Induction Of Enzymes As A Mechanism For The Seasonal Control Of Metabolism In Marine-Invertebrates - Glucose-6-Phosphate Dehydrogenases From The Mantle And Hepatopancreas Of The Common Mussel Mytilus-Edulis-L

1. Glucose-6-phosphate dehydrogenase from the hepatopancreas and mantle tissue of M. edulis was investigated over two years for changes in specific activity (crude enzyme preparations) and the apparent Michaelis constants for G6P and NADP+ (highly purified enzyme preparations). 2. The specific activity of the mantle enzyme was low in summer and autumn and increased in the winter during the time of lipid deposition. In contrast, the specific activity of the hepatopancreas enzyme was high in summer and declined during the autumn and winter. 3. The apparent values for G6P and NADP+ of the mantle enzymechange little during a year. Changes were observed for the hepatopancreas enzyme during the first year but not the second.

Laboratory Simulation Of Chemical Processes Induced By Estuarine Mixing - The Behavior Of Iron And Phosphate In Estuaries

A series of well stirred tank reactors has been shown to provide an adaptable laboratory analogue of a one-dimensional estuarine mixing profile which can be applied dynamically to the study of the chemistry of estuarine mixing. Simulations of the behaviour of iron and phosphate in the low salinity region of an estuary have been achieved with this system. The well documented general features of iron removal, involving rapid aggregation of river-borne colloids, were reproduced. Phosphate removal is attributable in part to the coagulation process, although specific adsorption of phosphate by colloids also appears to be significant.

Nutrient Distributions In An Estuary - Evidence Of Chemical Precipitation Of Dissolved Silicate And Phosphate

Continuous autoanalytical recordings of the axial distributions of dissolved nitrate, silicate and phosphate in the influent freshwater and saline waters of the Tamar Estuary, south-west England have been obtained. Short-term variability in the distributions was assessed by repetitive profiling at approximately 3-h intervals on a single day and seasonal comparisons were obtained from ten surveys carried out between June 1977 and August 1978. Whereas nitrate is always essentially conserved throughout the upper estuary, the silicate- and phosphate-salinity relationships consistently indicate a non-biological removal of these nutrients within the low (0–10%) salinity range. Attempts to quantify precisely the degree of removal and to correlate this with changes in environmental properties (pH, turbidity, chlorophyll fluorescence, salinity, freshwater composition) were mainly inconclusive due to short-term fluctuations in the riverine concentrations of silicate and phosphate advected into the reactive region and to the rapid changes in turbidity brought about by tidally-induced resuspension and deposition of bottom sediment.

Comparison of phosphate uptake rates by the smallest plastidic and aplastidic protists in the North Atlantic subtropical gyre

The smallest phototrophic protists (<3 μm) are important primary producers in oligotrophic subtropical gyres – the Earth's largest ecosystems. In order to elucidate how these protists meet their inorganic nutrient requirements, we compared the phosphate uptake rates of plastidic and aplastidic protists in the phosphate-depleted subtropical and tropical North Atlantic (4–29°N) using a combination of radiotracers and flow cytometric sorting on two Atlantic Meridional Transect cruises. Plastidic protists were divided into two groups according to their size (<2 and 2–3 μm). Both groups of plastidic protists showed higher phosphate uptake rates per cell than the aplastidic protists. Although the phosphate uptake rates of protist cells were on average seven times (P<0.001) higher than those of bacterioplankton, the biomass-specific phosphate uptake rates of protists were one fourth to one twentieth of an average bacterioplankton cell. The unsustainably low biomass-specific phosphate uptake by both plastidic and aplastidic protists suggests the existence of a common alternative means of phosphorus acquisition – predation on phosphorus-rich bacterioplankton cells.