were calculated over the total array of individuals in a sample, excluding carnivores
(which does give the diagram only three axes, but seems unfortunate; we would like
to know the relative importance of carnivores). Each basis of classification (motility,
feeding stratum) was analyzed separately. The results show that sessile modes are less
common than either motile or discretely motile modes among sediment-dwelling
polychaetes of the shelf. Only one sample from the coastal survey showed a
predominance of sessile worms. In deep continental-basin sediments all three motility
modes were represented (points near the triangle center), while the abyssal sample
was evenly split between motile and discretely motile worm species, but almost no
species were fully sedentary. In other words, sessile habit is most common at mid-
depths. Filter-feeding is a strategy of relatively few individuals in soft sediments at all
depths. On coastal bottoms, assemblages vary from all surface deposit-feeding to all
burrowing, including all combinations between.
Fig. 14.13 Ternary diagrams for samples from the continental shelf off southern
California. (a) Stations are located in the diagram according to the proportions of
discretely motile (πD), motile (πM), and sessile (πS) polychaete worms. (b) Stations are
located according to proportions of surface feeding (πS′), burrowing (πB), and filtering
(πF) polychaetes.
(^) (After Jumars & Fauchald 1977.)
Fig. 14.14 Ternary diagrams like those in Fig. 14.13, only for deep-water samples in
the Santa Catalina Channel, San Diego Trough, and central North Pacific.
(After Jumars & Fauchald 1977.)