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 probability of copepod entanglement in microfibers in a laboratory experiment. This experiment was inspired by an accidental observation of entangled copepods with microfibers during isolating copepods for grazing experiments. The exposure of microfibers to copepods was designed by applying conditions similar to environmentally relevant concentrations of microfibers to zooplankton in the Yellow Sea as well as highly elevated concentrations of microfibers compared to the previously reported maximum natural concentration. Copepod entanglement in microfibers was reproduced in laboratory. The entanglement was not observed in the condition which simulated the environmental scenario of copepods outnumbering microfibers observed in the Yellow Sea, while it occurred inconsistently in the conditions of the maximum and 10-fold maximum natural concentrations of microfibers. However, consistent entanglement of copepods by microfibers was found in the 100-fold maximum environmental concentration of microfibers. These results suggest that copepod entanglement by microfibers can happen accidentally under the maximum natural concentration of microfibers occurring in the marine environment; however, copepods are likely to be entangled in microfibers consistently if copepods encounter highly enhanced concentration of microfibers.

The dispersal of organisms in an isolated environment of a hydrothermal vent remains unclear. Here, we provide direct evidence that meroplanktonic larvae may migrate thousands of meters above the ocean floor. The morphological quantitative measurements of mesozooplankton were conducted in the Onnuri Vent Field (OVF), the Solitaire Fields (SF), and the reference site (ref-site). Only one species of bivalve larva that appeared at the OVF and the ref-site (0–200 m) was similar to Bathymodiolus spp. Sixteen species of gastropod larvae were distinguished, among which, species 1–4, 6, and 13 had holoplanktonic features (Atlanta, Oxygrus, and Limacina), whereas species 5, 7–12, and 14–16 had meroplanktonic features. Species 5, 11, and 12 appeared only at the OVF, 9 and 10 appeared only in the SF, 14–16 appeared only at the ref-site, and species 7 and 8 appeared in all surveyed stations. The species 5, 8, 12, 14, and 15 have morphological features similar to Vetulonia spp., and species 7 was similar to Lepetodrilidae; species 9–11 and 16 were similar to Phymorphynchus protoconchs. The morphologically distinguished mollusk larvae in the upper layers of the water column (0–200 m) indicate that larvae associated with deep-sea hydrothermal vents may disperse approximately 2000 m above the vents.