Patterns of Gene Expression Variation across Body Parts of the Hydrothermal Vent Shrimp Nautilocaris saintlaurentae

Ocean Science Journal - Since deep-sea hydrothermal vents have been targeted for mining mineral resources, concerns about the potential impacts of mining on vent ecosystems have gradually...     

High-frequency acoustic backscattering characteristics for acoustic detection of the red tide species Akashiwo sanguinea and Alexandrium affine

Harmful algal blooms (HABs), caused by the overgrowth of certain phytoplankton species, have negative effects on marine environments and coastal fisheries. In addition to cell-counting methods using phytoplankton nets, a hydroacoustic technique based on acoustic backscattering has been proposed for the detection of phytoplankton blooms. However, little is known of the acoustic properties of HAB species. In this study, as essential data to support this technique, we measured the acoustic properties of two HAB species, Akashiwo sanguinea and Alexandrium affine, which occur in the South Sea off the coast of Korea. Due to the small size of the target, we used ultrasound for the measurements. Experiments were conducted under laboratory and field conditions. In the laboratory experiment, the acoustic signal received from each species was directly proportional to the cell abundance. We derived a relationship between the cell abundance and acoustic signal received for each species. The measured signals were compared to predictions of a fluid sphere scattering model. When A. sanguinea blooms appeared at an abundance greater than 3 500 cells/mL, the acoustic signals varied with cell abundance, showing a good correlation. These results confirm that acoustic measurements can be used to detect HAB species.     

Application of a Conceptual Ecological Model to Predict the Effects of Sand Mining around Chilsan Island Group in the West Coast of Korea

Chilsan Island Group, located on the west coast of South Korea, has been recognized as a critical breeding and nursery ground for endangered seabirds because food is abundant and human activity is low. Chilsan Island Group has been under protection as a Natural Monument (Article no. 389) since 1997, but attempts were made in 2004 to exploit the coastal sands around the islands. A conceptual ecological model (CEM) was employed with energy flow diagram (EFD) to predict the effects of sand mining on the islands’ ecosystem. The results showed that sand mining activities caused long-term damage to benthic ecosystems and threatened seabird communities by reducing fish populations throughout the food web. The changes in energy flow in the ecosystem due to sand mining operations predict that reduction in secondary production of benthic animal communities might reduce energy transfer to humans and seabirds by 30%. Different ranges of uncertainty provided by the Monte Carlo simulation lead to the conclusion that sand mining could bring about undesirable consequences. One concern is that such negative consequences would have a much more severe impact on seabirds than humans because seabirds cannot compete effectively against humans for the limited food sources. In this study, the complex interrelationships between ecosystem members were simplified and a CEM was established to clearly identify which elements would be affected. The CEM with EFD was found to be helpful in promoting communication between stakeholders, and it is expected to be widely used as a decisionmaking tool by public officials.     

Reproduction of the giant jellyfish, <Emphasis Type="Italic">Nemopilema nomurai</Emphasis> (Scyphozoa: Rhizostomeae), in 2006–2008 as peripherally-transported populations

This study investigated the sexual maturation process, release of spermatozoa or eggs and oocyte diameter of the rhizostomid medusae Nemopilema nomurai using samples collected from August 2006 to June 2008 from the waters around Korea and Japan, including peripheral areas outside the species’ usual habitat. Immature medusae were observed from June to October only in the western sector of the study area. The onset of spermatozoa and egg release occurred in September and October, respectively, and peaked in December and January. Medusae migrated eastward from source areas with the Tsushima Warm Current, where they formed gametes and spawned. Peak position and maximum oocyte diameter increased as the gonads developed according to the size-frequency distribution of oocytes. No fertilized eggs or embryos were found in the gonads. The correlation was analyzed with bell diameter, maximum oocyte diameter, sampling date, surface water temperature and gonad color to estimate which environmental factors and maturation indices were related to the maturation stage of females. Maturation stage correlated well with maximum oocyte diameter, which correlated negatively with surface water temperature. There was no significant correlation between bell diameter and maturation stage. Therefore, bell diameter was inappropriate for determining maturation index. Sex could not be distinguished clearly by gonad color. However, light pink gonads were more prevalent in males and various deep colors such as orange and brown were more frequent in female medusae.     

Mechanism of tremolite carbonation

The direct aqueous carbonation of fibrous tremolite was investigated by TEM, powder XRD, and FT-IR to elucidate the transformation mechanism of tremolite into calcite. The TEM study revealed that tremolite dissolves along the weak cleavage on (1 0 0) and (1 1 0) and the cleavage fragment fibers. The preferential release of Ca, relative to Si or Mg, into the solution resulted in the crystallization of compositionally homogeneous calcite and in the concurrent formation of proto-saponite. X-ray diffraction analysis revealed that the amount of product calcite increased rapidly within 15 min. Subsequently, after a 5 h carbonation period, it increased slowly to about 60%. The product calcite is euhedral. In contrast, the unreacted tremolite grains retain the original crystal structure even after prolonged carbonation. The morphological modification of tremolite from fibrous to round may have important implications for the elimination of its toxicity.     

Effects of ocean acidification driven by elevated CO<Subscript>2</Subscript> on larval shell growth and abnormal rates of the venerid clam, <Emphasis Type="Italic">Mactra veneriformis</Emphasis>

The venerid clam (Mactra veneriformis Reeve 1854) is one of the main cultured bivalve species in intertidal and shallow subtidal ecosystems along the west coast of Korea. To understand the effects of ocean acidification on the early life stages of Korean clams, we investigated shell growth and abnormality rates and types in the D-shaped, umbonate veliger, and pediveliger stages of the venerid clam M. veneriformis during exposure to elevated seawater pCO₂. In particular, we examined abnormal types of larval shell morphology categorized as shell deformations, shell distortions, and shell fissures. Specimens were incubated in seawater equilibrated with bubbled CO₂-enriched air at (400±25)×10^-6 (ambient control), (800±25)×10^-6 (high pCO₂), or (1 200±28)×10^-6 (extremely high pCO₂), the atmospheric CO₂ concentrations predicted for the years 2014, 2084, and 2154 (70-year intervals; two human generations), respectively, in the Representative Concentration Pathway (RCP) 8.5 scenario. The mean shell lengths of larvae were significantly decreased in the high and extremely high pCO₂ groups compared with the ambient control groups. Furthermore, under high and extremely high pCO₂ conditions, the cultures exhibited significantly increased abundances of abnormal larvae and increased severity of abnormalities compared with the ambient control. In the umbonate veliger stage of the experimental larvae, the most common abnormalities were shell deformations, distortions, and fissures; on the other hand, convex hinges and mantle protuberances were absent. These results suggest that elevated CO₂ exerts an additional burden on the health of M. veneriformis larvae by impairing early development.     

Deriving a practical form of IDF formula using transformed rainfall intensities

A general form of formula is presented for the rainfall Intensity–Duration–Frequency (IDF) relationship. This formula is derived from the nearly normal probability distribution function of transformed intensities. In order to transform the raw intensities, a correcting non‐constant spread technique, the Kruskal–Wallis statistic, and the Box–Cox transformation are adopted. These transformations enable to express a simpler model for the IDF formula that agrees well with traditional IDF relationships. Since the proposed method allows the estimation of any percentile value of intensities with a single equation, the intensity percentile at arbitrary duration can be generated easily. The validity of the formula derived by means of the proposed method is assessed using data from major weather stations in Korea. The results show that the percentile intensities produced using the proposed method are in good agreement with those of traditional frequency analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

Distribution of small plastic debris in cross-section and high strandline on Heungnam beach, South Korea

The spatial distribution of small plastic debris on Heungnam beach in February 2011 was investigated. The abundances of small plastic debris over 2 mm in size along the high strandline and cross-sectional line of the beach were determined. The mean abundances of small plastics were 976 ± 405 particles/m² at the high strandline in the upper tidal zone along the shoreline and 473 ± 866 particles/m² at the cross-section perpendicular to the shoreline. Specifically, styrofoam (expanded polystyrene) spherules accounted for 90.7% of the total plastic abundance in the high strandline and 96.3% in the cross-section. The spatial distribution patterns of small plastic debris differed between the high strandline and cross-sectional line. The cross-sectional distribution of small plastic abundance differed among plastic types, indicating that representative sampling of small plastic debris on a beach is necessary.     

Preliminary Results of the Ground-Based Orographic Snow Enhancement Experiment for the Easterly Cold Fog （Cloud） at Daegwallyeong during the 2006 Winter

The snow enhancement experiments, carried out by injecting AgI and water vapor into orographically enhanced clouds (fog), have been conducted to confirm Li and Pitter’s forced condensation process in a natural situation. Nine ground-based experiments have been conducted at Daegwallyeong in the Taebaek Mountains for the easterly foggy days from January–February 2006. We then obtained the optimized condi- tions for the Daegwallyeong region as follows: the small seeding rate (1.04 g min-1) of AgI for the easte...