We measured the C/N ratio and ␦ 15 N values of two brown macroalgae-Padina spp. and Dictyota sp., which are distributed over all the subtropical fringing reefs of the Ryukyu Islands, Japan-to evaluate the feasibility of these algae as indicators of the terrestrial nitrogen load to the reef. The correlations between the distance from the shoreline and algal C/N ratio and surrounding NO concentrations were not clear, although their average values among the Ϫ 3 reefs seemed to indicate differences in nitrogen loadings from the land. The ␦ 15 N values of these algae, on the other hand, linearly or curvilinearly decreased from ϩ8‰ to ϩ2‰ with increasing distance from the shoreline, indicating the difference in nitrogen sources available to macroalgae. The slope of the decline among eight study areas had different characters, which seemed to depend on the residence time of reef seawater and the fluxes of terrestrial nitrogen. Using ␦ 15 N values of brown algae as an indicator, we confirmed that primary producers, such as macroalgae on the reefs, assimilated land-derived nitrogen and successfully evaluated time-integrated effects of terrestrial nitrogen on coral reef algae, which had been missed by conventional monitoring of the water column nutrients.Direct anthropogenic influences on coral reefs are major concerns because the global population is increasing, especially in tropical and subtropical countries with coral reefs. Furthermore, coral reefs are threatened by global climate

Since radioiodination of human granulocyte colony-stimulating factor (G-CSF) is difficult, we synthesized a mutein of human G-CSF that retains full biological activity and receptor-binding capacity for at least 2 weeks after radioiodination. Receptors for human G-CSF were characterized in the plasma membrane fraction from the human term placenta (human placental membranes) and trophoblastic cells by using the III-labeled mutein of human G-CSF (KW-2228). The specific binding of III-labeled KW-2228 to placental membranes was pH-dependent, with maximal specific binding at pH 7.8; it increased linearly with protein to 3.7 mg of protein per ml and was both time-and temperature-dependent, with maximal binding at 4°C after a 24-hr incubation. When we examined the ability of hematopoietic growth factors to inhibit 2-5I-labeled KW-2228 binding, we found that KW-2228 and intact human G-CSF inhibited '25I-labeled KW-2228 binding, whereas erythropoietin or granulocyte-macrophage colonystimulating factor did not. Scatchard analysis revealed a single receptor type with a Bn,,., of 210 fmol/mg of protein and a Kd of 480 pM. The human G-CSF receptors on human placental membranes were shown to consist of two molecular species of 150 kDa and 120 kDa that could be specifically cross-linked to

Abstract. Macroalgal beds have drawn attention as one of the vegetated coastal ecosystems that act as atmospheric CO2 sinks. Although macroalgal metabolism as well as inorganic and organic carbon flows are important pathways for CO2 uptake by macroalgal beds, the relationships between macroalgal metabolism and associated carbon flows are still poorly understood. In the present study, we investigated carbon flows, including air–water CO2 exchange and budgets of dissolved inorganic carbon, total alkalinity, and dissolved organic carbon (DOC), in a temperate macroalgal bed during the productive months of the year. To assess the key mechanisms responsible for atmospheric CO2 uptake by the macroalgal bed, we estimated macroalgal metabolism and lateral carbon flows (i.e., carbon exchanges between the macroalgal bed and the offshore area) by using field measurements of carbon species, a field-bag method, a degradation experiment, and mass-balance modeling in a temperate Sargassum bed over a diurnal cycle. Our results showed that macroalgal metabolism and lateral carbon flows driven by water exchange affected air–water CO2 exchange in the macroalgal bed and the surrounding waters. Macroalgal metabolism caused overlying waters to contain low concentrations of CO2 and high concentrations of DOC that were efficiently exported offshore from the macroalgal bed. These results indicate that the exported water can potentially lower CO2 concentrations in the offshore surface water and enhance atmospheric CO2 uptake. Furthermore, the Sargassum bed exported 6 %–35 % of the macroalgal net community production (NCP; 302–1378 mmol C m−2 d−1) as DOC to the offshore area. The results of degradation experiments showed that 56 %–78 % of macroalgal DOC was refractory DOC (RDOC) that persisted for 150 d; thus, the Sargassum bed exported 5 %–20 % of the macroalgal NCP as RDOC. Our findings suggest that macroalgal beds in habitats associated with high water exchange rates can create significant CO2 sinks around them and export a substantial amount of DOC to offshore areas.

No abstract

No abstract