Phytoplankton photosynthesis at two index stations in Lake Ontario 1987-1992: assessment of the long-term response to phosphorus control

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

doi:10.1139/f96-029

Cited by 16 publications

(27 citation statements)

References 31 publications

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“…P was, however, about 50% higher than the 8-yr average B m value observed in the ELA lakes ) but close to phaeopigment-corrected values reported for Lake Ontario (Millard et al 1992). The median ␣ B (9.2 mgC mgChl a Ϫ1 E Ϫ1 m 2 ) was nearly twice as high as median values reported for ELA and other Shield lakes (Fee et al , 1992.…”

Section: Resultssupporting

confidence: 78%

Planktonic production and respiration in oligotrophic Shield lakes

Carignan

Planas

Vis

2000

Limnology & Oceanography

179

129

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A precise oxygen method was used to measure primary production, community respiration and to determine the importance of exogenous organic carbon as an energy source to planktonic communities in the epilimnion of 12 oligotrophic to mesotrophic Shield lakes. Median photosynthetic parameters observed with the oxygen method were up to twice as high as those measured with 14 C in other oligotrophic Shield lakes. Gross photosynthesis was almost always larger than community respiration, with a median P : R ratio of 1.7. We observed strong relationships between respiration and gross photosynthesis, but could not detect any significant trend between respiration or the P : R ratio and the concentration of dissolved organic carbon (DOC). DOC appeared to depress both photosynthesis and respiration. These results argue against the importance of exogenous organic carbon supply as a significant energy source to freshwater planktonic communities. Previously low P : R ratios reported for oligotrophic fresh waters may be due to the uncertain meaning of 14 C production data.The balance between production and respiration lies at the basis of our understanding of carbon flow and food web structure in marine and freshwater ecosystems. Ecosystems where photosynthesis exceeds total planktonic respiration (P Ͼ R) are net autotrophic; they are net sinks for CO 2 and net producers of O 2 and organic matter. Conversely, ecosystems where respiration exceeds photosynthesis (P Ͻ R) are net heterotrophic; they are net sources of CO 2 and net consumers of organic carbon.The relative importance of primary production and community respiration in oligotrophic waters and the role of exogenous organic carbon as an energy source to planktonic communities are the subject of an ongoing debate in oceanography and limnology. Most ecologists have considered lakes and oceans as net autotrophic systems fueled primarily by planktonic photosynthesis. Our understanding of carbon flow and of the production-respiration balance in oligotrophic aquatic ecosystems is still limited, however. Several studies have suggested that respiration systematically exceeds photosynthesis in the epilimnion of oligotrophic lakes, estuaries, and oceans (Sorokin 1971;Findlay et al.

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Section: Resultssupporting

confidence: 78%

Planktonic production and respiration in oligotrophic Shield lakes

Carignan

Planas

Vis

2000

Limnology & Oceanography

179

129

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“…70% was chosen to eliminate meteorological variability and to provide a reasonable estimate of actual production rates. Millard et al (1996) found that empirical solar irradiance approximated 70% of theoretical cloud-free irradiance for Lake Ontario. Using the empirical solar data collected in 2002 (see Radiation measurements section below), we calculated that empirical solar data averaged 64.4% ± 23.1% of theoretical (100%) cloud-free values generated by YPHOTO and YTOTAL (Fee 1990), so our choice of 70% should not greatly overestimate primary production rates.…”

Section: Primary Production Calculationsmentioning

confidence: 93%

“…The seasonal distribution of chl a and P int in the east basin during 2001-2002, as in 1970(Glooschenko et al 1974, could be considered bimodal and consistent with the classical pattern. Primary production and chl a measurements in the 1980s and 1990s from Lakes Ontario (e.g., Millard et al 1996), Michigan (e.g., Fahnenstiel and Scavia 1987a, fall months excluded), and eastern Lake Erie (e.g., MacDougall et al 2001) also tended towards the classical bimodal pattern. The patterns observed can be quite variable between years, however, and some east basin stations have shown only a single summer-fall peak in some years (e.g., MacDougall et al 2001).…”

Section: Seasonal Patterns Of Chl a And Primary Productionmentioning

confidence: 94%

Nearshoreoffshore comparison of chlorophyll a and phytoplankton production in the dreissenid-colonized eastern basin of Lake Erie

Depew¹,

Guildford²,

Smith³

2006

Can. J. Fish. Aquat. Sci.

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Planktonic primary production, chlorophyll a (chl a), underwater light climate, and total phosphorus were measured at 18 stations during 2001 and 2002 in eastern Lake Erie to characterize spatial and seasonal patterns in this system colonized by dreissenid mussels (Dreissena spp.). Areal production rates and chl a displayed a seasonal pattern typical of the Laurentian Great Lakes, with highest production in the early and late summer. Daily and seasonal (MayOctober) primary production was significantly lower nearshore than offshore. Although light attenuation was similar between nearshore and offshore, the nearshore light climate was generally more favorable for phytoplankton because of shallower mixing depths. However, chl a was significantly lower nearshore, which accounted for most of the depression in production rates. Nearshore chl a was lower than predicted from relationships with total phosphorus in comparable dreissenid-free systems. Offshore, subepilimnetic communities contributed up to 67% of daily production but only up to 19% of seasonal production. The depression of chl a and primary production in the nearshore was a reversal from historic patterns in eastern Lake Erie and from the pattern traditionally expected in large lakes. Decreased external nutrient loading and dreissenid colonization may both have contributed to this new spatial pattern, but dreissenids appear to be key agents.Résumé : Nous avons mesuré en 2001 et 2002 la production primaire planctonique, la chlorophylle a (chl a), les conditions lumineuses aquatiques et le phosphore total dans 18 stations de l'est du lac Érié afin de caractériser les structures spatiale et saisonnière de ce système colonisé par les bivalves dreissénidés (Dreissena spp.). Les taux de production et la chl a en fonction de la surface suivent un patron typique des Grands Lacs laurentiens, avec des maximum de production au début et à la fin de l'été. La production primaire journalière (mai-octobre) est significativement plus basse près des rives qu'au large. Bien que l'atténuation de la lumière soit semblable près du bord et au large, les conditions lumineuses près des rives sont généralement plus favorables au phytoplancton à cause de l'épaisseur moindre de la couche de brassage. Cependant, la chl a est significativement moins abondante près des rives, ce qui explique presque toute la diminution des taux de production. La chl a près des rives est moins abondante que prédit d'après les relations avec le phosphore total établies dans des systèmes comparables sans la présence des dreissénidés. Les communautés du large situées sous l'épilimnion fournissent jusqu'à 67 % de la production journalière, mais seulement un maximum de 19 % de la production saisonnière. La diminution de la chl a et de la production primaire près des rives représente un renversement des patrons historiques dans l'est du lac Érié et des patrons attendus dans les lacs de grande taille. Une réduction des apports provenant de l'extérieur et la colonisation par les dreissénidés peuvent toutes deux a...

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“…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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Phytoplankton photosynthesis at two index stations in Lake Ontario 1987-1992: assessment of the long-term response to phosphorus control

Cited by 16 publications

References 31 publications

Planktonic production and respiration in oligotrophic Shield lakes

Planktonic production and respiration in oligotrophic Shield lakes

Nearshoreoffshore comparison of chlorophyll a and phytoplankton production in the dreissenid-colonized eastern basin of Lake Erie

The ecological history of Lake Ontario according to phytoplankton

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Phytoplankton photosynthesis at two index stations in Lake Ontario 1987-1992: assessment of the long-term response to phosphorus control

Cited by 16 publications

References 31 publications

Planktonic production and respiration in oligotrophic Shield lakes

Planktonic production and respiration in oligotrophic Shield lakes

Nearshoreoffshore comparison of chlorophyll a and phytoplankton production in the dreissenid-colonized eastern basin of Lake Erie

The ecological history of Lake Ontario according to phytoplankton

Contact Info

Product

Resources

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Nearshoreoffshore comparison of chlorophyll a and phytoplankton production in the dreissenid-colonized eastern basin of Lake Erie