Masahiro Notoya

Recent fluctuations in distribution and biomass of cold and warm temperature species of Laminarialean algae at Cape Ohma, northern Honshu, Japan

The Cape Ohma region of Shimokita Peninsula, the northernmost point of Honshu Island, Japan, is subject to both the warm Tsugaru Current and the cold Kurile Current. As a result, the Laminarialean flora includes both cold temperature species (Laminaria japonica Areschoug, Kjellmaniella crassifolia Miyabe and Costaria costata (C. Agardh) Saunders) andwarm temperature species (Undaria peterseniana (Kjellman) Okamura, Ecklonia stolonifera Okamura), as well as Undaria pinnatifida (Yendo) Okamura, which is distributed in both waters. The frequency of occurrence (as a measure of distribution) and the biomass of these species were recorded in June 1976 (at 50 points in depths between 8–30 m), July 1988 (192 points, 2.5–25 m) and July 2001 (78 points, 2.5–25 m). Comparison of these data revealed a decrease in cold temperature species and an increase in warm temperature species from 1976 or 1988 to 2001. Long-term data of seawater temperature measured at 5 m depth near the study site showed that mean temperatures in the middle of winter (late January to February) in 1989–2000 were 0.9–1.1 °C higher than those in 1980-1988. Higher seawater temperatures in the last decade appear to have affected the frequency of occurrence and biomass of the Laminarialean species along the coasts of Cape Ohma. This result supported our previous conclusion that 1 °C higher mean seawater temperature in late January caused a decrease in the biomass of L. japonica (by ca. 64%) along the same coast.

Life history, in culture, of the obligate epiphyte Porphyra moriensis (Bangiales, Rhodophyta)

The life history of the obligate epiphyte Porphyra moriensis Ohmi, collected from the type locality in Japan, was demonstrated in culture. Conchocelis filaments were cultured at temperatures between 5 and 30 °C under photon irradiances of 10–80 μmol m−2s−1 and photoperiods of 10L:14D or 14L:10D. Conchosporangial branches developed at 5–20 °C under both photoperiods, and were abundant when the conchocelis was cultured at 20 °C, 20 μmol m−2s−1, 14L:10D and 15 °C, 40 μmol m−2s−1, 10L:14D. No foliose thalli survived at 25 or 30 °C and conchocelis failed to survive at 30 °C. Released conchospores attached very poorly to synthetic strings and glass slides but settled very well on Chorda filum thalli and thereafter germinated to develop into foliose thalli. Thalli grew well at 15 °C and 14L:10D or 10L:14D and at 20 °C and 10L:14D. No archeospores were observed on the thallus under any culture conditions. Spermatangial and zygotosporangial sori were formed in patches along the upper margins of mature thalli. Anatomical examination revealed that the mature spermatangial packets were 128 (a/4, b/4, c/8) and zygotosporangia were 16 (a/2, b/2, c/4) according to the Hus formula. Released zygotospores gave rise to conchocelis filaments. Neither monospores nor protothalli were produced by the conchocelis in culture. The life history of this plant is a simple biphasic cycle, with the thallus stage appearing to require attachment to Chordafilum.

’seed’ production of Porphyra spp. by tissue culture

Differentiation of archeospores was observed from excised tissue of young thalli of various monoecious Porphyra species (P tenera, P. yezoensis, P suborbiculata, P okamurae) after 4–8 days in culture at temperatures of 20 and 25 °C. Excised tissue from adult thalli did not differentiate into archeospores, but rather regenerated directly into blades and rhizoids of foliose thalli. Tissues from young thalli of two dioecious Porphyra species (P. dentata and P pseudolinearis) also regenerated into blades and rhizoids after manipulation of the culture conditions. In addition, 1–2 celled tissue pieces of both monoecious and dioecious species were also seen to develop directly into blades. Polarity of regeneration of blades and rhizoids was observed in these species. These results suggest that ‘seed’ can be obtained through tissue culture instead of using conventional conchocelis culture for commercial nori aquaculture in Japan.

Physiological Responses of Blade and Conchocelis of Porphyra vietnamensis Tanaka et Pham-Hoang Ho (Bangiales, Rhodophyta) from Thailand in Culture

The effects of temperature (10-30°C), photon flux density (10-80 µmol · m ‐2 ·s ‐1 ), salinity (10-40 ppt) and photoperiod (14L: 10D and 10L: 14D) on the growth and maturation for the conchocelis and blade phase of Porphyra vietnamensis Tanaka et Pham-Hoang Ho from Thailand were examined under laboratory conditions to investigate data of tropical species. Maximum growth rate of the conchocelis showed at 25°C, 80 µmol · m ‐2 ·s ‐1 under 35 ppt and 14L: 10D without formation of conchosporangial branch during 6 weeks of culture period. An early formation of conchosporangial branch was observed at 30°C, 20-40 ppt under 80 µmol · m ‐2 ·s ‐1 of both photoperiods after 2 weeks in culture. Early conchospore release occurred at 20-35 ppt and 10L: 14D under 30°C and 80 µmol · m ‐2 ·s ‐1 at 4th weeks of culture. Fast growth of the conchospore germlings was observed at 25°C under the both of photoperiods in 35 ppt and 80 µmol · m ‐2 ·s ‐1 . The blades culture at 30°C produced only archeospores after 2 weeks throughout the culture period. Under the optimum culture conditions of 25 ppt and 14L: 10D at 25°C and 80 µmol · m ‐2 ·s ‐1 , the blades matured and liberated zygotospores within 6 weeks. In good combinations of conditions at the four factors, the life cycle was completed within 12 weeks in culture.

Relation between size and age of holdfasts of Ecklonia stolonifera Okamura (Laminariales, Phaeophyta) in northern Honshu, Japan

Ecklonia stolonifera is distributed along the coast facing the Sea of Japan. The size of various parts of the shoot (blade length and width and stipe length and diameter) and the age were determined at Ooma, Aomori Prefecture. The smaller the holdfast, the higher the percentage of one-year-old shoots. Holdfasts 10 cm in diameter seemed to be three years old, whereas holdfasts 40 cm in diameter seemed to be five or more years old. Zoosporangial sori were observed on blades three or more years old. Ecklonia stolonifera holdfast diameter expands only vegetatively by stoloniferous rhizoids. Zoospores, formed on shoots three or more years old, serve for the formation of new populations.

Distribution and recent reduction of Gelidium beds in Toyama Bay, Japan

The distribution and recent reduction of Gelidium beds, i.e. mat-like beds dominated by the agarophyte G. elegans Kützing in Toyama Bay (Sea of Japan), in which 95% of the coastline is protected artificially, are reported. Gelidium beds were common in shallow waters (usually < 10 m deep); most of the large beds (> 1 ha) were restricted to the inner coasts of the bay. In calm and eutrophic areas, however, G. elegans was heavily colonized by epiphytes. In the last decade, two beds were buried in situ and beds in their vicinity were damaged by the stagnation of coastal water and/or sedimentation by silts which accompanied land reclamation. At the other two beds monitored since 1988, Gelidium declined a few times but most prominently in 1998, when episodic long summer rain was recorded. This is the first report, not only on the current status of Gelidium beds other than for the central Pacific Coast of Honshu in Japan, but also concerning reduction of the beds caused by both anthropogenic and natural events.

Studies on the growth, in culture, of two forms of Porphyra lacerata from Japan

Comparative studies were conducted on two forms of Porphyra lacerata Miura (Bangiales, Rhodophyta). Growth, morphological characteristics and maturation were compared in small epiphytic forms collected from Banda, Chiba Prefecture and large epilithic forms from Enoshima, Kanagawa Prefecture. Germlings of both types were cultured at temperatures of 10, 15 and 20 °C, an irradiance of 40 μmol m−2 s−1 and photoperiods of 14L:10D (light:dark) and 10L:14D. After 12 weeks, under identical culture conditions, the maximum size of foliose thalli of the epiphytic form was less than the epilithic form. At a temperature of 10 °C, the morphology of the Enoshima plants changed from cordate to lanceolate, whereas those from Banda retained their cordate shape. Under various culture conditions, the formation and liberation of archeospores were more abundant in the form from Banda. These observations suggest that the two forms of P. lacerata may represent different species, but further studies are required.

Eicosapentaenoic acid release from the red alga Pachymeniopsis lanceolata by enzymatic degradation

Forty-eight species of seaweeds from Japanese waters were screened for the valuable polyunsaturated fatty acids eicosapentaenoic acid (EPA). The eight species that contained the highest levels of these compounds were analyzed in detail. Of all species tested the red alga Pachymeniopsis lanceolata contained the highest EPA concentration, and it was present as both the free and bound forms. EPA constituted 38.7% of total fatty acids, and polar lipids were the main constituent of the total lipids in P. lanceolata. EPA was obtained from the marine algae P. lanceolata by enzymatic hydrolysis of the total lipids extract using phospholipase A2(PLA2). The release of EPA reached a plateau after 10 min of enzymatic treatment. These results suggest that P. lanceolata is a useful natural source of EPA and that PLA2 treatment is a convenient method for obtaining EPA from the red alga.

Chloroplast changes and differentiation of callus cells in Eckloniopsis radicosa (Kjellman) Okamura (Phaeophyta, Laminariales)

Excised rectangular blade pieces of young sporophytes of Eckloniopsis radicosa (Kjellman) Okamura were cultured at four different temperatures (10, 15, 20, 25 °C) and light intensities (10, 20, 40, 80 µmol photon m−2 s−1) to observe callus cell propagation and differentiation. Although rapidly propagating callus cells were observed at a low temperature (15 °C) and low light intensities of (10–20 µmol photon m−2 s−1), differentiation to bladelets was only observed at higher temperatures and light intensities. In rapidly propagating callus cells, the chloroplasts decreased in both size and number. When callus cells with few chloroplasts were exposed to high temperature and light intensity, the chloroplasts gradually increased in number and size until they were the same size as found in cells from young blades. Finally, these cells differentiated and produced bladelets. This is the first report describing a relationship between differentiation and chloroplast size and number in the callus cells on E. radicosa.

Life History of Porphyra seriata Kjellman (Bangiales, Rhodophyta) from Korea in Laboratory Culture

The laboratory culture study of Porphyra seriata Kjellman from Korea was conducted at different conditions of temperatures (5, 10, 15, 20, 25 and 30), photon flux densities (10, 20, 40 and 80 mol ) and photoperiods (14L: 10D and 10L:14D). Conchocelis filaments grew fast at 15-20 and 20-80 mol under both photoperiods. Concho sporangial branches were produced at 5-25, and abundant when the conchocelis filaments were cultured at higher temperatures of 20-25 under both photoperiods. Foliose thalli grew well at 15-20 under 10L:14D and at 20 under 14L:10D. At 30, the foliose thallus failed to survive. No archespores were observed at any culture conditions. Spermatangia and zygotosporangia were formed in squarish patches at the upper marginal portion of mature thalli. Anatomical examination revealed that the mature spermatangia were 64 (a/4, b/2, c/8) and 128 (a/4, b/4, c/8), and that of zygotosporangium was 16 (a/2, b/2, c/4) according to the Hus` formula.