Remotely Operated Vehicle Dives Research Articles

Seafloor Investigations of the Kemp Caldera, the Southernmost Arc Caldera Volcano From the South Sandwich Island Arc

AbstractKemp Caldera, situated in the south of the intra‐oceanic South Sandwich arc, is one of the least explored submarine calderas that hosts hydrothermally active vent sites. The caldera was discovered in 2009. Since then, the focus has been primarily on biological studies. During the R/V Polarstern cruise PS119 in 2019, we gained new insights into the morphology, petrology and the formation of the Kemp Caldera. The ship's multibeam data provide an overview of the caldera bathymetry and backscatter characteristics. The new data revealed that the caldera is nested with two or possibly three concentric calderas. TV‐sled and remotely operated vehicle (ROV) observations provide detailed visual data for the hydrothermally active sites of the vent field at the central resurgent cone and flare site at the NNW caldera rim. The central vent field is dominated by white smokers, where clams, sponges and other fauna thrive, while at the flare site inactive as well as actively venting chimneys have been found. The latter are characterized by metal‐enriched fluids of temperatures ≥200°C. During ROV dives, rock samples were collected from the cone, providing the first information about the Kemp Caldera rock composition. The caldera rocks are dacitic, in contrast to the basalts and andesites of the neighboring Kemp Seamount. This suggests that the dacitic cone was formed by one or more later eruptions of differentiated magma, probably stored in shallow intrusions which are driving hydrothermal activity.

Enigmatic Deep-Water Mounds on the Orphan Knoll, Labrador Sea

Deep-sea mounds can have a variety of origins and may provide hard-substrate features in depths that are normally dominated by mud. Orphan Knoll, a 2 km high bedrock horst off northeast Newfoundland, hosts more than 250 mounds of unknown composition, 10-1000 m high and 1-3 km wide in water depths of 1600–3200 m. The study objective was to characterize the size, shape, orientation, and composition of the enigmatic Orphan Knoll mounds, in order to determine their age and origin. Archival ship-based side-scan sonar, multibeam sonar, airgun, high-resolution sparker and 3.5 kHz acoustic sub-bottom profiling, and newly acquired ship-based multibeam sonar, video transects by remotely operated vehicle (ROV), rock samples, and near-bottom multibeam sonar data were analyzed. Four mounds were studied during two ROV dives. Archival sidescan sonar data show >200 mounds. Sparker profiles show that the mound crests are covered by condensed stratified Quaternary sediment and airgun seismic data show faults reaching near the seafloor. New multibeam sonar data show mounds are dominantly conical to elliptical in shape, but without preferred orientation or alignment. ROV transects and near-bottom multibeam showed that three mounds were rounded and symmetrically arranged, while a fourth was more asymmetrical, with steep faces on the southwestern and southeastern flanks, where finely bedded to massive sedimentary bedrock outcropped dipping 15-45°SW. Rock samples from the mounds include Eocene calcareous ooze and mid-Miocene bedded pelagic limestone. Thick ferromanganese crusts were found on many surfaces, obscuring possible outcrops from physical sampling. Polymetallic nodules were found on the slope of one mound. Ice-rafted detritus, including igneous and metamorphic rocks and Paleozoic limestone and dolostone, was common in the sediments immediately surrounding the mounds. Quaternary sub-fossil solitary scleractinian corals accumulated over a span of at least 0.18 Ma at the base of one mound. The presence of uplifted condensed Eocene-Miocene rocks on the mounds and faulting in seismic profiles suggest uplift during reactivation of old rift-related faults during the Neogene, with seabed mass wasting creating residual mounds, which were then draped by Quaternary proglacial muds. Sculpting of hemipelagic Quaternary sediment by bottom currents probably contributed to mound morphology.

Macro- and micro-fauna from cold seeps in the Palmahim Disturbance (Israeli off-shore), with description of Waisiuconcha corsellii n.sp. (Bivalvia, Vesicomyidae)

Chemosymbiotic micro- and macro-fauna related to cold-seep sites were recovered in the Palmahim Disturbance (PD), offshore Israel, during EU EUROFLEETS2 SEMSEEP Cruise, by box-coring and Remotely Operated Vehicle (ROV) dives. No live macrofauna was identified in the collected sediments, with the exception of the seep-related crustacean Calliax lobata (de Gaillande and Lagardère, 1966). Numerous Calliax claws testify the past colonization of these soft bottoms by several generations of this ghost shrimp. After sediment sieving on 1 mm, we identified gastropods belonging to the families Trochidae, Eucyclidae, unassigned Seguenzioidea (genus Anekes), Rissoidae, Elachisinidae, Raphitomidae, Mangeliidae, Architectonicidae, Orbitestellidae, and Acteonidae. The identified bivalves belong to the families Nuculidae, Yoldiidae, Mytilidae, Lucinidae, Thyasiridae, Semelidae, Kelliellidae, Vesicomyidae, Xylophagidae, and Cuspidariidae. A seep-related group of chemosymbiotic molluscs was detected, including: Taranis moerchii (Malm, 1861), Lurifax vitreus Warén and Bouchet, 2001, Idas ghisottii Warén and Carrozza, 1990, Lucinoma kazani Salas and Woodside, 2002, Thyasira biplicata (Philippi, 1836), Isorropodon perplexum Sturany, 1896, and the newly described Vesicomyid species Waisiuconcha corsellii n. sp., that represents also the first record of the genus Waisiuconcha in recent Mediterranean sediments.The ROV dives recorded local patches of several m2 of seafloor covered by dead shells of L. kazani, with a density of up to about 200 loose shells per square meter. The potential occurrence of seep-related foraminifera, among low-oxygen tolerant species, was explored by comparison with previously sampled adjacent localities, and lead to the identification of Chilostomella oolina, Globobulimina affinis and G. pseudospinescens as potential foraminiferal seep indicators in the southeastern Mediterranean Sea. The absence of live, seep-related fauna in surface sediments in the PD, where seepage has been confirmed, suggests intermittent activity and a pause or decline of the investigated seeps.

Notes on a remotely operated vehicle survey to describe reef ichthyofauna and habitats – Agulhas Bank, South Africa

Background: Despite their ecological and economic importance, reef habitats on the central Agulhas Bank, off the southern tip of Africa, remain poorly studied. The ichthyofauna of these habitats cannot be surveyed using trawl gear.Objective: Preliminary assessment of the use of a remotely operated vehicle (ROV) to investigate the ichthyofauna associated with deep reef habitats on the central Agulhas Bank.Method: Underwater visual surveys were carried out during ROV dives (maximum duration 60 minutes; area covered approximately 800 m2; maximum dive depth 100 m).Results discussion: The number of detected fish species (36) compares well with that reported from fishing surveys and commercial fisher data. Most (68%) fishes appeared to be undisturbed by the ROV. Species saturation was reached after a maximum of 135 minutes survey time, but species numbers increased and saturation times shortened (34 minutes minimum) with the introduction of bait.Conclusion: ROV surveys may represent a non-extractive alternative to assess demersal ichthyofaunal diversity in relation to habitat structure and benthic cover on temperate reefs around South Africa.

Acquisition procedures, processing methodologies and preliminary results of magnetic and ROV data collected during the TOMO-ETNA experiment

<p>The TOMO-ETNA experiment was devised for the investigation of the continental and oceanic crust beneath Mt. Etna volcano and northeastern Sicily up to the Aeolian Islands, through an active source study. In this experiment, a large amount of geophysical data was collected both inland and in the Ionian and Tyrrhenian Seas for identifying the major geological and structural features offshore Mt. Etna and NE Sicily. One of the oceanographic cruises organized within the TOMO-ETNA experiment was carried out on the hydrographic vessel “Galatea” by Italian Navy. During the cruise a detailed magnetic survey and a set of ROV (remotely operated vehicle) dives were performed offshore Mt. Etna. The magnetic survey allowed the compilation of a preliminary magnetic map revealing a clear direct relationship between volcanic structures and high frequency magnetic anomalies. Significant positive magnetic anomalies were identified offshore the Timpa area and along the easternmost portion of the Riposto Ridge <span>and</span> correlated to a primitive volcanic edifice and to shallow volcanic bodies, respectively. On the whole, the magnetic anomaly map highlights a clear SW-NE decreasing trend, where high amplitude positive magnetic anomaly pattern of the SW sector passes, northeastwardly, to a main negative one. ROV dives permitted to directly explore the shallowest sectors of the Riposto Ridge and to collect several videos and seafloor samples, allowing us to identify some locally developed volcanic manifestations.</p>

The TOMO-ETNA experiment: an imaging active campaign at Mt. Etna volcano. Context, main objectives, working-plans and involved research projects

<p>The TOMO-ETNA experiment was devised to image of the crust underlying the volcanic edifice and, possibly, its plumbing system by using passive and active refraction/reflection seismic methods. This experiment included activities both on-land and offshore with the main objective of obtaining a new high-resolution seismic tomography to improve the knowledge of the crustal structures existing beneath the Etna volcano and northeast Sicily up to Aeolian Islands. The TOMO ETNA experiment was divided in two phases. The first phase started on June 15, 2014 and finalized on July 24, 2014, with the withdrawal of two removable seismic networks (a Short Period Network and a Broadband network composed by 80 and 20 stations respectively) deployed at Etna volcano and surrounding areas. During this first phase the oceanographic research vessel “Sarmiento de Gamboa” and the hydro-oceanographic vessel “Galatea” performed the offshore activities, which includes the deployment of ocean bottom seismometers (OBS), air-gun shooting for Wide Angle Seismic refraction (WAS), Multi-Channel Seismic (MCS) reflection surveys, magnetic surveys and ROV (Remotely Operated Vehicle) dives. This phase finished with the recovery of the short period seismic network. In the second phase the Broadband seismic network remained operative until October 28, 2014, and the R/V “Aegaeo” performed additional MCS surveys during November 19-27, 2014. Overall, the information deriving from TOMO-ETNA experiment could provide the answer to many uncertainties that have arisen while exploiting the large amount of data provided by the cutting-edge monitoring systems of Etna volcano and seismogenic area of eastern Sicily.</p>

Comparison between ROV video and Agassiz trawl methods for sampling deep water fauna of submarine canyons in the Northwestern Mediterranean Sea with observations on behavioural reactions of target species

In this paper we present a comparison between Remotely Operated Vehicle (ROV) and Agassiz trawling methods for sampling deep-water fauna in three submarine canyons of the Northwestern Mediterranean Sea and describe the behavioural reactions of fishes and crustacean decapods to ROV approach. 10 ROV dives, where 3583 individuals were observed and identified to species level, and 8 Agassiz trawls were carried out in a depth range of 750–1500m. As noticed in previous studies, abundances of fishes and decapod crustaceans were much higher in the ROV videos than in Agassiz trawl samples, as the latter are designed for the retrieval of benthic, less motile species in permanent contact with the bottom. In our observations fish abundance was one order of magnitude higher with ROV (4110.22ind/km2) than with Agassiz trawl (350.88ind/km2), whereas decapod crustaceans were six times more abundant in ROV videos (6362.40ind/km2) than in Agassiz samples (1364.52ind/km2).The behaviour of highly motile fishes was analysed in terms of stationary positioning over the seafloor and avoidance or attraction to ROV approach. The most frequently occurring fish species Coelorinchus mediterraneus, Nezumia aequalis, Bathypterois dubius, Lepidion lepidion, Trachyrincuss scabrus and Polyacanthonotus rissoanus did not react to the presence of the ROV in most cases (>50%). Only B. dubius (11%), Lepidion lepidion (14.8%), P. rissoanus (41%) and T. scabrus (14.3%) reacted to ROV approach. More than 60% of less motile species, such as crustacean decapods, did not respond to ROV presence either. Only 33.3% of Geryon longipes, 36.2% of Munida spp. and 29.79% of Pagurus spp. were observed avoiding or defensively reacting to the ROV.The comparison of results obtained with ROV and trawl sampling is of ecological relevance since ROV can report observations in areas where trawling is technically unfeasible. The lack of reaction by most fish and crustacean decapod specimens further confirms that ROV surveying is an efficient technique to assess abundance and species composition in deep-sea waters for these motile species and questions trawl-based estimations.

Rapid assessment of octocoral diversity and habitat on Saba Bank, Netherlands Antilles.

Saba Bank is a large submerged platform (∼2200 km2), average depth 30 m, located 4 km southwest of Saba Island in Netherlands Antilles, Caribbean Sea. Ships traveling to and from oil terminals on nearby St. Eustatius routinely anchor on the Bank, damaging benthic megafauna. Gorgonian octocorals are vulnerable to anchor damage, and they are common and conspicuous in shallow water (15–50 m) around the banks. This prompted a rapid assessment of octocoral habitat and diversity. The primary objectives were to estimate total species richness and to characterize habitats vis a vis gorgonians. Landsat imagery and multibeam bathymetry were employed to identify random sites for quantitative transects. A Seabotix LBV200L remotely operated vehicle (ROV) and SCUBA were used to collect and survey to 130 m. A total of 14 scuba dives and 3 ROV dives were completed in 10 days. During that time, 48 octocoral species were collected, including two likely undescribed species in the genera Pterogorgia and Lytreia. Gorgonian richness was exceptional, but not all species were collected, because the species accumulation curve remained steeply inclined after all surveys. Two shallow-water gorgonian habitat types were identified using multidimensional scaling and hierarchical cluster analyses: 1) a high diversity, high density fore-reef environment characterized by Eunicea spp., Gorgonia spp., and Pseudopterogorgia spp. and 2) a low diversity, low density plateau environment characterized by Pseudopterogorgia acerosa, Pterogorgia guadalupensis, and Gorgonia mariae. The analyses support hypotheses of broad (∼15 km) habitat homogeneity (ANOSIM, P>0.05), but a significant difference between fore-reef and plateau environments (ANOSIM, P<0.05). However, there was some indication of habitat heterogeneity along the 15 km study section of the 50 km platform edge along the southeast rim. Our results highlight the complexity and biodiversity of the Saba Bank, and emphasize the need for more scientific exploration.

The Cleft revealed: Geologic, magnetic, and morphologic evidence for construction of upper oceanic crust along the southern Juan de Fuca Ridge

The geology and structure of the Cleft Segment of the Southern Juan de Fuca Ridge (JdFR) have been examined using high‐resolution mapping systems, observations by remotely operated vehicle (ROV), ROV‐mounted magnetometer, and the geochemical analysis of recovered lavas. Bathymetric mapping using multibeam (EM300) coupled with in situ observations that focused on near‐axis and flank regions provides a detailed picture of 0 to 400 ka upper crust created at the southern terminus of the JdFR. A total of 53 rock cores and 276 precisely located rock or glass samples were collected during three cruises that included sixteen ROV dives. Our observations of the seafloor during these dives suggest that many of the unfaulted and extensive lava flows that comprise and/or cap the prominent ridges that flank the axial valley emanate from ridge parallel faults and fissures that formed in the highly tectonized zone that forms the walls of the axial valley. The geochemically evolved and heterogeneous nature of these near‐axis and flank eruptions is consistent with an origin within the cooler distal edges of a crustal magma chamber or mush zone. In contrast, the most recent axial eruptions are more primitive (higher MgO), chemically homogeneous lobate, sheet, and massive flows that generate a distinct magnetic high over the axial valley. We suggest that the syntectonic capping volcanics observed off‐axis were erupted from near‐axis and flank fissures and created a thickened extrusive layer as suggested by the magnetic and seismic data. This model suggests that many of the lavas that comprise the elevated ridges that bound the axial valley of the Cleft Segment were erupted during the collapse of a magmatic cycle not during the robust phase that established a new magmatic cycle.

An evaluation of acoustic and video methods to estimate the abundance and vertical distribution of jellyfish

Four non-invasive methods (three acoustic and one video) were compared to estimate the abundance and vertical distribution of scyphomedusae, using the locally abundant coronate species Periphylla periphylla in Lurefjorden, north of Bergen, Norway, as the test organism. The acoustic methods included single-target quantification by, respectively, a hull-mounted 38 kHz split-beam echo sounder and a 675 kHz scanning sonar mounted on a remotely operated vehicle (ROV). Data from acoustic backscattering provided estimates of abundance and changes in the vertical position of scattering (= aggregation) layers. Vertical migration was also studied by acoustic target tracking, following single individuals as they ascended in the afternoon. The ROV-mounted scanning sonar missed an unidentified part in the lower size distribution of the target population. Vertical video profiles, conducted during ROV dives, provided the most detailed information on abundance and distribution, although uncertainties remained regarding the size distribution in the population.

Comparison of a Remotely Operated Vehicle and a Submersible for Estimating Abundance of Demersal Shelf Rockfishes in the Eastern Gulf of Alaska

Abstract A miniROVER MKI remotely operated vehicle (ROV) and the submersible Delta were compared for effectiveness in collecting abundance information on demersal shelf rockfishes, Sebastes spp., by means of strip transect sampling, in the eastern Gulf of Alaska. We attempted to run 18 transects with the submersible and 15 transects with the ROV. Seventeen submersible dives and seven ROV dives were completed; one submersible dive was aborted because of sea conditions, and eight ROV dives were aborted because of snags on bottom or other difficulties related to the rugged terrain. The ROV was effective only for covering transects in areas of low relief, such as soft bottom, cobble, and flat pavement. The ROV was not effective in high-relief, rocky areas typically inhabited by demersal shelf rockfishes. The submersible worked well in both low- and high-relief terrain. The submersible's utility for collecting information on demersal shelf rockfish abundance would be increased by using line transect rather tha...