Characterization of plankton from the Galveston estuary (original) (raw)
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Estuarine, Coastal and Shelf Science, 2011
Identification of the limiting nutrient(s) is a requirement for the rational management of eutrophication. Here, we present the first experimental analysis of nutrient limitation of phytoplankton growth and its seasonal variation in the Guadiana estuary (SE Portugal-SW Spain). Ten microcosm experiments were performed during 2005 and 2008, using water samples collected in the freshwater tidal zone of the Guadiana estuary. Nitrate, phosphate and silicate were added in a single pulse, alone and in combinations. Experimental treatments were incubated for 4 days under controlled laboratory conditions. Phytoplankton response to nutrient enrichment was evaluated through changes in biomass (Chla), and abundance of specific phytoplankton groups.
PLOS ONE, 2016
Nitrogen availability and form are important controls on estuarine phytoplankton growth. This study experimentally determined the influence of urea and nitrate additions on phytoplankton growth throughout the growing season (March 2012, June 2011, August 2011) in a temperate, eutrophied estuary (Neuse River Estuary, North Carolina, USA). Photopigments (chlorophyll a and diagnostic photopigments: peridinin, fucoxanthin, alloxanthin, zeaxanthin, chlorophyll b) and microscopy-based cell counts were used as indicators of phytoplankton growth. In March, the phytoplankton community was dominated by Gyrodinium instriatum and only fucoxanthin-based growth rates were stimulated by nitrogen addition. The limited response to nitrogen suggests other factors may control phytoplankton growth and community composition in early spring. In June, inorganic nitrogen concentrations were low and stimulatory effects of both nitrogen forms were observed for chlorophyll a-and diagnostic photopigment-based growth rates. In contrast, cell counts showed that only cryptophyte and dinoflagellate (Heterocapsa rotundata) growth were stimulated. Responses of other photopigments may have been due to an increase in pigment per cell or growth of plankton too small to be counted with the microscopic methods used. Despite high nitrate concentrations in August, growth rates were elevated in response to urea and/or nitrate addition for all photopigments except peridinin. However, this response was not observed in cell counts, again suggesting that pigment-based growth responses may not always be indicative of a true community and/or taxa-specific growth response. This highlights the need to employ targeted microscopy-based cell enumeration concurrent with pigmentbased technology to facilitate a more complete understanding of phytoplankton dynamics in estuarine systems. These results are consistent with previous studies showing the seasonal importance of nitrogen availability in estuaries, and also reflect taxa-specific responses nitrogen availability. Finally, this study demonstrates that under nitrogen-limiting conditions, the phytoplankton community and its various taxa are capable of using both urea and nitrate to support growth.
We have previously shown that primary productivity in San Francisco Bay, USA, is highly correlated with phytoplankton biomass B (chlorophyll a concentration) and an index of light avallability in the photic zone, 2, I, (photic depth times surface irradiance). To test the generality of this relation, we compiled data from San Francisco Bay and 5 other USA estuarine systems (Neuse and South Rivers, Puget Sound, Delaware Bay and Hudson River Plume), and regressed daily produclvity J ' P (mg C m-2 d-') against the composite parameter B Z, I,. Regressions for each estuary were significant and typically over 80 % of the varialon in P was correlated with variations in B Z,I,. Moreover, the pooled data (n = 211) from 4 estuaries where methodologies were comparable fell along one regression line ( r 2 = 0.82), indicating that primary productivity can be estimated in a diversity of estuarine waters from simple measures of phytoplankton biomass and hght availability. This implies that physiological variabhty (e. g. responses to variations in nutrient availabhty, temperature, sahnity, photoperiod) is a secondary control on phytoplankton production in nutrient-rich estuaries, and that one empirical function can be used to estimate seasonal variations in productivity or to map productivity along estuarine gradients of phytoplankton biomass and turbidity.
Journal of Aquaculture & Marine Biology, 2019
Small, shallow estuaries can be highly vulnerable to land use changes, eutrophication and habitat loss but are understudied with respect to their larger counterparts. Where they are monitored, the descriptors of their environmental status are typically chlorophyll a as a proxy for phytoplankton abundance and nutrient concentration as a presumed driver of the phytoplankton community. We present data from a shallow estuary, Weeks Bay, Alabama (USA), that demonstrates that chlorophyll a and nutrient concentrations are inadequate descriptors of ecological state. Weeks Bay had relatively high nutrient concentrations (86– 169µM total nitrogen and 1.0–5.2µM total phosphorus) and highly variable chlorophyll a concentrations (2.2–160.5μgL-1). The variability in chlorophyll a was most highly correlated with nutrient levels and river discharge. There was no relationship between chlorophyll a and community composition. Two of three maxima in chlorophyll a (>100μgL-1) were caused by non-toxic chlorophytes and diatoms; the third was dominated by potentially toxic raphidophyte Heterosigma akashiwo. The phytoplankton were diverse even at the class level and community composition varied on both annual and inter-annual scales. The best overall descriptor of phytoplankton composition was the annual cycle in temperature, but inter-annual variability was correlated with hydrology. In the winter, dominance by dinoflagellates, including several taxa that form harmful algal blooms, was correlated with low river discharge, low turbidity and high zooplankton numbers, while dominance by diatoms was correlated with high and variable river discharge and high turbidity. In the summer, dominance by cryptophytes versus diatoms was consistent with changes in groundwater discharge. The dominance of harmful algal bloom taxa vs non-toxic ones could not be inferred from chlorophyll a and/or nutrient concentrations.
Limnology and Oceanography, 1998
In North Inlet, a tidally dominated salt-marsh estuary near Georgetown, South Carolina, the summer chlorophyll maximum correlates with an annual peak in ambient NH,+ concentration. This relationship suggests that phytoplankton population growth during the summer bloom is limited by factors other than nutrient supply, because NH,+ is the major inorganic nitrogen source available to phytoplankton in North Inlet, and phosphorus should not be limiting (N : P is generally -7). We tested the hypothesis that phytoplankton population growth during the bloom was controlled by grazing. Natural samples were incubated in treatments designed to differentiate between nutrient and grazing effects, and time-course changes in total phytoplankton biomass and phototrophic community composition were followed. Marked seasonal differences were observed in the relative contribution of pica-, nano-, or microplankton to phytoplankton community biomass, as well as the mechanisms controlling phytoplankton population growth. During the summer bloom, phototrophic picoplankton (mostly Synechococcus spp.) and nanoplankton (mostly flagellates) were relatively abundant, and phytoplankton population growth was unaffected by NH,' addition, but was greatly stimulated by dilution that reduced microzooplankton grazing pressure. During the winter, when diatoms dominated the phytoplankton, the response to dilution was relatively minor, while NH,' addition significantly stimulated the growth of various phytoplankton groups and total chlorophyll. The results indicate a seasonal transition in microbial food-web trophic structure and regulation in North Inlet estuary. During the summer, microzooplankton grazing is an important factor regulating phytoplankton population growth during the nanoflagellate-prevalent bloom, whereas in the winter, a diatom-dominated community is limited by nutrient supply.
Estuaries and Coasts, 2013
Seasonal wind-driven upwelling along the U.S. West Coast supplies large concentrations of nitrogen to surface waters that drives high primary production. However, the influence of coastal upwelled nutrients on phytoplankton productivity in adjacent small estuaries and bays is poorly understood. This study was conducted in Drakes Estero, California, a low inflow estuary located in the Point Reyes National Seashore and the site of an oyster mariculture facility that produces 40 % of the oysters harvested in California. Measurements of nutrients, chlorophyll a , phytoplankton functional groups, and phytoplankton carbon and nitrogen uptake were made between May 2010 and June 2011. A sea-to-land gradient in nutrient concentrations was observed with elevated nitrate at the coast and higher ammonium at the landward region. Larger phytoplankton cells (>5 μm diameter) were dominant within the outer and middle Estero where phytoplankton primary productivity was fueled by nitrate and f-ratios were >0.5; the greatest primary production rates were in the middle Estero. Primary production was lowest within the inner Estero, where smaller phytoplankton cells (<5 μm) were dominant, and nitrogen uptake was dominated by ammonium. Phytoplankton blooms occurred at the outer and middle Estero and were dominated by diatoms during the spring and dryupwelling seasons but dinoflagellates during the fall. Small flagellated algae (>2 μm) were dominant at the inner Estero where no blooms occurred. These results indicate that coastal nitrate and phytoplankton are imported into Drakes Estero and lead to periods of high new production that can support the oyster mariculture; a likely scenario also for other small estuaries and bays.
Lateral variation in the production and fate of phytoplankton in a partially stratified estuary
Marine Ecology Progress Series, 1986
It is generally believed that the high productivity of many estuaries is a consequence of both allochthonous nutrient inputs and autochthonous recycling of nutrients among producers and decomposers of organic matter. However, the mechanisms by which nutrients are recycled between sources and sinks are not clear We have documented time-dependent variations in density structure along a transect normal to the main axis of Chesapeake Bay which may be important in this regard. These variations influenced lateral distributions of dissolved inorganic nutrients, oxygen, chlorophyll a, and bacterioplankton and appeared to be responsible for high phytoplankton production over the flanks of the main channel relative to production over the channel. Vertical and seasonal variations in bacterial abundance were correlated with phytoplankton biomass, and increases in bacterial abundance were related to the development of phytoplankton bloon~s with lags of 0 to 6 d. Bacterial biomass and production were high throughout the study period, averaging 20 O/ O to over 50 O/ O of phytoplankton biomass and production, respectively. Absolute levels of bacterial abundance were among the highest reported and suggest that bacteria are responsible for a large function of the carbon flux in Chesapeake Bay. Relations among phytoplankton production, bacterial abundance and sediment trap collections indicate that variations in density structure reflect a transverse circulation which may explain how nutrients regenerated below the pycnocline are rapidly recycled into the euphotic zone above. This could be an important mechanism by which river-borne nutrient inputs during spring are coupled to high phytoplankton production during summer.
Distributions of phytoplankton in Tampa Bay Estuary, USA 20022003
Bulletin of Marine …, 2007
Phytoplankton was observed from April 2002 to April 2003 in Tampa Bay to determine spatial and temporal patterns of composition and abundance. Picoplankton cyanobacteria were numerically dominant at all sites within the bay, but due to their small size were infrequently dominant in terms of biomass (i.e., biovolume). The small-celled diatoms Skeletonema and Pseudo-nitzschia were the next most numerically abundant taxa throughout the bay. In terms of biovolume, the dominant species varied spatially and temporally. Diatoms dominated in the lower and midbay, with the relative abundance of large-celled diatoms, such as Dactyliosolen fragilissimus, higher in the lower bay (near the outlet to the Gulf of Mexico) than in the mid-bay region. In the upper bay, dinoflagellates were most often dominant. During the summer and fall, a bloom of the potentially toxic dinoflagellate Pyrodinium bahamense var bahamense was observed in the upper bay, with cell densities up to 350 cells L -1 . Our observations are consistent with the hypothesis that different subbasins of the bay support different phytoplankton assemblages. From a historical perspective, the most dramatic distinctions between past records and our results were the previous absence of Pyrodinium bahamense var. bahamense blooms, and the first report of picoplankton.
Journal of Plankton Research, 2002
Estuarine phytoplankton are subject to many interacting and competing stressors and they must compete for available resources to maximize their photosynthetic rates and growth (Petersen et al., 1997). Characterizing the physiological response of phytoplankton to interacting environmental variables is essential to anticipating changes that might occur due to anthropogenic disturbances. This is fundamental to the formation of effective coastal nutrient management practices (Cloern, 1996). These humaninduced impacts include enhanced nutrient loading (Hobbie and Smith, 1975; Paerl et al., 1995), modified nutrient ratios (Quian et al., 2000), altered flow regimes (Rudek et al., 1991), and enhanced ultraviolet (UV) radiation (Hader and Worrest, 1991). Given this, developing a non-intrusive means to characterize the physiological state of phytoplankton communities and to predict their response to interacting anthropogenic disturbances has long been a goal of environmental scientists. Work over the last two decades by plant scientists and oceanographers (Kolber et al., 1988; Schreiber et al., 1995) has demonstrated the utility of chlorophyll a (chl a) fluorescence measurements as a sensitive indicator of the physiological state of phytoplankton populations under erratic conditions.