intrudes around Point Barrow from the Bering Strait area, carrying phytoplankton
from the rich production over the Bering Sea shelf. This flow is almost certainly a
source of enriching organic matter for the underlying sediments, a food source.
Fig. 14.1 Station positions ( ), bathymetric contours (dashed lines), and numerical
abundance of polychaetes (number of worms m−2, solid lines) on the western Beaufort
Sea shelf and slope.
(^) (After Bilyard & Carey 1979.)
The next pass was to identify and count all of the species of polychaetes in each of
the samples, generating a book of data-sheets (Fig. 14.2). This part of the work can be
a monumental task. Examining animals one by one, sometimes seta by seta, for all 24
samples took over two years. Such an effort is not for those in an overwhelming hurry
to publish. Data for any one station are not in themselves very informative. However,
comparison of data for all the stations can be. What Bilyard had after his long
taxonomic interlude was a large table with two axes, species by stations, filled with
abundance estimates. The art of community analysis is to extract a maximum of
information from the matrix. It is useful first to simplify it in several ways. Bilyard
began by changing all the abundances to “1” for present and “0” for absent, then
ordered the species according to presence and absence progressing down the depth
gradient (Fig. 14.3).
Fig. 14.2 Actual data-sheet, showing logarithmic data transform, from Gordon
Bilyard’s analysis of Beaufort Sea polychaete species abundance.
(^) (Courtesy of Gordon Bilyard.)