Porphyra Thalli Research Articles

Decreases in turbidity during neap tides initiate late winter blooms of Eucampia zodiacus in a macrotidal embayment

Eucampia zodiacus Ehrenberg is harmful, as it causes reduction in the quality of the aquacultured Porphyra thalli owing to nutrient depletions during dense blooms in the late winter in the macrotidal Ariake Sea, Japan. To understand the mechanism of bloom development, changes in the abundance of E. zodiacus during a bloom were investigated along vessel transects from February to April 2012. In addition, marine environmental variables were continuously monitored by the Ariake Sea Monitoring Tower, which revealed that turbidity periodically decreased during neap tides. During the 16 February neap tide, a high Secchi depth (4.3 m) was recorded at offshore stations and the Z 1% depth, at which the light intensity attenuates to 1 % of that at the sea surface, exceeded the water depth. On 16 February, the abundance of E. zodiacus was 52–732 cells mL−1, peaking at 7.0 m depth offshore. Subsequently, abundance increased at all stations. During the 22 February spring tide, abundance became vertically uniform. On 19 March, abundance at the tower reached 3758 cells mL−1 at the surface. We conclude that an improvement in light conditions in the deeper layer triggered the bloom, although the size and the duration of the bloom were determined by nutrient availability. Thus, decreases in turbidity during neap tides and subsequent strong vertical mixing during spring tides may be instrumental in the population dynamics of the large diatom E. zodiacus in macrotidal environments.

Metabolic plasticity of nitrogen assimilation by Porphyra umbilicalis (Linnaeus) Kützing

The physical stresses associated with emersion have long been considered major factors determining the vertical zonation of intertidal seaweeds. We examined Porphyra umbilicalis (Linnaeus) Kutzing thalli from the vertical extremes in elevation of an intertidal population (i.e. upper and lower intertidal zones) to determine whether Porphyra thalli acclimate to different vertical elevations on the shore with different patterns of nitrate uptake and nitrate reductase (NR) and glutamine synthetase (GS) activities in response to different degrees of emersion stress. We found that the nitrate uptake and NR recovery in the emersed tissues took longer in lower intertidal sub-population than in upper intertidal sub-population; and GS activity was also significantly affected by emersion and, interestingly, such an activity was enhanced by emersion of thalli from both upper and lower intertidal zones. These results suggested that intra-population variability in post-emersion recovery of physiological functions such as nutrient uptake and NR activity enables local adaptation and contributes to the wide vertical distribution of P. umbilicalis. The high GS activity during periodic emersion stress may be a protective mechanism enabling P. umbilicalis to assimilate nitrogen quickly when it again becomes available, and may also be an evidence of photorespiration during emersion.

UVB로 손상이 유도된 피부세포에 해양소재 추출물의 항노화 효능

피부는 끊임없이 외부환경에 노출되며 가장 주요한 스트레스 요인 중 하나는 자외선방사이다. 자외선 방사로 인하여 피부에 염증, 착색, 광노화 및 피부암을 포함하는 생물학적 영향을 끼치게 된다. 본 연구에서는 해양천연소재 (김, 다시마, 모려, 모자반, 미역, 석결명, 우뭇가사리, 청각, 톳, 파래)로부터 피부보호 항산화제를 조사하기 위해 자외선으로부터 기인된 세포보호 효과를 증명하였으며 세포독성, 산화에 의한 세포사멸, 항노화 효과에 대하여 평가를 실시하였다. 그 결과, 모자반, 한천, 석결명, 청각 에탄올 추출물을 처리한 군이 자외선으로 유도된 세포독성 및 세포사멸을 효과적으로 억제하는 것으로 나타났다. 또한 다른 실험에서 자외선에서 인한 세포사멸은 세포내 축적이나 ROS로부터 매개되지만 해양추출물을 처리함으로써 현저하게 감소되었다. 이러한 해양추출물의 보호효과 증가는 Type I collagen과 Type I procollagen에 의해 매개하는 것과 연관되는 것으로 사료된다. 이들의 결과는 해양추출물이 노화예방 및 항산화제로서의 우수한 특성으로 피부손상에 의한 산화적 스트레스에 대응하는 새로운 기능성 소재로서의 가능성을 가지는 것으로 평가된다. The skin is continuously exposed to environmental stresses. One of the most important stress factor is UV radiation. UV radiation causes a variety of biological effects on the skin, including inflammation, pigmentation, photoaging and cancer. Therefore in this study, we tried to search for skin-protective antioxidant materials from marine natural products (Porphyra Thalli, Laminariae japonicae thallus, Ostreae Concha, Sargassum Thallus, Undaria thallus, Haliotidis Concha, Agar, Codium thalli, Hizikia fusiforme thalli; HFE, Thalli) which exhibit protective activities against UVB-induced cytotoxicity and oxidative cell death and antiaging effects. As a results, UVB-induced cytotoxicity and cell death were effectively suppressed by treatment of Sargassum Thallus, Agar, Haliotidis Concha, Codium thalli, Thalli ethanol extracts. UVB-induced cell death was mediated by intracellular accumulation or ROS, which was significantly inhibited by treatment with marine natural products extracts. Also, The protective effect of these marine natural products seemed to be mediated by increased expression of type I collagen and Type I procollagen. These results suggest that marine natural products may have anti-aging effects new functional materials against oxidative stress-mediated skin damages.

B16 멜라닌 세포에서 해양소재 추출물의 멜라닌 생성 저해 효과

Objectives : Under normal condition melanin protects the skin from extracellular stimuli including ultraviolet (UV)-induced oxidative skin damages, but excess production and accumulation of melanin can induce hyperpigmentation causing esthetic problems. Therefore, in this study we tried to search for natural skin whitening materials from marine natural resources. Methods : Water and ethanol extracts of marine natural resources were prepared from Porphyra thalli (PT), Laminariae thallus (LT), Ostreae concha (OC), Sargassum thallus (ST), Undaria thallus (UT), Codium thalli (CT), Enteromorpha thalli (ET), Syngnathoides biaculeatus (SB), and Hippocampus coronatus (Hc). Their effects against UVB and <TEX>${\alpha}$</TEX>-melanocyte stimulating hormone (<TEX>${\alpha}$</TEX>-MSH)-induced melanogenesis were investigated based on melanin formation in B16 mouse melanoma cells. The mRNA and protein expression of enzymes involved in the melanogenic process were further examined by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analysis, respectively. Results : Water extract of Ostreae concha (OCW/E) effectively inhibited UVB and <TEX>${\alpha}$</TEX>-MSH-induced melanin production in B16 melanocytes, which seemed to be mediated by inhibition of mRNA expression of tyrosinase and tyrosinase-related protein 1 (TRP-1). In another experiment, ethanol extracts from Porphyra thalli (PTE/E), Laminariae thallus (LTE/E), Sargassum thallus (STE/E), Undaria thallus (UTE/E), Codium thalli (CTE/E), Syngnathoides biaculeatus (SBE/E), and Hippocampus coronatus (HcE/E) significantly suppressed UVB and <TEX>${\alpha}$</TEX>-MSH-induced melanin formation. Furthermore, ethylacetate fraction isolated form LTE/E (LTE/EEt) decreased UVB and <TEX>${\alpha}$</TEX>-MSH-elevated extracellular melanin levels via inhibition of tyrosinase protein expression. Conclutions : These results suggest that marine natural resources such as Porphyra thalli, Laminariae thallus, Ostreae concha, Sargassum thallus, Undaria thallus, Codium thalli, Syngnathoides biaculeatus and Hippocampus coronatus have anti-melanogenic effects, thereby exhibiting high potentials to be utilized as one of the ingredients for the development of new whitening functional cosmetics.

Nitrate and phosphate uptake kinetics of the harmful diatom Coscinodiscus wailesii, a causative organism in the bleaching of aquacultured Porphyra thalli

The large diatom Coscinodiscus wailesii is one of the problematic species which indirectly cause bleaching damage to “Nori” ( Porphyra thalli) cultivation through competitive utilization of nutrients during its bloom. In the present study, we experimentally investigated the nitrate (N) and phosphate (P) uptake kinetics of C. wailesii, Harima-Nada strain. Maximum uptake rates ( ρ max), obtained by short-term experiments, were 58.3 and 95.5 pmol cell −1 h −1 for nitrate and 41.9 and 59.1 pmol cell −1 h −1 for phosphate at 9 and 20 °C, respectively. The half saturation constants for uptake ( K s ) were 2.91 and 5.08 μM N and 5.62 and 6.67 μM P at 9 and 20 °C, respectively. The ρ max values of C. wailesii, much higher than those of other marine phytoplankton species, suggest that C. wailesii is able to take up large amounts of nutrients from the water column. On the other hand, V max/ K s ( V max; V max = ρ max/ Q 0, Q 0; minimum cell quota) values of C. wailesii, which is a better measure to evaluate the competitive ability for nutrient uptake, were low in dominant diatom species. This parameter indicates that C. wailesii is disadvantaged compared to other diatom species in competing for nutrients, and the decreasing nutrient concentrations from winter to spring is an important factor limiting C. wailesii blooming in early spring.

On the Properties of Seawater for Artificial Culture of Porphyra Thalli

On the Properties of Seawater for Artificial Culture of Porphyra Thalli

Nitrate and phosphate uptake kinetics of the harmful diatom Eucampia zodiacus Ehrenberg, a causative organism in the bleaching of aquacultured Porphyra thalli

The diatom Eucampia zodiacus Ehrenberg is a harmful diatom which indirectly causes bleaching of aquacultured Nori (Porphyra thalli) through competitive utilization of nutrients during bloom events. In the present study, we experimentally investigated the nitrate (N) and phosphate (P) uptake kinetics of E. zodiacus, Harima-Nada strain. Maximum uptake rates (ρmax), which were obtained by short-term experiments, were 0.777 and 0.916pmolcell−1h−1 for nitrate and 0.244 and 0.550pmolcell−1h−1 for phosphate at 9 and 20°C, respectively. The half-saturation constants for uptake (Ks) were 2.59 and 2.92μM N and 1.83 and 4.85μM P at 9 and 20°C, respectively. Although the maximum specific uptake rate (Vmax; Vmax=ρmax/Q0, Q0; minimum cell quota) and Vmax/Ks for nitrate at 9°C are about 1/2 of those obtained at the optimum temperature (20°C), they are still higher than those obtained for many other phytoplankton at their optimum temperature conditions for uptake. These results suggest that E. zodiacus utilizes nitrogen efficiently at low water temperature, and it is one of the important factors causing the serious damage to Porphyra thalli by bleaching due of this species. For phosphate, the Ks values of E. zodiacus were higher than those reported for other species; the Vmax and Vmax/Ks values were much lower than those of other diatoms such as Skeletonema costatum (Greville) Cleve. These results suggest that E. zodiacus is disadvantaged compared to other diatom species during competitive utilization of phosphate.

Effect of temperature on light-limited growth of the harmful diatom Coscinodiscus wailesii, a causative organism in the bleaching of aquacultured Porphyra thalli

The diatom Coscinodiscus wailesii is a harmful diatom which indirectly causes bleaching of aquacultured Nori ( Porphyra thalli) through competitive utilization of nutrients during bloom events. To elucidate the mechanism of the bloom, the effect of temperature on light-limited growth of C. wailesii was examined at 13 irradiance levels (5–350 μmol m −2 s −1) in combination with 4 temperature levels (9.0–20.0 °C). The results showed that all the parameters of growth-irradiance curves such as the maximum growth rate, half saturation constant, threshold value of irradiance and saturation irradiance for growth increased with increasing temperature. On the basis of the relationship between temperature and growth-irradiance curves and seasonal fluctuation of the light environment in Harima-Nada, the population dynamics of C. wailesii during the period from October to March was evaluated using two indices D t (depth of the threshold irradiance for growth) and D 0.5 (depth of growth rate is 0.5 divisions per day). As the vegetative cells of C. wailesii tend to distribute in relatively deeper water layers where the growth is limited by irradiance, the increase in the depth range over which C. wailesii is able to grow or grow at a high growth rate is concluded to be an important factor allowing the development of the blooms.

Population dynamics of the harmful diatom Eucampia zodiacus Ehrenberg causing bleachings of Porphyra thalli in aquaculture in Harima-Nada, the Seto Inland Sea, Japan

The diatom Eucampia zodiacus Ehrenberg is one of the harmful diatom species which indirectly cause bleachings of Nori ( Porphyra thalli) in aquaculture through competitive utilizing of nutrients (especially nitrogen) and resultant nutrient depletion in water columns during the bloom events. The seasonal changes in environmental factors, cell density and cell size of E. zodiacus were investigated for 4 years (April 2002–December 2005) to understand the population ecology of this diatom in Harima-Nada, the eastern part of the Seto Inland Sea, Japan. Vegetative cells of E. zodiacus were usually detected year-round. Total cell densities of E. zodiacus annually peaked from mid-February to early April, and high cell densities were observed in the whole water columns during the bloom-period. Nutrient concentrations decreased with the increase of cell density of E. zodiacus, and low nutrients concentrations continued throughout the E. zodiacus bloom-period. The average cell size (length of apical axis) of E. zodiacus populations ranged from 10.8 μm to 81.2 μm, and the restoration of cell size occurred once in autumn every year just after reaching the minimum cell size. In addition, its great seasonal regularity was confirmed by the decrease and restoration of its cell size through 4-year study period. Temperature and nutrients were suitable in autumn for the growth of E. zodiacus, its blooms never occur in that season. These results strongly suggest that E. zodiacus did not have a resting stage, and it spends autumn for size restoration and starts to bloom thereafter in Harima-Nada in winter and spring, causing fishery damage to Nori aquaculture by resulting nutrient deprivation.

Preparation of recombinant polysaccharide-degrading enzymes from the marine bacterium, Pseudomonas sp. ND137 for the production of protoplasts of Porphyra yezoensis

We previously reported that a marine bacterium, strain ND137, produced the enzymes to make protoplasts from the thalli of a marine red alga Porphyra yezoensis. In this study, the bacterium was classified as Pseudomonas sp. based on the sequence of the gene encoding 16S rRNA and the G + C content of the DNA. The β-1,4-xylanase-, cellulase-, β-1,3-xylanase-, porphyranase-, and β-1,4-mannanase-encoding genes were cloned from the genomic library of Pseudomonas sp. ND137 and expressed in Escherichia coli. The protoplasts from Porphyra yezoensis were produced by treating the thalli with several combinations of these recombinant crude enzymes. Treatment of the Porphyra thalli with any of these enzymes on their own failed to produce protoplasts. However, a mixture of β-1,3-xylanase, porphyranase, and β-1,4-mannanase produced protoplasts, although β-1,4-xylanase and cellulase were not observed to have any effect on protoplast production. These results indicate that among the five recombinant crude enzymes, β-1,3-xylanase, porphyranase, and β-1,4-mannanase are essential for producing protoplasts from the thalli of P. yezoensis. The yield of the protoplasts was 1.4 × 104 cells mg−1 wet weight of the thalli, indicating that these recombinant enzymes can be used efficiently for protoplast production from P. yezoensis.

Forecasting infections of the red rot disease on Porphyra yezoensis Ueda (Rhodophyta) cultivation farms

Pythium porphyrae is a fungal pathogen responsible for red rot disease of the seaweed Porphyra (Rhodophyta). Infection forecasts of Porphyra by P. porphyrae were estimated from the epidemiological observations of Porphyra thalli and numbers of zoospore of P. porphyrae in laboratory and cultivation areas. Four features of forecasting infections were determined by relating zoospore concentrations to the incidence of thallus infection; infection (in more than 1000 zoospores L−1), microscopic infection [less than 2 mm in diameter of lesion (in from 2000 to 3000 zoospores L−1)], macroscopic infection [more than 2 mm in diameter of lesion (in from 3000 to 4000 zoospores L−1), and thallus disintegration (in more than 4000 zoospores L−1). High zoospore concentrations led to more infection. The tendency that zoospore concentration of P. porphyrae increased with the rate of infection of Porphyra thalli was generally observed in forecasting infections in both the laboratory and in cultivation areas. Based on the Porphyra cultivation areas, the accuracy and consistency of forecasting infections suggest that this method could be employed to manage and control red rot disease.

Exploring Northeast American and Asian species of Porphyra for use in an integrated finfish–algal aquaculture system

Many aquaculture industries generate a nutrient-rich waste stream that can lead to eutrophication of coastal waters. To address this environmental issue, the bioremediation potential of several native Northeast American species of Porphyra was assessed and compared to the well-known Asian species. Porphyra thalli were cultured over 4 weeks at 15 °C at a stocking density of 0.4 g FW L − 1 . At 3- to 4-day intervals nutrient uptake, tissue N accumulation and phycobiliprotein concentration (PBP) were determined as functions of nitrogen (N) concentration (25–300 μM) and N source (nitrate vs. ammonium). Growth rates were measured weekly. Growth and tissue N reached maximal levels at inorganic N concentrations of 150–300 μM. Maximum growth rates ranged from 10% to 25% day − 1 , although induction of archeospores reduced average growth rates in many cases. No evidence of ammonium toxicity (reductions in growth rate) was observed; in fact, similar values were found with both N sources. Ammonium generally yielded higher PBP and tissue N contents than nitrate. Porphyra amplissima presented the highest growth rate, followed by the Asian Porphyra yezoensis. Under the experimental conditions, Porphyra spp. removed 70–100% of N within 3–4 days at N concentrations up to 150 μM, but was less efficient in removing inorganic phosphorus (35–91% removal). The highest tissue N and PBP concentrations were found at 150–300 μM of N, with N values close to 7% DW. Overall, Porphyra appears to be an excellent choice for bioremediation of moderately eutrophic effluents, with the added benefit that tissue may be harvested for sale.

Effect of temperature on light-limited growth of the harmful diatom Eucampia zodiacus Ehrenberg, a causative organism in the discoloration of Porphyra thalli

The diatom Eucampia zodiacus Ehrenberg is one of the harmful diatoms which indirectly cause, through nutrient depletion, discoloration of Porphyra thalli. The effect of temperature on light-limited growth of E. zodiacus was examined at 13 irradiance levels (5–350 μmol m −2 s −1) in combination with five temperatures (8.0–25.0 °C). The results showed that all the parameters of growth-irradiance curves, such as the maximum growth rate ( μ m), half saturation constant ( K s), threshold value of irradiance ( I 0) and saturation irradiance for growth ( S), increased with increasing temperature. On the basis of the relationship between temperature and growth-irradiance curves and seasonal fluctuation of the light environment in Harima-Nada, the effect of irradiance on the population dynamics of E. zodiacus during the period from October to March was evaluated using two indices, depth of the threshold irradiance for growth ( D t) and depth where a half of its maximum growth rate is attained ( D k). D t and D k remained almost stable from October to December, but gradually increased in early March. This indicates that the range of depth at which E. zodiacus was able to grow increased markedly in early spring when E. zodiacus blooms in Harima-Nada. As the vegetative cells of E. zodiacus tend to distribute in relatively deeper water layers, where growth is limited by irradiance, the increase in the depth range over which E. zodiacus is able to grow is concluded to be an important factor allowing development of its blooms.

Serological detection of red rot disease initiation stages of microbial pathogen, Pythium porphyrae (Oomycota) on Porphyra yezoensis

Pythium porphyrae (Oomycota), a pathogen causing red rot diseasein Porphyra spp., can at present only be detected when colonizationof the host thallus has already occurred and so it is often too late to takeappropriate disease control measures. The paper presents an account of an effective methdology for early detection of the disease. Since Py.porphyrae zoospores are the primary means of pathogen dispersal,polyclonal antibodies (Pabs) were raised against the surface components ofzoospores and encysted zoospores. Using these Pabs the disease initiationstages of the Pythium porphyrae were detected on the surface of Porphyra thalli by immunofluorescence assay. The specificity of theseantibodies and the efficacy of immunofluorescence assay in the detectionof red rot disease are discussed.

Isolation of bacteria that decompose major polysaccharides in the cell wall of the marine red alga Porphyra yezoensis and their application for protoplast production

We attempted to screen for bacteria that could decompose major polysaccharides in the cell wall of the marine red alga Porphyra yezoensis from Porphyra-culturing farms to enable simple and high-yield preparation of protoplasts with the crude enzyme from a single bacterial origin. A total of 275 positive bacterial strains were isolated by enrichment culture supplemented with Porphyra powder or xylan. Nine strains were capable of producing protoplasts from Porphyra thalli in a 10-fold concentrated culture broth. These strains were identified as two Flavobacterium spp., one Alteromonas sp., four Acinetobacter spp., and two Vibrio spp. The crude enzymes of these bacteria could release 106 protoplast cells from 0.1 g of Porphyra thalli. The crude enzyme from Alteromonas sp. strain ND137 produced the most protoplasts among the nine strains tested. Moreover, an assay of the crude enzymes from the nine bacterial strains for glycosidase activity against four major polysaccharides (xylan, mannan, porphyran, and cellulose) of P. yezoensis revealed strong decomposing activity against these polysaccharides. Xylanase activity was highest in these glycosidases, suggesting that xylanase might be a very important factor in producing protoplasts from Porphyra thalli.Key words: Porphyra, cell wall, bacteria, decomposing polysaccharide.

Responses of Cultivated Porphyra Thalli to Water Temperature and Water Current-I. Effects of Water Temperature on the Growth of Red Alga Porphyra yezoensis from. narawaensis (Nori) Cultivated in an Outdoor Raceway Tank.

In order to examine effects of seawater temperature on the growth of Porphyra foliose thalli, outdoor raceway tanks with circulating water were newly designed, and provided the experimental condition simulating Nori cultivation farms in the sea. Frozen seed nets of Porphyra yezoensis form. narawaensis were set in the raceway tanks. During the period of the two experiments, December in 1985 and February in 1986, mean seawater temperature ranged from 8.0 to 23.4°C. Standing crop of foliose thalli increased normally at 10-17°C, but the increase rate of standing crop lessened at the temperature higher and lower beyond these limits. Visible absorption spectra of living foliose thalli, indicating concentrations of photosynthetic pigments, did not vary much within the range of seawater temperature from 8 to 20°C. The optimum seawater temperature for the growth of Porphyra foliose thalli ranged from 10 to 17°C in the raceway tanks. This temperature range confirmed results obtained through in vitro experiments but was higher than that in Nori cultivation farm.

都市下水の養殖ノリの生育に及ぼす影響に関する研究 ＩＶ 養殖ノリの生育に及ぼす塩素殺菌都市下水処理水の影響

The effects of chlorinated effluent of activated sludge treatment on the growth of Porphyra yezoensis were investigated with different chlorinated effluent-dosed culture media and different chlorine-dosed, diluted Provasoli's Enriched Seawater (PES) culture media as a control, by means of a shaking culture. To clarify the effect of the chlorinated effluent on the Porphyra thalli, the length of thalli were measured every two days, and the number of dead cells in a thallus were counted under a microscope 4-10 days after the start of the culture followed by an erythrosine staining. Initial chlorine concentrations which manifested a 50% growth effect and 50% dead cell in chlorinated effluent-dosed culture and chlorine-dosed diluted PES culture were 0.025-0.035mg Cl2/l and 0.06mg Cl2/l, and 0.75-0.95mg Cl2/l and 1.5-3mg Cl2/l, respectively. The growth effect and dead cells manifestation were dependent on the initial chlorine concentrations in both cultures. It was found by the amperometric method that chlorine was free chlorine in the diluted PES culture and combined chlorine in the chlorinated effluent-dosed culture. Although both residual chlorines disappeared with the passage of time, the removal rate of combined chlorine was slower than that of free chlorine. The above mentioned results suggest that the strong toxicity may be caused by the reaction products of chlorine with organic substances in the effluent.

都市下水の養殖ノリの生育に及ぼす影響に関する研究 ＩＩＩ 養殖ノリの生育に及ぼす下水処理場処理水の影響評価のための採水時間

The sampling time in a day and the day of the week were investigated to evaluate the effects of unchlorinated activated sludge effluent from the municipal sewage plant on the growth of Porphyra yezoensis by means of in vitro shaking culture. Effluents examined were sampled, before the chlorination occurred in the sewage plant, every two hours in one day and every day at 15:00 over one week. To clarify the difference in the effects on the Porphyra thalli, the thalli length and the absorbance spectra were measured, and dead cells were observed. Hourly sampled efliuents (Thursday-Friday) were classified roughly into three time zones from a standpoint of the effects on the growth ofPorphyra thalli, they were 11:00-17:00, 21:00-next day 5:00 and transition time zone. Effluent sampled daily at 15:00 were classified roughly.into three types from a standpoint of the growth of the Porphyra thalli: samples collected from Tuesday to Friday, on Saturday and from Sunday to Monday. The above mentioned results suggested that normally, the sampling time zone and day of the week to evaluate the effects of activated, unchlorinated effluent may be (1) 13:00-17:00 on Sunday, on Monday and on one of the day's from Tuesday to Thyrsday and (2) 23:00-next day 1:00 on Sunday and on one of the day's from Tuesday to Friday.

都市下水の養殖ノリの生育に及ぼす影響に関する研究 ＩＩ 養殖ノリの生育に及ぼす都市下水処理水の影響評価のための培養法について

The effect of effliuents from municipal sewage treatment plants on the growth of Porphyra yezo-ensis was studied by comparing the shaking culture method with the static culture method. Emuents examined were sampled before chlorination, and Provasoli's enriched seawater(PES) was used as a control. To clarify the differences in effects between shaking and static cultures on the growth of Porphyra thalli, the thalli length and the absorption spectra of living thalli were measured every second day. The number of dead or diseased cells in a thallus were observed under a microscope followed by erythrosine staining after 10 to 12 days from the start of the culture. The ranges of relative length of the thalli (1.8-4.9 and 1.3-2.1) were obtained after 10 days in effluents, with a salinity of 31‰ by shaking or static cultures, respectively. The maximum relative length of thalli (5.8) was obtained after 10 days in a fortyfold diluted PES medium, with a salinity of 31‰ by shaking culture. The shaking culture method showed a higher sensitivity than the static culture method for other aspects examined regarding the effect of the effluent on the growth of Porphyra thalli.

都市下水の養殖ノリの生育に及ぼす影響に関する研究 Ｉ 静置培養における養殖ノリの生育に及ぼす都市下水処理水の影響

The effects of unchlorinated activated sludge effluent from a municipal sewage treatment plant on the growth of Porphyra yezoensis were inverstgated for different effluent dosages with different degrees of salinity by means of in vitro static culture. To clarify the effect of the effluent on the Porphyra thalli, the length of thalli and the absorbance spectra of living thalli were measured every two days. The number of dead cells in a thallus were counted using a microscope 10 days after the start of the culture, followed by a erythrosine staining. While increasing the effluent dosage to about 5% by volume, the relative length of thalli decreased rapidly and the number of dead cells quickly increased, and they were enhanced with the lower salinity. When the effluent dosages was above 5%, the relative length of thalli and the number of dead cell had a definite value for each degree of salinity. The absorbance spectra (350-750nm) and absorbance ratio (567nm/676nm) of living thalli increased when the effluent dosage and exposure time were increased.The above mentioned results suggest that the activated sludge effluent of municipal waste-water may have an adverse effect on the growth of Porphyra thalli.