Euphausiacea
Diversity

Euphausiid species richness in the South Atlantic is lowest amongst southern assemblages. However, there is no clear increase to the equator as might intuitively be expected, and peaks in diversity are associated with the regions off Brazil and southern Africa (35°S). While it is tempting to dismiss this pattern as an artifact of the distribution of effort in the region, it does stress the effects of mixing between water masses and serves to identify transition zones (Boltovskoy, 1986). This is highlighted in the waters off southern Africa where species-rich subtropical assemblages in the Agulhas Current are supplemented with species from surrounding warm and cold temperate waters (Gibbons et al., 1995; Gibbons and Hutchings, 1996). This happens to a lesser extent in the regions off southern Brazil where tropical and subtropical assemblages in the Brazil Current are supplemented with warm temperate components from further south (Latitudinal distribution )

Although the estimation of sampling effort has been made from the same data used in the construction of Schem. map of zoogeographic it should be noted that cruises dedicated to the study of individual species have been ignored. In instances where authors have repeatedly visited particular grids through time, each visit has been logged separately. However, where several samples have been made from the same grid during the same cruise, only one record has been made here. It should be further noted that only records of euphausiid catches have been entered, thus areas sampled but without catches have not been included. Data therefore represent estimates of minimum effort. Data south of 60°S are very approximate as the literature in this region has not been thoroughly examined.

One further pattern not illustrated is the difference in euphausiid species richness between oceanic and coastal communities. Coastal euphausiid assemblages are generally less diverse than those of the neighbouring ocean, because few species are able to tolerate the frequently variable environments encountered there. Local increases in the richness of coastal euphausiid assemblages may accompany movements of oceanic water inshore, but this is generally short-lived and the elevated diversity fails to persist. This can be most clearly seen by the greater species richness on the narrow shelf at the Cape of Good Hope (13 species, Gibbons et al., 1995) compared to regions further north along the southern African coast (5 species).

Characteristic species of the zoogeographic provinces identified in Schem. map of zoogeographic:
Eu table 2
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