Primary Production in Relation to Temperature Structure, Biomass Concentration, and Light Conditions at an Inshore and Offshore Station in Lake Ontario

1974 ◽  
Vol 31 (7) ◽  
pp. 1215-1232 ◽  
Author(s):  
P. Stadelmann ◽  
J. E. Moore ◽  
E. Pickett
Keyword(s):  
Primary Production ◽  
Biomass Concentration ◽  
Lake Ontario ◽  
Early Summer ◽  
Temperature Structure ◽  
Turnover Rates ◽  
Available Energy ◽  
Offshore Station ◽  
Photosynthesis Efficiency ◽  
Different Depths

Annual primary production rates of 270 and 170 g C m−2 yr−1, respectively, were estimated for an inshore and offshore station in Lake Ontario using the in situ 14C technique. A lag in increase of both biomass and photosynthesis rate at the offshore station in early summer was attributed to deep vertical mixing.Production/biomass quotients were computed using different biomass parameters such as particulate organic carbon, nitrogen, and chlorophyll a. Carbon turnover rates of the seston on an areal basis (m2) were found to vary between 0.04–0.18 day−1 and 0.01–0.21 day−1 at the inshore and offshore station, respectively. Daily photosynthesis efficiency (energy fixed by photosynthesis/available energy) ranged from 0.1 to 1.8% at the two stations. Atypical photosynthesis–light intensity curves showed that algal populations behaved differently at different depths during the stratified period.

Primary Production in Lakes Ontario and Erie: A Comparative Study

1974 ◽  
Vol 31 (3) ◽  
pp. 253-263 ◽  
Author(s):  
Walter A. Glooschenko ◽  
James E. Moore ◽  
Mohiuddin Munawar ◽  
R. A. Vollenweider
Keyword(s):  
Primary Production ◽  
Chlorophyll A ◽  
Lake Erie ◽  
Lake Ontario ◽  
Early Summer ◽  
Central Basin ◽  
Western Basin ◽  
Eastern Basin ◽  
Production Values ◽  
Rate Of Increase

Primary production values in Lake Ontario were low in winter, reached a maximum in midspring, declined during summer, and slightly increased in fall. Rate of increase of production for inshore waters (< 20 m depth) was greater especially in spring and early summer with a greater maximum reached earlier than in offshore waters. Assimilation numbers, mgC fixed/mg chlorophyll a per hour, in Lake Ontario were fairly constant over the lake with a yearly range of 1.2–1.6. Primary production showed a linear relationship to chlorophyll a concentration, as also occurred in Lake Erie.Lake Erie primary production varied in its three basins. Seasonally, in the Eastern Basin, production was highest in spring with a midsummer decline, and small peaks in fall. The Western Basin had a maximum in midsummer whereas the Central Basin had peaks in late summer and early fall. Assimilation numbers were highest in the Western Basin (up to 3.5 mgC/mg chlorophyll a per hour) and lowest in the mid-Central Basin and Eastern Basin with values of approximately 1.4 mgC/mg chlorophyll a per hour. A definite westerly increase of assimilation number was observed.Up to early summer, the two lakes were fairly equal in surface production but integral photosynthesis, mgC/m2 per hour was higher in Lake Ontario than in Lake Erie. The same was valid in November and December. In summer, Lake Erie was higher in production on both a mgC/m3 per hour and mgC/m2 per hour basis. For the period, April–December, Lake Ontario's total estimated yield was 170 gC/m2, whereas for Lake Erie values of 160, 210, and 310 gC/m2 were found for the Eastern, Central, and Western basins, respectively.

scholarly journals Seasonal evolution of aerosol stratigraphy in Ürümqi glacier No. 1 percolation zone, eastern Tien Shan, China

2006 ◽  
Vol 43 ◽  
pp. 245-249 ◽  
Author(s):  
Feiteng Wang ◽  
Zhongqin Li ◽  
Xiaoni You ◽  
Chuanjin Li ◽  
Huilin Li ◽  
...  
Keyword(s):  
Wind Erosion ◽  
Sampling Site ◽  
Chemical Species ◽  
Early Summer ◽  
Tien Shan ◽  
Wet Season ◽  
Surface Layers ◽  
Different Depths ◽  
Physical And Chemical ◽  
Percolation Zone

AbstractThe processes involved in the evolution of vertical profiles of Mg2+, Ca2+ and microparticle concentrations, as well as their seasonal variation in surface snow, were studied by weekly sampling from September 2003 to September 2004 of a snow pit on Ürümqi glacier No. 1, eastern Tien Shan, China. The development of the microparticle and Mg2+ and Ca2+ stratigraphy in the snow pit is closely related to the physical development of the snow–firn pack. The sampling site is located at 4130 ma.s.l. in the percolation zone of the glacier, and in addition to the effects of sublimation and wind erosion, melting plays a crucial role in both the physical and chemical evolution processes. During the winter, soluble aerosol concentrations in the surface layers are altered slightly by sublimation and wind erosion, and the concentrations are further modified as the wet season begins in late April. In contrast, soluble aerosol stratigraphy in the deeper layers remains relatively unchanged through the winter. In early summer, as melting occurs in the upper part of the snow–firn pack, meltwater carries chemical species to different depths in the underlying snow–firn layers, such that at the end of the ablation season, all of the surface cations might be leached out from the upper layers. In addition, the possible source of calcium and magnesium is discussed in this paper.

Circulation and Temperature Structure in Large Marine Enclosures

1977 ◽  
Vol 34 (8) ◽  
pp. 1095-1104 ◽  
Author(s):  
J. H. Steele ◽  
D. M. Farmer ◽  
E. W. Henderson
Keyword(s):  
Vertical Mixing ◽  
Temperature Structure ◽  
Temperature Profiles ◽  
Turbulent Diffusivity ◽  
Mixing Energy ◽  
Physical Measurements ◽  
Average Coefficient ◽  
Different Depths ◽  
External Fluctuations ◽  
Shed Light

Certain physical measurements intended to shed light on the circulation in large plastic enclosures (60–2000 m3) induced by the changing environment in which they are moored are described. Layers of dye were generally seen to diffuse vertically although some important advection effects were also observed. Estimates of an average coefficient of turbulent diffusivity yielded values in the range.05–.26 cm2∙s−1.Measurements taken with recording thermistor chains both inside and outside the enclosures show strong damping of external fluctuations with periods significantly less than 1 day. Various possible sources of mixing energy are considered and it is concluded that thermal forcing through the wall may be significant and could account for the observed range of coefficients.The significance of the observed mixing and circulation to the ecology of the enclosures is discussed. Of particular importance is the vertical mixing of nutrients that influences phytoplankton sinking rates and thus plays a crucial role in determining variations in algal concentration at different depths. Key words: mixing, enclosures, controlled ecosystem pollution experiment, circulation, temperature profiles

Diel and Annual Cycles of Net Plankton Photosynthesis in Lake Ontario

1973 ◽  
Vol 30 (12) ◽  
pp. 1779-1787 ◽  
Author(s):  
G. P. Harris
Keyword(s):  
Inverse Correlation ◽  
Lake Ontario ◽  
Rate Of Change ◽  
Annual Cycles ◽  
Light Regimes ◽  
Static Water ◽  
Different Depths ◽  
Diel Fluctuations ◽  
Photosynthesis And Respiration ◽  
Net Phytoplankton

Photosynthesis measurements on net plankton have been carried out for the period April, 1972 to January, 1973 in Lake Ontario. The rising and falling light regimes used on the net phytoplankton (> 64 μ) give marked photosynthetic hysteresis effects in winter and in spring for diatom-dominated populations. Diel fluctuations in photosynthesis and "sun" or "shade" adaptations showed a close interaction between the phytoplankton and the surface light intensity. Systematic seasonal changes have been recorded in the magnitude of the photosynthetic hysteresis effect, saturation light intensities, compensation points, maximum photosynthesis, and respiration rates. An inverse correlation has been found between net plankton mean maximum photosynthesis rates and the rate of change of water temperature. Also phytoplankton respiration rate is largely a function of temperature.The data have been unified to give a picture of daily photosynthesis patterns at different depths in a static water column. The data compare well with 14C moored bottle experiments. Predictive equations have been calculated for maximum photosynthesis rates at different times of the year.

scholarly journals Simulating the effects of phosphorus limitation in the Mississippi and Atchafalaya River plumes

2012 ◽  
Vol 9 (11) ◽  
pp. 4707-4723 ◽  
Author(s):  
A. Laurent ◽  
K. Fennel ◽  
J. Hu ◽  
R. Hetland
Keyword(s):  
Gulf Of Mexico ◽  
Primary Production ◽  
Inorganic Nitrogen ◽  
Circulation Model ◽  
Phosphorus Limitation ◽  
Early Summer ◽  
Nitrogen And Phosphorus ◽  
River Plumes ◽  
Northern Gulf Of Mexico ◽  
Plume Region

Abstract. The continental shelf of the northern Gulf of Mexico receives high dissolved inorganic nitrogen and phosphorus loads from the Mississippi and Atchafalaya rivers. The nutrient load results in high primary production in the river plumes and contributes to the development of hypoxia on the Louisiana shelf in summer. While phytoplankton growth is considered to be typically nitrogen-limited in marine waters, phosphorus limitation has been observed in this region during periods of peak river discharge in spring and early summer. Here we investigate the presence, spatio-temporal distribution and implications of phosphorus limitation in the plume region using a circulation model of the northern Gulf of Mexico coupled to a multi-nutrient ecosystem model. Results from a 7-yr simulation (2001–2007) compare well with several sources of observations and suggest that phosphorus limitation develops every year between the Mississippi and Atchafalaya deltas. Model simulations show that phosphorus limitation results in a delay and westward shift of a fraction of river-stimulated primary production. The consequence is a reduced flux of particulate organic matter to the sediment near the Mississippi delta, but slightly enhanced fluxes west of Atchafalaya Bay. Simulations with altered river phosphate concentrations (±50%) show that significant variation in the spatial extent of phosphorus limitation (±40% in July) results from changes in phosphate load.

scholarly journals Extreme events in gross primary production: a characterization across continents

2014 ◽  
Vol 11 (1) ◽  
pp. 1869-1907 ◽  
Author(s):  
J. Zscheischler ◽  
M. D. Mahecha ◽  
S. Harmeling ◽  
A. Rammig ◽  
E. Tomelleri ◽  
...  
Keyword(s):  
South America ◽  
Primary Production ◽  
Extreme Events ◽  
Gross Primary Production ◽  
Climate Extremes ◽  
Terrestrial Ecosystems ◽  
Global Scale ◽  
Early Summer ◽  
Seasonal Effects ◽  
Data Sets

Abstract. Climate extremes can affect the functioning of terrestrial ecosystems, for instance via a reduction of the photosynthetic capacity or alterations of respiratory processes. Yet the dominant regional and seasonal effects of hydrometeorological extremes are still not well documented. Here we quantify and characterize the role of large spatiotemporal extreme events in gross primary production (GPP) as triggers of continental anomalies. We also investigate seasonal dynamics of extreme impacts on continental GPP anomalies. We find that the 50 largest positive (increase in uptake) and negative extremes (decrease in uptake) on each continent can explain most of the continental variation in GPP, which is in line with previous results obtained at the global scale. We show that negative extremes are larger than positive ones and demonstrate that this asymmetry is particularly strong in South America and Europe. Most extremes in GPP start in early summer. Our analysis indicates that the overall impacts and the spatial extents of GPP extremes are power law distributed with exponents that vary little across continents. Moreover, we show that on all continents and for all data sets the spatial extents play a more important role than durations or maximal GPP anomaly when it comes to the overall impact of GPP extremes. An analysis of possible causes implies that across continents most extremes in GPP can best be explained by water scarcity rather than by extreme temperatures. However, for Europe, South America and Oceania we identify also fire as an important driver. Our findings are consistent with remote sensing products. An independent validation against a literature survey on specific extreme events supports our results to a large extent.

scholarly journals Simulating the effects of phosphorus limitation in the Mississippi and Atchafalaya River plumes

2012 ◽  
Vol 9 (5) ◽  
pp. 5625-5657 ◽  
Author(s):  
A. Laurent ◽  
K. Fennel ◽  
J. Hu ◽  
R. Hetland
Keyword(s):  
Gulf Of Mexico ◽  
Primary Production ◽  
Inorganic Nitrogen ◽  
Circulation Model ◽  
Phosphorus Limitation ◽  
Early Summer ◽  
Nitrogen And Phosphorus ◽  
River Plumes ◽  
Northern Gulf Of Mexico ◽  
Plume Region

Abstract. The continental shelf of the northern Gulf of Mexico receives high dissolved inorganic nitrogen and phosphorus loads from the Mississippi and Atchafalaya rivers. The nutrient load results in high primary production in the river plumes and contributes to the development of hypoxia on the Texas-Louisiana shelf in summer. While phytoplankton growth is considered to be typically nitrogen-limited, phosphorus limitation has been observed in this region during periods of peak river discharge in spring and early summer. Here we investigate the presence, spatio-temporal distribution and implications of phosphorus limitation in the plume region using a circulation model of the northern Gulf of Mexico coupled to a multi-nutrient ecosystem model. Results from a 7 yr simulation (2001–2007) compare well with available observations and suggest that phosphorus limitation develops every year between the Mississippi and Atchafalaya deltas. Model simulations show that phosphorus limitation results in a delay and westward shift of a fraction of river-stimulated primary production. The consequence is a reduced flux of particulate organic matter to the sediment near the Mississippi delta, but enhanced fluxes westward in the Atchafalaya and far-field regions. Two discharge scenarios with altered river phosphate concentrations (&amp;pm;50 %) reveal a significant variation (&amp;pm;40 % in July) in the spatial extent of phosphorus limitation with changes in phosphate load.

The primary production of aldabra atoll, with reference to habitats used by Giant Tortoises

1983 ◽  
Vol 302 (1109) ◽  
pp. 167-199 ◽  
Keyword(s):  
Primary Production ◽  
Standing Crop ◽  
Single Species ◽  
Structural Heterogeneity ◽  
Turnover Rates ◽  
Net Production ◽  
Wooded Area ◽  
Leaf Turnover ◽  
Scrub Forest

This paper reports on the seasonal changes of standing crop and production in habitats used by a high-density population of giant tortoises on Aldabra atoll. The study had two main aims: first to investigate the primary production of a raised coral atoll (to our knowledge the first such study) and secondly to provide base data for a study of the interactions of a large reptilian herbivore (the giant tortoise) with its food supply and environment. Environmental heterogeneity made it necessary to measure separately the standing crop and the above-ground net production of different components of the vegetation; these components were usually single species or small groups of species of plants. Measurements of these components were then combined with cover data for the same components in selected places to illustrate the seasonal and spatial variability of primary production on Aldabra. Standing crop biomasses were estimated from harvest samples. Methods for production estimates varied with the component studied, but included harvest difference methods, repeated clipping of the same plots and direct measurement of leaf turnover rates on marked shoots. These methods are compared where appropriate. Net annual above-ground production varied between plant types from 3165 kJ per square metre of plant for ‘tortoise turf’ to 47700 kJ m -2 for Cyperus ligularis , a robust perennial sedge. Total above-ground annual net production of different habitat types (bare ground and rocks between plants being taken into account) varied from 9100 kJ m -2 in a thinly wooded area with high tortoise turf cover (‘open mixed scrub’) to 28200 kJ m -2 in an area of thick scrub forest (‘groves’). The seasonality of production and standing crop also varied considerably between habitats, owing to the role of different components of the ground layer and shrub cover. These results are discussed in terms of the roles of environmental and structural heterogeneity in setting primary production and of the tortoises themselves in their interactions with the vegetation via trampling and grazing. The effect of this heterogeneity on sampling strategies and results is also assessed.

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