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1.
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
2.
Gretchen Rollwagen-Bollens Scott Gifford Stephen M. Bollens 《Estuaries and Coasts》2011,34(5):1026-1038
Decline of native pelagic species in estuarine systems is an increasing problem, especially for native fishes in the San Francisco
Estuary and Delta (SFE-D). Addressing these losses depends on understanding trophodynamics in the food web that supports threatened
species. We quantified the role of microzooplankton (heterotrophic–mixotrophic protists <200 μm) in the food web of the upper
SFE-D. We sampled protist plankton abundance and composition at two sites (Suisun Bay and Grizzly Bay) approximately monthly
from February 2004 to August 2005 and conducted dilution experiments during spring and summer of both years in Suisun Bay.
Heterotrophs dominated the protist community in Suisun Bay and Grizzly Bay, particularly in the <20 μm size range, and peaks
in protistan microzooplankton biomass were associated with high phytoplankton biomass. In both years, microzooplankton grazing
rates were high (0.5–0.7 day−1) during the spring and lower (~0.2 day−1) during summer. Phytoplankton growth rates peaked in April 2004 (~0.7 day−1) but were much lower (<0.1 day−1) in spring 2005, despite relatively high abundance. Thus, microzooplankton grazing consumed as much as 73% of phytoplankton
standing stock during spring and ~15% of standing stock during summer of both years. Combined with earlier results, we conclude
that microzooplankton can be important mediators of carbon and energy flow in the upper SFE-D and may be a “source” to the
metazoan food web. 相似文献
3.
The role of the microzooplankton community in regulating phytoplankton biomass was examined across a gradient from a river-dominated
estuary to an oceanic-influenced coastal zone. Three stations located along a salinity gradient from the central region of
Mobile Bay to 10 km off the coast were sampled from May 1994 to August 1995. Microzooplankton herbivory rates on phytoplankton
and microzooplankton excretion of nitrogen derived from phytoplankton were estimated using the dilution technique. Microzooplankton
grazing rates (range of station means=0.57–1.10 d−1) and phytoplankton growth rates (0.70–1.62 d−1) both increased across the salinity gradient from the bay station to the offshore station. However, the percent of primary
production grazed per day was highest at the bay station (mean=83%) and decreased to a low at the offshore station (mean=64%).
Excretion of phytoplankton-derived nitrogen by the microzooplankton was greatest at the bay and bay mouth stations. Excreted
nitrogen could potentially supply 39%, 29%, and 20% of phytoplankton nitrogen demand at the bay, bay mouth, and offshore stations,
respectively. These results support the idea that herbivorous microzooplankton are important in mediating nitrogen flow to
both lower and higher trophic levels. *** DIRECT SUPPORT *** A01BY085 00012 相似文献
4.
M. C. Murrell R. S. Stanley E. M. Lores G. T. DiDonato D. A. Flemer 《Estuaries and Coasts》2002,25(1):19-29
Microzooplankton dilution grazing experiments were conducted with water collected from Pensacola Bay, Florida (USA) on 12
dates at 2 sites. Statistically significant grazing rates were observed in 22 of 24 experiments. Grazing rates in Upper Bay
and Lower Bay were similar averaging 0.54 and 0.51 d−1, respectively. Phytoplankton growth rates were also similar at the two sites, averaging 1.02 and 1.00 d−1 at Upper Bay and Lower Bay, respectively. Phytoplankton growth rates usually exceeded grazing rates by about a factor of
two, though microzooplankton grazing represented a significant mortality for phytoplankton. The literature suggests a linkage
between phytoplankton growth and microzooplankton grazing that spans a wide variety of aquatic environments. While individual
growth and grazing rates were variable, growth frequently exceeded grazing by about two-fold. This implies that the role of
microzooplankton is similar across a wide variety of aquatic systems. 相似文献
5.
Phytoplankton Biomass and Production in Subtropical Hong Kong Waters: Influence of the Pearl River Outflow 总被引:1,自引:0,他引:1
Alvin Y. T. Ho Jie Xu Kedong Yin Yuelu Jiang Xiangcheng Yuan Lei He Donald M. Anderson Joseph H. W. Lee Paul J. Harrison 《Estuaries and Coasts》2010,33(1):170-181
The size-fractionated phytoplankton biomass and primary production were investigated in four contrasting areas of Hong Kong
waters in 2006. Phytoplankton biomass and production varied seasonally in response to the influence of the Pearl River discharge.
In the dry season, the phytoplankton biomass and production were low (<42 mg chl m−2 and <1.8 g C m−2 day−1) in all four areas, due to low temperatures and dilution and reduced light availability due to strong vertical mixing. In
contrast, in the wet season, in the river-impacted western areas, the phytoplankton biomass and production increased greater
than five-fold compared to the dry season, especially in summer. In summer, algal biomass was 15-fold higher than in winter,
and the mean integrated primary productivity (IPP) was 9 g C m−2 day−1 in southern waters due to strong stratification, high temperatures, light availability, and nutrient input from the Pearl
River estuary. However, in the highly flushed western waters, chl a and IPP were lower (<30 mg m−2 and 4 g C m−2 day−1, respectively) due to dilution. The maximal algal biomass and primary production occurred in southern waters with strong
stratification and less flushing. Spring blooms (>10 μg chl a L−1) rarely occurred despite the high chl-specific photosynthetic rate (mostly >10 μg C μg chl a
−1 day−1) as the accumulation of algal biomass was restricted by active physical processes (e.g., strong vertical mixing and freshwater
dilution). Phytoplankton biomass and production were mostly dominated by the >5-μm size fraction all year except in eastern
waters during spring and mostly composed of fast-growing chain-forming diatoms. In the stratified southern waters in summer,
the largest algal blooms occurred in part due to high nutrient inputs from the Pearl River estuary. 相似文献
6.
We measured seasonal variations in microzooplankton grazing in Long Island Sound (LIS) and San Francisco Bay (SFB). There
was consistent evidence of nutrient limitation in LIS, but not SFB. We found higher chlorophyll a concentrations in LIS compared with SFB. In spite of differences in phytoplankton, there were no differences in microzooplankton
abundance (summer: LIS, 12.4 ± 1.8 × 103 indiv. L−1; SFB, 14.1 ± 3.0 × 103 indiv. L−1), biomass (summer: LIS, 30.4 ± 5.0 μg C L−1; SFB, 26.3 ± 5.9 μg C L−1), or grazing rates (summer: LIS, 0.66 ± 0.19 day−1; SFB, 0.65 ± 0.18 day−1) between the two estuaries. In common with many other investigators, we found many instances of saturated as well as insignificant
grazing. We suggest that saturation in some cases may result from high particle loads in turbid estuarine systems and that
insignificant grazing may result from extreme saturation of the grazing response due to the need to process non-food particles. 相似文献
7.
Yongsik Sin Bonggil Hyun Quang-Dung Bach Sungryull Yang Chul Park 《Estuaries and Coasts》2012,35(3):839-852
Temporal and spatial variations in phytoplankton in Asan Bay, a temperate estuary under the influence of monsoon, were investigated
over an annual cycle (2004). Phytoplankton blooms started in February (>20 μg chl l−1) and continued until April (>13 μg chl l−1) during the dry season, especially in upstream regions. The percentage contribution of large phytoplankton (micro-sized)
was high (78–95%) during the blooms, and diatoms such as Skeletonema costatum and Thalassiosira spp. were dominant. The precipitation and freshwater discharge from embankments peaked and supplied nutrients into the bay
during the monsoon event, especially in July. Species that favor freshwater, such as Oscillatoria spp. (cyanobacteria), dominated during the monsoon period. The phytoplankton biomass was minimal in this season despite nutrient
concentrations that were relatively sufficient (enriched), and this pattern differed from that in tropical estuaries affected
by monsoon and in temperate estuaries where phytoplankton respond to nutrient inputs during wet seasons. The flushing time
estimated from the salinity was shorter than the doubling time in Asan Bay, which suggests that exports of phytoplankton maximized
by high discharge directly from embankments differentiate this bay from other estuaries in temperate and tropical regions.
This implies that the change in physical properties, especially in the freshwater discharge rates, has mainly been a regulator
of phytoplankton dynamics since the construction of embankments in Asan Bay. 相似文献
8.
Paulo C. Abreu Edna Granéli Clarisse Oderbrecht Dione Kitzmann Luis A. Proença Charrid Resgalla 《Estuaries and Coasts》1994,17(3):575-584
An enclosure experiment in the Patos Lagoon estuary, southern Brazil (32°S, 52°W) investigated the response of phytoplankton to the enhancement of mesozooplankton and fish abundance. Addition of nutrients (NO3 ? and PO4 ?) stimulated the growth of 3–20 μm diameter phytoplankton, especially the diatomCylindrotheca closterium, which, in turn, was heavily grazed by the dominant mesozooplankter, the copepodAcartia tonsa. Acartia did not consume small (2–3 μm) autotrophic flagellates and the cyanobacteriaAnabaena sp., despite their high cell number. Largest grazing ofC. closterium by the copepod occurred only after a decrease of ciliate abundance. The addition of mesozooplankton did not change the levels of primary production, but it significantly increased the phytoplankton assimilation number. Highest chlorophylla concentrations were measured in enclosures stocked with juveniles of the fishXenomelaniris brasiliensis. The large phytoplankton biomass and low mesozooplankton abundance found in this treatment indicates an, effective predator-mediated action on the phytoplankton community. 相似文献
9.
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
10.
A 16-yr (1985–2000) time series of calanoid copepod (Acartia tonsa andEurytemora affinis) abundance in the upper Chesapeake Bay was examined for links to winter weather variability. A synthesis of sea level pressure
data revealed ten dominant, winter weather patterns. Weather patterns differed in frequency of occurrence as well as associated
precipitation and temperature. The two dominant copepod species responded differently to winter weather variability.A. tonsa abundance showed little response to winter weather and did not vary in abundance during wet or dry springs.E affinis responded strongly to winter weather patterns that produced springs with high freshwater discharge and low salinities. During
wet springs,E. affinis abundance increased overall and its area of dominance extended further down estuary. The different response of the two species
is likely related to several factors including residence time, development time, salinity tolerance, food limitation, and
life history strategy. Important fish species that rely on zo oplankton as food resources were also related to winter weather
variability and spring zooplankton abundance.Morone saxatilis (striped bass) andAnchoa mitchilli (bay anchovy) juvenile indices were positively and negatively correlated toE. affinis abundance, respectively. *** DIRECT SUPPORT *** A02BY003 00004 相似文献
11.
Michael J. Durako Piotr Kowalczuk Michael A. Mallin William J. Cooper Jason J. Souza David H. Wells 《Estuaries and Coasts》2010,33(6):1430-1441
Surface water optical characteristics, nutrients, and planktonic chlorophyll a concentrations were analyzed in the Cape Fear River (CFR) plume over a 2-year period. CFR discharge during the dry year (109 ± 105 m3s−1) was only 25% of the wet year discharge (429 ± 337 m3s−1). Partitioning the contributions of phytoplankton pigments, non-pigmented particles, and colored dissolved organic matter
(CDOM) to the absorption of photosynthetically active radiation (PAR) indicated that CDOM was the dominant contributor to
PAR absorption. Particulate absorption was relatively greater during the dry year. Pigment absorption was minor and varied
little among stations or between years. Chlorophyll a concentrations were reduced at the most plume-influenced stations during the wet year, despite lower turbidity and higher
nitrate concentrations. Ammonium and orthophosphate concentrations were not different between years. CDOM absorption [a
CDOM
(412)] ranged from 0.05 to 8.25 m−1 with highest values occurring near the CFR mouth. Our results suggest that for coastal ecosystems with significant blackwater
river inputs, CDOM may exert a major limiting influence over near-shore primary production. 相似文献
12.
Edward J. Buskey Hongbin Liu Christopher Collumb Jose Guilherme F. Bersano 《Estuaries and Coasts》2001,24(3):337-346
The Laguna Madre has experienced a persistent bloom ofAureoumbra lagunensis for over eight years. The persistence of this bloom may be due in part to the often hypersaline conditions in Laguna Madre (40–60 psu) that favor the growth ofA. lagunensis. Above-normal rainfall in the fall of 1997 reduced the salinities in Baffin Bay from >40 to<20 psu.A. lagunensis cell densities dropped from>106 cells ml−1 in July 1997 to c. 200 cells ml−1 in January 1998. During this time of low brown tide density, phytoplankton biomass generally remained high and the Laguna Madre experienced successive blooms of diatoms (Rhizosolenia spp.) and cyanobacteria. Hypersaline conditions returned in 1998 and brown tide densities increased to>0.5 × 106 cells ml−1 by summer. The extraordinary persistence of the brown tide and the unusual sequence of intense blooms may be related in part to the reduction of zooplankton populations. Microzooplankton populations declined following the above-normal rain in the fall of 1997; populations did not recover until fall 1998. Copepod populations also declined sharply and remained low in Laguna Madre, but recovered by summer 1998 in Baffin Bay. Dilution experiments indicated that microzooplankton grazing and phytoplankton growth were usually balanced when measured during our cruises. The rapid recovery of theA. lagunensis bloom suggests that this alga may be a more resilient component of the Laguna Madre flora than previously suspected. 相似文献
13.
Efeturi U. Oghenekaro Paulinus Chigbu Ozuem F. Oseji Kam W. Tang 《Estuaries and Coasts》2018,41(2):495-506
Maryland Coastal Bays differ in hydrography from river-dominated estuaries because of limited freshwater inflow from tributary creeks and more marine influence. Consequently, the copepod community structure may be different from that of the coastal ocean and river-dominated estuaries in the mid-Atlantic region. A 2-year study was conducted to describe copepod species composition and seasonal patterns in abundance and factors influencing the community structure. Seven copepod genera, Acartia, Centropages, Pseudodiaptomus, Parvocalanus, Eurytemora, Oithona, and Temora, in addition to harpacticoids were found. The copepod community was dominated by Acartia spp. (64%), followed by Centropages spp. (30%), unlike in river-dominated estuaries in the region where the copepod community is usually dominated by Acartia spp. followed by Eurytemora affinis. Acartia tonsa was the most abundant in summer and fall whereas Centropages spp., Temora sp., Oithona similis, E. affinis, and harpacticoids were most abundant in winter and early spring. Parvocalanus crassirostris and Pseudodiaptomus pelagicus were present in fall and winter but at relatively low densities. The highest mean density of copepods occurred in winter 2012 (36,437 m?3) and the lowest in spring 2013 (347 m?3). Low densities occurred through early summer (614 m?3) coinciding with peak spawning by bay anchovy (Anchoa mitchilli). Bottom-up control via low phytoplankton biomass coupled with top-down control by ctenophores (Mnemiopsis sp.), mysids (Neomysis americana), and bay anchovy was probably responsible for the low copepod densities in spring and early summer. Temperature and salinity were also important factors that influenced the seasonal patterns of copepod species occurrence. The observed seasonal differences in the abundance of copepods have important implications for planktivorous fishes as they may experience lower growth rates and survival due to food limitation in spring/early summer when copepod densities are relatively low than in late summer/fall when copepod abundance is higher. 相似文献
14.
Joanna K. York George B. McManus Wim J. Kimmerer Anne M. Slaughter Toni R. Ignoffo 《Estuaries and Coasts》2014,37(3):576-588
We investigated trophic relationships involving microzooplankton in the low salinity zone of the San Francisco Estuary (SFE) as part of a larger effort aimed at understanding the dynamics of the food web supporting the endangered delta smelt, Hypomesus transpacificus. We performed 14 cascade experiments in which we manipulated the biomass of a copepod (Limnoithona tetraspina, Pseudodiaptomus forbesi, or Acartiella sinensis) and quantified responses of lower trophic levels including bacterioplankton, phytoplankton, and microzooplankton. Microzooplankton comprised a major food source for copepods; 9 out of 14 experiments showed removal of at least one group of microzooplankton by copepods. In contrast, the impact of copepods on phytoplankton was indirect; increased copepod biomass led to greater growth of phytoplankton in 3 of 14 experiments. Estimated clearance rates on microzooplankton were 4 mL day?1 for L. tetraspina and 2–6 mL day?1 for P. forbesi, whereas A. sinensis consumed mainly copepod nauplii. Complex trophic interactions, including omnivory, among copepods, microzooplankton, and different components of the phytoplankton likely obscured clear trends. The food web of the SFE is probably less efficient than previously thought, providing poor support to higher trophic levels; this inefficient food web is almost certainly implicated in the continuing low abundance of fishes, including the delta smelt that use the low salinity zone of the San Francisco Estuary. 相似文献
15.
The effects of advection, dispersion, and biological processes on nitrogen and phytoplankton dynamics after a storm event
in December 2002 are investigated in an estuary located on the northern New South Wales coast, Australia. Salinity observations
for 16 d after the storm are used to estimate hydrodynamic transports for a one-dimensional box model. A biological model
with nitrogen limited phytoplankton growth, mussel grazing, and a phytoplankton mortality term is forced by the calculated
transports. The model captured important aspects of the temporal and spatial dynamics of the bloom. A quantitative analysis
of hydrodynamic and biological processes shows that increased phytoplankton biomass due to elevated nitrogen loads after the
storm was not primarily regulated by advection or dispersion in spite of an increase in river flow from <1 to 928×103 m3 d−1. Of the dissolved nitrogen that entered the surface layer of the estuary in the 16 d following the storm event, the model
estimated that 28% was lost through exchange with the ocean or bottom layers, while 15% was removed by the grazing of just
one mussel species,Xenostrobus securis, on phytoplankton, and 50% was lost through other biological phytoplankton loss processes.X. securis grazing remained an important loss process even when the estimated biological parameters in the model were varied by factors
of ± 2. The intertidal mangrove pneumatophore habitat ofX. securis allows filtering of the upper water column from the lateral boundaries when the water column is vertically stratified, exerting
top-down control on phytoplankton biomass. 相似文献
16.
Gabriella Jackson Richard Zingmark Alan J. Lewitus Raphael G. Tymowski Joyce Stuckey 《Estuaries and Coasts》2006,29(6):1212-1221
Epiphytic microbial biomass (as chlorophylla) was measured monthly in North Inlet Estuary, South Carolina, for 16 months on spatially distinct stem sections (bottom and
middle) of dead and livingSpartina alterniflora growth forms (tall, medium, and short) exposed at low tide. The highest biomass was located on the bottom section of tall
plants, presumably due to their relatively longer contact with creek water and associated phytoplankton, and their closer
proximity to marsh sediments with associated benthic microalgae, both recruitment sources for epiphytes. Dead plants left
standing from the previous year’s growth cycle had higher epiphytic biomass than living plants, which occurred mostly in late
spring through fall. Epiphytic biomass was highest in the winter (mean of 1.77 mg chla (m2 marsh)−1) and lowest in the summer (mean of 0.34 mg chla (m2 marsh)−1). Because phytoplankton andSpartina production are lowest in the winter, the results emphasize the relative importance of epiphytes to growth of herbivores in
this season. 相似文献
17.
K. G. Sellner D. C. Brownlee M. H. Bundy S. G. Brownlee K. R. Braun 《Estuaries and Coasts》1993,16(4):859-872
During summer, bloom-forming cyanobacteria, including Anacystis, Aphanizomenon, and Microcystis aeruginosa, dominate tidal-fresh waters of the upper Potomac River estuary with densities exceeding 108 cells l?1. In an attempt to determine the importance of these high cyanobacteria densities to planktonic herbivory in the system, short-term grazing experiments were conducted in July and August 1987. Using size-fractionated river phytoplankton assemblages, zooplankton grazing rates were determined for dominant or subdominant planktonic microzooplankton and mesozooplankton feeding on 14C-labeled river assemblages, 14C-labeled river assemblages enriched with unlabeled cyanobacteria, and unlabeled river assemblages enriched with 14C-labeled cyanobacteria. Grazing rates were estimated for the rotifers Polyarthra remata, Hexarthra mira, Asplanchna brightwelli, Brachionus angularis, Epiphanes sp., Trichocerca similis, and the cyclopoid copepod Cyclops vernalis. Neither rotifers nor the copepod grazed heavily on Microcystis. Rotifer grazing rates on labeled cyanobacteria ranged from 4 to 1,650 nl· [individual · h]?1 while copepod rates ranged from undetectable to 135 μl · [copepod · h]?1. Grazing rates on labeled river phytoplankton assemblages were 4–100 times higher than noted for zooplankton feeding on cyanobacteria. The addition of the colonial alga to labeled river phytoplankton assemblages resulted in mixed zooplankton responses, that is, lower and higher grazing rates than observed on river assemblages with no added cyanobacteria. Total zooplankton demand for cyanobacteria and river phytoplankton assemblages was estimated for the study period July–August 1987. Rotifer plus C. vernalis herbivory would have removed 1–5% and 49%, respectively, of the standing stock of the two autotroph pools each day. Literature-derived clearance rates for Bosmina indicate, however, that herbivory by this cladoceran could increase demand to 24% and 60%, respectively, in bloom and nonbloom assemblages. These data suggest that the majority of cyanobacterial production remains ungrazed and may be transported to the lower estuary for salinity-induced aggregation and sedimentation. 相似文献
18.
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
19.
Michael C. Murrell James D. Hagy Emile M. Lores Richard M. Greene 《Estuaries and Coasts》2007,30(3):390-402
The relationships between phytoplankton productivity, nutrient distributions, and freshwater flow were examined in a seasonal
study conducted in Escambia Bay, Florida, USA, located in the northeastern Gulf of Mexico. Five sites oriented along the salinity
gradient were sampled 24 times over the 28-mo period from 1999 to 2001. Water column profiles of temperature and salinity
were measured along with surface chlorophyll and surface inorganic nutrient concentrations. Primary productivity was measured
at 2 sites on 11 dates, and estimated for the remaining dates and sites using an empirical regression model relating phytoplankton
net production to the product of chlorophyll, euphotic zone depth, and daily solar insolation. Freshwater flow into the system
varied markedly over the study period with record low flow during 2000, a flood event in March 2001, and subsequent resumption
of normal flow. Flushing times ranged from 1 d during the flood to 20 d during the drought. Freshwater input strongly affected
surface salinity distributions, nutrient flux, chlorophyll, and primary productivity. The flood caused high turbidity and
rapid flushing, severely reducing phytoplankton production and biomass accumulation. Following the flood, phytoplankton biomass
and productivity sharply increased. Analysis of nutrient distributions suggested Escambia Bay phytoplankton alternated between
phosphorus limitation during normal flow and nitrogen limitation during low flow periods. This study found that Escambia Bay
is a moderately productive estuary, with an average annual integrated phytoplankton production rate of 290 g C m−2 yr−1. 相似文献
20.
Analysis of 6 yr of monthly water quality data was performed on three distinct zones of Florida Bay: the eastern bay, central bay, and western bay. Each zone was analyzed for trends at intra-annual (seasonal), interannual (oscillation), and long-term (monotonic) scales. the variables TON, TOC, temperature, and TN∶TP ratio had seasonal maxima in the summer rainy season; APA and Chla, indicators of the size and activity of the microplankton tended to have maxima in the fall. In contrast, NO3 −, NO2 −, NH4 +, turbidity, and DOsat, were highest in the winter dry season. There were large changes in some of the water quality variables of Florida Bay over the study period. Salinity and TP concentrations declined baywide while turbidity increased dramatically. Salinity declined in the eastern, central, and western Florida Bay by 13.6‰, 11.6‰, and 5.6‰, respectively. Some of the decrease in the eastern bay could be accounted for by increased freshwater flows from the Everglades. In contrast to most other estuarine systems, increased runoff may have been partially responsible for the decrease in TP concentrations as input concentrations were 0.3–0.5 μM. Turbidity in the eastern bay increased twofold from 1991 to 1996, while in the central and western bays it increased by factors of 20 and 4, respectively. Chla concentrations were particularly dynamic and spatially heterogeneous. In the eastern bay, which makes up roughly half of the surface area of Florida Bay, Chla declined by 0.9 μg l−1 (63%). The hydrographically isolated central bay zone underwent a fivefold increase in phytoplankton biomass from 1989 to 1994, then rapidly declined to previous levels by 1996. In western Florida Bay there was a significant increase in Chla, yet median concentrations of Chla in the water column remained modest (∼2 μg l−1) by most estuarine standards. Only in the central bay did the DIN pool increase substantially (threefold to sixfold). Notably, these changes in turbidity and phytoplankton biomass occurred after the poorly-understood seagrass die-off in 1987. It is likely the death and decomposition of large amounts of seagrass biomass can at least partially explain some of the changes in water quality of Florida Bay, but the connections are temporally disjoint and the process indirect and not well understood. 相似文献