• Energy Research
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• 14. Life underwater close

Since long ago, pelagic Sargassum mats have been known to be abundant in the Sargasso Sea, where they provide habitat to diverse organisms. However, over the last few years, massive amounts of pelagic Sargassum have reached the coast of several countries in the Caribbean and West Africa, causing economic and environmental problems. Aiming for lessening the impacts of the blooms, governments and private companies remove the seaweeds from the shore, but this process results expensive. The valorization of this abundant biomass can render Sargassum tides into an economic opportunity and concurrently solve their associated environmental problems. Despite the diverse fields where algae have found applications and the relevance of this recurrent situation, Sargassum biomass remains without large scale applications. Therefore, this review aims to present the potential uses of these algae, identifying the limitations that must be assessed to effectively valorize this bioresource. Due to the constraints identified for each of the presented applications, it is concluded that a biorefinery approach should be developed to effectively valorize this abundant biomass. However, there is an urgent need for investigations focusing on holopelagic Sargassum to be able to truly valorize this seaweed.

Vegetated coastal ecosystems, in particular mangroves, tidal marshes and seagrasses are highly efficient at sequestering and storing carbon, making them valuable assets for climate change mitigation and adaptation. The state of Queensland, in northeastern Australia, contains almost half of the total area of these blue carbon ecosystems in the country, yet there are few detailed regional or state-wide assessments of their total sedimentary organic carbon (SOC) stocks. We compiled existing SOC data and used boosted regression tree models to evaluate the influence of environmental variables in explaining the variability in SOC stocks, and to produce spatially explicit blue carbon estimates. The final models explained 75 % (for mangroves and tidal marshes) and 65 % (for seagrasses) of the variability in SOC stocks. Total SOC stocks in the state of Queensland were estimated at 569 ± 98 Tg C (173 ± 32 Tg C, 232 ± 50 Tg C, and 164 ± 16 Tg C from mangroves, tidal marshes and seagrasses, respectively). Regional predictions for each of Queensland's eleven Natural Resource Management regions revealed that 60 % of the state's SOC stocks occurred within three regions (Cape York, Torres Strait and Southern Gulf Natural Resource Management regions) due to a combination of high values of SOC stocks and large areas of coastal wetlands. Protected areas in Queensland play an important role in conserving SOC assets in Queensland's coastal wetlands. For example, ~19 Tg C within terrestrial protected areas, ~27 Tg C within marine protected areas and ~ 40 Tg C within areas of matters of State Environmental Significance. Using multi-decadal (1987-2020) mapped distributions of mangroves in Queensland; we found that mangrove area increased by approximately 30,000 ha from 1987 to 2020, which led to temporal fluctuations in mangrove plant and SOC stocks. We estimated that plant stocks decreased from ~45 Tg C in 1987 to ~34.2 Tg C in 2020, while SOC stocks remained relatively constant from ~107.9 Tg C in 1987 to 108.0 Tg C in 2020. Considering the level of current protection, emissions from mangrove deforestation are potentially very low; therefore, representing minor opportunities for mangrove blue carbon projects in the region. Our study provides much needed information on current trends in carbon stocks and their conservation in Queensland's coastal wetlands, while also contributing to guide future management actions, including blue carbon restoration projects.

Alcoholism and alcohol abuse represent a significant medical and societal problem, and have been thoroughly investigated in humans as well as using animal models. A less well understood aspect of alcohol related disorders is the possible effect of this drug on offspring whose parents were exposed prior to conception. The zebrafish has been successfully employed in alcohol research, however, the effect of exposing the parents to alcohol before fertilization of the eggs on offspring has not been demonstrated in this species. In this proof of concept study, we attempt to address this hiatus. We exposed both adult male and female zebrafish to 0.0% (control) or 0.5% (vol/vol) alcohol chronically for 7 days, subsequently bred the fish within their respective treatment group, collected the fertilized eggs, allowed them to develop, and tested the behavior of free-swimming offspring at their age of 7-9 days post-fertilization. We conducted the analysis in two genetically distinct quasi-inbred strains of zebrafish, AB and TL. Although gross morphology and general activity of the fish appeared unaffected, we found significant behavioral alterations in offspring of alcohol exposed parents compared to offspring of control parents in both strains. These alterations included robustly increased duration and reduced frequency of immobility, increased turn angle, and increased intra-individual variance of turn angle in offspring of alcohol exposed parents in both strains. The mechanisms underlying these behavioral effects or whether the effects are due to exposure of the father, the mother, or both to alcohol are unknown. Nevertheless, our results now set the stage for future studies with zebrafish that will address these questions.

In recent decades, oceans have been increasingly stressed by human activities that induced significant changes in its abiotic properties. Temperature increase, acidification, deoxygenation, deregulation of ocean currents are some examples of the anthropogenic impact on our oceans. In addition, pollution and overexploitation of marine resources will lead to severe and possibly irreversible changes for marine life. As environmental conditions directly affect the physiology of species, changes in species distribution and trophic interactions have already been observed and are expected to increase in the near future. Predicting future oceans is currently a great challenge for scientists that work to maintain, as best as possible, the goods and services they provide. In this context, ecologists have developed several modeling approaches able to simulate changes in both species distribution (Ecological Niche Models – ENMs) and interactions (static and dynamic food-web models). This chapter explains these two approaches in detail as well as the ways by which these two families of models can be coupled. In each part, the main existing algorithms will be reviewed, with their advantages and limitations, and some key examples retrieved from recent scientific literature will be presented. Finally, we will discuss the current issues of these methods and their potential improvement.

Abstract Marine gas hydrates mostly occur in high-water content and non-diagenetic submarine sediments without tight stratigraphic traps. Therefore, the seepage capability of overlying and underlying strata (OUS) serves as a crucial parameter to analyze hydrate production behaviors. This study focuses on the numerical simulation study on the effects of the seepage capability of OUS on hydrate production behaviors in depressurization-induced production of three-phase hydrate deposits using a horizontal well. As shown by the simulation results, in the early stage of hydrate production, the permeability of the OUS had little effects on gas production rates. In long-term hydrate production, the hydrate deposit with lower permeability OUS has higher cumulative gas production, larger gas-water ratio and hydrate dissociation scope, and less cumulative water production. Moreover, the hydrate production efficiency first decreased rapidly and then tended to be stable as the permeability of OUS increased, and hydrate production behaviors are similar while the permeability of OUS larger than 1.0 mD. Herein, a water-resisting layers were constructed in overlying and/or underlying strata to decrease the seepage capability of OUS. Compared to the original hydrate deposits, the cumulative gas production and gas-water ratio increased by 31% and 147%, respectively but the water production was only 76% on the 5th year of the simulated production in which water-resisting layers were designed. Furthermore, the water-resisting layer in underlying strata produced more significant effects on hydrate production efficiency than the layer in overlying strata. All these indicate that the low-permeability OUS (especially in underlying strata) can restrain fluid invading into hydrate reservoirs, increase the pressure gradient of hydrate reservoirs and significantly improve the hydrate production efficiency during long-term hydrate production. Therefore, water-proof reformation in OUS may be an effective method to improve the energy utilization efficiency and promote the process of hydrate industrialization. However, further research is needed.

Hydrofoil based tidal arrays have emerged as a promising solution for large-scale power generation due to their high efficiency, cost effectiveness, and minimal interferences to the marine environment. In order to further maximize their power production and economic viability, an efficient tandem-hydrofoil based closely-interconnected tidal array is proposed, where the fore and hindfoils are closely spaced and interconnected to achieve constructive foil-foil interactions for energy capture. The power production, energy efficiency, capacity density, and levelized cost of electricity are obtained using a comprehensive approach that combines water tunnel experiments and computational fluid dynamics modeling. The results demonstrate that the capacity density of the proposed tandem configuration achieves at least 3 times higher than those of existing studies, while the hydrofoil deployment density is 4 times higher. Moreover, the energy efficiency and capacity density can be enhanced by enlarging the forefoil pitching amplitude or shortening the inter-foil spacing. Furthermore, the levelized cost of electricity is minimized to 50% that of existing studies, achieved by enhancing the energy capture and reducing the capital expenditures, thereby maximizing the commercial potential of the proposed hydrofoil based tidal array. ; National Research Foundation (NRF) ; The authors would like to thank the Singapore Centre for 3D Printing, which is supported by the National Research Foundation, and the Prime Minister’s Office of Singapore under its Medium-Sized Centre funding scheme.

AbstractVariable resource use and responses to environmental conditions can lead to phenotypic diversity and distinct morphotypes within salmonids, including Arctic char (Salvelinus alpinus). Despite the cultural and economic importance of Arctic char in the Inuvialuit Settlement Region (ISR), limited data exist on the extent and presence of morphological diversity in this region. This is of concern for management given climate change impacts on regional fish populations. The authors investigated morphological diversity in anadromous Arctic char sampled during their summer marine migration‐residency period when seasonal harvesting occurs in a coastal mixed‐stock fishery. Geometric morphometric analysis was conducted using digital photographs of live Arctic char (n = 103) of which a sub‐set was subsequently implanted with acoustic transmitters (n = 90) and released, and their overwintering lakes determined using active acoustic telemetry surveys. Twenty‐three morphological landmarks were established and overlaid on digital images, and nine linear measurements of the body and head were recorded. Principle component analysis and K‐means clustering based on linear measurements categorised fish into three morphotypes: slender body and slim head (n = 31), small and short head with a small mouth (n = 46) and elongated head shape with large mouth (n = 26). Tagged individuals of the three morphotypes occupied all lakes with no distinction observed. The three Arctic char morphotypes detected in this coastal mixed‐stock fishery could represent adaptation to specific feeding–movement behaviours potentially tied to juvenile residency in freshwater systems, efficient exploitation of the marine prey pulse, or are relicts from ancestral types. To the authors’ knowledge, this study is the first to identify distinct Arctic char morphotypes occurring in sympatry in the marine environment. Identifying phenotypic diversity will assist management to promote the sustainability of this regional fishery.

The fluvial and aquatic ecosystem of the Tagus River and Entrepeñas reservoir located in the surrounding of the Trillo nuclear power plant (NPP) was evaluated from 1992 to 2008, considering the physical-chemical characteristics, metal content and radiological activity of the water, sediments, algae and fish. The water of both basins demonstrated pH, conductivity, COD, NO3- and DO values within a range considered as good quality and the water quality index (WQI) was found to be within a range of 71-90. Chemometric analysis revealed a shift in the river water (from upstream to downstream) affected by the concentration of salts and metals of natural origin, such as Fe and Al, and slight variations in temperature and radiological activity were detected due to the discharges from the NPP. The hydric conditions contributed to increase or decrease the metal concentration of the river water, the reservoir sediments, algae and fish. Fe and Al were found in higher concentration during drought periods and accumulated in sediments, algae and fish along the river course (from SP1 to SP3). Natural and artificial radionuclides found were 40K with an average of 245 Bq/kg in river sediments, 499 Bq/kg in reservoir sediments and 121 Bq/kg in fish, and 90Sr with a concentration between 0.40 and 1.30 Bq/kg in sediments. Contamination of the aquatic ecosystem with metals and radionuclides was low according to European legislation. In conclusion, this study provides additional elements aimed at understanding the dynamics of fluvial and lentic ecosystems under the influence of different disturbances.

In order to make adequate projections on the consequences of climate change stressors on marine organisms, it is important to know how impacts of these stressors are affected by the presence of other species. Here we assessed the direct effects of ocean warming (OW) and acidification (OA) along with non-consumptive effects (NCEs) of a predatory crab and/or a predatory snail on the habitat-forming mussel Perumytilus purpuratus. Mussels were exposed for 10-14 weeks to contrasting pCO2 (500 and 1400 μatm) and temperature (15 and 20 °C) levels, in the presence/absence of cues from one or two predator species. We compared mussel traits at sub-organismal (nutritional status, metabolic capacity-ATP production-, cell stress condition via HSP70 expression) and organismal (survival, oxygen consumption, growth, byssus biogenesis, clearance rates, aggregation) levels. OA increased the mussels' oxygen consumption; and OA combined with OW increased ATP demand and the use of carbohydrate reserves. Mussels at present-day pCO2 levels had the highest protein content. Under OW the predatory snail cues induced the highest cell stress condition on the mussels. Temperature, predator cues and the interaction between them affected mussel growth. Mussels grew larger at the control temperature (15 °C) when crab and snail cues were present. Mussel wet mass and calcification were affected by predator cues; with highest values recorded in crab cue presence (isolated or combined with snail cues). In the absence of predator cues in the trails, byssus biogenesis was affected by OA, OW and the OA × OW and OA × predator cues interactions. At present-day pCO2 levels, more byssus was recorded with snail than with crab cues. Clearance rates were affected by temperature, pCO2 and the interaction between them. The investigated stressors had no effects on mussel aggregation. We conclude that OA, OW and the NCEs may lead to neutral, positive or negative consequences for mussels.