Didymosphenia geminata habitat requirements are unique and variable for cell establishment and mat accumulation

Abstract

Didymosphenia geminata is a freshwater diatom that can form thick mats that alter benthic habitat and community structure. In North America, mats now occur in streams outside historical observation ranges, necessitating a better understanding of conditions that support colonization and mat development to predict future occurrences and manage nuisance mats. A subbasin-level approach to relate D. geminata to habitat parameters was taken to minimize ecoregional and climatic differences among 24 sites in the geologically diverse upper Tennessee River basin, USA. Mat occurrence peaked at parameter concentrations slightly above those where D. geminata was absent; supporting previous studies that suggest nutrient limitation induces mat formation. However, unlike previous findings that suggest low dissolved phosphorus (P) is the main trigger of stalk formation, mat presence in this study was not correlated to dissolved P. Several water quality parameters, including water chemistry, temperature, and discharge, were correlated with D. geminata presence and abundance, but the strength of these relationships varied seasonally. These results support the idea that a hierarchical framework of habitat parameters is required for colonization and mat development, and that mat formation is related to stress. Differing conditions supporting cell proliferation and mat development may help explain the inconsistent nature of mats across a region. As parameters other than P may also be important in triggering stalk production, manipulating those may be useful in managing mat biomass.