8
Impact of Dynamic Light
and Nutrient Environments
on Phytoplankton Communities
in the Coastal Ocean
Mark A. Moline, Oscar Schofield and Joe Grzymski
When we try to pick out anything by itself, we find it hitched to everythingelse in the Universe.
John Muir (1838-1914)
In this chapter you will be able to explore:
• Responses of phytoplankton growth to light fields and nutrient concentrations;
• Effects of eutrophication on the structure of phytoplankton communities.
8.1. Introduction
Phytoplankton represent the base of the food web in marine ecosystems.
Changes in the structure and composition of these phytoplankton communities will, therefore, have a direct effect on the amount of carbon available to
higher trophic levels. In the absence of significant grazing, light and nutrients are the primary factors regulating phytoplankton photosynthesis and
productivity in marine environments. As the requirements for light and nutrients differ between species, phytoplankton community structure is also
sensitive to dynamic optical and chemical conditions in the water column .
Nutrient loading in coastal regions from agricultural runoff and urbanization has been documented on a global scale. Nitrogen (N) and phosphorous
(P) inputs into coastal seas have increased four-fold, leading to considerable
eutrophication (Martin et al. 1981; Nixon 1995). These nutrient additions
result in significant shifts in the ratios of macronutrients in the coastal margins. Shifts in nutrient ratios can alter phytoplankton community structure,
changing the timing and abundance of dominant phytoplankton species in
coastal areas (Sommer 1989; Admiraal et al. 1990; Smayda 1990; Officer and
Ryther 1980; Conley et al. 1993; Turner and Rabalais 1994). Increases in N
and P concentrations relative to silicate (SO concentrations have been shown
to favor the dominance of non-siliceous phytoplankton over siliceous di144
M. Ruth et al. (Eds.), Dynamic Modeling for Marine Conservation
© Springer-Verlag New York, Inc. 2002
Impact of Dynamic Light
and Nutrient Environments
on Phytoplankton Communities
in the Coastal Ocean
Mark A. Moline, Oscar Schofield and Joe Grzymski
When we try to pick out anything by itself, we find it hitched to everythingelse in the Universe.
John Muir (1838-1914)
In this chapter you will be able to explore:
• Responses of phytoplankton growth to light fields and nutrient concentrations;
• Effects of eutrophication on the structure of phytoplankton communities.
8.1. Introduction
Phytoplankton represent the base of the food web in marine ecosystems.
Changes in the structure and composition of these phytoplankton communities will, therefore, have a direct effect on the amount of carbon available to
higher trophic levels. In the absence of significant grazing, light and nutrients are the primary factors regulating phytoplankton photosynthesis and
productivity in marine environments. As the requirements for light and nutrients differ between species, phytoplankton community structure is also
sensitive to dynamic optical and chemical conditions in the water column .
Nutrient loading in coastal regions from agricultural runoff and urbanization has been documented on a global scale. Nitrogen (N) and phosphorous
(P) inputs into coastal seas have increased four-fold, leading to considerable
eutrophication (Martin et al. 1981; Nixon 1995). These nutrient additions
result in significant shifts in the ratios of macronutrients in the coastal margins. Shifts in nutrient ratios can alter phytoplankton community structure,
changing the timing and abundance of dominant phytoplankton species in
coastal areas (Sommer 1989; Admiraal et al. 1990; Smayda 1990; Officer and
Ryther 1980; Conley et al. 1993; Turner and Rabalais 1994). Increases in N
and P concentrations relative to silicate (SO concentrations have been shown
to favor the dominance of non-siliceous phytoplankton over siliceous di144
M. Ruth et al. (Eds.), Dynamic Modeling for Marine Conservation
© Springer-Verlag New York, Inc. 2002