Tadahide Noro

Photosynthesis and growth rates of Laurencia brongniartii J. Agardh (Rhodophyta, Ceramiales) in preparation for cultivation

Laurencia brongniartii is usually found at depths below 4 m, but can be found in shallow subtidal areas in crevices and on the walls of a coral reef in Amami Oshima Island, Kagoshima Prefecture, Japan, where irradiances were significantly lower than those at similar depths in open water. In preparation for the possible cultivation of this species for its antibiotic compounds, the effects of temperature and irradiance on photosynthesis and growth were measured. Photosynthesis and growth rates of L. brongniartii explants were highest at 26 and 28 °C, which closely corresponded to temperatures found during August to late December when it was most abundant. The estimated maximum photosynthesis rate (Pmax) was 4.41 μmol photon m−2 s−1 at 26 °C and 4.07 μmol photon m−2 s−1 at 28 °C. Saturating irradiance occurred at 95 μmol photon m−2 s−1 at 26 °C and 65 μmol photon m−2 s−1 at 28 °C. In contrast, growth experiments at 41.7 μmol photon m−2 s−1 caused bleaching of explants and the maximum growth rate observed during the study was 3.02 ± 0.75% day−1 at 28 °C and 25 μmol photon m−2 s−1. The difference in the saturating irradiance for photosynthesis and the irradiance that caused bleaching in growth experiments suggests that long-term exposure to high irradiance was detrimental and should be addressed before the initiation of large scale cultivation.

EFFECTS OF MACROALGAL TYPE AND WATER TEMPERATURE ON MACROALGAL CONSUMPTION RATES OF THE ABALONE HALIOTIS DIVERSICOLOR REEVE

Abstract The Japanese abalone “tokobushi” (Haliotis diversicolor Reeve) supports a valuable fishery off Tanegashima Island, southern Japan. However, catches have been declining, probably caused by over harvesting and other factors. Understanding the effects of macroalgal type and water temperature on the consumption rates of tokobushi has applications for the management of its population such as to identify sites with appropriate quality and quantity of macroalgae and the favorable water temperature during stock enhancement. Under controlled conditions, the effects of macroalgal type and water temperature on the macroalgal consumption rates of tokobushi were evaluated. On a short-term basis (24-h feeding), consumption rates were higher on leathery brown algae (Sargassum fusiforme, Sargassum patens, Sargassum duplicatum, Sargassum alternato-pinnatum, Undaria pinnatifida and Laminaria japonica), corticated red algae (Acanthophora spicifera, Gracilaria gigas, Carpopeltis affinis and Ceramium sp.) and foliose green algae (Ulva pertusa and Enteromorpha intestinales) than on siphonous green algae (Codium spp.) and filamentous green algae (Chaetomorpha crassa and Cladophoropsis zollingeri). Averaged across 20 species of macroalgae, the mean consumption rate was 4.96 ± 0.27%wet-TW.d−1 (wet alga and wet abalone; TW = total weight) or 1.37 ± 0.19%dryTW.d−1 (dry alga and dry abalone). On a long-term basis (20 days feeding), tokobushi had higher consumption rates on the green alga Ulva pertusa and the brown alga Sargassum fusiforme than on the red alga Meristotheca papulosa. When presented with a choice of species (3 days feeding), tokobushi ate more of the brown alga Sargassum fusiforme and the red alga Gracilaria gigas than the green alga Codium cylindricum. Consumption rates generally increased with temperature. Generally, tokobushi prefer macroalgae with high percent dry weight composition, most of which are brown and red algae, and eat more at water temperatures around spring/fall (17°C, 21°C) and summer (27°C) in Kagoshima, Japan.

Effect of temperature and irradiance on the uptake of ammonium and nitrate by Laurencia brongniartii (Rhodophyta, Ceramiales)

The effects of temperature (20, 24 and 28 °C) and irradiance (15 and 40 μmol photon m−2 s−1) on the nitrate and ammonium uptake rates of the subtropical red alga, Laurencia brongniartii, were investigated to prepare for tank cultivation. Nitrate uptake followed saturation kinetics and was faster at higher irradiances and temperatures. In contrast, ammonium uptake was linear over the experimental range and was not affected by an increase in temperature. A parameter, β, was calculated to compare substrate uptake rates of nitrate along the linear portion of the uptake curve with that of ammonium. For nitrate, β was lower at low irradiance and higher at high irradiance (β = 0.007 ± 0.003 and 0.030 ± 0.002 [μmol N L−1 (μmol N gww−1 d−)−1], respectively). However, β was 0.023 ± 0.002 and 0.034 ± 0.002 [μmol N L−1 (μmol N gww−1 d−1)−1] for ammonium, suggesting a preference for ammonium over nitrate.

In vitro promoting activity of human interferon β production by extracts of marine algae from Japan.

Two hundreds species of marine algae were investigated for in vitro promoting activity of human interferon β (IFN-β) production by poly(I:C)-induced human osteosarcoma cell line, MG-63. A brown alga, Sargassum hemipyllum promoted most its activity, showing more than 11-fold. When we attempted to partially purify the active substances by particular two-step chromatography, two peaks of active fractions were obtained. These fractioned materials exhibited the heat-stable and non-cytotoxic characters with the molecular weight less than 3000.

Taxonomic study of two Sargassum species (Fucales, Phaeophyceae) from the Ryukyu Islands, southern Japan: Sargassum ryukyuense sp. nov. and Sargassum pinnatifidum Harvey

Abstract Species of the genus Sargassum (Fucales, Phaeophyceae) belonging to the Schizophycus group (in subgenus Sargassum sensu lato) from the Ryukyu Islands, southern Japan, were morphologically reinvestigated, and two entities were recognized: Sargassum ryukyuense sp. nov. and Sargassum pinnatifidum. The new species is characterized by: 1) compressed primary branches; 2) simple lanceolate primary and lateral leaves with an undulate and dentate margin in all stages; 3) lateral branches issuing alternate-distichously on the main branches in one plane; 4) long and flattened receptacles arranged alternate-distichously on terminal branches; 5) main and lateral branches on the stem issuing as foliar expansions in the early stage of development; and 6) vesicles with a simple coronal leaf. This new species resembles S. pinnatifidum in features 1), 3) and 5). However, it differs from S. pinnatifidum in features 2), 4) and 6). Furthermore, this new species can be distinguished from all previously described species based on the complete set of diagnostic features above and by the presence of long lingulate receptacles with short stalks. The new species is known to be endemic in the Ryukyu Islands and adjacent waters of southern Japan.

Habitat characteristics and seasonal changes of Laurencia brongniartii (Ceramiales, Rhodophyta) in Kagoshima, Southern Japan

The seasonal change in size of Laurencia brongniartii was observed for the year 2002 at Banshobana Park, Satsuma Peninsula and Tsuchihama Beach, Amami Oshima, both in Kagoshima Prefecture, Japan. Additionally, the vertical distribution of this species was also studied at Tsuchihama Beach (second site), where the largest populations were found. Maximum lengths were observed in October ‐ November with a size of 100 ± 6 mm at Banshobana Park and 111 ± 5 mm at Tsuchihama Beach. Line‐transects conducted at Tsuchihama Beach, were analyzed to determine the vertical distribution of L. brongniartii due to depth and the slope of the substrate. Alga was found growing in areas restricted to low levels of light.

Correction to: Effects of salinity on the growth and mucous cells of the abalone Haliotis diversicolor Reeve, 1846

The original version of this article unfortunately contained a mistake.