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The tight program of scientific research cruises usually does not leave enough time for thorough tests of new research equipment and their system components, nor for extensive pilot and handling training. For this reason, ship time was requested for sea trials of two types of autonomous (not tethered) underwater vehicles owned by GEOMAR, the manned 400-meter submersible JAGO and the Hover-AUVs ANTON and LUISE, type Girona500. The aim was to test several technical and operational aspects with both vehicles at locations with differently structured terrain (from flat ground to steep rocky slopes) and to water depths of up to 500 meters. The Aeolian Islands in the Tyrrhenian Sea north of Sicily were chosen as test area. The volcanic islands offer sheltered sea conditions at their leeway, and bottom currents are usually weak or absent. Rocky and steep slopes are located in short distances to areas with flat underwater topography, providing ideal test conditions.

JAGO-AUV-FieldTrials, Äolische Inseln Wochenbericht 05.-18.02.2020

JAGO-AUV-FieldTrials, Äolische Inseln

4/2/2019 – 24/2/2019, Mindelo (Republic of Cape Verde) – Mindelo (Republic of Cape Verde) DeepC-Jelly We proposed to test the hypothesis that large gelatinous macrozooplankton (e.g. tunicates, hydrozoans) are a significant carbon storage in midwater, and a vector for carbon from midwater to the ocean floor in Cape Verde. To test this hypothesis, we studied 1) the distribution, diversity and abundance of gelatinous organisms in the epi-, meso-, and bathypelagic zone, 2) their role in transporting carbon through the pelagic foodweb to the seafloor and 3) their behavior and associations. We worked in the coastal deep sea off Santo Antão and Fogo as well as in the open ocean at the time series station CVOO and an eddy. A manned submersible was used for mesopelagic surveys, to document the behaviour and associations of deep-sea organisms and to collect living specimens. We performed pelagic video transects, discrete net sampling, and eDNA sampling down to 3000 m. ADCP and CTD transects allowed a detailed reconstruction of the effect of the islands on currents and productivity. To quantify the carbon flux of pelagic foodfalls, we also surveyed the seafloor. Sample and video analysis is still in progress, but first results indicate the impact of the pelagic tunicate Pyrosoma atlanticum, which is an upwelling-favored species largely absent from the oligotrophic open ocean, in the nearshore regions of Cape Verde as well as in the cyclonic eddy sampled. It was also observed on the seafloor and resembles a food source and a habitat in the water column and in the benthos. Specimens of pelagic fauna were collected that allow new species descriptions. New records and a new species for the region were also observed during benthic surveys. The cruise was documented in various outreach activities including national television in Cabo Verde.

We proposed to test the hypothesis that large gelatinous macrozooplankton (e.g. tunicates, hydrozoans) are a significant carbon storage in midwater, and a vector for carbon from midwater to the ocean floor in Cape Verde. To test this hypothesis, we studied 1) the distribution, diversity and abundance of gelatinous organisms in the epi-, meso-, and bathypelagic zone, 2) their role in transporting carbon through the pelagic foodweb to the seafloor and 3) their behavior and associations. We worked in the coastal deep sea off Santo Antão and Fogo as well as in the open ocean at the time series station CVOO and an eddy. A manned submersible was used for mesopelagic surveys, to document the behaviour and associations of deep-sea organisms and to collect living specimens. We performed pelagic video transects, discrete net sampling, and eDNA sampling down to 3000 m. ADCP and CTD transects allowed a detailed reconstruction of the effect of the islands on currents and productivity. To quantify the carbon flux of pelagic foodfalls, we also surveyed the seafloor. Sample and video analysis is still in progress, but first results indicate the impact of the pelagic tunicate Pyrosoma atlanticum, which is an upwelling-favored species largely absent from the oligotrophic open ocean, in the nearshore regions of Cape Verde as well as in the cyclonic eddy sampled. It was also observed on the seafloor and resembles a food source and a habitat in the water column and in the benthos. Specimens of pelagic fauna were collected that allow new species descriptions. New records and a new species for the region were also observed during benthic surveys. The cruise was documented in various outreach activities including national television in Cabo Verde.

As a result of the raising CO2-emissions and the resultant ocean acidification (decreasing pH and carbonate ion concentration), the impact on marine organism that build their skeletons and protective shells with calcium carbonate (e.g., mollusks, sea urchins, coccolithophorids, and stony corals) becomes more and more detrimental. In the last few years, many experiments with tropical reef building corals have shown, that a lowering of the carbonate ion concentration significantly reduces calcification rates and therefore growth (e.g., Gattuso et al. 1999; Langdon et al. 2000, 2003; Marubini et al. 2001, 2002). In the middle of this century, many tropical coral reefs may well erode faster than they can rebuild. Cold-water corals are living in an environment (high geographical latitude, cold and deep waters) already close to a critical carbonate ion concentration below calcium carbonate dissolves. Actual projections indicate that about 70% of the currently known Lophelia reef structures will be in serious danger until the end of the century (Guinotte et al. 2006). Therefore L. pertusa was cultured at GEOMAR to determine its long-term response to ocean acidification. Our work has revealed that – unexpectedly and controversially to the majority of warm-water corals – this species is potentially able to cope with elevated concentrations of CO2. Whereas short-term (1 week) high CO2 exposure resulted in a decline of calcification by 26-29 % for a pH decrease of 0.1 units and net dissolution of calcium carbonate, L. pertusa was capable to acclimate to acidified conditions in long-term (6 months) incubations, leading to slightly enhanced rates of calcification (Form & Riebesell, 2012). But all these studies were carried out in the laboratory under controlled conditions without considering natural variability and ecosystem interactions with the associated fauna. Moreover, only very little is known about the nutrition (food sources and quantity) of cold-water corals in their natural habitat. In a multifactorial laboratory study during BIOACID phase II we could show that food availability is one of the key drivers that promote the capability of these organisms to withstand environmental pressures such as alterations in the carbonate chemistry and temperature (Büscher, Form & Riebesell, in prep.). To take into account the influences of natural fluctuations and interactions (e.g. bioerosion), we aim to merge in-situ results from the two research cruises POS455 and POS473 with laboratory experimental studies for a comprehensive understanding of likely ecosystem responses under past, present and future environmental conditions.

The main goal of MSM21/4 was the study of gas hydrate system off Svalbard. We addressed this through a comprehensive scientific programme comprising dives with the manned submersible JAGO, seismic and heat flow measurements, sediment coring, water column biogeochemistry and bathymetric mapping. At the interception of the Knipovich Ridge and the continental margin of Svalbard we collected seismic data and four heat flow measurements. These measurements revealed that the extent of hydrates is significantly larger than previously thought and that the gas hydrate system is influenced by heat from the oceanic spreading centre, which may promote thermogenic methane production and thus explain the large extent of hydrates. At the landward termination of the hydrate stability zone we investigated the mechanisms that lead to degassing by taking sediment cores, sampling of carbonates during dives, and measuring the methane turn-over rates in the water column. It turned out that the observed gas seepage must have been ongoing for a long time and that decadal scale warming is an unlikely explanation for the observed seeps. Instead seasonal variations in water temperatures seem to control episodic hydrate formation and dissociation explaining the location of the observed seeps. The water column above the gas flares is rich in methane and methanotrophic microorganisms turning over most of the methane that escapes from the sea floor. We also surveyed large, until then uncharted parts of the margin in the northern part of the gas hydrate province. Here, we discovered an almost 40 km wide submarine landslide complex. This slide is unusual in the sense that it is not located at the mouth of a cross shelf trough such as other submarine landslides on the glaciated continental margins around the North Atlantic. Thus, the most widely accepted explanation for the origin of such slides, i.e. overpressure development due to deposition of glacial sediments on top of water rich contourites, is not applicable. Instead we find gas-hydrate-related bottom simulating reflectors underneath the headwalls of this slide complex, possibly indicating that subsurface fluid migration plays a major role in its genesis., MARIA S. MERIAN-Berichte

Trondheim – (Kristiansund) – Kiel 08. – (25.) – 30.09.2011

Polycarpa urmeli sp. nov. (Figures 1, 2, 3) Material examined. One specimen (holotype): JAG" dive # 660, 18 November 1999 277 m on rocky ground off the southeast coast of the volcanic island Sangih��, northeast Indonesia (03��22.08��N, 125 ��31.19��E). This specimen is deposited in the Kamchatka Branch of the Pacific Institute of Geography (KBPIG), KBPIG 1 / 1356. Second specimen: from JAGO dive # 659, 17 November 1999 217 m on rocky ground off the northeast coast of Sangih�� Island (03��44.75��N, 125 ��25.19��E). Further material: In addition to the collected samples, numerous observations of live specimens of this species were made during a series of submersible dives performed along the North Indonesian Sangih�� Islands and the northern part of Sulawesi. A video camera mounted on the submersible��s manipulator arm provided detailed in situ video close-ups of the animals. The specimens were collected alive with the manipulator arm of the submersible and stored in a sampling tube for the rest of the dive. At the surface, they were transferred to a glass aquarium with fresh sea water for initial examination and measurement. They were then narcotized with magnesium-chloride and preserved in 3 % formalin mixed with sea water. Only one specimen (the holotype) has been examined anatomically, the second specimen kept intact. Description. Living specimens have an elongate and almost cylindrical body and are supported on a fleshy stalk arising from the antero-ventral part of the body (Fig. 1 A). Body and stalk are of about the same length. The body of the living holotype is 12 cm long and the stalk 14 cm. In preservative the body is about 10 cm long and 5 cm wide and the stalk 11.5 cm long and 2 cm diameter at the upper end just below the body, increasing to about 3 cm at the base. The stalk is attached to the substrate by a flat attachment area. In the living specimens, the body is orientated horizontally on the stalk with the dorsum uppermost. In preserved specimens, the stalk is bent dorsally (probably by contraction of its thick dorsal muscles) (Fig. 2 A). The tunic is thick, soft and transparent with a yellowish tint and a glassy transparent inner layer. The surface of the tunic is smooth (Fig. 1 B), but has shallow wrinkles when contracted (Fig. 3 A). Sparse minute elongate structures embedded in the superficial layer of the tunic are visible to the naked eye as black dots (Fig. 1 D). These are assumed to be epibionts (see below). Otherwise the surface of the tunic is naked, lacking either attached particles or hairs or other outgrowths. The free end of the body (its posterior end) is rounded. It has a well defined thick solid transverse posteroventral crest (resembling those of some species of Culeolus), that is visible on the photos of the living specimens and is conspicuous on the preserved specimen. The circular, branchial aperture is at the anterior end of the body close to the top of the stalk. Its margin is minutely dentate but it is not lobed (Fig. 2 A). The large transverse atrial aperture is halfway along the dorsal side of the body. It exposes a large part of the branchial sac when widely open in life (Fig. 1 C). It is bilabiate with an anterior and a posterior lip (Fig. 3 A). The body wall is thin and transparent and an extension of it filled by loose parenchymatous tissue (part of the haemocoele) projects down to the base of the stalk. The body muscles are composed of thick, primarily transverse bands forming a loose network. Some of the muscles that encircle the anterior end of the body continue into the stalk, where they form a wide ribbon running along its dorsal side and ending half way to its base. Circular muscles are crowded around the short siphons at both openings of the body. The holotype has about 40 large, laterally flattened, tapering tentacles of two different sizes arising just beyond the base of the thin branchial velum (Figs. 1 E, 2 B). The prepharyngeal band, consisting of two thick lamellae close to the ring of tentacles and the branchial sac, forms a dorsal V around the dorsal tubercle (Figs. 2 A, B). The dorsal tubercle has a U-shaped opening with two re-curved horns. The elongate ganglion is only slightly thicker than the pairs of anterior and posterior nerves that extend from it. The ganglion together with the neural gland is just posterior to the dorsal tubercle (Fig. 2 B). The dorsal lamina is a high membrane that has numerous long languets on its margin (Fig. 3 C). The four high branchial folds on each side, have numerous internal longitudinal vessels crowded on them. The branchial formula of the right side of the branchial sac is E 4 (12) 6 (12) 5 (13) 6 (16)DL. The perforations of the branchial wall are rather irregular, oval or rectangular and usually slightly elongate transversely (Fig. 3 B). Ciliated epithelium has not been detected lining these perforations. The simple wide gut loop occupies much of the left side of the body (Fig. 2 A) and is clearly visible through the transparent tunic in the living specimens. The oesophagus is of moderate length and bent at a right angle before it opens into the stomach. The elongate stomach occupies less than half of the ascending limb of the gut loop, is slightly wider than the intestine and has numerous internal longitudinal folds. The intestine is isodiametric along the whole length, terminating in an anus with a smooth border. The holotype emptied its intestine when it was transferred into the aquarium and now contains neither mud nor other particles. Gonads are numerous, about 60 on the right and 40 on the left, and are firmly attached to the body wall but not embedded in it. Most are in the anterior halves of each side of the body, where they form rather compact clusters, and often overlap each other (Fig. 2 A). On the left, six gonads are inside the primary gut loop and two are between the gut loop and the mid-ventral line of the body. Each gonad consists of a central ovary and numerous (sometimes more than 100) male follicles spread over the sides and mesial surface, but not beneath the ovary. Male ducts curve around each side of the ovary, run along its mesial surface and occasionally join together to meet the vas deferens of variable length (Fig. 2 D) that opens at the base of the short oviduct. The gonads are aligned towards the atrial aperture. Several low fleshy endocarps are attached to the body wall along the intestine inside the gut loop (Fig. 2 A). Endocarps are not present outside the gut loop. Observations on the living animals. Habitat and abundance: Specimens of Polycarpa urmeli sp. nov. were sighted during submersible dives to between 50 and 400 m water depth around north Indonesia in November 1999. They occurred only sporadically and scattered over large areas. Only one aggregation of 10 individuals, separated by several meters from each other, was found at 237 m depth off Bunaken island. Specimens were present off the islands Sangih��, Mahengetang, Siau, Manado Tua, Bunaken and off the north coast of the northern arm of Sulawesi at water depths between 217 and 277 m and in water temperatures ranging from 12���16 ��C. They were not found in the Gulf of Tomini along the south coast of the northern arm of Sulawesi. Exploratory dives to determine the upper and lower depth limits of the species were not carried out. Most animals were sighted between 220 and 230 m. They were seen to have settled on open slopes mainly with rocky substrate, and were exposed to bottom currents that could reach 1 ���1.5 m/s, sometimes as strong surges that swayed the animals back and forth. Polycarpa urmeli lives in an environment with constant or frequent bottom currents and seems to be well adapted to these conditions. When the large branchial aperture is facing towards the current and both apertures are open wide, a large amount of water can pass through the animal without needing cilia to create a flow. This implies that species like P. u r m e l i with non-ciliated stigmata and large branchial perforations only occur in areas of continuous and strong bottom currents. Many deepwater species lack cilia and many of these are large, solitary and typically possess a peduncle arising close to the large branchial opening. The lack of food in their deep water habitats appears to be compensated for by the large amount of water passing through the animal to maximize the volume of microparticles filtered from it by the fine mucus net on the branchial sac. Monniot and Monniot (1978, p. 200) suppose that "the energy required for this form of nutrition would be minimal". Behaviour: Polycarpa urmeli sp. nov. is highly flexible on its fleshy stalk, which lifts the animal about 10 cm above the sediment and into the current. All animals observed had their large branchial apertures facing the current. Strong surging currents that transport a lot of sediment particles, sometimes caused the animals to close both apertures by contraction, and to lower the free (posterior) end of the body towards the substrate. However, this posture was also sometimes observed when there was no current. Individuals also responded to direct tactile contact by contraction of the apertures. Commensals: A diversity of commensals were observed on the outside of the tunic and inside the peribranchial cavity of several P. u r m e l i individuals. Small specimens of sea cucumbers (Holothuroidea), brittle- (Ophiuroidea) and feather-stars (Crinoidea), topshells (Trochidea) and spider crabs (Maiidae) moved around on the ascidians and their stalks (Fig. 1 H). The filter-feeders among these animals used their host to gain elevation for better exposure to the current, others probably fed on detritus particles and micro-organisms that occurred on the tunic. A tiny benthic ctenophore with long extended tentacles (Order Platyctenidae, probably Lyroctenidae) was also found on one P. u r m e l i specimen. Another P. u r m e l i carried piggyback between the two body openings a transparent sessile ascidian with cylindrical siphons (Fig. 1 F). Several P. u r m e l i individuals contained a single or a pair of shrimps. The small shrimps moved around on the outside of the branchial sac, climbed in and out of the peribranchial cavity at the artial aperture, and seemed to be well adapted to their host. One P. u r m e l i specimen contained a small eel (most likely a young conger eel) that probably got trapped in the peribranchial cavity by accident (Fig. 1 G). The holotype contained in its peribranchial cavity a symbiotic nemerthean worm which appeared to be an undescribed species belonging to the genus Gononemertes (pers. comm. Alexei Chernyshev, Valdivostok). Two Gononemertes species are known from ascidians of the genus Pyura and Phallusia (see Dalby 1995). The minute hairs visible on the tunic of some living specimens of P. u r m e l i (Fig. 1 E) are assumed to be epibionts. Microscopic examination of the tunic revealed these to be short cylindrical bodies completely embedded in the peripheral layer of the tunic. They appear to contain tentacle-like structures which in life could be expanded to the exterior giving an impression of hairs. Remarks. Several features of this Polycarpa species, including the absence of the ciliated stigmata and the toothed dorsal lamina, have not been reported for Polycarpa before. The structure of the pharyngeal wall is intermediate between the branchial wall of typical Styelidae and the deep-water genus Bathyoncus. However, the type species of the genus Bathyoncus, B. mirabilis Herdman, 1882, has only one voluminous gonad on each side of the body and may have affinities with the styelid genus Cnemidocarpa. Nevertheless its branchial wall, like that of Culeolus, is lost, leaving large rectangular meshes formed by longitudinal branchial vessels crossing transverse sinuses. In the present Polycarpa species the branchial wall persists and is perforated by irregular unciliated perforations probably derived from true stigmata by losing cilia and uniting adjacent stigmata into larger perforations. This may be an adaptation to deep water conditions and feeding by 'passive' filtration (see below). Such unciliated perforations are known in Pterygascidia mirabilis Sluiter, 1904 (see Kott in press) and in several other deep-water species belonging to genera in which most other species have typical ciliated stigmata (e.g. Distomus pacificus Monniot and Monniot, 1991, Monandrocarpa abyssa Sanamyan and Sanamyan, 1999). Bathyoncus arafurensis Monniot and Monniot, 2003, has a denser branchial sac and, unlike B. mirabilis, numerous polycarps and its assignment to the genus Bathyoncus is not well established. The present species is not closely related to any of the more than 120 Polycarpa species. The preserved specimens resemble superficially P. c l a v a t a Hartmeyer, 1919 (especially as figured by Kott 1985, Fig. 71 a), which also has a thick stalk inserted to the anterior end of the body. However, endocarps of P. clavata are spread over the whole body wall, and gonads and the shape of the gut loop differ significantly from those of P. urmeli. Living specimens of P. clavata are brillant orange to yellow in colour and the tunic of the species is thick and quite firm. Sympatric species. Four other stalked solitary ascidians were observed during the JAGO dives in northern Indonesia. The first was a transparent species of similar size and body shape like Polycarpa urmeli, except the free (posterior) end of its body was slightly flattened and rectangular and the atrial aperture was not in the middle of the body but slightly closer to the branchial aperture (Fig. 4 A). This transparent species occurred in the same habitat as P. u r m e l i. The second ascidian species appeared to be Pterygascidia mirabilis Sluiter, 1904 (family Ciallusiidae, see Kott in press) and was encountered at 253 m at the north coast of Sulawesi (Fig. 4 B). The branchial and atrial apertures of this species were both close together at the free end of the transparent elongated body. The siphon of the dorsal branchial aperture had the shape of a hood. The opening of the hood was facing the current that flows from the stalk along the elongated body. The atrial aperture had a ventral lobe and was facing down-current. The genus Pterygascidia is monotypic and known from the Philippines, Indonesia and the northwestern Australian continental shelf (Kott in press). The third ascidian species belonged to the genus Culeolus, probably C. herdmani Sluiter, 1904. Members of this genus have an extraordinarily long thin stalk, much longer than the body itself and a wide-meshed branchial sac which is reduced to the network of longitudinal and transverse vessels, the branchial wall having disappeared. The Culeolus specimen was encountered at 220 m depth at the Mahengetang submarine volcano. The fourth species belonged to the family Octacnemidae which is exclusively known from deeper waters and mainly characterized by the hypertrophy of the oral siphon. One specimen of this family was found at 270 m depth off Lembeh Island at the south coast of northern Sulawesi. The oral siphon of the pale yellowish species was greatly enlarged to form a large basket or hood (Fig. 4 C,D). The outer edge of this basket was undulated and rose-colored allaround like roughed lips. Also the inside of the basket around the opening to the branchial sac was rose-colored. An elongated prominent atrial siphon pointing vertically upwards opened at the antero-dorsal part of the body. The short thick stalk extended at the antero-ventral corner. The animal oriented the aboral surface of the oral basket to the on-coming bottom current, i.e. the oral opening of the body was facing down-current, as also observed for Megalodicopia hians Oka 1918 (Okuyama et al. 2002; pers. comm. Edward Seidel, Monterey Bay Aquarium). Members of this family, like Megalodicopia hians, are macrophagous and engulf large particles and organisms such as small invertebrates, whereas others, like the two genera Dicopia and Situla, have probably a mixed diet and feed on both large and tiny particles (Monniot & Monniot 1975). Ethymology. The species name refers to the shape of the main body that resembles the head of a puppet dinosaur called ���Urmel���, the main character of a famous puppet show broadcasted in the German Television in 1969., Published as part of Sanamyan, Karen & Hissmann, Karen, 2008, A new stalked species of Polycarpa (Tunicata: Ascidiacea) from deeper waters of the tropical Western Pacific and in situ observations on sympatric species, pp. 41-49 in Zootaxa 1744 on pages 42-48, DOI: 10.5281/zenodo.181612, {"references":["Monniot, C. & Monniot, F. (1978) Recent work on the deep-sea tunicates. Oceanography and Marine Biology: An Annual Review, 16, 181 - 228.","Herdman, W. A. (1882) Report on the Tunicata collected during the voyage of H. M. S. Challenger during the years 1873 - 1876, part 1, Ascidiae simplices. Report of the scientific results of the voyage of H. M. S. Challenger during the years 1873 - 76, 6 (17), 1 - 296.","Sluiter, C. P. (1904) Die Tunicaten der Siboga-Expedition Pt. I, Die socialen und holosomen Ascidien. Siboga Expeditie, 56 A, 1 - 126.","Monniot, C. & Monniot, F. (1991) Tunicata: Peuplement d'ascidies profondes en Nouvelle-Caledonie. Diversite des strategies adaptatives, in A. Crosnier (ed.), Resultats des Campagnes Musorstom, 8, Memoires du Museum National d'Histoire Naturelle, (A) 151, 357 - 448.","Sanamyan, K. & Sanamyan, N. (1999) Some benthic Tunicata from the southern Indo-Pacific Ocean. Journal of Natural History, 33, 1835 - 1876.","Monniot F., & Monniot, C. (2003) Ascidies de la pente externe et bathyales de l'ouest Pacifique. Zoosystema 25 (4), 681 - 749.","Hartmeyer, R. (1919) Ascidien. In Results of Dr. E. Mjobergs Swedish scientific expeditions to Australia 1910 - 13. Kungliga Svenska Vetenskapsakademiens Handlingar, 60 (4), 1 - 150.","Kott, P. (1985) The Australian Ascidiacea part 1, Phlebobranchia and Stolidobranchia. Memoirs of the Queensland Museum, 23, 1 - 440.","Oka, A. (1918) Megalodicopia hians n. g., n. sp., eine sehr merkwurdig ascidie aus dem japanischen Meere. Annotationes Zoologicae Japonenses, 9 (4), 399 - 406.","Okuyama, M., Saito, Y., Ogawa, M., Takeuchi, A., Jing, Z., Naganuma, T. & Hirose, E. (2002) Morphological studies on the bathyal ascidian, Megalodicopia hians Oka 1918 (Octacnemidae, Phlebobranchia), with remarks on feeding and tunic morphology. Zoological Science, 19, 1181 - 1189.","Monniot, C. & Monniot, F. (1975) Abyssal tunicates: an ecological paradox. Annales de l´Institut oceanographic, Paris, 51 (1), 99 - 129."]}

The deep demersal fish fauna at depths of 100–400min canyons off the St Lucia Marine Protected Area along the north coast of KwaZulu-Natal is compared with similar fish communities at the Comoro Islands and in the Indo-Pacific region. Fifty-four fish species were seen or photographed from the submersible Jago or by the discovery team of scuba divers in the coelacanth, Latimeria chalumnae, habitat of the canyons off Sodwana Bay. An additional 94 fish species known from depths of 100–200 m along the coast of northern KwaZulu-Natal are likely to occur in the canyon habitat. The fish fauna of the Sodwana canyons shares at least 18 species with the deep demersal fish community off tropical coral reefs of the Indo-Pacific region. Thirty-seven of the Sodwana canyon fishes are also known from the coelacanth habitat in the Comoros.

Using the manned submersible Jago, the habits, distribution and number of coelacanths within all main submarine canyons of the Greater St Lucia Wetland Park were studied during 47 survey dives, with a total bottom time of 166 hours at depths ranging from 46 to 359 m, between 2002 and 2004. Twenty-four individuals were positively identified from three of the canyons, primarily from inside caves at or close to the canyon edges at depths of 96-133 m with water temperatures between 16 and 22.5oC. The population size of coelacanths within the canyons is assumed to be relatively small; coelacanths are resident but not widespread nor abundant within the park.

High-temperature (250°C) hydrothermal vents and massive anhydrite deposits have been found in a shallow water, sediment-filled graben near 66°36′N in the Tjornes Fracture Zone north of Iceland. The site is located about 30 km offshore, near the small island of Grimsey. The main vent field occurs at a depth of 400 m and consists of about 20 large-diameter (up to 10 m) mounds and 1–3 m chimneys and spires of anhydrite and talc. A north–south alignment of the mounds over a 1-km strike length of the valley floor suggests that their distribution is controlled by a buried fault. Widespread shimmering water and extensive white patches of anhydrite in the sediment between the mounds indicates that the entire 1-km2 area occupied by the vents is thermally active. A 2-man research submersible JAGO was used to map the area and to sample vent waters, gases, and chimneys. Actively boiling hydrothermal vents occur on most of the mounds, and extensive two-phase venting indicates that the field is underlain by a large boiling zone (200×300 m). The presence of boiling fluids in shallow aquifers beneath the deposits was confirmed by sediment coring. The highest-temperature pore fluids were encountered in talc- and anhydrite-rich sedimentary layers that occur up to 7 m below the mounds. Baked muds underlie the talc and anhydrite layers, and pyrite is common in stockwork-like fractures and veins in the hydrothermally altered sediments. However, massive sulfides (pyrite–marcasite crusts) were found in only one relict mound. Subseafloor boiling has likely affected the metal-carrying capacity of the hydrothermal fluids, and deposition of sulfides may be occurring at greater depth. Although the mounds and chimneys at Grimsey resemble other deposits at sedimented ridges (e.g. Middle Valley, Escanaba Trough, Guaymas Basin), the shallow water setting and extensive boiling of the hydrothermal fluids represent a distinctive new type of seafloor hydrothermal system.

General Subject of research: Detailed study of the shallow water hydrothermal system around Kolbeinsey and Grimsey islands