Mesozooplankton taxonomic density collected using a 1-m diameter ring net with 200-μm mesh at Palmer Station, Antarctica during Palmer LTER field seasons, 2017-2020

Zooplankton are a morphologically and taxonomically diverse group of animals. Many zooplankton feed on phytoplankton in surface waters and thus provide a link between primary producers and higher trophic levels. The numerical density of common mesozooplankton taxa was determined at Palmer LTER Stations B and E. Samples were collected with a 1-m diameter, 200-μm mesh ring net towed obliquely from the surface to a target depth of 50 m and back. Tows were conducted during daytime, and sampling frequency was nominally twice weekly while personnel were at Palmer Station between the months of November and March. The preserved samples were size-fractionated with nested sieves into five size classes (0.2−0.5, 0.5−1, 1−2, 2−5, and >5 mm) prior to microscopic enumeration. Data are provided for the following taxa: copepods Oithona spp., Calanoides acutus (>1 mm only), Calanus propinquus (>1 mm only), Rhincalanus gigas (>1 mm only), and small calanoids (0.2−1 mm), chaetognaths, asteroid larvae, nemertean larvae, and foraminifera (not quantified in all years). Individual size fractions were split and subsampled such that at least 100 individuals of the most abundant taxon were present. Density varies across taxa, seasonally, among years, and between sampling stations. Units of density are individuals per cubic meter.