-
Irradiance Level Only Moderately Affects Thermal Bleaching in the Stony Coral Stylophora pistillata
-
Combining Cirrus and Aerosol Corrections for Improved Reflectance Retrievals over Turbid Waters from Visible Infrared Imaging Radiometer Suite Data
-
Exploring the Cultivation of Ulva intestinalis in Low-Salinity Environments of the Baltic Sea
Journal Description
Oceans
Oceans
is an international, peer-reviewed, open access journal of oceanography, published quarterly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, ESCI (Web of Science), AGRIS, and other databases.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 38.6 days after submission; acceptance to publication is undertaken in 5.5 days (median values for papers published in this journal in the first half of 2025).
- Journal Rank: CiteScore - Q2 (Oceanography)
- Recognition of Reviewers: APC discount vouchers, optional signed peer review and reviewer names are published annually in the journal.
- Journal Clusters of Water Resources: Water, Journal of Marine Science and Engineering, Hydrology, Resources, Oceans, Limnological Review, Coasts.
Impact Factor:
1.6 (2024);
5-Year Impact Factor:
1.9 (2024)
Latest Articles
A Stability Model for Sea Cliffs Considering the Coupled Effects of Sea Erosion and Rainfall
Oceans 2025, 6(3), 45; https://doi.org/10.3390/oceans6030045 (registering DOI) - 14 Jul 2025
Abstract
►
Show Figures
This study proposed a sea cliff stability model that accounted for the coupled effects of sea erosion and rainfall, offering an improved quantitative assessment of the toppling risk. The approach integrated the notch morphology (height and depth) and rainfall infiltration to quantify stability,
[...] Read more.
This study proposed a sea cliff stability model that accounted for the coupled effects of sea erosion and rainfall, offering an improved quantitative assessment of the toppling risk. The approach integrated the notch morphology (height and depth) and rainfall infiltration to quantify stability, validated by field data from six toppling sites near Da’ao Bay, where the maximum erosion distance error between model predictions and measurements ranged from 0.81% to 48.8% (with <20% error for Sites S2, S3, and S4). The results indicated that the notch morphology and rainfall exerted significant impacts on the sea cliff stability. Site S4 (the highest site) corresponded to a 17.5% decrease in K per 0.1 m notch depth increment. The rainfall infiltration reduced the maximum stable notch depth, decreasing by 8.86–21.92% during prolonged rainfall. This model can predict sea cliff stability and calculate the critical notch depth (e.g., 0.56–1.22 m for the study sites), providing a quantitative framework for coastal engineering applications and disaster mitigation strategies under climate change scenarios.
Full article
Open AccessArticle
Fin Whale Acoustic Presence Increases by 3 d/y in the Migratory Corridor off Cape Leeuwin, Western Australia—An Indicator of Population Growth?
by
Meghan G. Aulich, Robert D. McCauley, Brian S. Miller and Christine Erbe
Oceans 2025, 6(3), 44; https://doi.org/10.3390/oceans6030044 - 11 Jul 2025
Abstract
The population of southern fin whales (Balaenoptera physalus quoyi) was severely depleted by 19th and 20th century whaling. Its conservation status remains ‘vulnerable’, as recovery has been slow. Over 19 years of underwater acoustic recordings from the Comprehensive Nuclear-Test-Ban Treaty Organization
[...] Read more.
The population of southern fin whales (Balaenoptera physalus quoyi) was severely depleted by 19th and 20th century whaling. Its conservation status remains ‘vulnerable’, as recovery has been slow. Over 19 years of underwater acoustic recordings from the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO)’s hydrophones off Cape Leeuwin, Western Australia, were analyzed to monitor fin whales’ annual migration from their Southern Ocean feeding grounds (where they spend the austral summer) to their tropical breeding grounds (where they spend the austral winter) and back. Northward migrants arrived ~2 d/y earlier (2002–2020). The number of hours with fin whale acoustic presence increased by ~49 h/y and the number of days with fin whale acoustic presence by ~3 d/y. Thus, by the end of the 19-year recording period, fin whales were acoustically present on 74 more days than at the beginning of recording. While changes in habitat function, climate, and ambient noise may affect migratory behavior, the most likely explanation is a post-whaling increase in the number of animals of this Southern Hemisphere subspecies.
Full article
(This article belongs to the Special Issue Marine Mammals in a Changing World, 2nd Edition)
►▼
Show Figures

Figure 1
Open AccessCommunication
The Accidental Capture of a Newborn Shortfin Mako Shark Isurus oxyrinchus (Rafinesque, 1810) in the Northwestern Mediterranean Sea off the Coast of Marseille, France
by
Emmanuel Leguay and Eric E. G. Clua
Oceans 2025, 6(3), 43; https://doi.org/10.3390/oceans6030043 - 9 Jul 2025
Abstract
►▼
Show Figures
A small-sized shark was accidentally caught in the coastal waters of southeastern France and abandoned in the port of L’Estaque (Marseille) in May 2024. An autopsy revealed that it was a young female shortfin mako, Isurus oxyrinchus (Rafinesque, 1810). Numerous superficial wounds on
[...] Read more.
A small-sized shark was accidentally caught in the coastal waters of southeastern France and abandoned in the port of L’Estaque (Marseille) in May 2024. An autopsy revealed that it was a young female shortfin mako, Isurus oxyrinchus (Rafinesque, 1810). Numerous superficial wounds on the head, back, and flanks, in the form of parallel striations resulting from heavy friction, indicate meshing in a gillnet that provoked the animal’s death by asphyxiation. Its very small size (64.77 cm TL) suggests that this is a newborn individual, leading to the hypothesis that the waters off Marseille could be a nursery area for this species. This observation alone is not enough to prove this point, but it does suggest the need for closer monitoring to validate it. Should the area be proven to play this key role for this critically endangered species, measures to limit fishing pressure would be essential, particularly during the parturition period between February and May.
Full article

Figure 1
Open AccessArticle
Acropora spp. Coral Gardening Using Fragmentation and Direct Transplantation: A Feasibility Study at Boundary Island
by
Min Li, Dechuan Lee, Xiaofei Xiong, Le Zhu, Aimin Wang, Wubo Wan, Yaoxian Chin and Peizheng Wang
Oceans 2025, 6(3), 42; https://doi.org/10.3390/oceans6030042 - 8 Jul 2025
Abstract
As major bleaching continues to ravage reefs worldwide, there is an urgent need for active coral restoration. However, the high cost of such a project is inhibitive for many countries. Here, we introduce a cost-effective design for Acropora robusta and Acroporavalenciennesi coral
[...] Read more.
As major bleaching continues to ravage reefs worldwide, there is an urgent need for active coral restoration. However, the high cost of such a project is inhibitive for many countries. Here, we introduce a cost-effective design for Acropora robusta and Acroporavalenciennesi coral gardening through fragmentation and direct transplantation. Implemented off Boundary Island, Hainan Province, China, the project demonstrated high coral survival rates (>94%) at a reduced cost of USD 2.50 per coral after 246 days, besides exhibiting an efficient outplanting rate at 30 coral h−1 person−1. Growth monitoring suggested that the transplanted Acropora spp. follow an exponential growth model over time. Initial fragment size did not seem to affect the growth rate of outplanted Acropora spp., although a weak negative correlation was found at day 246 for A. robusta. Finally, the design used in this study employs detachable steel grid nurseries and is plastics-free, ensuring sustainability and adaptability to different reef conditions, and thus providing a promising strategy for affordable coral reef restoration.
Full article
(This article belongs to the Topic Conservation and Management of Marine Ecosystems)
►▼
Show Figures

Figure 1
Open AccessArticle
Factor Correction Analysis of Nodal Tides in Taiwan Waters
by
Hsien-Kuo Chang, Peter Tian-Yuan Shih and Wei-Wei Chen
Oceans 2025, 6(3), 41; https://doi.org/10.3390/oceans6030041 - 7 Jul 2025
Abstract
►▼
Show Figures
Nodal tides, which follow an 18.6-year cycle, influence tidal variations at any given location in the ocean. Conventional nodal tide theory neglects land effects and topological change. Due to the complex seabed topography around Taiwan waters, the purpose of this paper is to
[...] Read more.
Nodal tides, which follow an 18.6-year cycle, influence tidal variations at any given location in the ocean. Conventional nodal tide theory neglects land effects and topological change. Due to the complex seabed topography around Taiwan waters, the purpose of this paper is to use the long-term tidal data of six stations to discuss the effects of perigean and nodal tides on 20 constituents and to compare the results with previous theories. A modulation method is employed to fit the annual amplitude estimated by harmonic analysis (HA). The top four constituents of the fitted and theoretical values of nodal amplitude factor (AF) and phase factor (PF) are O1, K1, K2, and Q1. We find that perigean tides or second-order nodal tides considered in the fitting contribute to almost identical performance. The linear time change considered in the AF fitting has better fitting than the mean water level involved.
Full article

Figure 1
Open AccessEditorial
Feature Papers of Oceans 2024
by
Alexander J. Werth
Oceans 2025, 6(3), 40; https://doi.org/10.3390/oceans6030040 - 2 Jul 2025
Abstract
As the noted futurist and author Arthur C [...]
Full article
(This article belongs to the Special Issue Feature Papers of Oceans 2024)
Open AccessArticle
A Multi-Stage Enhancement Based on the Attenuation Characteristics of X-Band Marine Radar Images for Oil Spill Extraction
by
Peng Liu, Xingquan Zhao, Xuchong Wang, Pengzhe Shao, Peng Chen, Xueyuan Zhu, Jin Xu, Ying Li and Bingxin Liu
Oceans 2025, 6(3), 39; https://doi.org/10.3390/oceans6030039 - 1 Jul 2025
Abstract
►▼
Show Figures
Marine oil spills cause significant environmental damage worldwide. Marine radar imagery is used for oil spill detection. However, the rapid attenuation of backscatter intensity with increasing distance limits detectable coverage. A multi-stage image enhancement framework integrating background clutter fitting subtraction, Multi-Scale Retinex, and
[...] Read more.
Marine oil spills cause significant environmental damage worldwide. Marine radar imagery is used for oil spill detection. However, the rapid attenuation of backscatter intensity with increasing distance limits detectable coverage. A multi-stage image enhancement framework integrating background clutter fitting subtraction, Multi-Scale Retinex, and Gamma correction is proposed. Experimental results using marine radar images sampled in the oil spill incident in Dalian 2010 are used to demonstrate the significant improvements. Compared to Contrast-Limited Adaptive Histogram Equalization and Partially Overlapped Sub-block Histogram Equalization, the proposed method enhances image contrast by 24.01% and improves the measurement of enhancement by entropy by 17.11%. Quantitative analysis demonstrates 95% oil spill detection accuracy through visual interpretation, while significantly expanding detectable coverage for oil extraction.
Full article

Figure 1
Open AccessArticle
Status Quo and Future Prospects of China’s Weather Routing Services for Ocean-Going Business Vessels
by
Hao Zhang, Guanjun Niu, Tao Liu, Chuanhai Qian, Wei Zhao, Xiaojun Mei and Hao Wu
Oceans 2025, 6(3), 38; https://doi.org/10.3390/oceans6030038 - 23 Jun 2025
Abstract
►▼
Show Figures
The global shipping industry is evolving towards deep integration of digital transformation, intelligent upgrading, and green development. Meanwhile, recent geopolitical shifts have introduced heightened uncertainties into international shipping, compounding the challenges and escalating the demands for weather routing services for ocean-going ships. This
[...] Read more.
The global shipping industry is evolving towards deep integration of digital transformation, intelligent upgrading, and green development. Meanwhile, recent geopolitical shifts have introduced heightened uncertainties into international shipping, compounding the challenges and escalating the demands for weather routing services for ocean-going ships. This paper provides a systematic review and expert perspective on China’s current status and key challenges in ocean-going weather routing services. Based on operational insights from China’s national meteorological service synthesized with a review of current trends and the literature, it further explores the future development of China’s ocean-going weather routing services and technologies from multiple dimensions: enhancing maritime weather observation capabilities, developing advanced weather routing service models, upgrading autonomous and controllable global satellite communication systems, promoting intelligent navigation technologies to facilitate shipping’s low-carbon transition, and expanding meteorological support capabilities for Arctic shipping routes. The analysis identifies critical gaps and proposes strategic directions, offering a unique contribution to understanding the trajectory of weather routing services within China’s specific national context from the perspective of its primary national service provider.
Full article

Figure 1
Open AccessArticle
A Kiss from the Wild: Tongue Nibbling in Free-Ranging Killer Whales (Orcinus orca)
by
Javier Almunia, Johnny van Vliet and Debbie Bouma
Oceans 2025, 6(2), 37; https://doi.org/10.3390/oceans6020037 - 11 Jun 2025
Abstract
Tongue-nibbling is a rare and previously undocumented affiliative behaviour in free-ranging killer whales (Orcinus orca), until now seen only in individuals under human care. This study presents the first recorded observation of tongue-nibbling between two wild killer whales in the Kvænangen
[...] Read more.
Tongue-nibbling is a rare and previously undocumented affiliative behaviour in free-ranging killer whales (Orcinus orca), until now seen only in individuals under human care. This study presents the first recorded observation of tongue-nibbling between two wild killer whales in the Kvænangen fjords, Norway. The interaction, captured opportunistically by citizen scientists during a snorkelling expedition, lasted nearly two minutes and involved repeated episodes of gentle, face-to-face oral contact. This behaviour closely resembles sequences observed and described in detail in zoological settings, suggesting that it forms part of the species’ natural social repertoire. The observation also supports the interpretation of tongue-nibbling as a socially affiliative behaviour, likely involved in reinforcing social bonds, particularly among juveniles. The prolonged maintenance of this interaction in managed populations originating from geographically distinct Atlantic and Pacific lineages further indicates its behavioural conservation across contexts. This finding underscores the importance of underwater ethological observation in capturing cryptic social behaviours in cetaceans and illustrates the value of integrating citizen science into systematic behavioural documentation. The study also reinforces the relevance of managed populations in ethological research and highlights the ethical need for carefully regulated wildlife interaction protocols in marine tourism.
Full article
(This article belongs to the Special Issue Marine Mammals in a Changing World, 2nd Edition)
►▼
Show Figures

Figure 1
Open AccessArticle
Underwater Reverberation Suppression Using Wavelet Transform and Complementary Learning
by
Jiajie Liu, Qunfei Zhang, Xiaodong Cui, Chencong Tang and Zijun Pu
Oceans 2025, 6(2), 36; https://doi.org/10.3390/oceans6020036 - 9 Jun 2025
Abstract
►▼
Show Figures
Reverberation is the primary interference of active detection. Therefore, the effective suppression of reverberation is a prerequisite for reliable signal processing. Existing dereverberation methods have shown effectiveness in specific scenarios. However, they often struggle to exploit the distinction between target echo and reverberation,
[...] Read more.
Reverberation is the primary interference of active detection. Therefore, the effective suppression of reverberation is a prerequisite for reliable signal processing. Existing dereverberation methods have shown effectiveness in specific scenarios. However, they often struggle to exploit the distinction between target echo and reverberation, especially in complex, dynamically changing underwater environments. This paper proposes a novel dereverberation network, ERCL-AttentionNet (Echo–Reverberation Complementary Learning Attention Network). We use the Continuous Wavelet Transform (CWT) to extract time–frequency features from the received signal, effectively balancing the time and frequency resolution. The real and imaginary parts of the time–frequency matrix are combined to generate attention representations, which are processed by the network. The network architecture consists of two complementary UNet models sharing the same encoder. These models independently learn target echo and reverberation features to reconstruct the target echo. An attention mechanism further enhances performance by focusing on target information and suppressing irrelevant disturbances in complex environments. Experimental results demonstrate that our method achieves a higher Peak-to-Average Signal-to-Reverberation Ratio (PSRR), Structural Similarity Index (SSIM), and Peak-to-Average Ratio (PAR) of cross-correlation while effectively preserving key time–frequency features, compared to traditional methods such as autoregressive (AR) and singular value decomposition (SVD).
Full article

Figure 1
Open AccessArticle
Genomic Characteristics of Two Common Pest Starfish in Northern China Seas: A Whole-Genome Survey Approach
by
Zhichao Huang, Zhe Li and Gang Ni
Oceans 2025, 6(2), 35; https://doi.org/10.3390/oceans6020035 - 6 Jun 2025
Abstract
►▼
Show Figures
Coastal shellfish farming areas in northern China seas face frequent starfish outbreaks, particularly from Asterias amurensis and Patiria pectinifera, leading to significant economic losses. Genomic data are key to understanding the population dynamics and adaptive traits and developing effective control measures for
[...] Read more.
Coastal shellfish farming areas in northern China seas face frequent starfish outbreaks, particularly from Asterias amurensis and Patiria pectinifera, leading to significant economic losses. Genomic data are key to understanding the population dynamics and adaptive traits and developing effective control measures for these species. Here, we characterized and compared the genomic information of these two starfish using a whole-genome survey approach. The genome size of A. amurensis is ~477 Mb with 1.52% heterozygosity, 53.60% repetitive sequences, and 39.94% GC content, while P. pectinifera has a ~529 Mb genome, 2.90% heterozygosity, 56.02% repetitive sequences, and 40.63% GC content. Scaffold N50 values were 1823 bp for A. amurensis and 1328 bp for P. pectinifera. We identified 161,786 microsatellite motifs in A. amurensis and 316,245 in P. pectinifera, with mononucleotide repeats being the most common. A total of 171 single-copy homologous genes were found in A. amurensis, with 94 in P. pectinifera. For both species, KEGG annotation showed functional similarities in glycan biosynthesis, translation, metabolism, catabolism, and transport. The Pairwise Sequentially Markovian Coalescent (PSMC) analysis unveiled a bottleneck effect during the Pleistocene glaciation. Additionally, phylogenetic analysis of mitochondrial genomes indicates that P. pectinifera and Patiria miniata of the same genus belong to the same branch in the evolutionary tree as sister groups with the closest genetic relationship, while A. amurensis is most closely related to Astropecten polyacanthus within the class Asteroidea. These findings provide valuable genomic insights for both species.
Full article

Figure 1
Open AccessArticle
Elasmobranch Species Composition in Otter Trawl Fisheries (Eastern Aegean Sea)
by
İlker Aydin, Alexandros Theocharis, Sercan Yapici and Dimitris Klaoudatos
Oceans 2025, 6(2), 34; https://doi.org/10.3390/oceans6020034 - 6 Jun 2025
Abstract
►▼
Show Figures
The Eastern Aegean Sea hosts a diverse assemblage of elasmobranchs, many of which are vulnerable or endangered. This study presents a fishery-independent assessment of species composition, catch characteristics, and spatial patterns in bottom trawl fisheries between Lesvos Island and Ayvalik. A total of
[...] Read more.
The Eastern Aegean Sea hosts a diverse assemblage of elasmobranchs, many of which are vulnerable or endangered. This study presents a fishery-independent assessment of species composition, catch characteristics, and spatial patterns in bottom trawl fisheries between Lesvos Island and Ayvalik. A total of 48 surveys were conducted between September 2022 and October 2024, identifying nine elasmobranch species, with Scyliorhinus canicula (small-spotted catshark) and Mustelus mustelus (common smooth-hound) dominating the catch. Biological parameters, sex ratios, and condition upon capture and release were recorded, while catch per unit effort (CPUE) and diversity indices were used to evaluate temporal patterns. The survival probability was negatively affected by the trawl duration and elevated temperatures, emphasizing the need for mitigation measures. Spatial models revealed high-density zones that likely function as foraging or nursery grounds. Seasonal shifts in community composition were also evident. Many non-commercial species were discarded irrespective of their size or condition. These findings underscore the ecological importance of this understudied region and support the need for spatially explicit, species-specific management strategies, including gear selectivity improvements, seasonal closures, and Electronic Monitoring. The study offers a critical baseline for enhancing the sustainability of elasmobranch populations in the Eastern Mediterranean.
Full article

Figure 1
Open AccessArticle
Morphological Insights into Echinometra lucunter Spines Reveal Cellular Sources of Bioactive Molecules
by
Juliana Mozer Sciani, Marta Maria Antoniazzi, Carlos Jared, José Roberto Machado Cunha da Silva and Daniel Carvalho Pimenta
Oceans 2025, 6(2), 33; https://doi.org/10.3390/oceans6020033 - 5 Jun 2025
Abstract
►▼
Show Figures
Echinometra lucunter, the most abundant sea urchin in Brazil, causes numerous accidents by puncture wounds, primarily on hands and feet. Beyond mechanical trauma, recent research has identified bioactive molecules in spine extracts and coelomic fluid contributing to these inflammatory reactions. This study
[...] Read more.
Echinometra lucunter, the most abundant sea urchin in Brazil, causes numerous accidents by puncture wounds, primarily on hands and feet. Beyond mechanical trauma, recent research has identified bioactive molecules in spine extracts and coelomic fluid contributing to these inflammatory reactions. This study investigated spine morphology to better understand the envenomation and defense processes for the animal. Using various microscopy techniques, the spines were revealed to be mineral structures with longitudinal canals and a sponge-like central mesh rich in granular cells. These cells extend from the spine’s center to its edges, terminating in fimbriae-like structures, likely involved in molecular exchange with the environment. The spine tip is more cellular than the base, suggesting a defensive role, while the base provides structural support. Several cell types were identified, including granulocytes, red spherulocytes, and phagocytic amoebocytes, also found in the coelomic fluid. Other cells displayed prominent Golgi apparatuses and secretory granules, indicating specialized secretory functions, likely the source of bioactive molecules involved in chemical defense and spine regeneration. Understanding this cellular structure is crucial for comprehending the urchin’s envenomation and defense mechanisms.
Full article

Figure 1
Open AccessFeature PaperArticle
Irradiance Level Only Moderately Affects Thermal Bleaching in the Stony Coral Stylophora pistillata
by
Ronald Osinga, Emma van Veenendaal, Daniëlle S. L. Geschiere, Britt J. A. van Herpen and Saskia Oosterbroek
Oceans 2025, 6(2), 32; https://doi.org/10.3390/oceans6020032 - 4 Jun 2025
Abstract
►▼
Show Figures
Light is considered an important co-factor in causing thermal bleaching in photosymbiotic corals. To quantify the effects of light strength on thermal bleaching, colonies of the stony coral Stylophora pistillata were experimentally subjected to a gradual increase in temperature (1 °C per 4
[...] Read more.
Light is considered an important co-factor in causing thermal bleaching in photosymbiotic corals. To quantify the effects of light strength on thermal bleaching, colonies of the stony coral Stylophora pistillata were experimentally subjected to a gradual increase in temperature (1 °C per 4 days) under two irradiance levels: 100 and 500 µmole quanta m−2 s−1. Corals kept under the same irradiance levels at a constant temperature of 26 °C were used as controls. The apparent photochemical yield ΔF/Fm′ of Photosystem II of the coral symbionts was monitored daily as an indicator for the onset of thermal bleaching, the onset of bleaching being defined as a steep decrease in ΔF/Fm′. In heat-treated corals incubated under the high irradiance of 500 µmole quanta m−2 s−1, the onset of bleaching occurred 26 days after the start of the heat ramp, at a temperature of 33 °C. ΔF/Fm′ in corals incubated under the low irradiance of 100 µmole quanta m−2 s−1 started to drop 1 day later at the same temperature. Before and after the observed drop in ΔF/Fm′, coral samples were taken for analysis of symbiont densities and levels of chlorophyll-a. At the onset of bleaching, symbiont densities and chlorophyll-a levels in heat-treated corals were not different from those of corals kept under control conditions. Three days after the onset of bleaching, symbiont densities and levels of chlorophyll-a in heat-treated corals had substantially decreased in comparison to controls. Under low irradiance, symbiont density and chlorophyll-a content were 84% and 76% lower than controls, respectively, whereas under high irradiance, symbiont density and chlorophyll-a content were 41% and 46% lower. These data suggest that damage to the photosystem in coral symbionts is the root cause of thermal bleaching in symbiotic corals, followed later by a collapse of the symbiosis. The role of light in augmenting thermal bleaching was only moderate, with a five-fold reduction in irradiance causing only a 1-day delay in bleaching. These results suggest that temperature is the main driver of bleaching in the studied coral.
Full article

Figure 1
Open AccessArticle
Evaluation of Anchovy Egg Density: A Study on Differences Between Vertical and Oblique Towing Samplers for Ichthyoplankton
by
Gualtiero Basilone, Rosalia Ferreri, Angelo Bonanno, Simona Genovese and Salvatore Aronica
Oceans 2025, 6(2), 31; https://doi.org/10.3390/oceans6020031 - 29 May 2025
Abstract
►▼
Show Figures
The use of multiple sampling instruments during ichthyoplankton surveys could require a significant amount of time for sample collection procedures; moreover, their use is highly dependent on weather conditions. During surveys aimed at the application of the Daily Egg Production Method (DEPM), two
[...] Read more.
The use of multiple sampling instruments during ichthyoplankton surveys could require a significant amount of time for sample collection procedures; moreover, their use is highly dependent on weather conditions. During surveys aimed at the application of the Daily Egg Production Method (DEPM), two different kinds of sampler are employed: PairoVET and Bongo 40. The possibility of using only one of these samplers may allow for a reduction in the sampling time on board and the subsequent analyses; thus, a study was carried out to test the use of the Bongo 40 sampler alone (i.e., without PairoVET sampling) in DEPM application. Samples collected during five ichthyoplankton surveys (from 2007 to 2010 and in 2014) were analyzed to compare the efficiency in anchovy egg collection. Although the compared ichthyoplankton samplers provided differences in the collected number of eggs, as well as in the filtered volume, non-significant differences between them were recorded in the egg density. An ANCOVA revealed a significant relationship (F1,5 = 606.80; p < 0.001) between the density estimates from the two nets, but no differences were recorded among years (F1,5 = 0.99; p < 1). The slopes of the linear regressions for the two datasets were close to 1, suggesting a substantial equivalence of the two samplers in estimating the egg density. Finally, since only a few sampling stations showed densities higher than 20 ind. m−2, conversion equations were provided to estimate the PairoVET density from the Bongo 40 data at different density levels (i.e., 20 ind. m−2 or higher).
Full article

Figure 1
Open AccessArticle
Exploring the Cultivation of Ulva intestinalis in Low-Salinity Environments of the Baltic Sea
by
Indrek Adler, Georg Martin, Nikolai Kovalchuk, Helen Orav-Kotta, Kristel Vene, Rando Tuvikene and Jonne Kotta
Oceans 2025, 6(2), 30; https://doi.org/10.3390/oceans6020030 - 22 May 2025
Abstract
►▼
Show Figures
Ulva intestinalis holds promise for sustainable aquaculture in the Baltic Sea, but success has so far been limited by high environmental variability. This study examines how environmental factors influence sporogenesis, attachment, and growth of U. intestinalis in the low-salinity Baltic Sea. Optimal sporogenesis
[...] Read more.
Ulva intestinalis holds promise for sustainable aquaculture in the Baltic Sea, but success has so far been limited by high environmental variability. This study examines how environmental factors influence sporogenesis, attachment, and growth of U. intestinalis in the low-salinity Baltic Sea. Optimal sporogenesis was observed at nutrient levels of 4–7 g/L, with peak zoospore release at 22–24 °C. Artificial substrates showed limited attachment success, as competing algae like Pylaiella littoralis and Cladophora glomerata often outperformed Ulva. Mesh cage cultivation demonstrated potential, achieving growth rates similar to controlled systems, though storm-induced turbidity lowered growth. These findings highlight the importance of tailored Baltic Sea cultivation strategies, focusing on nutrient, temperature, water stability, and competition management to enhance Ulva production. As the first pilot experiments in the region, they provide essential input for developing informed strategies that support more detailed trials and future scaled-up production.
Full article

Figure 1
Open AccessArticle
Future Changes in Carbon Chemistry Under the Implementation of Artificial Ocean Alkalinization Based on CMIP6 Simulations
by
Baoxiao Qu, Jinming Song, Xuegang Li, Huamao Yuan and Liqin Duan
Oceans 2025, 6(2), 29; https://doi.org/10.3390/oceans6020029 - 20 May 2025
Abstract
►▼
Show Figures
Artificial ocean alkalinization (AOA) is one of the most promising marine carbon dioxide removal technologies, but its influence on marine carbon chemistry remains unclear. We applied data from the Sixth Coupled Model Intercomparison Project (CMIP6) to characterize the temporal and spatial variabilities of
[...] Read more.
Artificial ocean alkalinization (AOA) is one of the most promising marine carbon dioxide removal technologies, but its influence on marine carbon chemistry remains unclear. We applied data from the Sixth Coupled Model Intercomparison Project (CMIP6) to characterize the temporal and spatial variabilities of future marine carbon chemistry under the implementation of AOA. Our study shows that the marine carbon system varied significantly under the implementation of AOA, but some specific effects may be masked by the forcing of the high carbon emission scenario SSP5-8.5. Based on the CMIP6 protocol, which added 0.14 Pmol of alkalinity into the ocean annually, AOA promoted an increase in DIC, delayed the rise in pCO2, and mitigated declines in pH and Ω, respectively. The temperate oceans in both hemispheres were the most significantly impacted basins, whereas the Southern Ocean was the least affected. During this century, the oceanic carbon sink is expected to intensify rapidly until around the year 2080, and then gradually weaken. The implementation of AOA merely changed the relative strength of the oceanic sink, rather than its overall variation pattern. Furthermore, in the deep ocean, the effect of AOA was present but quite limited in mitigating ocean acidification.
Full article

Figure 1
Open AccessArticle
Combining Cirrus and Aerosol Corrections for Improved Reflectance Retrievals over Turbid Waters from Visible Infrared Imaging Radiometer Suite Data
by
Bo-Cai Gao, Rong-Rong Li, Marcos J. Montes and Sean C. McCarthy
Oceans 2025, 6(2), 28; https://doi.org/10.3390/oceans6020028 - 14 May 2025
Abstract
The multi-band atmospheric correction algorithms, now referred to as remote sensing reflectance (Rrs) algorithms, have been implemented on a NASA computing facility for global remote sensing of ocean color and atmospheric aerosol parameters from data acquired with several satellite instruments, including
[...] Read more.
The multi-band atmospheric correction algorithms, now referred to as remote sensing reflectance (Rrs) algorithms, have been implemented on a NASA computing facility for global remote sensing of ocean color and atmospheric aerosol parameters from data acquired with several satellite instruments, including the Visible Infrared Imaging Radiometer Suite (VIIRS) on board the Suomi spacecraft platform. These algorithms are based on the 2-band version of the SeaWiFS (Sea-Viewing Wide Field-of-View Sensor) algorithm. The bands centered near 0.75 and 0.865 μm are used for atmospheric corrections. In order to obtain high-quality Rrs values over Case 1 waters (deep clear ocean waters), strict masking criteria are implemented inside these algorithms to mask out thin clouds and very turbid water pixels. As a result, Rrs values are often not retrieved over bright Case 2 waters. Through our analysis of VIIRS data, we have found that spatial features of bright Case 2 waters are observed in VIIRS visible band images contaminated by thin cirrus clouds. In this article, we describe methods of combining cirrus and aerosol corrections to improve spatial coverage in Rrs retrievals over Case 2 waters. One method is to remove cirrus cloud effects using our previously developed operational VIIRS cirrus reflectance algorithm and then to perform atmospheric corrections with our updated version of the spectrum-matching algorithm, which uses shortwave IR (SWIR) bands above 1 μm for retrieving atmospheric aerosol parameters and extrapolates the aerosol parameters to the visible region to retrieve water-leaving reflectances of VIIRS visible bands. Another method is to remove the cirrus effect first and then make empirical atmospheric and sun glint corrections for water-leaving reflectance retrievals. The two methods produce comparable retrieved results, but the second method is about 20 times faster than the spectrum-matching method. We compare our retrieved results with those obtained from the NASA VIIRS Rrs algorithm. We will show that the assumption of zero water-leaving reflectance for the VIIRS band centered at 0.75 μm (M6) over Case 2 waters with the NASA Rrs algorithm can sometimes result in slight underestimates of water-leaving reflectances of visible bands over Case 2 waters, where the M6 band water-leaving reflectances are actually not equal to zero. We will also show conclusively that the assumption of thin cirrus clouds as ‘white’ aerosols during atmospheric correction processes results in overestimates of aerosol optical thicknesses and underestimates of aerosol Ångström coefficients.
Full article
(This article belongs to the Special Issue Ocean Observing Systems: Latest Developments and Challenges)
►▼
Show Figures

Figure 1
Open AccessArticle
Eight Categories of Air–Water Gas Transfer
by
David Kevin Woolf
Oceans 2025, 6(2), 27; https://doi.org/10.3390/oceans6020027 - 8 May 2025
Abstract
The air–sea transfer of gases is important within climate physics, biogeochemistry and the control of pollutants. A two-layer model of transfer directly across the sea surface underpins most discourse, but an expanding literature also features transfer mediated by “suspended fragments”, either bubbles in
[...] Read more.
The air–sea transfer of gases is important within climate physics, biogeochemistry and the control of pollutants. A two-layer model of transfer directly across the sea surface underpins most discourse, but an expanding literature also features transfer mediated by “suspended fragments”, either bubbles in the upper ocean or drops and aerosol in the lower atmosphere. In this study, we describe a categorization of process that elucidates departures from two-layer theory and is a starting point for quantification. On counting the distinct phenomena and their application to gases of various solubility, a total of eight categories are identified. Each category has a distinct scaling with respect to the properties of the gas and this is key to the relative importance of different categories and processes. Transfer through sea spray can be an exchange process, but the evaporation of sea spray is more effective and is an ejection process. The reactivity of carbon dioxide in aqueous solution enhances the effect of spray. Exceptional levels of sea spray generation and evaporation are required to be significant for most gases, but moderate levels are sufficient for carbon dioxide and the most soluble pollutants.
Full article
Open AccessArticle
Seasonal Macrofaunal Diversity in the Shells of Dead Pinna nobilis Linnaeus, 1758 in Southern Istria
by
Petra Burić, Neven Iveša, Adrian Brajković, Ante Žunec, Iris Matulja, Ines Kovačić, Andrej Jaklin, Gioconda Millotti, Paolo Paliaga, Emina Pustijanac, Tin Matulja and Moira Buršić
Oceans 2025, 6(2), 26; https://doi.org/10.3390/oceans6020026 - 7 May 2025
Abstract
►▼
Show Figures
The shells of dead Pinna nobilis individuals are important habitats in sedimentary coastal ecosystems, yet their ecological role is poorly understood. This study investigated macrofaunal communities associated with 80 P. nobilis shells from Soline Bay and Valovine Bay, northern Adriatic, analyzing variations in
[...] Read more.
The shells of dead Pinna nobilis individuals are important habitats in sedimentary coastal ecosystems, yet their ecological role is poorly understood. This study investigated macrofaunal communities associated with 80 P. nobilis shells from Soline Bay and Valovine Bay, northern Adriatic, analyzing variations in species abundance and biodiversity between shell orientations (vertical and horizontal) and across seasons. Shell dimensions were recorded, with larger shells and higher faunal abundance observed in Soline Bay compared to Valovine Bay. A total of 2225 individuals representing 183 species across 19 taxonomic groups were identified, with Malacostraca, Bivalvia, and Polychaeta being the most abundant. Vertically positioned shells hosted significantly more organisms than horizontally positioned ones, likely due to greater available surface area for settlement. Seasonal changes influenced organism abundance, with peaks in winter for Valovine Bay and spring for Soline Bay, correlating with environmental factors such as eutrophication. The most frequent species associated with the shells of dead individuals were the polychaete Sabella spallanzanii and the bivalve Rocellaria dubia, which can impact shell degradation. Despite their temporary nature, the shells of dead P. nobilis provide vital refuge and enhance biodiversity. The findings underscore the ecological importance of P. nobilis shells as biodiversity hotspots and highlight the need for their conservation and further study.
Full article

Figure 1
Highly Accessed Articles
Latest Books
E-Mail Alert
News
Topics
Topic in
JMSE, Oceans, Remote Sensing, Sustainability, Water
Conservation and Management of Marine Ecosystems
Topic Editors: Monia Renzi, Cristiana Guerranti, Manuela PiccardoDeadline: 30 September 2025
Topic in
Energies, JMSE, Oceans, Sustainability, Water
Control and Optimisation for Offshore Renewable Energy
Topic Editors: Olimpo Anaya-Lara, Stephanie Ordonez-Sanchez, Adam StockDeadline: 31 October 2025
Topic in
Applied Sciences, JMSE, Oceans, Water
Coastal Engineering: Past, Present and Future
Topic Editors: M. Dolores Esteban, José-Santos López-Gutiérrez, Vicente Negro, Maria Graça NevesDeadline: 30 April 2026

Conferences
Special Issues
Special Issue in
Oceans
Ocean Observing Systems: Latest Developments and Challenges
Guest Editors: A. Miguel P. Santos, Hassan MoustahfidDeadline: 31 July 2025
Special Issue in
Oceans
Oceans in a Changing Climate
Guest Editors: Mariana Bernardino, Diogo MendesDeadline: 31 December 2025
Special Issue in
Oceans
Marine Mammals in a Changing World, 3rd Edition
Guest Editors: Alexander Werth, Matthew S. SavocaDeadline: 28 February 2026