Evidence for phytoplankton succession and chromatic adaptation in the Sargasso Sea during spring 1985

Abstract

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

Assessing the role of dust deposition on phytoplankton ecophysiology and succession in a low-nutrient low-chlorophyll ecosystem: a mesocosm experiment in the Mediterranean Sea

“…This result underlines the high nutrient concentration-requirement of this class for growth (in agreement with nutrient availability after the second dust addition), and is consistent with the presence of Chlorophyceae (at least the picophytoplankton size class) in DCM layers of oligotrophic ecosystems (Brunet et al, 2006. Chlorophyceae occurrence in the DCM has been mainly related to their pigment properties, and notably to the presence of Chl b, which is particularly suited to exploit the dim blue-light environment of such depths (Bidigare and Marra, 1990;Brunet et al, 2006). By comparing this study with previous ones (Brunet et al, 2006, we can, therefore, assume that both the low light environment and nutrient availability are the main triggers controlling the presence of nano-and microphytoplanktonic Chlorophyceae in the DCM.…”

Distribution and chromatic adaptation of phytoplankton within a shelf sea thermocline

“…We consider the hypothesis that bottomup processes (nutrient and light availability) cause these observed gradients. We show that pigment concentrations and phytoplankton light absorption characteristics conform to vertical gradients in the spectral light field such that the phytoplankton were chromatically well adapted to the spectral quality of irradiance at their respective depths in the water column (Takahashi et al 1989;Bidigare et al 1990a;Lutz et al 2003). Further, we illustrate that phytoplankton cell sizes increased with depth on the nitrate gradient.…”

Seasonal and interannual variability of ocean color and composition of phytoplankton communities in the North Atlantic, equatorial Pacific and South Pacific

“…1. For the purpose of diagnosing the regional and seasonal composition changes of the phytoplankton, we used pigments indexes proposed by Bidigare et al (1990) andClaustre (1994). These indexes are based on the observation that fucoxanthin generally characterizes Counts of picoplankton cells are also routinely made on the GeP&CO cruises using flow Cytometry.…”