HR: 14:15h
AN: NB23D-04    [Abstracts]
TI: Stoichiometric Effects of Phosphorus Enrichment in the Kuparuk River Food web
AU: * Benstead, J P
EM: jbenstead@mbl.edu
AF: The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543 United States
AU: Deegan, L A
EM: ldeegan@mbl.edu
AF: The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543 United States
AU: Huryn, A D
EM: huryn@bama.ua.edu
AF: Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487 United States
AU: Peterson, B J
EM: peterson@mbl.edu
AF: The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543 United States
AB: A 3-km reach of the oligotrophic Kuparuk River (Alaska) has been fertilized with phosphorus (10 μg/L) for 22 consecutive Arctic summers. In 2004 we added a high-P (30 μg/L) reach to the experiment. As in previous years, phosphorus addition significantly increased chlorophyll a and decreased epilithon C:P ratio relative to the reference reach. Higher algal biomass or lower epilithon C:P in fertilized reaches caused faster growth of some primary consumers (e.g., Orthocladius rivulorum) but not others (e.g., Acentrella sp.), presumably because threshold C:P ratios varied among taxa. Young-of-year Arctic grayling (Thymallus arcticus) showed a significant step response to phosphorus addition. Some insect primary consumers are known to contain more phosphorus in fertilized reaches, because of storage or higher RNA content. Higher phosphorus content of insect prey may explain higher grayling growth rates in fertilized reaches, because production budgets suggest that carbon limitation of grayling growth is unlikely under natural prey densities, at which models of mass balance constraints indicate phosphorus limitation. Such an interaction would be evidence for increased growth of a nutrient-limited predator in response to modified carbon:nutrient ratios at two lower trophic levels - a fundamentally different effect of fertilization from that classically mediated by increased primary production.
DE: 1845 Limnology
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly