AMLR 2004 Weekly Reports No. 1 and 2
2. Due to the risk of damage by icebergs, only one out of
three instrumented buoys was deployed along the western edge of the submarine
canyon immediately to the east of
3. Provisions, mail and personnel (W. Trivelpiece and D. Krause, SWFSC, and D. Torres N. and D.
Torres C., Chilean Antarctic Institute) were transferred to the
4. Ship transited to
5. On 16 Jan a survey of bio-oceanographic conditions in the
vicinity of the
6. Krill, salps and other zooplankton. Plankton samples have been processed from 11 West Area samples. Modest numbers of Antarctic krill (Euphausia superba) were present in most of these samples with a total catch of nearly 500 individuals. Lengths generally ranged from 35 to 50 mm with median and modal lengths of 42 mm. These represent 2 and 3 year old krill resulting from the successful 2000-2001 and 2001-2002 year classes. The presence of a few spent females and infrequent larvae indicate that some spawning has taken place but the majority of mature females either have not yet mated or are in the early stages of ovarian development. The salp Salpa thompsoni, amphipod Thysanoessamacrura and copepods (Calanoidesacutus and Calanuspropinquus) have numerically dominated the catches. Presence of large numbers of the high latitude salp Ilhearacovitzai at one station north of Livingston Island suggests the influence of Weddell Sea water in the West area.
7. Krill biomass and dispersion. Mean krill biomass densities along the first 4 transects in the West Area ranged from 21 to 47 g m-2, comparable to densities observed in this area last year. Krill were mapped along all transects with highest densities (over 2 kg m-2) near the shelf break north of Livingston Island.
8. Phytoplankton. In conjunction with NSF Office of Polar Programs and the “Global Drifter Program” (NOAA), AMLR is conducting a study of surface currents in the study area and the influence of the Shackleton Fraction Zone (north of ElephantIsland) on the Antarctic Circumpolar Current in the Drake Passage. During the southbound transect from Punta Arenas, Chile, the first four of 20 drifter buoys to be released this month were deployed. Too few stations have been completed at this time to allow a description of phytoplankton biomass. In cooperation with D. Stramski and B.G. Mitchell (Scripps Institution of Oceanography), an integrated optics package (consisting of AC-9, Hydroscat, 2 aBetas, fluorometer, two transmissometers, PAR sensor, and CTD) has been successfully deployed. Also a free-fall Biospherical PRR-600 to measure upwelling and downwelling light spectra will be deployed, but rough seas for the past two days have so far prevented this from happening.
9. Oceanography and meteorology. A well-defined Antarctic Polar Front was observed during the southbound transit at 58ēS with the sea surface temperature dropping from 5.45ēC to 2.71ēC and a corresponding decrease in salinity. A sharp drop in atmospheric pressure (as low as 963 mb), at the beginning of the week (12 Jan) and towards the end of the week (17 Jan), was accompanied by strong northwesterly winds, averaging around 35-40 kt, gusting to 55-60 kt. After crossing the APF the air temperature dropped from 6ēC to a week average of approximately 1ēC. Too few stations have been completed at this time to allow a description of oceanographic conditions.
10. Predator diet studies. 4 Antarctic fur seal scats have been processed to date from collections at Cape Shirreff all containing krill. None of these scats contained squid beaks or otoliths.100 live krill have been sexed and measured for total length, carapace length and width analysis to determine if current regression equations are accurate. 12 milk samples have been processed for lipid extraction. Samples processed are being stored either as frozen or in scintillation vials.
11. Bird and marine mammal observations. 34 species of seabirds have been observed since 11 Jan, when we entered the Drake Passage area. Since entering the study area, we have conducted approximately 51 hours of underway observations. Unusual species observed include Westland petrel, gray-backed storm-petrel, and Arctic tern. Blue petrels and Antarctic prions were highly conspicuous in the offshore waters of the West Area. The following marine mammals have been observed during the course of our surveys in order of abundance: cetaceans: humpback, minke, fin, and southern bottlenose whales; pinnipeds: Antarctic fur seal. The primary area of concentration of humpback whales (n=35, group sizes: 1-8) occurred ~25 km N of Cape Shirreff, Livingston Island. Since 14 Jan, Antarctic fur seals (n=21, group sizes: 1-6) have been observed in offshore areas north of Livingston Island only. In addition, 3 killer whales and a leopard seal were observed in Admiralty Bay.
12. Scientific party aboard includes:
R. Hewitt, SWFSC, chief scientist
A. Cossio, SWFSC, acoustics
V. Loeb, Moss Landing Marine Labs, zooplankton
A. Jenkins, SWFSC, small boats, zooplankton
R. Rowley, MLML, small boats, zooplankton
J. Reum, UCSC, zooplankton
M. Force, SWFSC, zooplankton, bird and marine mammal obs.
K. Chambers, SWFSC, zooplankton
S. Sessions, SWFSC, zooplankton
J. Warren,SouthamptonCollege, inshore survey and zooplankton
E. Daniels, MLML, zooplankton
D. Needham, STS, Cape Town, oceanography, ET support
M. Van Den Berg, STS, Cape Town, oceanography, ET support
C. Hewes, SIO, phytoplankton
D. Allison, SIO, phytoplankton
J. Ryan, SIO, phytoplankton
J. Lipsky, SWFSC, lipid extractions and scat analysis
J. Santora, CUNY, bird and marine mammal observations
A. Bernick, CUNY, bird and marine mammal observations
S. Corsolini, University of Siena, Italy
Submitted by R. Hewitt