Hyeon Ho Shin

Reconstruction of historical nutrient levels in Korean and Japanese coastal areas based on dinoflagellate cyst assemblages.

Dinoflagellate cysts acquired from sediment cores were analyzed in order to reconstruct historical nutrient levels in Gamak Bay, Korea and Ariake Bay, Japan. Dinoflagellate cyst assemblages in Gamak Bay were characterized by high proportions of heterotrophic cysts such as Brigantedinium spp., Protoperidinium americanum and Polykrikos cysts, which suggested that nutrients levels may have already been high before 1970s, and then increased further to the hypertrophic conditions of the 1990s. In contrast, dinoflagellate cyst assemblages in Ariake Bay were characterized by high relative abundances of Lingulodinium machaerophorum and Spiniferites spp., which suggested that nutrient levels in Ariake Bay had increased gradually since the mid 1960s, and may have been significantly enhanced by the mid 1980s. Dinoflagellate cyst assemblages reflecting environmental changes in the two bays are contrasting, perhaps due to different nutrient enrichment mechanisms. This suggests that the indicators of nutrient levels encoded in dinoflagellate cyst assemblages may exhibit site-specific information.

Sedimentary records of metal contamination and eutrophication in Jinhae-Masan Bay, Korea

Historical environmental pollution in a semi-enclosed coastal bay was investigated using high-resolution sedimentary records for C(org), N(tot), CaCO(3,) δ(13)C, and δ(15)N signatures, and trace metals. A temporal increase in organic matter might have been attributable to enhanced primary marine productivity, presumably caused by increased anthropogenic nutrient inputs in the semi-enclosed, eutrophic system. Metal accumulation occurred in three stages: a preindustrial stage before the 1930s with natural concentrations of metals, an industrialization stage (1940s-1970s) with the highest concentrations, and a postindustrial stage (post 1970s) with stable or decreasing concentrations. However, Hg exhibited a different accumulation history, with concentrations increasing in the early 1900s and accelerating after the 1920s, probably in response to coal burning.

Toxicological impact assessment of heavy metal contamination on macrobenthic communities in southern coastal sediments of Korea

In the heavily industrialized Masan Bay of southern coast, Korea, the potential harmful effects of heavy metals (Cd, Co, Cu, Ni, Pb, Sn, Zn, and Hg) were evaluated in terms of the pollution load index (PLI) and ecological risk assessment index (ERI) methods, and the results obtained were considered alongside the health of the macrobenthic fauna communities. The results revealed that the bay sediments, especially in the inner bay and the outfall area of a sewage treatment plant, are exposed to moderate to serious levels of metal pollution. Hg and Cd contributed the most to the potential toxicity response indices in sediments recently deposited in the bay. The potential ecological risk assessment of heavy metals in the bay was highlighted by the use of the benthic biological pollution index (BPI), suggesting that the ERI is a useful toxicity response index, which can quantify the overall ecological risk level to a target environment.

Identification of the resting cyst of Cochlodinium polykrikoides Margalef (Dinophyceae, Gymnodiniales) in Korean coastal sediments

This study provides the first morphological features of resting cysts of Cochlodinium polykrikoides collected from Korean coastal sediments. Evidence for the existence of resting cysts of C. polykrikoides is based on the morphological and molecular phylogenetic data of the germinated cells and a resting cyst. The morphology of the resting cysts differed from that reported previously in sediments and culture experiments. The distinct feature is that the cyst body was covered by the reticulate ornaments and spines.

The First Appearance of Toxic Dinoflagellate Alexandrium tamarense (Gonyaulacales, Dinophyceae) Responsible for the PSP Contaminations in Gamak Bay, Korea

In Gamak Bay, Paralytic Shellfish Poisoning (PSP) was first detected from seafoods in 2003, however the toxin source is unknown yet. In this study, we report potential PSP producers of toxic dinoflagellates, describing morphology and abundance of cysts isolated from surface sediment of Gamak Bay. The most abundant type in these cysts was characterized with ellipsoidal and transparent wall identical to Alexandrium catenella and/or A. tamarense. Germination experiment of the cysts revealed that all motile cells germinated were morphologically identified as A. tamarense. This result suggests that A. tamarense may relate to PSP contaminations in Gamak Bay. Moreover, bottom water temperature in Gamak Bay is favorable for germination of A. tamarense cysts. Further studies are required to carry out the PSP monitoring for preventing the risk of PSP events that may outbreak in future at Gamak Bay.

Algicidal Effects of a Newly Developed Thiazolidinedione Derivative, TD49, on Dinoflagellate Akashiwo sanguinea

Abstract : To evaluate the algicidal impact of a newly developed algicide thiazolidinedione derivative,TD49, on dinophyceae Akashiwo sanguinea in aquatic ecosystems, tentative culture experiments for thetarget species were conducted in small (SS), middle (MS), and large scale (LS) culture vessels. When TD49was introduced at the final concentration of 2 µM in SS and MS, as well as 1 µM in LS, the abundance of A.sanguinea decreased significantly in all the treatments. On the other hand, total phytoplankton abundance,except A. sanguinea in the TD49 treatments, gradually increased with culture time, which implies that a celldestruction of A. sanguinea by TD49 is a major cause of the population growth by other phytoplanktonspecies. Also, A. sanguinea was easily destroyed, which was likely to be a source of extracellularsubstances. In particular, a pH decrease was significant in the treatments than in the control, which indicatesthat the water in the treatments has been acidified, due to an increase in the heterotrophic metabolisms ofbacteria and degradation of A. sanguinea cells. Our results indicate that the TD49 substance is the potentialagents for the control of A. sanguinea in the enclosed and eutrophic water bodies.Key words :Akashiwo sanguinea, algicidal effect, thiazolidinedione, ecosystem*Corresponding author. E-mail : yokim@kordi.re.kr

Morphology and phylogeny of a new woloszynskioid dinoflagellate Tovellia paldangensis sp. nov. (Dinophyceae)

Abstract: The genus Tovellia contains approximately eight described species. A new species, Tovellia paldangensis sp. nov. was observed by incubation of a cyst from sediment collected in the Paldang Dam Lake in Korea. The vegetative cells of this new species were 20.0–27.0 μm long, 18.0–23.0 μm wide, and 17.0–20.5 μm thick. The cingulum was displaced by one cingulum width, the nucleus was located in the posterior part of the cell, and the chloroplasts were numerous and in yellow-green in color. A prominent red body was present on each side of the cingulum. The amphiesma had numerous thin polygonal plates that were arranged in three to four latitudinal series on the epicone and in two to three series on the hypocone. A narrow apical line of plates (ALP) extended over the anterior part of the cell, approximately in a 3/4 of the ventral side and 1/4 of the dorsal side of the epicone. The antapical plate was usually hexagonal. T. paldangensis was clearly differentiated from the other species of Tovellia by the morphology of its vegetative cell (two red bodies, and the ALP lines on each side separated by a row of four to five elongate plates) and the resting cyst (typically covered with numerous short solid spines). Phylogenetic analysis based on partial large subunit ribosomal RNA gene sequences indicated that T. paldangensis was most closely related to T. coronata, T. sanguinea, and T. aveirensis.

Brigantedinium majusculum is the cyst of Protoperidinium sinuosum (Protoperidiniaceae, Dinophyceae)

Abstract: Two morphologically distinct species, Brigantedinium majusculum and Trinovantedinium applanatum, have been suggested as a cyst stage of Protoperidinium pentagonum; however, the cyst–theca relationships are still virtually undefined. In this study, we re-examined the motile stage of B. majusculum via thecal plate analysis together with a molecular phylogenetic analysis based on partial large-subunit ribosomal DNA gene sequences. The morphological features of motile cells germinated from B. majusculum were identical to those of Pr. sinuosum, and the molecular phylogenetic analysis showed that the germinated cells and B. majusculum are closely related to Pr. pentagonum and Pr. latissimum as a sister group. Additionally, high sequence divergences were observed between the germinated cells and B. majusculum as well as Pr. pentagonum and Pr. latissimum (18.0–19.5% according to P-values and 20.7–22.9% according to Kimura two-parameter values). On the basis of these results, our study indicates that B. majusculum should be accepted as the cyst of Pr. sinuosum.

In Situ Hatching Success of Calanoid Copepod Eggs in Hypoxic Sediments of a Coastal Bay

ABSTRACT Choi, K-H.; Jang, M-C.; Shin, H.H.; Lee, W-J., and Shin, K., 2016. In situ hatching success of calanoid copepod eggs in hypoxic sediments of a coastal bay. Hypoxia can have adverse effects on recruitment of marine copepods via its effects on egg hatching and survival of nauplii. This study investigated the effects of hypoxia on in situ hatching success of calanoid copepods in Gamak Bay, Korea, a shallow (9-m) microtidal coastal bay with long water residence times exceeding a month. Plankton emergence trap/chambers were placed into seafloor–surface sediments in July at a hypoxic site (mean = 0.6 mL L−1) in the inner part of the bay and at a normoxic site in the mid bay. Nauplii that hatched and left the sediment were collected daily for 12 days, and the top 1 cm of sediment was preserved at the end of incubation. The number of eggs in the sediment was >3 × 105 eggs m−2 at the hypoxic site, about six times that at the normoxic site. Most of the eggs appeared to be subitaneous. Egg-hatching rate in the hypoxic site, however, was only 4% of that at the normoxic site, where 57% of the eggs present hatched. Cumulative numbers of eggs hatching into the hypoxic chambers were about half the numbers hatching into the normoxic chambers. The pH level in the sediment was 7.1 to 7.3 at the hypoxic site, slightly lower than in the normoxic sediment (pH > 7.5). That difference seemed to have little effect on egg hatching. High sulfide concentration at the hypoxic site (>300 μM), combined with low dissolved oxygen in summer were likely responsible for the depressed egg hatching. However, the cumulative number of eggs that hatched in the hypoxic chambers was still about half of that in the normoxic chambers. Thus, it appears that the hypoxic site might still be a significant source of juveniles for the next generation of the copepods.

Distribution of dinoflagellate cysts in Yellow Sea sediments

To investigate the distribution, abundance, and species composition of dinoflagellate cysts in the Yellow Sea, surface sediment samples were collected at 37 sites, including the Korean dump site. Twenty-one dinoflagellate cyst taxa were identified, with the assemblages dominated mainly by Spiniferites bulloideus, Operculodinium centrocarpum, and cyst of Alexandrium catenella/tamarense type. A high frequency of O. centrocarpum in the Yellow Sea was observed for the first time, and it is likely that this can be attributed to the dynamics of the Yellow Sea Cold Water Mass and the Changjiang (Yangtze) River runoff. Total cyst concentrations ranged from 23 to 48 442 cysts/g dry weight, and high cyst concentrations were recorded adjacent to the dumping site. This result suggests that anthropogenic activities such as ocean dumping stimulate the growth of dinoflagellates in the Yellow Sea, which in turn leads to high levels of dinoflagellate cyst production.