VERY interesting Seminar TODAY


Speaker:  Andrea Albertin (PhD Exit), Soil and Water Science Dept
Advisor: James Sickman, Mark Clark
Time:  3 p.m.
Location:  Room 1151, McCarty Hall A 

Increased abundance of mat-forming filamentous macroalgae has been observed in many of Florida’s karst springs over the past 50 years and has been associated to increased ambient nitrate concentrations. However, no quantitative relationship exists between nitrate concentrations and algal biomass. We conducted four studies to assess nutrient dynamics in Florida springs, particularly the effects of increased nitrate levels on the growth of Lyngbya wollei, and Vaucheria sp. Threshold values of nitrate for algal growth were studied in two recirculating stream experiments. The stable isotopes of macroalgae and spring sediments (•15N and •13C) as well as nitrate (•15N-NO3 and •18O-NO3) and dissolved organic carbon (•13C) in spring water were measured regionally, at multiple boil sites throughout North Central Florida and the Panhandle and along four spring river runs. Additionally, seasonal variation in stable isotope composition of macroalgae was measured over the course of one-year at two springs. In one study, nutrient cycling within algal mats and in adjacent sediments was assessed using interstitial water samplers and advective and diffusive flow through mats was estimated. Results indicate that Lyngbya wollei growth is stimulated by nitrate additions despite very low phosphorus conditions. Multiple factors are likely affecting stable isotopic values in macroalgae, but results point to relatively distinct species-specific ä13C compositions, which may be indicative of an algae’s relative uptake of and degree of preference for CO2 (aq) vs. HCO3-  as a carbon source. Unlike ä13C, macroalgal ä15N values did not show strong species-specific trends. Finally, thick algal mats contain relatively large amounts of nutrients, particularly NH4+ and organic phosphorous, and diffusion of nutrients occurs out of algal mats into the sediment as well as into the overlying water column.

Kelly Jacoby | Program Assistant | University of Florida / IFAS | Soil & Water Science Department, PO Box 110510, Gainesville, FL 32611 | 352-392-1803 x 342 | Fax: 352-392-3399 | [log in to unmask]<mailto:[log in to unmask]>