Species composition, seasonal abundance and population structure of chaetognaths in Admiralty Bay (Antarctic)

Abstract

Abstract Although chaetognaths inhabiting polar ecosystems are relatively well known, there are few reports on their functioning in the Antarctic coastal plankton community. The presented results provide the first comprehensive description of population structure of chaetognaths in the neritic zone west of the Antarctic Peninsula. The studies were performed on samples collected in Admiralty Bay, from December 1994 to June 1995. Following six chaetognath species were determined: Eukrohnia hamata, E. bathypelagica, E. fowleri, Pseudosagitta gazellae, P. maxima and Solidosagitta marri. The representatives of Eukrohnia were observed almost throughout the research period, whereas those of Pseudosagitta and Solidosagitta were found only during first four months of our investigation. Eukrohnia hamata showed a strong dominance in respect to abundance (max. 445 ind./1000 m3). The mean abundance of all taxa significantly fluctuated in the study period and across weeks. Generally, all species were represented by the first three maturity stages (I-III), individuals stage IV occurred sporadically, and mature specimens (stage V) were not recorded at all. Morphometric analysis of the most abundant species showed distinct differences in their total length and body proportions. Our findings may suggest that chaetognath populations in Admiralty Bay are migrant, dependent on the inflow of water from the Bransfield Strait, but to prove this statement further, round year study is necessary.