Collection and Analysis of Underway Data and Related Physical Measurements

Our ability to describe and understand the marine environment is limited both by the type and detail of the environmental data we can acquire, and by the power and resolution of the analysis methods we can apply to that data. Much of our recent understanding of the spatial variability in the planktonic community has been achieved from the analysis of series of essentially continuous measurements, taken either at a point in space or along a vertical or horizontal line. For a few parameters, well-established methods allow resolution of spatial structure over all length scales from centimeters to thousands of kilometers. Measurements of physical (and some chemical) scalar variables (e. g. temperature and salinity) provide the best examples. However, for biological parameters, many of the desired spatial “windows” (see Angel, 1977) are less adequate. Because these windows have in general been opened only recently by new methodologies, their technical limitations are poorly known. They also tend to be narrower (Figure 1) and yield data that are even more subject than the physical scalars to the confounding effects of variations that occur along the temporal and unsampled spatial axes. For this reason various authors (e. g. Denman, 1976) have suggested that one-dimensional sampling schemes are inadequate to describe the spatial structure fully. As discussed in the introductory chapter (Steele), horizontal structure often cannot be separated from vertical structure, either observationally or in terms of operative mechanisms, and there is a serious need for the collection of continuous biological, physical and chemical data in both dimensions simultaneously.