NPZVISUALIZER 1.5 · Neil Banas, Univ of Washington Applied Physics Lab · Oct 2008

This is a tool for exploring the dynamics of coastal marine ecosystems, developed as part of the NSF RISE project. Scroll down for a description of the model cases shown. Email Neil at for more info.

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About the models

All of these models represent the cycling of nitrogen through plankton populations: we track nitrogen because it is the limiting factor controlling phytoplankton growth (along with light) along the Pacific Northwest coast, as in many places. Circles represent stocks of nitrogen, either dissolved, inside living cells, or in the form of "detritus" (which here really just means "other.") Arrows represent fluxes between these stocks, like growth, predation, decay, and so forth. The slider at the top lets you control the speed of the simulation; the sliders on the right let you explore the effect of some of the adjustable parameters in each model case.

· The simple case is a version of the classic three-box "NPZ" (nutrient, phytoplankton, zooplankton) model: see Franks et al. 1986 or Franks 2002.

· The size spectrum and smooth size spectrum cases are versions of a general allometric model I wrote (and am still exploring). Instead of one pool of phytoplankton (P) and one of zooplankton (Z), these models subdivide P and Z according to organism size and then assign vital rates (nutrient uptake rate, predation rate, mortality) and other parameters using general scaling relationships from (other people's) lab studies. This is a way to incorporate some, though not all, planktonic diversity while keeping the number of free parameters (a.k.a. tuning knobs (a.k.a. fudge factors)) under control. See the slides from my 2007 Gordon Conference seminar for some context.

(side note: some of my students in this course noticed in the six-size-class version ("size spectrum") that if you turn "Z preference for Z" down to 0 (so that zooplankton only eat phytoplankton, not each other) and then gradually increase it, you can get a beautiful period-doubling route to chaos. Go humanities majors!)

· Cross-shelf conveyor adds a conveyor-belt-like upwelling circulation to the six-size-class allometric model.

Finally, "NPZD, Banas et al 09" lets you explore the four-box ecosystem model used in this study of the Columbia River plume region. What's shown here is a 0-d (one-box, or chemostat) version of the model; in the paper linked to above, we couped it to a high-resolution, realistic circulation model for the Washington and Oregon coast. Note that the "N injection/removal" and "D sinking" sliders can be used to adjust the total nitrogen in the box or create a steady-state flowthough (N in, D out).


Built with Processing

Some but not all of the source code: statemachine15 dynamical_system gui model_list models_active models_other

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