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Global change has increased inorganic nitrogen (N) and dissolved organic carbon (DOC; i.e., "browning") inputs to northern hemisphere boreal lakes. However, we do not know how phytoplankton in nutrient poor lake ecosystems of different DOC concentration respond to increased N availability. Here, we monitored changes in phytoplankton production, biomass and community composition in response to whole lake inorganic N fertilization in six boreal unproductive Swedish lakes divided into three lake pairs (control, N enriched) at three DOC levels (low, medium, high), with one reference year (2011) and 2 impact yr (2012, 2013). We found that phytoplankton biomass and production decreased with DOC concentration before N fertilization. Further, phytoplankton community composition also differed with respect to DOC, with a dominance of non-flagellated autotrophs at low DOC towards an increasing dominance of flagellated autotrophs with increased lake DOC concentration. The N fertilization increased phytoplankton biomass and production in all lakes, but did not affect phytoplankton community composition. However, the net response in biomass and production to N fertilization declined with increasing DOC, implying that the lake DOC concentration is critical in order to infer phytoplankton responses to N fertilization, and that the system switches from being primarily nutrient limited to becoming increasingly light limited with increased DOC concentration. In conclusion, our results show that browning will reduce phytoplankton production and biomass and influence phytoplankton community composition, whereas increased inorganic N loadings from deposition, forestry or other land use will primarily enhance phytoplankton biomass and production. Together, any change in the landscape that enhances inorganic N availability will increase phytoplankton production and biomass, but the positive effects of N will be much weaker or even neutralized in browner lakes as caused by light limitation.

Phosphorus sources contributing to phytoplankton blooms in a subtropical reservoir

San Francisco Bay has been considered an HNLC or HNLG (high nutrient low chlorophyll or low growth) region with nonlimiting concentrations of inorganic nutrients yet low standing stocks of phytoplankton. Most of the studies leading to this conclusion come from the South Bay and little is known about nutrient processes and phytoplankton productivity in the northern and central parts of the estuary. Data collected over 3 yr (1999–2003) in Suisun, San Pablo, and Central Bays describe the availability of dissolved inorganic nitrogen (DIN), silicate, and phosphate and the seasonal variability in phytoplankton abundance. Rate measurements of fractionated nitrogen productivity provide the relative contributions of different forms of DIN (ammonium and nitrate) and different sized phytoplankton to the development of seasonal phytoplankton blooms. Regional differences in bloom dynamics are observed with Suisun Bay, the least saline, highest nutrient, most turbid region having less phytoplankton biomass and productivity than San Pablo and Central Bays, except in the abnormally wet spring of 2000. Spring blooms in San Francisco Bay are driven primarily by high rates of nitrate uptake by larger phytoplankton cells following a period of increased ammonium uptake that depletes the ambient ammonium. The smaller occasional fall blooms are apparently flueled mostly by ammonium uptake by small sized phytoplankton. The data suggest that the HNLC condition in the northern and central parts of San Francisco Bay is due primarily to light availability modulated by the interaction between ammonium and nitrate, and the relative amounts of the two forms of the DIN pool available to the phytoplankton.

The effects of calcite addition on two acidic Adirondack lakes were studied by investigators participating in the Lake Acidification Mitigation Project. Changes in phytoplankton biomass, productivity, and species composition were monitored during the ice-free period prior to and following lake treatment. Changes in water chemistry following limestone addition were largely restricted to the upper water column since calcite particles applied to the lake surface did not effectively penetrate the thermocline. Increased phytoplankton production and biomass were observed during the posttreatment period. Phytoplankton densities and rates of production were similar in both the neutralized (pH > 7.5) and acidic (pH < 5.5) portions of the water column; however, species composition was markedly different. The phytoplankton assemblage of the upper water column was largely comprised of chlorophytes and chrysophytes which had not been observed prior to treatment. In contrast, the deep-water assemblage comprised many of the same taxa that had been dominant during the pretreatment periodsss.

Spatial-temporal variations in phytoplankton primary production (PP) and biomass (B) were studied for a period of about one year, from July 1999 to July 2000. In addition, changes in corresponding environmental variables were examined. Sampling took place at two stations in Chwaka Bay, one located in mangrove areas, Station I, and the other in an open area, Station II. Although there were changes both with location and time, there were no clear seasonal trends. Generally, the phytoplankton biomass and primary production (mg C m-3 h-1) were higher at Station I than at Station II. However, specific production, that is, primary production normalized to phytoplankton biomass, PB (mg C (mg chl-a)-1 h-1) was higher at Station II than at Station I. No relationship could be found between phytoplankton biomass and the rate of primary production. These observations suggest that the presence of the mangrove ecosystem, and the processes therein, influenced the rate of phytoplankton primary production in the Mapopwe Creek, causing the differences between stations.

Spatial-temporal variations in phytoplankton primary production (PP) and biomass (B) were studied for a period of about one year, from July 1999 to July 2000. In addition, changes in corresponding environmental variables were examined. Sampling took place at two stations in Chwaka Bay, one located in mangrove areas, Station I, and the other in an open area, Station II. Although there were changes both with location and time, there were no clear seasonal trends. Generally, the phytoplankton biomass and primary production (mg C m-3 h-1) were higher at Station I than at Station II. However, specific production, that is, primary production normalized to phytoplankton biomass, PB (mg C (mg chl-a)-1 h-1) was higher at Station II than at Station I. No relationship could be found between phytoplankton biomass and the rate of primary production. These observations suggest that the presence of the mangrove ecosystem, and the processes therein, influenced the rate of phytoplankton primary production in the Mapopwe Creek, causing the differences between stations. Tanz. J. Sci. Vol. 28(2) 2002: 11-26

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 21:191-204 (2014) - DOI: https://doi.org/10.3354/ab00588 Impact of atypical ammonium concentrations on phytoplankton abundance and composition in fresh versus estuarine waters Mary Lou Esparza1,*, Ann E. Farrell1, Douglas J. Craig1, Curt Swanson1, Bhupinder S. Dhaliwal1, Gry Mine Berg2 1Central Contra Costa Sanitation District, 5019 Imhoff Place, Contra Costa, CA 94553, USA 2Applied Marine Sciences, 911 Center St, Santa Cruz, CA 95060, USA *Corresponding author: mesparza@centralsan.org ABSTRACT: The impact of atypically high ammonium (NH4+) concentrations delivered via treated wastewater effluent on phytoplankton community composition was investigated in a tidal slough connected with Suisun Bay in the northern part of San Francisco Bay. Input of effluent to a downstream location resulted in NH4+ concentrations of (mean ± SD) 1021 ± 380 µmol l-1, compared with 2.9 ± 1 µmol l-1 at a site further upstream, and 4.8 ± 1 µmol l-1 in Suisun Bay. Comparison of the diatom community at the downstream site in Pacheco Slough with that in Suisun Bay revealed a substantial overlap in species, including Cyclotella scaldensis, which dominated diatom species composition in both locations. The ratio of diatoms:other phytoplankton biomass (µmol3:µmol3) suggested that diatoms contributed a greater proportion of total phytoplankton community biomass at the downstream location (48.6 ± 87) versus in Suisun Bay (9.5 ± 1) or upstream (9.5 ± 8), and that diatoms can readily grow in the presence of NH4+ concentrations varying from 2 to 1350 µmol l-1. In the present investigation, species composition of the seeding population was found to be a more important predictor of final phytoplankton community composition than nutrient concentrations or ratios. KEY WORDS: Phytoplankton · Ammonium · N:P ratio · NH4+:NO3- ratio · Diatoms · Chlorophytes · San Francisco Estuary · Suisun Bay Full text in pdf format PreviousNextCite this article as: Esparza ML, Farrell AE, Craig DJ, Swanson C, Dhaliwal BS, Berg GM (2014) Impact of atypical ammonium concentrations on phytoplankton abundance and composition in fresh versus estuarine waters. Aquat Biol 21:191-204. https://doi.org/10.3354/ab00588 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 21, No. 3. Online publication date: September 03, 2014 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2014 Inter-Research.

The rapid physical changes affecting the Arctic Ocean alter the growth conditions of primary producers. In this context, a crucial question is whether these changes will affect the composition of phytoplankton communities, augment their productivity, and eventually enhance food webs. We combined satellite and model products with in situ datasets collected during fall and provide new insights into the response of phytoplankton biomass and production in the Canadian Arctic by comparing an interior shelf (Beaufort Sea) and an outflow shelf (Baffin Bay). Correlation analysis was used to distinguish between seasonal and interannual variability and revealed that most biological variables are responding to the interannual pressures of climate change. In southeast Beaufort Sea, a change in phytoplankton community composition occurred, with a significant increase in diatoms from 2% (2002) to 37% (2010–2011) of the total protist abundance. In 2011, photosynthetic picoeukaryotes were twice as abundant as in 2002. For these two phytoplankton groups, abundance was correlated with the duration of the open‐water period, which also increased and affected vertical stratification and sea‐surface temperature. In contrast, there was a sharp decline in centric diatom abundance as well as in phytoplankton biomass and production in northern Baffin Bay over the years considered. These decreases were linked to changes in seasonal progression and sea‐ice dynamics through their impacts on vertical stratification and freshwater input. Overall, our results highlight the importance of stratification and the duration of the open‐water period in shaping phytoplankton regimes—either oligotrophic or eutrophic—in marine waters of the Canadian Arctic.

Iron from melting glaciers fuels phytoplankton blooms in the Amundsen Sea (Southern Ocean): Phytoplankton characteristics and productivity

Phytoplankton species composition, biomass, and rates of primary production were determined at two sites within Kenepuru Sound, New Zealand, in spring, summer, and autumn of 1982–83. Microflagellates and ultraplankton (< 5–10 μm) were numerically very abundant on each occasion and small gymnodinoid nanno‐planktonic (< 10–15 μm) dinoflagellates were likewise always a common component of the populations. The dinoflagellate, Prorocentrum gracile , made a substantial contribution to the total biomass in summer. The diatom community changed from mainly small chain forming species (Chaetoceros spp., Leptocylindricus spp.) in spring to small solitary centric and pennate forms (Nitzchia longissima, Coscinodiscus spp.) in summer, to a diversity of larger taxa (Coscinodiscus concinnus, Eucampia zoodiacus) in autumn. The autotrophic ciliate Mesodinium rubrum was a particularly important member of the autumn photo‐autotrophic assemblage. Both phytoplankton biomass and productivity increased from spring to autumn. In situ rates of primary production ranged from 15 to 1420 mgC m ‐2 h ‐1 and chlorophyll a concentrations ranged from 6.9 to 258.5 mgChl a m ‐2 . A gross primary production rate, in summer, was estimated at 0.57 gC m ‐2 d ‐1 . Phytoplankton production and biomass appeared to be related to dissolved inorganic nutrient concentrations as a result of variations in the freshwater inflow. A tentative comparison between the rates of phytoplankton and cultivated mussel production is made.

Sea surface temperature control of taxon specific phytoplankton production along an oligotrophic gradient in the Mediterranean Sea

The existing oligotrophic conditions in the southwest tropical Indian Ocean (SWTIO) is believed to be one of the causes for low phytoplankton productivity (PP) observed in this area. Though many remote sensing based studies on PP have been carried out in SWTIO; studies on in situ estimation of PP and its cause(s) of variability are scarce. Thus, to understand the controlling environmental forcings on the variability in phytoplankton biomass (chlorophyll-a; Chl-a), community structure and productivity, time series (TS; @6h intervals for 10 days) plus point measurements (RT) were carried out in the SWTIO during southwest monsoon (June) of 2014. Strong thermohaline stratification resulted in shallow (35-40m) mixed layer (ML). Subsurface Chl-a maximum (SCM) was observed to oscillate within 40-60m with majority of peaks at ~50m, and existed just beneath the ML depth. Light availability at the time of sampling was highly conducive for algal growth; whereas nutrient ratios indicated N- and Si-limitation suggesting unfavourable conditions for diatoms and/or silicoflagellates growth within the ML. Furthermore, HPLC-based pigments analysis confirmed dominance of nano-sized plankton (53%) followed by pico-plankton (25%) and micro-plankton (22%). Column integrated production (IPP) varied from 176 - 268 (241+43 mgC m-2 d-1) and was relatively stable during the observation period, except a low value on 11-June, which was ascribed to the drastic dropdown in the daily incident PAR due to overcast sky. Vertical profiles of PP and Chl-a resembled each other and maximum PP usually corresponded with SCM depths. The Chl-a-specific PP (PB) was mostly higher within the ML and showed no surface photoinhibition, due to the dominance of smaller phytoplankton (less prone to pigment packaging effect) in the surface layer. Comparatively, higher PB within the ML is indicative of phytoplankton healthiness during the sampling time, whereas low PB below the SCM was due to light limitation. Highest integrated Chl-a (39 mg m-2) and IPP (328 mgC m-2 d-1) observed at RT-2 was clearly linked to low sea surface height anomaly (SSHA), cyclonic disturbance and associated positive Ekman pumping. Conversely, high SSHA and strong stratification conditions prevailed at TS, RT-4 and RT-6 stations leading to comparatively low IPP.

The northern Adriatic Sea has been historically subjected to phosphorus and nitrogen loading. Recent signs of increasing eutrophication include oxygen deficiency in the bottom waters and large-scale formation of gelatinous macroaggregates. The reason for the formation of these macroaggregates is unclear, but excess production of phytoplankton polysaccharides is suspected. In order to study the effect of different nutrient (nitrogen:phosphorus:silicon) ratios on phytoplankton production, biomass, polysaccharides, and species succession, 4 land-based enclosure experiments were performed with northern Adriatic seawater. During 2 of these experiments the importance of zooplankton grazing as a phytoplankton loss factor was also investigated Primary productivity in the northern Adriatic Sea is thought to be phosphorus limited, and our experiments confirmed that even low daily phosphorus additions increased phytoplankton biomass. However, this only occurred when nitrogen additions were high. Alternatively, when nitrogen was added in low concentrations, with simultaneous high phosphorus additions, phytoplankton biomass declined. Nitrogen deficiency induced the highest production of polysaccharides per unit of cell carbon, while nutrient-sufficient and phosphorus-deficient treatments caused a higher production of polysaccharides in total. In order to decrease the frequency of algal blooms and high polysaccharide production in the northern Adriatic, it appears necessary to reduce the amounts of incoming nutrients. Since phosphorus has a high turnover rate in low P:high N waters of the northern Adriatic, and since our experiments show that a shortage of nitrogen can produce reduced levels of phytoplankton biomass and total polysaccharides, a reduction of the nitrogen discharge would probably be the best countermeasure for eutrophication in the northern Adriatic Sea.

Influence of freshwater inflow variability on the Douro estuary primary productivity: A modelling study

Numerical Simulation of phytoplankton productivity in partially mixed estuaries