Enrico Schwabe1, Katharina M. Jörger1, Laura Würzberg2
Michael Schrödl1 (not on board)
1 ZSM
2ZMH
Objectives
Within the framework of an inventory of Atlantic cold water and deep-sea molluscs, we observed a generally high species richness and local abundance of molluscs in the Southern Ocean. Many Antarctic gastropods appear eurybathic, however, traditional shell-based taxonomy remains to be confirmed by molecular approaches.
Surprisingly, just a single benthic Antarctic deep-sea gastropod species was found to extend slightly north of the boundary of the Southern Ocean yet and so far no faunal overlap between Atlantic and Antarctic deep-sea basins could be found (Schrödl et al. 2010) In lower latitudes of the southern Atlantic, gastropod faunas were found to be poor in species and abundance (Schwabe et al. 2007, Schrödl et al 2010). Comparisons along a transect from the Equator to the Weddell Sea thus showed increasing gastropod diversity from lower to higher latitudes, opposing a previous paradigm. During SYSTCO II we collected molluscs from stations along the Antarctic convergence, a thus far unsampled area that is crucial for addressing apparent biogeographic boundaries between the strictly Antarctic fauna and the South Atlantic Ocean deep-sea basins previously investigated. Species limits as revealed by morphology will be assessed by molecular markers.
In the era of molecular systematics the phylogeny of basal molluscs and of several subgroups is in a state of revolution and Antarctic/deep-sea taxa such as e.g.
monoplacophorans have played a key role. Further members of basal taxa and more adequately preserved specimens are needed for molecular and, ultimately, phylogenomic research. Transcriptome analyses will give further insights into functional aspects and adaptations to the special ecological conditions in the deep-sea and a comparison of expression patterns of shell building proteins is planned.
In order to explore the trophic ecology of molluscs in benthic deep-sea communities we will apply comparative studies on fatty acid and isotope compositions.
Work at sea
We sorted and pre-identified molluscs from 7 EBS stations (2,752 m - 4,046 m)
27. Biogeography and phylogeny of southern Atlantic deep-sea mollusca meiofaunal molluscs, 2-3 MUC cores were sampled at each major station. The first 5 cm (suspected to contain most meiofauna) of each assigned sediment core were sieved to 100 µm and bulk fixed in 96 % ethanol. Due to the minute size of the animals, reliable sorting is impossible in the field and will be conducted later in the lab.
All taxonomic identification herein is in a preliminary stage and needs thorough reinvestigation with comparative material and revised literature.
Preliminary results
To date we collected 1041 specimens of molluscs from all gears, preliminary identified to 111 morphospecies. With approx. 65 morphospecies, Gastropoda are the dominant group in terms of species numbers, followed by Bivalvia with 29 morphospecies. Concerning local abundance bivalves dominated the samples from the first two regimes (Fig. 27.1). Even though AGT samples cannot be used for quantative comparison, the first rough evaluation shows a general trend of a higher abundance of gastropods than bivalves at the last regime (station PS79/175).
Morphospecies from all remaining molluscan taxa occurred in low numbers and in general a high degree of putative species are only represented by singletons.
So far we identified 6 morphospecies of Scaphopoda, 4 of Caudovofeata, 6 of Solenogaster and obtained one benthic cephalopod (Octopodidae) from the shallow station at a seamount close to 54°S, 52°W (AGT PS79/177-7).
The faunistic composition of Bivalvia was similar between the first two regimes with representatives of putatively the same morphospecies of the families Sareptidae Kelliidae, Limidae, Limopsidae, Montacutidae and Thyasiridae collected at all stations. Surprisingly, Nuculidae which dominated the bivalve composition at the first station (station PS79/81) was not found thereafter. First sorting from AGT samples indicate a completely different bivalve composition in the third regime (station PS79/175) with only representatives of Sareptidae and Thyasiridae co-occuring with the first two stations. In general, we noted a highly patchy distribution with considerable variation in abundance between repeated EBS drops at one station (Fig. 27.2). In the first regimes most gastropod species were only recorded from single or few specimens and thus no general trend on faunistic composition can be drawn. The high abundance of (ecto-)parasitic Melanella spp.
(Eulimidae) at station PS79/86-25 was remarkable; a putative correlation with the abundance and diversity of holothuorids still needs to be confirmed. At the last station (PS79/175) gastropods were by far more abundant and with different morphospecies compared to the first stations. The gastropod fauna was dominated by members of the families Turridae and Buccinidae.
Fig. 27.1: Comparison in abundance of molluscan taxa between the different EBS stations in the first two regimes.
Fig. 27.2: Percentage of molluscan morphospecies from the different EBS stations in the first two regimes.
Data management Refer to page 70.
references
Schrödl, M., Bohn, J. M., Brenke, N., Rolán, E. & Schwabe, E. (2011). Abundance, diversity,
28. AGASSIZ TrAWl (AGT) DEPlOYMENTS
Dorte Janussen1 , Simone Brandao2, Tomas Cedhagen3, Freija Hauquier4, Charlotte Havermans5, Katharina Jörger6, Franck Lejzerowicz7, Anna Meyer-Löbbecke8, Sarah Schnurr7, Enrico Schwabe6, Martina Vortkamp2, Laura Würzberg8 Ann Christine Zinnkann8, and Angelika Brandt8
1Senckenberg, Frankfurt/M
An AGT was deployed, as done during the ANDEEP I-III and SYSTCO I expeditions, in order to sample a representative collection of animals for zoogeographical, ecological, molecular and biochemical investigations. For the purpose of comparison of our results, as far as possible we conducted the employments according to the same scheme for each expedition of the ANDEEP-SYSTCO program. As far as possible, the AGT and other benthic gears were employed within the same research areas sampled during the Eddy Pump project.
Work at sea
Sampling was conducted at the three major benthic stations by the big AGT with an inner fine-meshed (500 µm) net in the cod end of the AGT-net, in order to collect also smaller animals, including macro- and meiofauna. For the first three stations we used the new AWI-AGT, which is symmetrical and can be deployed also upside-down, which is not an advantage though, because only one of the net surfaces is equipped for sliding over the ground and sampling. Because the symmetrical AGT proved to be unstable and would easily turn around during deployment, after deployment no. 3, we decided to use the old AWI-AGT (Fig. 28.1), which is actually not a “true” Agassiz trawl, because it is asymmetrical and can glide only on one side, but for that reason has proven to be much more stable than the new trawl.
As the function of the new and old trawl is identical, we here use the term AGT for both. After the second failure, deployment no. 5, we made some improvements in order to keep the net on the bottom, such as fastening a steel chain to the lower side of the net entrance and adding some extra weights onto the AGT. After the loss of the epibenthic sledge, we employed a Rauschert Dredge (RD, Figure 28.1) attached to the AGT by a long wire, in order to obtain additional material of especially the smaller animals.
Preliminary and expected results
Of the 10 deployments alltogether, two failed (AGT no. 3 and 5); after some technical improvements on the gear (see above) all deployments were successful (Table 28.1).
AGT 1-2 in the low productivity area (52oS, 10oW) contained small catches with megafauna of mainly holothurians, ophiuorids, molluscs, polychaetes and also a few sessile cnidarians.
AGT 4, 6-7 within the high chlorophyll bloom (51-51.5oS, 12oW) gave small, but comparably diverse megafauna catches including holothurians (min. 10 spp. from AGT 4), ophiuroids, polychaetes, molluscs and few sponges.
AGT 8, 9 within the high productivity area north of South Georgia (51oS, 39oW) provided lots of big stones and many animals. The megafauna catch was abundant and diverse, including big holothurians, fishes, ophiuroids, molluscs, polychaetes, and sponges. The macrofauna was rather poor, as the AGT, even with the fine-meshed inner net, is designed to catch mainly the bigger animals, less smaller ones.
AGT 10 shallow station (330 m) at 53o49’S, 52o21’W provided very abundant and diverse sponges, also the other megafauna taxa were diverse, and the macrofauna was well represented, e.g. by crustaceans.
Tab. 28.1: List of the AGT-deployments with metadata during SYSTCO II
Station
PS Date
Deploy-ment lat. lon. Depth,
[m] Trawl.
dist., calc., [m]
· Catch/
remarks
79/81-19 20.01.12 AGT 1/
new 52o0.2`S 9o59.5`E 3760 1809 Small, OK 79/84-26 23.01.12 AGT 2 52o6.0`S 10o2.5`E 4100 1915 Small, OK
79/85-16 27.01.12 AGT 3 52oS 8oW 2750 1609 Failure
79/86-21 31.01.12 AGT 4 51o59.9`S 12o2.4`W 3940 2189 Diverse megafauna 79/86-23 31.01.12 AGT 5 51o59.1`S 12o4.3`W 3981 2075 Failure 79/141-7 18.02.12 AGT 6 51o15.96`S 12o30.5`W 4100 1909 Good catch 79/141-8 18.02.12 AGT 7 51o16.0`S 12o37.5`W 4110 1904 Good catch 79/175-3 03.03.12 AGT 8 51o49.95`S 39o24.0`W 4150 1894 Stones, good
catch
79/175-4 03.03.12 AGT9/old 51o50.4`S 39o24.0`W 4160 1891 Stones, good catch
79/177-7 07.07.12 AGT 10/
old 53o48.5`S 52o21.0`W 330 619 Animals, best catch
28. Agassiz trawl (AGT) deployments
Fig. 28.1: The old AWI-AGT and the Rauschert Dredge used, the latter belongs to Charlotte Havermann (photo Ann Christine Zinnkann)
Data management Refer to page 75.