Ocean Conditions Research Articles

Evaluation of WRF model performance with different microphysics schemes for extreme rainfall prediction in Lagos, Nigeria: Implications for urban flood risk management

In Nigeria, particularly in urban areas like Lagos, flooding is a frequent natural hazard. In 2011, Lagos experienced one of its worst floods resulting in significant economic losses and displacement of people. In recent years, Lagos has continued to grapple with flooding challenges, with an equally significant flood episode occurring in 2021. This study focuses on predicting floods and forecasting extremely heavy rainfall in West Africa's equatorial zone using the Weather Research and Forecasting (WRF) model, particularly in humid tropical environments like Lagos. The study discusses the need to review existing flood models and adopt alternative flood models to address the limitations of flood prediction. As potential causes of these rainfall episodes, the interconnections between synoptic systems such as tropical easterly waves, southwesterly winds related to the West African Monsoon, and local topography and oceanic conditions are investigated. Three key metrics: root mean square error (RMSE), mean bias (MB), and mean absolute error (MAE) are used to assess the effectiveness of the computational model. Results indicate that the WRF model, specifically when using the Thompson parameterisation, can estimate the amount of rainfall accumulated over a 24-h period. This suggests that the model can predict the size of daily precipitation during intense rain events. The Thompson scheme shows better performance compared to the WSM6 scheme while evaluating the stations and episodes. During the rainfall episode on July 10, 2011, Thompson's spatial rainfall predictions were better than WSM6, resulting in a decrease in root mean square error (RMSE) of 15–31% depending on the area. Simulations of the July 2021 episode also show better performance, with a decrease in RMSE of 11–25% when comparing Thompson to WSM6 scheme. The Thompson scheme’s improved ability is directly linked to a more accurate depiction of the microphysical mechanisms that control the rainfall formation. By explicitly simulating the dynamics of ice crystals and graupel, it is possible to accurately replicate the processes of orographic lifting and moist convection that are responsible for driving intense monsoon precipitation. In addition, Thompson scheme shows a reduced degree of systemic bias in comparison to WSM6, with a 75% reduction in the average bias in rainfall accumulation over the research area. The combination of the advanced Thompson microphysics method and WRF's atmospheric dynamics shows a high level of accuracy in predicting intense rainfall and the risk of floods in this area with diverse tropical topography.

Synthetic aperture image enhancement with near-coinciding Nonuniform sampling case

Multireceiver synthetic aperture sonar (SAS) uses multiple receivers to collect echoed signals, leading to nonuniform sampling in the azimuth dimension if the moving distance between adjacent pings is not half the receiver array length. The filter bank reconstruction (FBR) method, based on matrix inversion, is commonly used to address this by reconstructing uniform data from nonuniform signals. However, in practice, near-coinciding sampling can occur due to inaccuracies in the towed velocity of the SAS system, influenced by ocean conditions. The signal correlation of these near-coinciding receivers is very strong, and thus the steering vectors corresponding to these receivers are not completely independent. This further leads to an ill-conditioned system transfer function matrix made up of the receiver steering vectors, and results in inaccurate calculations of inverse matrix. Consequently, the FBR method suffers from significant signal-to-noise ratio loss or fails to reconstruct uniform signals accurately. This degradation in signal quality directly impacts the accuracy of target reconstruction, leading to errors in identifying and locating targets. This paper quantitatively defines nonuniform sampling with near-coinciding samples and discusses performance loss in various cases. To enhance imaging performance, we propose a method for reconstructing uniform signals. Simulation results demonstrate that the proposed method outperforms the conventional FBR method, providing better target reconstruction and higher efficiency.

Fuzzy-based ensemble methodology for accurate long-term prediction and interpretation of extreme significant wave height events

Providing an accurate prediction of Significant Wave Height (SWH), and specially of extreme SWH events, is crucial for coastal engineering activities and holds major implications in several sectors as offshore renewable energy. With the aim of overcoming the challenge of skewness and imbalance associated with the prediction of these extreme SWH events, a fuzzy-based cascade ensemble of regression models is proposed. This methodology allows to remarkably improve the predictive performance on the extreme SWH values, by using different models specialised in different ranges on the target domain. The method’s explainability is enhanced by analysing the contribution of each model, aiding in identifying those predictor variables more characteristic for the detection of extreme SWH events. The methodology has been validated tackling a long-term SWH prediction problem, considering two case studies over the southwest coast of the United States of America. Both reanalysis data, providing information on various meteorological factors, and SWH measurements, obtained from the nearby stations and the station under examination, have been considered. The goodness of the proposed approach has been validated by comparing its performance against several machine learning and deep learning regression techniques, leading to the conclusion that fuzzy ensemble models perform much better in the prediction of extreme events, at the cost of a slight deterioration in the rest of the samples. The study contributes to advancing the SWH prediction field, specially, to understanding the behaviour behind extreme SWH events, critical for various sectors reliant on oceanic conditions.

Application of NiS modified WS2/TiO2heterostructure in photocathodic protection.

TiO2/WS2/NiS (TWN) composites with Type-Ⅱ heterojunction structure were prepared by hydrothermal method and titration method. The results reveal that TWN5 exhibits the best photoelectrochemical (PEC) performance, and its photocurrent density is 69% exceeding that of the unadulterated TiO2 photoanode. Under simulated ocean conditions, the self-corrosion potential of 304ss combined with TW5 and TWN5 photoanodes is reduced to -0.64 V and -0.7 V, respectively. The main reason is that contact surface of WS2 and TiO2 formed a Type II heterostructure, which accelerates the separation and diffusion process of photoinduced carriers. In addition, the plasmon resonance effect of NiS improves the ability to absorb visible light and the metallic-like feature of NiS also promotes charge separation.&#xD.

The Divergent Responses of Salinity Generalists to Hyposaline Stress Provide Insights Into the Colonisation of Freshwaters by Diatoms.

Environmental transitions, such as the salinity divide separating marine and fresh waters, shape biodiversity over both shallow and deep timescales, opening up new niches and creating opportunities for accelerated speciation and adaptive radiation. Understanding the genetics of environmental adaptation is central to understanding how organisms colonise and subsequently diversify in new habitats. We used time-resolved transcriptomics to contrast the hyposalinity stress responses of two diatoms. Skeletonema marinoi has deep marine ancestry but has recently invaded brackish waters. Cyclotella cryptica has deep freshwater ancestry and can withstand a much broader salinity range. Skeletonema marinoi is less adept at mitigating even mild salinity stress compared to Cyclotella cryptica, which has distinct mechanisms for rapid mitigation of hyposaline stress and long-term growth in low salinity. We show that the cellular mechanisms underlying low salinity tolerance, which has allowed diversification across freshwater habitats worldwide, includes elements that are both conserved and variable across the diatom lineage. The balance between ancestral and lineage-specific environmental responses in phytoplankton have shaped marine-freshwater transitions on evolutionary timescales and, on contemporary timescales, will affect which lineages survive and adapt to changing ocean conditions.

Prediction on Yellowfin Tuna (Thunnus albacares) Fishing Ground in Waters Near the Marshall Islands Based on SMOTETomek‐RF

ABSTRACTThis study monitored 37 longliners fishing in waters near the Marshall Islands from 2020 to 2022 by Liancheng Overseas Fishery (Shenzhen) Co., Ltd.'s operation management system. This study developed nine predictive models on the relationship between catch per unit effort (CPUE) data for yellowfin tuna (Thunnus albacares) and the environmental data. The environmental data integrate 48 variables, including eddy kinetic energy, chlorophyll a concentration, sea surface height, and additional measures of vertical oceanic conditions, alongside spatiotemporal parameters (year, month, day, longitude, and latitude). This study employed four spatial resolutions (0.25° × 0.25°, 0.5° × 0.5°, 1° × 1°, and 2° × 2°) to develop nine predictive models: KNN, RF, GBDT, CART, LightGBM, XGBoost, CatBoost, AdaBoost, and Stacking (RF, KNN, GBDT, and LR). These models, with a daily time resolution, were trained using 75% of the data and tested with the remaining 25%. The optimal spatial resolution and model were determined through a comprehensive comparison of model evaluation metrics across these spatial resolutions. The SMOTETomek algorithm was then applied to resample 75% of the data at the optimal spatial resolution, forming a new training dataset. This dataset was used to refine the model, subsequently tested with the remaining 25% of the data. Results indicated that (1) the optimal spatial resolution is 0.25° × 0.25° and the optimal model is RF; (2) the SMOTETomek algorithm enhances the model's predictive performance; and (3) the developed SMK‐RF model, exhibiting Acc and AUC values of 76.73% and 82.47%, respectively, accurately predicts the central fishing grounds for yellowfin tuna, consisting closely with actual fishing activity.

Predicting practical ship powering and speed loss in waves using added resistance test results

ABSTRACT This paper introduces a practical technique for accurately estimating ship propulsion and speed loss in the presence of waves. Utilising the previously established self-propulsion estimation framework, our approach enhances the method, which previously solely considered bare hull resistance, propeller performance, thrust deduction factor, and wake fraction, by incorporating added resistance test results. The full-scale DTC container ship is the focus of our investigation, providing a thorough examination of its performance in different sea states. The model's predictive abilities are enhanced by incorporating test data on added ship resistance, and it addresses a crucial aspect that is generally disregarded while estimating self-propulsion. This research is considered to be a contribution to the advancement of ship hydrodynamics, as it offers a practical and reliable tool for ship designers, operators, and researchers to accurately assess powering requirements and speed loss in harsh ocean conditions.

Otolith growth chronologies reveal distinct environmental sensitivities between and within shallow- and deep-water snappers

AbstractFish growth underpins individual fitness and population-level metrics, with fluctuations linked to environmental variability. Growth chronologies derived from otolith increment analysis are a powerful proxy to understand population responses to environmental change and productivity. Yet, long-term patterns of growth and their environmental drivers are better understood for shallow-water species compared to deep-water inhabitants. Additionally, focus is largely on adults, disregarding the potential influence of juvenile growth which is critical to size- and age-at-maturity. Here, we investigate the long-term growth patterns of two commercially important snapper species separated by depth in northwestern Australia’s coastal shelf waters, the shallow-water Lutjanus sebae (70 year chronology, 1950–2020) and the deep-water Etelis boweni (41 year chronology, 1973–2013). Annually-resolved otolith growth chronologies revealed distinct environmental sensitivities within (juveniles vs adults) and among (shallow- vs deep-water habitats) species. Within species, juveniles and adults responded differently to shared environmental stimuli, highlighting the importance of understanding the impacts of environmental effects and sensitivities for different life-history stages. Across species, L. sebae exhibited highly variable growth tied to local climate signals such as sea surface temperature and rainfall, while E. boweni displayed more stable growth patterns that only responded to interannual and decadal shifts in the environment (e.g. Pacific Decadal Oscillation). Our results highlight potential vulnerabilities of shallow-water species to future environmental perturbations compared to species residing at depth, as they are likely to encounter more extreme climate variability under future oceanic conditions. This study contributes valuable insights into understanding and managing the impacts of future environmental variability on fisheries sustainability, emphasising the need for continued research across species and habitats.

Hydrodynamic exposure – on the quest to deriving quantitative metrics for mariculture sites

This work attempts to define metrics for hydrodynamic exposure, using known oceanographic variables to provide a universal site assessment method for mariculture structures. Understanding environmental conditions driving open-ocean mariculture siting is crucial in establishing consistent ocean governance, minimizing adverse environmental impacts, and facilitating economically sustainable farm operations. To provide a metric of oceanic conditions and associated requirements for structural design and operation of aquaculture systems, six Exposure Indices (EI) are proposed that consider physical energy levels related to hydrodynamic forces at a site. Four of the proposed indices consider only environmental conditions, while the other two also consider the dimensions of the gear that is exposed to the external loads. These indices are: Exposure Velocity (EV), Exposure Velocity at Reference Depth (EVRD), Specific Exposure Energy (SEE), Depth-integrated Energy Flux (DEF), Structure-centered Depth-integrated Energy (SDE), and a Structure-centered Drag-to-Buoyancy Ratio (SDBR). While these indices are derived with a focus on aquaculture structures, they may also have applications for estimating biological stressors and operational challenges. The proposed exposure indices were evaluated for a range of known aquaculture sites around the world. A sensitivity analysis was conducted that quantified the relationship between the exposure indices and storm event return period. At a regional scale, hindcast numerical data for the German Bight combined with calculations of 50-year extreme values were used to calculate and map each proposed index spatially. Resulting maps showed that exposure is not simply a function of distance from shore. The six indices show plausible performance regarding the objective assessment of aquaculture sites. The authors herein present the indices to the aquaculture and ocean engineering communities for discussion, application, and potential adoption of one or more of the proposed indices.

Ferric iron stabilization at deep magma ocean conditions.

Fe2O3 produced in a deep magma ocean in equilibrium with core-destined alloy sets the early redox budget and atmospheric composition of terrestrial planets. Previous experiments (≤28 gigapascals) and first-principles calculations indicate that a deep terrestrial magma ocean produces appreciable Fe3+ but predict Fe3+/ΣFe ratios that conflict by an order of magnitude. We present Fe3+/ΣFe of glasses quenched from melts equilibrated with Fe alloy at 38 to 71 gigapascals, 3600 to 4400 kelvin, analyzed by synchrotron Mössbauer spectroscopy. These indicate Fe3+/ΣFe of 0.056 to 0.112 in a terrestrial magma ocean with mean alloy-silicate equilibration pressures of 28 to 53 gigapascals, producing sufficient Fe2O3 to account for the modern bulk silicate Earth redox budget and surficial conditions near or more oxidizing than the iron-wüstite buffer, which would stabilize a primitive CO- and H2O-rich atmosphere.

Nonlinear analysis of hydrodynamics of a shallow-draft floating wind turbine

AbstractThis study investigates numerically the dynamic responses of the T-Omega Wind novel concept of Floating Offshore Wind Turbine. The turbine is light-weight, has a shallow-draft and a relatively high centre of gravity that allows it to glide over harsh marine environments. The turbine responses are studied under regular wave excitation, considering most probable ranges of discrete sea wave heights and periods representative of real ocean conditions. A multibody virtual model is developed, simplified to a rigid 6 DOF system and experimentally validated in the state-of-art Marine Simulator to define the types of dynamical responses for both “Low” and “High” Sea States. The dynamics of coupled heave and pitch DOFs are evaluated with time histories, phase-plane portraits, Poincaré sections and FFT analyses to conclude that period-1 stable solutions exist for all studied cases of “Low Sea States”, whereas period-2, period-3 and period-4 periodic responses are identified for short wave periods of excitation under “High Sea States” conditions. Simulation results show that regions where period-1 responses exist are highly sensitive to wave height and can widen as the wave amplitude reduces. Finally, the turbines’ nonlinearities generated by the floats’ geometry are observed in this dynamical system, which are identified to be related to variation in float waterplane area and particularly observable for “High Sea States”.

The impact of virtual reality exposure on ocean connectedness and consumer responses to single-use packaging

Efforts to mitigate plastic packaging pollution include behavioural strategies aimed at shifting consumer perceptions and behaviour. Connectedness to nature, and more recently ocean connectedness, has been associated with pro-environmental intentions regarding single-use packaging. Two experimental studies were conducted to examine the potential of Virtual Reality (VR) technologies in promoting ocean connectedness and shifting consumer perceptions around packaging and its environmental qualities.To assess the influence of the VR content, in Study 1 (n = 94), participants were briefly exposed to an oceanic VR environment or an urban VR experience. Levels of ocean connectedness, both explicit and implicit, were measured after the VR manipulation using an Inclusion of Nature in Self (INS) measure and an Implicit Association Test (IAT). Participants then rated a variety of packaging options that were systematically manipulated in terms of type of raw material (e.g. plastic) and recyclability. The ocean VR condition showed higher levels of ocean connectedness on the adapted explicit INS measure, but not on the IAT measure, and there were no differences between the conditions in perceptions around packaging materials.Study 2 (n = 118) expanded on the previous study by adding a third condition: the participants were exposed to an oceanic VR environment, a built VR environment, or a non-VR task (cognitive task). The ocean VR condition showed higher levels of explicit ocean connectedness, as measured with the INS, than the other two conditions, but again there were no differences in implicit ocean connectedness. However, the ocean VR condition showed more critical perceptions around packaging overall in comparison to the built VR condition. We conclude that a brief immersive oceanic VR experience can influence explicit ocean connectedness, as measured with the INS, but its influence on packaging perceptions was more limited.

Ocean oxygenation and ecological restructuring caused by the late Paleozoic evolution of land plants

The dramatic increase in ocean-atmosphere oxygen levels during the Devonian and Mississippian is increasingly linked to the diversification of land plants, yet the timing and extent of this event remain uncertain. This study uses the redox-sensitive rare earth element cerium (cerium anomaly—Ce/Ce*) to investigate ocean redox conditions during the deposition of globally distributed Paleozoic carbonate strata. Our Paleozoic Ce/Ce* record suggests that Cambrian, Ordovician, and Silurian oceans had relatively low O2 levels (mean Ce/Ce* = 0.86 ± 0.10, 0.91 ± 0.14, and 0.91 ± 0.10 [±1σ], respectively). In contrast, short-lived ocean oxygenation events, possibly related to the diversification of small land plants, likely occurred throughout the Early and Middle Devonian (mean Ce/Ce* = 0.80 ± 0.07 and 0.58 ± 0.14, respectively). “Modern” Ce/Ce* values (<0.36) first occurred during the Late Devonian, suggesting that the main phase of Devonian and Mississippian oceanic oxygenation was related to the evolution of large vascular plants and the first forests. Despite this, the significant variability of Ce/Ce* values during this time suggests that shallow marine settings were susceptible to redox instability, possibly caused by upwelling of anoxic deep waters. This redox instability potentially provides evidence of a mechanism for contemporaneous mass extinction and metazoan reef collapse events. Development of strongly oxic conditions during the Late Devonian may have resulted in the demise of many Paleozoic-type organisms, facilitated the radiation of the modern evolutionary fauna, and established the modern oxygenated ocean-atmosphere system.

Microbiome flexibility enhances the resilience of the potentially invasive coral Tubastraea aurea to abrupt environmental changes: Insights from a shallow water hydrothermal vent transplantation study

To comprehend the effects of potentially invasive coral Tubastraea aurea on marine ecosystems, it is crucial to understand their adaptive strategies to survive environmental changes and perturbations. Therefore, a cross-transplantation study was conducted to assess the microbiome's role in the resilience of T. aurea to sudden environmental changes.Hydrographic analyses revealed distinct ecological conditions at two sites: a hydrothermal vent (HV) site, characterized by harsh environmental conditions serving as a natural laboratory for future oceanic changes, and a regular coastal site Fulong (FU). Both sites showed significant differences in pH, temperature, and dissolved oxygen. Using Oxford Nanopore Technologies, we examined bacterial dynamics in coral tissue, mucus and ambient sediment samples following cross-transplantation experiments. We observed a rapid shift in dominant bacterial groups post-transplantation with transplanted corals acquiring microbiomes similar to native corals from their respective sites within 16 days. The bacteria Endozoicomonas euniceicola and Ruegeria profundi were dominant in both native and transplanted corals, suggesting their critical role in coral resilience. Furthermore, the enrichment of certain bacterial taxa post-transplantation suggests that opportunistic species also contribute to host acclimatization. Functional profiling data indicated that there was site-specific adaptation because corals had acquired beneficial bacterial assemblages to assist them cope with environmental stressors. More specifically, there was a switch towards sulfur and nitrogen metabolism in corals that moved to high sulfidic environments, while corals transplanted into normal coastal environments showed enriched photoautotrophic processes due to their symbionts. Our study underscored the highly flexible microbiome of T. aurea and its pivotal role in facilitating host resilience to environmental perturbations, particularly in the context of its potential invasiveness. Hence, these findings contribute to the understanding of coral-microbiome dynamics and emphasize the necessity of considering microbially-mediated resilience in managing potentially invasive coral species in marine ecosystems around the world, especially as ocean conditions continue to change.

Melt sensitivity of irreversible retreat of Pine Island Glacier

Abstract. In recent decades, glaciers in the Amundsen Sea Embayment in West Antarctica have made the largest contribution to mass loss from the entire Antarctic Ice Sheet. Glacier retreat and acceleration have led to concerns about the stability of the region and the effects of future climate change. Coastal thinning and near-synchronous increases in ice flux across neighbouring glaciers suggest that ocean-driven melting is one of the main drivers of mass imbalance. However, the response of individual glaciers to changes in ocean conditions varies according to their local geometry. One of the largest and fastest-flowing of these glaciers, Pine Island Glacier (PIG), underwent a retreat from a subglacial ridge in the 1940s following a period of unusually warm conditions. Despite subsequent cooler periods, the glacier failed to recover back to the ridge and continued retreating to its present-day position. Here, we use the ice-flow model Úa to investigate the sensitivity of this retreat to changes in basal melting. We show that a short period of increased basal melt was sufficient to force the glacier from its stable position on the ridge and undergo an irreversible retreat to the next topographic high. Once high melting begins upstream of the ridge, only near-zero melt rates can stop the retreat, indicating a possible hysteresis in the system. Our results suggest that unstable and irreversible responses to warm anomalies are possible and can lead to substantial changes in ice flux over relatively short periods of only a few decades.

Sensitivity of marine invertebrates to acidification of seawater by an atmosphere enriched with CO2

Ocean acidification, a consequence of increasing atmospheric CO2, results from oceans absorbing about one-third of CO2 emissions, leading to a decrease in pH. This phenomenon can cause sublethal or lethal damage to marine organisms some of which are crucial for coastal ecosystems and human economies. Understanding how to reproduce acidified seawater in a laboratory is essential for assessing potential impacts. Our protocol uses a CO2-enriched atmosphere to determine the pH tolerance of Mysidopsis juniae, exposed at pH 6.8 and 7.0, and larvae of Arbacia lixula, exposed at pH 7.2. M. juniae showed lethal responses at pH 6.8 ± 0.3, while A. lixula exhibited delayed larval development as a sublethal reaction at pH 7.2 ± 0.3. However, these pH levels are extreme and cannot be predicted for future oceanic conditions. Other studies have indicated negative sublethal effects on similar organisms at higher pH levels than those observed in this study. Continued experiments are necessary to prepare for and inform about the dangers of ocean acidification, and also to develop other types of studies.

Numerical study on heat transfer of two-phase fluid in helical coil pipe under ocean condition

The thermal hydraulic characteristics and heat transfer of two-phase fluid in helical coil once-through steam generator under ocean conditions like rolling and heaving motions are studied numerically. A CFD model is established to analyze the effects of motion parameters like amplitude, period and rolling radius and the heat flux distribution are discussed. The analysis shows that the overall heat transfer decreases under ocean conditions, but the overall deterioration is limited, indicting the helical coil pipe has the stability for ocean conditions. The additional forces like Coriolis, centrifugal and inertial forces introduced by rolling motion are analyzed theoretically and the result shows it detorts the original two main vortexes responsible for high heat transfer due to its spiral geometry, making heat transfer fluctuates up and down periodically near the steady state value. As rolling height increases, the heat transfer is nonlinear due to the competition between Coriolis force and centrifugal and inertial forces. As rolling amplitude increases, the heat transfer variation increases and the local heat transfer deterioration is severely aggravated, indicating high rolling amplitude should be avoided as possible. Increasing rolling period makes heat transfer behavior more approximate to static case as gravity and centrifugal force due to spiral geometry is dominate. Under heaving motion, the overall heat transfer decreases, and increasing heaving amplitude and decreasing period make the fluctuation more severe.

Contrasting the Penultimate Glacial Maximum and the Last Glacial Maximum (140 and 21 ka) using coupled climate–ice sheet modelling

Abstract. The configuration of the Northern Hemisphere ice sheets during the Penultimate Glacial Maximum differed to the Last Glacial Maximum. However, the reasons for this are not yet fully understood. These differences likely contributed to the varied deglaciation pathways experienced following the glacial maxima and may have had consequences for the interglacial sea level rise. To understand the differences between the North American Ice Sheet at the Last and Penultimate glacial maxima (21 and 140 ka), we perform two perturbed-physics ensembles of 62 simulations using a coupled atmosphere–ice sheet model, FAMOUS-ice, with prescribed surface ocean conditions, in which the North American and Greenland ice sheets are dynamically simulated with the Glimmer ice sheet model. We apply an implausibility metric to find ensemble members that match reconstructed ice extent and volumes at the Last and Penultimate glacial maxima. We use a resulting set of “plausible” parameters to perform sensitivity experiments to decompose the role of climate forcings (orbit, greenhouse gases) and initial conditions on the final ice sheet configurations. This confirms that the initial ice sheet conditions used in the model are extremely important in determining the difference in final ice volumes between both periods due to the large effect of the ice–albedo feedback. In contrast to evidence of a smaller Penultimate North American Ice Sheet, our results show that the climate boundary conditions at these glacial maxima, if considered in isolation, imply a larger Penultimate Glacial Maximum North American Ice Sheet than at the Last Glacial Maximum by around 6 m sea level equivalent. This supports the notion that the growth of the ice sheet prior to the glacial maxima is key in explaining the differences in North American ice volume.

Factors influencing harvest success for an Arctic under-ice subsistence fishery

Long-term fisheries datasets are particularly rare in Arctic environments and are essential to understanding the variability in harvest rates. We analyzed 30 years of harvest monitoring data and compared results to fish monitoring data from nearshore waters of Prudhoe Bay, Alaska, to determine the importance of age-0 recruitment and intra-annual factors on subsequent harvests of Arctic cisco in the Colville River delta (CRD), Alaska. While age-0 recruitment to Prudhoe Bay was positively associated with annual harvest success in the CRD, wind and salinity patterns and subsistence fishing location and timing also contributed significantly in explaining adult harvest variability. Harvest rates were highest closest to the river mouth and early in the season. Harvest rates increased with increasing salinity up to 25 ppt, then declined. As the climate changes in the region, we may see shifts in nearshore ocean and river conditions which will impact recruitment and fishing activity. These long-term monitoring efforts will continue to inform sustainable fisheries management in the face of a rapidly changing climate, and with ongoing infrastructure development in the region.

Improved growth performance and physiological state in hybrid abalone (Haliotis rufescens and Haliotis fulgens) facing ocean acidification conditions

Abalone (Haliotis spp.) is a valuable global aquaculture resource in Mexican abalone industry, particularly red (Haliotis rufescens) and green (H. fulgens) abalone, showing significant growth. However, climate change -particularly ocean acidification (OA)- threatens production by negatively impacting mollusks, leading to recruitment failures, poor fertilization, malformations, and reduced calcification and growth jeopardizing sustainability and food security. This study aims to assess robustness of a hybrid abalone cross RF (H. rufescens ♀ x H. fulgens ♂) to OA conditions by evaluating biological performance (survival, growth in weight and length) and metabolic response (oxygen consumption, ammonia excretion rate, and atomic O:N ratio). Juveniles from hybrid RF cross and two pure parental crosses (RR, FF) were exposed to three pH levels: control (pH ≈ 8.0) and two reduced pH scenarios (pH 7.8 and 7.5), representing moderate and severe OA conditions. The results showed hybrid cross exhibiting better growth and metabolic response than pure crosses under all conditions. Notably, hybrid length growth was superior under moderate OA conditions (pH 7.8) compared to control (pH 8.0) and intense OA conditions (pH 7.5). Enhanced physiological hybrid status was evidenced by increased oxygen consumption and stable ammonia excretion, reflected in higher atomic O:N ratio. This study demonstrates hybrid cross RF robustness under OA conditions and supports interspecific hybridization as potential mitigation strategy to alleviate negative OA effects for sustainable abalone production.