Diel Zooplankton Tows

The diel samples were collected every 4 hours over a 24 hour period. Diaphragm pump used: Sandpiper, Warren Rupp. Flow rate of pump: 2.0 L/ sec

The water column was divided into epilimnion, metalimnion and hypolimnion based on the CTD profiles of water temperature and DO concentration. If the epilimnion was very deep, it was divided into an upper and lower epilimnion during certain times of the year. A fully mixed water column was divided in half. Water was pumped at 1-m intervals in each zone for a period of time to fully sample the zone and equal approximately 1m³ of water.

Net: The water was pumped through a 64 µm mesh net.

Depth: Pumped to 1-m above the bottom.

Zooplankton Abundance: At least 600 zooplankton were counted and identified per sample.

Zooplankton Biomass: For biomass determination, 25 immature and 10 adults were measured per sample (if they were 8% of the sample). For zooplankton biomasses less than 8% of the sample, a default weight was used either from published literature or based on lengths of zooplankton from this study (IFYLE 2005).

Large invertebrate predators: The whole sample was screened through a 600 µm mesh and large predators such as Leptodora and Bythotrephes were counted and their biomasses determined.

For further information, contact:

Joann F Cavaletto
NOAA-GLERL, 2205 Commonwealth Blvd.
Ann Arbor, MI 48105-2945
734-741-2356