Ecology of the burrowing amphipod, Pontoporeia affinis, in Lake Michigan / by Wayne Paul Alley.

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investigations. The standard on-station procedure during the macrobenthos sampling was: the ship was stopped on station; the depth, in
feet, was recorded from the fathometer and converted to meters; standard marine meteorological observations were taken; water transparency
was determined by a white secchi disk; the surface temperature was
measured with a thermistor; a bathythermograph cast was made; and
three bottom grab samples were taken.
The sampler was opened and the sediment transferred into a
large washtub in an undisturbed condition. The sediment texture was
classified as sand, sandy silt, silt, layered, and hard bottom after the
method described by Powers and Robertson (1968), Layered sediment
consisted of a layering of silt-clayey silt over stiff plastic clay, and the
hard bottom sediments included gravel, pebbles, and glacial till.
The macrobenthic invertebrates were separated from the sediment
by means of an elutriation-screening device (Powers and Robertson
1965) (Fig. 6). A whole sample, including washings from the bottom
samplers, was transferred from the washtub to the hopper of the
separating device. The sediment was agitated by hosing with water
after which the hopper was tipped to pour the supernatant water with
suspended organisms into an attached cylindrical screen of 0. 5 mm
mesh. The fine sediments passed through the screen while the organisms were collected in a pint mason jar that was attached to the screen
by a canvas sleeve. The hosing, agitation, and decanting were repeated