The life cycle, seasonal dynamics and production of two populations of Streblospio species (Annelida: Polychaeta), S. benedicti Webster, 1879, from muddy sediments of the Great Sippewissett Salt Marsh (southern New England, USA), and S. shrubsolii (Buchanan, 1890), from muddy areas of the Alfacs Bay (north-eastern Spain), were studied from November 1986 to September 1988. Both species have life-cycles shorter than one year. The American population showed a unimodal distribution most of the year while in the European population polymodal distributions were common. Average density of S. benedicti over the two-year period ranged from 24,086 to 677 individuals m−2 (annual average 4,554). The observed numbers of S. shrubsolii ranged from 65,668 to 2,579 individuals m−2 (average 35,311). The biomass of the American population ranged from 2·1 to 0·04g dry weight m−2 (average 0·5). The values obtained for the European population ranged from 5·9 to 0·1 g dry weight m−2 (average 4·1). Secondary production was higher in the European population (15·65 g dry weight m−2 y1) than in the American population (3·0 g dry weight m−2 y−1). Production to mean biomass ratios were 4·4 y−1 for S. shrubsolii and 5·4 y−1 for S. benedicti. Population densities are compared with previously published data for other Streblospio populations.

16 páginas, 2 tablas, 7 figuras

Peer reviewed