Fig. 13.15 A species–area curve for benthic infauna from the Helgoland Bight of the
Baltic Sea. The fitted curve shows that two grabs will typically capture 60% of the
total fauna, seven grabs 90%.
(^) (After Gerlach 1972.)
(^) The bracketed quantities in the ratio represent combinations of N items taken in
groups of size n. Hurlbert (1971) actually suggested this formula, showing that
Sanders’ original calculation overestimated expected S at any given n. Comparing
whole curves of E(S) vs. n avoids the problem that, since slope (equitability) and
asymptote (S) interact, quite different samples can give the same E(Sn) at a given
sample size, n. Nevertheless, E(S 100 ) and other E(Sn) (occasionally with n < 15) have
been used to compare diversity between sites. Rarefaction curves remain uniquely
popular among benthic ecologists.
(^) One study (Grassle & Maciolek 1992) that came perhaps as close as possible to
documenting fully the diversity in the deep sediment of a single region in a narrow
range of depth was conducted along the coast of New Jersey, USA. A suite of box