Flow extremes and benthic organic matter shape the metabolism of a headwater mediterreanan stream.

ACUNA, V.; ADONIS GIORGI; MUÑOZ, I.; UEHLINGER, U.; SABATER, S.

FRESHWATER BIOLOGY (PRINT)

Blackwell Publishing

Lugar: Londres; Año: 2004 vol. 49 p. 960 - 971

0046-5070

Single-station diel oxygen curves were used to monitor the oxygen metabolism of Fuirosos Stream, an intermittent forested third-order stream in the Mediterranean area, over a period of one year and a half. Ecosystem Respiration and Gross Primary Production were estimated, while the organic matter inputs and PAR were measured to determine the effect of the riparian forest on stream metabolism. Annual Ecosystem Respiration was 1690 g O2 m-2 y-1, while the Annual Gross Primary Production was 275 g O2 m-2 y-1. Due to these values, the Annual Net Ecosystem Production was –1415 g O2 m-2 y-1. During the studied period Fuirosos was a heterotrophic stream, with P:R ratios that averaged 0.16. Rates of Ecosystem Respiration (ER) were unusually high compared to other rivers, ranging from 0.4 to 32 gO2 m-2 d-1. ER was highest in fall 2001, when the amount of benthic organic matter was highest. The Mediterranean climate, and in its effect the hydrological regime, was mainly responsible of the temporal variation in BPOM, and consequently of ER. Gross Primary Production (GPP) rates were relatively low, ranging from 0.05 to 1.9 gO2 m-2 d-1. The maximum values of GPP were during few weeks in Spring until the riparian canopy was closed. The phenology of riparian vegetation was an important determinant of light availability, and consequently, of GPP. In a daily scale, light and temperature were the most important factors governing the shape of P-I curves. Three patterns could be distinguished in the P-I relationships: hysteresis in late autumn and winter, light saturation (that appears over 100mmol photon m-2 s-1) and linear the rest of the studied period.