Response of an algal assemblage to nutrient enrichment and shading in a Hawaiian stream

    Authors

    S. H. Stephens; A. M. D. Brasher;C. M. Smith

    Comments

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    Abbreviated Journal Title

    Hydrobiologia

    Keywords

    Stream; Benthic algae; Diatoms; Nutrient-diffusing substrate; Hawaii; Pulse amplitude modulated (PAM) fluorometer; RESOURCE COMPETITION; KANEOHE BAY; LIGHT; WATER; PERIPHYTON; COMMUNITY; DYNAMICS; GRADIENT; NITROGEN; BIOMASS; Marine & Freshwater Biology

    Abstract

    To investigate the effects of nitrate enrichment, phosphate enrichment, and light availability on benthic algae, nutrient-diffusing clay flowerpots were colonized with algae at two sites in a Hawaiian stream during spring and autumn 2002 using a randomized factorial design. The algal assemblage that developed under the experimental conditions was investigated by determining biomass (ash-free dry mass and chlorophyll a concentrations) and composition of the diatom assemblage. In situ pulse amplitude-modulated fluorometry was also used to model photosynthetic rate of the algal assemblage. Algal biomass and maximum photosynthetic rate were significantly higher at the unshaded site than at the shaded site. These parameters were higher at the unshaded site with either nitrate, or to a lesser degree, nitrate plus phosphate enrichment. Analysis of similarity of diatom assemblages showed significant differences between shaded and unshaded sites, as well as between spring and autumn experiments, but not between nutrient treatments. However, several individual species of diatoms responded significantly to nitrate enrichment. These results demonstrate that light availability (shaded vs. unshaded) is the primary limiting factor to algal growth in this stream, with nitrogen as a secondary limiting factor.

    Journal Title

    Hydrobiologia

    Volume

    683

    Issue/Number

    1

    Publication Date

    1-1-2012

    Document Type

    Article

    Language

    English

    First Page

    135

    Last Page

    150

    WOS Identifier

    WOS:000299925200010

    ISSN

    0018-8158

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