A survey of Staurastrum species across diverse habitats in northern Michigan.

Abstract

Staurastrum is a desmid in the family Desmidiaceae which proliferates in various aquatic habitats. We sampled five habitats in northern Michigan and documented the Staurastrum species diversity and relative abundance at each site. Additionally, each site was analyzed for phosphate, nitrate, ammonia, silicon dioxide, and calcium as well as the conductivity and pH of the water in order to determine if there is a correlation with species diversity and abundance. Our analysis found that the abundance of Staurastrum species is greatest between a pH of 6 and 7. As pH increases from 4.5 to 8.5 the species diversity decreases. In relation to calcium, we found that St. gracile, St. alternans, St. dejectum, and St. brevispinum reach highest abundance at calcium levels between 50 mg/L and 70 mg/L. St. orbiculare and St. rugulosum prefer calcium levels less than 20 mg/L. Preference of conductivity levels varied among species. However, as the nubmer of soluble ionic compounds increases the number of species decreases. No significant correlation was made between species diversity and relative abundance and the levels of phosphate, nitrate, and ammonia. These nutrient levels did not differ enough between habitats.