abstract

Technical Report
Title An accurate scheme for hyperbolic equations based on the memory saved Cubic Interpolated Pseudo-particle Method
Authers Kosei KOMATSU*
Keywords accurate advection scheme, Cubic Interpolated Pseudo-particle (CIP) method, numerical
Citation Bull. Fish. Res. Agen. No.9, 1-10, 2003
Abstract
 A new scheme for hyperbolic equations was developed based on the Cubic Interpolated Pseudo-particle method (CIP) which is one of the most precise among schemes with third-order accuracy in space. The CIP, however, requires memories of spatial derivatives of solutions while it is more efficient than another accurate schemes, which is a serious shortcoming especially for use in complex models such as current ocean ecosystem models composed of more than 10 compartments. The new scheme, named the simplified CIP method (SCIP), requires no memory of supplementary parameters and uses only one step for time integration. Moreover compared with previous lower-order accurate schemes, the scheme has both of higher stability and higher performance without remarkable diffusions and dispersions caused by finitedifference approximations, although it is second-order accurate in space and it contains neither additional diffusivities nor temporal smoothing.

Received on June 13, 2003
Contribution No.A 40 from Fisheries Research Agency
* National Research Institute of Fisheries Science, Fukuura 2-12-4, Kanazawa, Yokohama, Kanagawa, 236-8648, Japan



Doctoral Thesis
Title Physiological and ecological studies on harmful dinoflagellate Heterocapsa circularisquama - Ⅱ Clarification on toxicity of H. circularisquama and its mechanisms causing shellfish kills
Authers Yukihiko MATSUYAMA*
Keywords Heterocapsa circularisquama, dinoflagellate, bivalve, mortality, toxicity
Citation Bull. Fish. Res. Agen. No.9, 13-117, 2003
Abstract

Heterocapsa circularisquama Horiguchi (Dinophyceae) is a causative agent of red tide organism, appeared in 1988 in first time and then rapidly dispersed off the coastal waters of western Japan. The red tide due to H. circularisquama was associated with massive killing of commercially important bivalve species: pearl oyster Pinctada fucata martensii, Pacific oyster Crassostrea gigas, manila clam Ruditapes philippinarum, blue mussel Mytilus galloprovincialis, etc. Until 2000, 31 cases of H. circularisquama red tide (including 16 incidences leading to fisheries damage) had been recorded in western Japan. Economic losses in shellfish aquaculture by direct killing of marketable products were estimated about at least 10 billion-yen in the last decade. Although the recurrent blooms of H. circularisquama had damaged the shellfish aquaculture, no harmful effects on wild and cultured finfish, other marine vertebrates, and public health hazard were recorded. Therefore, this phenomenon is referred to as "novel red tide." The red tide due to H. circularisquama has devastates shellfish aquaculture in most of the region, in terms of mass mortality in farming organism, cost of measures to prevent the damage, adversely affects the development of shellfish aquaculture, and secondary damage, i.e. decline of demand due to misinformation. Incidence of this species has increased recently, and the economic losses in aquaculture have been a cause for concern for the industry and society. In the present study, mechanism of damage caused to shellfish aquaculture, toxicity of the organism were conducted, in order to clarify the mechanism to be causing shellfish death due to H. circularisquama red tide.

In field observations, pearl oysters exposed to 4,000-6,000cells/mL of H. circularisquama resulted in death within several days although the level of dissolved oxygen was not critical for their survival. The dead individuals were characterized by various negative symptoms: valve closure, marked shrinkage of the mantle, decrease of glycogen lobe attached to the mantle, gut discoloration, cardiac disorder, paralytic etc.. The symptoms caused by the H. circularisquama exposure clearly showed a potent cytotoxic effect on bivalve physiology. The consist cytotoxicity to the bivalve molluscs was also confirmed in laboratory-reared experiment. Further, laboratory exposure experiments revealed that various marine animals such as bivalves, gastropods, ascidians, jellyfish, ciliates, and some naked phytoflagellates are affected by H. circularisquama unlike vertebrates, crustaceans, starfish, and sea urchins, and mouse.In field observations, pearl oysters exposed to 4,000-6,000cells/mL of H. circularisquama resulted in death within several days although the level of dissolved oxygen was not critical for their survival. The dead individuals were characterized by various negative symptoms: valve closure, marked shrinkage of the mantle, decrease of glycogen lobe attached to the mantle, gut discoloration, cardiac disorder, paralytic etc.. The symptoms caused by the H. circularisquama exposure clearly showed a potent cytotoxic effect on bivalve physiology. The consist cytotoxicity to the bivalve molluscs was also confirmed in laboratory-reared experiment. Further, laboratory exposure experiments revealed that various marine animals such as bivalves, gastropods, ascidians, jellyfish, ciliates, and some naked phytoflagellates are affected by H. circularisquama unlike vertebrates, crustaceans, starfish, and sea urchins, and mouse.

According to survival experiments using various culture condition of H. circularisquama, toxicity of H. circularisquama on the mussel were increased in the high water temperature and high salinity culture conditions, but markedly decreased in nitrogen- limited conditions. These results suggested that toxicity of this dinoflagellate was considerably affected by environmental conditions in nature. Further, comparative studies on toxicity of H. circularisquama cells showed that toxicity of this algae clearly varied among strains which isolated from various locatities in Japan.

The toxicity of H. circularisquama to bivalves molluscs was clearly mediated by a chemical agent. The toxic effect of H. circularisquama on bivalves was not due to extracellular metabolites, cell exudates, and "naked cells" prepared by sonication and centrifugation. Furthermore, SDS (sodium dodecyl sulfate), triethanolamin, and trypsin treatments were found to decrease drastically the toxicity of H. circularisquama cells. The metabolism inhibitor for protein and glycochains also reduced the toxicity of H. circularisquama. Therefore, labile glycoprotein-like complex localized on the cell surface of H. circularisquama presumably exerts a detrimental effect on bivalves. Furthermore, H. circularisquama did not affect on the anterior byssus retractor muscle of the mussel M. galloprovincialis but significantly affects on the radula retractor muscle of rapa whelk Rapana venosa, having various chemical receptors against peptide and other related substances. These results indicated that H. circularisquama does not synthesize monoamines such as dopamine and acetyl-cholin, alternating bivalve physiology. Some bivalve species resulted in gill damage and cardiac disorder in early periods of the exposure experiment. Histological study on manila clam exposed to H. circularisquama demonstrated that marked collaps of the mitocondria and muscle fiber occurred in several minuts. This is considered as a potencial factor causing short-term death in shellfish species. Further, H. circularisquama showed lethal effects on the early stage of bivalve species. Exposure of H. circularisquama to non-fertilized eggs of bivalve causes rapid collapse of vitelline envelope of eggs. These results indicated that a receptor destroying enzyme or related substances in the cell surface of H. circularisquama is the causative agent of shellfish kills. Further, affected larval stage of R. philippinarum by the H. circularisquama showed drastic increases of intracellular calcium concentration. Therefore, detrimental effects of H. circularisquama cells to the targeted organs (gills and mantle etc) led significant increases the concentration of intracellular calcium at critical level, that is probably brought about collapse of bivalve homeostasis.

The toxicity of H. circularisquama can easily lost by the simple mechanical disturbance such as centrifugation of their cells. Further, the toxicity of H. circularisquama cells has been dropped by gently treatments of SDS (sodium dodecyl sulfate), triethanolamine, and trypsin. These detoxicated cell are readily cleared by the filter-feeding bivalve without any negative responses. Therefore, physiological and chemical treatments can be apply to prevent the detrimental effect of H. circularisquama in future. However, widespread application of these procedures for marine environments may exert a secondary harmful effect on the other valuable aquatic organisms. It is necessary to improve the economically cost and to asses risk management. Biological control of H. circularisquama; i. e. diatoms growth promoting due to silicate conditioning in coastal waters and clearances of H. circularisquama cells by the other filter-feeder such as dense population of ascidians is likely to be low cost and environmentally acceptable techniqus for mitigation in future.

Received on June 26, 2003
Contribution No.A 41 from Fisheries Research Agency
* National Research Institute of Fisheries and Environment of Inland Sea, 2-17-5, Maruishi, Ohno, Saeki, Hiroshima, 739-0452, Japan


Title Studies on Oceanic Primary Production using Ocean Color Remote Sensing Data
Authers Takahiko KAMEDA*
Keywords ocean color remote sensing, primary production, two-phytoplankton community model, seasonal and annual variation
Citation Bull. Fish. Res. Agen. No.9, 118-148, 2003
Abstract
This paper is intended to investigate of seasonal, annual and interannual variation of oceanic primary production by ocean color remote sensing data. In chapter 2, a two-phytoplankton community model based on the difference of productivity among the phytoplankton cell size was developed. In chapter 3, oceanic primary production was calculated by the two-phytoplankton community model and environmental data such as sea surface temperature, chlorophyll concentration and solar radiation from September 1997 to June 2001. The spatial, seasonal, annual and interannual variations of this time series of oceanic primary production were analyzed. Furthermore, relationships between primary production and El Nino/Southern Oscillation in the Pacific Ocean were examined. In chapter 4, seasonal variation of chlorophyll concentration and primary production in the western North Pacific were analyzed. By cluster analysis of chlorophyll concentration, the western North Pacific was divided into eight areas which showed original seasonal variation of chlorophyll concentration. Because these areas were corresponded to the Subtropical gyre, Transition domain and Subarctic gyre, the seasonal variations of chlorophyll concentration in western North Pacific was affected by physical conditions.

Received on July 3, 2003
Contribution No.A 42 from Fisheries Research Agency
* Oceanography and Southern Ocean Resources Division, National Research Institute of Far Seas Fisheries, 5-7-1, Shimizu-Orido, Shizuoka, Shizuoka, 424-8633, Japan