Kouichi Ohwada

Impacts by heavy-oil spill from the Russian tanker Nakhodka on intertidal ecosystems: recovery of animal community.

The impact of a heavy-oil spill from the Nakhodka on an intertidal animal community, and the recovery process of animals from the damage were surveyed from the autumn of 1997 to the spring of 2001. The field study was carried out in the rocky coast of Imago-Ura Cove, located along the Sea of Japan, where clean-up operations for oil pollution had been conducted less intensely than in other polluted areas. We have examined individual number of each animal taxon by continuously placing a quadrat of 5 m width along the entire intertidal zone of the cove. A total of 76 invertebrate taxa including 57 species of mollusks, 10 species of crustaceans were observed during the survey. The number of taxa increased from 1998 to 1999 in areas where the initial oil pollution was intense. Total individual number of benthic animals continued to increase from 1998 to 2000 in the polluted areas. The impact of oil on benthic animals was different from species to species. Some species such as Cellana toreuma and Monodonta labio confusa increased rapidly after the oil spill, whereas other species such as Patelloida saccharina lanx and Septifer virgatus did not show any apparent temporal tendencies. Population size structure of P. saccharina lanx varied greatly among years, however that of M. labio confusa did not. For P. saccharina lanx, recruitment was unsuccessful in 1997, possibly due to the effect of oil pollution. These differences in responses to oil pollution among benthic animals are considered to be caused by the differences in habitat use, susceptibility to heavy-oil, life history and migration ability. The findings suggest that it took at least 2-3 years for the intertidal animal community to recover to its original level after the oil spill.

Study of the effect of water-soluble fractions of heavy-oil on coastal marine organisms using enclosed ecosystems, mesocosms

Mesocosm facilities composed of 4 experimental and 2 reservoir tanks (1.5 m in diameter, 3.0 m in depth and 5 tons in capacity) made of FRP plastics, were constructed in the concrete fish rearing pond in the Fisheries Laboratory, The University of Tokyo. The water-soluble fraction of Rank A heavy residual oil was formed by mixing 500 g of the oil with 10 l of seawater, which was introduced to the 5000 l-capacity tanks. Experimental Run 4 was conducted from May 31 to June 7, 2000. Oil concentrations in the tanks were 4.5 microg/l called LOW, and 13.5 microg/l, called HIGH tank. Bacterial growth rates very quickly accelerated in the HIGH tank just after the loading of oil which corresponded with a high increase of bacterial cells in the same tank after 2 days. Later, bacterial numbers in HIGH tank rapidly decreased, corresponding with the rapid increase of heterotrophic nano-flagellates and virus numbers on the same day. Sediment traps were deployed at the bottom of the experimental tanks, and were periodically retrieved. These samples were observed both under light microscope and epi-fluorescent microscope with UV-excitation. It was observed that the main components of the vertical flux were amorphous suspended matter, mostly originating from dead phytoplankton and living diatoms. It was further observed from the pictures that vertical transport of oil emulsions were probably conducted after adsorption to amorphous suspended matter and living diatoms, and were settling in the sediment traps at the bottom of the tanks. This means that the main force which drives the soluble fraction of oil into bottom sediment would be vertical flux of such amorphous suspended particles and phytoplankton. Further incubation of the samples revealed that the oil emulsions were degraded by the activity of autochtonous bacteria in the sediment in aerobic condition.

Reassessment of the taxonomic position of Vibrio iliopiscarius (Onarheim et al. 1994) and proposal for Photobacterium iliopiscarium comb. nov.

The phylogenetic position of Vibrio iliopiscarius was inferred by the maximum-likelihood, maximum-parsimony and neighbour-joining methods on the basis of almost complete 16S rRNA gene sequences. The results showed that this species falls into the same cluster as Photobacterium species and is clearly distinct from other Vibrio species. Its nearest phylogenetic neighbour is Photobacterium phosphoreum. From these results, it is concluded that V. iliopiscarius should be reclassified as Photobacterium iliopiscarium comb. nov., the type strain of which is PS1T (= ATCC 51760T).

Bioremediation of organically enriched sediment deposited below fish farms with artificially mass-cultured colonies of a deposit-feeding polychaete Capitella sp. I

For bioremediation of organically enriched sediment deposited below fish farms, the extremely high potential for population growth of a deposit-feeding polychaete, Capitella sp. I, in the organically enriched sediment, and the effect on decomposition of organic matter in the sediment, were examined. A mass-culturing technique was conducted for this species. Bioremediation experiments were conducted on the organically enriched sediment in a fish farm in Kusuura Bay, Japan in 2003–2006. Approximately 1.7 million individuals of the worms were placed on the sediment below one net pen in December 2003, 9.3 million individuals in November 2004, and 2.2 million individuals in November 2005. After the worms were spread on the sediment, they rapidly increased in number and reached the highest densities of approximately 134 000 inds/m2 in February 2004, 527 000 inds/m2 in March 2005 and 103 000 inds/m2 in January 2006. In the process of rapid population growth, the decomposition of the organic matter of the sediment was enhanced markedly. Our results demonstrate that the promotion of population growth by spreading cultured colonies of Capitella can enhance the decomposition rate of organic matter markedly in organically enriched sediment below fish farms. This method is promising for minimization of the negative effects of fish farms.

Microbial diversity in time and space

Introduction (R.R. Colwell). Scope of Microbial Diversity: Importance of the Diversity of Community Relations (H. Kawanabe). Evolution of Microbial Diversity: From Strains to Domains: Measuring the Degree of Phylogenetic Diversity among Prokaryotic Species and as yet Uncultured Strains (E. Stackebrandt). Diversity of Viruses (M. Hatanaka). The Evolution of Fungal Diversity: Past, Present, and Future (A.Y. Rossman). Mutual Interaction and Microbial Diversity: Symbiosis in Termites (I. Yamaoka). The Role of Microorganisms in Tritophic Interaction Systems Consisting of Plants, Herbivores, and Carnivores (M. Dicke). Sensitivity Analysis in Microbial Communities (H. Nakajima, Z. Kawabata). Microbial Diversity in Environments: Adaptation of Soybean Bradyrhizobia to the Brazilian Edaphic Savanna (M.C.P. Neves et al.). Viruses and DNA in Marine Environments (J.H. Paul). Diversity of Naturallyoccurring Prokaryotes: A Beginning (E.F. DeLong). Workshop Microbial Diversity and Cycling of Bioelements: Image Analysis of Bacterial Cell Size Diversity (K. Kato). Microbial Diversity and Cycling of Nitrogen in Soil Ecosystem (T. Ueda, K. Inubushi). 6 additional articles. Index.

Increase in Alphaproteobacteria in association with a polychaete, Capitella sp. I, in the organically enriched sediment

We conducted bioremediation experiments on the organically enriched sediment on the sea floor just below a fish farm, introducing artificially mass-cultured colonies of deposit-feeding polychaete, Capitella sp. I. To clarify the association between the Capitella and bacteria on the efficient decomposition of the organic matter in the sediment in the experiments, we tried to identify the bacteria that increased in the microbial community in the sediment with dense patches of the Capitella. The relationship between TOC and quinone content of the sediment as an indicator of the bacterial abundance was not clear, while a significant positive correlation was found between Capitella biomass and quinone content of the sediment. In particular, ubiquinone-10, which is present in members of the class Alphaproteobacteria, increased in the sediment with dense patches of the Capitella. We performed denaturing gradient gel electrophoresis (DGGE) analyses to identify the alphaproteobacterial species in the sediment with dense patches of the worm, using two DGGE fragments obtained from the sediment samples and one fragment from the worm body. The sequences of these DGGE fragments were closely related to the specific members of the Roseobacter clade. In the associated system with the Capitella and the bacteria in the organically enriched sediment, the decomposition of the organic matter may proceed rapidly. It is very likely that the Capitella works as a promoter of bacteria in the organically enriched sediment, and feeds the increased bacteria as one of the main foods, while the bacteria decompose the organic matter in the sediment with the assistance of the Capitella.

Coupling between the respiratory chain and the luminescent system of Vibrio harveyi

Effects of monovalent cations on luminescence and respiratory activity were studied in the marine luminous bacterium Vibrio harveyi. Maximum oxygen uptake was observed in the presence of Na+over the pH range tested (6.5–8.5). At alkaline pH, effects of monovalent cation on luminescence were similar to those on the oxygen uptake. Although KCN addition caused a marked increase in luminescence, the enhanced luminescence with Na+was still greater than that with Li+. However, at acidic pH, K+increases luminescence more than Na+does. These results indicate that there is not only a competitive but also a cooperative relationship between luminescence and respiration. The respiratory NADH oxidase in the membrane fraction of V. harveyi showed some distinctive characters which are unique to the respiratory-dependent primary Na+pump, suggesting the possibility of coupling between the Na+pump and the luciferase system. This was also supported by the results from CCCP-resistant growth and luminescence at alkaline pH. The coupling mechanisms between luminescence and respiration in V. harveyi are discussed.

Respiratory dependence of the CCCP-resistant luminescence of Vibrio harveyi

SUMMARY: The relation between respiration and luminescence of Vibrio harveyi was studied in the presence of the proton conductor CCCP (carbonyl cyanide m-chlorophenylhydrazone). CCCP affected both luminescence and oxygen uptake rate, but did not alter the cellular ATP level. In the absence of CCCP, luminescence and oxygen uptake rate were almost constant over the pH range 6.5–8.5. However, at 10 μM-CCCP, both were apparently pH-dependent, with maxima observed at pH 8.5 and minima at pH 6.5. In the presence of CCCP (0.1–10 μM), the changes in the luminescence were in close correlation with those in the oxygen uptake rate regardless of the pH. HQNO (2-heptyl-4-hydroxyquinoline-N-oxide) and NaCN inhibited the CCCP-resistant luminescence. From these results, it is concluded that the CCCP-resistant luminescence is respiratory-dependent.