Applying the light: nutrient hypothesis to stream periphyton

Journal Article · Fri Jan 01 04:00:00 EST 2010 · Freshwater Biology

DOI:https://doi.org/10.1111/j.1365-2427.2009.02309.x· OSTI ID:1034675

Fanta, S E ^[1]; Hill, Walter ^[2]; Smith, Timothy B ^[1]; Roberts, Brian J ^[3]

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1. University of Illinois
2. University of Illinois, Urbana-Champaign
3. ORNL

The light:nutrient hypothesis (LNH) states that algal nutrient content is determined by the balance of light and dissolved nutrients available to algae during growth. Light and phosphorus gradients in both laboratory and natural streams were used to examine the relevance of the LNH to stream periphyton. Controlled gradients of light (12-426 mol photons m{sup -2} s{sup -1}) and dissolved reactive phosphorus (DRP, 3-344 {mu}g L{sup -1}) were applied experimentally to large flow-through laboratory streams, and natural variability in canopy cover and discharge from a wastewater treatment facility created gradients of light (0.4-35 mol photons m{sup -2} day{sup -1}) and DRP (10-1766 {mu}g L{sup -1}) in a natural stream. Periphyton phosphorus content was strongly influenced by the light and DRP gradients, ranging from 1.8 to 10.7 {mu}g mg AFDM{sup -1} in the laboratory streams and from 2.3 to 36.9 {mu}g mg AFDM{sup -1} in the natural stream. Phosphorus content decreased with increasing light and increased with increasing water column phosphorus. The simultaneous effects of light and phosphorus were consistent with the LNH that the balance between light and nutrients determines algal nutrient content. In experiments in the laboratory streams, periphyton phosphorus increased hyperbolically with increasing DRP. Uptake then began leveling off around 50 {mu}g L{sup -1}. The relationship between periphyton phosphorus and the light: phosphorus ratio was highly nonlinear in both the laboratory and natural streams, with phosphorus content declining sharply with initial increases in the light: phosphorus ratio, then leveling off at higher values of the ratio. Although light and DRP both affected periphyton phosphorus content, the effects of DRP were much stronger than those of light in both the laboratory and natural streams. DRP explained substantially more of the overall variability in periphyton phosphorus than did light, and light effects were evident only at lower phosphorus concentrations ({approx}< 25 {mu}g L{sup -1}) in the laboratory streams. These results suggest that light has a significant negative effect on the food quality of grazers in streams only under a limited set of conditions.

• Research Organization: Oak Ridge National Laboratory (ORNL); Oak Ridge National Environmental Research Park
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1034675
• Journal Information: Freshwater Biology, Journal Name: Freshwater Biology Journal Issue: 5 Vol. 55; ISSN 0046-5070; ISSN FWBLAB
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
60 APPLIED LIFE SCIENCES
ALGAE
AUFWUCHS
FOOD
HYPOTHESIS
NUTRIENTS
PHOSPHORUS
PHOTONS
WATER
benthic algae
light : nutrient hypothesis
periphyton
stoichiometry
stream