The Autecology of Eudiaptomus cf drieschi (Poppe & Mrazek 1895 ...

using a modification of the sugar flotation method introduced by Onbe (1978) and
described in Ban & Minoda (1992). Sediments were washed with filtered lake water
(0.45 µm) through a 45.0 µm mesh sieve. Material remaining on the sieve was rinsed
into 250 ml. Nalgene centrifuge bottles, combined with a supersaturated sugar solution
(1 kg per 1 liter), and centrifuged at 3,000 rpm for 5 minutes. The supernatant was then
washed through a 20 µm mesh net to remove the sugar and collect the eggs. Eggs were
carefully rinsed into petri-dishes and counted under a Wild binocular dissecting
microscope. Diaptomid eggs were incubated in controlled light and temperature
conditions (Shel-Lab Low Temperature Incubators) in filtered (0.45µm) lake water and
hatching of new - born nauplii was recorded.
The number of benthic resting eggs per gram of dry weight sediment was obtained by:
(a / b) * (# eggs / DW (g) ) = # eggs / g (DW) (2)
where a is the wet weight (g) of the sediment portion to be dried, b is the wet weight (g)
of the sediment portion for egg counts. The number of eggs per portion is then divided
by the dry weight (DW) of sediments. Then the density (number of eggs per square
meter) was calculated for each sample by finding the number of eggs in the surface area
of the core ( S.A. = square of r * ), which is divided into the number of eggs multiplied
by 10 3 .
.2. 3 Diel Survey
Diel sampling took place at Station F on April 1-2 (spring), September 29-30
(fall) 1997, and June 9-10 (summer) 1998. The research vessel (RV Hermona) was on
station throughout the survey periods. Duplicate zooplankton samples were taken every
2 hours with a 20 L Schindler - Patalas trap over a 24 hour period (dawn / dusk / dawn).
Zooplankton samples were taken from depths 1, 3, 5, 7, 10, 15, and 1meter from bottom.
Samples were filtered through a 20µm mesh net and preserved in 4% buffered formalin.
Samples were concentrated through a 20µm mesh net to a smaller volume in the lab.
The entire sample was counted and all life stages were enumerated with a Wild
binocular, dissecting microscope. The parameters: chlorophyll, oxygen, temperature,
light, and Secchi disc depth were measured.
Phytoplankton chlorophyll a samples were taken with a 5-liter Van Dorn bottle
at each sampling depth. The water was filtered on-board for size fractionation of net