Shallow Water Coastal Environments Research Articles

Long range acoustic detection of gas bubbles in a shallow water coastal environment

As the world economy moves to net zero carbon dioxide (CO2) emissions, carbon capture and storage (CCS) is recognised a mitigation mechanism in the suite of technology options. Liquified CO2 injection into offshore subsea reservoirs will be one of the CCS strategies used. Despite being improbable, CO2 leaks could occur and impact the effectiveness of this CO2 mitigation option and undermine confidence in its use as part of the suite of tools to combat climate change. To satisfy public safety expectations and environmental regulatory requirements, long-term measurement, monitoring, and verification (MM&V) plans that are affordable will be needed as part of any commercial CCS operation. Active acoustic methods are a well-suited technique as they can detect gas bubbles in the water column at extremely low flow rates. A bespoke detection system, the Echosounder Detection of Gas Events (EDGE) was developed with the goals of long-duration monitoring and detection of low flow gas bubble releases at long ranges; the literature suggests flow rates of <2 L min−1 will be readily detectable using active acoustics, well below the upper limits of a release of 1 % of stored CO2 over a 1000 year timeframe proposed by IPCC (2005). The EDGE system was housed on a seafloor lander with a battery powered scientific echosounder connected to a narrow-beam horizontally orientated transducer mounted on a turret that rotates through 360 deg. The effectiveness of the EDGE system was tested in a range of weather conditions during two six-month deployments in ∼ 20 m depth at a proposed CCS storage site, CarbonNet, situated off the coast of Victoria, Australia. Separate experiments with controlled gas releases were conducted at a local site at Hobart, Australia to establish the detection capability at range for low flow rates. These experiments found very small gas-releases (< 2 L min−1) could be detected at ranges of up to 378 m. The ability of long-term deployment of the EDGE at the proposed CCS site and the local experiments establishing range-detection ability have demonstrated that active acoustic systems can meet the dual objectives of sustained and wide-area monitoring as a key part of an aquatic based MM&V framework.

AUSSEABED: A NATIONAL PROGRAM OF COLLABORATION TO MAXIMISE AUSTRALIA’S SEABED MAPPING EFFORTS

High quality seabed data are fundamental to a wide range of engineering, management and science research applications stretching from shallow-water coastal environments, across the shelf and out on to the abyssal sea floor. Coastal applications require high-resolution, quality bathymetry data to support models for understanding currents and waves, sediment transport and erosion, hazard and risk assessment as well as ensuring safe navigation and informing development associated with infrastructure and commercial projects. Combined with other seabed data types, the information supports research around changing climate and marine biodiversity and provides development opportunities associated with energy and food production in support of the Blue Economy.

Transcriptional response of the calcification and stress response toolkits in an octocoral under heat and pH stress.

Up to one-third of all described marine species inhabit coral reefs, but the future of these hyperdiverse ecosystems is insecure due to local and global threats, such as overfishing, eutrophication, ocean warming and acidification. Although these impacts are expected to have a net detrimental effect on reefs, it has been shown that some organisms such as octocorals may remain unaffected, or benefit from, anthropogenically induced environmental change, and may replace stony corals in future reefs. Despite their potential importance in future shallow-water coastal environments, the molecular mechanisms leading to the resilience to anthropogenically induced stress observed in octocorals remain unknown. Here, we use manipulative experiments, proteomics and transcriptomics to show that the molecular toolkit used by Pinnigorgia flava, a common Indo-Pacific gorgonian octocoral, to deposit its calcium carbonate skeleton is resilient to heat and seawater acidification stress. Sublethal heat stress triggered a stress response in P. flava but did not affect the expression of 27 transcripts encoding skeletal organic matrix (SOM) proteins. Exposure to seawater acidification did not cause a stress response but triggered the downregulation of many transcripts, including an osteonidogen homologue present in the SOM. The observed transcriptional decoupling of the skeletogenic and stress-response toolkits provides insights into the mechanisms of resilience to anthropogenically driven environmental change observed in octocorals.

Using principal component analysis for marine soundscape research: A case study from Taiwan

Recent years have seen enormous increases in research on marine soundscape, as underwater acoustic sensors are becoming more affordable, coupled with a growing interest and increased concerns on underwater noise impacts on marine fauna. However, when faced with large amounts of data, there are significant challenges regarding how to analyze large datasets effectively and accurately to make informed decisions. In this study, we used principal component analysis (PCA) to analyze the temporal, spatial, and spectral patterns of the soundscape from major contributing sources in a shallow water coastal environment at two locations in Taiwan in early and late summer of 2012. Acoustic intensity levels were analyzed in three frequency bands: 150–300 Hz, 1.2–2.4 kHz, and 3–6 kHz. The PCA results show higher acoustic intensity in the 1.2–2.4 kHz band at night than during daytime hours, and relatively high acoustic intensity levels overall in the 150–300 Hz frequency at all times. In addition, a large temporal relationship was observed between early and late summer in the 1.2–2.4 kHz band. The results show that PCA has the potential to provide a simple but reliable way to quantify the dynamics of marine soundscapes.

The influence of bait on remote underwater video observations in shallow-water coastal environments associated with the North-Eastern Atlantic.

The use of baited remote underwater video (BRUV) for examining and monitoring marine biodiversity in temperate marine environments is rapidly growing, however many aspects of their effectiveness relies on assumptions based on studies from the Southern Hemisphere. The addition of bait to underwater camera systems acts as a stimulus for attracting individuals towards the camera field of view, however knowledge of the effectiveness of different bait types in northern temperate climbs is limited, particularly in dynamic coastal environments. Studies in the Southern Hemisphere indicate that oily baits are most effective whilst bait volume and weight do not impact BRUV effectiveness to any great degree. The present study assesses the influence of four bait types (mackerel, squid, crab and no bait (control)) on the relative abundance, taxonomic diversity and faunal assemblage composition at two independent locations within the North-Eastern Atlantic region; Swansea Bay, UK and Ria Formosa Lagoon, Portugal. Two different bait quantities (50 g and 350 g) were further trialled in Swansea Bay. Overall, patterns showed that baited deployments recorded statistically higher values of relative abundance and taxonomic diversity when compared to un-baited deployments in Swansea Bay but not in Ria Formosa Lagoon. No statistical evidence singled out one bait type as best performing for attracting higher abundances and taxonomic diversity in both locations. Faunal assemblage composition was however found to differ with bait type in Swansea Bay, with mackerel and squid attracting higher abundances of scavenging species compared to the crab and control treatments. With the exception of squid, bait quantity had minimal influence on bait attractiveness. It is recommended for consistency that a minimum of 50 g of cheap, oily fish such as mackerel is used as bait for BRUV deployments in shallow dynamic coastal environments in the North-Eastern Atlantic Region.

Trophic niche segregation allows range-extending coral reef fishes to co-exist with temperate species under climate change.

Changing climate is forcing many terrestrial and marine species to extend their ranges poleward to stay within the bounds of their thermal tolerances. However, when such species enter higher latitude ecosystems, they engage in novel interactions with local species, such as altered predator-prey dynamics and competition for food. Here, we evaluate the trophic overlap between range-extending and local fish species along the east coast of temperate Australia, a hotspot for ocean warming and species range extensions. Stable isotope ratios (δ15 N and δ13 C) of muscle tissue and stomach content analysis were used to quantify overlap of trophic niche space between vagrant tropical and local temperate fish communities along a 730km (6°) latitudinal gradient. Our study shows that in recipient temperate ecosystems, sympatric tropical and temperate species do not overlap significantly in their diet-even though they forage on broadly similar prey groups-and are therefore unlikely to compete for trophic niche space. The tropical and temperate species we studied, which are commonly found in shallow-water coastal environments, exhibited moderately broad niche breadths and local-scale dietary plasticity, indicating trophic generalism. We posit that because these species are generalists, they can co-exist under current climate change, facilitating the existence of novel community structures.

Factors Determining Benthic Foraminiferal Distribution in the Shallow Water Coastal Environments of Southwest Nigeria Sector of the Gulf of Guinea

Factors Determining Benthic Foraminiferal Distribution in the Shallow Water Coastal Environments of Southwest Nigeria Sector of the Gulf of Guinea

Fossil whale barnacles from the lower Pleistocene of Sicily shed light on the coeval Mediterranean cetacean fauna

We report on three shells of whale barnacle (Cirripedia: Coronulidae) collected from Pleistocene shallow-marine deposits exposed at Cinisi (northwestern Sicily, southern Italy). These specimens are identified as belonging to the extinct species Coronula bifida BRONN, 1831. Calcareous nannoplankton analysis of the sediment hosting the coronulid remains places the time of deposition between 1.93 and 1.71 Ma (i.e., at the Gelasian-Calabrian transition), an interval during which another deposit rich in whale barnacles exposed in southeastern Apulia (southern Italy) formed. Since Coronula LAMARCK, 1802, is currently found inhabiting the skin of humpback whales [Cetacea: Balaenopteridae: Megaptera novaeangliae (BOROWSKI, 1781)], and considering that the detachment of extant coronulids from their hosts' skin has been mainly observed in occurrence of cetacean breeding/calving areas, the material here studied supports the existence of a baleen whale migration route between the central Mediterranean Sea (the putative reproductive ground) and the North Atlantic (the putative feeding ground) around 1.8 Ma, when several portions of present-day southern Italy were still submerged. The early Pleistocene utilization of the epeiric seas of southern Italy as breeding/calving areas by migrating mysticetes appears to be linked to the severe climatic degradation that has been recognized at the Gelasian-Calabrian transition and that is marked in the fossil record of the Mediterranean Basin by the appearance of northern guests such as Arctica islandica (LINNAEUS, 1767) (Bivalvia: Veneroida). The subsequent abandonment of the Mediterranean Sea by most species of mysticetes is likely to have resulted from the progressive emergence of shallow-water coastal environments that occurred in Calabrian and Middle Pleistocene times.

A Paleoarchean coastal hydrothermal field inhabited by diverse microbial communities: the Strelley Pool Formation, Pilbara Craton, Western Australia.

The 3.4-Ga Strelley Pool Formation (SPF) at the informally named 'Waterfall Locality' in the Goldsworthy greenstone belt of the Pilbara Craton, Western Australia, provides deeper insights into ancient, shallow subaqueous to possibly subaerial ecosystems. Outcrops at this locality contain a thin (<3 m) unit of carbonaceous and non-carbonaceous cherts and silicified sandstones that were deposited in a shallow-water coastal environment, with hydrothermal activities, consistent with the previous studies. Carbonaceous, sulfide-rich massive black cherts with coniform structures up to 3 cm high are characterized by diverse rare earth elements (REE) signatures including enrichment of light [light rare earth elements (LREE)] or middle rare earth elements and by enrichment of heavy metals represented by Zn. The massive black cherts were likely deposited by mixing of hydrothermal and non-hydrothermal fluids. Coniform structures in the cherts are characterized by diffuse laminae composed of sulfide particles, suggesting that unlike stromatolites, they were formed dominantly through physico-chemical processes related to hydrothermal activity. The cherts yield microfossils identical to previously described carbonaceous films, small and large spheres, and lenticular microfossils. In addition, new morphological types such as clusters composed of large carbonaceous spheroids (20-40 μm across each) with fluffy or foam-like envelope are identified. Finely laminated carbonaceous cherts are devoid of heavy metals and characterized by the enrichment of LREE. This chert locally contains conical to domal structures characterized by truncation of laminae and trapping of detrital grains and is interpreted as siliceous stromatolite formed by very early or contemporaneous silicification of biomats with the contribution of silica-rich hydrothermal fluids. Biological affinities of described microfossils and microbes constructing siliceous stromatolites are under investigation. However, this study emphasizes how diverse the microbial community in Paleoarchean coastal hydrothermal environment was. We propose the diversity is at least partially due to the availability of various energy sources in this depositional environment including reducing chemicals and sunlight.

연안류 추적 장치 개발 및 모형 실험

Longshore current is main transportation mean causing movement of bed load and suspended particle in coastal waters, and effective measurement method and suitable equipment for shallow water coastal environment where is frequently exposed to atmosphere. Measurement equipment for longshore drift was designed and miniature model was applied to Gyeongpo beach in May and June, 2014. The equipment consists of three main elements, spheroid outer casing, spheroid inner casing, observation module equipped with GPS. Gyroscope principle was applied to observation module, and GPS receiver always can be directed upwards. Miniature models were installed along Gyeonpo beach, and it was well to track the flow of longshore current. This research described the design and function of the equipment and results of field experiments.

Impact of short-term salinity stress on larval development of the marine gastropod Crepipatella fecunda (Calyptraeidae)

Shallow-water coastal environments suffer frequent reductions in salinity due to heavy rains. This creates stressful conditions for the organisms found there, particularly for the early stages of development, including pelagic larvae. Freshly hatched larvae of the gastropod Crepipatella fecunda were exposed to different levels of salinity stress (32 (control), 25, 20 and 15) for a single 6h period. Subsequently, all veligers were maintained at normal control salinity (32) through metamorphosis. Periodic measurements were made of mortality, larval growth, and larval behavior. In particular, we measured changes in velar surface area, swimming velocity, clearance rate, oxygen consumption rate, shell growth rate, larval mortality, time to metamorphosis, and size at metamorphosis. The short exposure to salinity stress decreased subsequent mean growth rates at normal salinity and mean size at metamorphosis, but increased the duration of the planktonic period and the extent of larval mortality. It also reduced the rate at which the velar surface area increased relative to shell growth, and reduced mean larval swimming velocity. Mean oxygen consumption rates and clearance rates were also significantly lower for larvae that had been stressed early in larval life, compared with values obtained for control individuals. Exposure to low salinity for even a short time early in larval life can clearly have a substantial impact on the rest of larval development.

Combined Acoustic and Video Characterization of Coastal Environment by means of Unmanned Surface Vehicles

The aim of this work is the exploitation of an Unmanned Surface Vehicle (USV) for visual and acoustic characterization of the seafloor in shallow water coastal environments, through combined acquisition of echograms and video images. To this purpose, the employed vehicle is composed by two systems: i) a leading USV, equipped with an advanced mission control architecture, which performed a grid sampling over the study area; ii) a towed vehicle hosting an integrated system for acquisition of video and ultrasonic images, from the water column and the seafloor, coupled with a GPS receiver, which provided the geo-referencing of the survey. Data acquisition was carried out over different seafloor types, which included rock outcrops and sediments (mostly sand). The main key-points of employing such techniques to this peculiar field of coastal area monitoring are the possibility to perform automated missions and the capability to operate in very shallow water areas, usually not accessible to conventional boats.

Precision of high-resolution multibeam echo sounding coupled with high-accuracy positioning in a shallow water coastal environment

Over 4 years, repetitive bathymetric measurements of a shipwreck in the Gradyb tidal inlet channel in the Danish Wadden Sea were carried out using a state-of-the-art high-resolution multibeam echosounder (MBES) coupled with a real-time long range kinematic (LRK™) global positioning system. Seven measurements during a single survey in 2003 (n=7) revealed a horizontal and vertical precision of the MBES system of ±20 and ±2 cm, respectively, at a 95% confidence level. By contrast, four annual surveys from 2002 to 2005 (n=4) yielded a horizontal and vertical precision (at 95% confidence level) of only ±30 and ±8 cm, respectively. This difference in precision can be explained by three main factors: (1) the dismounting of the system between the annual surveys, (2) rougher sea conditions during the survey in 2004 and (3) the limited number of annual surveys. In general, the precision achieved here did not correspond to the full potential of the MBES system, as this could certainly have been improved by an increase in coverage density (soundings/m2), achievable by reducing the survey speed of the vessel. Nevertheless, precision was higher than that reported to date for earlier offshore test surveys using comparable equipment.

Comparison of two underwater acoustic communications techniques for multi-user access

Frequency hopped frequency shift keying (FHFSK) and code division multiple access (CDMA) are two different modulation techniques for multiple users to communicate with a single receiver simultaneously. In July 2003, these two techniques were tested alongside each other in a shallow water coastal environment off the coast of Kauai. A variety of instruments were used to measure the prevailing oceanography, enabling detailed modeling of the channel. The channel was acoustically probed using LFM waveforms and m-sequences as well. We will present the results of demodulating the FHFSK and CDMA waveforms and discuss modeling the channel for the purpose of predicting multi-user communications performance. a)Michael B. Porter, Paul Hursky, Martin Siderius (SAIC), Mohsen Badiey (UD), Jerald Caruthers (USM), William S. Hodgkiss, Kaustubha Raghukumar (SIO), Dan Rouseff, Warren Fox (APL-UW), Christian de Moustier, Brian Calder, Barbara J. Kraft (UNH), Keyko McDonald (SPAWARSSC), Peter Stein, James K. Lewis, and Subramaniam Rajan (SSI).

A natural laboratory for shallow gas: the R�as Baixas (NW Spain)

Interpretation of acoustic seismic records have allowed mapping of shallow gas accumulations and gas escape features in the Rias Baixas. X-ray photographs and voids of cores are semi-direct evidence of gassy sediments. Mapping of fluid-escape areas shows that these are related to the gas accumulations or at the intersections of faults. Analyses (GC-MS) of bubble samples collected in Simon Bay (Ria de Vigo) and across the whole ria confirm the presence of methane. The spatial distribution of gas escapes/accumulations and their vertical variations are interpreted as evidence of sedimentary facies control. The appearance of authigenic minerals (gypsum, pyrite and aragonite) and microbiological activity related to the seal facies are taken as evidence of the biogeochemical coupling processes. It is evident that these shallow-water coastal environments make significant contributions to the methane budget of the hydrosphere and atmosphere. It is also suggested that microbiological activity is favoured by gas escapes.

Model-based source localization in the 8–16 kHz band using the channel impulse response function

SignalEx tests have been conducted in a variety of shallow water coastal environments to relate the performance of acoustic communications systems to the prevailing oceanographic conditions. These tests have typically consisted of using a fixed receiver (one to four elements, spaced for diversity) and a transmitter drifting out to ranges beyond the minimum detectable level. During these tests, waveforms to probe the channel in the 8 to 16 kHz band were transmitted at regular intervals. These probe signals were used to test source localization algorithms at these high frequencies. Model-based source localization at these very high frequencies requires either very accurate modeling or algorithms inherently robust against model mismatch. Although the first couple of multipath arrivals can be stabilized from ping to ping, the later arrivals exhibit rapidly fluctuating amplitudes and times of arrival, due to the motion of the ocean surface, water column variability, and the varying bathymetry as the transmitter drifts in range. Measurements of the time-varying channel response and source localization results using the 8–16 kHz band SignalEx channel probes will be presented from sites at the New England Front and the Coronado Bank off San Diego.

Acoustic phase stability in a shallow-water environment

The formation of a synthetic aperture is dependent on the phase stability of the medium. Temporal and spatial phase stability of the medium were estimated from measurements taken during a high-frequency experiment conducted in August 1993 in the shallow-water coastal environment off Panama City, Florida. Phase stability was estimated from sequences of 150 0.5-ms and 1.0-ms pulses separated by 1-s intervals at experimental frequencies of 20, 40, 60, and 90 kHz. Phase fluctuations were found to contain both deterministic and random components which changed with time, indicating a changing propagation environment. Phase fluctuations were spatially correlated between both vertical and horizontal components of the receiving array. The relationship between acoustic phase stability and environmental factors is examined. Results of this analysis are compared with previous phase stability measurements [J. T. Christoff, C. D. Loggins, and E. L. Pipkin, J. Acoust. Soc. Am. 71, 1606–1607 (1982); P. T. Gough and M. P. Hayes, ibid. 86, 837–839 (1989)]. [Work sponsored by ONR.]