Sea Islands Research Articles

Species composition and distribution of Sponges in some islands in Vietnam sea

Research results from 2003 to present, in same Vietnamese islands, have identified 205 Sponges species belonging to 85 genera and 56 families, 22 orders of 3 classes, including Dermospongia class (203 species), two classes Calcarea and Homoscleromorpha has only 1 species in each class. Among these, there are 3 species new to science: Cladocroce pansinii Bertolino & Calcinai, 2023, Cladocroce lamellata Bertolino and Calcinai, 2023 and Spongilla marconii. The diversity of Sponges is quite high, reaching 2.4 species/genus, 3.66 species/family and 9.32 species/order. Orders with the highest number of species include Haplosclerida (55 species), followed by Poecilosclerida (29 species), Dictyoceratida (21 species), and Halichondrida (20 species). The South Central islands have the highest number of species (121 species), followed by the North Central islands (65 species), the Northeastern islands of Vietnam (57 species), Spratly Islands (37 species) and Phu Quoc (15 species). Species Cinachyrella australiensis, Dysidea fragilis, Dysidea cinerea can live at a water depth of 134 m. The biomass of Sponges varies from 0.14–2.5 kg/m2.

Ship path planning based on improved multi-scale A* algorithm of collision risk function

To improve the safety of ship navigation in complex sea areas and reduce planning time while achieving optimal path planning. The paper proposes an improved A* algorithm that incorporates ship collision risk assessment. The paper utilizes multi-scale raster maps to divide the sea chart in the context of complex sea areas, and combines the Line-of-sight (LOS) algorithm to solve the zigzag paths that may appear in this planning context. Moreover, in order to improve the efficiency of optimal path planning in the context of complex sea areas while ensuring path safety, the paper proposes a collision risk function to optimize the determination of the cost of A* algorithm nodes, thereby enhancing the heuristic function of the A* algorithm. The improved A* algorithm can consider both path length and collision risk to plan the optimal path and to enhance the overall quality of the planning results. To verify the advantages of the improved algorithm proposed in the paper, the Zhoushan Islands sea area with complex environment is selected as the planning background for simulation study. The results show that the improved algorithm with the introduction of the collision risk function reduces the path planning time, the number of expanded nodes, and the path length by 30%, 11%, and 5.8%, respectively, compared with the original algorithm, which can effectively reduce the computational burden of the algorithm. This study provides a relatively complete and scientific route planning strategy for the study of the safe navigation of smart ships in complex sea areas.

Foraging in contrasting oceanographic regions impacts the fatty acid profile of two closely related pelagic seabirds

Coastal urbanisation negatively affects marine ecosystems through habitat degradation and pollution. Cory’s (Calonectris borealis) and Scopoli’s (C. diomedea) shearwaters are closely related species inhabiting the Northeast Atlantic Ocean and the Mediterranean Sea, respectively. This study assesses the fatty acid profile, with the trophic and foraging ecology, of Cory’s and Scopoli’s shearwaters breeding at Berlenga (Atlantic Ocean) and Chafarinas (Mediterranean Sea) Islands. The diet quality of Scopoli’s shearwaters is expected to be generally lower, characterised by reduced levels of ω-3 fatty acids. Additionally, higher concentrations of specific fatty acid trophic markers are anticipated, reflecting the Mediterranean's semi-enclosed environment, low productivity, and pollution challenges. These markers include oleic acid, vaccenic acid, trans fatty acids (indicative of urban and industrial discharges), and odd-chain fatty acids (indicative of bacterial presence). This study supported these predictions, with Scopoli’s shearwaters foraging in the Mediterranean having higher concentrations of oleic and vaccenic acids, odd-chain fatty acids, and trans-palmitoleic acid in their plasma. Yet, concentrations of ω-3 were also higher in Scopoli’s shearwaters. This may result from diverse prey availability and selection, and different habitat exploitation, partially supported by differences in the trophic ecology and foraging patterns of both species; or from an enhanced immunological basal response of Scopoli’s shearwaters to cope with higher anthropogenic pressure in the western Mediterranean Sea. Further studies including specific diet and contaminant analyses are crucial to understand differences in fatty acid profiles of seabirds inhabiting both oceanic basins and the implications of diet quality for seabird populations.

Ecosystem-based fisheries management of crab fisheries in the Bering Sea and Aleutian Islands

We review ecosystem-based fisheries management (EBFM) of crab fisheries in the Bering Sea and Aleutian Islands (BSAI) and discuss considerations for future EBFM efforts under a rapidly changing climate. Specifically, we review governance frameworks, ecosystem policy, fishery ecosystem plans, catch accounting systems, trawl bycatch controls, trawl area closures and habitat protections, gear modifications, a Crab Rationalization Program, Ecosystem and Economic Status Reports, and Ecosystem and Socioeconomic Profiles. The strongest EBFM features of this management system include mechanisms to avoid overfishing, use of scientific knowledge, consideration of ecosystem connections, appropriate monitoring, acknowledging uncertainty, stakeholder involvement, and decisions that reflect societal choice. Some EBFM principles, such as the efficacy of gear and area closures and accounting for the dynamic nature of ecosystems have room for improvement. In spite of the large number of EBFM measures in place, three of the eight BSAI crab stocks with biomass estimates were below their minimum stock size thresholds, and thus classified as “overfished” in 2023. The lack of apparent correspondence between implemented EBFM actions and crab stock trends may indicate that environmentally driven sporadic recruitment, spikes in natural mortality, and stock range shifts mute favorable responses to EBFM actions or that outstanding critical EBFM measures have yet to be addressed. In the face of recent large-scale changes in the marine ecosystems of the BSAI and an outlook for greater changes in the future, it is increasingly important to routinely reevaluate interactions between crab, their ecosystems, fisheries and fishing communities.

Spatial and Temporal Diversity of Fishes at Wuzhizhou Island in the South China Sea Based on Environmental DNA

Spatial and Temporal Diversity of Fishes at Wuzhizhou Island in the South China Sea Based on Environmental DNA

Development of Project-based Mathematics Learning (PjBL) Using the Island Sea Context

Implementing learning using the PjBL model will be meaningful for students if it is connected to the students’ world. This research aims to produce a mathematics learning tool with the PjBL model that is valid, practical, and effective in the context of the island sea. This research is development research that aims to develop an island sea-based PjBL learning model. The development stages use a 4D model which consists of definition, design, development, and dissemination; however, in this research dissemination was not carried out. The research results show that the mathematics learning tools using PjBL are valid, practical, and effective. The learning tools used in learning are proven to be very practical for student activities and improve learning outcomes. The accompanying impact that emerges is communication skills and complex problem solving. Keywords: project-based learning, island marine context, 4D model, problem solving

Prominent Increase in Air Temperatures on Two Small Mediterranean Islands, Lastovo and Lošinj, Since 1998 and Its Effect on the Frequency of Extreme Droughts

The article analyzes the development of air temperatures and precipitation on two remote islands in the Adriatic Sea from 1961 to 2023, examining annual and monthly time scales. Lastovo Island is located in the southern Adriatic, and Lošinj Island is situated 277 km north, and both exhibit a sharp rise in air temperatures since 1998, though precipitation series show no significant trends of an increase or decrease. Using the New Drought Index (NDI) method, this study calculated drought intensities for the period 1961–2023. The analyses conducted in this study undoubtedly indicate a rising frequency and intensity of droughts, with severe droughts doubling and extreme droughts increasing fourfold in the recent period (1998–2023) compared to the previous one (1961–1997). The most pronounced increase in severe and extreme droughts occurs specifically from June to August. This trend is likely applicable to many small Mediterranean Islands, which number over 10,000 and have a permanent population of more than 1.6 million people, with numbers significantly rising during the tourist season. The increased water demand for agriculture and daily use, combined with increased drought risk, not only exacerbates the potential for forest fires but also threatens social structures and ecological conditions. This is particularly critical as the combination of drier conditions and increased fire risk poses a significant challenge, endangering natural landscapes and valuable historical sites that are integral to the islands’ identity and heritage. This study’s findings indicate a dangerous trend likely to persist and worsen with continued increases in air temperatures in the Mediterranean region.

Ottoman Foundations in Chios

Chios Island is one of the important islands located in the Sea of Islands. It remained under Ottoman rule for approximately 347 years from 1566 to 1913. While the Ottomans established their own administration here after the conquest, they also brought the traditional Turkish-Islamic culture to the island. The elements of this culture, such as love for humanity, respect for differences, peace, tolerance and sacrifice, were brought to the island through foundations. While the foundations ensured the continuation of the Turkish presence here with the mosques, mescits, dervish lodges and zawiyas they established, they played a certain role in the economic and commercial life of the island with structures such as inns, shops, bazaars, plots of land and mills. Foundations were established by both members of the Ottoman dynasty and statesmen. Knowing these will make it possible to make a more accurate assessment of the Ottoman administration on the island. The Ottomans created many architectural and cultural works on this island. Among these are many mosques, masjids, fountains, public fountains, baths, lodges and zawiyas. Some of these are the Hamidiye Mosque, Bayraktar Mosque, Piyale Pasha Mosque, Misirlizade Ibrahim Pasha Mosque and Foundation, Salih Pasha Mosque and Madrasah, Melek Mehmet Pasha Fountain and Laleli Mosque. According to state records from 1894, there were nine mosques, two madrasahs, three lodges, ninety-eight churches, one monastery, two synagogues, two baths and eighteen fountains on the island. Today, there are eight mosques, one masjid, one lodge, three baths, one fountain and one inn in Chios as Ottoman works. Some of these will be discussed in this study.

The history of the El Niño–Southern Oscillation and sea surface salinity during 1376–1500 CE reconstructed by Porites coral δ18O from Huangyan Island, South China Sea

The El Niño–Southern Oscillation (ENSO) is the most influential climatic phenomenon affecting global ecosystems, water use, and agriculture on an interannual scale. However, limited instrumental records make it difficult to fully understand the characteristics of ENSO events. In this study, we used both monthly-resolved Porites coral δ18O records, i.e., living Porites corals of δ18O–HYDL4 (1992–2015) and subfossil Porites corals of δ18O–HYD3 (1376–1500 CE), from Huangyan Island in the South China Sea (SCS), to reconstruct the moderate intensity ENSO and sea surface salinity (SSS) during 1376–1500 CE. The results show that the SSS was higher but the frequency of moderate-to-high intensity ENSO events was lower than the present during 1376–1500 CE. ENSO activity was generally similar to or slightly lower than that of today, but it included several very strong ENSO events in the first substage (1376–1450 CE), while it was relatively quiet in the second substage (1451–1500 CE). More moderate-intensity ENSO events may have occurred in the relatively warm climate. The variation in coral δ18O was dominated by multiple factors in this region. SST, ENSO and the Pacific Decadal Oscillation (PDO) may be the dominant factors influencing the changes in coral δ18O at different timescales.

McDonald Islands Phonolitic Lavas: Evidence for Zonation of the Kerguelen Plume

AbstractThe McDonald Islands, together with Heard Island and the Kerguelen Archipelago, are volcanic islands on the mostly submerged Kerguelen Plateau, and the products of the long‐lived Kerguelen mantle plume (at least 130 Myr; Coffin et al., 2002, https://doi.org/10.25919/jw5f‐ad35). The first multibeam bathymetry data acquired around the Heard and McDonald islands reveal > 70 sea knolls surrounding the McDonald Islands and three sea knolls north of Heard Island. Rocks dredged from McDonald Islands sea knolls include fresh vesicular phonolitic lavas, phonolitic obsidian, phonolitic pillow fragments, and one basanite. These are the first phonolites sampled from the seafloor on the Kerguelen Plateau. Dredging of one sea knoll north of Heard Island recovered basaltic lavas. Lavas from the sea knolls are young, returning 40Ar/39Ar plateau ages of 73.7 ± 15.1 ka to 7.0 ± 2.7 ka for McDonald Islands sea knoll phonolites and 9.0 ± 1.3 ka for the Heard Island sea knoll. We define a new magma series, the McDonald Series, characterized by low εHf (−3.9 to −4.4) and lower Δ207Pb/204Pb (4.5–4.8) and Δ208Pb/204Pb (79–85) than all other lavas on the Kerguelen Plateau. This newly defined series is the product of a relatively young (Pleistocene‐Holocene) phase of volcanism produced by a distinct component of the Kerguelen mantle plume. We propose that McDonald Series phonolites together with 53.4 Ma lavas previously dredged from Ninetyeast Ridge provide evidence for zonation of the Kerguelen mantle plume.

Internal tidal dynamics and associated processes at highly supercritical slopes in Banda Sea: Lessons from the oceanic island of Ambon, eastern Indonesia

Interactions between the deep sea and steep-sloping oceanic islands generate physical processes with potential impacts on sediment resuspension and ocean productivity. While studies have been conducted in the open oceans, those focusing on oceanic islands of the deep Banda Sea in eastern Indonesia are lacking. Here, we present the first observational evidence of vertical mechanisms (i.e. internal tidal reflection, internal hydraulic jumps) at the highly supercritical slope in outer Ambon Bay (OAB) in Ambon Island – an oceanic island in the Banda Sea. A 23-h CTD yoyo experiment combined with ADCP measurements conducted during spring flood and ebb tides demonstrated tidally-varying vertical temperature, salinity and density profiles. During spring flood tide, incoming internal tides were reflected by OAB's highly supercritical slope back to the deep sea with isopycnals and isotherms showing sharp downward plunges (downward vertical velocity = 6.5–8.3 × 10−3 m/s), and the internal tidal amplitude reaching 90–110 m. The reflection during flood tide caused seaward overturning flow at deeper depths despite the prevailing landward flow at the upper layers. During spring ebb tide, internal hydraulic jumps (upward vertical velocity = 6.1–6.48 × 10−3 m/s) occurred to rebound the downward plunges of isopycnals and isotherms as flood tide relaxed with the observed amplitude of internal tides of 90 m. We also observed weakened seaward ebb flow during the isothermal uplifting (when hydraulic jumps occurred), and subsequent intensified landward flow at the end of spring ebb tide indicating strong upslope flow when isotherms reached the maximum shoaling depths. Taken together, the observed vertical mechanisms indicate the conservation of energy at the highly supercritical slope of OAB evident by the comparable vertical velocities. An embedded turbidity-chlorophyll profiler in the CTD reveals that internal tidal activities at the highly supercritical slopes OAB may induce bottom nepheloid layers, and influence ocean productivity by regulating the vertical distribution of phytoplankton biomass.

Too many spines, or an integrative foundation of the Echiniscus spinulosus morphogroup (Heterotardigrada: Echiniscidae)

AbstractHistorical taxonomic bias has started to be effectively removed in tardigrade taxonomy in the last two decades by the application of modern statistical, genetic and morphological tools. Many of the “old” tardigrade taxa have been redefined, and their succinct original diagnoses—refined, finally resulting in making them properly identifiable and less enigmatic. At the same time, many of the “old” species were synonymised and perished in the taxonomic wastebasket. Herein, we address the species distinction between Echiniscus spiniger Richters, 1904 and Echiniscus spinulosus (Doyère, 1840) by means of integrative analyses of 11 European populations collected in the Mediterranean, the Carpathians and the Baltic Sea islands of Öland and Gotland, covering the southern distribution zone and northernmost known localities within trustworthy geographic range of these species. We disclose that, as previously hypothesised, E. spiniger is conspecific with E. spinulosus, and synonymised accordingly. We deliver morphological evidence supporting the triphyly of the morphogroup, with all tropical and subtropical species truly lacking intracuticular pillars, whereas the Palaearctic lineage corresponding solely to E. spinulosus and Afrotropical lineage represented by E. belloporus Gąsiorek and Kristensen, 2018—occasionally exhibiting pillars in some specimens. A synopsis and key to all representatives of the E. spinulosus morphogroup are provided, pinpointing to some problems that must be taken into consideration during identification and solved in the future.

The Geopolitical Imaginaries in Moby-Dick; or, The Whale and Hakugei: Legend of the Moby Dick

This paper explores the geopolitical imaginaries in Herman Melville’s Moby-Dick; or, The Whale (1851) and in the Japanese science fiction animation titled Hakugei: Legend of the Moby Dick (1997-1999) by the Japanese animation artist Osamu Dezaki. Although it is an adaptation of Moby-Dick, the setting of Hakugei has been creatively changed from the sea to space. In the mid-nineteenth century, when Melville chose the sea as the setting of his quest novel, the sea was inextricably intertwined with the nineteenth-century myth of U.S. expansionism. Melville presents a double vision of imaginary islands in the South Sea and the actual geopolitical relationships between existing transatlantic countries. Yet in the second half of the twentieth century, especially in the wake of Transpacific tensions, the sea as a place of quest among Japanese writers could not be delineated in the same kind of prefigurative language used by Melville, such as by drawing on symbolism. Instead, the animation reflects a Cold War psychology that was prevalent among Japanese after the defeat of World War II. As this paper suggests, Hakugei displays both fear and hope for the geopolitical transformation of the Pacific Rim countries and their future safety by choosing outer space as a site for the fable. It is in this way that the Japanese animator Dezaki draws on Melville’s Moby-Dick as a source text by engaging geopolitics, anti-war psychology, and uneasiness toward expansionism. Melville’s pacifism can be argued for as major transcultural influence, at the very least, driving Hakugei’s anime characterization. In fact, going beyond drawing on certain characters, including Ahab, Dezaki retains Melville’s anxiety over the proximity of creation and destruction in yet another era of increasing concern for world peace.

Key Drivers of Consumption, Conceptual, Sensory, and Emotional Profiling of Cheeses Based on Origin and Consumer Familiarity: A Case Study of Local and Imported Cheeses in Greece

The origin of a product, consumer familiarity, and purchasing identity are factors that affect the perception of cheese consumption. The present study aims at identifying consumers’ conceptualizations and attitudes towards local Greek cheeses of the North-Aegean Sea islands, such as Ladotyri, Graviera, Kasseri, Kaskavali, Melichloro, and Kalathaki, some of which have a Protected Designation of Origin (PDO) status, as opposed to cheeses of non-Greek origin, such as Cheddar, Regatto, and Gouda. Sensory and emotional attributes of local, local PDO, and imported cheeses, as well as drivers associated with consumers’ choice and acceptance above and beyond their sensory attributes, were studied using three methods: (a) flash profile to gain insight into the sensory positioning of products and description of samples; (b) qualitative analysis of focus groups to pinpoint consumer knowledge, preference, and consumption criteria; and (c) a new methodology for natural language processing and sentiment analysis of social media posts to determine consumer conceptualizations. Social media posts have proven to be a valuable source of linguistic and cultural data for cheeses. Local cheeses, including PDO products, were found to be linked to village life and family gatherings, home, tradition, and childhood memories, with saltiness and hardness being their main sensory attributes. Imported cheeses were linked to fast food, pizza, and snacking, with elasticity and gumminess as prominent sensory qualities. The main criteria for purchase were intended usage and versatility, taste and texture, price, and familiarity. The findings provide key sensory attributes, information about consumer purchasing criteria, and relevant vocabulary for the promotion of cheeses as agri-food and gastronomic identity key products.

Application of a GIS-Based Multi-Criteria Decision-Making Approach to the Siting of Ocean Thermal Energy Conversion Power Plants: A Case Study of the Xisha Sea Area, China

In order to achieve the goals of carbon neutrality and reduced carbon emissions, China is increasingly focusing on the development and utilization of renewable energy sources. Among these, ocean thermal energy conversion (OTEC) has the advantages of small periodic fluctuations and large potential reserves, making it an important research field. With the development of the “Maritime Silk Road”, the Xisha Islands in the South China Sea will see a growing demand for electricity, providing the potential for OTEC development in this region. Optimal site selection of OTEC power plants is a prerequisite for developing thermal energy provision, affecting both the construction costs and future benefits of the power plants. This study establishes a scientific evaluation model based on the decision-making frameworks of geographic information systems (GISs) and multi-criteria decision-making (MCDM) methods, specifically the analytic hierarchy process (AHP) for assigning weights, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) to reclassify the factors, and weighted linear combination (WLC) to compute the suitability index. In addition to commonly considered factors such as temperature difference and marine usage status, this study innovatively incorporates geological conditions and maximum offshore distances of cold seawater based on cost control. The final evaluation identifies three suitable areas for OTEC development near the Xuande Atoll and the Yongle Atoll in the Xisha Sea Area, providing valuable insights for energy developers and policymakers.

Lethal grip for an endangered endemic frog: The freshwater crab Potamon karpathos (Decapoda, Potamidae) preys on Karpathos water frog Pelophylax cerigensis (Anura, Ranidae)

Invertebrate predation on amphibians is widespread, although unreported in Europe. Here, we present documented predation of the Karpathos water frog (Pelophylax cerigensis) by the crab Potamon karpathos. Pelophylax cerigensis is an endangered, endemic species exclusively found on the Rhodes and Karpathos Islands in the South Aegean Sea, Greece. The Karpathos population is at risk due to limited suitable habitats and a scarcity of freshwater bodies on the island. From April to October, when there is no rain on the island, frogs and crabs cohabitate, sharing the same shallow ditches. Incidents of frog predation by crabs are common, indicated by numerous individuals with amputated limbs and scars, representing an additional threat to the endangered frog. Further research on the interactions between the two species is urgently required, as it has direct conservation implications.

A Spatial–Temporal Analysis and Multi-Scenario Projections of Carbon Sequestration in Sea Islands: A Case Study of Pingtan Island

A Spatial–Temporal Analysis and Multi-Scenario Projections of Carbon Sequestration in Sea Islands: A Case Study of Pingtan Island

Study on the Reinforcement of South China Sea Island Resources and the Impact on Coral Sand Using Microbially Induced Calcification Technology

This paper aims to explore the application of Microbially Induced Calcification Process (MICP) in reinforcing South China Sea island resources and to analyze its impact factors on coral sand. Through literature review and field surveys, it firstly introduces the significance of South China Sea island resources and coral sand, as well as the principles and application methods of MICP technology. Subsequently, through field investigations and experimental design, the effectiveness of MICP technology in reinforcing these islands is assessed, and the changes in coral sand during the MICP process are analyzed. Further, factors affecting coral sand, including microbial activity, environmental conditions, and other factors, are discussed. The research findings indicate that MICP technology can effectively reinforce South China Sea islands and has a significant impact on coral sand, with microbial activity and environmental conditions being among the primary factors. This study provides an important reference for further exploration of the protection and utilization of South China Sea island resources and anticipates future research directions for MICP technology in this field.

Plastid marker variation reveals immigration history in Scandinavian Syntrichia norvegica and S. ruralis (Pottiaceae, Bryophyta)

ABSTRACT Introduction Based on previous analyses of Syntrichia norvegica and S. ruralis, the idea of panmictic populations in Scandinavia can be rejected, despite the high dispersal capacities of wind-dispersed spores. We tested, using comprehensive European datasets, whether intraspecific phylogeographical structure reflects glacial and post-glacial history. We expected different entities to indicate immigration from known Late Glacial Maximum refugial areas, and habitat differentiation. Methods Using plastid markers (atpB–rbcL and rpl16), we investigated 45 and 190 Scandinavian and 17 and 15 non-Scandinavian specimens of Syntrichia norvegica and S. ruralis, respectively. Key results We revealed four intraspecific entities in Syntrichia norvegica. Two were from the Scandinavian mountains and the Alps, and one from the Scandinavian mountains only. The fourth was widespread across the Scandinavian mountains, the northern lowlands, and the Baltic Sea islands Öland and Gotland. For S. ruralis, we recovered five entities, of which three were from both Scandinavia and the Alps. One of these occurred in strongly calcareous habitats in southern Scandinavia and the Alps and dominated on Öland and Gotland. One entity was widely distributed only in Scandinavia. One was restricted to the border between boreo-nemoral and southern-boreal Scandinavia. Conclusions The plastid haplotype distribution patterns suggest glacial survival of Syntrichia norvegica and S. ruralis in refugia south, east and possibly within ice-covered areas of Scandinavia. We hypothesise that one S. ruralis entity evolved adaptations to strongly calcareous habitats. The dominance or prevalence of specific haplotypes of both species on Öland and Gotland contributes to the unique biodiversity of these islands.

Resting Cysts of the Toxic Dinoflagellate Gymnodinium catenatum (Dinophyceae) Ubiquitously Distribute along the Entire Coast of China, with Higher Abundance in Bloom-Prone Areas

Blooms of Gymnodinium catenatum have occurred occasionally in different areas of China and caused tremendous economic loss and even threatened human health. Not only is G. catenatum an important harmful-algal-bloom (HAB)-causing species, but also the only gymnodinioid dinoflagellate known to produce paralytic shellfish poisoning toxins (PSTs). Due to the germination of resting cysts, which often initiates blooms, the distribution and abundance of cysts in sediments and particularly the confirmation of cyst beds are important information for understanding and predicting dinoflagellate blooms. In this research, 199 sediment samples were collected from China’s coastal seas, ranging from the Beidaihe in the Bohai Sea (BS) to the southernmost sample from the Nansha Islands of the South China Sea (SCS). TaqMan quantitative PCR (qPCR) assays with species-specific primers and probes were developed to specifically detect the distribution and abundance of cysts in the 199 samples. The detection revealed that G. catenatum cysts were widely present in the sediments (126 of the 199 samples), with 93.55%, 74.65%, 42.37%, and 50% of the samples detected positively from the BS, YS, ECS and SCS, respectively, and covering the vast sea area from Nansha Islands to the Beidaihe area. The single-cyst morpho-molecular identification in the samples from Beidaihe confirmed the existence of G. catenatum cysts in the BS, and the positive detections of G. catenatum cysts using the qPCR methods. While G. catenatum cysts were widely distributed in all four seas of China, the average abundance was relatively low (1.0 cyst per gram of wet sediment). Three samples from the East China Sea (ECS), however, contained G. catenatum cysts at a relatively higher level (23 cysts g−1 wet sediment) than other sea areas, suggesting a pertinence of cyst abundance to the frequent occurrences of G. catenatum blooms in the area during recent years. Collectively, for G. catenatum being such an important toxic and HAB-causing species globally, the ubiquitous distribution of its cysts along the coastal waters of China and higher abundance in the bloom-prone areas warns us of a risk that cyst beds, although currently low in abundance, may seed HABs in any and many sea areas of China at any forthcoming year, and particularly those areas with records of frequent HABs outbreaks in the past.