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Blog: Radially Aligned Linear Photosynthetron - 9 March

In the back of Karl Safi’s lab, where we found him working in the semi-dark, is a very futuristic looking piece of kit called the Radially Aligned Linear Photosynthetron (RALPH).

Karl Safi, NIWA, at work in the C14 lab after a CTD deployment.
Sadie Mills, NIWA

RALPH is used to measure surface primary production in water collected by the CTD deployments at up to six selected depths.

Each chamber in the RALPH contains 12 small bottles that are exposed to different light regimes the further they are from the light in the middle of the machine. Each chamber has samples from a different water depth in it. Karl uses C14, a radioactive tracer for the fixation of carbon (uptake of CO2) by phytoplankton in the water samples. The RALPH system gives Photosynthetic Irradiance curves, which allow the microbial team to compare to the instantaneous results coming from Andres’s FRRF instrument (the Fast Repetition Rate fluorometer) that we mentioned in an earlier blog (15th Feb).

CTD water samples lined up inside one of the chambers of the RALPH system ready for analysis.
Sadie Mills, NIWA