Stream production and decomposition processes in contrasting environments in Argentina Virtual Conference on the 25th -30th July 2021

GIORGI, A.; VILCHES,C.; TAGLIAFERRO, M., ; TORREMORELL,A.; ALBARIÑO, R.

Dublin

Simposio; 12th Symposium for European Freshwater Sciences; 2021

Sociedad Europea de Ecología de Agua dulce

Stream production and decomposition processes in contrastingenvironments in ArgentinaDr Adonis Giorgi1, Dr Carolina Vilches1, Dr Marina Tagliaferro2, Dr Ana Torremorell1, Dr Ricardo Albariño31Instituto de Ecología y Desarrollo Sustentable (CONICET-UNLu), Departamento de Ciencias Básicas-UNLu-Av. Constitucióny Ruta Nac. N° 5, 2Centro Austral de Investigaciones Científicas -Consejo Nacional de Investigaciones Científicas y Técnicas(CADIC-CONICET). Bernardo Houssay 200, 3Instituto de Investigaciones en Biodiversidad y Medioambiente (CONICETUNComahue),Quintral 1250, 84001E_SS01 Role of freshwater ecosystems in the carbon cycle and the climate system, July 26, 2021, 10:30 - 12:00We estimated whole metabolism and leaf litter decomposition in two Argentina ecoregions, the Pampas andPatagonia. Pampean streams have mild weather, high irradiance, moderate temperatures, high nutrientconcentrations and low slopes. Patagonian streams have lower irradiance, temperature and nutrientconcentrations and higher slopes. Changes in dissolved oxygen were measured in twelve streams duringaustral spring at both ecoregions with the two station method along selected reaches. Using these values andthose of re-aeration, whole stream metabolism was estimated. Decomposition was estimated by the litterbag method, in twelve stream reaches with coarse and fine mesh sizes (20 and 0.5mm diameter, respectively)filled with 5 g of Populus nigra leaf litter. Bags were fastened to stream bottoms and retrieved at differentdates to estimate decay rates by a negative exponential model against cumulative degree days (dd-1) obtainedfrom water temperature series. Both production and decomposition differed by one order of magnitudebetween the two ecoregions. Estimated production was 1-8 g O2 m-2 d-1 in Pampean streams and 0.027-0.397g O2 m-2d-1 in Patagonia streams. Decay rates in Pampean were 0.00400 dd-1 and 0.00089 dd-1 in Patagonianstreams. Our findings suggest that Pampean streams function as autotrophic ecosystems while Patagonianstreams behave as heterotrophic, mostly ruled by regional contrasts determining different carbon sourcesand the capability to process them Such differences in stream functioning were diminished in high nutrientand less dense riparian plant canopy environments.