Peak Chlorophyll Research Articles

Primary production and respiration of the phytoplankton of the Rivers Thames and Kennet at Reading

SummaryDuring the period April 1967‐ApriI 1968 the phytoplankton production and respiration of the River Thames and its tributary, the River Kennet, were measured at approxi‐mately 2‐week intervals using the light and dark bottle technique. Concentrations of chlorophyll and pheopigment were determined weekly. On fourteen occasions sets of light and dark bottles were rotated in a specially designed apparatus, and production and respiration values obtained were found to be 1·38 ± 0·31 times higher than in stationary bottles at identical depths over the same period. There was little horizontal, vertical or diurnal variation in chlorophyll concentration showing that the water was well mixed. Peaks of chlorophyll were found in spring, summer and autumn in the Thames (max. 219 mg/m3) but there was very little variation in the Kennet (max. 38·2 mg/m3). In both rivers lowest concentrations were found during winter. Pheo‐pigment concentration was low in both rivers for most of the period although in the Kennet this represented on average 50% of the pigments present. In the Thames a peak of pheopigments(1·33–5 mg/m3) was associated with the autumnal bloom and repre‐sented 61 % of the total pigments. No pheopigments were detected during the spring bloom. The average concentration of suspended organic matter was identical in both rivers but in the Thames over 25 % was due to phytoplankton and in the Kennet almost 95 % was non‐algal.In the Thames, net oxygen production reached a peak in May (10·81 gO2/m2/day) and was negative from November to February (min. −0·45 gO2/m2/day). In the Kennet, maximum production also occurred in May (0·85 gO2/m2) but was negative from the middle of May until the following March. The average annual net production was 1250 and −78 g O2/m2 in the Thames and Kennet respectively.Respiration rates showed similar fluctuations being 4·59 g O2/m2/day in spring in the Thames to 0·09 g O2/m2/day in November. The Kennet was almost always lower (1·05–0·34 g O2/m2/day. The average annual respiration was almost three times higher in the Thames than in the Kennet (641–228 g O2/m2).Various factors which might influence production are discussed. The average net efficiency ofthe Thames phytoplankton fell within ranges described from other rivers. Net efficiencies ofthe Kennet were almost always negative.In the Thames it appeared that net production could be explained as a function of solar radiation, chlorophyll concentration and euphotic depth.

CHANGES IN ABSORBANCE SPECTRUM OF THE DIATOM PHAEODACTYLUM TRICORNUTUM UPON MODIFICATION OF PROTEIN STRUCTURE1,2

SUMMARYChanges in the absorbance spectrum, of the diatom Phaeodactylum tricornutum which are brought about by heat, urea, stilt, and formaldehyde have been studied. The changes brought about by all agents are similar. Each converts cell suspensions from orange‐brown to yellow‐green. This color change results from an increase in absorbance in the blue and a decrease in absorbance in the green. All agents, except salt, also bring about an increase in absorbance in the red at wavelengths below that of the red peak of chlorophyll, and a decrease in absorbance at longer wavelengths. On heating cells, the absorbance change in the green occurs more rapidly than the changes in the blue and red. The converse is true when cells are treated with 4 M NaCl. Heat or formaldehyde treatments chemically modify chlorophyll pigments which are present in untreated cells. The change in absorbance in the green is probably due to changes in the molecular environment of fucoxanthin which, results from protein modification. The changes in the blue and red are at least partly due to chemical changes in chlorophylls, but may also be due, in part, to protein modification.

Photoelectronic effects in organic materials. I. Chlorophyll-chloranil lamellar systems.

Abstract— Photoinduced electron transfer in lamellar composites of chlorophyll a and p‐chloranil has been shown to lead to a voltaic effect. The photovoltage spectral response peaks at the absorption peak of chlorophyll in the red region, indicating that chlorophyll itself is the light absorbing species. Maximum power output of the system is approximately 10‐15 W. A dependence of photovoltage on the square of the incident intensity suggests a bi‐excitonic mechanism for charge separation.

Studies of chlorophyll-lipid-water systems.

Preliminary studies of the electronic absorption spectra of chlorophyll molecules in aqueous glycolipid and phospholipid dispersions are reported. The spectra show a shift for the red peak of chlorophyll of some 10 millimicrons to longer wavelength compared with the spectrum of chlorophyll in ether. Photochemical studies were carried out with cytochrome c incorporated into the aqueous layers separating the lipid bilayers.

ヒトエグサの傷害・生死の徴候について

The injured or dead thalli of Monostroma are rather difficult to distinguish from the normal ones either by naked eye or by microscopic observation. Vital staining with methylene blue, neutral red, toluidine blue or rhodamin B gives also an unsatisfactory result. Comparing the spectral absorption curves of whole thalli, increased grade of injury is accompanied by lowering of absorbance over the visible range including the specific peaks of chlorophyll and carotene. Ethanol extracts of such thalli also give changes in spectral absorption nearly in parallel with the thalli themselves. The treatment of thalli with a tetrazolium salt (TTC) gives a satisfactory result corresponding to the grade of injury of cells. But it needs to use a rather high concentrated solution of TTC (4mg./cc), to evacuate sufficiently, and to incubate at 30°C. adequately.