Jean-Pierre Chanut

An Experimental Tool to Study the Effects of Ultraviolet Radiation on Planktonic Communities: A Mesocosm Approach

A mesocosm approach was adopted for the study of the impact of UV-B radiation on coastal planktonic communities. Experiments were conducted in eight land-based 1500 1 mesocosms. The 2.25 m deep mesocosms reproduced the whole euphotic zone and vertical mixing ensured a homogeneous water column. While maintaining all other physical characteristics the same, UV-B levels were manipulated in different mesocosms by either increasing UV-B with lamps or by eliminating it using Mylar® sheet as a filter. The resulting spectral irradiance regime produced in the mesocosms was characterised by the daily irradiance averaged over the water column. Incident irradiance was measured every 10 minutes using an International Light IL-1700 radiometer and a Biospherical PUV-511 radiometer. Underwater spectral irradiance for the different treatments was determined using a Biospherical PUV-500 profiling radiometer. One of the present challenges of UV-B research is the extrapolation of results from laboratory and short-term field ...

STRATE: a microcomputer program for designing optimal stratified sampling in the marine environment by dynamic programming—I. Theory and method

Abstract A method for delimiting strata boundaries in an optimal way using dynamic programming is described in mathematical terms. A computational procedure built around the Bellmans principle of optimality is presented. This procedure permits to determine the optimal strata boundaries and the associated values of the variance within each stratum using a minimum number of computation steps and space memories. Some criteria for computing the optimal number of strata and the optimal allocation of sampling units through the strata also are specified. For evaluating the stability of results, a sensitivity analysis is performed for a given level of precision in regard to the total sample variance. The usefulness and limits of this computation algorithm are discussed in the context of a marine experiment.