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In situ observations of predatory feeding behaviour of the galatheid squat lobster Munida sarsi using a remotely operated vehicle
No full textThe feeding behaviour of a deep-sea holothurian, Stichopus tremulus (Gunnerus) based on in situ observations and experiments using a Remotely Operated Vehicle
No full textUsing a Remotely Operated Vehicle (ROV) to deploy an in situ cage experiment
incorporating fluorescent Luminophore particle tracers, the gut throughput time of the deposit feeding holothurian, Stichopus tremulus (Gunnerus) was determined as 23.73 h (S.D.F2.3). For a range of individuals examined at different depths (350–500 m) and locations, throughput times varied between 19 and 26 h irrespective of animal size or gut tract length. In situ video observations of feeding behaviour showed that this species uses fine oral papillae in a ‘sweeping’ motion to target particles on the seafloor. Following detection of a food source fine-branched digitate tentacles collect a large range of sediment fragments from the seabed. The main types of particles ingested include silica fragments ( < 20 > 500 Am), pelagic foraminifera, benthic
foraminifera, fine phytodetrital remains and occasional larger rock fragments (f1 cm). Ingested sediment consisted mainly of very fine silica fragments (f50 Am) accounting for over 50% of the total gut contents. Frame-by-frame video analysis revealed that the particle handling time (i.e. the time taken for a tentacle insertion and the subsequent collection of food) was found to be f54 s. Only 10 of the 20 feeding tentacles were simultaneously employed during feeding. Use of tentacles appeared to be in sequence, alternating between the reserve and active tentacles. Estimating the rate of movement over the seabed and the total effective capture area of each tentacle, the impact of this animal on the turnover and quality of surface sediment at this deepwater site is potentially substantial. The in situ experiments provided a significant improvement over previous methods used to investigate deep-sea deposit feeders and represent a useful concept for further in situ deep-sea research using an industrial ROV
A review of the uses of work-class ROVs for the benefits of science: lessons learned from the SERPENT project
No full textThis paper reviews the contributions of underwater science in continuing to develop new technology to explore the marine environment and how collaborations taking place between the oil and gas industry and science are facilitating this process. A case study focuses on some of the results and highlights from the SERPENT Project. SERPENT (Scientific and Environmental ROV Partnership using Existing Industrial Technology) is a collaboration programme that was designed to make better use of remotely operated vehicle (ROV) technology and data available through links with marine operations in the oil and gas industry. Oil and gas exploration and production activities in the marine environment are increasing. The amount of global hydrocarbon reserves removed from below the seafloor is set to increase over the next 5–10 years with exploration heading into deeper, more remote waters, many of which have yet to be fully explored. The only way that these remote areas may be documented is through a working relationship with industry, with mutual benefit for both sides, and learning from technology that is already in place for the benefit of science
Reproductive biology of the abyssal holothurian Amperima rosea: an opportunistic response to variable flux of surface derived organic matter?
No full textA radical change in the abundance of invertebrate megafauna has occurred over a vast area of the Porcupine Abyssal Plain, north-east Atlantic, in recent years. In particular, the holothurian Amperima rosea has increased in abundance by three orders of magnitude. The sudden increase in abundance of A. rosea appears to be the result of environmental forcing rather than localized stochastic population variations. Amperima rosea produces small eggs ([less-than-or-eq, slant]200 [mu]m) indicating (1) planktotrophic larval development or (2) lecithotrophic larval development with an abbreviated larval stage. It also reaches maturity at a very small size. The reproductive biology of A. rosea indicates that it can increase rapidly in population size and can colonize large areas quickly. It has high fecundity, as predicted by gonad indices and observed in histological studies. Fecundity was greater in winter than in summer months, but there was no clear evidence of seasonal or episodic reproductive events. All males, irrespective of sample season or year, were mature with spermatozoa. Most oocytes were of an intermediate size (70 to 120 [mu]m), either at the late previtellogenic (70–90 [mu]m) or early vitellogenic (100–120 [mu]m) stage of development. It is postulated that development of full vitellogenesis, leading to episodic spawning, might be dependent on certain environmental stimuli. The most likely stimulus is food supply. Amperima rosea has been shown to feed preferentially on phytodetritus and to have a requirement for certain sterols in its diet. Qualitative changes in the flux of organic matter to the sea-floor may control vitellogenesis and fecundity, and hence have an effect on the population dynamics of the species
Seasonality and selectivity in the feeding ecology and reproductive biology of deep-sea bathyal holothurians
No full textChlorophyll and carotenoid pigments were determined from the gut sediments of five species of bathyal holothurian in the NE Atlantic, sampled shortly after the spring/summer phytoplankton bloom in 2001 and prior to the spring bloom in 2002. Three species, Laetmogone violacea, Paroriza pallens and Bathyplotes natans, sampled within a similar depth range (900–1100 m) in the summer of 2001 showed significant differences in their chlorophyll and carotenoid pigment concentrations. This suggests they may select for slightly different components from the available food resource. Four species sampled in early spring 2002, Laetmogone violacea, Paroriza pallens, Benthogone rosea and Benthothuria funebris, also had significant differences in their pigment concentrations. These species were sampled over a wider depth range (1000–3100 m) showing a bathymetric trend in pigment concentrations. There was a distinct seasonal change in the composition and concentration of the pigments, linked to a reduction in the availability of fresh organic material during autumn and winter periods.Ovarian tissue was also examined. The carotenoid pigments found in the ovary also occurred in the OM ingested by the holothurians. The dominant gonadal carotenoid pigments were beta-carotene, echinenone and zeaxanthin. The potential for using these carotenoids to gain a competitive advantage through selectivity of chlorophyll and carotenoid pigment biomarkers are discussed in relation to competition for food resources by deposit-feeders. The results were also compared with selectivity in abyssal species
Inter-annual variability and potential for selectivity in the diets of deep-water Antarctic echinoderms
No full textThe continental shelf of the West Antarctic Peninsula (WAP) is a highly productive region but also unusually deep as a result of isostatic depression by the polar ice cap. The close coupling of surface processes with those of the benthos would be expected in such a seasonally variable environment; however, the cold, deep conditions of the WAP shelf may allow for the persistence of organic material in the sediments as a “food bank”. Chlorophyll and carotenoid pigments were determined from the gut contents of seven species of echinoderm and from the surficial sediment on the bathyal continental shelf. Samples were collected as part of the FOODBANCS programme during successive cruises in austral spring (October 2000) and austral autumn (March 2001). Pigments were identified and quantified using reverse-phase high-performance liquid chromatography (HPLC). A lack of qualitative selectivity was observed among species, compared to that observed for deep-water assemblages at temperate latitudes, supporting the theory of a persistent “food bank”. However, significant quantitative differences were observed among species and between years and sampling location on the shelf. Species differences were marked between those we classified as “true” deposit feeders and those species whose diet also may be supplemented by scavenging and/or grazing
Abyssal scavenging demersal fauna at two areas of contrasting productivity on the Subantarctic Crozet Plateau, southern Indian Ocean
No full textThe Crozet Plateau is situated below typical high-nutrient, low-chlorophyll (HNLC) waters of the southern Indian Ocean. The area to the east of the Crozet Islands experiences high levels of surface productivity during the austral summer due to natural iron enrichment from terrestrial sources and favourable light conditions. The demersal scavenging fauna at two areas of contrasting productivity, to the east and south of the islands, were investigated using two landers equipped with baited cameras and traps. Five species of scavenging fish were observed along with five groups of invertebrates during a single deployment of the RObust BIOdiversity (ROBIO) lander. Further deployments of the Fish RESPirometry (FRESP) video lander yielded no additional scavenging fish species. A modelled arrival and departure curve for the abyssal grenadier Coryphaenoides armatus suggests a region of low food availability compared to other regions worldwide. The ROBIO-derived abundance estimate for C. armatus of 187 ind. km–2 is comparable with published trawl-derived estimates. Significantly more amphipods were collected to the south of the islands, which was subject to lower organic matter supply. Reasons for this are unknown but may be due to differing current direction/velocities, or increased fish predation at the enriched site. The numerically dominant amphipod species present was Paralicella caperesca, followed by Eurythenes gryllus and Orchomenella gerulicorbis. A further five species were observed in low numbers, some occurring only once. One, Paracallisoma sp. nov, was a new species
Feeding behaviour of deep-sea dwelling holothurians: inferences from a laboratory investigation of shallow fjordic species
No full textAn experimental mesocosm was used to investigate the feeding behaviour, particle size selectivity, gut throughput time and dietary selection of two holothurian species, Stichopus tremulus (Gunnerus) and Mesothuria intestinalis (Ascanius). Specimens usually only present at depths > 1000m in the North-eastern Atlantic Ocean were collected from a relatively shallow (< 100 m) cold-water fjordic system in Sweden and maintained in the laboratory. Both species exhibited a similar strategy for retrieving sediment particles from the sediment surface; feeding tentacles were used in a ‘grasping’ motion to pick up sediment particles. The rate at which the feeding tentacles were placed onto the sediment surface, however, differed between species (S. tremulus was three times quicker than M. intestinalis) resulting in a significant difference in gut throughput time. Both species, when offered different sized sediment particles, showed a preference for finer sediment and for nutritionally rich, pigment-enhanced, food patches. <br/
Mass deposition of jellyfish in the deep Arabian Sea
Full text linkIn December 2002 large numbers of dead jellyfish, Crambionella orsini (Vanhöffen 1888), were observed on the seabed over a wide area of the Arabian Sea off the coast of Oman, at depths between 350 and 3300 m. Moribund jellyfish were seen tumbling down the continental slope. Large aggregations of dead jellyfish were evident within canyons and on the continental rise. At the deepest stations, patches of rotting, coagulated jellyfish occurred. The patches were several metres in diameter, at least 7 cm thick and covered about 17% of the sediment surface. At other locations on the continental rise the seafloor was covered in a thin, almost continuous, layer of jelly “slime,” a few millimetres thick, or was littered with individual jellyfish corpses. Photographic transects were used to estimate the amount of carbon associated with the jelly detritus. The standing stock of carbon varied between 1.5 and 78 g C m-2, the higher figure exceeding the annual downward flux of organic carbon, as measured by sediment traps, by more than an order of magnitude. The episodic nature of jellyfish blooms, which may be modulated by global change phenomena, provides a hitherto unknown mechanism for large-scale spatial and temporal patchiness in deep-sea benthic ecosystems
Temporal variability in phytodetritus and megabenthic activity at the seabed in the deep northeast Atlantic
No full textWe report a ten-year study of the abundance and activity of megabenthos on the Porcupine Abyssal Plain, northeast Atlantic, together with observations on the occurrence of phytodetritus at the deep-sea floor (4850 m). Using the Southampton Oceanography Centre time-lapse camera system, ‘Bathysnap’, we have recorded a radical change in the abundance and activity of megabenthos between the two periods of study (1991–1994 and 1997–2000). In 1991–1994, the larger megabenthos occurred at an abundance of c. 71.6/ha and were dominated by large holothurians. In addition, there were very substantial populations of smaller megabenthic ophiuroids (c. 4979/ha). Together, the total megabenthos are estimated to track over some 17 cm2/m2/d (exploiting 100% of the surface of the seabed in c. 2.5 years). In 1997–2000, the larger megabenthos increased to an abundance of c. 204/ha and were joined by exceptional numbers of a small holothurian species (Amperima rosea, 6457/ha) and ophiuroids (principally Ophiocten hastatum, 53,539/ha). The total megabenthos population was tracking at an estimnated rate of c. 247 cm2/m2/d (exploiting 100% of seabed in just 6 weeks). Coincident with these increases in the abundance and activity of the megabenthos, there were apparently no mass depositions of aggregated phytodetritus to the seabed in the summers of 1997–1999. Mass occurrences of phytodetritus had been noted during the summer months of the three years previously studied (1991, 1993 and 1994), with covering between 50 and 96% of the sediment surface. There is a statistically significant (p<0.02) negative correlation between maximum extent of this seabed cover of phytodetritus and seabed tracking by megabenthos. Additional studies [Lampitt et al., Progr. Ocean. 50 (2001)], indicate that there were no substantial changes in surface ocean primary productivity, in export flux, or in the composition of the flux that might otherwise account for the apparent absence of observable concentrations of phytodetritus during the summers of 1997–1999. We postulate that the marked increase in megabenthic tracking activity resulted in the removal (via consumption, disaggregation, burial etc.) of the bulk of the incoming phytodetrital flux during these years. A simple conceptual model, based on the apparent phytodetrital fluxes observed in 1991 and 1993, suggests that the megabenthos tracking rates estimated for 1997–1999 are sufficient to account for near-total removal of this flux. However, we are not able to estimate other processes removing phytodetritus (i.e. other elements of the benthos) that may also have increased between 1991–1994 and 1997–1999. Other independent studies [e.g. Ginger et al., Progr. Ocean. 50 (2001)] of flux constituents support the possibility that just a few species of megabenthos (e.g. A. rosea, and O. hastatum) could well have consumed a major proportion of the incoming flux and so substantially modified the composition of the organic matter available to other components of the benthos
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