Mapping the fundamental niches of two freshwater microalgae, chlorella vulgaris (Trebouxiophyceae) and peridinium cinctum (Dinophyceae), in 5-dimensional ion space

Abstract

The fundamental niche defined by five ions, NO 3 -, PO 4 3 -, K +, Na +, and (Cl-), was mapped for Chlorella vulgaris (Trebouxiophyceae) and Peridinium cinctum (Dinophyceae) growth rates and maximum cell densities in batch cultures. A five dimensional ion-mixture experimental design was projected across a total ion concentration gradient of 1 to 30mM to delineate the ion-based, potential niche space, defined as the entire n-dimensional hypervolume demarcated by the feasible ranges of the independent factors under consideration. The growth rate-based, fundamental niche volumes overlapped for ca. 94 of the ion mixtures, although the regions of maximal growth rates and cell densities were different for each alga. Both C. vulgaris and P. cinctum exhibited similar positive responses to cations and negative responses to anions. It was determined that total ion concentration for these five ions, from 1 to 30mM, did not directly affect either growth rate or maximal cell density for either alga, although it did play an interactive role with several ions. This study is the first that we are aware of to attempt the mapping of a multivariate, ion-based, fundamental niche volume. The implications of the experimental design utilized and the potential utility of this type of approach are discussed. © 2011 Terence J. Evens and Randall P. Niedz.