PHYTOPLANKTON TRAIT TRADEOFFS INFLUENCE PRODUCTIVITY AND ASSEMBLAGE COMPOSITION IN A SPECIES-RICH BAY MODEL

Historically, ecosystem and earth-system models have focused on 1-3 phytoplankton groups, and therefore left assemblage structure unresolved. Considering processes that support ecosystem functioning (e.g. biomass production, maintenance of water quality), differentiating between bulk phytoplankton biomass and species (or functional group) specific biomass is important, as phytoplankton taxa respond differently to environmental fluctuations and potential changes in composition may not reflect changes in bulk biomass. In cases where the traits of an altered assemblage are less desirable, as in the case with harmful algae blooms, such distinctions become critical. In the work presented here, we discuss further development of the spatially-explicit, multispecies, multi-nutrient plankton model for shallow bay systems (MUMPS), focused on incorporation of a self-organized, species-rich phytoplankton assemblage shaped by life history traits and ecological trade-offs. Here, tradeoffs include reduced maximum growth rate for low half-saturation growth coefficients and reduced edibility to a dynamic zooplankton population. Preliminary results show that shifts in phytoplankton assemblage composition to dominance by slower growing species were largely dependent on extended periods of nutrient limitation that occurred during prolonged low inflow conditions. In simulations still to come, we anticipate altered freshwater inflows and nutrient loading conditions to reveal nuanced interactions between bottom-up and top-down (grazer-driven) controls on productivity and community composition.

Presentation Preference: Oral

Primary Presenter: Sierra Cagle, Texas A&M University at Galveston (scagle1414@gmail.com)

Authors:

Daniel Roelke, Texas A&M University  (droelke@tamu.edu)

Joydeb Bhattacharyya, Karimpur Pannadevi College  (b.joydeb@gmail.com)