Community development alters photosynthesis‐irradiance relations in stream periphyton

Abstract

The effects of biomass accumulation and community age on the photosynthesis-irradiance response of periphyton were examined in developmental sequences from three stream locations that differed in canopy cover. Photosynthesis-irradiance (P-Z) curves for four developmental stages from each location were constructed from 14C uptake at six irradiances (22-1,100 pmol quanta m-2 s-l) in the laboratory. Photoinhibition in the periphyton from the two shaded sites declined with development, indicating that self-shading significantly influenced photosynthesis in older communities. Photoinhibition was absent, however, in all of the developmental stages from the high light site. Maximum photosynthesis (P,,,,,) and slope ((x) of the light-limited portion of the chlorophyll-specific light response decreased > 40% in developing periphyton at all sites. Significant negative correlations between biomass and biomass-specific P,,,,, suggested that light or metabolic substrates became progressively more limiting during development. Although there was little community-level evidence of shade adaptation during development (photosynthesis did not saturate at lower light intensities as development proceeded), periphyton understories appear to retain considerable photosynthetic potential despite significant shading by upper layers.

Epilithic biomass in a large gravel‐bed river (the Garonne, France): a manifestation of eutrophication?

“…This pigment, which is present in every alga, varies in quantity as a function of species, of the cells' nutritive state and of the light environment (Steele and Baird, 1965;Heaney, 1978;Harris, 1980). With the biofilm, there is also a vertical accumulation of cell layers that produce a self-shading effect (Steinman and McIntire, 1987;Hill and Boston, 1991). This is possibly the reason why the relationship of chla as a function of AFDM gave a significant relationship when fitted to a log model ( Figure 5), with the quantity of chla levelling off as the AFDM increases.…”

Periphyton metabolism along a nutrient gradient in a desert river (Truckee River, Nevada, USA)

“…For example, Busch and Fisher (1981) reported Q 10 temperature coeffi cients of 1.5 for gross primary production and 2.5 for community respiration in Sycamore Creek. Photosynthesis of epilithic algae has been reported to be light saturated at intensities ranging from 100 to 600 µE m -2 s -1 (e.g., Boston and Hill, 1991;Dodds et al, 1999;Hill, 1996;Hill and Boston, 1991). Compared to these values, PAR intensities in November were still relatively high (>600 µE m -2 s -1 for about 4 h each day, Table 1), and may account for the relatively moderate reduction in GPP.…”

Periphyton production on wood and sediment: substratum-specific response to laboratory and whole-lake nutrient manipulations

“…Experiments have shown conclusively that light and nutrient availability strongly affect periphyton abundance and production in freshwater ecosystems (Round 1961, Bjö rk-Ramberg 1984, Shortreed et al 1984, Fairchild et al 1985, Peterson et al 1985, Mazumder et al 1989, Hill and Boston 1991, Bothwell 1993, Fairchild and Sherman 1993, Rosemond 1993, Hill 1996. In addition, substratum (e.g., macrophytes, rocks, sediment) affects the light and nutrient environment of associated periphyton (Sand-Jensen and Borum 1991, Burkholder 1996, Lowe 1996, Krause-Jensen and Sand-Jensen 1998.…”