Multifractal
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Ecological Modeling
I have used a variety of modeling frameworks over a range of scales to investigate ecological relationships of estuarine and marine systems.
IBM Modeling:
Individual-based model of the feeding behavior of predators foraging in
a complex food environment.
- Currie WJS and KMD Cuddington. The Importance of Patchy Distributions for Predator Foraging Success: Zooplankton in a Multifractal Field.
Nutrient Loading to Estuaries:
CLUE: is a generalized model of nutrient loading into New England coastal
embayments as determined by land-use. CLUE is a process-based, empirical
model in which the relationships among its important variables are derived
from independent observations. It represents the best synthesis of how
the various components of land use, nitrogen loading, and ecosystem response
fit together. The nitrogen loading model was developed and tested originally
in Waquoit Bay on Cape Cod, but has successfully estimated nitrogen inputs
into estuaries, as determined by field measurements and other supporting
data. This provides an estimate of the amount of nitrogen entering the
receiving waters either as a mass loading value or a concentration. Estuary
size and the tidally induced flushing rate determine the amount of nitrogen
available for biological uptake in the estuary.
The ecosystem response model takes output from the nitrogen loading model and estimates the levels of four key indicators of estuarine habitat quality in response to the nitrogen loading: algal blooms, eelgrass, susceptibility to low dissolved oxygen conditions, and fish populations. Water column chlorophyll concentration is calculated based on relationships of algal productivity to nitrogen availability, light, temperature, mixing, and grazing by herbivores. The model estimates susceptibility to anoxia by calculating the number of days that oxygen demand is likely to exceed supply, based on average light incidence, temperature, and modeled system respiration. For a given embayment, the ecosystem response model estimates the areal extent and density of eelgrass under pristine and eutrophic conditions, using such factors as light availability, temperature, and water depth. Finally, the model estimates finfish abundance and diversity as a function of eelgrass density.
- Currie WJS and JN Kremer. The CLUE model: A generalized model for the investigation and management of shallow estuarine eutrophication
EcoHAB:
Harmful Algal Blooms (HABs) of the dinoflagellate Karenia brevis
Davis (formerly Gymnodinium breve) routinely affect the Gulf coast
of Florida and account for a significant portion of the yearly production
of the region. HABs of Karenia brevis have resulted in closures
of shellfishing due to Neurotoxic Shellfish Poisoning (NSP), and fish
and marine mammal kills. The vital tourist industry requires immediate
cleanup of beaches fouled by significant fish kills reaching 100 kg /
meter of coastline and costing millions of dollars.
Extremely clear water, low nutrients, and a resultant low phytoplankton biomass typify waters of this region. Though tropical oligotrophic waters are not typical environments for dense growths of algae, episodic blooms have been documented back to the 1700's. This is in part due to the specifics of K. brevis physiology, which grows at extremely low light levels, has high nutrient uptake rates, and utilizes both inorganic and organic nitrogen. These dinoflagellates are active swimmers (1 m hr-1) capable of vertical migration, with known positively phototrophic, weakly negatively geostrophic behavior. While significant progress has been made documenting the toxin production and growth physiology of K. brevis, these are almost exclusively laboratory-based studies. Little research has yet been done using field-based measurements of Florida HAB initiation, growth and dissipation. A variety of triggers have been suggested to account for the bloom initiation including Saharan dust events, growth of nitrogen-fixing cyanobacteria, and upwelling on the continental shelf. We use a straightforward modeling approach with very little site specificity, a simple imbedded biological model parameterized with Karenia brevis physiology capable of simulating the gross features of both the initiation and spread of a bloom off Florida. This ecological model is coupled to ROMS, the Regional Ocean Modeling System, a sophisticated, open-source physical oceanographic model ideally suited for the simulation of upwelling systems to investigate the possibility of wind-induced upwelling as the initiator of HABs off Florida.
- Currie WJS, Lewis CV, Powell TM. Upwelling events initiate harmful algal blooms of Karenia brevis on the West Florida Shelf - a modeling study.
Relevant Publications:
- Howard C. Berg. 1983. Random walks in biology. Princeton Univ. Press, 142p.
- D. L. DeAngelis. 1992. Dynamics of Nutrient Cycling and Food Webs. Kluwer Academic Publishers, 288 p
- DeAngelis DL, Gross GL (1992) Individual-based models and approaches in ecology: Populations, communities and ecosystems. Chapman and Hall, Inc, New York
- L. Edelstein-Keshet. 1988. Mathematical Models in Biology. McGraw-Hill, 608p
- Nicholas J. Gotelli. 2001. A primer of ecology. Sinauer, 206 p., 3nd Ed.,
- William S. C. Gurney and Roger M. Nisbet. Ecological Dynamics. Oxford Univ. Press, 352p
- Hassell MP (1978) The dynamics of arthropod predator-prey systems. Princeton University Press, Princeton
- Kareiva, P. 1990. Population dynamics in spatially complex environments: theory and data. Phil. Trans. R. Soc. Lond. B 330:175-190.
- Sharon E. Kingsland. Modeling Nature. 1995. The Univ. of Chicago Press, 2nd Ed
- Roger M. Nisbet and William S. C. Gurney. 1982. Modelling Fluctuating Populations. Wiley, 379p
- David C. Schneider. 2003. Quantitative Ecology: Spatial and Temporal Scaling. Academic Press, 395p
- Peter Yodzis. 1998. Introduction to theoretical ecology. New York (etc.): Harper & Row, 384 p