Flow, nutrients, and light availability influence Neotropical epilithon biomass and stoichiometry

Authors

Tyler J. Kohler, University of Nebraska at LincolnFollow
Thomas N. Heatherly II, University of Nebraska at LincolnFollow
Rana W. El-Sabaawi, Cornell University & University of VictoriaFollow
Eugenia Zandona, Drexel UniversityFollow
Michael C. Marshall, University of Georgia-AthensFollow
Alexander S. Flecker, Cornell UniversityFollow
Catherine M. Pringle, University of GeorgiaFollow
David N. Reznick, University of California, RiversideFollow
Steven A. Thomas, University of Nebraska - LincolnFollow

Document Type

Article

Date of this Version

8-28-2012

Citation

Freshwater Science, 2012, 31(4):1019–1034

DOI: 10.1899/11-141.1

Comments

2012 by The Society for Freshwater Science

Abstract

Light, nutrient availability, and flow are strong factors controlling the elemental composition and biomass of epilithon in temperate stream ecosystems. However, comparatively little is known about these relationships in tropical streams. We investigated how gradients of light and nutrient availability, seasonality, and habitat influenced epilithon biomass, chlorophyll a, and nutrient ratios in montane streams of Trinidad, West Indies. We sampled 4 focal tributaries of a single river, 2 of which had canopies experimentally thinned, every other month over a 2-y period to observe temporal dynamics and light effects on epilithon. We also sampled 18 sites across Trinidad’s Northern Range Mountains once each in a wet and dry season to examine the effects of naturally occurring differences in light and dissolved nutrient availability on epilithic characteristics. We found greater chlorophyll a concentrations in habitats with greater light availability, but the effect of light on epilithon stoichiometry differed between the site-survey and focal-tributary data. In general, epilithic C: nutrient ratios decreased with increasing dissolved nutrient concentrations, but relationships between nutrient availability and biomass probably were obscured by naturally high dissolved N and P concentrations in many of the streams. Season and habitat type had profound effects on epilithon variables. Biomass and % C generally decreased in riffles and under wet- season conditions. These results suggest multiple controls for the quantity and quality of stream epilithon and have important implications for in-stream consumers.