dc.contributor.author	Beck, Whitney S., author
dc.contributor.author	Hall, Ed K., author
dc.contributor.author	PLOS ONE, publisher
dc.date.accessioned	2018-10-23T12:56:13Z
dc.date.available	2018-10-23T12:56:13Z
dc.date.issued	2018-10-18
dc.description.abstract	Assessing algal nutrient limitation is critical for understanding the interaction of primary production and nutrient cycling in streams, and nutrient diffusing substrate (NDS) experiments are often used to determine limiting nutrients such as nitrogen (N) and phosphorus (P). Unexpectedly, many experiments have also shown decreased algal biomass on NDS P treatments compared to controls. To address whether inhibition of algal growth results from direct P toxicity, NDS preparation artifacts, or environmental covariates, we first quantified the frequency of nutrient inhibition in published experiments. We also conducted a meta-analysis to determine whether heterotrophic microbial competition or selective grazing could explain decreases in algal biomass with P additions. We then deployed field experiments to determine whether P-inhibition of algal growth could be explained by P toxicity, differences in phosphate cation (K vs. Na), differences in phosphate form (monobasic vs. dibasic), or production of H2O2 during NDS preparation. We found significant inhibition of algal growth in 12.9% of published NDS P experiments as compared to 4.7% and 3.6% of N and NP experiments. The meta-analysis linear models did not show enhanced heterotrophy on NDS P treatments or selective grazing of P-rich algae. Our field experiments did not show inhibition of autotrophic growth with P additions, but we found significantly lower gross primary productivity (GPP) and biomass-specific GPP of benthic algae on monobasic phosphate salts as compared to dibasic phosphate salts, likely because of reduced pH levels. Additionally, we note that past field experiments and meta-analyses support the plausibility of direct P toxicity or phosphate form (monobasic vs. dibasic) leading to inhibition of algal growth, particularly when other resources such as N or light are limiting. Given that multiple mechanisms may be acting simultaneously, we recommend practical, cost-effective steps to minimize the potential for P- inhibition of algal growth as an artifact of NDS experimental design.	en_US
dc.description.sponsorship	Published with support from the Colorado State University Libraries Open Access Research and Scholarship Fund.
dc.format.medium	born digital
dc.format.medium	articles
dc.identifier.bibliographicCitation	Beck WS, Hall EK (2018) Confounding factors in algal phosphorus limitation experiments. PLoS ONE 13(10): e0205684. https://doi.org/10.1371/journal.pone.0205684
dc.identifier.doi	https://doi.org/10.1371/journal.pone.0205684
dc.identifier.uri	https://hdl.handle.net/10217/192615
dc.language	English	en_US
dc.language.iso	eng	en_US
dc.publisher	Colorado State University. Libraries	en_US
dc.relation.ispartof	Open Access Research and Scholarship Fund (OARS)
dc.rights.license	This article is open access and distributed under the terms and conditions of the Creative Commons Attribution 4.0 International (CC BY 4.0).
dc.rights.uri	https://creativecommons.org/licenses/by/4.0/
dc.subject	algae
dc.subject	nutrients
dc.subject	meta-analysis
dc.subject	nutrient diffusing substrate
dc.subject	freshwater ecology
dc.title	Confounding factors in algal phosphorus limitation experiments	en_US
dc.type	Text	en_US

Confounding factors in algal phosphorus limitation experiments

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