Antarctic Chaetognatha: United States Antarctic Research Program Eltanin Cruises 8–28, Part 1
- Louis S. Kornicker
Published Online: 16 MAR 2013
Copyright 1983 by the American Geophysical Union.
Biology of the Antarctic Seas XI
How to Cite
Alvariño, A., Hosmer, S. C. and Ford, R. F. (1983) Antarctic Chaetognatha: United States Antarctic Research Program Eltanin Cruises 8–28, Part 1, in Biology of the Antarctic Seas XI (ed L. S. Kornicker), American Geophysical Union, Washington, D. C.. doi: 10.1029/AR034p0129
- Published Online: 16 MAR 2013
- Published Print: 1 JAN 1983
Print ISBN: 9780875901800
Online ISBN: 9781118664704
- Eltanin cruises;
This study considered the species composition, distribution, and abundance of Chaetognatha obtained in the Antarctic, Subantarctic, and adjacent regions of the Pacific and Atlantic oceans during the United States Antarctic Research Program. The samples were collected from April 1963 to May 1967, during Eltanin cruises 8-28, using open-closing and none losing plankton nets. The distribution and abundance of each species are discussed for the three bathymetric levels, epipelagic (200-0 m ), mesopelagic (1000-200 m ) , and bathypelagic (below 1000 m depth). These distributions also are considered in relation to season, oceanographic conditions, and pertinent ocean dynamics. Eighteen species of Chaetognatha occurred in these collections. Eukrohnia hamata was the most common species in the Antarctic-Subantarctic region, in both abundance of individuals and frequency of occurrences. Sagitta tasmanica was the most abundant species in the Subtropical Convergence region. Typical Antarctic-Subantarctic species were Eukrohnia bathyantarctica, Sagitta gazellae, S. marri, S. planctonis, and S. tasmanica. Species cosmopolitan in the deep layers were Eukrohnia bathypelagica, E. Fowleri, and E. hamata, the latter inhabiting the epipelagic strata in the high latitudinal regions. Other cosmopolitan meso-bathypelagic species were S. decipiens, S. macrocephala, maxima, and zetesios. Krohnitta subtilis, Pterosagitta draco, S. bipunctata, S. hexaptera, and S. minima were species typical to the north and south central Pacific waters. Stray specimens of S. lyra (oceanic, cosmopolitan in the warm and temperate regions of the Atlantic and Indian oceans and Asiatic Pacific) reached the Subtropical Convergence zone of the South Pacific via the West Wind Drift (A. Alvarino, unpublished data). Species previously found in the region surveyed, Heterokrohnia mirabilis Ritter-Zahony, S. bierii Alvarifio, and S. enflata Grassi, were not obtained during cruises 8-28. The absence of S. bierii at locations off southern Chile could have resulted from the lack of stations in the Chilean coastal area. Tables provide the location and other pertinent data for the samples and the numerical abundance of the species of Chaetognatha obtained in each sample. Maps present in quantitative form the distribution of the species for different seasons and bathymetric layers. The abundance and distribution of each species are discussed in relation to environmental conditions, including ocean dynamics. North-south transects at 160°E and 140°W are analyzed and data presented in tables and depth profile maps to show how species composition and the bathymetric distribution and abundance of each species changed in relation to the distribution of water masses and currents. Also considered are variations in the distribution patterns and densities of chaetognath species with respect to seasonal changes. Areas analyzed for seasonal variations are as follows: epipelagic zone of the southwest Atlantic from 55°S to 64°S, 65°W to 22°W during the summer and fall; mesopelagic zone of the southwest Atlantic from 59°S to 64°S, 55°W to 28°W during the summer and fall; epipelagic and mesopelagic zones in the Antarctic region of the South Pacific from 130°W to 90°W during all four seasons, and the bathypelagic zone during the spring, fall and winter; and epipelagic zone in the Subantarctic region of the South Pacific from 150°W to 120°W during the spring and winter. Two major regions of a southward flow of warm central Pacific waters into cold Subantarctic waters are indicated by the presence of typical Subtropical species (K. subtilis, P. draco, S. bipunctata, S. hexaptera, and S. minima) in Subantarctic regions. These two regions are the Subtropical Convergence region of the central South Pacific from 150°W to 125°W and off the coast of Chile from 95°W to 83°W. A narrow, northward, cold-water flow was found in the Subtropical Convergence region at 140°W in the upper 200 m depth. This flow is indicated by the absence of typical Subtropical species and the presence of the Subantarctic species S. gazellae and S. tasmanica. Major upwelling regions are indicated by the presence of typical meso-bathypelagic species (E. bathypelagica, E. fowleri, S. decipiens, S. macrocephala, S. marri, S. maxima, S. planctonis, and S. zetesios) in the epipelagic layers. Zones of upwelling with respect to each season are discussed.