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Monday, May 26, 2008 - 1:45 PM
88
An empirical and modeling analysis of the spatial structure and trophic energy flow through a small temperate stream
Jerry V. Mead1, Michael J. Connerton2, Charles A.S. Hall3, and Neil H. Ringler3. (1) Patrick Center for Environmental Research, The Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103-1101, (2) Cape Vincent Fisheries Station, New York Department of Environmental Conservation, 541 East Broadway, Cape Vincent, NY 13618, (3) Environmental and Forest Biology, SUNY ESF, 1 Forestry Drive, Syracuse, NY 13210
I studied the importance of spatial attributes to the structure and function of a small stream ecosystem in Northern New York. This study has three main objectives: (1) to simulate and compare production of periphyton along a gradient of riparian forest cover, (2) to refine aquatic invertebrate bioenergetics models via synthesis of literature values, (3) to construct and validate a spatial model of energy flow through the benthos of the stream food web. Each objective builds upon one another beginning with models of the physical environment and periphyton, followed by inclusion of aquatic invertebrates. To achieve the first objective, I simulated periphyton production over a 2-dimensional space using existing periphyton and hydraulic models. I then validated predictions of periphyton production against field estimates of gross primary production (GPP). Simulations of periphyton production explained 75% of the variation in measured GPP. Stream wetted area per unit reach length increased with riparian forest cover up to 70% cover and then declined. Due to increased area per unit length, total algal production (gross and net) increased with forest cover on the bank reaching a maximum at 70% forest cover after which it declined. For the second objective, I compared bioenergetic parameters among taxa grouped by different methods of locomotion and feeding to create a general energetic algorithm for application in a trophic model. I used body size and water temperature as covariates for comparisons of categories of invertebrates (ex. filterers vs non-filterers). The model explained 94.6% of the variance in observed standard metabolic rates using body weight, water temperature, and feeding category. To predict invertebrate production (Objective 3), I combined models from objectives 1 and 2 with a model that populates invertebrates over space. I then compared simulated production of lotic invertebrates to measured production along a riparian forest-cover gradient. Simulations of invertebrate production explained 68% percent of the variation in measured growth. Invertebrate biomass per unit stream length was greatest at 60-80% riparian forest cover;` invertebrate production peaked at 20-40% forest cover.
Web Page: hydraulics, spatial, riparian