Sea Ecosystem Research Articles

Trophic interactions between common minke whales (Balaenoptera acutorostrata) and their prey during summer in the northern Barents Sea

Global warming is causing rapid change in marine food webs, particularly at northern latitudes where temperatures are increasing most rapidly. In this study, the diet of common minke whales Balaenoptera acutorostrata was assessed both in terms of short-term (morphological analyses of digestive tract contents) and longer-term (tissue chemical markers: fatty acids and stable isotopes) prey use in the northern Barents Sea to see if they are prey shifting. Samples (blubber cores, muscle, and stomach contents) were obtained from 158 common minke whales taken during Norwegian commercial whaling operations during summer over the period 2016–2020. Two prey items, capelin Mallotus villosus and krill (primarily Thysanoessa sp.), dominated the stomach contents in the entire period of investigation, which included sampling both in June and in August, similar to findings from earlier studies. A few gadoids were also observed in the whale stomachs. Lower blubber fatty acid (FA) contents in 2016/2017 as compared with 2018/2019 were observed. This is most likely explained by differences in sampling time (June in 2016/2017 vs August in 2018/2019, i.e., after a longer feeding period during the summer in the latter case). This explanation also fits with the fact that FA profiles of the 2018/2019 whales were more similar to the FA profiles of the potential prey, presumably reflecting the two months longer assimilation time for these whales. Multidimensional mixing models based on carbon and nitrogen isotope composition of the most likely prey groups suggested that the whales ate mostly krill in four of the five sampling years. In 2018 there were indications of a higher proportion of gadoid fish, showing some dietary flexibility. The trophic level of the whales’ feeding, as interpreted from the nitrogen isotope values, was positively correlated with blubber thickness suggesting that fish-eaters tended to assimilate more energy than whales that focused more exclusively on lower trophic prey. The variation suggested by different dietary analyses methods − stomach contents, fatty acids, and stable isotopes – most likely reflects different turnover times, with muscle stable isotopes likely representing several months of dietary integration, while lipid stores are more dynamic and may represent weeks, and stomach contents represent feeding events during the last few hours. The change in diet of minke whales from small pelagic fishes (in the past) to a greater quantity of krill and demersal fish (seen in this study) suggests that the whales are responding to the ongoing borealization of the Barents Sea ecosystem.

Strategy for Implementing the Tiatiki Concept in Conservation Resource

Strategy is a plan that is intended to achieve the desired goal, or in other words, Strategy is a long-term plan that is prepared to lead to the achievement of certain goals and targets, while the Coastal area is a transition area between land and sea ecosystems which is influenced by changes on land and sea. Research on strategies for implementing the Tiatiki concept in coastal resource conservation in Tabla Supa Depapre village, Jayapura Regency was carried out in August-October 2023 using survey and interview methods. Next, data analysis can be carried out using SWOT analysis. The results of data analysis show that there are 5 strategies for conserving coastal resources in Tabla Supa Village, Depapre District, Jayapura Regency: Developing tourism by involving the community and local wisdom, Increasing community capacity in managing coastal and marine resources in a sustainable manner based on local wisdom, Utilizing local wisdom through the Tabla Supa village community institution in minimizing the negative impacts of using coastal resources that are not environmentally friendly, managing coastal area resources with an integrated system based on community-based management and involving the community and increasing community understanding, especially the younger generation, about the values of local wisdom including Tiatiki by Village community organizations.

Review of marine alien isopods in Türkiye with two new records: of Paracerceis sculpta and Paranthura japonica

This study focuses on the alien isopod species recorded in the Turkish seas. To date, two alien species (Paradella dianae, Sphaeroma walkeri) have been reported in the country, accounting for almost 2.4% of the total number of isopod species occurring in the Turkish seas. The faunistic analysis of benthic samples collected from Dardanelles (Çanakkale) Straits and Izmir Bay revealed two new alien isopod species (Paranthura japonica and Paracerceis sculpta), on the Turkish coasts. Additionally, this is the first record of P. japonica in the Black Sea ecosystem. This study analyses and discusses the morphological, ecological and distributional characteristics of the species.

Testing the deep‐sea glacial disturbance hypothesis as a cause of low, present‐day Norwegian Sea diversity and resulting steep latitudinal diversity gradient, using fossil records

AbstractAimWithin the intensively‐studied, well‐documented latitudinal diversity gradient, the deep‐sea biodiversity of the present‐day Norwegian Sea stands out with its notably low diversity, constituting a steep latitudinal diversity gradient in the North Atlantic. The reason behind this has long been a topic of debate and speculation. Most prominently, it is explained by the deep‐sea glacial disturbance hypothesis, which states that harsh environmental glacial conditions negatively impacted Norwegian Sea diversities, which have not yet fully recovered. Our aim is to empirically test this hypothesis. Specific research questions are: (1) Has deep‐sea biodiversity been lower during glacials than during interglacials? (2) Was there any faunal shift at the Mid‐Brunhes Event (MBE) when the mode of glacial–interglacial climatic change was altered?LocationNorwegian Sea, deep sea (1819–2800 m), coring sites MD992277, PS1243, and M23352.Time period620.7–1.4 ka (Middle Pleistocene–Late Holocene).Taxa studiedOstracoda (Crustacea).MethodsWe empirically test the deep‐sea glacial disturbance hypothesis by investigating whether diversity in glacial periods is consistently lower than diversity in interglacial periods. Additionally, we apply comparative analyses to determine a potential faunal shift at the MBE, a Pleistocene event describing a fundamental shift in global climate.ResultsThe deep Norwegian Sea diversity was not lower during glacial periods compared to interglacial periods. Holocene diversity was exceedingly lower than that of the last glacial period. Faunal composition changed substantially between pre‐ and post‐MBE.Main conclusionsThese results reject the glacial disturbance hypothesis, since the low glacial diversity is the important precondition here. The present‐day‐style deep Norwegian Sea ecosystem was established by the MBE, more specifically by MBE‐induced changes in global climate, which has led to more dynamic post‐MBE conditions. In a broader context, this implies that the MBE has played an important role in the establishment of the modern polar deep‐sea ecosystem and biodiversity in general.

Unravelling the molecular dimensions of atmospheric Micro(nano)Plastics: Exploring potential impacts on human health and strategies for detection

Numerous studies have been conducted to limit the impact of micro (nano)plastics (MNPs) on the environment, specifically in land and sea ecosystems. However, we still have limited knowledge of their occurrence in the troposphere and the potential health risks correlated with acute and long-term exposure. Recent studies suggest that atmospheric MNPs could pose significant threats to human health. These small particles can be inhaled and penetrate deep into the lungs, leading to the development of non-communicable diseases such as cancer, metabolic disorders, and pulmonary dysfunction. It is crucial to continue researching the impact of atmospheric MNPs on human health to develop appropriate measures to mitigate their effects. In this article, we have conducted a comprehensive analysis of the harmful effects that exposure to atmospheric MNPs can have on human health. We have emphasized the importance of using advanced optical and analytical sensor-based techniques to recognize and characterize these particles' sources, prevalence, and distribution in the atmosphere. It is critical to use cost-efficient, artificial intelligence-based approaches to broaden the scope of the problem and design efficient solutions to improve environmental and public health.

Thirty years of change: Assessing the dynamics of fish communities in Daya Bay, a semi-enclosed coastal ecosystem of the South China sea

Daya Bay is a semi-enclosed bay in the South China Sea which is a coastal ecosystem with significant ecological and economic value that is subjected to a variety of anthropogenic disturbances. However, long-term variation in fish community structure in this Bay remains uncertain. In this study, we aimed to explore the changing characteristics of fish species composition and community structure in Daya Bay during the past 30 years using data from 1989 to 2021 from bottom trawl surveys and historical literature data. As of now, a total of 544 species of fish have been identified in the Bay, belonging to 24 orders and 125 families. The structure of the fish community in the bay has changed over time. Firstly, there has been a clear decrease in the number of species and biomass of large fish. Secondly, the number of fish constituent orders and families has decreased. Moreover, both the average taxonomic distinctness and variation in taxonomic distinctness decreased from 1989 to 2021. Thirdly, there is low similarity among fishes at different time phases and distinct changes in the composition of dominant species. Present results indicate that the fish community structure in Daya Bay has tended to reflect a decline in diversity, shifts in composition, and shrinking of fish body size in the past 30 years. This study improves our understanding of fish species composition and its drivers over time in Daya Bay, providing important knowledge to support the protection and restoration of this ecosystem and the important ecosystem services it provides.

Distribution and in vivo Observations of the Boa Dragonfish Stomias boa (Stomiidae) in Deep-Sea Canyon Ecosystems of the Northwestern Mediterranean Sea

Distribution and in vivo Observations of the Boa Dragonfish Stomias boa (Stomiidae) in Deep-Sea Canyon Ecosystems of the Northwestern Mediterranean Sea

Erratum: Response of cetaceans to fluctuations of pelagic fish stocks and environmental conditions within the Celtic Sea ecosystem

Erratum: Response of cetaceans to fluctuations of pelagic fish stocks and environmental conditions within the Celtic Sea ecosystem

A Historical Plankton Index: Zooplankton abundance in the North Sea since 800 CE

The North Sea region boasted one of the world’s most important fisheries for many centuries. Climate directly and indirectly influences the development and survival of many important pelagic fish in the North Sea ecosystem. One indirect influence is the food availability in the form of phyto- and zooplankton abundance, which is strongly controlled by environmental factors. One of these environmental factors is local sea surface temperatures. A negative correlation between zooplankton abundance and sea surface temperature is well established for the epeiric sea on the European continental shelf. Continuous temporal observations of North Sea zooplankton production only exist since 1958. Therefore we developed a Historical Plankton Index (HPI) from 800 CE onwards to extend our record of temperature-driven zooplankton abundance in the North Sea over a multi-centennial time scale. For this we used the North Atlantic temperature reconstructions and associations between zooplankton abundance and contemporary sea surface temperatures established applying a General Additive Modelling (GAM) approach. We then examined the association between the HPI and historical landings from the Dutch commercial herring fishery in the 17th century to test the utility of our HPI. We examine the potential influence of food availability (in terms of zooplankton abundance) on the fishery, the evolution of which is often only considered in terms of human influences such as conflict, fishing gear and demand for fish as a commodity. We find that under certain conditions the HPI can explain 20% of the variability in Dutch herring landings. This highlights the importance of developing long-term and large-scale indices of natural marine ecosystem dynamics to understand the historical fortunes of the commercial fishing industry. The results are directly relevant to the United Nations’ sustainable development goal 14 – life below water.

Deep sea treasures - Insights from museum archives shed light on coral microbial diversity within deepest ocean ecosystems

Deep sea benthic habitats are low productivity ecosystems that host an abundance of organisms within the Cnidaria phylum. The technical limitations and the high cost of deep sea surveys have made exploring deep sea environments and the biology of the organisms that inhabit them challenging. In spite of the widespread recognition of Cnidaria's environmental importance in these ecosystems, the microbial assemblage and its role in coral functioning have only been studied for a few deep water corals. Here, we explored the microbial diversity of deep sea corals by recovering nucleic acids from museum archive specimens. Firstly, we amplified and sequenced the V1–V3 regions of the 16S rRNA gene of these specimens, then we utilized the generated sequences to shed light on the microbial diversity associated with seven families of corals collected from depth in the Coral Sea (depth range 1309 to 2959 m) and Southern Ocean (depth range 1401 to 2071 m) benthic habitats. Surprisingly, Cyanobacteria sequences were consistently associated with six out of seven coral families from both sampling locations, suggesting that these bacteria are potentially ubiquitous members of the microbiome within these cold and deep sea water corals. Additionally, we show that Cnidaria might benefit from symbiotic associations with a range of chemosynthetic bacteria including nitrite, carbon monoxide and sulfur oxidizers. Consistent with previous studies, we show that sequences associated with the bacterial phyla Proteobacteria, Verrucomicrobia, Planctomycetes and Acidobacteriota dominated the microbial community of corals in the deep sea. We also explored genomes of the bacterial genus Mycoplasma, which we identified as associated with specimens of three deep sea coral families, finding evidence that these bacteria may aid the host immune system. Importantly our results show that museum specimens retain components of host microbiome that can provide new insights into the diversity of deep sea coral microbiomes (and potentially other organisms), as well as the diversity of microbes writ large in deep sea ecosystems.

The interplay of co-occurring ecosystem engineers shapes the structure of benthic communities – a mesocosm experiment

IntroductionEcosystem engineers play a pivotal role in shaping habitats through their activities and presence. In shallow Baltic waters, seagrasses, patch-forming mussels, and infaunal clams modify soft bottom habitats, impacting benthic community structure. While the individual effects of these ecosystem engineers are well studied, interactions among co-occurring engineers are poorly understood. MethodsWe conducted a mesocosm experiment to assess the independent and combined impacts of seagrass (Zostera marina), epifaunal mussels (Mytilus spp.), and infaunal clams (Macoma balthica) on invertebrate colonization in soft sediments. ResultsOur findings reveal significant engineer-driven alterations in macrofaunal community structure. Combined engineer effects diverged from individual impacts, indicating potential synergies or antagonisms in sediment (re)colonization. Notably, a higher number of engineer species positively affected the diversity of settled macrofauna, with the lowest macrofaunal abundance and biomass but the highest Shannon diversity found in the presence of all three engineers. DiscussionResults suggest that seagrass, mussels, and clams influence benthos through larval settlement and sediment biogeochemistry, providing insights into the distinct roles of habitat-forming organisms in shaping the benthic communities in coastal ecosystems of the Baltic Sea.

Investigating ecosystem connections in the shelf sea environment using complex networks

Abstract. We use complex network theory to better represent and understand the ecosystem connectivity in a shelf sea environment. The baseline data used for the analysis are obtained from a state-of-the-art coupled marine physics–biogeochemistry model simulating the North West European Shelf (NWES). The complex network built on model outputs is used to identify the functional groups of variables behind the biogeochemistry dynamics, suggesting how to simplify our understanding of the complex web of interactions within the shelf sea ecosystem. We demonstrate that complex networks can also be used to understand spatial ecosystem connectivity, identifying both the (geographically varying) connectivity length-scales and the clusters of spatial locations that are connected. We show that the biogeochemical length-scales vary significantly between variables and are not directly transferable. We also find that the spatial pattern of length-scales is similar across each variable, as long as a specific scaling factor for each variable is taken into account. The clusters indicate geographical regions within which there is a large exchange of information within the ecosystem, while information exchange across the boundaries between these regions is limited. The results of this study describe how information is expected to propagate through the shelf sea ecosystem, and how it can be used in multiple future applications such as stochastic noise modelling, data assimilation, or machine learning.

New insights into the Weddell Sea ecosystem applying a quantitative network approach

Abstract. Network approaches can shed light on the structure and stability of complex marine communities. In recent years, such approaches have been successfully applied to study polar ecosystems, improving our knowledge on how they might respond to ongoing environmental changes. The Weddell Sea is one of the most studied marine ecosystems outside the Antarctic Peninsula in the Southern Ocean. Yet, few studies consider the known complexity of the Weddell Sea food web, which in its current form comprises 490 species and 16 041 predator–prey interactions. Here we analysed the Weddell Sea food web, focusing on the species and trophic interactions that underpin ecosystem structure and stability. We estimated the strength for each interaction in the food web, characterised species position in the food web using unweighted and weighted food web properties, and analysed species' roles with respect to the stability of the food web. We found that the distribution of the interaction strength (IS) at the food web level is asymmetric, with many weak interactions and few strong ones. We detected a positive relationship between species median IS and two unweighted properties (i.e. trophic level and the total number of interactions). We also found that only a few species possess key positions in terms of food web stability. These species are characterised by high median IS, a middle to high trophic level, a relatively high number of interactions, and middle to low trophic similarity. In this study, we integrated unweighted and weighted food web information, enabling a more complete assessment of the ecosystem structure and function of the Weddell Sea food web. Our results provide new insights, which are important for the development of effective policies and management strategies, particularly given the ongoing initiative to implement a marine protected area (MPA) in the Weddell Sea.

Diversity and dynamics of tintinnids communities from Romanian Black Sea, in 2021

Tintinnids are tiny ciliates from microzooplankton that are very important due to their implication in the microbial food web and for the fact that in the last two decades a considerable number of non-indigenous species have entered and acclimatized in the Black Sea basin. The paper presents the species diversity and dynamic of microzooplanktonic tintinnids’ abundance as a result of two cruises carried out in May-June and August-September 2021, along the Romanian Black Sea coast. We identified 23 tintinnid species in total, with a higher diversity in the surface layer compared to those of depth. The species Eutintinnus sp. and Salpingella decurtata were found eclusively in the 10 m layer. Tintinnopsis cylindrica represented 74% of the mean biomass of tintinnid’s community from May-June, the best quantitative representation recorded in the Romanian coast's northern sector. Amphorellopsis acuta represented 91% of the mean biomass of tintinnid’s community in August-September. The biotic component was also correlated with temperature and salinity to give more information regarding spatial and temporal variations from one area to the other. The findings contribute to the knowledge of microzooplankton communities in the Romanian Black Sea region. The data on species composition, abundance distribution, and environmental correlations enhance our understanding of the ecological dynamics and potential ecological implications of tintinnid communities. This study brings valuable information to the understanding of the microzooplankton component in the Black Sea ecosystem.

Morphological analysis of resorption and degenerative processes in gonads of fishes — representatives of different families in reservoirs Dagestan part of the Middle Caspian Sea

In recent decades, the vulnerability of the Caspian Sea ecosystem has been observed due to large-scale anthropogenic impact. Due to the limited number of studies on resorption and degenerative processes in fish gonads, it was important to evaluate these regularities in commercial fish species — representatives of different families in the water bodies of the Dagestan part of the Middle Caspian Sea. In the process of our own research and analyzed literature data, the peculiarities and character of resorption passage when it is of mass character were revealed and the reasons causing it were established. In addition, the phases (stages) and conditions necessary for this process, its duration and irreversibility were studied. The biological significance of resorption has been established. Disturbances revealed in the external morphology of germ cells may be a predictor of profound changes in their structure and function. To clarify and elucidate the possibility of participation of individuals of the analyzed fish species in the spawning process with abnormal types of gonads, it is necessary to conduct a more detailed study of the sex glands at different levels of their organization, including cellular, tissue and organ levels. All the obtained factual data, regularities and revealed peculiarities in the reproductive processes in the studied species with different biology provide an opportunity for further scientific knowledge of all parts of the reproductive cycle in fish in different ecological conditions. We consider the revealed peculiarities of functioning of reproductive systems, mechanisms of adaptation of fishes to different conditions of existence as significant and necessary for solving many theoretical questions — in the field of morphofunctional and ecological analyses of evolutionary process, as well as such urgent practical problems as obtaining artificially full-fledged eggs and milk for fish breeding in pond conditions; for biologically justified exploitation of fish resources in natural reservoirs, which provide fish with high fecundity.

A chlorophyll a, non‐photochemical fluorescence quenching correction method for autonomous underwater vehicles in shelf sea environments

AbstractAutonomous underwater vehicles provide water column observations of phytoplankton biomass using chlorophyll a (Chl a) fluorometers. However, under high incident light, phytoplankton fluorescence yield decreases in a process known as non‐photochemical quenching, resulting in a reduced Chl a fluorescence signal. Methods have been developed to identify and remove the quenched signal from observations by autonomous underwater vehicles. These existing methods rely on assumptions of the homogeneity of the system, both in terms of time (i.e., between day and night observations) and space (i.e., within the water column or between neighboring profiles). These assumptions are not valid in shallow shelf seas or when sampling across different water masses. Thus, we evaluate six new quenching correction methods based on an existing ocean‐based method, but adapted for a continental shelf sea environment where the water mass changes between night and day observations. We have included two main changes to the existing method. First, we interpolate the unquenched, nighttime signal across the daytime observations and use this as a reference for correcting the quenched, daytime signal. Second, we explore the inclusion of a fluorescence quenching depth limit. By interpolating nighttime observations across daytime periods, the diel changes in non‐photochemical quenching were separated from the phytoplankton population changes. The proposed methods all show improved performance compared to existing approach. The methods presented here, and the approach used to evaluate them, are applicable in other shelf sea environments, enabling studies using autonomous Chl a fluorescence data across shelf sea ecosystems.

Critical periods in the marine life history of juvenile western Alaska chum salmon in a changing climate

Recent precipitous declines in western Alaska chum salmon Oncorhynchus keta returns followed unprecedented warming in the northern Bering Sea ecosystem. To better understand the role of anomalous events on the early marine ecology of juvenile chum salmon in the northern Bering Sea, we utilized time-series observations over a 17 yr period (2003-2019) of sea surface temperature (SST) and juvenile chum salmon size (length and weight), diet, energy density, and relative abundance. Particular attention was paid to more recent (2014-2019) years in which there was unprecedented loss of sea ice in the northern Being Sea in comparison to previous warm (2003-2005) and cold (2006-2013) periods. Our findings indicate significant correlations between SST and juvenile chum salmon relative biomass (positive) and energy density (negative). We found that juvenile chum salmon were larger during warm periods than during cold periods; however, there was no significant difference in their length and weight between the warm periods. Juvenile chum salmon fed on lower quality prey during warm periods than during cold periods, with an increase in the proportion of lower quality prey during the recent warm period. Consequently, the energy density of juvenile chum salmon was also lower during warm periods than during cold periods, with the lowest values occurring during the recent warm period (2014-2019). These results identify a shift in energy allocation and/or prey quality of juvenile chum salmon with temperature and illustrate how marine ecosystems have altered the nutritional condition of juvenile chum salmon prior to winter, when energy reserves are considered critical to survival.

When the “best available science” is not good enough: The need for supporting scientific research in the United Nations treaty to protect biodiversity beyond national jurisdiction

The distant ecosystems of the high seas are growing closer every year as humans create and deploy novel technologies to harvest resources from the open ocean. A new international agreement, the treaty for Biodiversity Beyond National Jurisdiction (BBNJ), is intended to ensure the conservation and sustainability of such ecosystems. Among other issue areas, the BBNJ agreement establishes requirements for conducting Environmental Impact Assessments (EIAs) for activities within (or impacting) Areas Beyond National Jurisdiction. This short communication argues that the EIA process created by the BBNJ treaty will not be effective at achieving the goals of conservation and sustainable use of marine biodiversity beyond national jurisdiction without strong scientific support. The basic problem is that EIAs require more information than what is available for even the most accessible marine ecosystems in Areas Beyond National Jurisdiction. We consider three cases of ocean uses – plastic cleanups, deep seabed mining, and mesopelagic fisheries – to demonstrate that available scientific knowledge is insufficient to conduct and evaluate informative EIAs. We suggest three ways that the Scientific and Technical Body established by the BBNJ agreement could be augmented by the Conference of Parties in order to help avoid dysfunction in the EIA process, support scientific discovery, and increase environmental protection.

Automated identification of invasive rabbitfishes in underwater images from the Mediterranean Sea

Abstract Coastal ecosystems of the Mediterranean Sea are among the richest in non‐indigenous species, mostly due to the establishment of species coming from the Red Sea through the Suez Canal. Two herbivorous rabbitfishes, Siganus rivulatus and Siganus luridus, are already invasive in the south‐eastern part of the Mediterranean Sea where they cause ecological damage by overgrazing algae. The early detection and the counting of these non‐indigenous species in the rest of the Mediterranean Sea is thus a major challenge for scientists and ecosystem managers. However, analysing images from divers or remote cameras is a demanding task. Here, a dataset of 31,285 images of Siganus spp. and of six common native fishes to the Mediterranean Sea was built from 40 underwater videos recorded at three reef habitats. A deep learning algorithm was then trained to identify Siganus spp. on images containing the eight Mediterranean species. Finally, the algorithm and a post‐processing filtering were tested with an independent dataset of 2024 images. The model had a recall of 0.92 for the Siganus genus (i.e., two Siganus species combined). After a confidence‐based post‐processing, the recall increased to 0.98 with only 4 out of 272 images of Siganus spp. being misclassified. Accuracy reached a score of 0.61 meaning that experts would have to discard false positives. Images of five native species not present in the training dataset yielded similar false positive rates than species present in the training dataset. Overall, the automatic processing of images by the model and then the checking of putative Siganus images by experts required up to five times less effort than a full processing by experts. The algorithm can help to efficiently detect these two invasive fishes in underwater images to evaluate progress towards conservation objectives and accelerate citizen‐based monitoring of coastal ecosystems.

Diverse foraging strategies of breeding Swinhoe's Storm-petrel in the productive marginal sea of the Northwest Pacific

Understanding the foraging behavior is essential for investigating seabird ecology and conservation, as well as monitoring the well-being of the marine environment. Breeding seabirds adopt diverse foraging strategies to maximize energy gains and cope with the intensified challenges of parenting and self-maintenance. Such trade-off may stem from the heterogeneity of food resources and the constraints of central place foraging. Nevertheless, abundant marine productivity could alleviate the energy limitation for seabirds, resulting in a consistent foraging approach. Here, we investigated the foraging strategy during the breeding season of a cryptic small-sized seabird, Swinhoe's Storm-petrel (Hydrobates monorhis), in the Yellow Sea, a productive marginal sea of the Northwest Pacific. Using GPS tracking, we evaluated habitat preference, quantified the foraging strategy, and tested if environmental conditions and individual traits influence foraging trips. We found that Swinhoe's Storm-petrels preferred nearshore areas with shallow water and engaged in primarily short foraging trips. Distinctive southeastward and southwestward strategies emerged when combining trip metrics, including foraging direction, duration, and maximum distance. The bathymetry, proximity to the coastline, and sea surface temperature differed in two foraging strategies. Foraging strategies exhibited flexibility between individuals, potentially explained by wing morphology, in which longer-winged birds are more likely to embark on longer-distance foraging trips. These findings highlight the impact of environmental factors and individual traits on seabirds' foraging decisions in productive marginal sea ecosystems. Our study also provides valuable insights into the foraging ecology of this Asian endemic storm-petrel.