Summary A total of 74 independently run bioassays with soil incorporated metsulfuron‐methyl from 12 different laboratories was analysed by a logistic dose‐response curve to assess the precision of regression parameters and relate ED50 to soil properties. The potency in terms of ED50 of metsulfuron‐methyl in Brassica rapa L., which was used by all laboratories, varied between 0.05 and 3.9 g a.i. ha‐1. ED50 was negatively correlated with pH and positively correlated with organic matter. The majority of laboratories had ED50 within the interval 0.1‐1.0 g a.i. ha‐1. At one laboratory using three test species, the most sensitive species was Beta vulgaris L. followed by Brassica rapa L. and Lepidium sativum L. The coefficients of variation were smallest for the ED50 and ED90 response levels and largest for the ED10. The slope of the response curves had considerably lower coefficients of variation than the EDs. The results are discussed in relation to a previous collaborative bioassay study. Finally it is suggested that standardization of bioassays with herbicides could be achieved in the same way as standardization of chemical analyses.

The primary productivity of an area of inshore sea in the South Orkney Islands was measured using in situ techniques in two consecutive seasons. Liberation of extracellular products of photosynthesis occurred, accounting for about 1 % of the total carbon fixed at the depth of maximum photosynthesis but rising to 38 % or more when photosynthesis was inhibited at high light intensities.

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