DOCSLIB.ORG

Salp/Krill Interactions in the Southern Ocean:Spatial Segregation and Implications for the Carbon flux

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Deep-Sea Research II 49 (2002) 1881–1907 Salp/krill interactions in the Southern Ocean:spatial segregation and implications for the carbon flux E.A. Pakhomova,*, P.W. Fronemanb, R. Perissinottoc a Department of Zoology, University of Fort Hare, P/Bag X1314, Alice 5700, South Africa b Southern Ocean Group, Department of Zoology and Entomology, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa c School of Life and Environmental Sciences, University of Natal, Durban 4041, South Africa Abstract Available data on the spatial distribution and feeding ecophysiology of Antarctic krill, Euphausia superba, and the tunicate, Salpa thompsoni, in the Southern Ocean are summarized in this study. Antarctic krill and salps generally display pronounced spatial segregation at all spatial scales. This appears to be the result of a clear biotopical separation of these key species in the Antarctic pelagic food web. Krill and salps are found in different water masses or water mass modifications, which are separated by primary or secondary frontal features. On the small-scale (o100 km), Antarctic krill and salps are usually restricted to the specific water parcels, or are well segregated vertically. Krill and salp grazing rates estimated using the in situ gut fluorescence technique are among the highest recorded in the Antarctic pelagic food web. Although krill and salps at times may remove the entire daily primary production, generally their grazing impact is moderate (p50% of primary production). The regional ecological consequences of years of high salp densities may be dramatic. If the warming trend, which is observed around the Antarctic Peninsula and in the Southern Ocean, continues, salps may become a more prominent player in the trophic structure of the Antarctic marine ecosystem. This likely would be coupled with a dramatic decrease in krill productivity, because of a parallel decrease in the spatial extension of the krill biotope. The high Antarctic regions, particularly the Marginal Ice Zone, have, however, effective physiological mechanisms that may provide protection against the salp invasion. r 2002 Elsevier Science Ltd. All rights reserved. Re´ sume´ Les observations disponibles sur la distribution spatiale et l’ecophysiologie! de l’alimentation du krill antractique, Euphausia superba, et du tunicier Salpa Thompsoni dans l’Ocean! Austral sont synthetis! ees! dans cette etude.! Le krill et les salpes presentent! une distribution qui se traduit en gen! eral! par une forte segr! egation! spatiale, a" toutes les echelles! d’espaces. Ceci semble etre# le resultat! d’une separation! claire des niches ecologiques! de ces deux especes" cles! du reseau! trophique antarctique. Le krill et les salpes sont observes! dans des masses d’eau differentes! qui sont separ! ees! par des frontieres" primaires et secondaires. A petite echelle! (o100 km), soit le krill antarctique et les salpes sont habituellement localisee! dans des parcelles d’eaux specifiques,! ou alors ils sont separ! es! verticalement. Les vitesses de broutage du krill et des salpes, estimees! en utilisant la technique de fluorescence in situ, sont parmi les plus elev! ees! rencontrees! au sein du reseau! trophique pelagique! antarctique. Bien que le krill et les salpes peuvent parfois consommer l’ensemble de la production primaire journaliere," l’impact de leur activite! de broutage est gen! eralement! moder! e(! p50% de la production primaire). Les consequences! ecologiques! regionales! d’annees! caracteris! ees! par des fortes densites! de salpes peuvent etre# *Corresponding author. E-mail address: [email protected] (E.A. Pakhomov). 0967-0645/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII:S 0967-0645(02)00017-6 1882 E.A. Pakhomov et al. / Deep-Sea Research II 49 (2002) 1881–1907 dramatiques. Si la tendance au rechauffement,! qui est observee! autour de la Peninsule! Antarctique et dans l’Ocean! Austral, continue, les salpes pourraient jouer un role# plus important dans la structuration des ecosyst! emes" marins antarctiques. A cela serait probablement associe! une diminution dramatique de la productivite! du krill, en raison d’une diminution de l’extension spatiale du biotope du krill. Cependant, aux hautes latitudes, et en particulier dans la zone marginale des glaces, il existe des mecanismes! physiologiques effectifs qui pourraient offrir une certaine protection vis a" vis d’une invasion par les salpes. 1. Introduction 1993a; Park and Wormuth, 1993; Kawamura et al., 1994; Nishikawa et al., 1995). With the exception The Antarctic krill, Euphausia superba, and the of only few areas, such as Antarctic Peninsula tunicate, Salpa thompsoni, are among the most region, spatial exclusion between Antarctic krill important filter-feeding metazoans of the Southern and salps has been widely documented (Pakhomov Ocean, ranking only after copepods in terms of et al., 1994a; Hosie, 1994; Voronina, 1998). Studies total dry pelagic biomass (Pages, 1997; Voronina, on the community structure of zooplankton 1998). These two species are also recognized as conducted in the vicinity of the Greenwich microphages of key importance, as they are able to meridian have indicated that Antarctic krill and efficiently re-package small particles into large fast salps may overlap in their distribution south of the sinking feces, thereby playing a major role in Antarctic Polar Front (Fransz and Gonzalez, channeling biogenic carbon from surface waters 1997; Pakhomov et al., 2000). Feeding studies into the long-living pools and to the ocean’s conducted in this region provided evidence that interior and seafloor (Huntley et al., 1989; Fortier these species may at times consume the entire daily et al., 1994; Schnack-Schiel and Mujica, 1994; primary production (Dubischar and Bathmann, Pakhomov et al., 1997; Le Fevre" et al., 1998; 1997; Perissinotto et al., 1997; Perissinotto and Perissinotto and Pakhomov, 1998a). As a conse- Pakhomov, 1998a; Froneman et al., 2000). Unlike quence, the ecological role of these two key species for case of krill, for which there are numerous data in the Antarctic pelagic food web has recently on its feeding ecology, there are still large gaps in received much attention (e.g., Nishikawa et al., our understanding of the biology and the ecologi- 1995; Siegel and Loeb, 1995; Siegel and Harm, cal role of salps in the Southern Ocean (Le Fevre" 1996; Dubischar and Bathmann, 1997; Loeb et al., et al., 1998). The aims of this paper are to 1997; Kawaguchi et al., 1998; Perissinotto and summarize studies on the trophic ecophysiology Pakhomov, 1998b; Ross et al., 1998). It has been of Antarctic krill and of the tunicate S. thompsoni, suggested that krill and salps may be in direct with particular emphasis to the tunicates, and to competition with one another in certain areas of discuss the phenomenon of krill/salp spatial the Antarctic Peninsula (Loeb et al., 1997) and in separation. the Lazarev and Cooperation Seas (Perissinotto and Pakhomov, 1998a, b). It also was tentatively postulated that if the increase in seawater tem- 2. Materials and methods perature, already observed in the Antarctic Penin- sula region, continues (Zwally, 1991; Rott et al., Data on ingestion rates of Antarctic krill, E. 1996), salps may spread into the high Antarctic superba, and of the tunicate, S. thompsoni, regions, with important implications for the estimated using the gut fluorescence technique regional carbon flux and the Antarctic food web were obtained mainly during the three expeditions structure (Perissinotto and Pakhomov, 1998a, b). to the southern part of the Atlantic sector of the In the Southern Ocean, S. thompsoni is generally Southern Ocean:(a) the second cruise of the South restricted to the warmer water masses (Voronina, African Antarctic Marine Ecosystem Study 1984; Nast, 1986; Siegel et al., 1992; Pakhomov, (SAAMES II) conducted aboard the mv SA E.A. Pakhomov et al. / Deep-Sea Research II 49 (2002) 1881–1907 1883 Agulhas along the Greenwich Meridian (WOCE CmÀ2) and from 1 to 1200 mg C mÀ2 (mean SR2 line) in January 1993 (Perissinotto et al., 1997; 2207320 mg C mÀ2) in the regions of dense and Froneman et al., 2000; Pakhomov et al., 2000); (b) low krill concentrations, respectively (Voronina, the SAAMES IV aboard the mv SA Agulhas in the 1998). Lazarev Sea during December 1994–January 1995 Although Southern Ocean tunicates have not (Froneman et al., 1997; Perissinotto and Pakho- been targeted specifically, over the past two mov, 1998a, b); (c) the joint Scandinavian/South decades a substantial amount of data on S. African Antarctic Research Expedition aboard the thompsoni density has been accumulated in differ- mv SA Agulhas along the 61E meridian between ent sectors of the Southern Ocean (Table 1). In 491S and 601300S (Pakhomov, 2002; Pakhomov summary, these data indicate extreme variability in and Froneman, 2002a, b). salp densities across the Southern Ocean (Table 1). In addition, numerous published and unpub- Nevertheless, throughout much of the area south lished sources (mentioned throughout the text) on of 401S, S. thompsoni densities remain moderate, krill and salps ingestion rates, abundances, bio- on average varying between o0.1 and 30 mg mass and distribution in the Southern Ocean were CmÀ2, or between o0.1 and 30 ind mÀ2. However, used for this synthesis. To convert wet weight into S. thompsoni densities in the Antarctic Peninsula carbon weight, the following conversion factors region, particularly in the Bransfield Strait and were used:(a) S. thompsoni dry weight was around Elephant Island, were found to be assumed to be 4% of wet weight, and carbon consistently elevated (Table 1). Furthermore, the weight was assumed to be 4.3% of dry weight secondary frontal systems that demarcate low and (Ikeda and Mitchell, 1982; Ikeda and Bruce, 1986; high latitude water masses around the Antarctic Hagen, 1988; Huntley et al., 1989; Donnelly et al., Continent, e.g., Weddell–Scotia Confluence, 1994); (b) E. superba dry weight was assumed to be Warm Counter Weddell Current in the Lazarev 22% of wet weight, and carbon weight assumed to Sea, the northern part of the Ross Sea, also be 45% of dry weight (Ikeda and Mitchell, 1982; showed enhanced densities of S.
Recommended publications
  • An Observation of Two Oceanic Salp Swarms in the Tasman Sea: Thetys Vagina and Cyclosalpa Affinis Natasha Henschke1,2,3*, Jason D

    An Observation of Two Oceanic Salp Swarms in the Tasman Sea: Thetys Vagina and Cyclosalpa Affinis Natasha Henschke1,2,3*, Jason D

    Henschke et al. Marine Biodiversity Records (2016) 9:21 DOI 10.1186/s41200-016-0023-8 MARINE RECORD Open Access An observation of two oceanic salp swarms in the Tasman Sea: Thetys vagina and Cyclosalpa affinis Natasha Henschke1,2,3*, Jason D. Everett1,2,3 and Iain M. Suthers1,2,3 Abstract Background: Large oceanic salps are rarely encountered. The highest recorded biomasses of the salps Thetys vagina (852 g WW m−3)andCyclosalpa affinis (1149 g WW m−3) were observed in the Tasman Sea during January 2009. Results: Due to their fast sinking rates the carcasses and faecal pellets of these and other large salps play a significant role in carbon transport to the seafloor. We calculated that faecal pellets from these swarms could have contributed up to 67 % of the mean organic daily carbon flux in the area. This suggests that the flux of carbon from salp swarms are not accurately captured in current estimates. Conclusion: This study contributes information on salp abundance and biomass to a relatively understudied field, improving estimates for biogeochemical cycles. Background (Henschke et al., 2013) can increase the carbon flux in an The role of gelatinous zooplankton, such as salps, pyro- area up to ten-fold the daily average (Fischer et al., 1988) somes and cnidarians, in ocean food webs and biogeo- for a sustained period of time (Smith et al. 2014). chemical cycling has garnered increased attention in Due to their regular occurrence (Henschke et al., recent years (Lebrato et al., 2011; Henschke et al., 2013; 2014) and coastal dominance (Henschke et al 2011), Lebrato et al., 2013; Smith et al.
  • First Record of a Broad-Billed Prion Pachyptila Vittata at Coronation Island, South Orkney Islands

    First Record of a Broad-Billed Prion Pachyptila Vittata at Coronation Island, South Orkney Islands

    Blight & Woehler: First record of a Broad-billed Prion at Coronation Island 191 FIRST RECORD OF A BROAD-BILLED PRION PACHYPTILA VITTATA AT CORONATION ISLAND, SOUTH ORKNEY ISLANDS LOUISE K. BLIGHT1,2 & ERIC J. WOEHLER3 1Procellaria Research and Consulting, 944 Dunsmuir Road, Victoria, British Columbia, V9A 5C3, Canada 2Current address: Centre for Applied Conservation Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada ([email protected]) 3School of Zoology, University of Tasmania, Hobart, Tasmania, 7005, Australia Received 15 April 2008, accepted 2 August 2008 The known breeding distribution of Broad-billed Prions Pachyptila or as a bird blown out of its normal at-sea range by strong winds vittata is restricted to Tristan da Cunha and Gough Islands in the during poor weather. Alternatively, there may be low numbers of South Atlantic Ocean and to offshore islands around New Zealand Broad-billed Prions breeding at poorly-surveyed sub-Antarctic and the Snares and Chatham Islands, with the range at sea believed colonies, such as the South Orkney Islands. Antarctic Prions are one to extend to coastal South Africa in the South Atlantic Ocean and of the most numerous seabird species in the Antarctic (Marchant & near-shore waters around New Zealand (Marchant & Higgins 1990). Higgins 1990); they nest in the South Orkney Islands (Marchant & The taxonomy of prions remains controversial, with most authors Higgins 1990). It is possible that low numbers of breeding Broad- recognising up to six species, but varying numbers of subspecies. billed Prions have been overlooked amongst their congeners. The at-sea ranges of many Southern Ocean seabird species are Although no sympatric breeding sites are known for the two species still incompletely described, with relatively few surveys obtaining (Shirihai 2002) and the presence of this bird may have been an at-sea data for prions.
  • Salp Contributions to Vertical Carbon Flux in the Sargasso Sea

    Salp Contributions to Vertical Carbon Flux in the Sargasso Sea

    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by College of William & Mary: W&M Publish W&M ScholarWorks VIMS Articles Virginia Institute of Marine Science 2016 Salp contributions to vertical carbon flux in the Sargasso Sea JP Stone Virginia Institute of Marine Science Deborah K. Steinberg Virginia Institute of Marine Science Follow this and additional works at: https://scholarworks.wm.edu/vimsarticles Part of the Aquaculture and Fisheries Commons Recommended Citation Stone, JP and Steinberg, Deborah K., "Salp contributions to vertical carbon flux in the Sargasso Sea" (2016). VIMS Articles. 797. https://scholarworks.wm.edu/vimsarticles/797 This Article is brought to you for free and open access by the Virginia Institute of Marine Science at W&M ScholarWorks. It has been accepted for inclusion in VIMS Articles by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. 1 Salp contributions to vertical carbon flux in the Sargasso 2 Sea 3 4 5 Joshua P. Stonea,*, Deborah K. Steinberga 6 a Department of Biological Sciences, Virginia Institute of Marine Science, College of William & Mary, 7 PO Box 1346, Gloucester Point, VA 23062, USA 8 * Corresponding author. 9 E-mail addresses: [email protected] (J. Stone), [email protected] (D. Steinberg) 10 11 1 © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 12 Abstract 13 We developed a one-dimensional model to estimate salp contributions to vertical carbon flux at the 14 Bermuda Atlantic Time-series Study (BATS) site in the North Atlantic subtropical gyre for a 17-yr period 15 (April 1994 to December 2011).
  • Sc Annex 7 Cover

    Sc Annex 7 Cover

    ANNEX 7 REPORT OF THE JOINT MEETING OF THE WORKING GROUP ON KRILL AND THE WORKING GROUP FOR THE CCAMLR ECOSYSTEM MONITORING PROGRAM (Cape Town, South Africa, 27 July to 2 August 1994) TABLE OF CONTENTS INTRODUCTION MEETING OBJECTIVES PREY MONITORING Data Collection Procedures Review of Available Data Krill Biomass Estimates in the Integrated Study Regions (ISRs) Fine-scale Catch Data Fine-scale Surveys PREDATOR MONITORING ECOSYSTEM INTERACTIONS Distribution of Krill Fishing and Predators Potential Effect of Precautionary Measures Krill/Predator Functional Relationships ECOSYSTEM ASSESSMENT Development of Prey, Fishery and Environmental Indices Integrating Predator, Prey, Environmental and Fishery Indices into Ecosystem Assessments CEMP Experimental Approaches (Experimental Fishing Regimes) Incorporating Ecosystem Assessments into Management Advice ORGANISATION OF FUTURE WORK Advice on the Re-organisation of the Scientific Committee’s Working Groups List of Priority Activities Terms of Reference of a New Working Group on Ecosystem Monitoring and Management (WG-EMM) OTHER BUSINESS Future Cooperative Research ADOPTION OF THE REPORT CLOSE OF THE MEETING TABLES APPENDIX A: Agenda APPENDIX B: List of Participants APPENDIX C: List of Documents 1 REPORT OF THE JOINT MEETING OF THE WORKING GROUP ON KRILL AND THE WORKING GROUP FOR THE CCAMLR ECOSYSTEM MONITORING PROGRAM (Cape Town, South Africa, 27 July to 2 August 1994) INTRODUCTION 1.1 The second Joint Meeting of the Working Group on Krill (WG-Krill) and the Working Group for the CCAMLR Ecosystem Monitoring Program (WG-CEMP) was held at the Breakwater Lodge, Cape Town, South Africa, between 27 July and 2 August 1994, and was chaired by the Chairman of the Scientific Committee, Dr K.-H.
  • Birdlife Australia Rarities Committee Unusual Record Report Form

    Birdlife Australia Rarities Committee Unusual Record Report Form

    BirdLife Australia Rarities Committee Unusual Record Report Form This form is intended to aid observers in the preparation of a submission for a major rarity in Australia. (It is not a mandatory requirement) Please complete all sections ensuring that you attach all relevant information including any digital images (email to [email protected] or [email protected]). Submissions to BARC should be submitted electronically wherever possible. Full Name: Rob Morris Office Use Address: Phone No: Robert P. Morris, Email: Full Name: Andrew Sutherland (first noticed the second bird) Address: Phone No: Email: Species Name: Broad-billed Prion Scientific Name: Pachyptila vittata Date(s) and time(s) of observation: 11 August 2019 First individual photographed at 12.22 – last bird photographed at 13.11. How long did you watch the bird(s)? c30+ minutes – multiple sightings of 2 birds (possibly 3) and then an additional sighting of 1 bird 20 minutes later whilst travelling, flying past and photographed. First and last date of occurrence: 11 August 2019 Distance to bird: Down to approximately 20-30 m Site Location: SE Tasmania. Approximately 42°50'36.30"S 148°24'46.23"E 22NM ENE of Pirates Bay, Eaglehawk Neck. We went north in an attempt to seek lighter winds and less swell and avoid heading straight into the strong SE winds and southerly swell. Habitat (describe habitat in which the bird was seen): Continental slope waters at a depth of approximately 260 fathoms. Sighting conditions (weather, visibility, light conditions etc.): Weather: Both days were mostly cloudy with occasional periods of bright sunshine.
  • Coastal and Marine Ecological Classification Standard (2012)

    Coastal and Marine Ecological Classification Standard (2012)

    FGDC-STD-018-2012 Coastal and Marine Ecological Classification Standard Marine and Coastal Spatial Data Subcommittee Federal Geographic Data Committee June, 2012 Federal Geographic Data Committee FGDC-STD-018-2012 Coastal and Marine Ecological Classification Standard, June 2012 ______________________________________________________________________________________ CONTENTS PAGE 1. Introduction ..................................................................................................................... 1 1.1 Objectives ................................................................................................................ 1 1.2 Need ......................................................................................................................... 2 1.3 Scope ........................................................................................................................ 2 1.4 Application ............................................................................................................... 3 1.5 Relationship to Previous FGDC Standards .............................................................. 4 1.6 Development Procedures ......................................................................................... 5 1.7 Guiding Principles ................................................................................................... 7 1.7.1 Build a Scientifically Sound Ecological Classification .................................... 7 1.7.2 Meet the Needs of a Wide Range of Users ......................................................
  • DIET and ASPECTS of FAIRY PRIONS BREEDING at SOUTH GEORGIA by P.A

    DIET and ASPECTS of FAIRY PRIONS BREEDING at SOUTH GEORGIA by P.A

    DIET AND ASPECTS OF FAIRY PRIONS BREEDING AT SOUTH GEORGIA By P.A. PRINCE AND P.G. COPESTAKE ABSTRACT A subantarctic population of the Fairy Prion (Pachyprzla turtur) was studied at South Georgia in 1982-83. Full measurements of breeding birds are given, together with details of breeding habitat, the timing of the main breeding cycle events, and chick growth (weight and wing, culmen and tarsus length). Regurgitated food samples showed the diet to be mainly Crustacea (96% by weight), fish and squid comprising the rest. Of crustaceans, Antarctic krill made up 38% of items and 80% by weight. Copepods (four species, mostly Rhincalanus gigas) made up 39% of items but only 4% by weight; amphipods [three species, principally Themisto gaudichaudii made up 22% of items and 16% by weight. Diet and frequency of chick feeding are compared with those of Antarctic Prions and Blue Petrels at the same site; Fairy Prions are essentially intermediate. INTRODUCTION The Fairy Prion (Pachyptila turtur) is one of six members of a genus confined to the temperate and subantarctic regions of the Southern Hemisphere. With the Fulmar Prion (P. crassirostris), it forms the subgenus Pseudoprion. Its main area of breeding distribution is between the Antarctic Polar Front and the Subtropical Convergence. It is widespread in the New Zealand region, from the north of the North Island south to the Antipodes Islands and Macquarie Island, where only about 40 pairs survive (Brothers 1984). Although widespread in the Indian Ocean at the Prince Edward, Crozet and Kerguelen Islands, in the South Atlantic Ocean it is known to breed only on Beauchene Island (Falkland Islands) (Strange 1968, Smith & Prince 1985) and South Georgia (Prince & Croxall 1983).
  • Data Structure

    Data Structure

    Data structure – Water The aim of this document is to provide a short and clear description of parameters (data items) that are to be reported in the data collection forms of the Global Monitoring Plan (GMP) data collection campaigns 2013–2014. The data itself should be reported by means of MS Excel sheets as suggested in the document UNEP/POPS/COP.6/INF/31, chapter 2.3, p. 22. Aggregated data can also be reported via on-line forms available in the GMP data warehouse (GMP DWH). Structure of the database and associated code lists are based on following documents, recommendations and expert opinions as adopted by the Stockholm Convention COP6 in 2013: · Guidance on the Global Monitoring Plan for Persistent Organic Pollutants UNEP/POPS/COP.6/INF/31 (version January 2013) · Conclusions of the Meeting of the Global Coordination Group and Regional Organization Groups for the Global Monitoring Plan for POPs, held in Geneva, 10–12 October 2012 · Conclusions of the Meeting of the expert group on data handling under the global monitoring plan for persistent organic pollutants, held in Brno, Czech Republic, 13-15 June 2012 The individual reported data component is inserted as: · free text or number (e.g. Site name, Monitoring programme, Value) · a defined item selected from a particular code list (e.g., Country, Chemical – group, Sampling). All code lists (i.e., allowed values for individual parameters) are enclosed in this document, either in a particular section (e.g., Region, Method) or listed separately in the annexes below (Country, Chemical – group, Parameter) for your reference.
  • Species Status Assessment Emperor Penguin (Aptenodytes Fosteri)

    Species Status Assessment Emperor Penguin (Aptenodytes Fosteri)

    SPECIES STATUS ASSESSMENT EMPEROR PENGUIN (APTENODYTES FOSTERI) Emperor penguin chicks being socialized by male parents at Auster Rookery, 2008. Photo Credit: Gary Miller, Australian Antarctic Program. Version 1.0 December 2020 U.S. Fish and Wildlife Service, Ecological Services Program Branch of Delisting and Foreign Species Falls Church, Virginia Acknowledgements: EXECUTIVE SUMMARY Penguins are flightless birds that are highly adapted for the marine environment. The emperor penguin (Aptenodytes forsteri) is the tallest and heaviest of all living penguin species. Emperors are near the top of the Southern Ocean’s food chain and primarily consume Antarctic silverfish, Antarctic krill, and squid. They are excellent swimmers and can dive to great depths. The average life span of emperor penguin in the wild is 15 to 20 years. Emperor penguins currently breed at 61 colonies located around Antarctica, with the largest colonies in the Ross Sea and Weddell Sea. The total population size is estimated at approximately 270,000–280,000 breeding pairs or 625,000–650,000 total birds. Emperor penguin depends upon stable fast ice throughout their 8–9 month breeding season to complete the rearing of its single chick. They are the only warm-blooded Antarctic species that breeds during the austral winter and therefore uniquely adapted to its environment. Breeding colonies mainly occur on fast ice, close to the coast or closely offshore, and amongst closely packed grounded icebergs that prevent ice breaking out during the breeding season and provide shelter from the wind. Sea ice extent in the Southern Ocean has undergone considerable inter-annual variability over the last 40 years, although with much greater inter-annual variability in the five sectors than for the Southern Ocean as a whole.
  • The Origins of Chordate Larvae Donald I Williamson* Marine Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom

    The Origins of Chordate Larvae Donald I Williamson* Marine Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom

    lopmen ve ta e l B Williamson, Cell Dev Biol 2012, 1:1 D io & l l o l g DOI: 10.4172/2168-9296.1000101 e y C Cell & Developmental Biology ISSN: 2168-9296 Research Article Open Access The Origins of Chordate Larvae Donald I Williamson* Marine Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom Abstract The larval transfer hypothesis states that larvae originated as adults in other taxa and their genomes were transferred by hybridization. It contests the view that larvae and corresponding adults evolved from common ancestors. The present paper reviews the life histories of chordates, and it interprets them in terms of the larval transfer hypothesis. It is the first paper to apply the hypothesis to craniates. I claim that the larvae of tunicates were acquired from adult larvaceans, the larvae of lampreys from adult cephalochordates, the larvae of lungfishes from adult craniate tadpoles, and the larvae of ray-finned fishes from other ray-finned fishes in different families. The occurrence of larvae in some fishes and their absence in others is correlated with reproductive behavior. Adult amphibians evolved from adult fishes, but larval amphibians did not evolve from either adult or larval fishes. I submit that [1] early amphibians had no larvae and that several families of urodeles and one subfamily of anurans have retained direct development, [2] the tadpole larvae of anurans and urodeles were acquired separately from different Mesozoic adult tadpoles, and [3] the post-tadpole larvae of salamanders were acquired from adults of other urodeles. Reptiles, birds and mammals probably evolved from amphibians that never acquired larvae.
  • Krill Caught by Predators and Nets: Differences Between Species and Techniques

    Krill Caught by Predators and Nets: Differences Between Species and Techniques

    MARINE ECOLOGY PROGRESS SERIES Vol. 140: 13-20. 1996 Published September 12 Mar Ecol Prog Ser Krill caught by predators and nets: differences between species and techniques K. Reid*, P. N. Trathan, J. P. Croxall, H. J. Hill British Antarctic Survey, Natural Environment Research Council, High Cross. Madingley Road, Cambridge CB3 OET, United Kingdom ABSTRACT. Samples of Antarchc krill collected from 6 seabird species and Antarctic fur seal dunng February 1986 at South Georgia were compared to krill from scientific nets fished in the area at the same time. The length-frequency d~stributionof krill was broadly similar between predators and nets although the krill taken by diving species formed a homogeneous group wh~chshowed significant dif- ferences from knll taken by other predators and by nets There were significant differences In the maturity/sex stage composition between nets and predators; in particular all predator species showed a consistent sex bias towards female krill. Similarities in the knll taken by macaroni [offshore feeding) and gentoo (inshore feeding) penguins and differences between krill taken by penguins and alba- trosses suggest that foraging techniques were more important than foraging location in influencing the type of krill in predator diets. Most krill taken by predators were adult; most female krill were sexually active (particularly when allowance is made for lnisclassification bias arising from predator digestion). Because female krill are larger, and probably less manouverable, than males, the biased sex ratio In predator diets at thls t~meof year may reflect some comblnat~onof selectivity by predators and superior escape responses of male krill.
  • Towards an Understanding of Salp Swarm Dynamics. ICES CM 2002/N

    Towards an Understanding of Salp Swarm Dynamics. ICES CM 2002/N

    CM 2002/ N:12 Towards an understanding of salp swarm dynamics by Patricia Kremer ABSTRACT Species of salps are characterized by intermittent blooms. Several studies have documented the importance of physical processes both in providing seed stocks of salps and creating an environment that is favorable for the rapid increase of salp populations. Although salps are typically oceanic, most observations of bloom dynamics have been made in more accessible inshore waters, so it is difficult to assess how frequent and widespread these swarms are. A review and comparison of existing data is helping to define geographic “hot spots” for salp blooms as well as the necessary physical and biological precursors. Although at this point, the review is far from complete, several generalities are emerging. The details of the physical forcing functions vary, but the overall physical regime seems to require a region of pulsed mixing of oceanic water that results in a relatively high standing stock of autotrophs. For a salp bloom to occur, there also needs to be an adequate seed population of salps and sufficient sustained primary production to support the biomass of the salp population as the bloom develops. As non-selective filter feeders, salps are able to remove a wide range of particulates from the water column, transforming the undigested portion into fast sinking feces. Therefore, when salps occur at high densities, the water is characterized by low abundance of other plankton, with obvious trophic implications. Patricia Kremer: Marine Sciences, University of Connecticut, Groton CT 06340-6097, USA [tel: +1 860 405 9140; fax: +1 860 405 9153; e-mail [email protected]] INTRODUCTION Salps are holoplanktonic grazers that have a life history, feeding biology, and population dynamics that contrasts sharply to copepods and other crustacean zooplankton (Madin and Deibel 1998).