Box 21 I Langmuir circulations

Langmuir circulations are elongated, wind-induced convection cells that form at the surface of lakes and of the sea, having characters first formalised by Langmuir (1938). They take the form of parallel rotations, that spiral approximately in the direction of the wind, in the general manner sketched in Fig. 2.26. Their structure is more clearly understood than is their mechanics but it is plain that the cells arise through the interaction of the horizontal drag currents and the gravitational...

Sources and fluxes of available inorganic carbon

Hco3 Determination Water

The sea-level, air-equilibrated concentration of carbon dioxide in water at 0 C is 23 M, falling to 13 M at 20 C say, 0.5-1.0mg CO2 L-1, or 0.15-0.3mgC L-1 . Besides being sensitive to temperature, the equilibrium concentration depends upon the atmospheric partial pressure of CO2, which is, in turn, affected by altitude. In many natural waters, carbonic acid is the only free acid present and, thus, the concentrations of alkalinity base ions , carbon dioxide The pH-carbon dioxide-carbonate...

Photoprotection photoinhibition and photooxidation

Against the background of environmental variability, there may be superimposed variations in the contemporary ambient range of fluctuations, subjecting hitherto supposedly acclimated plank-ters to additional demands of accommodation. Among the most crucial of these is a weakening of the mechanical forcing, either as a result of a sharp reduction in the wind speed or of sharp increase in the photon flux perhaps as the cloud clears or, as is often the case, the coincidence of both events. In all...

Measurement of lightdependent photosynthetic oxygen production

Numerous studies based on oxygen generation in light and darkened bottles were published in the 50 years between 1935 and 1985. Many of the findings were substantially covered in a thorough synthesis by Harris 1978 . Since then, the method has been displaced by more direct and more sensitive techniques. Nevertheless, the experiments based on measurements of photo-synthetic oxygen production in closed bottles suspended at selected depths in the water column yielded consistent generalised results...