Plankton Photosynthesis Research Articles

Temperature and Antarctic plankton community respiration

Antarctic plankton community respiration rates were determined from in vitro changes in dissolved oxygen. Oxygen consumption rates, measured at in situ temperatures between 0 and 6°C, were found to lie in the range 0.3–3.7 μmol O 2 l −1 per 24 h. Water samples were collected between East Falkland Island and South Georgia, South Atlantic Ocean, and incubated shipboard in the dark at up to 36 temperatures between −2 and 14−C. A respiration rate at each temperature was then determined and used to calculate the temperature coefficient (Q 10 ) of Antarctic planktonic community respiration from the Arrhenius equation. Fourteen Q 0 values lay in the range 1−3, with four further values >5. This range of temperature coefficient values for community respiration is comparable to the published range of values for plankton photosynthesis. Frequency distributions of temperature coefficients for the two processes show similar modal Q 10 5 of 2–3. Thus, this study does not lend support to the hypothesis of a differential response of photosynthesis and community respiration to low temperature.

Comparison of 14C and O2 measurements of phytoplankton production in oligotrophic waters

Present day estimates of primary phytoplankton production are derived almost exclusively from the results of a single method, the 14C technique. 14C methodology is amenable to routine measurement and also has the requisite sensitivity for the large expanses of ocean characterized by low autotrophic biomass. However, there is still great uncertainty as to its ecological interpretations; for example, whether it is measuring net or gross primary production. We report here the first comparison of planktonic photosynthesis based on 14C assimilation with measurements of oxygen flux for an oligotrophic environment of ocean character. We conclude from the results that there is no evidence of persistent errors of any size, unique to the 14C technique, in the measurement of gross production. We also infer, from a consideration of the rates themselves, that in vitro methodology is not biased with respect to in situ photosynthesis.

Model of light penetration in a turbid lake

The relationships governing the penetration and attenuation of light in natural water bodies are of great importance to studies and models of photosynthesis and water quality in general. Quantitative expressions which give the rate of reflection of incident light at a water surface and absorption and scattering of light by suspended inorganic (clay) particles and by suspended organic particles (phytoplankton and detritus) in the water are developed herein for Lake Chicot, a highly turbid lake in Arkansas. Differentiation between inorganic and organic types of particles reveals their respectively different effect on light penetration. In addition, light attenuation is also a function of wavelength. Therefore, three wave bands are distinguished. In addition, light as seen by flat plate sensors and spherically integrated light as experienced by an algal cell are distinguished. To facilitate modeling of planktonic photosynthesis, a relationship between incident total radiation measured above the water (as available from a weather station) to underwater photosynthetically active radiation has been developed for Lake Chicot. The work described was exploratory and relied exclusively on Lake Chicot data. The results were intended for use in a water quality simulation model.

Satellites for the study of ocean primary productivity

Estimates of global marine primary productivity are currently based upon the 14C method for determining rates of plankton photosynthesis and upon the relatively sparse data available using shipboard sampling techniques. With recent advances in remote sensing and in multiplatform (ship, aircraft, and satellite) sampling strategies, it is now possible to significantly lower the variance in estimates of phytoplankton abundance and of population growth rates. Multiplatform sampling strategies are essential to assess the mean and variance of phytoplankton biomass on a regional or on a global basis. The relative errors associated with shipboard and satellite estimates of phytoplankton biomass and primary productivity, as well as the increased statistical accuracy now possible from the utilization of contemporaneous data from both sampling platforms, are discussed. It is shown that one of the more exciting and potentially useful aspects of oceanographic research today is our new ability to view large areas of the ocean synoptically.

Phytoplankton photosynthesis and carbon‐specific growth: Light‐saturated rates in a nutrient‐rich environment1

Light‐saturated photosynthesis from short term (2 h) and daily (24 h) measurements were correlated in phytoplankton of two size fractions, net plankton dominated by diatoms and nanoplankton dominated by chlorophytes. Diurnal variations in short term photosynthesis were characterized by a midday maximum and tended to be of a greater amplitude in net plankton than in nanoplankton populations. Nanoplankton photosynthesis varied on a seasonal scale while net plankton photosynthesis varied on a daily scale—a phenomenon which appeared to be reflected in the relationship between short term photosynthesis and growth. The latter, calculated from daily photosynthesis, increased exponentially with temperature and was more closely coupled to short term photosynthesis in nanoplankton than in net plankton populations. These differences seem to be related to the way in which the two size fractions are distributed in time and space as a consequence of interactions between physical process and time‐dependent growth.

Internal phosphorus loading in a shallow eutrophic lake

Internal loading of phosphorus has been implicated as a major eutrophicating factor in Long Lake, Washington (Kitsap County). As a result of such loading, summer total phosphorus concentrations approach or exceed 100 μgP l −1. Most of the summer loading of phosphorus is thought to have been released directly from the rich, flocculent sediment in the mid and northern part of the lake as a result of high pH (up to 10) related to phytoplankton photosynthesis. The lake also supports a dense submersed macrophyte crop (areal weighted mean dry weight of about 220 g m −2) composed primarily of Elodea densa. Although excretion of phosphorus from healthy E. densa was found to be minimal, the potential contribution of P indirectly from sediment via macrophyte uptake and subsequent decomposition in the winter was on the order of 200–400 kg yr −1 or about 25–50% of the external loading. Nevertheless, loading of phosphorus during predrawdown summers is thought to have originated largely as a direct release from sediment due to high pH. Estimates of sediment phosphorus release determined from laboratory experiments, mass balance and core analyses ranged from 2.2 to 5.6 mg m −2 day −1. As a component of the restoration program, the lake (mean depth of 2 m) was drawn down nearly 2 m for 4 months during the summer and fall of 1979. The lake's trophic status was expected to improve due to sediment consolidation and/or macrophyte reduction. The drawdown resulted in an 84% reduction in macrophyte biomass in 1980 but minimal sediment consolidation (0.1 m). Winter decomposition of the much smaller macrophyte crop, apparently provided insufficient phosphorus in the spring to stimulate phytoplankton and to enrich midlake sediments, which has probably occurred in previous years. Low water column pH during the postdrawndown summer of 1980 resulted from relatively low rates of plankton photosynthesis. During the summer of 1980 internal loading of phosphorus was reduced and total phosphorus remained below 50 μg l −1.

Effects of heavy metals in combination with NTA, humic acid, and suspended sediment on natural phytoplankton photosynthesis.

The tested heavy metal concentrations: Cd, Cu≥5·10−8M, Zn, Pb≥5·10−7M, Hg≥5·10−9M, and a mixture with the concentrations of each metal ten times more dilute, had inhibitory effects on the photosynthesis of phytoplankton from Lake Tyrifjorden. A moderate increase in the water's turbidity or colour reduced the biological availability of the metals and thus their effect on the photosynthetic rate. The increase in anthropogeneous metal load which has taken place in most watercourses may thus be counteracted by the natural influence of dissolved organic matter and by processes in lakes and rivers causing increased turbidity. NTA led to detoxification of Cd, Zn, Pb, and Cu while Hg and the metal mixture became more toxic. An increase in NTA concentration may be the result if this substance comes into use as a substitute for phosphorus in detergents. In Lake Tyrifjorden this may have some unwanted implications since the sediments in the deeper part of the lake are severely contaminated by mercury (HONGVE and SKOGHEIM unpubl.), and NTA may release this as an NTA-Hg complex to the water (CHAU and SHIOMI 1972). NTA complexations of mercury adsorbed to the sediment may thus give a new and quantitatively important contribution to the internal cycle of mercury in the lake. It will also give directly, without microbiological methylation, a substance which may affect the plankton photosynthesis at a concentration which is only a little higher than the present concentration of mercury in the water.

Phytoplankton production in a turbid, temperate salt marsh estuary

Maximum rates of particulate formation ( P max) by phytoplankton in the Wassaw Sound estuary (Georgia U.S.A.) average 20.2 mg C m −3 h −1. Annual primary production is about 90 g C m −2. The point at which plankton photosynthesis is saturated with light ( I k ) is lowest during winter. Short-term temperature fluctuations cause a shift in I k paralleling the seasonal relationship of I k versus temperature. Seasonal changes in P max are also closely related to temperature in the estuary. Temporal and spatial variation of both P max and light attenuation is considerable. The marsh appears to be a net consumer of photosynthetically active phytoplankton cells. Estuarine flushing by storms and rivers spills the accumulated estuarine phytoplankton into the nearshore zone where the much more favourable light conditions leads to a dramatic increase in production per m 2.

Diel and Annual Cycles of Net Plankton Photosynthesis in Lake Ontario

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.

Potential sources of error in the measurement of low rates of planktonic photosynthesis and excretion.

THE introduction of liquid scintillation counting techniques to the study of aquatic productivity1–3 has stimulated interest in the accurate determination of low rates of algal photosynthesis, such as occur in tropical waters or in deep living phytoplankton populations. Attention is also being directed to the measurement of soluble extracellular products of photosynthesis4. Our studies have revealed some potential sources of interference in the widely used 14C technique when used to study low rates: (1) retention of NaH14C03 by filters; (2) passive adsorption of radioactivity by filters and/or seston and (3) soluble and insoluble radioactive impurities in commercially available NaH14C03.

Planktonic photosynthesis and the environment of calcium carbonate deposition in lakes

Planktonic photosynthesis and the environment of calcium carbonate deposition in lakes

Influence of Surface Illumination on Plankton Photosynthesis in Danish Waters (56° N) throughout the Year

Influence of Surface Illumination on Plankton Photosynthesis in Danish Waters (56° N) throughout the Year