TABLE 1
Reproduction days - months 1 - 10 km (H)
1000 m (100 m resolution)
Migration (H) days - weeks 10 - 100 km
Migration (V) hours - seasonal 300 m
Swarming hours - weeks 10 m - 10 km
Mortality
a) "natural" weeks microscale - gyre scale
b) predation seconds - months
Growth days - weeks
Life cycle 2 - 3 years gyre scale
(hatch - Hatch)
*Note: Sample to 1000 m for copepods
The quasi-synoptic survey cruises should take place at approximately monthly intervals for a minimum period of three years, in order to resolve the full life cycle of E. superba and other key species. These cruises should encompass shelf, slope and oceanic environments (Fig. 1), with the aim of resolving mesoscale features in both the biotic and dynamic physical environments.
Process cruises should focus on the processes and mechanisms identified above, and should be directed on a phenomenological basis from information arising from results of the survey cruises.
Remote sensing aspects of the program should incorporate new and existing technologies capable of yielding synoptic data over long time scales.
In general, the working group recommends that this project could feasibly begin by 1996-97. It would involve multiple ships from different nations, and would require that a common quasi-synoptic survey grid be occupied at different times by all participants.
It was noted that sampling strategies may differ depending upon the
species being investigated. For example, while the 200 m depth horizon may
be adequate for a study of juvenile and adult krill, the 1000 m depth
horizon may be more appropriate for copepods and early larval stages of
krill.
7.2 Benthic Working Group Report
A. Criteria for Selection
Five characteristics were identified as criteria for selection of target species, including:
Three groups of benthie fauna were selected as potential target species. Examples are presented for each, inclusive of both wide ranging species with pelagic (p) larvae and restricted fauna, often characterized by brooders (b).
The reproductive success of Southern Ocean birds and seals has been shown to depend on interannual variations in prey abundance (Croxall et al., 1988); their long term fluctuations in abundance have been related to changing sea ice conditions (Fraser et al., in press). Therefore these higher predators are especially valuable to a program designed to detect the biological effects of global warming.
There are other practical reasons for their inclusion. Birds and seals can be more easily and inexpensively surveyed than other pelagic animals. While foraging, they perform spatially and temporally integrated "sampling regime" over a substantial area. Lengthy time series already exist on the reproduction and abundance of several of the numerically dominant species (e.g. Adélie and chinstrap penguins, fur and crabeater seals) in various locales (Palmer Station, King George Island, Signy Island and South Georgia). Furthermore, the recently established CCAMLR Ecosystem Monitoring Program (CEMP) which involves studies on selected bird and seal species. The results of this program have direct relevance to GLOBEC. Studies focused on fishes and higher predators will provide information on the relationships between predator-prey and their environment which is critical to understanding variability in the Southern Ocean ecosystem. Such studies may also provide the bases for monitoring the effects of man-induced perturbations.
The group agreed that in order to detect changes in fish and higher
predators induced by climatic change it is essential to establish long term
base line monitoring. These studies are dependent on having good information
from field studies and modeling exercises identifying critical processes.
7.3.2 Site selection
We suggest that the Atlantic sector, including the Antarctic Peninsula,
South Georgia and the South Orkney Islands, is the most appropriate study
region because of its known sensitivity to variation in the Antarctic
Circumpolar Current and its existing historical data bases. Within this
area, the Weddell and Bellinghausen Seas are considered important and
contrasting sea ice zones worthy of study; South Georgia is an open water
area with considerable commercial fishing activity (krill and finfish), a
historical data base and ongoing monitoring programs; the South Orkneys are
within the Weddell-Scotia Confluence and experience commercial fishery
activity (especially summertime krill harvesting). The wide latitudinal
range was felt to be important for assessing larger scale ecological changes
which would be associated with climate change.
7.3.3 Target species
We have selected a relatively long list of target species with the
justification that ecological changes among groups of species across the
broad study area are more likely to reveal compelling evidence of
climatically related change. The target fish species all have broad
distributional ranges and represent commercially harvested forms, abundant
non-harvested holopelagic forms and accessible shallow water species.
The target penguin and seabird species are primarily krill predators
considered important by CEMP: Adélie, chinstrap, macaroni and gentoo
penguins; cape and Antarctic petrels; Black browed albatross. Because of
their different feeding activities we also feel it would be useful to
include the grey headed albatross (fish and squid prey) and South Polar skua
(which feeds on Pleuragramma antarctica ) as target species. The mammalian
target species are crabeater and Antarctic fur seals. Both are dependent on
krill, but occupy different habitats analogous to those of Adélie and
chinstrap penguins.
7.3.4 Definable populations
We are uncertain whether various populations can be distinguished at the
present time. The CCAMLR subareas under consideration are felt to be
reasonable management units for the commercial fish species. Some bird and
seal species show distributional differences which may represent distinct
populations. For these species populations could probably be distinguished
using mitochondrial DNA or other molecular techniques.
7.3.5 Population dynamics
The commercial fish stocks are monitored and analyzed annually by CCAMLR and
cohort analyses have been performed on the South Georgia stocks. Through
traditional fishcries techniques, spawning stock biomass for these and the
other finfishes can be established through ongoing base line studies of
growth and reproduction. Continuing national and CEMP bird and seal programs
are monitoring growth rates, breeding success and cohort survival.
7.3.6 Focus on processes and mechanisms
Included are studies providing data important for understanding population
dynamics relative to direct and indirect effects of environmental change.
Direct effects include:
Fraser, W. R., W. Z. Trivelpiece, D. G. Ainley and S. G. Trivelpiece. Increases in Antarctic penguin populations: Reduced competition with whales or a loss of sea ice due to environmental warming. Polar Biology, in press.
Laws, R.M. 1985. The ecology of the Southern Ocean. Am. Sci.
73, 26-40.
7.4 Physics/Climate Working Group Report
The accuracy of present climate predictions is limited by the relatively coarse (300 km grid) atmospheric and oceanic models used for climate research. However, the models indicate that in sea-ice regions the increase in summer temperatures will be substantially smaller than the global mean. Global warming will be delayed over the oceans with the greatest delay occurring in the Antarctic Ocean, just south of the belt of minimum westerlies.
The present models predict a reduced temperature contrast in the atmosphere between the equator and the poles. This will result in a reduced strength of the westerlies and a corresponding change in the strength of the Antarctic Circumpolar Current.
Finally, the models predict increases in the cloudiness of the atmosphere
(resulting from increased evaporation). As the Southern Ocean is cloud
covered, typically 80% of the time, even small increases in cloud cover
could result in large changes in the biological productivity of the region.
7.4.3 Large-scale system
The large scale structure of the circulation in the Southern Ocean is
controlled largely by the surface wind stress and the shape of the ocean
bottom. The wind stress, in general terms, controls the strength (total
transport) of the Antarctic Circumpolar Current. The bathymetry, on the
other hand, controls the location of the current. In particular, the ACC is
constrained to flow through Drake Passage, north of the Kerguelen Plateau,
south of the Campbell Plateau and through the Eltanin Fracture in the East
Pacific Rise. These gateways for the ACC determine its path through the
Southern Ocean. The location of the atmospheric Westedies would have to
shift by ten or more degrees of latitude in order to have any major effect
on the structure of the circulation in the Southern Ocean.
The polar gyres near the Antarctic Continent may be differrent from the large-scale structure. The location of the Weddell gyre is strongly influenced by the Antarctic Peninsula. The other, suspected, gyres (e.g. in the Ross Sea) may become much more evident if the Easterlies along the continent became stronger. These gyres might also extend farther into the Southern Ocean if the winds were to change.
Within the large scale, Antarctic Circumpolar Current, there are narrow (about 50 km in width) high speed current jets that are associated with density fronts. These jets are separated by relatively low speed zones of about 100km width. A study of surface drifters shows that these fronts are associated with a secondary circulation that leads to flow convergence at the surface (surface drifters tend to collect over the fronts). The strength and importance of this secondary circulation has not been investigated nor has its effect on biological processes.
The high speed, narrow currents in the ACC are subject to flow instability which leads to mesoscale eddies. This eddy variability is evident in satellite altimetric observations, specifically in the measures of the time variation of the height of the sea surface. In fact, the ACC stands out in the Southern Ocean as a band of large flow variation. There is also measureable flow variation near the Antarctic Continent but it is not clear how much of this is due to the presence of ice.
Within the band of high variability associated with the ACC, areas of even higher variations exist. The largest magnitude of the eddy kinetic energy occurs in the Agulhas Retroflection and near the collision of the Brazil Current and the Falkland Current. Lesser hot spots are over the Kerguelen Plateau, the Macquarie Ridge, the Campbell Plateau, the East Pacific Rise and the Scotia Arc. The implication of this observation is that mesoscale variability is driven to some extent by the interaction of flow in the Southern Ocean (which penetrates to the bottom with only slightly diminished speed) with relatively shallow (less than 1 km) parts of the Southern Ocean.
A comparison of phytoplankton maps from CZCS and bathymetry reveals a
striking necessary condition: high phytoplankton occurs in regions of large
bottom slope. However, not every region of strong bottom slope is associated
with high phytoplankton concentrations. Some of the regions of high
phytoplankton are also areas of high flow variability, but not all. The
relationship among flow variability, bathymetry and high phytoplankton
concentration is not clear at this time.
7.4.4 Sea-ice region
Sea ice in Antarctica is one of the most seasonal parameters on the surface
of the earth. In winter, it is a very extensive habitat, covering an area
about 20 x 106 km2 and a large percentage of the Southern Ocean south of
50 S. In summer, only 20% of the winter ice cover remains. The immediate
effect of the large seasonality is to cause seasonal modifications in the
vertical structure of the underlying ocean. During growth, in fall and
winter (about 9 months), the formation of ice causes the ejection of salt
thereby decreasing stability of the mixed layer. During spring and summer,
the retreat of the ice causes the introduction of large amounts of low
salinity melt water to the surface providing vertical stability in the
water column. It has been postulated that the presence of melt water is a
key factor leading to phytoplankton blooms near ice edges. Melt water provides
vertical stability in the water column and allows phytoplankton to grow in
high-light high-nutrient environments.
During winter, the presence of leads and polynyas are also significant factors affecting the environment. Their presence is known to cause a considerable change in heat fluxes between the ocean and the atmosphere and salinity fluxes between the ice and ocean. Leads are linear and random features of open water (or new ice) in the ice pack and are known to constitute less than 10% of the ice cover. Polynyas are more rounded features and have been classified as either sensible heat polynyas or latent heat polynyas. The sensible heat polynyas which are usually in the deep ocean and can cover large areas are believed to be caused primarily by upwelling over topographical features (e.g. the Maud Rise). Latent heat polynyas are usually located along the coast and are formed by katabatic (or synoptic) winds. Biological populations have been observed to be considerably enhanced in lead and polynya regions. A careful monitoring of these features is therefore important.
Consistent records of ice extent from satellite observations have
indicated no significant change in ice cover during the past seventeen
years. However, there have been large regional variations. Large polynyas in
1974 through 1976 were observed in the Weddell Sea, but not in other
regions. In 1980, the ice cover in the Weddell Sea was 15% larger than
normal. This was compensated by smaller than average sea ice extents in
other regions such as the Ross Sea and the Indian Ocean during this
period. Long term effects of global warming would reduce the seasonality of
sea ice and perhaps result in the eventual absence of summer ice. However,
on the short term, the effect is not too obvious because of the complex feed
backs that exist between ice, ocean, and the atmosphere.
7.4.5 Coastal circulation
Much of the physical oceanography research that had been done in the
Antarctic has focused on the processes associated with the large-scale flow
of the Antarctic Circumpolar Current or on processes that contribute to
bottom water formation. With few exceptions, the regional and coastal
circulation of the Antarctic has been ignored.
The historical hydrographic and current measurements that exist for the Antarctic are primarily concentrated in the Bransfield Strait-South Shetland Island region. These data reveal that the coastal flow in this region consists of complex circulation patterns that exhibit seasonal variability in strength and direction, in response to changes in wind stress and ice cover. The coastal currents are relatively narrow, being on the order of a few kilometers in width, but having large horizontal extent. For example the narrow westward flowing current on the north of the South Shetland Islands is thought to be circumpolar in nature. The coastal currents are influenced by bottom topography and coastal geometry, which can result in small scale variability.
Coastal regions such as the Bransfield Strait are areas where different water masses meet. This results in the formation of small scale frontal regions that can and do exhibit considerable variability in space and time. It is also likely that coastal flows are influenced by the amount of melt water from ice shelves and glaciers that is introduced each year.
Climate change effects could potentially affect the coastal circulation in
the Antarctic through such processes as reduced inputs of melt water and/or
changes in solar radiation. Either of these processes could alter water
column stability, which would affect the intensity of veritcal mixing in
coastal regions. Also, changes in the wind stress field would alter the
intensity of the seasonal surface circulation.
7.4.6 Recommendations
The Working Group recommended that:
There is a need for assembly and analysis of historical information. In
particular the observations from shore-based stations in the Antarctic
should be put into a standard format and made available. Such data sets
would help in filling in the lack of long term observations of environmental
parameters in the Antarctic.
Understanding the processes associated with sea-ice extent and variability are an important part of determining what (if any) effect climate change will have on the Antarctic.
Understanding of coastal circulation is a necessary component of addressing questions that relate to marine population fluctuations. Many species, such as krill, spawn on or near the continental shelf where their larval forms are dispersed by the coastal currents. Thus, understanding the factors that result in the successful recruitment of these species requires first a knowledge of the coastal current systems. The existence of shore-based laboratories makes coastal programs logistically feasible for the Antarctic.
There is a need for consistent and synoptic observations of sea ice and
currents in the Antarctic. Attention should focus on designing measurement
programs that use satellites, moored instrumentation and drifters.
7.5 Modeling Working Group Report
The present models do not realistically predict the ridging of sea ice or
the formation of caverns by the rating of sea ice. Such models need
development. The present models also do not attempt to describe the details
of the flow field below the sea ice. However, this may be possible using a
general circulation model with high resolution in the top 200 m.
7.5.2.5 Models for recruitment
There is a critical need to use Lagrangian calculations to look at the
dispersal of holoplanktonic species and the planktonic stages of benthic,
micronektonic, and nektonic species. This requires proper circulation models
and also measurements of growth and the migration pattern. These
calculations are relatively inexpensive and yield considerable insight on
the dispersal and distribution of the species.
7.5.3 Recommendations
A. Considered GLOBEC Report Number 3 "Biotechnology Applications to Field Studies of Zooplankton" very important in regard to the need to investigate the following:
B. Determinations need to reflect different time intervals in the physiology of the animal, i.e., long term versus short term changes in the state of the animal.
C. Need to consider all of the approaches in Report Number 3 and work toward
II. Seasonal studies need to be emphasized regarding
A. Environmental triggers of behavioral and metabolic events - in polar environments very small changes (i.e. 0.5 degrees C) may trigger change.
B. Comparisons of metabolic responses between extremes in the environment, e.g. summer versus winter. Most organisms investigated show seasonal cycles in metabolic activity.
C. May need new resources for station/ocean work throughout the year.
III. Physiological "plasticity" needs to be considered, especially to understand the capacity of antarctic animals to respond to environmental change (new to antarctic work)
A. Need detailed laboratory experiments to interpret simpler shipboard measurements in the context of an animal's metabolic history and consequences to its future.
B. Need to measure physiological responses by the target organism to conditions outside the normal environmental range normally encountered.
E. Important to explore the idea of the ability of Antarctic species to procrastinate a physiological decision, especially whether it is a generality for Antarctic species
IV. Additional specific questions
A. Krill and salps do not generally occur together. Is this separation in part due to physiological differences between the two species, or primarily due to physical conditions in the environment?
B. What physiological parameters should be measured during the life cycle or at specific stages of the target organism that would most likely be an index of processes affecting population dynamics?
V. Target species
A. Attention should be given to not only studying a few species in detail, but also to studying a greater number of species in less detail.
The complexity of the benthos is greater than the planktonic community. For the benthos site selection should consider historical long term records, logistical constraints, and high and low latitude sites. The Ross Sea, McMurdo Sound and the South Orkney Islands should be considered possible sites. In the context of climate change the persistence of the benthic structure, the long term faunal and sediment record, and the ecological community structure should be considered. Some of the criteria for selection of target species shotrid be their abundance, whether they have a wide or restricted distribution, and whether measurable growth parameters exist.
The group discussed the merits of looking at a few species in detail or many species in less detail. The detailed approach was favored, but with a note that a broader range of species needs investigation at some level. For the detailed approach we need to consider how an organism responds to different carbon inputs, determine the physiological state of the organism and have the laboratory data to understand the implications. Ground truthing of physiological measurements and how different environmental variables affect the physiology of an organism is essential if we are to use these measures as assessments of the physiological state of an organism in the field (Fig. 1). Possible measurements included metabolic rate, growth, and (particularly for larvae) enzyme activity, amount of total protein and the pattern of synthesis of specific proteins. Concern was expressed about whether techniques were too sophisticated for field use and that they would not be something that "everyone" could do. Citrate synthase activity was suggested as an example of a useful and appropriate assay since the assay is simple, material needs to be frozen only at -80 deg C, and citrase synthase is thought to be a good index of metabolism.
It may also be useful to better understand an organism's maximum potential versus what we actually see in the field. Growth rates would be a good example. Another question mentioned was how do we relate physiology to birth and death rates? or How do we relate physiological status to light, temperature, salinity and other abiotic factors? What followed was a general discussion of what to measure. Krill in Prydz Bay experience a constant low temperature compared to those west of the Antarctic Peninsula that encounter a 4-5 deg C range in temperature. The same species from different areas may show different physiological responses that may make "physiological state" difficult to interpret. It was mentioned again that growth was a good integrator of recent past environmental events. A combination of the biochemical and physiological approaches may be most suitable for GLOBEC. However, we need to be aware of potential problems. One example mentioned was the contribution of enzymatic activity from bacterial enzymes in krill stomachs to any analysis of krill.
Physiological rates should be evaluated in terms of their relevance to
population dynamics. In addition, the relative importance of stages to
measure since the work load may need to be prioritized. It was also
emphasized that there should be a thorough review about what we know of
particular species important to the study, and a critical evaluation of
past research.
7.7 Population Dynamics Working Group Report
The potential study areas were the Bellingshausen Sea and adjacent waters to
the east, but it was felt that because of logistic constraints of national
ongoing and planned projects, other areas such as the Weddell Sea or Prydz
Bay should be taken into consideration. These may also be utilized to look
at a given target species under different latitudinal regimes, or the
shipborne work in the primary study areas may be complemented by shore-based
studies in different regions on e.g. rates and processes. In general, the
group acknowledged that the most striking andimportant gap is the lack of
data from the winter months for all taxonomic and ecological groups.
7.7.1 Benthos
Shipborne sampling periods are limited to the austral summer months. This
may be improved by the use of ice-strengthened research vessels, and by
future and present establishment of shore-based research. In analyzing
length frequency data, the apparent longevity of many benthic organisms may
obscure patterns that are useful for age and growth estimated. An apparent
feature with respect to early life history seems to be the decrease of
species having meroplanktic larvae 1) with latitude, and 2) with bottom
depth. Another feature is the long developmental times of embryos which may
contribute to circumantarctic distribution patterns, but may also be
interpreted as waiting stage for favorable environmental conditions during
larval drift. Field studies indicate that recruitment may be sporadic and
irregular. Colonization should be studied in areas which are exposed after
major ice shelf calving. Similarly, re-colonization and the succession of
species may be studied in areas of high iceberg grounding frequency.
7.7.2 Fish
Although the shortcomings of traditional fishing methods were recognized, it
was understood that there are no new techniques readily available. In recent
years, population dynamics of the commercially harvested species has been
studied in detail. It was agreed that stock assessment should not be the
main objective in the study areas, although there is at present no
commercial fisheries going on. Instead, the existing gaps are the proper
assessment of larval and juvenile growth and developmental rates as related
to biotic and physical environments. Key events in the life history such as
hatching, settlement and first maturity have to be determined.
7.7.3 Zooplankton
The group reiterated the gaps that were identified by the Zooplankton and
Krill WG format I, i.e., the need for both quasi-synoptic demographic
surveys and processoriented cruises. Among particular processes, reference
was made to the processes identified by that group.
7.7.4 Higher level predators
Populations in sea birds can be clearly identified and followed. Marking and
tracking is feasible in sea birds. The bottleneck is apparently the winter
months, especially with respect to foraging dynamics, i.e., food
consumption, distribution relative to prey. Since more than 90% of the bird
biomass consists of penguins, study efforts should focus on these.
Adélie and chinstrap populations in the Antarctic Peninsula area have
shown a decrease and increase in population size, respectively, over the past
40 years, which may well be related to changing degrees of pack-ice
cover. Environmental conditions for these species seem to vary more in the
Weddell Sea than in the Bellingshausen Sea. Some seal species may be
regarded as ecological equivalents of these penguin species, e.g. the
crabeater and fur seals.
7.7.5 Techniques
Standardized techniques have to be agreed upon in order to make comparisons in
space and time possible.
7.7.5.1 Benthos
Both semiquantitative and quantitative sampling gears should be used. The
first includes Agassiz-trawl (4 mm mesh) and video-systems, while
quantitative gear comprise box cores, multiple corers and meiofauna
corers. For the megafauna, video-systems and cameras can be considered as
being quantitative. The minimum mesh size for sieving is 0.5 mm. Aging
methods need to be developed, such as the use of hard parts in sea urchins
or appendices in crustaceans, and these estimates need to be
validated. Rearing experiments have not shown to hold great potential for
this due to the lack of growth in some species in captivity.
7.7.5.2 Zooplankton
A continuous recording device is the Optical Plankton Counter (OPC) which is
towed at 8-10 knots with a depth range of 300-0 m, and which is now
commercially available. Net sampling has to be vertically stratified down to
2000 m with desirable free scale sampling within strata of 100 m. Multiple
opening-closing nets should be used with mesh sizes around 250 um. These may
be complemented by acoustic doppler systems and moorings. Under ice studies
may be performed by SCUBA diving or hand operated horizontal tows through
holes in ice floes or fast ice.
7.7.5.3 Fish
Early life stages should be obtained with the RMT 1+8, but also the
international young cod net was recommended. For adult fish, standard
100-300 feet bottom trawls, and benthopelagic, high fishing nets should be
used. Rearing experiments provide insights into the capacity of otoliths as
recorders of past growth and environmental histories of fish.
7.7.5.4 Higher level predators
The techniques used are internationally standardized (CCAMLR). All data are
considered quantitative. Tracking devices should be developed and
utilized. Studies of the microstructure of seal teeth have revealed
important insights into foraging patterns and success of fur seals,
providing indicators of unfavorable conditions and environmental
disturbances. Similar techniques should be tested for possible application
in other seal species.
7.8 New Technology Working Group Report
Recommendation: aircraft logistic support for operations coupled with real time satellite data would be necessary. Satellite receiving stations capable of collecting such data either on ship or on adjacent bases would be necessary.
b) Local weather and sea surface conditions: data such as wind speed/direction are available from WOCE meteorological buoys in addition to local and large scale surface circulation.
Recommendation: there should be close coordination between GLOBEC and WOCE concerning meteorological and physical oceanographic data for study areas.
Table 1: Summary of technologies now available (*), under development (**), or desirable but requiring development (***), for Southern Ocean GLOBEC investigations.
SENSOR INSTRUMENTATION DEPLOYMENT PLATFORMS
Mobile survey cruises
Acoustics Low-frequency acoustic array, towed
for school detection or tracking**
Multi-frequency surface acoustics towed body, hull mounted
(existing), dual-, split-beam* (**)
Multi-frequency remote acoustics multiple nets, towed bodies
(prototype), dual-, split-beam** and vechicles
Acoustic Doppler Current Profiler hull mounted
(ADCP)*
Optics Optical particle counter** nets and towed bodies
Video camera systems* (**) towed bodies, vehicles and
benthic sledges
Sampling Automated sample processing multiple and high-speed trawls
Process oriented cruises
Acoustics Acoustic volume imaging systems** ROV's, profilers,submersibles
Side-scan sonar (others from above)*
Optics TV and still cameras, still* and Profilers, ROV's, divers
Fixed location experiments
Acoustics Low-frequency acoustic array**
Acoustic volume imaging**
Acoustic transponder and receiving
arrays for predator-prey studies**
Optics Micro video cameras for predator-
prey studies (High definition)*(**)
Moorings
Acoustics Multi-frequency acoustics*(**) vertical profiling arrays
ADCP's*(**)
Optics Longterm cameras* and videos cameras such as Bathysnap
Sampling Bottom landers for growth and
physiology***
c) Structure of water column: in general it was thought that systems used or
being developed by oceanographers for use in other areas were likely to be
suitable for studies in a Southern Ocean GLOBEC (although see constraints
under 2.a). The Group stressed that it was most important that oceanographic
and biological measurements were coordinated and were measured over the same
scales. Frequently the oceanography was determined at larger scales than
those applicable to biological processes, especially those implicated in the
swarming of krill.Recommendations: physical oceanography for small scale phenomenon - on the scale of meters to centimeters - would need to be accorded high priority. Relevant temporal and spatial scales of study for oceanography, phytoplankton, krill and predator dynamics are discussed in detail in Murray et al. (1988; see especially Fig. 8). A general treatment of scale-related issues for zooplankton is discussed in Marine Zooplankton Colloquium 1 (1988).
d) Bathymetry: An understanding of this is vital because of the effect on currents.
Recommendations: bathymetry of the study region should be well defined with multi-beam echosounders (such as SeaBeam) and side scan sonar.
7.8.2 Ice biology
a) Distribution and abundance of organisms: the presence of ice presents
extra sampling problems in comparison to other areas. Once in the ice, ships
are effectively stationary or cause much disturbance if steaming is
attempted. Therefore remote sensing techniques must be developed
further. Development of remotely operated or autonomous vehicles would allow
under-ice surveys. In addition ice islands and ice-anchored drifting buoys
could be used to provide extra information. Under-ice profiling could be
carded out from moored arrays which could contain instrumentation such as
transmissometers, fluorometers, ADCP, sediment traps, multifrequency
acoustic profiling instruments. It is stressed that deployment of such
equipment under the ice is not a simple case of using techniques and
equipment developed elsewhere due to the remote location of the study sites
and the inaccessbility of the equipment for much of the year. The
development of equipment to make in situ observations on animals living
within the ice was also thought to be necessary.
Recommendation: non-invasive techniques to observe krill and zooplankton distribution, abundance and behavior in both ice-free and ice-covered areas should be accorded high priority (e.g. use of optical holography, multifrequency acoustics, etc.).
Recommnendation: close coordination with the Sea Ice Working Group of SCAR and with SO-JGOFS should be established concerning the biological data for sea ice, under ice and water biota of the Southern Ocean.
b) Physiology: It was felt that equipment capable of making in situ measurements of respiration, growth, etc. would be beneficial for benthic animals and the under-ice environment. It was pointed out that use of captive populations in large tanks (see Price eta/. 1987 for use of such a tank in Canada) or in enclosures in sheltered bays would provide valuable information on behavior and physiology (see Foote et al. 1989 for use of rafts and cages at South Georgia).
Recommendation: large enclosures need to be developed further to simulate natural conditions for physiological studies of krill and other organisms. For example, enclosures in Admiralty Bay could be more cost effective than building large scale laboratory facilities ashore.
7.8.3 Species specific problems
a) Antarctic krill Euphausia superba: krill are frequently found at or
near the sea surface (0-10 m). This depth range is particularly poorly sampled
by nets and acoustics (see for example Everson and Bone, 1986a, on results from
an upwardlooking echo-sounder). Moored upward-looking acoustic arrays could
be capable of distinguishing water movement and acoustic backscatter from
targets in the upper 5-10m in both ice-free and ice-covered areas. The
effect of high sea states on the distribution of krill and other
zooplankton/micronekton in surface waters was discussed. While this creates
problems for all observation techniques it may not be severe because of the
downward migration of animals under these conditions.
Recommendation: instrumentation be improved or developed to examine the upper 10 rn of the water column and the undersurface of the ice.
Many animals and krill in particular have been shown to avoid nets (see for instance Everson and Bone, 1986b). It was agreed that for krill, stealth nets capable of sampling with minimum avoidance at relatively high speed were desirable. The Group recognized the need for the development of non-invasive sampling techniques but stressed that these should be validated at the earliest opportunity. There was good evidence that krill were able to avoid divers, submerged cameras and other "non-invasive" systems.
Recommendation: evaluate avoidance/attraction effects of measuring devices and deployment platforms on krill behavior.
b) Salps: in addition to krill, salps must be adequately studied. Because of the delicate nature of salp aggregates, it is important to use a combination of nets and video systems to quantify them and distinguish aggregation sizes.
Recommendation: improve large volume sampling techniques to determine abundance, biomass and distribution of salps with minimal disturbance to aggregates. It was suggested that a large volume water sampler monitored by video camera for triggering at appropriate times might be developed. It is important that sampling devices for both krill and salps are routinely available to take advantage of the alternate occurrence of these two species.
c) Copepods: the Group did not discuss instrumentation specifically for copepod studies. It is likely that techniques mentioned in the North Atlantic proposal and under-ice biology would form the core of new developments.
7.8.4 Data management
The Group recognized that this was not the best forum to discuss data
management but that a number of points should be highlighted at this
time. Timely interchange of data, data access, data entry protocols and
validation were all areas that could cause problems. A number of other
international programmes have experience in setting up and administering
databases (e.g. BIOMASS, WOCE).
Recommendation: data management must be considered early in the development of GLOBEC in concert with other existing international programs.
7.8.5 References
Everson, I. and D. G. Bone. 1986a. Detection of krill (Euphausia
superba) near the sea surface: preliminary results using a towed
upward-looking echo-sounder. British Antarctic Survey Bulletin
72: 61-70.
Everson, I. and D. G. Bone. 1986b. Effectiveness of the RMT-8 system for sampiing krill (Euphausia superba) swarms. Polar Biology 6: 83-90.
Foote, K. G., I. Everson, J. L. Watkins and D. G. Bone. 1990. Target strengths of Antarctic krill (Euphausia superba) 38 and 120 kHz. Journal of Acoustic Society of America 87: 16-24.
Marine Zooplankton Colloquium 1, 1989. Future marine zooplankton research - a perspective. Marine Ecology Progress Series 55: 197-206.
Murphy, E. J., D. J. Morris, J. L. Watkins and J. Priddle. 1988. Scales of interaction between Antarctic krill and the environment. In: D. Sahrhage (ed.), Antarctic Ocean and Resources Variability, pp. 120-130, Springer, Berlin.
Price, H. J. 1989. Swimming behavior of krill in response to algal patches: a mesocosm study. Limnology and Oceanography 34: 649-659.