The Expedition ANTARKTIS XVIIl3 (EASIZ 111) OF RV ,,POLARSTERNu in 2000 Edited by Wolf E. Arntz and Thomas Brey with contributions of the participants Ber. Polarforsch. Meeresforsch. 402 (2001) ISSN 1618 - 31 93 Contents 111 Page INTRODUCTION 1 Objectives of the Cruise Summary Review of Results Itinerary Meteorological Conditions RESULTS 10 Pelagobenthic Coupling and the Role of Benthic Suspension Feeders Water Column Features Sediment Features Water Column Nutrients Chlorophyll and Particulate Organic Matter Biochemistry of Antarctic Benthic and Pelagic Organisms Water Column Picoplankton Feeding experiments with Active Filter Feeders Reproduction Studies in Filter Feeders Ecology of Epibiotic Benthic Hydrozoans 2.1.10 The Pole of Meiobenthos in the Food Web 56 Iceberg Dynamics and the Impact of Drifting Icebergs On Benthos and Fish Fauna 58 Iceberg Dynamics 5 8 Iceberg Effects on the Benthic Fauna 62 Comparative Community Analysis by Imaging Methods 63 Impact On Demersal Fish Communities 67 Biodiversity and Biogeography 70 Demersal Fish Fauna 70 Anthozoan Distribution and Biodiversity 76 Phylogenetic Relationships between Primnoid Genera 83 Bryozoan Communities 82 Mollusc Biodiversity and Ecology 85 Cephalopod Taxonomy and Biology 96 Polychaete Autumn Diversity and Reproductive Biology 98 Amphipoda: Weddell Sea - Western Antarctic - Magellan Region 103 Contents IV 2.3.9 Crinoidea and Holothuroidea 109 2.3.10 Quantitative Zoobenthos Studies 111 2.3.1 1 Biodiversity of Macrozoobenthic Communities in the Eastern Weddell Sea and at the Antarctic Peninsula 113 2.3.12 Zooplankton 116 2.3.1 3 Pelagic Microbial Biodiversity 119 2.3.14 Bird Observations during the Cruise 121 2.3.1 5 Parasitological Survey in Antarctic Fish and Invertebrates 123 2.4 Ecophysiology and Adaptive Strategies 129 2.4.1 Temperature Physiology of Antarctic Invertebrates 129 2.4.2 Respiration Rate of Antarctic Amphipods 131 2.4.3 Respiration of Meiofauna under Varying Food and Temperature Conditions 131 2.4.4 Growth Performance and Fecundity of Notothenioids 132 2.4.5 Ecology and Trophic Position of Antarctic Asteroids 2.5 Chemical Ecology and Marine Chemistry 136 2.5.1 Chemical Ecology in Antarctic Waters 136 2.5.2 Structure and Function of Marine Natural Products in Benthic Invertebrates 136 2.5.3 Persistent, Bioaccumulative, Toxic Chemicals in the Antarctic Ecosystem 157 2.6 Other Investigations 2.6.1 Study of the Winter Antarctic Marginal Ice Zone 3. ANNEXES 162 3.1 Abbreviations of Gears and Investigation Areas 3.2 Station List 3.3 Participants 3.4 Participating Institutions 3.5 Ship's Crew Introduction 1 1 Introduction 1.1 Objectives of the Cruise (W.E. Arntz) As during the two preceding cruises EASIZ l (1996) and EASIZ II (1998), the third "Polarstem" cruise of SCAR's international EASIZ Programme was to concentrate on limited areas to be studied and a small number of joint projects ("box concept"). The principal projects to be realized included: (i) Bentho-pelagic coupling in the high Antarctic ecosystem and the role of suspension feeders. On the preceding cruises, food analyses of benthic suspension feeders had revealed limited connection between the rain of larger pariicles sinking to the seafloor during the short Antarctic Summer and the food of these organisms, and incubation experiments had presented evidence for the use of the fine seston fraction by certain suspension feeders. Both the food analyses and the experiments were continued and refined On EASIZ III, putting major emphasis on the quality of the food offer and the processes that make the food available to the benthos. A multidisciplinary approach was undertaken inclhding tnicrobial ecology, seston quality analysis, flow measurements, sediment dynamics, and the study of other variables and processes above and dS the feeafloor. Investigations On shallow areas which present specific environmental conditions and a special fauna of suspension feeders were intensified by means of Visual methods and a large TV grab. (ii) Effect of iceberg scour On macro- and meiobenthic, and demersal fish, communities. As on the preceding cruises, the task was to identify recurrent successional stages during the process of recolonisation after iceberg scour, and to assess the temporal and spatial scales of the processes involved. The final goal is to determine the capacity of recovery (resilience) of Antarctic benthic communities in comparison with other marine ecosystems. One of the major difficulties to be overcome is age and growth determination of those organisms that have no hard structures, and where alternative modern methods have to be applied. The combination of fish and invertebrate approaches in joint studies has once again proved to be scientifically rewarding. Improved video techniques On the Multibox corer were helpful in distinguishing between disturbed sites and "virgin" areas which did not suffer iceberg scour for a Iong time. (iii) Biodiversity and evolutionary links of the high Antarctic Weddell Sea with the Antarctic Peninsula and other regions. Latitudinal diversity gradients are far from clear due to worldwide continuous changes in sampling gear and enormous difficulties in taxonomic identification. To improve this situation, the baseline material for genuine comparisons was to be complemented by the use of gear such as Multibox corer, Multicorer and Epibenthic sledge. Representative samples were taken, and the material will be worked up at a single Institution, to determine total per haul, or per sample, invertebrate diversity for areas in the eastern Weddell Sea and off the Antarctic Peninsula. Genetic variability was studied in copepods and peracarid crustaceans. Other specific taxa to be investigated within the biodiversity context included cnidarians, bryozoans, amphipods, molluscs, crinoids, asteroids, and cephalopods. Light and electron microscopic studies were perforrned on the occurrence of parasites in Antarctic inveriebrates and fish. (iv) Adaptive strategies On the population and community level. This project was to address physiological, ecological and behavioural adaptations to the Antarctic environment in meio- and macrofauna, and in fish populations and communities. Due to the realisation of the EASIZ 111 cruise late in the Antarctic season, special emphasis was laid on processes and strategies in populations under autumn conditions, and On spatio-temporal distribution of demersal and IntroducBon 2 pelagic fish communities in relation to environmental conditions. Taxa under specific consideration were decapod crustaceans, polychaetes, asteroids, eelpouts (Zoarcidae) and the scallop Adamussium colbecki. (V) Structure and function of marine natural products in Antarctic invertebrates. Proceeding on the assumption that the Antarctic benthic system is a fairly old one, and that the manifold interactions observed between its faunal elements reflect the frequent use of secondaty metabolites and other natural substances, an attempt was made to explore the biochemical and ecological significance of marine natural products in the field. Taxa to be studied included pterobranchs, priaoulids, brachiopods, bryozoans, gastropods and cnidarians. In addition to these core projects, studies were undertaken, among others, on persistent organic pollutants in the Southern Ocean ecosystem, and novel drifting buoys were deployed in the marginal ice Zone to improve understanding bf the mechanisms of Antarctic sea ice formation in winter. In regional terms, the idea was to work most of the time between Atka Bay and the Drescher Inlet in the southeastern Weddell Sea, then proceed towards the northem ice edge to deploy the drifting buoys, and finally work a few days around King George Island to complement work done there during EASIZ II. This schedule had to undergo certain changes due to engine trouble before reaching the Drescher Inlet (see Itinerary), so that finally work around the South Shetland Islands gained n importance. 1.2 Summary Review of Results (W.E. Arntz) Contrary to the preceding (summer) expeditions EASIZ l and 11, the EASIZ 111 cruise was realized in autumn, which made the study of the living conditions during this season, and the response of the organisms to these conditions, a central question. It is current belief that most benthic animals use the short period of plankton blooms in spring and summer to fill up their resources, scraping a hard living during the long winter season when food is presumably scarce. Already during EASIZ II we observed, however, that some benthic suspension feeders prefer a continuous supply with tiny food particles throughout the year to occasional feasting in summer. During this cruise these findings were confirmed in feeding experiments with "lollipop sponges" (lat. Stylocordyla sp.) whose food Ingestion rates were found to be comparable to those of related species in temperate and tropical latitudes. There are, however, many other benthic species which make use of macroscopic food offered in the water column. Near the South Shetlands, sea anemones, certain soft corals (alcyonarians) and sea Stars had principally fed on salps, gelatinous zooplankters which ingest small food particies in the water column. With this pelagic food concentrated in their stomachs, they undertake vertical migrations to the seafloor where they are swallowed by the benthos - a textbook case of pelagobenthic coupling! Other benthic organisms had fed On copepods, which also occur in large quantities close to the bottom in autumn, The principal result of these findings