Temporal variation in appearace of moon jellyfish (Aureliα sp.) aggregation at surface layer in summertime Hokezu Bay during 2002-2005 were examined using the land-base video monitoring system. The existences of long- and short-term fluctuations in the appearance of the moon jellyfish aggregation were revealed. The long-term fluctuation was characterized by the appearance of the moon jellyfish aggregation in middle August and by vanishment in September-October, whereas the short-term fluctuation had periods of 10-15 days. Interannual variation of the short-term fluctuation well corresponded with that of kyucho, which was intrusion of warm surface water from the Pacific Ocean to the Bungo Channel. To examine the relationship between the short-term fluctuation and the kyucho, mooring and hydrographic observations were conducted in summertime Hokezu Bay of 2007. When the kyucho reached Hokezu Bay, the warm water flowed into the bay under surface pycnocline (thermocline). This warm water intrusion caused not only bay-scale water mass exchange but also transport of the moon jellyfish from the outside to the inside of the bay, and then the intruded moon jellyfish was considered to be passively aggregated at the surface layer. As a result of this, the short-term fluctuation with periods of 10-15days in the appearace of the moon jellyfish aggregation was considered to occur at the surface layer in summertime Hokezu Bay.

The increase of the atmospheric carbon dioxide (CO₂) concentration after the industrial revolution caused global climate change. During the last several decades, coral reef ecosys tems have been devastated by the mass-scale coral bleaching events caused by abnormally high seawater temperature in summer. In addition, increased atmospheric CO₂ dissolves in the ocean, acts as an acid and finally decreases the pH level of seawater. This phenomenon, known as ocean acidification, is now being considered as a future threat to the calcifying organisms in coral reef ecosystems. In this review, we summarize basic backgrounds of ocean acidification as well as its potential impacts on coral reef calcifiers. Together with the distinctive mechanisms of calcification among specific groups, we review the impacts of ocean acidification on major reef-builders such as scleractinian corals, calcareous red algae and reef-dwelling foraminifera. Finally, we point out some recently-recognized problems in acidified seawater experiments as well as the future direction of this research field.

This article summarizes the results of my study on the character吐zationand dynamics of chromophoric dissolved organic matter (CDOM) in the ocean based on both observational and experimental approaches. CDOM can be separated into bio-components (e.g., protain-like fluorophores) and humic-like substances. In regards to the bio-components in CDOM, like fluorophores were first suggested to derive from aromatic amino acids in DOM. Furthermore, using fluorescence properties and amino acid composition, chemical forms of amino acid-containing DOM in high molecular weight fractions were identified as long-chain peptides in surface waters and relatively small peptides in deep waters, respectively. In regards to the humic-like substances in CDOM, the spatial distribution of both quantitative and qualitative parameters of marine humic-like CDOM as well as apparent oxygen utiliza tion (AOU) indicated that marine humic-like CDOM is produced as organic matter is bio logically oxidized, and that this material is bio-refractory on centennial to millennium time scales.