ABSTRACT: To approach the aims of the German research project PRISMA, an integrated measurement strategy was developed, following the nesting principle: (i) drift experiments which involved sampling in a defined water mass aiming at the analyses of transfer and transformation processes were supplemented by (ii) analyses at 3 equidistant drifting positions 3 n.m. (nautical miles) apart, which were performed in (iii) a grid of equidistant stations at fixed positions 10 n.m. apart, covering the German Bight, to identify hydrodynamic and biogeochemical changes or interferences affecting the drift area. In this way, the spatial representativeness of frequent point measurements at drifting stations could be estimated, as well as the short-term variability during the 4 d duration of each grid survey in the German Bight. The latter also provided data sets for transport modelling. In addition time series data were collected at 6 mooring stations equipped with current meters, CTD and transmission meters. Some of the modelling was already performed during the experiment with a daily operational model (used by BSH, Bundesamt für Seeschiffahrt und Hydrographie, Hamburg) comprising atmospheric and ocean models. The output provided nearly real-time information on the drift direction of the defined water masses. The results of more extensive model calculations allowed the subsequent description of water mass transports in different depths of the German Bight. A great number of samples were taken for the estimation of bulk parameters in order to define the status of the ecosystem. Taking account of the time and position of these measurements, selected samples were processed for the analysis of contaminants, which required more effort. Some examples are discussed that illustrate the advantages and disadvantages of the measurement strategy. These focus mainly on hydrographic measurements and nutrient data, reflecting the dominant biological processes investigated during PRISMA.

KEY WORDS: Measurement strategy · Drift experiment · Nitrate

Published in MEPS Vol. 156 (1997) on September 25
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997