Environmental control of seasonal and inter-annual variations of periphytic biomass in a North Iberian stream

Abstract

). Sampling sites showed large differences in cover, conductivity and nutrient contents, as well as some inter-annual differences, resulting from changes in discharge and in human activities. Most environmental variables showed low seasonality, main variations being produced by floods. Solar radiation changed little during 2001 -2002, because of the coincidence of a sunny winter followed by a cloudy summer, and seasonal differences in riparian cover resulted in more sunlight reaching the streambed of closed sites during winter, and small differences at the open ones. The growth and abscission of riparian leaves results in a strong light regime at the closed sites, with more sunlight during winter, but this pattern changes from year to year, depending on the weather. Spatial differences and highest values of periphytic biomass were much lower than those measured in 1990 -91, because of contrasting weather patterns. Variables controlling periphytic biomass in the Agüera change from reach to reach. At open sites flow is the main temporal controller, whereas at closed sites the effects of light availability prevail, thus giving more similar seasonal patterns from year to year. Nutrients seem to play a minor role in temporal variations.

Impacts of Eucalyptus globulus Plantations on Physiology and Population Densities of Invertebrates Inhabiting Iberian Atlantic Streams

“…In a previous study on the main channel of the Agüera River, a relationship was observ ed between growth of periphyton and the SRP content of the water (SRP range: 11.3-85.1 μg P l -1 ) (IZAGIRRE and ELOSEGI, 2005). Although the SRP concentration in the streams studied is low (3.4-9.7 μg P l -1 ), it still allows primary production (SABATER et al, 2008), and we suggest that the enhancement of primary production by an increment of SRP may be responsible for the physiological changes observed in H. confusa.…”

“…Nevertheless, no relationship arose between shading and the invertebrate variables we measured (data not shown). Moreover, the differences in the shading at the zenith between site types were surely lower in the previous months, when the deciduous species of the reference sites did not have leaves (see IZAGIRRE and ELOSEGI, 2005) and hence the differences were likely to be less pronounced.…”

Effects of wastewater treatment plant pollution on in-stream ecosystems functions in an agricultural watershed

“…The respiration rate was also largely controlled by water exchange with the hyporheic zones (Wang et al, 2003), and it may be interesting to take this geomorphological parameter into account to explain the results obtained. Nutrient (P and N) seems to play a minor role in inter-site variations of epilithic biofilm biomass as shown by Izagirre and Elosegui (2005) in a stream of North Spain.…”

Macroinvertebrate community dynamics in a temperate European Atlantic river. Do they conform to general ecological theory?

“…This pattern has also been found in other European temperate Atlantic rivers (Basaguren et al, 1996). Moreover, spatial and temporal variability of food resources have also been shown to produce significant changes in macroinvertebrate FFG in these rivers, due to the increases in leafy debris and algal productivity in autumn-winter and summer-autumn, respectively (Graca, 2001;Izaguirre & Elosegui, 2005;Pardo & Alvarez, 2006).…”