long term benthic infaunal monitoring at a deep ocean dredged material disposal site off northern california abstract one hundred and thirty five benthic infaunal samples were collected from the san francisco deep ocean disposal site sf dods over a 10 year period from january 1996 to september 2004 each sample was 0 1 m2 cut to a depth of 10 cm and sieved through a 300 m mesh a total of 810 species of benthic invertebrates were identified the majority of taxa 65 4 new to science the fauna represents a rich lower slope infaunal assemblage that rivals similarly studied locations in the western north atlantic no regional impact or degradation of benthic infauna due to dredged material disposal was detected all reference stations and stations on the site boundary maintained high species richness and diversity during the monitoring period exceptions included an occasional sample with anomalously high numbers of one or two species that reduced the diversity and or equitability within sf dods species richness and diversity were often reduced stations within the disposal site were recolonized by the same taxa that normally occurred in adjacent reference areas initial colonizers of fresh dredged material included spionid and paraonid polychaetes that were typical dominants at the site at least one polychaete species ophelina sp 1 sometimes colonized dredged materials containing coarse sand one sample at station 13 located in the middle of sf dods september 2002 contained 57 species of benthic invertebrates suggesting that colonization of fresh dredged material is rapid it seems unlikely that larval dispersal and settlement account for this rapid recolonization therefore it is postulated that adult organisms from adjacent areas move to the disturbed sites via boundary layer currents the steep continental slope adjacent to sf dods is subject to turbidity flows and the resident fauna are likely pre adapted to rapidly colonize disturbed sediments larval dispersal especially by spionid polychaetes such as prionospio delta may also be important in colonizing newly deposited sediments subtle year to year shifts in faunal assemblages were evident at stations on the boundary of sf dods at these stations species richness and diversity remained high but numerically dominant taxa differed possibly due to changes in sediment grain size associated with the dredged material however some year to year changes appeared to be regional in nature large epifaunal organisms such as the elasapoid holothurian scotoplanes globosa appeared to be locally important in modifying surficial sediments it moves through the sediment like a bulldozer disturbing the surface and disrupting resident infauna as it ingests sediment other deposit feeding holothurians such as ypsilothuria bitentaculata were found throughout the study area including sediments with fresh dredged material a long narrow bodied tube like agglutinated foraminiferan of the genus bathysiphon is commonly found in sediments containing dredged material this foraminiferan is poorly understood but may be opportunistic on soft dredged material

sedimentation of biogenic constituents during the last century in western bransfield and gerlache straits antarctica a relation to currents primary production and sea floor relief abstract as part of the fruela experiment 11 sediment cores were recovered from the bellingshausen sea the western bransfield and gerlache straits antarctic peninsula to determine the spatial distribution of organic carbon oc biogenic silica bsi and nitrogen n in the sediment under regions of known irregular primary production rates pprs oc bsi and n contents ranged from 0 3 to 1 2 from 5 7 to 20 4 and from 0 03 to 0 17 respectively apparent mean sediment accumulation rates sars varied between 0 25 and 3 11 mm year 1 220 and 1750 g m 2 year 1 central gerlache and western bransfield straits the orleans canyon had the highest biogenic constituents contents and sediment accumulation rates whereas the northern coast off snow island bellingshausen sea showed the lowest values central gerlache strait with the highest primary production rates in the study area was the only region where the oc and bsi contents in the sediment corresponded to the photosynthetic activity in the euphotic zone above it at the extremes of gerlache strait as in western bransfield strait sediment focusing by currents enhanced by depressions in the sea floor contributed to develop regions with high biogenic constituent concentrations whereas at the bellingshausen sea and western gerlache strait winnowing by currents may drift away the biogenic material exported from the euphotic zone apparently bottom relief and currents rather than solely depth determined the modern distribution and accumulation rates of biogenic particulate matter in the study area paleoceanographic interpretations of the sedimentary record from antarctic marginal seas such as gerlache and bransfield straits should consider that focusing due to lateral transport and sea floor morphology and the preferential degradation of oc relative to bsi may increase to an important degree the biogenic contents in the sediment especially the opal oc and bsi accumulation in antarctic marginal seas could be as important as the broad continental shelves despite large spatial differences

a lower cretaceous ichthyosaur graveyard in deep marine slope channel deposits at torres del paine national park southern chile remnants of ophthalmosaurid ichthyosaurs recently discovered in the vicinity of the tyndall glacier in the torres del paine national park of southern chile are extremely abundant and well preserved after three field campaigns to the area a total of 46 articulated and virtually complete ichthyosaur specimens both adults and juveniles were tentatively assigned to four different species of ophthalmosauridae preservation is excellent and occasionally includes soft tissue and embryos the skeletons are associated with ammonites belemnites inoceramid bivalves and fishes as well as numerous plant remains the enormous concentration of ichthyosaurs is unique for chile and south america and places the tyndall locality among the prime fossil lagerstatten for early cretaceous marine reptiles worldwide the deposit is early cretaceous valanginian hauterivian in age and forms part of a monotonous bathyal to abyssal sequence of the late jurassic to late early cretaceous rocas verdes back arc basin in this region the tyndall ichthyosaur population may have profited from cold upwelling currents that caused abundant life at the shelf edge including masses of belemnites and small fish the preferred diet of ichthyosaurs the abundance of almost completely articulated ichthyosaur skeletons in the tyndall area suggests that some animals fell victim to episodic mass mortality events caused by turbidity currents traveling downslope through a submarine canyon they lost orientation drowned and were dragged into the deep sea by these turbulent high energy gravity flows their bodies ended up in an oxygen deficient basin environment where they were immediately embedded by the fine turbidite suspension fallout the tyndall ichthyosaur locality thus combines characteristics of both concentration and conservation lagerstatten

distribution abundance and trail characteristics of acorn worms at australian continental margins abstract acorn worms enteropneusta which were previously thought to be a missing link in understanding the evolution of chordates are an unusual and potentially important component of many deep sea benthic environments particularly for nutrient cycling very little is known about their distribution abundance or behaviour in deep sea environments around the world and almost nothing is known about their distribution within australian waters in this study we take advantage of two large scale deep sea mapping surveys along the eastern northern lord howe rise and western continental margins of australia to quantify the distribution abundance and trail forming behaviour of this highly unusual taxon this is the first study to quantify the abundance and trail behaviour of acorn worms within australian waters and provides the first evidence of strong depth related distributions acorn worm densities and trail activity were concentrated between transect averaged depths of 1600 and 3000 m in both eastern and western continental margins the shallow limit of their depth distribution was 1600 m the deeper limit was less well defined as individuals were found in small numbers below 3000 down to 4225 m this distributional pattern may reflect a preference for these depths possibly due to higher availability of nutrients rather than a physiological constraint to greater depths sediment characteristics alone were poor predictors of acorn worm densities and trail activity high densities of acorn worms and trails were associated with sandy mud sediments but similar sediment characteristics in either shallower or deeper areas did not support similar densities of acorn worms or trails trail shapes varied between eastern and western margins with proportionally more meandering trails recorded in the east while spiral and meandering trails were both common in the west trail shape varied by depth with spiral shaped trails dominant in areas of high acorn worm densities 2000 3000 m water depth while meandering trails were common over a much broader depth range and were the only trails recorded in deep environments 3000 m while species specific patterns may in part explain these differences evidence suggests that nutrient availability is also likely to be an important driving factor supporting the hypothesis put forward by smith et al 2005 that acorn worms meander when searching for food and form a spiral when feeding in a nutrient rich area

spatial and temporal patterns of benthic macrofaunal communities on the deep continental margin in the gulf of guinea abstract density taxonomic composition at higher taxon level and vertical distribution of benthic macrofaunal communities and sediment characteristics pore water nitrogen organic carbon sulfur c n ratio n alcohol biomarkers were examined at three deep sites on the congo gabon continental margin this study was part of the multidisciplinary biozaire project that aimed at studying the deep benthic ecosystems in the gulf of guinea sampling of macrofaunal communities and of sediment was conducted during three cruises january 2001 december 2001 and december 2003 at two downslope sites 4000 m depth one located near the congo submarine channel 15 km in the south and the other one far from the channel 150 km in the south the third area located 8 km north of the congo channel in the surroundings of a giant pockmark at 3160 m depth was sampled during one cruise in december 2003 at these three locations the macrofaunal communities presented relatively high densities 327 987 ind 0 25 m 2 compared with macrofaunal communities at similar depths that is due to high levels of food input related to the congo river and submarine system activities that affect the whole study area the communities were different from each other in terms of taxonomic composition at higher taxon level phylum class order for all the groups except for the polychaetes classified into families the polychaetes dominated the communities and were responsible for the increase in densities observed at both deep sites 4000 m between january 2001 and december 2003 whereas the tanaidaceans the isopods and the bivalves were the other most abundant taxa responsible for the spatial differences between these sites the community at 3150 m differed from the two deep communities by higher abundances in bivalves nemerteans and holothuroids the composition of the polychaete community also differed among sites in the vicinity of the congo channel the expected positive effect of the additional organic matter transported through the turbiditic currents on to the surrounding benthic communities was not observed as the increase in densities during the study period was higher at the site located away from the congo channel than near the channel 80 vs 30 that may be due to the low food value of the organic matter of terrestrial origin carried through the turbidites and or to the disturbance caused by these turbidites conversely far from the channel the macrofaunal communities benefit from organic matter of higher energetic value originating mainly from marine sources but also from continental sources carried by the congo plume or by near bed currents across or along the continental slope spatial and temporal variability in trophic and physical characteristics of the sediment habitat at both deep sites also affected the vertical distribution of the macrofaunal communities the activities of the very active congo system structure the deep macrofaunal communities on a large area in terms of densities composition and vertical distribution the food input is enhanced at regional scale as well as the heterogeneity of the sediment characteristics mainly in terms of organic matter quality marine vs terrigenous in turn the densities are enhanced as well as the regional diversity of the macrofaunal communities in terms of taxonomic composition and distribution

benthic prokaryotic community dynamics along the ardencaple canyon western greenland sea abstract the ardencaple canyon emanating from the eastern greenland continental rise over a distance of about 200 km towards the greenland basin was investigated to determine the effect of enhanced down slope transport mechanisms on deep sea benthic prokaryotic communities the concentration of viable bacterial cells live dead baclight and prokaryotic incorporation rates 3 h thymidine 14 c leucine increased with increasing distance from the continental shelf multidimensional scaling mds results from terminal restriction fragment length polymorphism t rflp analysis indicated a spatial coherence between the benthic bacterial community structure prokaryotic incorporation rates water content protein concentration and the total organic matter in the sediments the community complexity in sediments at 4 5 cm depth was lower in the central parts of the channel compared with the northern and the southern levees while richness in surface sediments of all stations was similar lacking any clear indications for a recent mass sediment transport or funneled shelf drainage flows high similarities between bacterial assemblages in sediments along the canyon course may thus be governed by a combination of an ice edge induced particle flux episodic down slope and canyon guided transport mechanisms

composition export and faunal utilization of drift vegetation in the salt river submarine canyon abstract submarine canyons may be particularly important in the transport process of drift seagrasses and seaweeds from highly productive shallow lagoon areas to deeper water we studied the composition export and faunal utilization of shallow nearshore benthic vegetation as it was transported to offshore areas via the salt river submarine canyon on the island of st croix u s virgin islands the study was conducted using a saturation diving system nuls 1 hydrolab during two missions in april and august 1980 using bottom drifters deployed in salt river bay and the submarine canyon we recorded net benthic current flow up to 2 cm s 1 moving out of the lagoon and down the canyon to deeper water using bottom nets set up at the canyon head and at the 29 m isobar and from transect surveys and drift clump samples we determined drift plant export rates and drift clump biomass and species composition the dominant drift plants were thalassia testudinum and syringodium filiforme and algae in the genera dictyota dictyopterus and diloplus during the second mission the seagrass halophila decipiens became more abundant both in the drift and in large patches along the canyon floor in both missions more drift was collected in the nets during high wind conditions than during calmer days calculated turnover times ranged from 0 01 to 4 4 days for algae in the order dictyotales and 4 4 to 18 days for thalassia blades total exported biomass of drift vegetation varied between 1 4 to 65 1 kg wet wt day 1 samples of drift vegetation contained mostly juvenile forms of both invertebrates and fishes but in relatively low numbers faunal numbers were most strongly related to rate of drift movement

megafauna distribution along active submarine canyons of the central mediterranean relationships with environmental variables abstract the tectonically controlled margins off southern italy are carved by several shelf indenting submarine canyons that are periodically flushed by sedimentary gravity flows in this study the distribution of benthic and demersal megafauna within the thalweg of some of these canyons i e the gioia petrace and caulonia marina canyons in the tyrrhenian and the ionian calabrian margins respectively and the sant agata san gregorio tremestieri and messina canyons in the messina strait was studied using remotely operated vehicle video transects the relationships between fauna distribution and environmental conditions i e seafloor type depth slope aspect and canyon system extracted from video footage and bathymetric data were assessed to identify the main physical drivers influencing the megafaunal assemblages within active submarine canyons these latter have their heads in shallow water so representing highly dynamic environments affected by present day sediment transport hierarchical cluster analysis allowed to distinguish seven different assemblages occurring in the study areas permanova analysis showed significant differences among species groups associated to different seafloor types depth ranges and canyon systems distance based linear modeling distlm identified the canyon system as the main factor explaining the variability of the megafaunal assemblages across the study areas in the gioia and petrace canyons both characterized by homogenous fine grained sediment the assemblages were mainly dominated by polychaeta sabellidae and ceriantharia the almost total absence of sessile fauna at the canyons head was interpreted as an effect of a strong physical disturbance due to the impact of sedimentary flows in the canyons of the messina strait the presence of more varied seafloor encompassing fine and coarse sediment along with an higher spatial heterogeneity of physical disturbance determined more diversified faunal assemblages featuring species associated with hard and soft substrates more in detail in the sant agata san gregorio and messina canyons the colonization of cobbles and boulders by slow growing species vulnerable to physical disturbance such as the gorgonians acanthogorgia hirsuta and swiftia dubia was recorded for the tremestieri canyons a stronger impact by sedimentary flows was reflected both by a very high abundance of land based litter and the lowest values of species richness interactions between megafauna and marine litter whose widespread occurrence was recorded on the floor of all these canyons have been also presented and discussed although in several cases litter caused entanglement of benthic species the anthropogenic debris was also used as growing substrate or shelter by some invertebrates and fishes suggesting complex fauna litter interactions that should be better explored overall the large variability in morphology and seafloor characteristics across the studied canyons is reflected on the variability of megafauna assemblages suggesting a strong influence of the physical conditions specific of each canyon in controlling fauna distribution

a 250 ka leaf wax δd record from a loess section in darai kalon southern tajikistan abstract the climate of sw central asia is influenced by strong precipitation seasonality with dry summers and winter spring precipitation delivered by mid latitude westerlies due to its geographic position sw central asia is a key locality for identifying fluctuations of westerlies siberian high and sw monsoon yet there is only limited information on the pleistocene climate history in sw central asia here we use plant wax biomarkers and their hydrogen isotope d composition from a loess section in darai kalon southern tajikistan to reconstruct environmental conditions of the past 250 thousand years ka we focus on the hydrogen isotope composition of long chain n alkanes dalk and long chain n carboxylic acids dcarb to reconstruct changes in the hydrological system moreover we infer information about past vegetation changes from proxies based on the relative abundance of these compounds results show that during glacials grasses dominated whereas during interglacials arboreal species prevailed these changes in vegetation follow the dominant glacial interglacial variability visible in the loess stratigraphy our results are in line with decreased precipitation during glacials as a result of a more extensive siberian high isotope measurements reveal a close relation of dalk and dcarb with insolation controlled by 20 ka cycles of orbital precession that is distinct from the glacial interglacial variability of the loess stratigraphy depleted enriched dalk and dcarb values coincide with low high winter spring insolation the precessional mode of our isotope records is likely influenced by variations in the precipitation seasonality between winter and spring precipitation caused by insolation induced temperature changes in comparison with speleothem records along the westerly path our results further indicate that the winter westerly storm tracks did not extend to the east of the tian shan during the last two glacial cycles

defining biological assemblages biotopes of conservation interest in the submarine canyons of the south west approaches offshore united kingdom for use in marine habitat mapping in 2007 the upper part of a submarine canyon system located in water depths between 138 and 1165 m in the south west sw approaches north east atlantic ocean was surveyed over a 2 week period high resolution multibeam echosounder data covering 1106 km2 and 44 ground truthing video and image transects were acquired to characterise the biological assemblages of the canyons the sw approaches is an area of complex terrain and intensive ground truthing revealed the canyons to be dominated by soft sediment assemblages a combination of multivariate analysis of seabed photographs 184 1059 m and visual assessment of video ground truthing identified 12 megabenthic assemblages biotopes at an appropriate scale to act as mapping units of these biotopes 5 adhered to current definitions of habitats of conservation concern 4 of which were classed as vulnerable marine ecosystems some of the biotopes correspond to descriptions of communities from other megahabitat features for example the continental shelf and seamounts although it appears that the canyons host modified versions possibly due to the inferred high rates of sedimentation in the canyons other biotopes described appear to be unique to canyon features particularly the sea pen biotope consisting of kophobelemnon stelliferum and cerianthids

cold seep like macrofaunal communities in organic and sulfide rich sediments of the congo deep sea fan methane rich fluids arising from organic matter diagenesis in deep sediment layers sustain chemosynthesis based ecosystems along continental margins this type of cold seep develops on pockmarks along the congo margin where fluids migrate from deep buried paleo channels of the congo river acting as reservoirs similar ecosystems based on shallow methane production occur in the terminal lobes of the present day congo deep sea fan which is supplied by huge quantities of primarily terrestrial material carried by turbiditic currents along the 800 km channel and deposited at depths of up to nearly 5000 m in this paper we explore the effect of this carbon enrichment of deep sea sediments on benthic macrofauna along the prograding lobes fed by the current active channel and on older lobes receiving less turbiditic inputs macrofaunal communities were sampled using either usnel cores on the channel levees or rov blade cores in the chemosynthesis based habitats patchily distributed in the active lobe complex the exceptionally high organic content of the surface sediment in the active lobe complex was correlated with unusual densitiesof macrofauna for this depth enhanced by a factor 7 to 8 compared with those of the older abandoned lobe whose sediment carbon content is still higher than in angola basin at same depth macrofaunal communities dominated by cossurid polychaetes and tanaids were also more closely related to those colonizing low flow cold seeps than those of typical deep sea sediment in reduced sediments microbial mats and vesicomyid bivalve beds displayed macrofaunal community patterns that were similar to their cold seep counterparts with high densities low diversity and dominance of sulfide tolerant polychaetes and gastropods in the most sulfidic habitats in addition diversity was higher in vesicomyid bivalve beds which appeared to bio irrigate the upper sediment layers high beta diversity is underscored by the variability of geochemical gradients in vesicomyid assemblages and by the vesicomyid population characteristics that vary in density size and composition by modifying the sediment geochemistry differently according to their morphology and physiology the different vesicomyid species play an important role structuring macrofauna composition and vertical distribution dynamics of turbiditic deposits at a longer temporal scale thousands of years and their spatial distribution in the lobe area also resulted in high heterogeneity of the cold seep like communities dynamics of chemosynthetic habitats and associated macrofauna in the active lobe area 2 please note that this is an author produced pdf of an article accepted for publication following peer review the definitive publisher authenticated version is available on the publisher web site resembled those previously observed at the regab pockmark along the congo margin and rapid succession is expected to cope with high physical disturbance by frequent turbiditic events and huge sedimentation rates finally we propose a model of the temporal evolution of these peculiar habitats and communities on longer timescales in response to changes in distributary channels within the lobe complex

habitat heterogeneity of hadal trenches considerations and implications for future studies abstract the hadal zone largely comprises a series of subduction trenches that do not form part of the continental shelf slope rise to abyssal plain continuum instead they form geographically isolated clusters of deep sea 6000 11 000 m water depth environments there is a growing realization in hadal science that ecological patterns and processes are not driven solely by responses to hydrostatic pressure with comparable levels of habitat heterogeneity as observed in other marine biozones furthermore this heterogeneity can be expressed at multiple scales from inter trench levels degrees of geographical isolation and biochemical province to intra trench levels variation between trench flanks and axis topographical features within the trench interior sedimentary basins ridges escarpments deeps seamounts to the substrate of the trench floor seabed sediment composition mass movement deposits bedrock outcrop using best available bathymetry data combined with the largest lander derived imaging dataset that spans the full depth range of three hadal trenches including adjacent slopes the mariana kermadec and new hebrides trenches the topographic variability fine scale habitat heterogeneity and distribution of seabed sediments of these three trenches have been assessed for the first time as well as serving as the first descriptive study of habitat heterogeneity at hadal depths this study also provides guidance for future hadal sampling campaigns taking into account geographic isolation total trench particulate organic matter flux maximum water depth and area

submarine canyon head morphologies and inferred sediment transport processes in the alias almanzora canyon system sw mediterranean on the role of the sediment supply abstract canyon head regions are key areas for understanding the shelf to canyon sedimentary dynamics and assessing the predominant hydrodynamic and sedimentary processes shaping their morphology high resolution multibeam bathymetry surveys conducted on the shelf upper slope and along the main thalwegs of the alias almanzora submarine canyon system were used to recognize the specific morphological features of the various canyon heads and infer the main sediment transport mechanism operating through them off the almanzora river different canyon head morphologies were observed at 65 90 m water depth incising the outer prodeltaic deposits a direct connection from the river supply is evidenced by the presence of a large radial field of sediment waves on the prodelta presumably related to hyperpycnal flows during flash flood events and their continuation towards trains of cyclic steps that merge into the almanzora canyon head processes linked to seepage and groundwater sapping also seems apparent in the prodeltaic deposits which results in pockmark alignments and formation of elongated narrow canyon heads at the southern limit of the almanzora prodelta another type of canyon head results from the formation and merging of linear gullies these have been interpreted as the morphological expression of the distal off shelf transport of flood related hyperycnal flows however most of the canyon heads of the main tributaries of this canyon system i e garrucha cabrera and alias are found at much shallower water depths 7 20 m they generally show a continuation in land with rivers or intermittent creeks known as ramblas that also experience flash flood events but some of them are disconnected from any river source these canyon heads cut into the infralittoral prograding wedge displaying feeder channels that tend to oriented against the direction of the prevalent long shore current some canyon head tributaries show sediment waves along their axis interpreted as the result of hyperpycnal flood events or storm induced turbidity flows this study focusses on the diversity of sediment transport processes that can co exist in the various canyon tributaries of a given submarine canyon system stressing on the importance of the canyon heads location with respect to the principal sedimentary source which ultimately determines their main geomorphological traits

spatial and temporal variability of meiobenthic density in the blanes submarine canyon nw mediterranean abstract meiofaunal density distribution was studied from 400 m to 1500 m depth inside blanes submarine canyon nw mediterranean and on the eastern open slope in autumn 2003 and spring 2004 our multidisciplinary approach allowed to study the hydrodynamics and sedimentary processes in the blanes canyon that characterize it as highly heterogeneous environment inside the canyon area particle fluxes were higher than on the slope area increased from autumn to spring and mostly consisted of lithogenic material moreover the canyon s locations experienced more intense bottoms currents and sediment disturbance being reflected in a greater variability of meiobenthic densities both between stations and sampling times than on the open slope no clear trends e g declining densities associated with increasing depths were observed contrary in the open slope current velocities were relatively lower compared with the canyon area and showed lower temporal variability at the same time the nutritional quality of the particle fluxes at deeper grounds were higher probably allowing the meiofaunal densities not to change over time in conclusion the meiobenthos in our system apparently showed a higher temporal variability inside the canyon area strongly affected by particle fluxes or erosive and sediment mixing processes linked to current modifications induced by the canyon topography

secondary production of ampelisca mississippiana soliman and wicksten 2007 amphipoda crustacea in the head of the mississippi canyon northern gulf of mexico abstract annual production was calculated for the dominant ampeliscid amphipod ampelisca mississippiana soliman y wicksten m 2007 ampelisca mississippiana a new species amphipoda gammaredea dominated the head of the mississippi canyon northern gulf of mexico zootaxa submitted at the head of the mississippi canyon in the northern gulf of mexico average densities were 12 094 2499 ind m 2 with secondary production of 6 93 g dry wt m 2 yr 1 based on the size frequency method hynes hamilton h b n coleman m 1968 a simple method for assessing the annual production of stream benthos limnology and oceanography 13 569 573 menzies c a 1980 a note on the hynes hamilton method of estimating secondary production limnology and oceanography 25 4 770 773 with a production biomass p b ratio of 3 11 growth rates of this magnitude are comparable to available data for freshwater and shallow marine ampeliscids but are unexpectedly high for deep ocean habitats growth efficiency appeared to be approximately 35 growth assimilation 100

understanding sediment dynamics of two large submarine valleys from seafloor data blanes and la fonera canyons northwestern mediterranean sea abstract the studied area appears as a major place for dense shelf water dsw formation and export towards the deep basin with blanes and la fonera canyons as most efficient pathways these two canyons are so deeply indented on the continental shelf and slope of the northern catalan margin western mediterranean sea that their heads significantly reduce the width of the shelf and interfere with coast and contour parallel sediment transport patterns this study presents the results of the analysis of swath bathymetry data and parametric seismic reflection profiles showing the detailed morphology and uppermost sedimentary structure of blanes and la fonera canyons with the focus on their heads and adjacent upper courses and shelf the main aim is to understand their functioning and assess how they influence and respond to the hydrosedimentary processes active in the study area the n s oriented blanes canyon head whose shortest distance to shore is only 4 km extends along 21 7 km from 70 to 1300 m water depth with an average rim to rim width of 8 km and a canyon floor width up to 750 m la fonera canyon head extends along 28 km from 60 to 1700 m water depth rim to rim and canyon floor widths are up to 7 km and up to 700 m respectively the canyon head follows a general wnw ese trending course in its deeper part but trends n s in its shallower course formed by cap begur branch south of it the illa negra branch trends nw se and its tip located at 60 m water depth and 800 m from the coastline intersects the littoral sedimentary prism backscatter data show high reflectivity into both blanes and la fonera canyon floors as well as on tributary gullies which at these locations is indicative of coarse sediment the seafloor and subseafloor observations here presented are explained and best understood from the sedimentological viewpoint by the interplay of event driven dsw flows permanent mesoscale circulation and storm action while dsw flows from the gulf of lion and the shelf area around the studied canyons are the most dynamic agent in terms of sediment transport and seafloor shaping the northern current ensures background sedimentation of fines and coastal storms promote episodic entries through canyon heads and upper course rims canyon wall morphology and sediment draping respond to the currentward or leeward position of each wall with respect to the main southward moving water flows in the area either episodic or permanent that are dsw and the northern current other relevant morphosedimentary features such as a 40 km long southbound subdued channel on the roses outer shelf that originates off cap de creus promontory to finally feed cap begur branch of la fonera canyon and a contouritic ridge and moat attached to the northern wall of the canyon are interpreted in terms of dsw flows a comprehensive model of the sedimentary functioning of the canyoned north catalan margin that integrates seafloor information and background data on dynamic processes is presented which could be of application to other continental margins worldwide such an integrative view is eased by the enormous unprecedented multidisciplinary research effort carried out in the study area over the last three decades

biodiversity and distribution of meiofauna in the gioia petrace and dohrn canyons tyrrhenian sea abstract habitat heterogeneity is a major structuring agent of benthic assemblages promoting high turnover in species composition and ultimately contributing to overall higher diversity submarine canyons a pervasive feature of the continental margins worldwide increase habitat heterogeneity at multiple spatial scales in the present study we test the hypothesis that different topographic structures or and food sources controlling the abundance biomass and biodiversity using meiofauna and nematodes as a model study in canyon systems to do so we compared different topographic structures canyon edge thalweg and axis and the upper shelf and open slope in the gulf of gioia gioia and petrace canyons and in the gulf of naples dohrn canyon tyrrhenian sea at different depths our results suggest that meiofaunal abundance and biomass are generally higher in the canyon thalwegs than in the canyon edge or adjacent open slopes at regional scale this pattern is not always confirmed for biodiversity and when thalwegs are compared to different topographic structures within the gioia canyon system in our study the role of food quantity and quality is preeminent to explain the spatial distribution of meiofaunal variables among different topographic structures at 200 m while habitat heterogeneity become relevant at 500 m and within the dohrn canyon in gioia and petrace canyons we observed a high food availability is associated to specific topographic structures thalwegs that influenced the meiofaunal abundance and diversity distribution and nematode diversity and species composition each topographic structure shows a high number of exclusive species that contributes to a high species turnover and high overall biodiversity in all canyon systems changes in nematode composition determine also differences in the functional diversity trophic guilds composition and life strategy of the nematode assemblages our findings reveal that the presence of different topographic structures influences the spatial distribution of food quality and quantity that determine the presence of exclusive taxa and species enhancing both local and regional diversity

late quaternary fluctuations of palaeoproductivity in the murray canyons area south australian continental margin abstract two sediment cores from the murray canyons area south of kangaroo island south australia were investigated for proxy records to reconstruct past productivity of the surface waters in the area over the last 175 ka the proxies used included concentrations of aragonite low and high mg calcite total carbonate total organic carbon sulfur and 13c of globigerina bulloides cyclic increases in palaeoproductivity were observed to be in tune with insolation minima at 30 s the atmospheric conditions during insolation minima were comparable to present winter patterns when strong westerly winds dominate over the area and bring dust from the central desert areas during the last insolation minimum last glacial maximum lgm the murray canyons laid directly under the eastern australian dust plume dust could have fertilized surface waters and initiated the observed productivity increases on a precessional time scale the core from the more westerly canyons is richer in organic matter this could be attributed to the influx of organic matter from shallower water which is carried by an overflow of hypersaline water from the spencer gulf to the deep ocean using the western canyons as conduits there is no evidence that the palaeo murray river which debouches close to the core sites during sealevel lowstands was a major source of nutrients for surface waters although total carbonate concentrations remained high planktonic foraminifers were fewer in numbers during these periods possibly due to reduced light penetration caused by suspended river material a deglacial minimum in 13c of globigerina bulloides observed in other cores from the southern hemisphere and attributed to a major hydrographic change south of the polar front is also visible in our two cores thus attesting to the global significance of the event

megabenthic assemblages at the hudson canyon head nw atlantic margin habitat faunal relationships abstract the distribution of megabenthic communities at the head of hudson canyon and adjacent continental shelf was studied by means of underwater video transects and still photo imagery collected using a towed camera system the goal was to explore the relationships between faunal distribution and physical seafloor conditions and to test the hypothesis that increased seafloor heterogeneity in the hudson canyon supports a larger diversity of benthic communities compared with the adjacent continental shelf hierarchical cluster analysis was performed to identify benthic assemblages as defined in imagery the bio env procedure and the canonical correspondence analysis were carried out to elucidate species groupings in relation to terrain variables extracted from bathymetric data species accumulation curves were generated to evaluate species turn over in and out of hudson canyon the results indicate that seafloor morphology is the main physical factor related to benthic community composition and distribution assemblages dominated by sponges zoanthids and cup corals colonized the canyon margins and flanks and were associated with coarse grained sediments while sea pen assemblages were observed along muddy seafloor within the thalweg an assemblage dominated by sea stars occurred on the shelf associated with a sandy seafloor some assemblages were exclusively observed in the canyon area suggesting that the increased variability of seafloor composition together with the oceanographic processes specific to the canyon area enhance beta diversity the colonization by benthic suspension feeders within the canyon in contrast to shelf assemblages mainly composed of carnivores and detritus feeders could be favored the intense hydrodynamics at the canyon head that increase the availability of suspended organic matter from the perspective of management and conservation of marine resources the results obtained support the relevance of hudson canyon as a biodiversity hotspot such results are of particular significance in light of the recent action promoted by the mid atlantic fisheries management council that restricts bottom trawling in most of the submarine canyons of the us atlantic margin including the hudson canyon to protect cold water corals from damage by fishing gear

organic enrichment of submarine canyon and continental shelf benthic communities by macroalgal drift imported from nearshore kelp forests remotely operated vehicle rov surveys were conducted over a 3 year period to evaluate the importance of macroalgal drift exported from nearshore forests of giant kelp macrocystis pyrifera to adjacent submarine canyon and continental shelf benthic habitats abundant macroalgal drift was found in the carmel submarine canyon 153454 m depth but was rare at pt joe a continental shelf habitat 9 km away 87 357 m depth most of the drift parcels consisted of brown algae but 10 other categories were found including green and red algae and the surfgrass phyllospadix spp m pyrifera drift accounted for as much as 20 of the density of drift parcels in the carmel submarine canyon and up to 50 of the drift parcels at pt joe from previously determined turnover rates of drift m pyrifera and the standing stock estimates from the present study we estimated that the rate of carbon flux associated with drift m pyrifera to the benthos of the cannel submarine canyon was 45 2 mg c m z d i based on published estimates of carbon flux from vertically sinking particulate organic carbon at 400 m depth in the nearby monterey submarine canyon and our estimates of kelp derived carbon flux drift m pyrifera can account for 20 83 of the total particulate organic carbon reaching the sea floor in the carmel submarine canyon we conclude that drift macrophytes provide significant enrichment of organic carbon to the benthos above that provided by vertically sinking particulate organic material the extent to which this alters the structure of benthic communities compared to areas without organic enrichment by drift macrophytes remains unknown and awaits further study deep sea benthic communities are entirely dependent on imported primary production for metabolic energy except hydrothermal vent and cold seep communities whose energy is provided by chemolithoautotrophy organic carbon arrives at the sea floor as small detrital particles episodic deliveries of large organic parcels such as large animal carcasses actively swimming zooplankton turbidity currents and macrophyte detritus rowe 1981 the relative importance of these organic carbon pathways no doubt varies with habitat and distance from shore although quantification of these pathways is still in its infancy gage and tyler 1991 pilskaln et al 1996 rowe 1981 the macrophyte detritus pathway may be particularly important in deep sea environments adjacent to productive neat shore habitats such as seagrass meadows or kelp forests where macrophyte detritus removed from these habitats may be transported offshore to deep sea benthic communities via bottom currents josselyn et al 1983 menzies et al 1967 suchanek et al 1985 vetter and dayton in press forests of giant kelp

benthic foraminifera from capbreton canyon revisited faunal evolution after repetitive sediment disturbance abstract at a 650 m deep site in the axis of capbreton canyon an 18 cm thick turbidite was deposited in december 1999 during subsequent campaigns an almost monospecific fauna of the benthic foraminifer technitella melo considered as a pioneer species was found in may 2000 in 2001 this fauna had disappeared and was replaced by an exceptionally rich fauna strongly dominated by the opportunistic species bolivina subaenariensis we present sedimentological radionuclide and foraminiferal data of new cores sampled in 2005 and 2011 taken with the aim to study the further evolution of the benthic ecosystem cores sampled in 2005 show that in the canyon axis a new ca 5 cm thick turbidite has been deposited the live benthic foraminiferal faunas were much poorer than in 2001 but still had a high dominance and low diversity although less extreme than in 2001 we conclude that in the canyon axis benthic foraminiferal faunas remain in an early stage of ecosystem colonization it appears that the very thick 1999 turbidite marks an exceptional event the uncommonly rich faunas observed in 2001 could be a response to the concentration of organic rich material in the fine grained top of this deposit in 2011 cores were sampled at a slightly different site on the lower canyon flank the sedimentary sequence here is marked by the absence of coarse turbidite layers although some levels show slightly increased grain size and lower 210 pb xs activities indicative of an admixture with advected older sediments live foraminiferal faunas are much more equilibrated as shown by their higher diversity lower dominance and deeper penetration into the sediment all these characteristics are indicative of a much more stable ecosystem dead faunas are present throughout the core indicating that the levels with slightly elevated grain size are not typical turbidites resulting from hyperpycnal currents which are characterized by levels barren of foraminifera but denote other more long term sedimentary processes leading to the advection of older material such as bottom nepheloid layers or repetitive fine grained turbidite deposits due to small scale slumping the comparison of live and dead fauna shows that at both sites the foraminiferal turnover rates are fairly low at the lower canyon flank site sampled in 2011 the foraminiferal faunas are renewed every 1 5 2 years such a fairly long foraminiferal lifespan corresponds to earlier estimates but is surprisingly high for the opportunistic taxa that dominate the faunal assemblages in these unstable and food enriched submarine canyon settings

habitat compression and expansion of sea urchins in response to changing climate conditions on the california continental shelf and slope 1994 2013 abstract echinoid sea urchins with distributions along the continental shelf and slope of the eastern pacific often dominate the megafauna community this occurs despite their exposure to naturally low dissolved oxygen do waters

excepftonally strong near bottom flows on the continental rise of nova scotia recent current velocity measurements across the lower continental rise of nova scotia show a deep equatorwardflow with speeds maximum 73 centimeters per second among the highest recorded for the deep sea silicate measurements indicate that this flow usually consists of southern source antarctic bottom water these measurements confirm the existence of a second and deeper western boundary flow that was earlier inferredfrom geological observations

general patterns of circulation sediment fluxes and ecology of the palamos la fonera submarine canyon northwestern mediterranean abstract currents particle fluxes and ecology were studied in the palamos submarine canyon also known as the fonera canyon located in the northwestern mediterranean seven mooring arrays equipped with current meters and sediment traps were deployed along the main canyon axis on the canyon walls and on the adjacent slope additionally local and regional hydrographic cruises were carried out current data showed that mean near surface and mid depth currents were oriented along the mean flow direction ne sw although at 400 and 1200 m depth within the canyon current reversals were significant indicating a more closed circulation inside the canyon mean near bottom currents were constrained by the local bathymetry especially at the canyon head the most significant frequency at all levels was the inertial frequency a second frequency of about three days attributed to a topographic wave was observed at all depths suggesting that this wave was probably not trapped near the bottom the current field observed during the most complete survey revealed a meandering pattern with cyclonic vorticity just upstream from and within the canyon the associated vertical velocity ranged between 10 and 20 m day and was constrained to the upper 300 m this latter feature together with other computations suggests that during this survey the meander was not induced by the canyon but by some kind of instability of the mean flow in the canyon suspended sediment concentration downward particle fluxes chlorophyll and particulate c and n were significantly higher up canyon from about 1200 m depth than offshore defining along with the different hydrodynamics two canyon domains one from the canyon head to about 1200 m depth more affected by the canyon confinement and the other deeper than 1200 m depth more controlled by the mean flow and the shelf slope front the higher near bottom downward total mass fluxes were recorded in the canyon axis at 1200 m depth along with sharp turbidity increases and are related to sediment gravity flows during the deployment period the increase in downward particle fluxes occurred by mid november when a severe storm took place on the canyon walls at 1200 m depth suspended sediment concentrations downward particle fluxes chlorophyll and particulate c and n were higher on the southern wall than on the northern wall inversely to the current s energy this could be caused by an upward water supply on the southern canyon wall and or the mean flow interacting with the canyon bathymetry in the swimmers collected by the sediment traps the dominant species was an elasipod holothurian which has not been recorded in other canyons or elsewhere in the mediterranean indicating particular speciation

macrofaunal communities within and adjacent to a detritus rich submarine canyon system abstract macrofaunal abundance biomass diversity and species assemblages within scripps and la jolla submarine canyons are compared with those on the nearby continental shelf and slope our primary objective was to examine the effect of detrital aggregates on infaunal communities within canyons two submarines a remotely operated vehicle rov and a soutar box corer were used to collect samples within the canyons organic enrichment by macrophyte detritus was evident from canyon heads down to 550 m and evidence of strong currents coarse sediment was found down to 700 m infaunal density and biomass were higher in the canyons than outside at all depths where comparative data were available 100 500 m infaunal assemblages in canyons were distinct from those at reference stations both the canyon and non canyons samples showed community differentiation with depth species diversity was generally high but decreased with depth outside of canyons and increased with depth within the canyons low diversity at shallow depths within the canyon is attributed to a combination of organic enrichment and physical disturbance submarine canyons are commonly found to contain distinct species assemblages or higher faunal densities and or biomass than nearby non canyon regions at similar depths canyons are regular features along most ocean margins and appear to be important as sites of enhanced secondary production provide diverse habitats and act as conduits of coastal detritus to the deep sea

possible tectonomagnetic effect observed from mid 1989 to mid 1990 in long valley caldera california precise measurements of local magnetic fields have been obtained with a differentially connected array of three proton magnetometers in the long valley caldera region since 1984 two magnetometers are located inside the caldera with a third reference magnetometer located 26km southeast of the caldera after correction for secular variation it is apparent that an anomalous 2 nt decrease in the magnetic field occurred from mid 1989 to mid 1990 at the magnetometer located closest to the center of the resurgent dome inside the caldera during this period a significant increase in geodetic strain rate of 8 5 ppm a was observed on the two color geodimeter network within the caldera from october 1989 to mid 1990 and a dramatic increase in seismic activity occurred from december 1989 to july 1990 a simple dilatational point source model with pressure increasing by 52 mpa from october 1989 to august 1990 at a depth of about 7km beneath the center of the resurgent dome can be fit to the strain data if this same model is used to calculate piezomagnetic fields in the caldera the results obtained agree with the observed local magnetic field data provided the curie point isotherm is at a depth of 5km taken together these magnetic seismic and geodetic data suggest that an episode of active magmatic intrusion occurred from late 1989 to mid 1990 at a depth of about 7 8km beneath the resurgent dome within the long valley caldera other indications of this intrusion should be evident in measurements of leveling local gravity and seismic imaging data

objective automated classification technique for marine landscape mapping in submarine canyons abstract this study proposes a fully automated and objective technique to map marine landscapes in submarine canyons the method is suitable for broad and regional scale mapping derived from sonar data using multivariate statistical analysis the method is divided into two main parts the terrain analysis and the multivariate statistical analysis the first part aims to optimise the sonar data and comprises three steps 1 data resampling 2 determination of length scale and 3 multiple scale analysis the second part covers the actual marine landscape classification and consists of 1 principal component analysis pca 2 k means clustering and 3 cluster determination in addition a confidence map is presented based on cluster membership derived from cluster distance in attribute space the technique was applied in the lisbon setubal and cascais canyons offshore portugal the area was classified into 6 marine landscapes that represent the geomorphological features present in submarine canyons the main findings from the study are 1 the transferability of a tool from geomorphometric analysis estimation of scale parameter esp to detect the length scale of potential patterns in bathymetric grids 2 multiple scale terrain analysis allows an appropriate discrimination of local and broad scale geomorphic features in marine landscape mapping 3 the method not only delineates geomorphic seafloor features but also points out properties that might influence biodiversity in a complex terrain

deep sea habitat heterogeneity influence on meiofaunal communities in the gulf of guinea to estimate the degree of spatial heterogeneity of benthic deep sea communities we carried out a multiple scale from m s to 200 km investigation in the congo angola margins equatorial west african margin 3150 4800 m in which we examined the metazoan meiofauna at a variety of habitats along the congo channel system and in the associated cold seep we investigate the structure density vertical distribution patterns in the sediment and biomass of meiofaunal communities in the gulf of guinea and how they are controlled by hydrologic and biogeochemical processes the meiofaunal communities in the gulf of guinea were shaped by heterogeneous conditions on the margin and reflect the multiple scale spatial variability that corresponds with the different identified habitats the two control sites located at 100 km away from the canyon were inhabited by very dense and the most diverse meiobenthic communities similar meiobenthic communities inhabited the transition zone between the canyon and the cold seep sites located along the congo channel were obviously affected by the local high velocity bottom currents and unstable sedimentary conditions in this active submarine system extremely low meiobenthic densities and very low proportions in the most surficial sediment layers provided evidence for recently highly disturbed sediments at these sites the remote operated vehicle rov victor 6000 provided images of the cold seep showing a patchy distribution of several types of patchy distributed megafaunal communities dominated by three key symbiotic taxa mytilidae vesicomyidae and siboglinidae these cold seep sediments were colonised by a unique meiobenthic community characterised by a high small scale m s patchiness low species richness and the prominent dominance of two large sized nematode species sabatieria mortenseni which is a cosmopolitan nematode known from littoral habitats and an undescribed desmodora species the high individual body weight of s mortenseni and its dominance at the cold seep site resulted in a significantly higher nematode biomass at the seep compared to the surrounding sites in addition the vertical nematode profiles with maximum proportions in subsurficial layers points to a chemosynthesis based meiobenthic community in this cold seep in contrast to the phytodetritus based communities at the control sites and at the transition zone

deep sea mobile megafauna of mediterranean submarine canyons and open slopes analysis of spatial and bathymetric gradients abstract mediterranean canyons are generally characterized by complex topography and hydrographic conditions and can act as conduits for organic matter and sediments from the shelf to the deep sea which result in enhanced macro and megafaunal abundance and biodiversity here we reviewed the literature of the last 20 years and combined available information with new data from our own datasets including unpublished data on megafaunal species inhabiting submarine canyons and the adjacent slopes we analysed the data acquired using different gears from baited cameras on aluminum frames and landers and baited traps to commercial trawl gears in order to combine and complement the results in megafaunal biodiversity and assemblage structure in mediterranean canyons overall the results of our analysis on megafaunal assemblages allowed identifying 400 species including 28 species of cephalopods 64 of decapod crustaceans 25 of echinoderms 27 of elasmobranches and 127 of actinopterygii we observed significant longitudinal differences in assemblage composition with high species turnover across mediterranean sub basins our analysis also confirmed the importance of depth axis as the main factor influencing the structure of the deep sea demersal assemblages with greater diversity in the upper part of the slopes the multivariate multiple regression analysis showed that geomorphological features of the canyons i e slope dendricity sinuosity and distance from adjacent canyons contribute significantly to explain the observed variability in the taxonomic composition of megafaunal assemblages at sub basin scale the results presented here are important in global biodiversity management perspectives and confirm that canyons represent a seascape unit deserving protection at different levels modulated according to biogeographic and geomorphological features

distributions and habitat associations of deep water corals in norfolk and baltimore canyons mid atlantic bight usa a multi disciplinary study of two major submarine canyons baltimore canyon and norfolk canyon off the us mid atlantic coast focused on the ecology and biology of canyon habitats particularly those supporting deep sea corals historical data on deep sea corals from these canyons were sparse with less than 750 records for the mid atlantic region with most being soft sediment species this study substantially increased the number of deep sea coral records for the target canyons and the region large gorgonians were the dominant structure forming coral taxa on exposed hard substrates but several species of scleractinians were also documented including first observations of lophelia pertusa in the mid atlantic bight region coral distribution varied within and between the two canyons with greater abundance of the octocoral paragorgia arborea in baltimore canyon and higher occurrence of stony corals in norfolk canyon these observations reflect the differences in environmental conditions particularly turbidity between the canyons some species have a wide distribution e g p arborea primnoa resedaeformis anthothela grandiflora while others are limited to certain habitat types and or depth zones e g paramuricea placomus l pertusa solenosmilia variabilis the distribution of a species is driven by a combination of factors which include availability of appropriate physical structure and environmental conditions although the diversity of the structure forming corals gorgonians branching scleractinians and large anemones was low many areas of both canyons supported high coral abundance and a diverse coral associated community the canyons provide suitable habitat for the development of deep sea coral communities that is not readily available elsewhere on the sedimented shelf and slope of the mid atlantic bight

macrofaunal assemblages in canyon and adjacent slope of the nw and central mediterranean systems abstract macrofaunal assemblages were studied along bathymetric transects in six canyons and four adjacent open slopes of the mediterranean sea the different areas investigated were located approximately along a longitudinal gradient at similar latitudes three regions were investigated the catalan from 334 to 1887 m depth the ligurian from 222 to 2005 m depth and the south adriatic margins from 196 to 908 m depth the analysis of the meso scale distribution of assemblage structure and biomass showed significant differences among regions which resulted in high values of diversity clear differences in trophic composition were also observed and a decreasing pattern in the individual body size of macrofaunal organisms moving eastward these patterns were apparently linked to changes in food supply whereas macrofaunal abundance and number of taxa showed a decrease pattern with increasing water depth when the assemblage structure was compared between canyons and adjacent open slope a very high diversity was observed indicating that the bottom topography exerted a strong effect on the assemblage characteristics

the connection between iron ore formations and mud shrimp colonizations around sunken wood debris and hydrothermal sediments in a lower cretaceous continental rift basin mecsek mts hungary in the early cretaceous the continental rift basin of the mecsek mts hungary was situated on the southern edge of the european plate the opening of the north atlantic ocean created a dilatational regime that expanded to the southern edge of the european plate where several extensional basins and submarine volcanoes were formed during the early cretaceous epoch permanent seaquake activity caused high swell events during which a large amount of terrestrial wood fragments entered into submarine canyons from rivers or suspended woods which had sunk into the deep seafloor these fragments created extended wood fall deposits which contributed large scale flourishing of numerous burrowing thalassinid crustaceans twelve different thalassinid coprolite ichnospecies can be found in the berriasian hauterivian volcano sedimentary formations

a conceptual surrogacy framework to evaluate the habitat potential of submarine canyons the seascape of the vast australian continental margin is characterised by numerous submarine canyons that represent an equally broad range of geomorphic and oceanographic heterogeneity theoretically this heterogeneity translates into habitats that may vary widely in their ecological characteristics here we describe the methodology to develop a framework to broadly derive estimates of habitat potential for pelagic and epibenthic species including demersal fishes and benthic infauna in all of australia s known submarine canyons our analysis shows that the high geomorphic and oceanographic diversity of australian submarine canyons creates a multitude of potential habitat types in general it appears that canyons may be particularly important habitats for benthic species canyons that incise the shelf tend to score higher in habitat potential than those confined to the slope canyons with particularly high habitat potential are located mainly offshore of the great barrier reef and the nsw coast on the eastern margin of tasmania and bass strait and on the southern australian margin many of these canyons have complex bottom topography are likely to have high primary and secondary production and have less intense disturbance to sediment the framework presented here can be applied once refined and comprehensively validated with ecological data to help managers make informed conservation decisions especially for high value canyons

limited depth zonation among bathyal epibenthic megafauna of the gully submarine canyon northwest atlantic abstract the gully is a large submarine canyon incised into the scotian shelf in the northwest atlantic a submersible mounted camera was used to collect 17 km of high resolution video imagery of the soft sediment flanks and floor of the canyon between 1000 and 2500 m depth a depth stratified random survey design with two transects per stratum was followed depth strata were drawn at 1000 1500 m 1500 2000 m and 2000 2500 m reflecting global and regional faunal boundaries the 47 614 individuals or colonies observed on the transects were identified into 49 unique taxa drawn from 7 phyla while 21 additional taxa were observed between the transect lines cnidaria was the most diverse phylum 22 taxa on the transects followed by the echinodermata 15 taxa most fauna were sessile or sedentary suspension feeders a species of xenophyophorida likely syringammina sp was the most abundant taxon cluster analysis of transects based on a bray curtis bc matrix of species abundance identified one cluster of five transects and one independent transect the deepest transect 2406 m average depth a similarity profile test indicated that this structure is not random there was a significant change in the megafaunal assemblage with depth over scales of 10s of kilometers accounting for 65 of the variation in the bc matrix both total organic carbon and labile carbon were higher in cores from the 1000 1500 m stratum than at greater depth consistent with transport of food and sediments into the canyon from shallower waters the first principal component calculated from species abundances separated the two transects from the 1000 1500 m depth stratum from the others indicating that sediment food supply influences community structure and composition over small spatial scales 10 m eight groups of species associations were identified however the associations between the species within each group were not strong with the highest correlation between the xenophyophorida and the pennatulacea 0 66 at this spatial scale substrate type was an important factor with hard and soft bottom species associations being identified

submarine canyons as important habitat for cetaceans with special reference to the gully a review there has been much research interest in the use of submarine canyons by cetaceans particularly beaked whales family ziphiidae which appear to be especially attracted to canyon habitats in some areas however not all submarine canyons are associated with large numbers of cetaceans and the mechanisms through which submarine canyons may attract cetaceans are not clearly understood this paper reviews some of the cetacean associations with submarine canyons that have been anecdotally described or presented in scientific literature and discusses the physical oceanographic and biological mechanisms that may lead to enhanced cetacean abundance around these canyons particular attention is paid to the gully a large submarine canyon and marine protected area off eastern canada for which there exists some of the strongest evidence available for submarine canyons as important cetacean habitat studies demonstrating increased cetacean abundance in the gully and the processes that are likely to attract cetaceans to this relatively well studied canyon are discussed this review provides some limited evidence that cetaceans are more likely to associate with larger canyons however further studies are needed to fully understand the relationship between the physical characteristics of canyons and enhanced cetacean abundance in general toothed whales especially beaked whales and sperm whales appear to exhibit the strongest associations with submarine canyons occurring in these features throughout the year and likely attracted by concentrating and aggregating processes by contrast baleen whales tend to occur in canyons seasonally and are most likely attracted to canyons by enrichment and concentrating processes existing evidence thus suggests that at least some submarine canyons are important foraging areas for cetaceans and should be given special consideration for cetacean conservation and protection

acoustical detection of high density krill demersal layers in the submarine canyons off georges bank high density demersal layers of krill have been detected in the submarine canyons off georges bank by means of a high frequency dual beam bioacoustical technique krill densities in these demersal layers were observed to be two to three orders of magnitude greater than the highest densities observed in water column scattering layers such abundances may help explain the unusually high squid and demersal fish production estimates attributed to the georges bank ecosystem

macrofaunal density and biomass in the campeche canyon southwestern gulf of mexico abstract the composition density and community structure of the benthic macrofauna were investigated in sediments of the campeche canyon in the sw gulf of mexico total macrofaunal density ranged from 9466 2736 ind m 2 at the continental shelf station to 1550 195 ind m 2 in the canyon density values significantly diminished with distance from the coast and depth only a few stations in the center of the canyon displayed larger density values e 37 with 4666 1530 ind m 2 e 36 with 5791 642 ind m 2 and e 26 with 6925 2258 ind m 2 densities were positively correlated to organic nitrogen in the sediment r 0 82 and coarse silt r 0 43 and negatively with depth r 0 74 and distance from the coast r 0 68 at all stations the polychaete worms contributed most to the multi species community structure the nematodes and foraminifera displayed their highest densities in the center of the canyon the biomass values declined significantly with depth we conclude that the macrofauna density and biomass changed in response to organic matter contents in the sediment both with distance from the coast and with depth

recent sediment transport and deposition in the lisbon setubal and cascais submarine canyons portuguese continental margin abstract recent sediment transport and deposition in the lisbon setubal and cascais submarine canyons portuguese continental margin were investigated on the basis of water column profiles of suspended particulate matter records of near bottom currents and settling fluxes of particulate matter obtained with benthic landers and analysis of surface sediments the results show that fine grained predominantly lithogenic sediment derived from adjacent shelf areas accumulates in the upper reaches of the canyons sediment deposited further down in the middle and lower reaches of the canyons is essentially similar to the hemipelagic sediment found on the adjacent continental slope indicating that down canyon transport of sediment from the upper to the lower canyon is limited tidal currents measured at various depths in the lisbon setubal canyon appear sufficiently strong to resuspend and transport sediment but net up canyon flow of the bottom water may retain shelf derived lithogenic sediment in the upper canyon sediment gravity flows which in the nearby nazare canyon are an effective mechanism for down canyon sediment transport appear rare in the lisbon setubal canyon and probably also in the cascais canyon turbidity current events recorded in the sedimentary record of the canyons may correspond to seismic events of 1969 and 1755 ad

in situ raman spectroscopy study of synthetic gas hydrate formed by cold seep flow in the south china sea abstract properties of gas hydrate are commonly investigated in laboratory by simulators or studied using the hydrate samples recovered from permafrost and marine sediments here synthetic gas hydrate sgh is quickly formed for the first time by fluids and bubbles erupted from the active cold seeps at the formosa ridge in the south china sea scs sgh samples are in situ detected by a raman insertion probe for gas hydrate rip gh which is deployed by the remotely operated vehicle rov faxian both spatial and temporal in situ raman spectra of the sgh samples are acquired in order to determine the structure and the evolution of the synthetic gas hydrate authigenic carbonate debris or other debris serving as nucleation particles which is found in the in situ raman spectra of sgh samples for the first time may be one factor that can promote the formation of synthetic gas hydrate the gas water interface demonstrated by the observation results also contributes to the quick formation of sgh samples which agrees well with the previous study in situ raman spectra of three sgh samples which have been placed on the seafloor for 0 h 4 h and 21 h respectively are acquired laboratory raman spectra of one sample which has been surprisingly found and recovered after 9840 h 410 days since formed on the seafloor are also acquired the raman spectra of the four sgh samples indicate that the methane large to small cage occupancy ratios of the hydrates vary from 1 01 to 1 39 and the ratios of methane large to gas of the hydrates increase from 0 53 to 1 55 overall our work suggests a new explanation for the quick formation of gas hydrate compared to that in laboratory simulation work and reveals the evolution of synthetic gas hydrate after quick formation which provides a new insight for the study of natural gas hydrate

classification of submarine canyons of the australian continental margin abstract submarine canyons influence oceanographic processes sediment transport productivity and benthic biodiversity from the continental shelf to the slope and beyond however not all canyons perform the same function the relative influence of an individual canyon on these processes will in part be determined by its form shape and position on the continental margin here we present an analysis of canyon geomorphic metrics using an updated national dataset of 713 submarine canyons surrounding mainland australia these metrics attributes for each canyon are used to classify them into canyon types across a hierarchy of physical characteristics separately for shelf incising n 95 and slope confined blind n 618 canyons we find that the canyon metrics describe a wide variety of canyon form and complexity that is consistent with a population of canyons that has evolved at different rates around the australian margin since the break up of gondwana the large number of slope confined canyons is interpreted to reflect dominance of slope mass wasting processes over erosive turbidity flows from fluvial and shelf sources on an arid continent the distribution of submarine canyons around the australian margin is not regular with clusters occurring in the east southeast west and southwest where the margin is steepest the classification result provides a quantitative framework for describing canyon heterogeneity for application in studies of geological controls on individual canyons canyon oceanography and canyon biodiversity