Effects of spatial and temporal variability of turbidity on phytoplankton blooms

Abstract

A central challenge of coastal ecology is sorting out the interacting spatial and temporal components of environmental variability that combine to drive changes in phytoplankton biomass. For 2 decades, we have combined sustained observation and experimentation in South San Francisco Bay (SSFB) with numerical modeling analyses to search for general principles that define phytoplankton population responses to physical dynamics characteristic of shallow, nutrient-rich coastal waters having complex bathymetry and influenced by tides, wind and river flow. This study is the latest contribution where we investigate light-limited phytoplankton growth using a numerical model, by modeling turbidity as a function of suspended sediment concentrations (SSC). The goal was to explore the sensitivity of estuarine phytoplankton dynamics to spatial and temporal variations in turbidity, and to synthesize outcomes of simulation experiments into a new conceptual framework for defining the combinations of physical-biological forcings that promote or preclude development of phytoplankton blooms in coastal ecosystems. The 3 main conclusions of this study are: (1) The timing of the wind with semidiurnal tides and the spring-neap cycle can significantly enhance springneap variability in turbidity and phytoplankton biomass; (2) Fetch is a significant factor potentially affecting phytoplankton dynamics by enhancing and/or creating spatial variability in turbidity; and (3) It is possible to parameterize the combined effect of the processes influencing turbidity -and thus affecting potential phytoplankton bloom development -with 2 indices for vertical and horizontal clearing of the water column. Our conceptual framework is built around these 2 indices, providing a means to determine under what conditions a phytoplankton bloom can occur, and whether a potential bloom is only locally supported or system-wide in scale. This conceptual framework provides a tool for exploring the inherent light climate attributes of shallow estuarine ecosystems and helps determine susceptibility to the harmful effects of nutrient enrichment.

Morphology-based classification of functional groups for potamoplankton

“…First, MBFG V mixed species of Groups RV and RIIb by ignoring the absence and presence of exoskeletal structures, whereas this morphological difference might lead to observable discrepancies in terms of tolerance to suspended sediment in rivers. Potamoplankton showed sensitivity to inorganic (non-algal) turbidity, which is a function of SSC (May et al, 2003). Group RV was possibly vulnerable to high SSC because it lacked hard armour (e.g., dinoflagellates) (Lau et al, (Fig.…”

A Multi-Sensor Approach to Examining the Distribution of Total Suspended Matter (TSM) in the Albemarle-Pamlico Estuarine System, NC, USA

“…A major effect that TSM has on water quality is its influence on the underwater light field. Through absorption and scattering, TSM can alter the spectral nature and reduce light intensity to a level that significantly limits phytoplankton production within the water column [1][2][3][4][5][6] and primary production of submerged vegetation on the seabed [7][8][9]. Coral reefs are negatively impacted by the deposition of TSM [10,11].…”

Interannual variability of alongshore spring bloom dynamics in a coastal sea caused by the differential influence of hydrodynamics and light climate

“…Later, the mean water column PAR also reached 400Wh × m −2 d −1 on days with high incident irradiance corroborating Iriarte and Purdie (2004) who observed strong phytoplankton growth above this level of mean water column PAR. Turbidity in coastal seas can, in general, be related to winds, tides, and suspended particulate matter input from rivers (Iriarte and Purdie, 2004;May et al, 2003;Cloern, 1996), but it may also be raised by planktonic organisms in the water column (Tilzer, 1983). It is beyond the scope of this study to explicitly assess the role of different factors in leading to the rapid decrease of turbidity.…”