Seasonal phosphorus deficiency of Lake Ontario phytoplankton at two index stations: light versus. phosphorus limitation of growth

Millard, Éric; Myles, D D; Johannsson, Ora E.; Ralph, K. M.

doi:10.1139/f96-030

Cited by 15 publications

(24 citation statements)

References 23 publications

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“…Alternatively, one or more environmental factors may constrain the ability of phytoplankton to use nitrate in the lake. Owing to the complex seasonal and synergistic relationships between light and nutri- ent availability in the Great Lakes (Nalewajko et al 1981;Nalewajko and Voltolina 1986;Millard et al 1996;Fahnenstiel et al 2000), the AND100 bioreporter exhibits performance characteristics under varying light regimes and nutrient status that are suitable to assess the influence of these factors on nitrate consumption. The reporter strain thus provides a proxy for the physiological responses of the endogenous cyanobacteria, whose nitrogen assimilatory functions are likely similarly regulated by light levels, nitrogen speciation, and bioavailability of both phosphate and iron.…”

Section: Discussionmentioning

confidence: 99%

Construction and characterization of a cyanobacterial bioreporter capable of assessing nitrate assimilatory capacity in freshwaters

Ivanikova

McKay

Bullerjahn

2005

Limnol. Oceanogr. Methods

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The use of cyanobacterial whole-cell luminescent bioreporters has enhanced our ability to monitor nutrient availability in aquatic ecosystems. We have constructed a Synechocystis sp. strain PCC6803 bioluminescent reporter for the assessment of nitrate bioavailability. Specifically, a 380-base pair DNA fragment containing the NtcA/B-dependent nitrate/nitrite-activated nirA promoter (regulating expression of genes encoding nitrite reductase) was fused to the bacterial luciferase genes, luxAB, and introduced into Synechocystis by genetic transformation. Characterization of this strain, designated AND100, yielded dose-dependent increased bioluminescence coincident with increased nitrate added to the growth medium from 1 to 100 µM. Bioluminescence in response to nitrate addition was light dependent up to 50 µmol quanta m -2 s -1

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Section: Discussionmentioning

confidence: 99%

Construction and characterization of a cyanobacterial bioreporter capable of assessing nitrate assimilatory capacity in freshwaters

Ivanikova

McKay

Bullerjahn

2005

Limnol. Oceanogr. Methods

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“…Johannsson et al (1998) associated P input reductions with declines in water column TP, algal standing crop, and zooplankton productivity between 1981 and 1987 in the Mississauga and the eastern Kingston basins. In contrast, Mills et al (2003a) reported significant NO 3 concentration increases from 1968 to l987, paralleling N fertilizer application and probably resulting in summer P limitation in deep pelagic waters (Lean et al, 1987a(Lean et al, , 1987bMillard et al, 1996a). Millard et al (1996b) also measured seasonal phytoplankton photosynthesis from 1987 to 1992 and compared results to locations from the 1972 Lake Ontario IFYGL.…”

Section: Main Lake Regionmentioning

confidence: 99%

The ecological history of Lake Ontario according to phytoplankton

Estepp

Reavie

2015

Journal of Great Lakes Research

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Lake Ontario's condition has fluctuated since European settlement, and our understanding of the linkages between observed ecosystem shifts and stressors is improving. Changes in the physical and chemical environment of the lake due to non-indigenous species, pollution, sedimentation, turbidity, and climate change altered the pelagic primary producers, so algal assessments have been valuable for tracking long-term conditions. We present a chronological account of algal assessments to summarize past and present environmental conditions in Lake Ontario. This review particularly focuses on pelagic, diatom-based assessments as their fossils in sediments have revealed the combined effects of environmental insults and recovery. This review recaps the long-term trends according to three unique regions: Hamilton Harbour, the main lake basin, and the Bay of Quinte. We summarize pre-European impact settlement; eutrophication throughout most of the 20th century; subsequent water quality changes due to nutrient reductions; and filter-feeding dreissenid colonization and contemporary pelagic, shoreline, and embayment impairments. Recent data suggest that although phytoplankton biovolume is stable, species composition has shifted to an increase in densities of spring eutrophic diatoms and summer cyanobacteria. Continued monitoring and evaluation of historical data will assist in understanding and responding to the natural and anthropogenic drivers of Lake Ontario's environmental conditions.

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“…Regarding nutrient limitation, the main channel of the International Section of the St. Lawrence River is expected to be primarily phosphorus limited in late spring and summer, as are its immediate headwaters in Lake Ontario (Millard et al, 1996). Phosphorus limitation decreases photosynthetic efficiency in phytoplankton (Litchman et al, 2003); hence, any decreases in P could reduce phytoplankton fitness and be reflected in both reduced photosynthetic efficiency and biomass.…”

Section: Introductionmentioning

confidence: 99%

Plankton dynamics along a 180 km reach of the Saint Lawrence River from its headwaters in Lake Ontario

et al. 2010

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We test the hypothesis that phytoplankton biomass decrease upon entry into the St. Lawrence River from headwaters in Lake Ontario is attributable to a range of causal factors including, decreased photosynthetic fitness due to turbulence, cell loss due to increased flocculation and subsequent sedimentation, decreases in nutrients, and loss due to grazing. In order to test this, changes in phytoplankton and crustacean zooplankton concentrations were examined during four transects along the river, from 8 km offshore in Lake Ontario to the hydroelectric power dam 180 km downstream. Both phytoplankton biomass, measured as chlorophyll-a, and zooplankton decreased markedly upon entry of lake water into the river. Phytoplankton community composition and size changed little over the river reach and tended to reflect that in Lake Ontario. Total phosphorus increased with transit of river water downstream despite low tributary inputs of water into this reach of river. Light availability was high, photosynthetic efficiency suggested that phytoplankton were not physiologically stressed during transit in turbulent waters, and there was no direct evidence of flocculation causing sedimentation of phytoplankton. Grazing by the benthic community (filtering insect larvae and dreissenid mussels) is inferred to be a dominant biological factor as is the geomorphology in this reach of the river, which includes large littoral areas, shoals, and reaches of high water velocity that can increase particle contact in the water column with benthic grazers. The findings of this study have a bearing on understanding how changing water levels in a regulated river might alter areas of benthic grazing.

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Seasonal phosphorus deficiency of Lake Ontario phytoplankton at two index stations: light versus. phosphorus limitation of growth

Cited by 15 publications

References 23 publications

Construction and characterization of a cyanobacterial bioreporter capable of assessing nitrate assimilatory capacity in freshwaters

Construction and characterization of a cyanobacterial bioreporter capable of assessing nitrate assimilatory capacity in freshwaters

The ecological history of Lake Ontario according to phytoplankton

Plankton dynamics along a 180 km reach of the Saint Lawrence River from its headwaters in Lake Ontario

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