Combined effects of water temperature and nutrients concentration on periphyton respiration – implications of global change

Abstract

With the increase in global mean surface temperature predicted for the near future, stream water temperature will also increase. Simultaneously, water quality is likely to decrease (e.g., due to increases in nutrient and pollutant concentrations). The objective of this study was to evaluate the individual and combined effects of increases in water temperature and nutrients concentration on periphyton respiration, as a surrogate for stream metabolism. Stones naturally colonized with periphyton in an unpolluted mountain stream in Central Portugal were sampled seasonally over a year, and incubated in the laboratory under two water temperatures (ambient and 4°C elevated) and two nutrients concentration levels (ambient and ∼6× higher inorganic dissolved nitrogen, ∼2× higher soluble reactive phosphorous concentrations). Overall, increases in water temperature stimulated periphyton respiration to a larger extent than did increases in nutrients concentration. In spring, the simultaneous increase in water temperature and nutrients concentration stimulated periphyton respiration beyond expected from the individual effect of each factor. These results indicate that synergistic interactions between factors might occur under certain environmental conditions, suggesting that care should be taken when predicting the combined effect of changes in multiple factors from their individual effects. The observed stimulation of periphyton respiration promoted by increased temperature and nutrients concentration can lead to changes in streams carbon budgets, with a positive feedback for global warming, as more CO2 might be released to the atmosphere.

Do changes in riparian zones affect periphyton growth and invertebrate colonization on rocky substrates in Atlantic Forest streams?

“…Temperature is a key factor in the development of algal biomass because it regulates cellular metabolism, tending to optimize growth rates (Bowes et al, 2007). Normally, nitrogen and phosphorus act as limiting nutrients for algae and periphyton growth in stream ecosystems (Murdock et al, 2011;Rosa et al, 2013). In streams located near agricultural areas, the periphyton production can be increased by input of fertilizers leached from surrounding areas (Conley et al, 2009).…”

“…The extract retained in the trays was stored in covered centrifuge tubes (50 ml) under refrigeration and taken to the laboratory. After the periphyton was removed, the active surface area of each cobble, i.e., the area excluding the lower surface, was determined following Rosa et al (2013) Sample processing. The chlorophyll-a content was used as an indicator of the growth of periphytic algae on each incubated cobble.…”

“…The presence of these primary producers alters the structure of the aquatic environment; the algae remove nutrients from the water column, minimize the effects of water flow on exposed substrates, and contribute to sediment stabilization (Larned, 2010). The biomass of periphytic algae may be influenced by several abiotic factors including temperature, luminosity, substrate type, water flow and nutrient content (Fanta et al, 2010;Rosa et al, 2013). Some biotic factors may negatively affect periphyton biomass, such as herbivory and bioturbation caused by aquatic organisms (Wellnitz & Poff, 2012).…”

Influence of light and temperature on the development and denitrification potential of periphytic biofilms

“…Previously, it was found that increasing overlying water velocity promoted establishment of a more physiologically active consortium of bacterial denitrifiers in periphyton (Arnon et al, 2007). Stimulation of periphyton respiration was observed by increased temperature and nutrient concentrations (Rosa et al, 2013).…”