23 D15. Paleontology (Posters)

Friday, 20 March 2020
1:30 PM - 5:30 PM
Grand Ballroom A–D

POPULATION AND SIZE DISTRIBUTION OF CIBICIDES ANTARCTICUS ON ADAMUSSIUM COLBECKI WITHIN EXPLORERS COVE, ANTARCTICA

Paper number: 23-6
Program: Technical Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

We studied the population and size distribution of the parasitic foraminifer Cibicides antarcticus living on the shell of the Antarctic scallop Adamussium colbecki within Explorers Cove, Western McMurdo Sound, Antarctica. Previous work examined populations and parasite load between two distinct geographic locations, but our study focuses on the population and size distribution of C. antarcticus within one embayment, Explorers Cove. We hypothesize that if A. colbecki are living in the same embayment and have one recruitment event, then populations and their size distributions should be similar; but, if they have differing populations and sizes, they likely are recruiting from very localized microhabitats with varying recruitment events.

Live A. colbecki were collected from the Jamesway (water depth 24.4 m), Smallberg (9.1 m), and Anoxic Pit (9.1 m) sites in Explorers Cove. Five top valves were examined for C. antarcticus under 75x magnification. The foraminifera were counted, their spatial distribution noted, and their largest diameter was measured using ImageJ. All data from each site was pooled to compare the sites.

Results indicate that all the sites had different populations of parasitic C. antarcticus. Smallberg had the most parasitic foraminifera (n = 663), followed by Jamesway (n = 319); the Anoxic Pit site had the fewest (n = 55). The largest size classes (0.70–1.30 mm) occurred at the Anoxic Pit and Smallberg sites, while the smallest size classes (0.18–0.70 mm) were found at Jamesway, the deepest site. The average size of Cibicides was also smaller at Jamesway (0.71 mm), compared to Smallberg (0.92 mm), and Anoxic Pit (0.94 mm). In general, C. antarcticus recruits to the youngest part of the scallop shell while larger adults are found on oldest part of the shell. The skewed size frequency distributions and differing population sizes suggest that C. antarcticus has localized microhabitat recruitment in Explorers Cove, rather than one synchronous recruitment event.

Geological Society of America Abstracts with Programs. Vol. 52, No. 2

doi: 10.1130/abs/2020SE-343189

© Copyright 2020 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.