Distribution and abundance of hyperiid amphipods in relation to summer mesoscale features in the southern Gulf of Mexico

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Seventy-one hyperiid species were identified from 97 zooplankton samples collected in the southern Gulf of Mexico during July 1988. About 91% of the adult individuals belonged to five species: Lestrigonus bengalensis (86.56% of total hyperiid numbers), Anchylomera blossevillei (1.20%), Phronimopsis spinifera (1.05%), Hyperioides longipes (1.00%) and Hyperietta vosseleri (0.99%). Overall, up to 74% of the hyperiids were collected at night, although a reverse migration was observed in the anticyclones. The mean abundance was 5-fold higher at the neritic stations than in the oceanic areas. This tendency was even more marked at night. Night samples yielded about the same number of species as during the daytime (56 taxa versus 61). Four mesoscale features (two anticyclones, one cyclone and one upwelling) characterized the oceanic mesoscale circulation in the surveyed area. The abundance of the oceanic hyperiid community showed significant differences related to some of the mesoscale features active in the area, i.e. the abundance in the Lazy Eddy anticyclone was lower than that in the cyclone (day and night). Overall, the upwelling areas showed a tendency to have higher abundances than the downwelling features (anticyclones). Cluster analysis indicated neritic-oceanic differences rather than mesoscale feature-related differences in the local hyperiid community. The neritic community showed differences that were attributed to the effect of upwelling. The summer and spring hyperiid communities had important differences in the same area, thus suggesting a seasonal succession of the gulf hyperiid community. eng

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