Effects of macrograzers and light on periphyton stoichiometry

Abstract

A. 2004. Effects of macrograzers and light on periphyton stoichiometry. Á/ Oikos 106: 93 Á/104.Ecological stoichiometry describes the biochemical constraints of trophic interactions emerging from the different nutrient content and nutrient demand of producers and consumers, respectively. Most research on this topic originates from well-mixed pelagic food webs, whereas the idea has received far less attention in spatially structured habitats. Here, we test how light as well as grazing and nutrient regeneration by consumers affects growth and biomass of benthic primary producers. In the first laboratory experiment, we manipulated grazer presence (two different snail species plus ungrazed control), in the second experiment we factorially combined manipulation of grazer presence and light intensity. We monitored snail and periphyton biomass as well as dissolved and particulate nutrients (nitrogen and phosphorus) over time. Grazers significantly reduced algal biomass in both experiments. Grazers affected periphyton nutrient content depending on the prevailing nutrient limitation and their own body stoichiometry. In the nitrogen (N-) limited first experiment, grazers increased N both in the periphyton and in the water column. The effect was stronger for grazers with lower N-content. In the phosphorus (P-) limited second experiment, grazers increased the Pcontent of the periphyton, but the grazer with lower N-content had additionally positive effects on algal N. Light reduction did not affect periphyton biomass, but increased chlorophyll-, N-and P-content of the periphyton. These experiments revealed that the indirect effects of grazers on periphyton were bound by stoichiometric constraints of nutrient incorporation and excretion.

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

“…This difference in elementary composition (C, N, and P) might be related to the difference in microbial community structure (Makino et al, 2003). Previously, light and nutrient availability was found to be important factors affecting the elementary composition of periphytic biofilms developed in lakes and streams (Hillebrand et al, 2004;Qin et al, 2007). But no significant difference was observed for elementary composition and EPS of the biofilms in treatments with different PAR, which is probably due to the relatively high nutrient concentration used in this study.…”

Quantifying phosphorus and light effects in stream algae

“…Diatoms were identified to species level with the help of subsamples that were cleared with hot H 2 O 2 , mounted in Naphrax, and examined with a compound microscope at 10003. Cell volumes were calculated with standard geometric formulae (Hillebrand et al 1999), or with simple three-dimensional models, using dimensions measured on at least 10 individual cells for each major taxon. Biovolume density (mm 3 cm 22 ) for each taxon was computed by multiplying its areal density (No.…”

“…Phosphorus requirements have also been hypothesized to increase as a result of the demands of photoacclimation (Hessen et al 2002;Dickman et al 2006). Research on phytoplankton supports the negative relationship between light on algal nutrient content, but this relationship has been demonstrated inconsistently in benthic studies (Frost and Elser 2002;Hillebrand et al 2004;Hill and Fanta 2008). Large amounts of non-algal carbon in benthic algal communities may diminish the applicability of the light : nutrient hypothesis in streams (Frost et al 2005).…”

Independent effects of grazing and tide pool habitats on the early colonisation of an intertidal community on western Antarctic Peninsula

“…Periphyton is one of the main sources of food for benthic herbivores and in many cases is critical for the establishment of benthic macroalgae [23]. Grazing often has negative effects on the biomass accrual and productivity of this group [24]. In Antarctic coast, intertidal Nacella feeds on periphyton that is mainly comprised by microalgae and small filamentous algae [17].…”