R.J. Baldwin

Spatial and temporal variation in the abundance, distribution and population structure of epibenthic megafauna in Port Foster, Deception Island

Abundance and spatial distribution of epibenthic megafauna were examined at Port Foster, Deception Island, five times between March 1999 and November 2000. Camera sled surveys and bottom trawls were used to identify and collect specimens, and camera sled photographs also were used to determine abundances and spatial distributions for each species. The ophiuroid Ophionotus victoriae, the regular echinoid Sterechinus neumayeri, and one or more species of Porifera were the most abundant taxa during this sampling period. Abundances of O. victoriae varied throughout the annual cycle, peaking in June 2000, and were correlated positively with sedimentation rates. In contrast, abundances of S. neumayeri were consistent throughout the sampling period, except for a peak in June 2000, during austral winter. Peak abundances for both species coincided with a large number of small individuals, indicating apparent recruitment events for O. victoriae and S. neumayeri during this time period. Poriferans, as a group, had statistically similar abundances during each sampling period. Low-abundance species tended to be aggregated on both small and large spatial scales, their distributions probably influenced by reproductive method, gregarious settlement, and food availability. The spatial distribution of S. neumayeri in June 2000 and O. victoriae was random across multiple spatial scales, perhaps in response to food availability and broad environmental tolerances, respectively.

Effects of seasonal pack ice on the distribution of macrozooplankton and micronekton in the northwestern Weddell Sea

The presence of mesopelagic organisms in the guts of surface-foraging seabirds feeding in open areas within seasonal pack ice in the Antarctic has given rise to questions regarding the effects of pack ice on the underlying mesopelagic community. Bottom-moored free-vehicle acoustic instruments were used in concert with midwater trawls and baited traps to examine the abundance, size distribution and vertical distribution of pelagic organisms in the uppermost 100 m of the water column during the austral spring of 1992 in two areas of the northwestern Weddell Sea, one covered by seasonal pack icc and the other free of ice cover. Acoustic largets were more abundant and significantly larger at the open-water station than beneath pack ice. However, targets at the ice-covered site exhibited a pronounced diel pattern, with the largest targets detected only at night. Samples from night trawls at the icecovered site contained several species of large, vertically-migrating mesopelagic fishes, whereas these species were absent from trawls taken during the day. In addition, baited traps deployed in pack ice just beneath the ice-water interface collected large numbers of scavenging lysianassoid amphipods, while deeper traps beneath the ice and traps at the open-water station were empty, indicating the presence of a scavenging community associated with the undersurface of the ice. These results sapport the idea that mesopelagic organisms migrate closer to the surface beneath pack ice than in open water, exposing them to possible predation by surface-foraging seabirds.

Abyssopelagic fauna in the central North Pacific: comparison of acoustic detection and trawl and baited trap collections to 5800 m

Abstract An integrated study using an acoustic array, opening-closing trawl and baited traps was conducted at an abyssal station in the central North Pacific (31°N, 159°W) to further characterize the near-bottom community. Two split-beam line arrays with beam patterns narrow in the vertical and omnidirectional in the horizontal were moored at 100 and 600 m above bottom (mab), sampling an insonified volume of 7855 m 3 each. In addition, a multiple opening-closing trawl (10 m 2 mouth opening) and baited traps were used to sample the fauna up to 1800 mab. Fourteen deployments of the acoustic arrays during two cruises detected 26 targets, with twice as many at 100 mab as at 600 mab (2.10 vs 0.97 targets h −1 ). Backscatter strengths for acoustic targets ranged from −57.2 to −26.8 dB. A total of 31 species, at least eight previously undescribed, were identified from trawl and trap collections within 1800 m of the sea floor. Of these new species, four of the decapod genus Hymenodora and one eel, Monognathus rosenblatti , were the most abundant animals collected by trawl. Other species commonly collected in baited traps included Acanthephyra quadrispinosa (Crustacea, Decapoda), Eurythenes gryllus (Crustacea, Amphipoda), and Coryphaenoides yaquinae (Osteichthyes, Macrouridae). Acoustic target abundances ranged from 0 to 1.6 animals per 10 5 m 3 per deployment, while values measured with the trawl ranged from 1.4 to 11.9 animals per 10 5 m 3 . Biomass of the acoustic targets, estimated using a tentative identification based on size, and a series of regressions based on target strength and animal length and weight, ranged from 0 to 72.3 g wet weight per 10 5 m 3 . Biomass estimates from the trawl samples ranged from 0.2 to 6.7 g wet weight per 10 5 m 3 . The large number of new species collected during this study and the variability in sampling sparse populations using three different sampling techniques illustrate how little we know about the abyssopelagic community.

Ecosystem studies at Deception Island, Antarctica: an overview

The Southern Ocean represents one of the most extreme marine environments on Earth, characterized by low temperature throughout the water column and extensive seasonal ice cover resulting in high temporal variability in primary production (Smith and Nelson, 1986; Arrigo et al., 1997). This fluctuating production of organic matter heavily impacts the marine ecosystem. Ship-based measurements and observations during all seasons of the year have provided a description of ecosystems encompassing surface to benthic communities (Ainley et al., 1991; Lancraft et al., 1991; Siegel et al., 1992; Hopkins et al., 1993; Grebmeier and Barry, 1991; Knox, 1994). However, seasonal ice cover has impeded year-round studies of how these ecosystems function, especially under such extreme conditions. Long time-series studies are critical in understanding processes affecting marine ecosystems on seasonal and annual time scales (Austen et al., 1991; Brodeur and Ware, 1992; Deuser et al., 1995). Such studies are especially important in geographic regions, such as the Southern Ocean, that experience high annual variability in physically and/or chemically mediated processes (e.g., Franklin, 1989). In situ long-term monitoring has been employed successfully in the Southern Ocean to document extreme temporal variability in the sinking of particulate matter (e.g., Collier et al., 2000). Much of this variability appears related to seasonal ice cover and the production of organic matter in the surface waters of both open-ocean (Wefer et al., 1988; Fischer et al., 1988; Wefer and Fischer, 1991) and shelf (Fukuchi et al., 1988; Dunbar et al., 1989, 1998; DeMaster et al., 1992) environments. A study of the marine ecosystem associated with Port Foster, Deception Island, in the South Shetland Islands, Antarctica (Fig. 1), was undertaken with the intent of utilizing a long time-series approach to monitoring the unique marine communities in this polar environment throughout an annual cycle. Such long time-series studies are essential to understanding the impact of global warming in these highly temperature-sensitive environments. Evidence is now accumulating that the Antarctic Peninsula area has warmed over the past half century by as much as 2.5 C along the western coastline (Vaughan and Doake, 1996; Vaughan et al., 2001). Warming in the Antarctic Peninsula region, including the South Shetland and South Orkney Islands, has been related to changes in marine populations ranging from predators such as penguins (Fraser et al., 1992) seals and albatross to prey such as krill (Reid and Croxall, 2001). Port Foster, the sunken, seawater flooded caldera of Deception Island, was chosen for our studies because of its proximity to Antarctic stations located within the South Shetland Islands and along the northwestern side of the Antarctic Peninsula (Fig. 1) where long time-series climate and marine community data have been collected for decades. Deception Island is also the site of several scientific stations occupied by British, Chilean, Argentine and Spanish contingents since the mid-1930s. This island also afforded a unique opportunity to work in a semi-enclosed environment that could be monitored effectively with long-term instrumentation while being free from ARTICLE IN PRESS

9 Laboratory and in Situ Methods for Studying Deep-Sea Fishes

Publisher Summary This chapter discusses the laboratory and in situ methods for studying deep-sea fishes. Laboratory studies of living, deep-sea fishes require their capture, recovery, and maintenance. Two primary factors influencing the physiological condition of deep-sea fishes collected for laboratory studies are increasing temperature and decompression. Thermally insulated cod ends have been successfully developed and used on a variety of opening–closing midwater trawls and epibenthic sleds to collect and recover living bathypelagic animals for metabolic studies in shipboard laboratories. Temperature-insulated traps also have been employed for collecting scavenging deep-sea fishes. Such traps have been either attached to long pull lines extending to depth from the surface or configured as free vehicles. Free-vehicle acoustic monitoring systems have been developed to study the abundance, movements, and behavior of bathypelagic animals using noninvasive active sonar. The prototypes of these vertically profiling acoustic arrays with single transducers have now been successfully used to study nekton over a seamount and under the Antarctic pack ice.

Long time-series monitoring of the ecosystem at Deception Island, Antarctica: description of instrumentation

A description of the oceanographic instrumentation developed and deployed at Deception Island, Antarctica during the period 9 March 1999 to 20 November 2000 as part of the ERUPT program is presented. This instrumentation includes (1) an autonomous weather station (Terrestrial station) to record daily conditions and ice-cover, (2) an underwater time-lapse camera/sediment trap array to photograph the abundance and movements of bottom-dwelling animals and collect sinking particulate matter, (3) an acoustic array to monitor movements of macrozooplankton and nekton, (4) an autonomous, vertically profiling pump sampler to capture and preserve plankton and nekton from discrete depths, (5) thermistor arrays to record water temperature at various depths, (6) an acoustic Doppler profiler to record current velocities at discrete depths, and (7) a piston-operated grab respirometer to measure sediment community oxygen consumption and recover sediments. The Terrestrial station and thermistor arrays, current meter and grab respirometer were the most successful instruments deployed, producing large data sets. The acoustic array produced some data of limited value, while the camera tripod and pump sampler produced no useful data due to technical and operational problems.