Global ecological concern regarding the transfer of fouling organisms to ship hulls is increasing. This study investigated the species composition, dominant species, distribution patterns, community structure, and life-cycle differences of hull-fouling macroinvertebrates on five research vessels (R/Vs: Isabu, Onnuri, Eardo, Jangmok 1, and Jangmok 2) operated by the Korea Institute of Ocean Science and Technology (KIOST). Hull-fouling macroinvertebrates were collected three to five times on quadrats from the upper and middle sectors of the hull sides, bottom, and niche areas (the propellers, shafts, and thrusters). A total of 47 macroinvertebrate species were identified, represented by 8519 individuals (ind.)/m² and a biomass of 1967 gWWt/m² on the five vessels. The number of species, density, and biomass were greater on the coastal vessels Eardo, Jangmok 1, and Jangmok 2 than on the ocean-going vessels the Isabu and Onnuri. Among the coastal vessels, barnacles were the most abundant and had the greatest density, while mollusks had the highest biomass. Differences between hull sectors showed that the highest species abundance and density appeared on all hulls in ports and bays where the Jangmok 1 operated, while the highest species abundance, density, and biomass were identified in the niche areas of the Eardo, which operated farther from the coast. The hull-fouling macroinvertebrates that exceeded 1% of all organisms were the barnacles Amphibalanus amphitrite, Balanus trigonus, and Amphibalanus improvisus; the polychaete Hydroides ezoensis; the bivalves Magallana gigas and Mytilus galloprovincialis; and the amphipod Jassa slatteryi. The dominant species were cosmopolitan and globally distributed, and many of them were cryptogenic. Six native species were identified: M. gigas, H. ezoensis, the amphipod Melita koreana, the isopod Cirolana koreana, and the barnacles B. trigonus and F. kondakovi. Eight non-indigenous species (NIS) were detected: the barnacles A. amphitrite and A. improvisus, the bivalve M. galloprovincialis, the polychaete Perinereis nuntia, the amphipods J. slatteryi and Caprella californica, and the bryozoans Bugulina californica and Bugula neritina. Of the fouling macroinvertebrates found on the vessel hulls, 13% were native, and 17% were NIS. More diverse communities developed on the hulls of vessels that operated locally rather than globally or in deep oceans. The species diversity index correlated positively with the total number of anchoring days and coastal operation days and negatively with the total number of operation days and ocean operation days. The macroinvertebrates differed by the area of operation, the port of anchorage, the number of days in operation and at anchor, and the hull sectors. There is no previous research data on hull-fouling macroinvertebrates in the Republic of Korea, and this study provides a basis for future studies to identify introduced species and their differences based on operation area.

We investigated the biological impact of extensive Manila clam (Ruditapes philippinarum) aquaculture on macrobenthic communities in a tidal ecosystem in Korea. We collected macrobenthos (>1 mm in length) samples seasonally in the intertidal zone in Geunsoman, Taean, Korea from April 2011 to December 2014. We identified 146 macrobenthos species, including 60 polychaetes, 53 crustaceans, and 16 mollusks. A biota–environment matching (BIO–ENV) analysis indicated that the benthic community was affected by mean sediment grain size (Mz), total organic carbon (TOC), and R. philippinarum biomass. We found no correlation between R. philippinarum and the main dominant species (Heteromastus filiformis, Ceratonereis erythraeensis, and Ampharete arctica), which have a different feeding strategy; thus, this may result in a lack of competition for food resources. In addition, we found that flourishing R. philippinarum positively affects the macrobenthos density but negatively affects the biodiversity index. Moreover, competition between species does not occur clearly, and environmental variables (sediment, organic carbon) are important.

The Ulleung Basin of the East Sea is a biological hotspot, but studies on the macrobenthos therein are lacking. To evaluate the macrobenthos species diversity and community structure in the Ulleung Basin, we conducted a survey from 2017 to 2021. A total of 262 species of macrobenthos was detected by the survey, and the average habitat density was 243 individuals/m². The average biomass of macrobenthos was 43.7 g/m², and the average Shannon and Wiener’s diversity index was 2.3 (0.69–3.61). The dominant species were the polychaetes Terebellides horikoshii, Chaetozone setosa, Scalibregma inflatum, and Aglaophamus sp. and the bivalvia Axinopsida subquadrata. The community structure of macrobenthos differed according to water depth, and a correlation analysis using environmental variables showed that the community was affected by water temperature, salinity, and dissolved oxygen. The macrobenthic fauna in the Ulleung Basin was greatly influenced by water depth, the sedimentary environment was different, and the dominant species were also different. In addition, there was little seasonal change compared to the East Sea coast. Our findings will facilitate further investigation of benthic ecosystems throughout the East Sea.

Pollution associated with marine debris is of global ecological concern, as it threatens wildlife and local economies. Submerged marine debris alters local benthic species composition and community characteristics. The study site of Jaguri, Jeju Island, where a variety of submerged marine debris was found, was used to investigate the impact of submerged marine debris on the macrobenthic fauna of sandy and rocky substrates. The dominant macrobenthos taxon differed by sediment type; the polychaete Armandia lanceolata was dominant in sandy bottom environments and the mollusk Leiosolenus lischkei was dominant in rocky bottom environments. The presence of marine debris was associated with differences in biomass in both the soft and rocky areas. The site without debris had higher biomass in the soft area, and the site with nets had a higher density of benthic animals within the site with debris. In the rocky area. the site with debris had a higher biomass. Macrobenthos were affected by the type of deposited marine debris and the type of sediment substrate. This study provides a basis for future studies on the impact of debris on marine ecosystems and identified the benthos species affected by marine debris.

Dokdo Island’s diverse marine ecosystem requires long-term monitoring to understand the effects of rapid environmental changes, such as global warming, on macrobenthos species and communities. Current studies are often short-term and limited, highlighting the need for extended research to predict future changes to ecosystems. This study analyzed the environmental variables influencing macrobenthos through long-term monitoring. In total, 511 species (spp./23.4 m²) were identified with an abundance of 1709.9 individuals/m² and a diversity of 2.9. Since 2020, there has been a decline in both the number of species and diversity, attributed to changes in sediment composition, particularly an increase in gravel and sand. The dominant species include the crustacean Abludomelita denticulata (17.6%), the polychaete Haplosyllis spongiphila (6.8%), the bivalve Glycymeris munda (5.6%), the polychaete Opisthodonta uraga (5.3%), and the bivalve Limatula japonica (3.8%). The macrobenthos community differs each year, as the dominant species G. munda has decreased in abundance since 2022 and L. japonica since 2021. Depth and gravel sediment strongly correlated with community variation. Site-specific analysis also showed significant differences, with depth, bottom temperature, and sediment composition as the influencing factors. These species thrive in cold water but their abundance declines with an increase in temperature. Continuous long-term monitoring is essential to understand and protect the Dokdo ecosystem amid rapid environmental changes. Long-term monitoring studies have revealed more species than have short-term studies, showing annual and site-specific environmental changes, including sediment erosion and bottom temperature increases. These changes have affected macrobenthos diversity, abundance, and community composition, necessitating ongoing research to determine the persistence of these trends and to protect the ecosystem.

The increasing amount of marine plastic debris (MPD) poses risks of ingestion, entanglement, and transport of alien species. A new ecosystem called the “plastisphere” is currently being studied, but relevant research on it is limited. In this study, we analyzed the frequency of appearance of macroinvertebrate species on MPD. Macroinvertebrates attached to MPD were collected once every three months from March to December 2021 in eight regions. MPD in the form of aquaculture and fishing gear was detected most frequently during the study. In total, two phyla, 14 orders, 19 families, and 41 species of attached macroinvertebrates were detected during the study. There were more attached macroinvertebrate species, and they were more frequent, on fishing/aquaculture MPD (sea origin) than packaging MPD (land origin). Most fishing/aquaculture MPD is made of softer or rougher materials than packaging MPD and has a longer exposure time in the sea. In particular, the alien species Mytilus galloprovincialis was found on all longer-exposure MPD. These findings suggest that the macroinvertebrates attached to MPD are affected by the duration of exposure to the water and the characteristics of the MPD material. Therefore, in the future, fishing/aquaculture MPD could be used as an indicator for monitoring MPD-attached organisms.