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Research Spending & Results

Award Detail

Awardee:OREGON STATE UNIVERSITY
Doing Business As Name:Oregon State University
PD/PI:
  • James J Ruzicka
  • (541) 737-4933
  • jim.ruzicka@oregonstate.edu
Award Date:02/19/2013
Estimated Total Award Amount: $ 182,687
Funds Obligated to Date: $ 182,687
  • FY 2013=$182,687
Start Date:03/01/2013
End Date:02/28/2017
Transaction Type:Grant
Agency:NSF
Awarding Agency Code:4900
Funding Agency Code:4900
CFDA Number:47.050
Primary Program Source:040100 NSF RESEARCH & RELATED ACTIVIT
Award Title or Description:Collaborative Research: Analysis of Continental Shelf Ecosystems: Food Web Structure and Functional Relations
Federal Award ID Number:1259057
DUNS ID:053599908
Parent DUNS ID:053599908
Program:BIOLOGICAL OCEANOGRAPHY
Program Officer:
  • Michael Sieracki
  • (703) 292-7585
  • msierack@nsf.gov

Awardee Location

Street:OREGON STATE UNIVERSITY
City:Corvallis
State:OR
ZIP:97331-8507
County:Corvallis
Country:US
Awardee Cong. District:04

Primary Place of Performance

Organization Name:Oregon State University
Street:
City:Corvallis
State:OR
ZIP:97331-8507
County:Corvallis
Country:US
Cong. District:04

Abstract at Time of Award

Marine ecosystems are characterized by complex interactions among biological components and within the physical setting. The complexity of these systems makes them difficult to understand or interpret based on either observations or models, both of which suffer from incomplete knowledge of the natural system. Of interest to many scientific questions and to management is the utility of broad, simplifying concepts about how such systems operate and how they change over time. Among these concepts are bottom-up control (the idea that nutrient sources and lower trophic levels govern the ecosystem), top-down control (the idea that organisms at the highest trophic levels govern), and regime shifts (major restructuring of the system due to natural or anthropogenic, or combined, forcing). A basic tenet of biological oceanography is the coupling between physical processes and population dynamics. The study of these connections has been based on certain simplifications, particularly the emphasis on one, or very few, trophic components. The parallel development of trophic network models (e.g., ECOPATH) represents an effort to study the relationships between a more complete spectrum of trophic groups from an energy transfer and predator-prey perspective. Yet, ecosystem structure, function, and behavior depend on the physical context: mixing, advection, water residence time, and seasonality, especially for shelf ecosystems. These terms define production, recycling, and export rates and set the scope of benthic-pelagic coupling, but they are rarely incorporated into trophic network models. There is clear need to develop portable methods of analysis that can illuminate physical-biological interactions across a wide range of ecosystems and demonstrate their effects on system productivity and resilience at all trophic levels. However, there is a simultaneous risk of such models becoming so complex that untangling the mechanisms and artifacts of model dynamics quickly becomes intractable. A portable, coupled bio-physical model framework of intermediate trophic and physical resolution is a potential solution that will be developed in this project. The goal is to produce models simple enough to understand, but complex enough to be realistic. Thus, about 5 physical boxes and about 20 ecological compartments are expected to be included. The models will be developed for four contrasting, data-rich continental shelf ecosystems. This project will use the range of food webs and physical forcing characteristic of these four systems to do the following. 1. Assess the merits and disadvantages of studying community dynamics in terms of aggregated functional groups as the appropriate level of trophic resolution. 2. Compare the relative roles of physical processes and trophic network structure in determining system productivity, variability, and resilience across all trophic levels, including both pelagic and benthic food webs. 3. Test the applicability of broad concepts of ecosystem behavior such as bottom-up vs. top-down control of community dynamics, or of sudden regime shifts. The project will contribute to the education of future scientists through participation in active research. The public will be informed about ocean ecosystem issues through development of a museum exhibit. Model code will be provided to the community for further use and development. Collaboration with NOAA scientists will foster application of project results to practical management issues.

Publications Produced as a Result of this Research

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Ruzicka, J.J., Steele, J.H., Gaichas, S.K., Ballerini, T., Gifford, D., Brodeur, R., Hofmann, E.E. "Analysis of Energy Flow in U.S. GLOBEC Ecosystems from End-to-End" Oceanography, v.26, 2014, p.24.

Ruzicka, J.J., Steele, J.H., Gaichas, S.K., Ballerini, T., Gifford, D., Brodeur, R.D., Hofmann, E.E. "Analysis of energy flow in US GLOBEC ecosystems using end-to-end models" Oceanography, v.26, 2013, p.24.

Treasure, A.M., Ruzicka, J.J., Gurney, L., Moloney, C., Ansorge, I. "Land-sea interactions and consequences for sub-Antarctic marine food webs" Ecosystems, v.18, 2015, p..

Treasure, A., Ruzicka, J., Moloney, C., Gurney, L., Ansorge, I. "Land-sea interactions and consequences for sub-Antarctic marine food webs" Ecosystems, v.18, 2015, p.752.

Ruzicka, J.J., Brink, K.H., Gifford, D.J., Bahr, F. "An intermediate complexity, physically coupled end-to-end model platform for coastal ecosystems: simulating the effects of changing upwelling conditions on the Northern California Current ecosystem." Ecological Modelling, v.331, 2016, p.86.

Ruzicka, J.J., Steele, J.H., Gaichas, S.K., Ballerini, T., Gifford, D., Brodeur, R.D., Hofmann, E.E. "Analysis of energy flow in US GLOBEC ecosystems using end-to-end models" Oceanography, v.26, 2013, p.24.


Project Outcomes Report

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

Objectives and Intellectual Merit:

A major feature distinguishing shelf ecosystems is the physical context that defines rates of nutrient import, nutrient recycling, and plankton exchange between coastal and oceanic waters. When comparing dynamics of marine ecosystems involving multiple species, researchers have focused upon studying differences in food web structures. Food web models integrate our knowledge of community composition, ecosystem productivity, and species interactions. This allows investigation of temporal variability among species that are primarily driven through predator-prey interactions and fishing pressure. However, to understand ecosystem dynamics and resilience to natural and anthropogenic perturbations, researchers must also consider the physical context of the ecosystem. The two major goals of this project were: 1) to develop a common, intermediate complexity physical/biological model platform that may be applied to study diverse ecosystems, and 2) to understand how food web structure and physical context each control the dynamics of coastal ecosystems.

 

Approach:

Our first major activity was the development of a standardized multi-species ecosystem model platform, ECOTRAN, that could be applied to diverse shelf ecosystems. It considers multiple trophic levels, includes nutrient and detritus cycling pathways, and is built upon a 2-dimensional 5-box geometry to incorporate physical advection and mixing across the shelf. We considered four food web models within four physical settings representing diverse coastal ecosystems: the Northern California Current upwelling ecosystem, the Coastal Gulf of Alaska downwelling ecosystem, Georges Bank shallow bank ecosystem, and the North Sea semi-enclosed basin ecosystem. Our second major activity was to apply the models to investigate the role of food web structure and the role of physical context in determining ecosystem dynamics. We examined response times of coupled physical - food web models following perturbations to nutrient input rates, and we ran different food web models within each of the four physical settings. ECOTRAN was also applied to the Northern California Current upwelling ecosystem to examine the effects of changes to upwelling characteristics expected to occur into the future as a result of global warming.

 

Results and Impact:

ECOTRAN simulations provide information about ecosystem resilience and response to environmental change and resource management strategies, and these are of further value to economic and social sciences. Response times of different species following changes to plankton production are related to the time required for the plankton production rate to balance physical transport rates, the rate of detritus recycling back into the food web, and growth rates of higher trophic level consumers. Detritus recycling plays a major role in system dynamics since it affects both “bottom-up” fluxes through the food web and “top-down” pressures by predators. When detritus recycling is low, as in an upwelling system, response times are short and less sensitive to differences in physical transport rates. But when detritus recycling is high, as in a semi-enclosed basin, more production is recycled through longer-lived, higher trophic level consumers whose slow growth impose long response times.

Comparative analyses of different food webs within different physical settings tested the hypothesis that when nutrient supply and physical transport rates are standardized, there are no substantial differences in the dynamics within diverse food webs. With few specific exceptions, physical context played the greater role controlling dynamics. Exchange between shelf and ocean affected not only nutrient recycling but also trophic transfer efficiencies and the importance of pelagic vs. benthic components of the food web. Differences in plankton transport rates leads to apparent decoupling of lower trophic and upper trophic level production - reducing upper trophic production relative to plankton production (upwelling) or enhancing upper trophic level and benthos production (downwelling). Food web structure further affects dynamics within different physical contexts. Food webs with high intrinsic detritus production have especially productive benthos where physical conditions provide plankton subsidies.

Application of ECOTRAN to the Northern California Current allowed us to look at response to changes in upwelling. Dome-shaped relationships exist between upwelling strength and productivity across all trophic levels. Phytoplankton production is a balance between nutrient supply and physical export off the shelf. Productivity increases as phytoplankton take advantage of increasing nutrient rate, but as plankton export begins to exceed the ability of the phytoplankton community to utilize the increased nutrient supply, production declines with increasing upwelling intensity. Other researchers have proposed that global warming will lead to steeper temperature gradients between the ocean and the land, leading to greater alongshore wind-stress and increased upwelling intensity. ECOTRAN simulations suggest that as upwelling intensifies, we should expect to see increasing ecosystem productivity in the future. However, the broad distribution of upwelling event intensities over the past 50 years suggests that during the strongest events, the Northern California Current already realizes the negative effects of high rates of plankton export to the ocean. As the proportion of strong upwelling events increases beyond current conditions, the historically observed correlations between upwelling and overall ecosystem productivity may break down.


Last Modified: 05/22/2017
Modified by: James J Ruzicka

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