Modelling phytoplankton production at shelf-sea fronts

1981 ◽  
Vol 302 (1472) ◽  
pp. 605-615 ◽  
Keyword(s):  
General Theory ◽  
Primary Production ◽  
Turbulent Mixing ◽  
Dominant Factor ◽  
Phytoplankton Production ◽  
Controlled Growth ◽  
Water Motion ◽  
Horizontal Gradients ◽  
Shelf Sea ◽  
Vertical Turbulent Mixing

Large standing crops of phytoplankton are often found in the neighbourhood of shelf-sea fronts. How do these large biomasses come about? Special hypotheses have been proposed, but it seems preferable to treat frontal production in terms of a general theory. By assuming that phytoplankton behave as 'passive contaminants of water motion' and that vertical turbulent mixing is the dominant factor, it is possible to model the distribution of phytoplankton at fronts by means of simple expressions for photosynthesis, nutrient-controlled growth, and grazing. Because of their strong vertical and horizontal gradients, fronts are good places to test such simple models, which might also be applied to primary production in other regions of the ocean.

The Coupling of Heterotrophic Bacterial and Phytoplankton Production in a Hypertrophic, Shallow Prairie Lake

1994 ◽  
Vol 51 (10) ◽  
pp. 2219-2226 ◽  
Author(s):  
Richard D. Robarts ◽  
Michael T. Arts ◽  
Marlene S. Evans ◽  
Marley J. Waiser
Keyword(s):  
Primary Production ◽  
Bacterial Production ◽  
Thymidine Incorporation ◽  
Chlorophyll Concentration ◽  
Bacterial Biomass ◽  
Cyanobacterial Blooms ◽  
Dominant Factor ◽  
Phytoplankton Production ◽  
Carbon Production ◽  
Prairie Lakes

Data from hypertrophic Humboldt Lake (Zmax = 6 m), Saskatchewan, support published studies indicating that bacterial numbers and production do not increase proportionally with chlorophyll concentration and primary production. There was no compensation for these relationships with increased bacterial production per cell, but our data showed an increase in production per unit bacterial biomass (273 fmol TdR∙μg C−1∙h−1). Bacterial production (19.8–422 mg C∙m−2∙d−1) was correlated with primary production (r = 0.76), and maximum bacterial production coincided with summer cyanobacterial blooms. Water temperature was a dominant factor correlated with bacterial production (r = 0.85) and growth (r = 0.92). Depending upon the factors used to convert the rate of thymidine incorporation to gross carbon production, heterotrophic bacterial production was able to consume an average of 42% (408 mg C∙m−2∙d−1) to 67% (653 mg C∙m−2∙d−1) of plankton primary productivity. Based on these calculations, hypertrophic prairie lakes might accumulate autochthonously produced organic carbon, but this conclusion takes no account of benthic bacterial production which could be high in shallow lakes.

Light, Nutrients, and Water Temperature as Determinants of Phytoplankton Production in Two Saline, Prairie Lakes with High Sulphate Concentrations

1992 ◽  
Vol 49 (11) ◽  
pp. 2281-2290 ◽  
Author(s):  
Richard D. Robarts ◽  
Marlene S. Evans ◽  
Michael T. Arts
Keyword(s):  
Water Temperature ◽  
Photosynthetic Capacity ◽  
Chlorophyll Concentration ◽  
Euphotic Zone ◽  
Dominant Factor ◽  
Phytoplankton Production ◽  
Dissolved Phosphorus ◽  
Prairie Lakes ◽  
The Mean ◽  
Algal Productivity

Our data support empirical models indicating that algal productivity is low relative to total phosphorus (TP) levels in prairie lakes with high sulphate concentrations. Mean chlorophyll accounted for 91.1% of the variance in euphotic zone primary production (ΣA) in Humboldt Lake (total dissolved solids (TDS) = 3.3 g∙L−1; Zmax = 6 m), while TP, total dissolved phosphorus, and water temperature accounted for 82.7% of ΣA variance in Redberry Lake (TDS = 20.9 g∙L−1; Zmax = 17 m). The relative importance of these variables to ΣA resulted from biological, chemical, and physical differences of these lakes. Light usually penetrated to the bottom of Redberry Lake due to a mean euphotic zone (Zeu) chlorophyll of 1.7 mg∙m−3, while Humboldt Lake's mean Zeu was 3.4 m with a mean chlorophyll concentration of 62.6 mg∙m−3. Chlorophyll was the dominant factor correlated with light penetration in Humboldt Lake (r2 = 0.65) but not in Redberry Lake. Photosynthetic capacity was correlated (r2 = 0.72) with water temperature only in Redberry Lake. The mean ΣA was 57.1 and 230.2 mg C∙m−2∙h−1 for Redberry and Humboldt lakes, respectively.

Primary Production and Phytoplankton in the Experimental Lakes Area, Northwestern Ontario, and other Low-Carbonate Waters, and a Liquid Scintillation Method for Determining 14C Activity in Photosynthesis

1971 ◽  
Vol 28 (2) ◽  
pp. 189-201 ◽  
Author(s):  
D. W. Schindler ◽  
S. K. Holmgren
Keyword(s):  
Primary Production ◽  
Liquid Scintillation ◽  
Species Abundance ◽  
Euphotic Zone ◽  
Phytoplankton Production ◽  
Phytoplankton Species ◽  
Experimental Lakes Area ◽  
Phytoplankton Species Composition ◽  
Northwestern Ontario ◽  
Filtration Error

A modified 14C method is described for measuring phytoplankton production in low-carbonate waters. The procedure includes the use of the Arthur and Rigler (Limnol. Oceanogr. 12: 121–124, 1967) technique for determining filtration error, liquid scintillation counting for determining the radioactivity of membrane filters and stock 14C solutions, and gas chromatography for measuring total CO2.Primary production, chlorophyll a, and total CO2 were measured for two dates in midsummer from each of several lakes in the Experimental Lakes Area (ELA), ranging from 1 to 1000 ha in area and from 2 to 117 m in maximum depth. Phytoplankton species abundance and biomass were determined for the same dates. Production ranged from 0.02 to 2.12 gC/m3∙day and from 0.179 to 1.103 g C/m2∙day. Chlorophyll ranged from 0.4 to 44 mg/m3 and from 5 to 98 mg/m2 in the euphotic zone. The corresponding ranges for live phytoplankton biomass were 120–5400 mg/m3 and 2100–13,400 mg/m2. Chrysophyceae dominated the phytoplankton of most of the lakes.A system for classifying the lakes in terms of phytoplankton species composition and production–depth curves is developed.

scholarly journals Role of eyewall and rainband eddy forcing in tropical cyclone intensification

2019 ◽  
Vol 19 (22) ◽  
pp. 14289-14310 ◽  
Author(s):  
Ping Zhu ◽  
Bryce Tyner ◽  
Jun A. Zhang ◽  
Eric Aligo ◽  
Sundararaman Gopalakrishnan ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Turbulent Mixing ◽  
Inner Core ◽  
Weather Research And Forecasting ◽  
Rapid Changes ◽  
Flow Feature ◽  
Secondary Circulations ◽  
Vertical Turbulent Mixing ◽  
Operational Models

Abstract. While turbulence is commonly regarded as a flow feature pertaining to the planetary boundary layer (PBL), intense turbulent mixing generated by cloud processes also exists above the PBL in the eyewall and rainbands of a tropical cyclone (TC). The in-cloud turbulence above the PBL is intimately involved in the development of convective elements in the eyewall and rainbands and consists of a part of asymmetric eddy forcing for the evolution of the primary and secondary circulations of a TC. In this study, we show that the Hurricane Weather Research and Forecasting (HWRF) model, one of the operational models used for TC prediction, is unable to generate appropriate sub-grid-scale (SGS) eddy forcing above the PBL due to a lack of consideration of intense turbulent mixing generated by the eyewall and rainband clouds. Incorporating an in-cloud turbulent-mixing parameterization in the vertical turbulent-mixing scheme notably improves the HWRF model's skills in predicting rapid changes in intensity for several past major hurricanes. While the analyses show that the SGS eddy forcing above the PBL is only about one-fifth of the model-resolved eddy forcing, the simulated TC vortex inner-core structure, secondary overturning circulation, and the model-resolved eddy forcing exhibit a substantial dependence on the parameterized SGS eddy processes. The results highlight the importance of eyewall and rainband SGS eddy forcing to numerical prediction of TC intensification, including rapid intensification at the current resolution of operational models.

scholarly journals Attributing differences in the fate of lateral boundary ozone in AQMEII3 models to physical process representations

2018 ◽  
Vol 18 (23) ◽  
pp. 17157-17175
Author(s):  
Peng Liu ◽  
Christian Hogrefe ◽  
Ulas Im ◽  
Jesper H. Christensen ◽  
Johannes Bieser ◽  
...  
Keyword(s):  
Turbulent Mixing ◽  
Dry Deposition ◽  
Gulf Coast ◽  
Vertical Mixing ◽  
Primary Role ◽  
Southeastern Us ◽  
The Us ◽  
Vertical Grid ◽  
Vertical Turbulent Mixing ◽  
The Impact

Abstract. Increasing emphasis has been placed on characterizing the contributions and the uncertainties of ozone imported from outside the US. In chemical transport models (CTMs), the ozone transported through lateral boundaries (referred to as LB ozone hereafter) undergoes a series of physical and chemical processes in CTMs, which are important sources of the uncertainty in estimating the impact of LB ozone on ozone levels at the surface. By implementing inert tracers for LB ozone, the study seeks to better understand how differing representations of physical processes in regional CTMs may lead to differences in the simulated LB ozone that eventually reaches the surface across the US. For all the simulations in this study (including WRF∕CMAQ, WRF∕CAMx, COSMO-CLM∕CMAQ, and WRF∕DEHM), three chemically inert tracers that generally represent the altitude ranges of the planetary boundary layer (BC1), free troposphere (BC2), and upper troposphere–lower stratosphere (BC3) are tracked to assess the simulated impact of LB specification. Comparing WRF∕CAMx with WRF∕CMAQ, their differences in vertical grid structure explain 10 %–60 % of their seasonally averaged differences in inert tracers at the surface. Vertical turbulent mixing is the primary contributor to the remaining differences in inert tracers across the US in all seasons. Stronger vertical mixing in WRF∕CAMx brings more BC2 downward, leading to higher BCT (BCT=BC1+BC2+BC3) and BC2∕BCT at the surface in WRF∕CAMx. Meanwhile, the differences in inert tracers due to vertical mixing are partially counteracted by their difference in sub-grid cloud mixing over the southeastern US and the Gulf Coast region during summer. The process of dry deposition adds extra gradients to the spatial distribution of the differences in DM8A BCT by 5–10 ppb during winter and summer. COSMO-CLM∕CMAQ and WRF∕CMAQ show similar performance in inert tracers both at the surface and aloft through most seasons, which suggests similarity between the two models at process level. The largest difference is found in summer. Sub-grid cloud mixing plays a primary role in their differences in inert tracers over the southeastern US and the oceans in summer. Our analysis of the vertical profiles of inert tracers also suggests that the model differences in dry deposition over certain regions are offset by the model differences in vertical turbulent mixing, leading to small differences in inert tracers at the surface in these regions.

The contribution of the deep chlorophyll maximum to primary production in a seasonally stratified shelf sea, the North Sea

2013 ◽  
Vol 113 (1-3) ◽  
pp. 153-166 ◽  
Author(s):  
Liam Fernand ◽  
Keith Weston ◽  
Tom Morris ◽  
Naomi Greenwood ◽  
Juan Brown ◽  
...  
Keyword(s):  
Primary Production ◽  
North Sea ◽  
Deep Chlorophyll Maximum ◽  
Chlorophyll Maximum ◽  
The North ◽  
Shelf Sea ◽  
The North Sea

Primary Productivity of Southern Indian Lake before, during, and after Impoundment and Churchill River Diversion

1984 ◽  
Vol 41 (4) ◽  
pp. 591-604 ◽  
Author(s):  
R. E. Hecky ◽  
S. J. Guildford
Keyword(s):  
Light Intensity ◽  
Primary Production ◽  
Water Column ◽  
Primary Productivity ◽  
Phosphorus Deficiency ◽  
Light Environment ◽  
Phytoplankton Production ◽  
Light Penetration ◽  
The Mean ◽  
Chlorophyll Concentrations

The primary productivity of seven regions of Southern Indian Lake and neighboring Wood Lake was measured during open-water seasons from 1974 to 1978. The lake had regional differences in chlorophyll concentrations and daily rates of integral primary production in 1974 and 1975 prior to impoundment of the lake. Regions receiving Churchill River flow tended to have higher chlorophyll concentrations and production rates than those regions marginal to the flow. Impoundment of the lake resulted in higher efficiencies of primary production in all regions, as indicated by higher light-saturated rates of carbon uptake per unit chlorophyll and by higher initial slopes of the hyperbolic light response relation of the phytoplankton. Many large basins of the lake had light penetration reduced by high concentrations of suspended sediment from eroding shorelines, while other areas had relatively unchanged light penetration. The increased efficiency of carbon fixation per unit chlorophyll resulted in higher rates of integral production in those regions where light penetration was not greatly affected. Daily rates of integral primary production in lake regions where light penetration had decreased markedly were not significantly different after impoundment because efficiencies of light utilization were higher. Comparison of the mean water column light intensities for those turbid regions with the values of Ik (light intensity at the onset of light saturation) for phytoplankton indicated that these turbid regions are now light deficient on average. Phosphorus deficiency, as indicated by alkaline phosphatase activity per unit ATP, which was present before impoundment, has been eliminated as the mean water column light intensity declined below 5 mEinsteins∙m−2∙min−1. The light environment of a new reservoir can be a significant determinant of integral production, and predicting the consequences of impoundment on phytoplankton production requires accurate prediction of the light environment.

Relationships of Fish Yield to Lake Phytoplankton Standing Crop, Production, and Morphoedaphic Factors

1977 ◽  
Vol 34 (12) ◽  
pp. 2271-2279 ◽  
Author(s):  
Ray T. Oglesby
Keyword(s):  
Primary Production ◽  
Standing Crop ◽  
Crop Production ◽  
Fishery Management ◽  
Cold Water ◽  
Phytoplankton Production ◽  
Fish Yield ◽  
Morphoedaphic Index ◽  
Intensively Managed ◽  
Predicted Values

Fish yield is related to annual primary production, summer phytoplankton standing crop, and the morphoedaphic index for lakes representing a wide variety of typologies by a series of models in the form of log-log regressions. Tentative boundary conditions are established by which lakes inappropriate to the models can be excluded. Confidence intervals for predicted values about the mean are given for the fish yield–phytoplankton standing crop regression. From this relation, potential yields for the lakes studied are reduced from a range of 10,000 to one of 25-fold. Efficiencies with which carbon is transferred from primary production to fish yield vary by 2 to 3 orders of magnitude and are highest for small, intensively managed ponds and lowest for large, deep, cold-water lakes. Models based upon fish yield as a function of phytoplankton production or standing crop are inherently more accurate and subject to fewer exceptions than are those related to morphoedaphic factors. The former appear to be capable of substantial refinement but even in their present state might be employed to make useful predictions for groups of lakes. A suggested supplement to existing approaches in fishery management involves the following sequence: (1) use of expectation-variability diagrams to obtain an overview of the problem, (2) selection of an appropriate model or models to predict yield, (3) prediction of a range of yields, and (4) implementation of regulations proved successful for other lakes in the same yield category. Key words: fish, lakes, phytoplankton, morphoedaphic index, fishery management

Emergence of Chironomidae (Diptera) in Fertilized and Natural Lakes at Saqvaqjuac, N.W.T.

1988 ◽  
Vol 45 (4) ◽  
pp. 731-737 ◽  
Author(s):  
Harold E. Welch ◽  
John K. Jorgenson ◽  
Martin F. Curtis
Keyword(s):  
Primary Production ◽  
Phytoplankton Production ◽  
Experimental Lakes Area ◽  
Natural Lakes ◽  
Before And After ◽  
Mean Size ◽  
Apparent Reason ◽  
Total Primary Production ◽  
Latitudinal Range ◽  
Lake Fertilization

Chironomid emergence was quantified in four small lakes at Saqvaqjuac, N.W.T. (63°39′N), before and after lake fertilization. Emerging biomass responded immediately to increased phytoplankton production, reaching equilibrium the following year. Emergence from the reference lake was extremely variable, for no apparent reason. The emergence – phytoplankton production relationships found by Davies for the Experimental Lakes Area (~49°N) were generally valid for Saqvaqjuac lakes and Char Lake (74°42′), except that (1) biomass was better correlated than numbers because of increased mean size with increasing latitude and (2) total primary production was a better predictor than phytoplankton production alone because benthic photosynthesis increases with increasing latitude. Chironomid production seems to be a predictable function of total primary production throughout the latitudinal range of the small Canadian lakes examined.

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