Cole, J. J. Institute of Ecosystem Studies, colej@ecostudies.org
Caraco, N. F. Institute of Ecosystem Studies, caracon@ecotudies.org
del Giorgio, P. A. Horn Point Environmental Laboratory, delgior@hpl.umces.edu
Pace, M. L. Institute of Ecosystem Studies, pacem@ecostudies.org

 
DOM SUBSIDIZES HETEROTROPHY IN AQAUTIC ECOSYSTEMS: MULTIPLE LINES OF EVIDENCE FROM FRESH- AND SALT WATERS.
 
While limnologists and oceanographers have been aware for decades that dissolved organic matter (DOM) of external origin enters and effects aquatic ecosystems, trophic models generally do not explicitly consider these inputs. In the absence of external inputs of DOM, organic carbon flows from primary producers to consumers and bacteria. This view implies that autotrophic primary production (P) must exceed or equal the respiration (R) of all organisms (P/R greater than or equal to 1). Evidence from diverse fresh- and salt-water environments suggest that heterotrophic respiration exceeds primary production in most systems at most times (P/R less than 1). This evidence is robust, spans both geochemical and biological approaches and is consistent with ecosystem-scale carbon budgets. In this review we summarize the results of these diverse data sets and approaches and argue that most aquatic ecosystems receive and respire significant amounts of dissolved organic matter (DOM) originating outside of the system's boundaries. The evidence comes from both freshwater and marine systems and includes: inverted trophic biomass pyramids; comparisons of planktonic bacterial respiration to planktonic primary production; direct measurements P/R ratios in bottles; whole system measurements of P/R ratios; surface water gas saturation; and linked watershed-lake DOC models.
 
Day: Monday, Feb. 1
Time: 04:15 - 04:45pm
Location: Eldorado Hotel
 
Code: SS34MO0400E