HR: 09:30h
AN: NB21D-05    [Abstracts]
TI: Nutrient Availability and Stream Biofilm Responses: Contrast Among Streams Draining Catchments With Different Land Uses
AU: * von Schiller, D
EM: schiller@ceab.csic.es
AF: Centre d'Estudis Avancats de Blanes (CSIC), Acces a la Cala St. Francesc, 14, Blanes, 17300 Spain
AU: Marti, E
EM: eugenia@ceab.csic.es
AF: Centre d'Estudis Avancats de Blanes (CSIC), Acces a la Cala St. Francesc, 14, Blanes, 17300 Spain
AU: Riera, J L
EM: jlriera@ub.edu
AF: Departament d'Ecologia, Univ. de Bracelona, Av. Diagonal, 645, Barcelona, 08028 Spain
AB: Nutrient limitation has been shown to be common in pristine streams due to low availability or unbalanced stoichiometry. Humans have altered both the quantity and the ratios among nutrients in freshwater ecosystems. This effect highly depends on the type of activity. Within this context, we asked a) how nutrient inputs from human activity affected the potential limitation of stream biofilms, and b) how biofilm responded in front of two N sources (ammonium and nitrate). We conducted nutrient diffusing substrata experiments (6 treatments: control, nitrate, ammonium, phosphate, nitrate+phosphate, and ammonium+phosphate) in 3 streams located in the same catchment but subjected to distinct human pressures (pristine, agricultural, and urban) resulting in a gradient of N availability. On the last week of each experiment we performed a 12h 15NO3 addition. Chlorophyll a showed high variability within and between treatments and among streams, but was generally highest in the agricultural stream. N limitation was only observed in the pristine stream. Nitrate and ammonium treatments exerted no differential effect as potential limiting nutrient sources. All treatments were 15N labeled, but biofilm in control and phosphate treatments tended to show higher 15N values. These results suggest that nutrient availability affects both biofilm accrual and uptake capacity
UR: http://www.ceab.csic.es
DE: 0400 Biogeosciences
DE: 1030 Geochemical cycles (0330)
DE: 1803 Anthropogenic effects
DE: 1845 Limnology
DE: 4805 Biogeochemical cycles (1615)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly