A model for the light-limited growth of buoyant phytoplankton in a shallow, turbid waterbody

1994 ◽  
Vol 45 (5) ◽  
pp. 847 ◽  
Author(s):  
BE Sherman ◽  
IT Webster
Keyword(s):  
Wind Speed ◽  
Water Column ◽  
Chlorophyll Concentration ◽  
Light Attenuation ◽  
Euphotic Zone ◽  
Limited Growth ◽  
Potential Growth ◽  
Column Temperature ◽  
Turbid Waters ◽  
Neutrally Buoyant

A computer model was used to explore the relationship between buoyancy and the light-limited growth of phytoplankton in very turbid waters. The model simulates the potential growth of phytoplankton as a function of flotation speed, using field observations of photosynthetically active radiation, wind speed, surface-layer thickness (from water-column temperature data), and light attenuation made at Rushy Billabong on the River Murray from 28 November 1991 to 26 March 1992. A unique feature of the model is the simulation of the development and dispersal of surface scums as a function of wind speed. Under nutrient-replete conditions, the model predicted that phytoplankton with a flotation speed of 1-10 m day-1 (typical of Anabaena flos-aquae and Microcystis aeruginosa) would grow up to four times faster than would neutrally buoyant phytoplankton with the same maximum specific growth rate. In the shallow system modelled, high flotation speeds allowed a large proportion of the total population to rise into the euphotic zone shortly after the onset of stratification each day. Surface scums played an important role in maintaining the more buoyant phytoplankton populations close to the water surface. Under the very turbid conditions in the billabong (100 nephelometric turbidity units), self-shading became significant only when the mean chlorophyll concentration in the water column approached 100 mg chla m-3.

Contribution of epiphyte load to light attenuation on seagrass leaves is small but critical in turbid waters

2020 ◽  
Vol 71 (8) ◽  
pp. 929
Author(s):  
Yan Xiang Ow ◽  
Kai Jun Ng ◽  
Samantha Lai ◽  
Siti Maryam Yaakub ◽  
Peter Todd
Keyword(s):  
Water Column ◽  
Light Transmission ◽  
Light Attenuation ◽  
Attenuation Coefficients ◽  
Seagrass Meadows ◽  
Relative Contribution ◽  
Turbid Waters ◽  
Cymodocea Rotundata ◽  
The Relationship ◽  
Epiphyte Load

Quantifying contributors to light attenuation is useful for the management of seagrass meadows. Epiphytic growth on seagrasses can lead to diminished light for the host plant, impairing photosynthesis and growth. Here, we quantify the contributions of the water column and epiphytic load to light attenuation in a Cymodocea rotundata meadow at Chek Jawa, Singapore. Using a modified spectrometer and seagrass mimics (clear polyethene strips) colonised by epiphytes, we determined the relationship between light transmission (400–700nm) and epiphyte load. Subsequently, we derived the percentage of surface light that reaches the leaf surface (PLL) over a range of epiphyte biomass and water-column light-attenuation coefficients (Kd). Results indicated that the relative contribution to light attenuation by epiphytic biomass was greater in clearer waters (Kd<0.5) than in turbid waters. As Kd increases, the amount of epiphytic material required to reduce PLL to minimum light requirement (11%) decreases exponentially. At Chek Jawa, the average epiphytic load was 32mg DW cm−2, which was close to the estimated amount (33mg DW cm−2) required to reduce PLL to 11% at prevailing turbidity levels. Our findings suggest that high epiphyte load is benign in clear waters, but becomes critical in turbid waters.

Phytoplankton Distribution and Light Attenuation in Port Hacking Estuary

1978 ◽  
Vol 29 (1) ◽  
pp. 31 ◽  
Author(s):  
BD Scott
Keyword(s):  
Water Column ◽  
Chlorophyll Concentration ◽  
Light Attenuation ◽  
Suspended Sediments ◽  
Tidal Exchange ◽  
Phytoplankton Distribution ◽  
Relationship Of ◽  
The Relationship ◽  
In Vivo Chlorophyll Fluorescence

The distribution of phytoplankton in a marine dominated estuary is described in terms of in vivo chlorophyll fluorescence, phytoplankton photosynthesis rates at constant irradiance, and the attenuation of solar irradiance by the water column. The phytoplankton distribution was consistent with the physiography and water circulation in the estuary. A method is described for estimating the proportions of suspended sediments, introduced with runoff from the land, which are removed from the estuary by tidal exchange or by sinking. Estimates of the proportions of phytoplankton and detritus in the water column are derived from the relationship of chlorophyll concentration to the extinction coefficient.

scholarly journals The role of sediment-induced light attenuation on primary production during Hurricane Gustav (2008)

2020 ◽  
Vol 17 (20) ◽  
pp. 5043-5055
Author(s):  
Zhengchen Zang ◽  
Z. George Xue ◽  
Kehui Xu ◽  
Samuel J. Bentley ◽  
Qin Chen ◽  
...  
Keyword(s):  
Primary Production ◽  
Water Column ◽  
Chlorophyll Concentration ◽  
Light Attenuation ◽  
Sediment Concentration ◽  
Biogeochemical Model ◽  
System A ◽  
Sensitivity Tests ◽  
The Impact

Abstract. We introduced a sediment-induced light attenuation algorithm into a biogeochemical model of the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) modeling system. A fully coupled ocean–atmospheric–sediment–biogeochemical simulation was carried out to assess the impact of sediment-induced light attenuation on primary production in the northern Gulf of Mexico during the passage of Hurricane Gustav in 2008. When compared with model results without sediment-induced light attenuation, our new model showed a better agreement with satellite data on both the magnitude of nearshore chlorophyll concentration and the spatial distribution of offshore bloom. When Hurricane Gustav approached, resuspended sediment shifted the inner shelf ecosystem from a nutrient-limited one to a light-limited one. Only 1 week after Hurricane Gustav's landfall, accumulated nutrients and a favorable optical environment induced a posthurricane algal bloom in the top 20 m of the water column, while the productivity in the lower water column was still light-limited due to slow-settling sediment. Corresponding with the elevated offshore NO3 flux (38.71 mmol N m−1 s−1) and decreased chlorophyll flux (43.10 mg m−1 s−1), the outer shelf posthurricane bloom should have resulted from the cross-shelf nutrient supply instead of the lateral dispersed chlorophyll. Sensitivity tests indicated that sediment light attenuation efficiency affected primary production when sediment concentration was moderately high. Model uncertainties due to colored dissolved organic matter and parameterization of sediment-induced light attenuation are also discussed.

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.

Phytoplankton Biomass and Water Column Temperature Dynamics of Lake James, NC USA

2004 ◽  
Vol 1 (1) ◽  
pp. 23-26
Author(s):  
Kemal Celik ◽  
James Schindler . ◽  
William Foris . ◽  
Jonathan Knight .
Keyword(s):  
Water Column ◽  
Phytoplankton Biomass ◽  
Column Temperature ◽  
Temperature Dynamics ◽  
Lake James

scholarly journals Drivers of diffusive CH<sub>4</sub> emissions from shallow subarctic lakes on daily to multi-year timescales

2020 ◽  
Vol 17 (7) ◽  
pp. 1911-1932 ◽  
Author(s):  
Joachim Jansen ◽  
Brett F. Thornton ◽  
Alicia Cortés ◽  
Jo Snöälv ◽  
Martin Wik ◽  
...  
Keyword(s):  
Wind Speed ◽  
Water Column ◽  
Atmospheric Stability ◽  
Water Concentration ◽  
Gas Transfer ◽  
Air Concentration ◽  
Subarctic Lakes ◽  
Surface Renewal ◽  
Near Surface ◽  
Functional Relations

Abstract. Lakes and reservoirs contribute to regional carbon budgets via significant emissions of climate forcing trace gases. Here, for improved modelling, we use 8 years of floating chamber measurements from three small, shallow subarctic lakes (2010–2017, n=1306) to separate the contribution of physical and biogeochemical processes to the turbulence-driven, diffusion-limited flux of methane (CH4) on daily to multi-year timescales. Correlative data include surface water concentration measurements (2009–2017, n=606), total water column storage (2010–2017, n=237), and in situ meteorological observations. We used the last to compute near-surface turbulence based on similarity scaling and then applied the surface renewal model to compute gas transfer velocities. Chamber fluxes averaged 6.9±0.3 mg CH4 m−2 d−1 and gas transfer velocities (k600) averaged 4.0±0.1 cm h−1. Chamber-derived gas transfer velocities tracked the power-law wind speed relation of the model. Coefficients for the model and dissipation rates depended on shear production of turbulence, atmospheric stability, and exposure to wind. Fluxes increased with wind speed until daily average values exceeded 6.5 m s−1, at which point emissions were suppressed due to rapid water column degassing reducing the water–air concentration gradient. Arrhenius-type temperature functions of the CH4 flux (Ea′=0.90±0.14 eV) were robust (R2≥0.93, p<0.01) and also applied to the surface CH4 concentration (Ea′=0.88±0.09 eV). These results imply that emissions were strongly coupled to production and supply to the water column. Spectral analysis indicated that on timescales shorter than a month, emissions were driven by wind shear whereas on longer timescales variations in water temperature governed the flux. Long-term monitoring efforts are essential to identify distinct functional relations that govern flux variability on timescales of weather and climate change.

scholarly journals Seabed Resuspension in the Chesapeake Bay: Implications for Biogeochemical Cycling and Hypoxia

2020 ◽  
Vol 44 (1) ◽  
pp. 103-122
Author(s):  
Julia M. Moriarty ◽  
Marjorie A. M. Friedrichs ◽  
Courtney K. Harris
Keyword(s):  
Organic Matter ◽  
Chesapeake Bay ◽  
Water Column ◽  
Primary Productivity ◽  
Environmental Changes ◽  
Light Attenuation ◽  
Sediment Resuspension ◽  
Nitrogen Dynamics ◽  
Biogeochemical Model ◽  
Order Of Magnitude

AbstractSediment processes, including resuspension and transport, affect water quality in estuaries by altering light attenuation, primary productivity, and organic matter remineralization, which then influence oxygen and nitrogen dynamics. The relative importance of these processes on oxygen and nitrogen dynamics varies in space and time due to multiple factors and is difficult to measure, however, motivating a modeling approach to quantify how sediment resuspension and transport affect estuarine biogeochemistry. Results from a coupled hydrodynamic–sediment transport–biogeochemical model of the Chesapeake Bay for the summers of 2002 and 2003 showed that resuspension increased light attenuation, especially in the northernmost portion of the Bay, shifting primary production downstream. Resuspension also increased remineralization in the central Bay, which experienced larger organic matter concentrations due to the downstream shift in primary productivity and estuarine circulation. As a result, oxygen decreased and ammonium increased throughout the Bay in the bottom portion of the water column, due to reduced photosynthesis in the northernmost portion of the Bay and increased remineralization in the central Bay. Averaged over the channel, resuspension decreased oxygen by ~ 25% and increased ammonium by ~ 50% for the bottom water column. Changes due to resuspension were of the same order of magnitude as, and generally exceeded, short-term variations within individual summers, as well as interannual variability between 2002 and 2003, which were wet and dry years, respectively. Our results quantify the degree to which sediment resuspension and transport affect biogeochemistry, and provide insight into how coastal systems may respond to management efforts and environmental changes.

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