This study investigates the resonated diurnal impact of the surface wind forcing from several atmospheric wind products, including CCMP (Cross-Calibrated Multi-Platform), ERA Interim, NCEP-2 (NCEP-DOE AMIP-II Reanalysis), MERRA (Modern-Era Retrospective analysis for Research and Application), NARR (Northern American Regional Reanalysis) and NAM (North American Mesoscale Forecast System), on the wind-driven near-inertial ocean motions in the northern Gulf of Mexico by numerical simulation, and in comparison, with NDBC buoy surface observed winds. Our analyses show that the near-inertial wind power input, which can affect vertical mixing in the water column, is closely associated with the variability of land-sea breeze by various wind products. In comparison with buoy observations in the northern Gulf of Mexico, the MERRA has the worst land-sea breeze representation, while the NCEP2 and CCMP, which are chosen to represent the coarsest and medium–high horizontal resolution, have the best performance. We further show that by comparison of the buoy data, that the near-inertial wind power input derived from all the wind products is underestimated by 30–50% approximately.

A correction to this paper has been published: https://doi.org/10.1007/s12601-021-00025-z

The paper presents the evolution of the morphological structures of a fine sand bed subjected to a turbulent flow field associated with the propagation of unidirectional surface waves. In particular, starting from a flatbed, the instability of the sediment grains from the ripple formation initiation state to the quasi-equilibrium state was observed in a wave flume. During the rolling grain ripple formation stages, new ripples appeared at each trough due to the doubling transition phenomenon and the ripples migrated soon after their formation. Observations showed that the wavelength of the bed forms that appeared during the rolling grain stage was about half of that observed at the quasi-equilibrium stage. Further, the suspended sediment concentration above the ripple bed varied with the number of wave cycles and at different vertical positions of the water column—as evidenced from the present experiments. The power spectral density of the turbulent velocity fluctuations showed that the transition of the rolling grain to vortex ripples occurred between 400 and 500 cycles with signatures of distinct reduction of near-bed spectral energy at the quasi-equilibrium state. It is evident from the stress ellipsoid that until the transition from rolling grain ripples to vortex ripples occurred, the ejection and the sweeping turbulent bursting structures took the leading role in the transportation of sediment. Thereafter, gradually the outward- and inward-interacting turbulent bursting structures provided the major contribution to the Reynolds shear stresses during the different evolution stages of vortex ripples and also at the quasi-equilibrium stage.

Thamnaconus modestus is a commercially important species that is widely distributed in the Northwest Pacific region. To investigate the genetic diversity, demographic history, and population structure, 84 individuals were collected from two locations in Korea (Geomundo and Jumunjin) and one location in Japan (Wakasa Bay). Analysis of the mitochondrial DNA control region sequence of 373 base pairs from the 84 individuals revealed 39 haplotypes with 50 polymorphic sites. The haplotype diversity and nucleotide diversity of different populations ranged from 0.973 (0.018) to 0.981 (0.013) and from 0.020 (0.011) to 0.021 (0.011), respectively. Phylogenetic analysis revealed three distinct clades of which two were large (clade 1 and clade 2) and one was small clade (clade 3). However, there was no significant geographical clustering of the haplotypes according to the sampling locality. Demographic analysis suggested that both clades experienced Late Pleistocene population expansion. The pairwise FST and AMOVA analysis were insignificant among the populations investigated. This indicated high gene flow among the populations of Korea and Japan. The dispersal capacity of the larvae and juveniles by ocean currents and migration of adult individuals could explain the genetic homogeneity. Insufficient time to accumulate genetic variation might be another reason for the lack of genetic structure.

As planktonic ciliates have been recognized as important players in marine microbial food webs, relevant studies have been conducted in the western coastal waters of the Yellow Sea. However, little is known about ciliate distributions from the eastern coast of the Yellow Sea near the Korean Peninsula. A spring cruise in April 2019 was carried out to investigate vertical and horizontal distributions of ciliate plankton at 18 stations that form three zonal sections in the eastern area. Biological (picoplankton, nanophytoplankton, and mesozooplankton) and hydrological (water temperature and salinity) environments were also analyzed to understand relationships between the ciliate distributions and the environments. High abundance (ca. 2400 cells L−1) of a large ciliate species, Laboea strobila, was observed at the surface water of Stn. 37–5. Abundance peak of large (> 50 μm) ciliates coincided with the peak of mesozooplankton abundance. Spatial distribution of the large ciliates was associated with nanophytoplankton distribution while a smaller (20–50 μm) ciliate group was associated with picoplankton distribution. Therefore, the spring distribution of ciliate plankton in the southeastern coast of the Yellow Sea indicates that food size for the ciliates is one of the important factors controlling ciliate compositions as well as their abundances. Further investigations need to be carried out to understand seasonal differences of ciliate distributions in the eastern Yellow Sea.

Clove oil (CO) is an effective anesthetic. Many hatcheries and research studies use clove oil to immobilize fish for artificial reproduction and surgery to suppress their sensory systems during invasive procedures. In this study, olive flounder Paralichthys olivaceus were exposed to two distinct CO concentrations (25 µL/L and 50 µL/L) under white fluorescent lights and green light emitting diodes (LEDs), and the effects of CO on their stress response were investigated up to 42 h after anesthesia. The stress parameters evaluated were the prepro-melanin concentrating hormone (pMCH) and corticotropin-releasing hormone (CRH) mRNA expression levels in the brain and plasma cortisol. The results showed that anesthesia was rapidly induced in fish exposed to higher anesthetic doses and white light. However, these fish took a longer time to recover when compared with fish exposed to green light. Additionally, green light initially increased the pMCH expression, before decreasing after 14 h. The CRH and cortisol levels were measured under the same parameters; these values were lower in fish exposed to green light than those exposed to white fluorescent light. Additionally, the pMCH, CRH, and cortisol levels increased when exposed to higher CO concentrations. However, the mRNA expression levels and activity showed initial peaks, followed by a decline. Our results suggest that irradiation with green light after anesthesia reduces cortisol levels (the final product of the stress index) suggesting that this is an effective procedure to quickly recover homeostasis after anesthesia-induced stress.

As a suspension feeder, Manila clam Ruditapes philippinarum (A. Adams and Reeve 1850) plays a crucial role in the coastal soft bottom ecosystem in the temperate region, linking the benthic primary production to the upper trophic level. Manila clam density on tidal flats on the west coast of Korea has been declining for the past decades, and infection by the protozoan parasite Perkinsus olseni (Lester and Davis 1981) is one of the major causes for the decline. Recent studies carried out in Japan revealed that P. olseni induces mortalities of the juveniles in their natural habitats, which may lead to the recruitment failure and subsequent decline in the clam population. In this study, we surveyed P. olseni infection in juvenile Manila clam occurring on two tidal flats on the Taean coast. Ray’s fluid thioglycollate medium assay (RFTM) revealed that P. olseni infection was not limited to the adult clams, and the juvenile and small-sized clams are also infected by P. olseni. As young as four-month-old juveniles from Jugyo tidal flat were infected by P. olseni, with the prevalence (i.e., percentage of the infected individuals) of 75.0% and the intensity of 7.77 × 105 cells g−1 wet tissue weight (WT). The adult Manila clams (SL > 30 mm) from Jugyo tidal flat showed a prevalence of 96.0%, and the intensity as 5.80 × 10 cells g−1 WT. The observed infection prevalence and intensity of the juvenile are somewhat comparable to those of the adult clams, suggesting that a high level of P. olseni infection in the juveniles may lead to mortality and a long term decline in the clam population density.