ARE FRESHWATER BENTHIC PERIPHYTON SODIUM AND CHLORIDE CONTENTS HOMEOSTATIC WHEN EXPOSED TO LOW-LEVEL INCREASES IN DISSOLVED SODIUM CHLORIDE?
Sodium, chloride, and other ion concentrations are increasing in fresh waters due to anthropogenic activities. Salts can be nutritional subsidy, but may also cause stress at high levels; we know little about how freshwater enrichment can affect biota. Terrestrial autotroph ion concentrations can relate positively to environmental ion concentrations; this same pattern may occur for freshwater autotrophs. We conducted a greenhouse experiment where we exposed periphyton on cobbles collected from a local, low-level salt stream in recirculating streams with increasing concentrations of sodium chloride added (ambient, 6, 32, and 64 mg/L, N=3 per treatment). After 26-d, we harvested all periphyton and examined the elemental and ionic content of the dried material. We found no evidence that periphyton sodium contents were positively related to water concentrations at these low concentrations; chloride and other elemental analysis is still in process. Periphyton sodium concentration appears to be homeostatic (i.e., no positive relationship between cell and environmental concentrations) at the concentrations examined, which may exert a metabolic cost of osmoregulation with increasing concentrations. The potential metabolic cost of this homeostasis should be examined in future studies.
Michelle Evans-White (Co-Presenter/Co-Author), University of Arkansas, email@example.com;
Sally Entrekin (Co-Presenter/Co-Author), Virginia Tech, firstname.lastname@example.org;
Natalie Clay (Co-Presenter/Co-Author), Louisiana Tech University, email@example.com;
Samuel Dias (Primary Presenter/Author), University of Arkansas, firstname.lastname@example.org;