Atmosphere Ocean Science Friday Seminar

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Competing mechanisms for the generation of intrinsic variability in an NPZ model

Speaker: Ben Mayersohn, PhD Candidate

Location: Warren Weaver Hall 512

Date: Friday, April 19, 2019, 3:45 p.m.

Synopsis:

Phytoplankton communities are highly diverse, and their rich community structure allows them to play a role in several important oceanic processes: large species such as diatoms have high sinking rates and lead to increased carbon sequestering, and small cyanobacteria such as prochlorococcus are responsible for the majority of oceanic photosynthetic activity. Thus, it is important to understand the dynamics that lead to changes in community structure and total biomass. While much of the observed variability in these communities may be physically driven, ecosystems often exhibit complicated intrinsic variability. Here we develop a zero-dimensional intermediate-complexity ecosystem model with three nutrients, six phytoplankton, and two zooplankton to explore two kinds of intrinsic variability:  R-oscillations, which correspond to patterns of species succession; and Z-oscillations, which are driven by predator- prey interactions. While Z-oscillations always occur on relatively short timescales, we find that increasing the strength of zooplankton leads to longer species succession times. We suspect that in the presence of faster physical processes, the R-oscillation mechanism may collapse. More work must be done to investigate this further.