Areal Production Rates Research Articles

Resource recycling with algal cultivation: environmental and social perspectives

Efficient use and recycling of resources by utilizing nutrients of waste water and CO2 from flue gases are considered through comparing two conceptual systems: a conventional small scale waste water treatment plant (base case) and a waste water treatment plant combined with algae cultivation unit (algae case). The used algae case concept is based on interviews of experts working with algae cultivation in Finland. Hotspots related to the algae case are assessed from environmental perspectives. According to model calculations, in high latitudes effective algae production may be achieved, although the areal production rates are very low in winter. In the algae case concept nutrients of waste water can be more effectively recycled using bio-based chitosan as flocculant. Also energy is produced in the biogas production plant, which increases the resource recycling of the algae case. When considering the energy balance, a positive net energy ratio (NER) >1 is possible to achieve with maximum methane production potential of algal biomass.

Ecosystem-Scale Rates of Primary Production Within Wetland Habitats of the Northern San Francisco Estuary

Salt marsh restoration is hypothesized to provide shoreline stabilization, increased fish habitat, and organic carbon subsidies for estuarine food webs. Organic carbon comes from diverse primary producers that differ in carbon fixation rates and areal extent within wetland systems. This study was designed to obtain some of the first estimates of the relative contribution of different primary producers to total organic carbon production within open water and tidally flooded wetlands of the northern San Francisco Estuary (SFE). Carbon fixation rates of phytoplankton, microphytobenthos, and low marsh emergent vegetation were measured in two natural and four restoring wetlands in 2004. Areal (m2) rates of carbon fixation were greatest for low marsh vegetation, while phytoplankton and microphytobenthos rates were one and two orders of magnitude lower, respectively. However, when areal production rates were scaled to the amount of habitat available for each primary producer group, the relative importance of each group varied by location. Given that each primary producer group supports a different subset of estuarine consumers, the type of food subsidy desired should influence the amount open water channel, mudflat and low marsh area restored. Large-scale wetland restoration activities should consider the types of primary producers likely to occupy restored habitats when estimating future food web impacts.

Biogas production from an anaerobic pond treating domestic wastewater in Burkina Faso

The production of biogas and its composition from an anaerobic pond treating domestic wastewater have been studied in the Sudano-Sahelian climate of Burkina Faso. The biogas production was measured from March 2010 to March 2011 using a floating static chamber, and the composition was analysed using a micro-gas chromatograph. The composition of biogas produced was relatively constant with time. The major component of the biogas by volume was CH4 which accounted for an average of 80.5%, N2 for 11.8%, O2 for 5% and CO2 for 2.5%. The mean areal production rates of biogas and methane respectively were 121 and 97 L m-2 d-1. The mean methane production rates were 248 L kg-1 COD removed and 588 L kg-1 VSS removed. The average daily volume of biogas and its corresponding methane were 5.73 and 4.63 m3 d-1, respectively, equivalent to a ratio of 7.3 m3 CH4 per capita-year. The conversion of this methane production to electricity could reduce the CO2 equivalent greenhouse gas emission from petrol combustion. This study revealed that the conversion of an anaerobic pond to an anaerobic lagoon digester with the capture and reuse of biogas would be an interesting option for wastewater treatment in the warm conditions of Sudano-Sahelian climate of Burkina Faso.

Synchronization of fluid-dynamics related and physiological time scales and algal biomass production in thin flat-plate bioreactors

Experiments on ultrahigh density unicellular algae cultures in thin flat-plate bioreactors (thickness ≤2 cm) indicate that: i) Optimal areal biomass production rates are significantly higher than in traditional ponds or raceways, ii) productivity grows for radiation levels substantially higher than one sun; saturation emerging, possibly, at intensities of about four suns, and iii) optimal volumetric and areal production rates as well as culture densities increase as reactor thickness is reduced. The observations are reproduced within the framework of a simple model, which takes into account the random motion of cells across the reactor thickness, and the competing effects of two physiologically significant time scales. These are TR, the time that elapses from the moment a reaction center has collected the number of photons required for one photosynthetic cycle until it is available again for exploiting impinging photons (1–10 ms), and TW, an average of the decay time characteristic of photon loss processes (several ms to several tens of ms).

Microalgae mass culture: the constraints of scaling-up

There is overwhelming evidence that microalgae would be the logical source of oils for biodiesel production, the best option for CO2 sequestration and numerous other applications. However, this apparent lucrative approach is still in its infancy. In order to impact on global energy needs, bioremediation and other potential applications, vast quantities of biomass must be produced at a reliable rate and as cost-effective as possible. When extrapolating volumetric rates from laboratory or small-scale outdoor cultures to large-scale outdoor areal production rates, it becomes apparent that many of the potential claims are either misleading or still only a dream. Open raceway ponds are at present the only feasible culture system for the production of millions of tons of biomass. To date, at best photosynthetic efficiencies of around 1.2% have been achieved, but with present understanding and know-how efficiencies of double that should be achievable, especially when vertical mixing is increased in raceway ponds.

Considerations for the maximum production rates of triacylglycerol from microalgae

Abstract In recent years, a wide variety of photobioreactors have emerged for producing triacylglycerol (TAG) from microalgae as a feedstock for biodiesel with wildly varying forecasts of TAG and biomass production rates. This research describes the general photobioreactor concept and the dominating factors that determine microalgal production and the maximum attainable production rate of TAG. The information necessary for such an assessment is obtained from published articles and the results are compared to published photobioreactor production rates. Results indicate that at most 9% conversion of available solar energy to TAG is thermodynamically possible, resulting in an annual areal production rate of no more than 23 l m −2 a −1 . Given photosynthetic efficiencies and TAG contents of microalgae currently reported, production rates of no more than 15.8 l m −2 a −1 should be anticipated.

Upper limits of photosynthetic productivity and problems of scaling

Some 1,370 W m−2 of light energy reaches the outer atmosphere of earth and on average only 240 W m−2 reaches the earth’s surface. Only a fraction of this is used to fix CO2 through photosynthesis, and efficiencies ranging from 0.1−8% for total irradiance have been reported. The theoretical maximum quantum efficiency of carbon fixation is 0.125 mol C (mol quanta)−1 which relates to a maximum productivity of about 12 g C m−2 day−1 or 29.8 g(dw) m−2 day−1. This could increase to a maximum of 200 g(dw) m−2 day−1 in intermittent light of high frequencies, which is on average eight times higher than the average measured under field conditions where rates approaching 25 g(dw) m−2 day−1 are considered high. Several possibilities exist for achieving higher yields and photosynthetic efficiencies, such as limiting the antennae sizes and pulsing light at frequencies equivalent to electron turnover in the electron transport chains of photosynthesis. Scaling from laboratory experimental conditions to large commercial photobioreactors is a major stumbling block and may be the single most important factor responsible for the overall low reported areal production rates.

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

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 (May–October) 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.

Fluxes of inorganic carbon from two forested catchments in the Appalachian mountains

AbstractThis study uses long‐term records of stream chemistry, discharge and air temperature from two neighbouring forested catchments in the southern Appalachians in order to calculate production of dissolved CO2 and dissolved inorganic carbon (DIC). One of the pair of catchments was clear‐felled during the period of the study. The study shows that: (1) areal production rates of both dissolved CO2 and DIC are similar between the two catchments even during and immediately after the period of clear‐felling; (2) flux of total inorganic carbon (dissolved CO2+ DIC) rises dramatically in response to a catchment‐wide acidification event; (3) DIC and dissolved CO2 are dominantly released on the old water portion of the discharge and concentrations peak in the early autumn when flows in the study catchments are at their lowest; (4) total fluvial carbon flux from the clear‐felled catchment is 11·6 t km−2 year−1 and for the control catchment is 11·4 t km−2 year−1. The total inorganic carbon flux represents 69% of the total fluvial carbon flux. The method presented in the study provides a useful way of estimating inorganic carbon flux from a catchment without detailed gas monitoring. The time series of dissolved CO2 at emergence to the stream can also be a proxy for the soil flux of CO2. Copyright © 2005 John Wiley & Sons, Ltd.

Measuring production of Halodule wrightii: additional evidence suggests clipping underestimates growth rate

Growth rates of Halodule wrightii determined using the traditional method of clipping and reharvesting were compared to those determined using the hole-punching method in four populations distributed in coastal lagoons of the Yucatan Peninsula, Mexico. For three of the four populations, clipped shoots revealed 38–56% lower growth rates than punched shoots. The decrease in leaf production per shoot and on an areal basis in clipped shoots compared to punched shoots resulted from generally lower new leaf length, and, of equal or greater importance, leaf width of these shoots. Thus, the clip and reharvest method for assessing H. wrightii leaf production yielded underestimates. Leaf-punching is a convenient method in populations characterized by relatively broad leaves, such as those in Yucatan lagoons. From these populations, the highest published values for leaf elongation rates of H. wrightii to date (11.7–20.6 mm shoot −1 d −1) and summer areal production rates of 4.2–5.8 g dw m −2 d −1. Long-term production data for this species are crucial for managing subtropical coastal environments. Because contrasting methods have been employed to estimate the growth of H. wrightii, spatial and temporal comparisons of production from published reports are difficult to make, and a unified robust method for estimating growth rates and areal production of this seagrass is needed.

Methyl mercury dynamics in littoral sediments of a temperate seepage lake

The sites and rates of methyl mercury (MeHg) production and transport in littoral zone sediments were investigated at Pallette Lake in northern Wisconsin. In littoral areas where groundwater inflow occurs, sulfate supply from groundwater creates profiles of electron acceptors (sulfate) and donors (methane, sulfide) that are reversed from those found in sediments whose sulfate supply is delivered from overlying water. The highest MeHg concentrations in porewaters and the maximal advective MeHg flux rates (4.5-61.7 ng ·m-2 ·day-1) were observed in the spring, while highest bulk phase concentrations occur later in the summer. These estimated MeHg fluxes are greater than the mean areal production rates estimated previously for the water column and are similar to the atmospheric flux. Gross MeHg production was measured using the addition of 203Hg as a tracer to sediments. The depth at which maximal 203Hg methylation occurred coincided with the observed maximums in solid-phase and porewater MeHg concentrations. Because input, advection, and accumulation of MeHg in these sediments were measured directly, an independent estimate of MeHg production could be made and compared with 203Hg-derived rates. This comparison suggests that that the 203Hg tracer method provides reasonable estimates of gross methylation rates and that a substantial fraction of solid-phase Hg is available for methylation.

Size-fractionated phytoplankton production in western Agulhas Bank continental shelf waters

Carbon-14 measurements of community and size-fractionated production during a mid-winter, spring and three summer research cruises in stratified continental shelf waters of the western Agulhas Bank (South Africa) are presented. Auxilliary measurements included chlorophyll a, nitrate concentrations and thermal profiling of the water column. During the winter and spring surveys, the mixed layer extended deeper than the euphotic zone, with nitrate and phytoplankton biomass being evenly distributed through the euphotic zone. Production maxima occurred at the 40–90% surface irradiance light depths, with some evidence of surface photoinhibition. All surveys during summer months (December–January) showed a thermally stratified euphotic zone ( Z eu0.5%/ Z m= 1.1–2.2), with a well defined nitracline within the thermocline. A subsurface chlorophyll maximum (0.5–6 μg l −1), situated at the 3–10% surface irradiance light depth and closely associated with the region of maximum nitrate gradient, was typical of summer measurements. The primary production maximum was located at the depth of the subsurface chlorophyll maximum only on limited occasions, primarily when conditions of a deep thermocline (>35 m) prevailed. During surveys when a shallow (<30 m) thermocline was observed, the primary production maximum occurred frequently at the 90 and 100% surface irradiance intensities. Average integrated production values ranged between 95 and 289 mg C m −2 h −1. Minimum areal production rates were observed during winter (July). Maximum euphotic zone production was measured during the spring survey in western Agulhas Bank waters (347 mg C m −2 h −1). The <15 μm size-fraction accounted for 62–97% of total primary production during mid-winter and one summer survey. During the spring survey with stabilization of a winter mixed euphotic zone, and two summer surveys where a shallow (<35 m) thermocline persisted, production was predominantly by the netplankton >15 μm size-fraction (60–87%). Periods of enhanced netplankton growth may be crucial for the sustaining of the large biomass of spawning anchovy present in western Agulhas Bank waters. Vertical profiles, the subsurface chlorophyll and production maximum and size-fractionated production measurements are discussed with relevance to the control of phytoplankton production and potential trophic fluxes in Agulhas Bank waters.

Effects of the isoetid macrophytes Eriocaulon septangulare and Lobelia dortmanna on the periphyton of littoral sediments

Plants of an isoetid form are common in soft-water lakes and can increase surface area available for periphyton development. The effects of the macrophytes Eriocaulon septangulare With. and Lobelia dortmanna L. on the productivity of periphyton overlying sediments were evaluated by comparing periphyton from macrophyte-sediment treatments with periphyton from sediment treatments in four lakes. Areal productivity (expressed on the basis of underlying sediment area), chlorophyll a standardized productivity, and chlorophyll a biomass of a loosely associated component of the epiphyton of Eriocaulon and Lobelia were similar and not significantly different from that measured for periphyton on sediments. The areal productivity (expressed on the basis of leaf area) of an attached epiphyton component was only 10–20% of rates measured for the loosely associated component. The concentration of leaf area over sediments did not appear to affect areal production rates of epiphyton components over the range 1:0.4 and 1:3.8 sediment area to leaf area. Periphyton productivity is likely higher in areas of isoetid macrophytes than in areas of sediment alone because of the contribution of the attached component of the epiphyton, which is proportional to the leaf area present. Key words: periphyton, isoetid, soft water, productivity, Eriocaulon, Lobelia.

The Utility of Light-Saturation Models for Estimating Marine Primary Productivity in the Field: A Comparison with Conventional "Simulated" In Situ Methods

Primary production rates derived from model photosynthesis–light (P–l) curves and daily solar radiation data were compared with direct measurements using "simulated" in situ incubations in arctic and temperate marine waters. On the average, model estimates were slightly higher in surface waters and significantly lower at the bottom of the euphotic zone (1% light level) than were the measured values. This could be partially explained by spectral differences in incubation light sources. However, areal production rates were statistically indistinguishable. Use of P-l models without a photoinhibition term and incorporating P-l pararmeters from mixed-layer populations gave the best overall agreement with directly measured production rates.

Important Factors for Estimating Annual Phytoplankton Production in the Experimental Lakes Area

Annual phytoplankton growth rates from 21 lakes in the Experimental Lakes Area (ELA) for the 4-yr period 1973–76 are reported. The coefficient of variation of production in most lakes over this period was about 20%. This variability was the same for both control and experimental lakes. Subthermocline populations were quantitatively unimportant in eutrophied basins but up to 50% of annual production occurred in hypolimnion chlorophyll peaks in some transparent control lakes. The exact details of chlorophyll distribution as monitored with an in vivo fluorometer are unnecessary for accurate measurements of production, even in lakes having hypolimnion chlorophyll peaks. Annual production rates were about 80% of the rates predicted with simulated cloudless weather. The common practice of not correcting production estimates for basin morphometry when reporting areal production rates resulted in overestimation of productivity by roughly 20%. The results indicate several ways for simplifying the numerical primary production model.Key words: production, morphometry, models, limnology, Experimental Lakes Area, incubator