–84%) of the >73 μm plankton was composed of copepod nauplii
and copepodites, and plankton samples taken with larger, coarser meshed (150 and 350 μm) nets did not contain significant
numbers of larger (non-copepod) organisms. In all, 32 copepod species were recorded, with small euryhaline marine copepod
species such as Parvocalanus crassirostris, Bestiolina similis and Oithona aruensis dominating the zooplankton. Plankton abundances ranged between 30,000 and 110,000 m−3, and there were significant year (2003 > 2004), season (wet > dry) and site differences (inner harbour sites > outer harbour
sites), but negligible diurnal differences. Multivariate analyses identified three sample groups: (1) middle and outer harbour
sites, (2) inner harbour and river sites and (3) the river site during the wet seasons. Middle and outer harbour stations
were characterised by a diverse mixture of coastal copepods, whereas inner harbour and river sites were dominated by P. crassirostris and O. aruensis. During the wet season, there was a distinct copepod community within the Blackmore River, dominated by Acartia sinjiensis, Oithona nishidai and Pseudodiaptomus spp. Environmental variables (nutrients and chlorophyll a) were correlated with salinity, which had the strongest influence on community structure. There was a significant drop in
species richness from harbour to river sites. Small copepods of the families Paracalanidae and Oithonidae dominate tide-dominated
Australian tropical estuaries, whereas copepods belonging to the family Centropagidae (such as Gladioferens spp.) appear to be characteristic of wave-dominated estuaries in southern Australia. 相似文献
17.
An ichthyoplankton survey (18 stations in seven sampling sectors) was conducted in Narragansett Bay in 1990 to provide information on abundance, distribution, and seasonal occurrence of eggs and larvae of estuarine fishes, including seasonal migrants. An additional goal was to examine changes in species composition, abundance, and distribution occurring since the last baywide survey in 1972–73. The taxonomic composition of eggs and larvae in 1990 (41 species in 25 families from 684 plankton samples) and in 1972–73 (43 species in 28 families from 6900 samples) was similar. Maximum abundance of fish eggs occurred in June and larvae in July, minimum abundance in September to February. Species diversity was greatest in May–July and lowest during January in both surveys. However, egg and larval densities in 1990 were considerably lower than in 1972–73. Bay anchovy, tautog, and cunner accounted for 86% of the eggs and 87% of the larvae in the bay in 1990. These three species accounted for only 55% of the eggs and 51% of the larvae in 1972–73, with menhaden accounting for another 18% of the eggs and 34% of the larvae. Searobins, scup, and butterfish eggs were common in 1973 (19%) but rare in 1990 (2%). Ichthyoplankton abundance for several of the most abundant species was significantly lower (p<0.05) in the Providence River, upper bay, and Greenwich Bay in 1990 than in 1972–73. Density of fish eggs and larvae in the lower portions of the bay was lower in 1990 for some species but not others. Distribution data suggested a general down-bay shift in density in 1990. *** DIRECT SUPPORT *** A01BY085 00015 相似文献
18.
Carlton D. Hunt David G. Borkman P. Scott Libby Richard Lacouture Jefferson T. Turner Michael J. Mickelson 《Estuaries and Coasts》2010,33(2):448-470
The Massachusetts Water Resources Authority (MWRA) conducts a comprehensive multidisciplinary monitoring program in Massachusetts
Bay, Cape Cod Bay, and Boston Harbor to assess the environmental effects of a relocated secondary-treated effluent outfall.
Through 2007, 8.7 years of baseline data and 7.3 years of postdiversion data (16 total years), including species level estimates
of phytoplankton and zooplankton abundance, have been collected. MWRA’s monitoring program and other studies make this region
one of the most thoroughly studied and well-described marine systems in the world. The data show that the diversion of MWRA
effluent from the harbor to the bay has decreased nutrients concentrations and improved water quality in the harbor (e.g.,
higher dissolved oxygen, lower chlorophyll). The diversion also resulted in an increase in dissolved inorganic nutrients (especially
ammonium) in the vicinity of the bay outfall, but no obvious impacts such as increased biomass or decreased bottom water dissolved
oxygen have been observed. Regional changes in phytoplankton and zooplankton unrelated to the diversion have been seen, and
it is clear that the bays are closely connected both physically and ecologically with the greater Gulf of Maine. Direct responses
to modifications of the nutrient field within a 10 × 10-km area centered near the midpoint of the 2-km long outfall diffuser
in Massachusetts Bay (a.k.a. the nearfield) have not been seen in the plankton community. However, plankton variability in
the bays has been linked to large regional to hemispheric scale (NAO) processes. 相似文献
19.
Richard J. Cowlishaw 《Estuaries and Coasts》2004,27(3):539-550
The standing stocks of ciliates and phytoplankton together with physical variables (temperature and density) were measured
biweekly from March 6, 1999, to March 22, 2000, in the marine-dominated region of the South Slough, the southern arm of the
Coos Bay estuary (Oregon, United States). The abundance and biomass of naked ciliates correlated significantly with phytoplankton
<5 μm (ultraphytoplankton) biomass throughout the sampling periods and with total phytoplankton biomass between October and
march; possibly due to a compositional shift in the >5 μm phytoplankton fraction from diatoms in the spring-summer period
to flagellates during this fall-winter period. Temperature could explain 49% of the variation of ultraphytoplankton and naked
ciliate biomass across seasons and may be important in determining the rate of the ciliate numerical response to increases
in ultraphytoplankton and its assimilation into ciliate biomass. High standing stocks of ciliates, their strong coupling with
ultraphytoplankton across seasons, and the relatively higher contribution of ciliate carbon to the ciliate and >5 μm phytoplankton
carbon pool in the October–March period suggest that ciliates are a significant component to the South Slough food web and
may be particularly important during seasons of reduced phytoplankton biomass. 相似文献
20.
S. Nakamoto S. Prasanna Kumar J. M. Oberhuber H. Saito K. Muneyama R. Frouin 《Journal of Earth System Science》2002,111(3):339-349
Western tropical Indian Ocean, Arabian Sea, and the equatorial Pacific are known as regions of intense bio-chemical-physical
interactions: the Arabian Sea has the largest phytoplankton bloom with seasonal signal, while the equatorial Pacific bloom
is perennial with quasi-permanent upwelling. Here, we studied three dimensional ocean thermodynamics comparing recent ocean
observation with ocean general circulation model (OPYC) experiment combined with remotely sensed chlorophyll pigment concentrations
from the Coastal Zone Color Scanner (CZCS). Using solar radiation parameterization representing observations that a higher
abundance of chlorophyll increases absorption of solar irradiance and heating rate in the upper ocean, we showed that the
mixed layer thickness decreases more than they would be under clear water conditions. These changes in the model mixed layer
were consistent with Joint Global Ocean Flux Study (JGOFS) observations during the 1994-1995 Arabian Sea experiment and epi-fluorescence
microscopy (EFM) on samples collected during Equatorial Pacific Ocean Climate Study (EPOCS) in November, 1988. In the Arabian
Sea, as the chlorophyll concentrations peak in October (3 mg/m3) after the summer plankton bloom induced by coastal upwelling, the chlorophyll induced biological heating enhanced the sea
surface temperature (SST) by as much as 0.6‡C and sub-layer temperature decreases and sub-layer thickness increases. In the
equatorial Pacific, modest concentrations of chlorophyll less than 0.3 mg/m3 is enough to introduce a meridional differential heating, which results in reducing the equatorial mixed layer thickness
to more than 20 m. The anomalous meridional tilting of the mixed layer bottom enhances off equatorial westward geostrophic
currents. Consequently, the equatorial undercurrent transports more water from west to east. We proposed that these numerical
model experiments with use of satellite andin situ ocean observations are consistent under three dimensional ocean circulation theory combined with solar radiation transfer
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