Phytoplankton Nutrient Dynamics Research Articles

Phytoplankton nutrient dynamics and flow cytometry based population study of a eutrophic wetland habitat in eastern India, a Ramsar site.

Phytoplankton diversity, their abundance based on flow cytometric (FCM) analysis and seasonal nutrient dynamics were investigated from a waste water fed wetland of Eastern India (88° 24.641′E and 22° 33.115′N). The primary objective of the study was to correlate the seasonal fluctuations in phytoplankton abundance to the environmental variables. Total chlorophyll content and FCM based cell counts were used to characterize and quantify the phytoplankton population. Multivariate statistical methods were employed in predicting the possible relationships between biotic and abiotic variables. Distinct seasonal variations characterized by high abundance during the pre-summer period compared to other seasons were detected. The results indicated that environmental factors like water temperature and nutrients, such as various forms of nitrogen and phosphate, influenced the seasonal phytoplankton accumulation. Cluster analysis and non-metric multidimensional scaling helped analyze the seasonal distribution of phytoplankton based on their composition. The dominant genera among the entire phytoplankton community were Scenedesmus spp. of Chlorophyta, followed by Merismopedia spp. of Cyanoprokaryota. Around 3.7 × 105 phytoplankton mL−1 were recorded during the study period. Due to the very high count of individual species in the community, FCM based counting was applied for determination of Species Diversity Index. The entire population was divided into 13 subpopulations based on the cell sorting method and the seasonal abundance in each sub-population was illustrated.

Influence of a buoyant river plume on phytoplankton nutrient dynamics: What controls standing stocks and productivity?

The influence of the Columbia River plume on phytoplankton rates and biomass accumulation was examined using multiday deckboard incubations as part of the coastal ocean processes River Influences on Shelf Ecosystems field program in August 2005. At a set of five stations encompassing the near‐field plume (three stations) on the Oregon and Washington coasts, treatments consisting of control, added nitrate, and added nitrate with 0.45 μm filtered plume water were used to assess the phytoplankton community response to macronutrients and micronutrients. For a subset of these stations, nutrient (nitrate, ammonium, and ammonium inhibition of nitrate) kinetics were obtained, as well as carbon‐based estimates of productivity. For all experiments, nitrogen (nitrate) was clearly controlling both biomass accumulation and growth rates. Despite the apparent poleward trend toward increasing biomass in this region, there were no obvious differences in phytoplankton physiological capacity, nor were there any symptoms of iron limitation in the short term. We conclude that phytoplankton in this region are predominantly nitrogen limited but that upon release from this limiting factor, phosphorous and/or silicic acid (in waters not influenced by the Columbia River plume) would quickly become limiting. Evidence suggests that the mesoscale differences in phytoplankton biomass between the Oregon and Washington coasts result from a combination of enhanced grazing downstream and the physically retentive and dispersive effects of the plume itself.