NOAA - Great Lakes Environmental Research Laboratory
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Microzooplankton samples were collected from CTD, immediately preserved with acid Lugol’s iodine (1% final concentration) and stored at 4oC in opaque containers. In the land laboratory, the samples were settled in 50 to 100 ml chambers overnight. The entire chamber was scanned for ciliates, dinoflagellates ›20 m, sarcodines (heliozoans, loricated and naked amoeba), and rotifers under a differential interference contrast inverted microscope (100-600x). Microzooplankton were sized using an eyepiece micrometer. Their volumes were corrected for shrinkage due to fixation and converted to carbon biomass according to Putt and Stocker (1989) and Menden-Deuer and Lessard (2000). Rotifer biomass was calculated according to Fahnenstiel et al. (1998). Copepod nauplii and other crustaceans were not included in these analyses.
In September 2005, an underway survey system was used to measure the biomass distribution of microzooplankton. The system consisted of a towed V-fin depressor (PSS) and a double diaphragm air-driven peristaltic pump, which continuously supplied lake water to the shipboard lab via a ?” ID hose connected to the towed instrument. The collected water was used for shipboard flow-cytometry . Samples were collected every 15 minutes along the HE›AS transect. At the ship speed of 4.5 kts, it resulted in a horizontal resolution in the shipboard data of ca. 1.5 nautical miles. Microzooplankton were enumerated in real-time using an imaging-in-flow system (FlowCAM; Sieracki et al. 1998), which was calibrated using inert beads. Microzooplankton linear dimensions were recorded by the FlowCAM software and later used to calculate ESD and biomass as described above (no correction for shrinkage was done in this case as the cells were measured in vivo).
Fahnenstiel GL, Krause AE, McCormick MJ, Carrick HJ, Schelske CL (1998) The structure of the planktonic food-web in the St. Lawrence Great Lakes. J. Great Lakes Research 24: 531-554
Menden-Deuer S, Lessard EJ (2000) Carbon to volume relationships for dinoflagellates, diatoms, and other protist plankton. Limnol Oceanogr 45:569-579
Putt M, Stoecker DK (1989) An experimentally determined carbon - volume ratio for marine oligotrichous ciliates from estuarine and coastal waters. Limnol Oceanogr 34:1097-1103
Sieracki CK, Sieracki ME, Yentch CS (1998) An imaging-in-flow system for automated analysis of marine microplankton. Mar Ecol Prog Ser 168:285-296
Peter J. Lavrentyev
Department of Biology
University of Akron
Akron, OH 44325-3908
phone: 330-972-7922
email:
