Submitted to: International Journal of Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2011
Publication Date: 7/13/2011
Citation: Evens, T.J., Niedz, R.P. 2011. Mapping the fundamental niches of two freshwater microalgae, Chlorella vulgaris (Trebouxiophyceae) and Peridinium cinctum (Dinophyceae), in 5-dimensional ion space. International Journal of Ecology. 2011: 1-12.
Interpretive Summary: Defining the potential impacts of agriculturally-derived ions (i.e. 'nutrients') on aquatic community structure will require the ability to quantify the main effects and interactions of a suite of ions. This demands the use of multivariate experiment designs that are free of ion confounding and approached from the standpoint of 'ions as independent factors'. To this end we quantified the ion-based, "Grinnellian" niche for two microalgae commonly found in Southeast Florida for five ions that are important nutrients, i.e. nitrate and phosphate, and/or as drivers of bulk solution chemistry, i.e. potassium, sodium and chloride. We discovered that these two genetically distinct algae share over 95% of the same Grinnellian niche, although their growth rates and maximal cell densities differ within this space. This type of research will allow us to determine the fundamental responses of a complex community of algae exposed to a complex mixture of nutrients and pesticides and facilitate a rational analysis of potential impacts as well as suggest primary targets for future BMPs.
Technical Abstract: A five dimensional experimental design, i.e. a five component ion mixture design for nitrate, phosphate, potassium, sodium and chloride projected across a total ion concentration gradient of 1-30 mM was utilized to map the ion-based, scenopoetic, or ‘Grinnellian’, niche space for two freshwater algae, Chlorella vulgaris and Peridinium cinctum, in relation to growth rates and maximum cell densities. The niches for the two algae overlapped for ca. 95% of the ion mixtures, although the regions of maximum growth rates and maximal cell densities were unique to each alga. Both C. vulgaris and P. cinctum exhibited very similar positive responses to the cations and negative responses to the anions used in this study. Beyond these anion/cation effects there was very little evidence of any significant ion-specificity. It was determined that total ion concentration for these five ions, from 1-30 mM, does not directly affect either growth rate or maximal cell densities for either alga, although it does play an interactive role with several ions. There is no evidence that either K+ or Na+ is essential for growth. This study is the first that we are aware of to attempt the mapping of an ion-based Grinnellian niche. The implications of the experimental design utilized and the potential utility of this type of approach are discussed.