Phosphorus HABs

Samples were collected in Saginaw Bay, Lake Huron during August, 2005 because of a lack of algal blooms in Lake Erie that summer. 2006 samples were from the western basin of Lake Erie.

- Surface water samples were collected from 0.5 to 1 m below the surface with either a submerged bucket or Niskin bottle cascade - Total phosphorus was measured on 30 ml aliquots after persulfate digestion according to standard colorimetric analysis (Murphy and Riley 1962) - Chlorophyll a was extracted from GF-C filters in 90% ethanol an measured using the Welschmeyer method (1994). - Microcystin toxin was analyzed via ELISA on filtered seston (analyzed by A. Wilson at CILER/GLERL) - Alakaline phosphatase activity for Micocystis colonies was assessed using Enzyme-labeled fluorescence (ELF 97, Invitrogen Corporation). 10 ml of unfiltered water was inoculated with a 50 µl of a 1:20 substrate to buffer solution and allowed to react for 2 hrs. Samples were then filtered onto 1 µm black membrane filters and mounted on microscope slides. The slides were frozen at -20 degC for up to 6 months before visual analysis on an epifluorescence Microscope. - Phytoplankton samples were preserved with a 1% Lugols solution until enumerated via the inverted microscope technique, with counts made at several magnifications (100X - 1000X) to accurately assess the density of both large and small species. Cell volumes (exclusive of spines, horns and sheaths) were calculated from cell dimensions estimated using images captured with a digital camera at 1000X and analyzed with image-analysis software. Phytoplankton volumes were converted to wet biomass assuming a specific gravity of 1 g cm-3.

Contact information:

Geoffrey Horst
Department of Fisheries and Wildlife
Michigan State University
13 Natural Resources
East Lansing, MI 48824-1222
(517) 353-3234
(517) 432-1699 Fax
email: