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Oceans, Volume 2, Issue 2 (June 2021) – 8 articles

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Article
Future Changes in Tropical Cyclone and Easterly Wave Characteristics over Tropical North America
Oceans 2021, 2(2), 429-447; https://doi.org/10.3390/oceans2020024 - 10 Jun 2021
Cited by 1 | Viewed by 2046
Abstract
Tropical Cyclones (TCs) and Easterly Waves (EWs) are the most important phenomena in Tropical North America. Thus, examining their future changes is crucial for adaptation and mitigation strategies. The Community Earth System Model drove a three-member regional model multi-physics ensemble under the Representative [...] Read more.
Tropical Cyclones (TCs) and Easterly Waves (EWs) are the most important phenomena in Tropical North America. Thus, examining their future changes is crucial for adaptation and mitigation strategies. The Community Earth System Model drove a three-member regional model multi-physics ensemble under the Representative Concentration Pathways 8.5 emission scenario for creating four future scenarios (2020–2030, 2030–2040, 2050–2060, 2080–2090). These future climate runs were analyzed to determine changes in EW and TC features: rainfall, track density, contribution to seasonal rainfall, and tropical cyclogenesis. Our study reveals that a mean increase of at least 40% in the mean annual TC precipitation is projected over northern Mexico and southwestern USA. Slight positive changes in EW track density are projected southwards 10° N over the North Atlantic Ocean for the 2050–2060 and 2080–2090 periods. Over the Eastern Pacific Ocean, a mean increment in the EW activity is projected westwards across the future decades. Furthermore, a mean reduction by up to 60% of EW rainfall, mainly over the Caribbean region, Gulf of Mexico, and central-southern Mexico, is projected for the future decades. Tropical cyclogenesis over both basins slightly changes in future scenarios (not significant). We concluded that these variations could have significant impacts on regional precipitation. Full article
(This article belongs to the Special Issue Tropical Cyclone Future Projections)
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Review
Offshore Geological Hazards: Charting the Course of Progress and Future Directions
Oceans 2021, 2(2), 393-428; https://doi.org/10.3390/oceans2020023 - 31 May 2021
Cited by 1 | Viewed by 2475
Abstract
Offshore geological hazards can occur in any marine domain or environment and represent a serious threat to society, the economy, and the environment. Seismicity, slope sedimentary instabilities, submarine volcanism, fluid flow processes, and bottom currents are considered here because they are the most [...] Read more.
Offshore geological hazards can occur in any marine domain or environment and represent a serious threat to society, the economy, and the environment. Seismicity, slope sedimentary instabilities, submarine volcanism, fluid flow processes, and bottom currents are considered here because they are the most common hazardous processes; tsunamis are also examined because they are a secondary hazard generated mostly by earthquakes, slope instabilities, or volcanic eruptions. The hazards can co-occur and interact, inducing a cascading sequence of events, especially in certain contexts, such as tectonic indentations, volcanic islands, and canyon heads close to the coast. We analyze the key characteristics and main shortcomings of offshore geological hazards to identify their present and future directions for marine geoscience investigations of their identification and characterization. This review establishes that future research will rely on studies including a high level of multidisciplinarity. This approach, which also involves scientific and technological challenges, will require effective integration and interplay between multiscale analysis, mapping, direct deep-sea observations and testing, modelling, and linking offshore observations with onshore observations. Full article
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Communication
Humpback Whale Instigates Object Play with a Lion’s Mane Jellyfish
Oceans 2021, 2(2), 386-392; https://doi.org/10.3390/oceans2020022 - 24 May 2021
Viewed by 2421
Abstract
Cetaceans are well-known for their intelligence, charismatic nature, and curiosity. Many species, particularly odontocetes, are known to investigate and manipulate novel objects they encounter. Yet, disentangling the drivers of these behaviors and distinguishing between those that are simply playful and those which serve [...] Read more.
Cetaceans are well-known for their intelligence, charismatic nature, and curiosity. Many species, particularly odontocetes, are known to investigate and manipulate novel objects they encounter. Yet, disentangling the drivers of these behaviors and distinguishing between those that are simply playful and those which serve a specific function remains challenging due to a lack of direct observations and detailed descriptions of behaviors. This is particularly true for mysticetes such as humpback whales (Megaptera novaeangliae), as records of object use are far less common than in odontocetes. Here, we present evidence of novel object use from a first of its kind encounter between an individual humpback whale and a large lion’s mane jellyfish (Cyanea capillata) in the coastal waters off New England. We detail the interaction and discuss possible drivers for the behavior, with a focus on cetacean innovation, ectoparasite removal, and wound healing. Full article
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Article
The Interactive Role of Hydrocarbon Seeps, Hydrothermal Vents and Intermediate Antarctic/Mediterranean Water Masses on the Distribution of Some Vulnerable Deep-Sea Habitats in Mid Latitude NE Atlantic Ocean
Oceans 2021, 2(2), 351-385; https://doi.org/10.3390/oceans2020021 - 26 Apr 2021
Cited by 4 | Viewed by 1516
Abstract
In this work, we integrate five case studies harboring vulnerable deep-sea benthic habitats in different geological settings from mid latitude NE Atlantic Ocean (24–42° N). Data and images of specific deep-sea habitats were acquired with Remoted Operated Vehicle (ROV) sensors (temperature, salinity, potential [...] Read more.
In this work, we integrate five case studies harboring vulnerable deep-sea benthic habitats in different geological settings from mid latitude NE Atlantic Ocean (24–42° N). Data and images of specific deep-sea habitats were acquired with Remoted Operated Vehicle (ROV) sensors (temperature, salinity, potential density, O2, CO2, and CH4). Besides documenting some key vulnerable deep-sea habitats, this study shows that the distribution of some deep-sea coral aggregations (including scleractinians, gorgonians, and antipatharians), deep-sea sponge aggregations and other deep-sea habitats are influenced by water masses’ properties. Our data support that the distribution of scleractinian reefs and aggregations of other deep-sea corals, from subtropical to north Atlantic could be dependent of the latitudinal extents of the Antarctic Intermediate Waters (AAIW) and the Mediterranean Outflow Waters (MOW). Otherwise, the distribution of some vulnerable deep-sea habitats is influenced, at the local scale, by active hydrocarbon seeps (Gulf of Cádiz) and hydrothermal vents (El Hierro, Canary Island). The co-occurrence of deep-sea corals and chemosynthesis-based communities has been identified in methane seeps of the Gulf of Cádiz. Extensive beds of living deep-sea mussels (Bathymodiolus mauritanicus) and other chemosymbiotic bivalves occur closely to deep-sea coral aggregations (e.g., gorgonians, black corals) that colonize methane-derived authigenic carbonates. Full article
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Article
After the Fall: The Demographic Destiny of a Gorgonian Population Stricken by Catastrophic Mortality
Oceans 2021, 2(2), 337-350; https://doi.org/10.3390/oceans2020020 - 19 Apr 2021
Viewed by 997
Abstract
In recent years, the frequency of mass mortality events in marine ecosystems has increased, and several populations of benthic organism have been affected, reducing their density and changing their size and age structure. Few details are known about the dynamics of these populations [...] Read more.
In recent years, the frequency of mass mortality events in marine ecosystems has increased, and several populations of benthic organism have been affected, reducing their density and changing their size and age structure. Few details are known about the dynamics of these populations over long time intervals. In late summer of both 1999 and 2003 two drastic mass mortality events, co-occurring with anomalous temperature increases, affected the northwestern Mediterranean rocky coastal communities. Due to these events the Paramuricea clavata population living at the western edge of La Spezia Gulf (Italy) was stricken, and 78% of the colonies died. This population was monitored from 1998 (pre-mortality) until 2013. This paper deals with the photographic sampling of permanent plots carried out in 2013. The findings were compared with those from the previous sampling series. This long-term, non-destructive sampling highlights the demographic trajectory of the octocoral population there after two anomalous mortality events, indicating that some new drop-point between local extinction and complete recovery may be have been reached. Long-term monitoring (including pre-mortality data) could allow evaluating the effects of global climate change on the conservation of impacted populations. Full article
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Article
Measurements of Bicarbonate in Water Containing Ocean-Level Sulfate Using a Simple Multi-Pass Optical Raman System
Oceans 2021, 2(2), 330-336; https://doi.org/10.3390/oceans2020019 - 06 Apr 2021
Cited by 1 | Viewed by 1000
Abstract
The concentration of dissolved inorganic carbon in the oceans at depths of a few meters to thousands of meters is a critical parameter for understanding global warming. The concentration is both pH dependent and depth dependent. Current analysis that employs pH meters must [...] Read more.
The concentration of dissolved inorganic carbon in the oceans at depths of a few meters to thousands of meters is a critical parameter for understanding global warming. The concentration is both pH dependent and depth dependent. Current analysis that employs pH meters must account for several other parameters, such as salinity, temperature, pressure, and the dissolved carbon’s form, carbon dioxide, bicarbonate, or carbonate. Recently, Raman spectroscopy has been used to measure these forms directly in water at ~1000 ppm, which is unfortunately insufficient for typical ocean concentrations, such as ~115 ppm bicarbonate near the surface. Here, we employed a simple multi-pass optical system, a flat mirror to reflect the laser back through the sample, and a concave mirror opposite the entrance slit that effectively doubled the laser power and the collected Raman photons, respectively. This multi-pass optical Raman system with a 1.5 W, 532 nm laser was used to measure 30 ppm bicarbonate in water that contained 2650 ppm sulfate to simulate ocean water, a bicarbonate concentration well below that near the ocean surface. Furthermore, spectral analysis employed the bicarbonate C=O symmetric stretch at 1360 cm−1 instead of the C–OH stretch at 1015 cm−1 to avoid the intense, overlapping sulfate SO4 symmetric stretch at 985 cm−1. The calculated standard deviation of ~5 ppm for the described approach suggests that accurate measurement of bicarbonate in situ is possible, which has been, heretofore, either calculated based on pH or measured in a lab. Full article
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Article
Mapping Sub-Metre 3D Land-Sea Coral Reefscapes Using Superspectral WorldView-3 Satellite Stereoimagery
Oceans 2021, 2(2), 315-329; https://doi.org/10.3390/oceans2020018 - 02 Apr 2021
Cited by 4 | Viewed by 1573
Abstract
Shallow coral reefs ensure a wide portfolio of ecosystem services, from fish provisioning to tourism, that support more than 500 million people worldwide. The protection and sustainable management of these pivotal ecosystems require fine-scale but large-extent mapping of their 3D composition. The sub-metre [...] Read more.
Shallow coral reefs ensure a wide portfolio of ecosystem services, from fish provisioning to tourism, that support more than 500 million people worldwide. The protection and sustainable management of these pivotal ecosystems require fine-scale but large-extent mapping of their 3D composition. The sub-metre spaceborne imagery can neatly produce such an expected product using multispectral stereo-imagery. We built the first 3D land-sea coral reefscape mapping using the 0.3 m superspectral WorldView-3 stereo-imagery. An array of 13 land use/land cover and sea use/sea cover habitats were classified using sea-, ground- and air-truth data. The satellite-derived topography and bathymetry reached vertical accuracies of 1.11 and 0.89 m, respectively. The value added of the eight mid-infrared (MIR) channels specific to the WorldView-3 was quantified using the classification overall accuracy (OA). With no topobathymetry, the best combination included the eight-band optical (visible + near-infrared) and the MIR8, which boosted the basic blue-green-red OA by 9.58%. The classes that most benefited from this MIR information were the land use “roof” and land cover “soil” classes. The addition of the satellite-derived topobathymetry to the optical+MIR1 produced the best full combination, increasing the basic OA by 9.73%, and reinforcing the “roof” and “soil” distinction. Full article
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Article
Divergent Proteomic Responses Offer Insights into Resistant Physiological Responses of a Reef-Foraminifera to Climate Change Scenarios
Oceans 2021, 2(2), 281-314; https://doi.org/10.3390/oceans2020017 - 01 Apr 2021
Cited by 3 | Viewed by 1755
Abstract
Reef-dwelling calcifiers face numerous environmental stresses associated with anthropogenic carbon dioxide emissions, including ocean acidification and warming. Photosymbiont-bearing calcifiers, such as large benthic foraminifera, are particularly sensitive to climate change. To gain insight into their responses to near-future conditions, Amphistegina lobifera from the [...] Read more.
Reef-dwelling calcifiers face numerous environmental stresses associated with anthropogenic carbon dioxide emissions, including ocean acidification and warming. Photosymbiont-bearing calcifiers, such as large benthic foraminifera, are particularly sensitive to climate change. To gain insight into their responses to near-future conditions, Amphistegina lobifera from the Gulf of Aqaba were cultured under three pCO2 conditions (492, 963, 3182 ppm) crossed with two temperature conditions (28 °C, 31 °C) for two months. Differential protein abundances in host and photosymbionts were investigated alongside physiological responses and microenvironmental pH gradients assessed via proton microsensors. Over 1000 proteins were identified, of which > 15% varied significantly between treatments. Thermal stress predominantly reduced protein abundances, and holobiont growth. Elevated pCO2 caused only minor proteomic alterations and color changes. Notably, pH at the test surface decreased with increasing pCO2 under all light/dark and temperature combinations. However, the difference between [H+] at the test surface and [H+] in the seawater—a measure of the organism’s mitigation of the acidified conditions—increased with light and pCO2. Combined stressors resulted in reduced pore sizes and increased microenvironmental pH gradients, indicating acclimative mechanisms that support calcite test production and/or preservation under climate change. Substantial proteomic variations at moderate-pCO2 and 31 °C and putative decreases in test stability at high-pCO2 and 31 °C indicate cellular modifications and impacts on calcification, in contrast to the LBFs’ apparently stable overall physiological performance. Our experiment shows that the effects of climate change can be missed when stressors are assessed in isolation, and that physiological responses should be assessed across organismal levels to make more meaningful inferences about the fate of reef calcifiers. Full article
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