Intercomparision of 234 Th measurements in both water and particulate samples was carried out between 15 laboratories worldwide, as a part of GEOTRACES inter-calibration program. Particulate samples from four different stations namely BATS (both shallow and deep) and shelf station (shallow) in Atlantic and SAFE (both shallow and deep) and Santa Barbara station (shallow) in Pacific were used in the effort. Particulate intercalibration results indicate good agreement between all the participating labs with data from all labs falling within the 95% confidence interval around the mean for most instances. Filter type experiments indicate no significant differences in Th from decay and large in-growth corrections as a result of long gap between sample collection and processing.
During summer 2007, Arctic microphytobenthic potential primary production was measured at several stations around the coastline of Kongsfjorden (Svalbard, Norway) at B5 m water depth and at two stations at five different water depths (5, 10, 15, 20, 30 m). Oxygen planar optode sensor spots were used ex situ to determine oxygen exchange in the overlying water of intact sediment cores under controlled light (ca. 100 lmol photons m -2 s -1 ) and temperature (2-4°C) conditions. Patches of microalgae (mainly diatoms) covering sandy sediments at water depths down to 30 m showed high biomass of up to 317 mg chl a m -2 . In spite of increasing water depth, no significant trend in ''photoautotrophic active biomass'' (chl a, ratio living/dead cells, cell sizes) and, thus, in primary production was measured at both stations. All sites from B5 to 30 m water depth exhibited variable rates of net production from -19 to ?40 mg O 2 m -2 h -1 (-168 to ?360 mg C m -2 day -1 ) and gross production of about 2-62 mg O 2 m -2 h -1 (17-554 mg C m -2 day -1
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