Fleischer, Dirk

Piepenburg, Dieter

OceanRep

Fig. 1 RV Maria S. Merianduring cruise MSM02/3 Mitteilun en zur Kieler Polarforschun Heft 22-2006 Dieter Piepenburg 1•2, Dirk Fleischer21 Akademie der Wissenschaften und Literatur Mainz 2 Institut für Polarökologie der Universität Kiel Benthological studies du ring cruise MSM02/3 of RV Maria S. Merian From July 31 to August 17, 2006, we participated in cruise MSM02/3 of R/V „Maria S. Merian" (Fig. 1). The overall scientific objective of this expedition was to analyse environmental controls and postglacial climate variability of biosedi­mentary systems at selected study areas on the shelves around Svalbard (Fig. 2). The major working tool was the manned submersible JAGO (Fig. 3), which oper­ated in topographically complex submarine terrains that are difficult to sample with conventional gear. Within the integrated multidis­ciplinary approach of the cruise, involving oceanographic, geo-logical and biological studies, the mai n objective of our bentho­logical sampling programme was to analyse spatial variations in the structure of benthic assem­blages in the study area. In the i nvestigated coastal habitats, the distribution, composition and abundance of the benthos are assumed to be mainly controlled by light penetration (and, hence, the oc­currence of coralline red algae) and the kinetic energy regime (waves, current, tides). As these factors depend very much on the water depth, a depth zonation is likely to be the most pronounced pattern in the distribution of benthic assem­blages. In addition, sedimentation setting (which in turn is largely determined by the presence or absence of glaciers) is of special significance off Svalbard coasts. Within the greater context of international and multidisciplinary cooperation, the analyses will contribute to the documentation of the present condition of the marine ecosystems off Svalbard. This is an important issue, as most ecologi­cal models agree in the prediction that northern seas will experience particu­larly severe ecosystem shifts because of pronounced sea temperature rise and rapid seaice reduction. Due to the influence of the North Atlantic Current sys-2 tem, even now most benthic species inhabiting the coastal waters off Svalbard, ft Mitteilun en zur Kieler Polarforschun Heft 22-2006particularly at the western and northern coasts, are actually of Atlantic origi n, i.e., they are immigrants from the south that occur at both polar and boreal lati­tudes. Endemie Arctic species ,which are adapted to extreme­ly low temperatures character­izing polar environments anddo occur in Arctic waters only,are clearly less numerous thanthose Arctic-boreal species.Due to the expected climate­related ecosystem shifts, theirnumbers are likely to furtherdecrease, especially in transi­tion regions between sub-Arc­tic and high-Arctic climates,such as Svalbard. We will test whether this trend has already set off.Sampling The composition, abundance and distribution of seafloor communities of the Svalbard shelf were investigated - in addition to JAGO - by means of three gears: (1) dredge (DRG; Fig. 4), (2) van Veen grab (BG; Fig. 5), and (3) photographicprobe (FTS; Fig. 6). The basic idea behind the use of a combination of differentgears was that each method has its specific pros and cons and is most adequatefor the sampling of different community fractions and at different seafloor types.Together, especially if their results are combined with those gained with theFig 2 Route ond study oreas of RV Maria S. Merian during cruise MSM02/3 Fig 3 Manned submersible JAGO, being deployed in the Lamfjord (Spitsbergen)w 3 Tab 1 Benthic sampling statians during R/V MARIA S. MERJAN Cruise 02/3: BG - van Veen grab; ORG - Oredge; FTS - Pho-tographic probe Mitteilun en zur Kieler Polarforschun Heft 22-2006video-based ,visual transect census' carried out using the submersible JAGO, they provide a more complete picture of the benthic assemblages present in the study area, as if they would in case of separate deployment. FTS and ORG were employed, together with the submersible JAGO, in the study areas Mitragrunnen, Moffen Island, Mosselbukta and Kap Rubin (Tab. 1, Fig. 7). MSM Gear Date Latitude Longitude Oepth Region Remarks 02/3 N E (m) No. 636 DRG·l 02.08.06 79°05,47' 10 °48,17' 98· 99 Mitragrunnen Course 129 °; · 79°05,68' ·10°49,38' 15min; lkn 79°05,91' 10 °47,69' Course 262°; 637 DRG-2 02.08.06 · 79°05,84' ·10°46,37'48· 49 Mitragrunnen 15min; lkn 653 FTS·l 04.08.06 79°05,940' 10 °45,63' 41· 69 Mitragrunnen 25 pictures · 79°05,701' • 10 °46,84'660 FTS-2 05.08.06 79 °59,534' 14°13,962' 39. 48 Moffen Island 20 pictures • 79°59,469' · 14 °13,335'661 DRG-3 05.08.06 79°59,26' 14°15,28' 40· 40 Moffen Island Course 309°; · 79 °59.45' ·14°14,08' 15min; lkn 674 FTS-3 06.08.06 79 °54,591' 15°48,906' 40· 51 Mosselbukta 30 pictures • 79°54,647' 15°48,069' 675 DRG-4 06.08.06 79 °54,21' 15 °46,94' 61· 72 Mosselbukta Course 206°; • 79 °53,53' ·15°44,89' 15min; lkn 696 BG-1 08.08.06 79°58,02' 17°44,54' 383 Northern Hinlopen Three proper • 79°58,02' ·17°44,55' Strait replicates 704 DRG-5 09.08.06 80°31,22' 19°44,23' 45· 43 Kap Rubin Course 26°; · 80°31.44' ·19°43,02' 15min; lkn 705 FTS·4 09.08.06 80°32,039' 19°50,745' 88· 24 Kap Rubin 29 pictures • 80°31,988' • 19 °51,383'720 BG-2 11.08.06 80°18,94' 23°25,18' 312· 321 Ouvefjord Three proper · 80°18,73' ·23°25,67' replicates 722 FTS-5 11.08.06 80°15,312' 23°33.435' 47. 42 Duvefjord 30 p1ctures • 80°15,502' • 23°33,919'734 DRG-6 13.08.06 79°34,96' 17°50,78' 43.49 Lomfjord Course 171°; · 79°34,69' ·17°50,94 15min; lkn 735 FTS-6 13.08.06 79°34,800' 17°50,504' 54· 66 Lomfjord 30 pictures • 79°34,789' • 17°51,664'737 BG-3 13.08.06 79°41,01' 18°18,07' 417· 417 Lomfjord Three proper • 79°41,01' ·18°18,07' replicates 743 FTS-7 14.08.06 79°35,838' 18°52,195' 25· 239 Hinlopen Strait 30 pictures • 79°36,005' ·18°51,820'744 BG-4 14.08.06 79°14,16' 20°53,38' 79· 79 Southern Hinlopen Three proper • 79°14, 16' ·20°53,38' Strait replicates 746 BG-5 14.08.06 78°59,20' 24°35,83' 208 Barents Sea Three proper • 78°59,20' ·24°35,83' replicates 747 BG-6 15.08.06 79°13, 10' 25°51,27' 192 Barents Sea Three proper • 79°13,10' ·25°51,28' replicates 748 BG·7 15.08.06 78°46,03' 25 °08,28' 122 Barents Sea Th ree proper • 78°46,03' ·25°08,28' replicates 749 BG-8 15.08.06 78°23,14 24°44.45 138 Barents Sea Three proper • 78°23, 14 ·24°44,45 replicates 750 BG-9 15.08.06 78°16,19' 27°11.70 312 Barents Sea Th ree proper • 78°16,19' ·27°11,70 replicates 755 FTS-8 16.08.06 79°57, 181' 15°45,014' 40· 95 Hornsund 30 pictures • 79°57,183' • 15°44,320'Mitteilun en zur Kieler Polarforschun Heft 22-2006 In the Duvefjord, we combined the FTS and BG. In the Lomfjord, it was pos­sible to combine all four techniques JAGO, DRG, FTS and BG. The Hornsund was sampled by JAGO and FTS. The stations in the northwestern Barents Sea were sampled by BG only. Dredge The dredge was used to collect macro- and megabenthic epifauna. This gear does not provide quantitative samples but it can be employed on grounds made up by pebbles, cobbles and stones, i.e., at locations where the use of grabs and corers is not possible because these gears do not close and thus do not provide samples at all. The dredge used during the cruise consists of a rectangular frame (100 cm wide and 40 cm high), to which a net of 150 cm length and 0.5 cm mesh size is fixed (Fig. 4). The main objective of the dredge hauls was a qualitative species inventory of the benthic fauna and flora. In addition, the results will help to identify the organisms visible in the video footage obtained during JAGO dives and in the seabed pictures provided by the photographic probe. During the cruise the dredge was employed at a total of 6 stations (Tab. 1, Fig. 7), all of which were in close proximity to the loca­tions of JAGO dives and/or deployments of the photographic probe. All live specimens were sorted out of the catches and identified to lowest possible taxonomic level (putative species). Moreover, for each taxon identified the gross abundance was estimated (using a logarithmic abundance classification scheme), and voucher specimens were selected and fixed in a 4% formalin-seawater solution for later more precise identification in the lab. Van Veen-type grab A van Veen grab was employed to ob­tain quantitative samples of the macrob­enthos. The grab used during the cruise measured 60 cm in width and 30 cm in height. It had an opening of 46.5 x 46.5 cm (Fig. 5). lt was deployed at a total of 9 stations (Tab. 1, Fig. 7). Their posi-Fig 4 Dredge used during cruise MSM02/3 of RV Morio S. MerionFig 5 Von·Veen grob used during cruise MSM02/3 of RV Morio S. Merion 5 Fig 6 Photographie probe used during cruise MSM02/3 of RV Maria S. Merian 6 Mitteilun en zur Kieler Polarforschun Heft 22-2006 tions were selected according to three criteria: (1) the seabed texture has to be appropriate (in case the seafloor primarily consists of sand, pebbles and stones the grab will not close (see above); (2) stations sampled last year by Norwegian colleagues are revisited; and (3) getting samples from areas that have not been investigated to date. For statistical reasons, at each station three replicate samples were taken in order to investigate the smallscale patchiness of the ben­thic fauna. Samples were gently washed through a sieve of 1 mm mesh size, and the sieve residue was fixed in 70% alcohol for later analysis of species composi­tion, abundance and biomass in the lab after the cruise. Photographie probe The photographic probe was used to obtain high resolution stills of the seabed, complementing the video footage obtained during the JAGO dives. The primary goal of its use was a quantitative inventory of the megabenthic epifauna. The probe basically consisted of a vertically oriented still camera (PHOTOSEA ™ 70 D) and an obliquely oriented strobe (PHOTOSEA ™ 1500 D), both aligned 1 m apart from each other in a steel frame of 2.3 m length in total (Fig. 6). lt was vertically lowered to the sea fl.oor from the ship, which by means of its high-precision GPS-based Dynamic Positioning System (DPS) moved slowly with a constant speed of 0.25 kn along a transect that was determined before the deployment in a multibeam-derived map displaying the bathymetry of the study in high resolution. On bottom contact of a weight hanging about 1.4 m below the probe, both camera and strobe were triggered, and bottom contact was signalled to the ship via a single conductor cable. The gear was then heaved a few metres and subsequently lowered again for the next bottom contact and seabed exposure. By control of the ship's DPS, the interval between the single shots was kept constant at approximately 10 m. In this manner, series of 30 nonoverlapping photographs, distributed along the predefined 300m transects, were obtained at each station [at some stations, less than 30 shots were taken due to technical problems]. The system did not comprise a video camera allow­ing for realtime monitoring; i.e. all sea floor photographs were taken blindly. As -I Mitteilunqen zur Kieler Polar forschunq Heft 22-2006the distance be-.tween camera and seabed was kept constant for each exposure by means of the trigger mechanism, the bottom area imaged by each photograph was the same (1 m2). Two laser light points with a distance of 22.5 cm to each other were projected on the depicted seabed area and provided a scale in each photo. In total, 224 seabed photographs were taken at 8 stations at water depths rang­i ng from 25 to 240 m (Tab. 1, Fig. 7). The station plan was designed in order to complement the video surveys carried out by JAGD, i.e., whenever feasible, the photographic transects were embedded into the video transects covered by JAGD. The exposed slides will be developed and analysed at home. The high resolution of the sea floor pictures, due to the relatively small camera-seabed distance and the high quality of the optical system and film material used (KODAK EKTA­CHROME™ 64 ASA 70 mm colour slide film), will allow to investigate epibenthic individuals as small as 1 mm. The „closeup" pictures of the sea floor (for an example, see Fig. 8) will be evaluated according to the following aspects: (a) ,,in situ" observations of epibenthic habitat structures(b) quantitative determination of absolute population densities(c) identification of spatial distribution patterns and, if population densities aresufficiently high,(d) assessment of size spectra of large epibenthic organismsFor species identification, megabenthic specimens were collected from dredgecatches taken at the same or nearby locations. In the course of the quantita­tive analysis of the photographs, epibenthic organisms will be determined bycomparison with these specimens (and, if necessary, with the help of taxonomicexperts) and counted. For comparative analyses, these counts will be raised toabsolute abundance values (ind m·2).Preliminary results Dredge catches Overall, the number of macrobenthic (putative) species, sorted on board out of the dredge catches (Fig. 4), totals 111 (Tab. 2). The numbers of (putative) spe­cies per station ranged from 18 at station 636 (Mitragrunnen) to 46 at station 675 (Mosselbukta) (Tab. 2). Overall, Crustacea were most diverse (24; Tab. 3), Station 636 Total: 111 18 637 661 675 704 34 35 46 41 734 45 followed by Mollusca (23), Polychaeta (15), and Echinodermata (14). Only two species - the brittle star Ophiopholis aculeata (Echinodermata: Ophiuroidea) and the prawn Lebbeus polaris (Crustacea: Decapoda) - were present in all catches. Tab 2 Number of putative spedes (live spedmens anly) in dredge samp/es. 7 1 1 1 11 II 1 II 1 Tab 3 Number of (putative) spedes for higher taxa in dredge cotches. Tab 4 Number of putative spe· des identified in video footage gained during 10 JAGD dives. 1 8 Mitteilunaen zur Kieler Polarforschuna Heft 22-2006 1 Taxonomie group Rhodophyta Phaeophyta Porifera Cnidaria Brachiopoda Bryozoa Sipunculida Nemertea Mollusca Polyplacophora Gastropoda Bivalvia Polychaeta Pantopoda Crustacea Echinodermata Crinoidea Asteroidea Ophiuroidea Echinoidea Holothuroidea Chordata Ascidiacea Pisces Station Total: 57634 14 Number of (putative) species Note that these numbers are conserv­ative estimates of species richness, as it is certain that more species will be added in a more detailed analysis in the lab after the cruise. 2 1 2 8 1 4 2 1 23 1 15 7 15 4 24 14 1 4 6 2 1 10 2 8 644 647 652 14 2 12 JAGO video footage In a preliminary analysis undertaken on board, part of the video footage gained during JAGO dives (10 stations in total) was scanned for the compo­sition of the epibenthic assemblages imaged along the dive transects. In total, the number of megabenthic (putative) species, identified in the video footage, was 57 (Tab. 4). The numbers per station ranged from 2 at station 647 to 29 at station 684 (Tab. 4). Echinoderms were most diverse (13; Tab. 5), followed by Cnidaria (9), Mollusca (8), and Chordata (7). 657 671 16 18 680 684 711 731 8 20 29 13 lt should again be noted that these numbers are conservative estimates of spe­cies richness, as it is certain that more species will be added in a more detailed, visual transect census' carried out in the lab after the cruise. 

Benthological studies during cruise MSM02/3 of RV Maria S. Merian

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