(^) Mesozooplankton in the NPSG are a diverse array despite their low population
biomass, with around three-fold more species than are found at higher latitudes.
McGowan and Walker (1979), referring primarily to copepods, raised the issue of
how so many species can persist together with so few obviously differing niches. The
distinctive roles seem to sum up as: (i) eat particles, or (ii) eat each other. As
ecologists steeped in the “Law of Competitive Exclusion”, our expectation is that the
system should simplify to just a few kinds in each role by competitive extinctions.
The answer will never be complete, but part of it is that species with similar trophic
roles, represented in the data by species in the same genera of copepods, are dispersed
vertically (Longhurst 1985 – actually referring to the eastern Pacific equatorial zone;
Ambler & Miller 1987 – in the CLIMAX region). Congeners tend to separate into
different depth levels.
(^) Like all ocean areas, the subtropical gyres have stocks of nekton in a substantial
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