Measurements of photosynthetic p~g m e n t s , nutnents, spectral Irradiance and vanous physical parameters were performed in the western Sargasso Sea (35"N, 70°W) to ~n v e s t~g a t e the factors affecting phytoplankton blomass dlstribut~ons Algal plgment concentrations and c o m p o s~t~o n s measured during spring 1985 showed cons~derable time-dependent v a n a t~o n s which were cons~stent with those documented by dlrect mlcroscoplc observation D u r~n g early Apnl, 2-fold Increases In chlorophyll a and fucoxanthln were measured on a relatively short tlme scale of days The presence of a d~atom-dominated community malnly specles of the genera Rhlzosolen~a and Chaetoceros, suggested that we were witnessing a stage of the spring bloom Upon return to thls location 2 wk later, the diatom bloom was replaced by a considerably more diverse phytoplankton assemblage consisting of prymnes~ophytes, cyanobacter~a, d~noflagellates, green algae (~ncludlng praslnophytes) and d~a t o m s The vert~cal structures d~splayed by ~n d i v~d u a l accessory plgments dunng Apnl were markedly simllar and suggest that the major phytoplankton taxa were not un~formly distributed In the upper 200 m The phytoplankton were d~s t r~b u t e d as broadly overlapp~ng layers, 1~1th cyanobacterla and diatoms most abundant In the m~x e d layer, prymnesiophytes at lntermed~ate depths, and green algae (Including prasinophytes) deeper In the water column Results p r o v~d e descnptive evidence for a rapid succession of chromatically-adapted phytoplankton during springtime in the Sargasso Sea

No abstract

The relationships between beam attenuation spectra, chlorophyll and pheophytin pigment concentrations, and particle size distributions are examined for a coastal region (Monterey Bay area) believed to have negligible concentrations of terrestrially derived dissolved organic compounds (during May 1977) but large quantities of phytoplankton and resuspended sediments. It was found that the slope of the beam attenuation spectra increases when the hyperbolic slope of the size distribution increases. The magnitude of this increase in slope was consistent with calculations based on a range of particle diameters from 0.5 to 30 microm, so that it would be possible to predict the slope of the particle size distribution if the slope of the beam attenuation spectra is known. The ratio of chlorophyll and pheophytin pigments to suspended volume concentrations affected the beam attenuation spectra to a lesser degree and in a more complex manner. Because of the strong effect of slope, it was concluded that the chlorophyll and pheophytin pigment content of suspended particles could not be efficiently predicted by means of beam attenuation measurements.

No abstract

A simple heat budget model for a radiation‐dominated mixed layer of constant depth is presented. In this model the influence of the vertical irradiance (heat flux) profile is examined by means of the Jerlov [1976] optical water type classification. It is shown that the vertical irradiance profile is important in determining the mixed layer heating rate. The heating rate varies greatly as a function of water type, mixed layer depth, and diffusivity beneath the mixed layer, ranging from 0.098°C/day for oceanic water type I with a mixed layer depth of 20 m and diffusivity beneath the mixed layer of 1.0 cm2 s−1 to 0.316°C/day for coastal type 9 with a mixed layer depth of 10 m and zero diffusivity beneath the mixed layer, a variation of more than a factor of 3.