Naho Horimoto

A phytoplankton absorption-based primary productivity model for remote sensing in the Southern Ocean

Recent global environmental changes such as an increase in sea surface temperature (SST) are likely to impact primary productivity of phytoplankton in the Southern Ocean. However, models to estimate net primary production using satellite data use SST and uncertain estimation of chlorophyll a (chl-a) concentration. A primary productivity model for satellite ocean color data from the Southern Ocean, which is based on the light absorption coefficient of phytoplankton to reduce uncertainties of sea surface chl-a estimations and bias in optimal values of chl-a normalized productivity derived from SST, has been developed. The new model was able to estimate net primary productivity in the water column (PPeu) without dependency on temperature when in the range of −2 to 25°C, and it explained 51% of the observed variability in PPeu with a root mean square error (RMSE) of 0.15. Application of the model revealed that the SST dependent model has overestimated PPeu in warmer waters around the Subtropical Front, and underestimated PPeu in colder waters poleward of the Sub-Antarctic Front. This absorption-based primary productivity model contributes to a study of the relationship among spatio-temporal variations in the physical environment, and biogeochemical cycles in the Southern Ocean.

Developing Partnerships with the Community for Coastal ESD.

Purpose – The purpose of this paper is to draw lessons for developing community‐university partnerships from experiences in promoting coastal education for sustainable development (ESD).Design/methodology/approach – Qualitative data collected from two coastal community outreach projects were analyzed.Findings – The outreach projects improved the relationship between university and community members. It is important to conduct interviews at the early stages of the projects to understand the needs of the community and set project outcomes to meet community‐defined priorities. The most effective means for promoting an ESD program based upon community‐university partnerships is to reach out to and network with local individuals who have been active in community projects and embed the program concept into the activities of those individuals. Mediators who link the academic community with the local community are helpful in promoting the partnerships, and university students were found to be successful mediators...

A practical method for sensitive determination of the fluorescent water-tracer uranine by reversed phase HPLC under alkaline conditions.

A stable and highly sensitive HPLC method for uranine has been developed. Because of unstableness of silica-based octadecyl-C18 columns at high pH condition, a reversed phase HPLC analysis under alkaline conditions has not necessarily taken as a usual method. However, the application for uranine seems to be advantageous, since the fluorescence yield of uranine is markedly enhanced at high pH condition. The detection limit of the HPLC system was 0.9 pg. The analytical consideration was also paid for the solid phase extraction (SPE) prior to the HPLC analysis with careful consideration of the recently revised pK(a) values of uranine. The recovery rate of uranine by SPE was found to depend on the sample volume and a few ml of seawater was applied to SPE in order to maintain the recovery rate during SPE. A combination of HPLC and SPE methods achieved detection of uranine at concentrations as low as 0.2 ng l(-1) (0.5 pM), which was comparable to the background concentration of uranine in coastal water off Japan. For the practical use of the detected tracer-uranine concentration values after substantial duration after release, the photodegradation of uranine in surface water was also evaluated in terms of incident solar radiation dose as an exponential rate constant of -0.135 mol photon(-1)m(2).