Search

The dinoflagellate genus Scrippsiella is a common member of phytoplankton and their cysts are also frequently reported in coastal sediments worldwide. However, the diversity of Scrippsiella in Korean waters has not been fully investigated. Here, several isolates of Scrippsiella precaria collected from Korean waters and germinated from resting cysts were examined using light and scanning electron microscopy. The resting cysts were characterized by pointed calcareous spines and one or two red accumulation bodies, and the archeopyle was mesoepicystal, representing the loss of 2–4′ and 1–3a paraplates. Rounded resting cysts were found in culture, and an increase in spine length was observed until 8 days of development. Korean isolates of S. precaria had the plate formula of Po, X, 4′, 3a, 7″, 6C, 4S, 5‴, 2⁗. There were differences in the cell size and location of the red body between Korean isolates and previously described cells of S. precaria. In addition, the Korean isolates of S. precaria had two types of the 5″ plate that either contacted the 2a plate or not. Molecular phylogeny based on internal transcribed spacer (ITS) and large subunit (LSU) rDNA sequences revealed that the Korean isolates were nested within the subclade of PRE (S. precaria and related species) in the clade of Scrippsiella sensu lato, and that the PRE subclade had two ribotypes: ribotype 1 consisting of the isolates from Korea, China, and Australia, and ribotype 2 consisting of the isolates from Italy and Greece. Lineages between isolates of ribotype 1 were likely to be related to the dispersal by ocean currents and ballast waters from international shipping, and the two types of spine shapes and locations of the 5″ plates may be a distinct feature for ribotype 1.

For the better understanding of long-term variations of water quality in Jinhae Bay after establishment of special law, we analyzed the archive data monitored in Jinhae Bay during the last 17 years (1997-2013). And change on fish catch due to the variations of water quality was investigated. A marked decrease in the number of red tide occurrence is due to the effectiveness of the law and sewage treatment plant that has targeted the reduction of COD in the effluent water since early 2000. Although the improvement of water quality, increase in fishery production was not observed in Jinhae Bay. For the recovery of fishery production, processes for restoration of entire ecosystem such as restoration of artificial intertidal flat and seaweed bed and remediation of organic-rich sea bed should be accompanied with improvement of water quality.

有毒渦鞭毛藻 Alexandrium tamarense 広島湾株による溶有態有機リン(DOP)の取り込みと排出に関して、広島湾汲み置き海水を用いたパッチ培養と半連続培養による実験を行った。バッチ培養では、培養液中のリン酸塩濃度約2μMを境に、それ以下で有意な正味のDOP取り込み、それ以上で正味の排出が見られた。半連続培養では、A. tamarense は希釈率が大きく、培地中の十分なリン酸塩を利用して活発に増殖している場合にDOPの正味の排出を示した。以上のことから、予備的実験結果ではあるが、A. tamarense 広島湾株はリン酸塩濃度が低い場合にはDOPを利用し、リン酸塩濃度が高くて活発に増殖している場合にはDOPを排出することが示唆された。, Capability of utilization and excretion of dissolved organic phosphorus (DOP) by the toxic dinoflagellate Alexandrium tamarense (Hiroshima Bay strain) was investigated with both batch and semi-continuous cultures using natural aged-seawater from Hiroshima Bay. In the batch cultures, significant net DOP uptake was detected in phosphate concentrations below 2μM, while net DOP excretion was observed above this concentration. The semi-continuous culture showed that A. tamarense excretes DOP at high dilution rates. At these rates, this organism grows fast by utilizing sufficient phosphate in the medium. These experiments, although preliminary, suggest that A. tamareme (Hiroshima Bay strain) can utilize DOP of natural seawaters under a condition of low phosphate concentration and excretes DOP under a condition of high phosphate concentration.