<i>Desulfovbrio desulfuricans</i> in een chemostaat met sulfaat als beperkende faktor

At this investigation Desulfovibrio was cultured in a chemostate with sulphate as limiting factor and pyruvate as C-source. From the ratio between the consumption of pyruvate and the consumption of sulphate it appears that with increasing D a shift takes place from fermentation to anaerobic respiration until D reaches a value of about 0,1. Then the ratio between fermentation and anaerobic respiration appears to remain constant until D reaches a value of 0,3. With further increasing D a suppression takes place of anaerobic respiration. At an experiment with a surplus of sulphate in the medium the measure of anaerobic respiration remained constant in the investigated interval from D = 0,02 till D= 0,28

Interaction of detritus with abundance of cyanobacteria and microalgae

Detritus particles interact with phytoplankton growth through light attenuation and nutrient retention. A model is described for predicting abundance of cyanobacteria and microalgae in relation to the detritus dynamics in shallow lakes with varying phosphorus load. Steady-state P distribution among cyanobacterial biomass, detritus and the dissolved pool depending on mortality and detritus mineralisation rare was predicted from kinetics for P-limited growth and refractory fraction of the detritus. The depth-averaged irradiance was computed for a constant background attenuation and specific attenuation coefficients of biomass and detritus estimated from field and laboratory data. This light was compared to the light critical to net growth of microalgae based on initial slope of growth vs. irradiance relationship. maximal growth rate and constant maintenance rate. It was predicted that the probability of abundance of microalgae relative to that of cyanobacteria is high at low population loss rates, coinciding with the lowest depth-averaged irradiances at a particular P load. This prediction is consistent with observations on many shallow lakes. [KEYWORDS: detritus; light attenuation; microalgae; phosphorus cycling; shallow lakes Lake lake loosdrecht; oscillatoria-agardhii; plankton communities; phytoplankton; growth; irradiance; shallow; photosynthesis; netherlands; cultures]

Interaction of detritus with abundance of cyanobacteria and microalgae

Detritus particles interact with phytoplankton growth through light attenuation and nutrient retention. A model is described for predicting abundance of cyanobacteria and microalgae in relation to the detritus dynamics in shallow lakes with varying phosphorus load. Steady-state P distribution among cyanobacterial biomass, detritus and the dissolved pool depending on mortality and detritus mineralisation rare was predicted from kinetics for P-limited growth and refractory fraction of the detritus. The depth-averaged irradiance was computed for a constant background attenuation and specific attenuation coefficients of biomass and detritus estimated from field and laboratory data. This light was compared to the light critical to net growth of microalgae based on initial slope of growth vs. irradiance relationship. maximal growth rate and constant maintenance rate. It was predicted that the probability of abundance of microalgae relative to that of cyanobacteria is high at low population loss rates, coinciding with the lowest depth-averaged irradiances at a particular P load. This prediction is consistent with observations on many shallow lakes. [KEYWORDS: detritus; light attenuation; microalgae; phosphorus cycling; shallow lakes Lake lake loosdrecht; oscillatoria-agardhii; plankton communities; phytoplankton; growth; irradiance; shallow; photosynthesis; netherlands; cultures

Optical teledetection of chlorophyll a in turbid inland waters

Determination of subsurface spectral irradiance reflectance by use of a hand-held spectroradiometer and then estimation of chlorophyll a (Chl-a) concentration facilitate assessment of ecological change in turbid lakes, rivers, and estuaries. The method was applied under widely varying solar elevation and weather. Noise due to reflected sky light was evaluated by theory on surface waves and by field data. A strong relationship was established for the shallow and eutrophic freshwater IJssel Lagoon including the River IJssel (The Netherlands) between corrected Chi-a concentrations (3-185 mg m(-3)) and the reflectance ratio for 704 and 672 nm with backscattering derived from the reflectance at 776 nm (R-2 > 0.95; N = 114; Standard error of estimate <9 mg m-3). This relationship adequately predicted Chi-a concentrations in well- mixed and optically deep water in lakes in The Netherlands, the Scheldt Estuary in Belgium and The Netherlands, and Lake Tai in China (N = 40; standard error of estimate <9 mg m(-3)). Floating layers of the cyanobacterium Microcystis in Lake Chao in China were distinguished from homogeneously distributed phytoplankton by reflectance in the violet, blue, and near- infrared wavebands. [KEYWORDS: Ocean color; reflectance; quality; lake; phytoplankton; instruments; system; model; nm]

Some notes on water color in Keweenaw Bay (Lake Superior)

Spectral subsurface irradiance reflectance—intrinsic water color—was derived from above-water radiance measurements using a hand-held spectroradiometer along a transect on Keweenaw Bay, Lake Superior. The reflectance spectra were typical of oligotrophic lacustrine waters. The reflectance peak wavelength shifted from 484 nm at stations farthest offshore to 540 nm near the head of the bay. This change coincided with a decrease in Secchi-disk depth from 16 to 8 m, and an increase in concentrations of chlorophyll a and total suspended matter from about 0.45 to 0.60 mg m–3 and from 0.3 to 0.5 g m–3, respectively. The concentration of chromophoric dissolved organic matter (gilvin), expressed as the absorption of filtrate at 440 nm, varied between 0.11 and 0.2 m–1. Like almost all inland waters, Keweenaw Bay should be classified as a Case 2 water due to the concentrations of gilvin and inanimate particles relative to plankton biomass. A model for chlorophyll-a estimation from spectral reflectance that adequately predicted concentrations in mesotrophic to highly eutrophic Case 2 waters elsewhere gave negative values when applied to the Keweenaw Bay transect. Evidently, there is a need of algorithm development for oligotrophic lacustrine waters. Estimates improved using a modified blue to green band ratio algorithm previously applied for remote sensing of oceanic waters. In optimization of semi-empirical algorithms for estimation of plankton biomass in Lake Superior, absorption by gilvin as well as by inanimate particles merits special consideration. [KEYWORDS: Chlorophyll ; Lake Superior ; remote sensing ; spectral reflectance ; water color]