Population dynamics and production of &lt;i&gt;Streblospio benedicti&lt;/i&gt; (Polychaeta) in a non-polluted estuary in the Basque coast (Gulf of Biscay)

Loreto García-Arberas,Ana Rallo

doi:10.3989/scimar.2004.68n2193

Abstract

Population dynamics and production of a population of Streblospio benedicti from the Gernika estuary (Basque coast, Gulf of Biscay) were studied monthly for one year, from May 1991 to May 1992. S. Benedicti was present in the muddy sand community of Gernika throughout the period of study except in March, when it all but disappeared. Continuous recruitment was observed throughout the year, even though it was stronger in autumn. Abundance fluctuations were principally due to the incorporation of recruits and so the highest density in Gernika was recorded in autumn, and the lowest in spring, with an annual mean of 6346 ± 4582 ind m -2 . The same pattern of seasonal variation was shown in biomass: the annual mean biomass of S.benedicti in Gernika was estimated at 0.80 ± 0.54 g dry weight m-2. Secondary production was 3.57 g dry weight m-2 year, giving a P/B ratio of 4.46. S. benedicti in Gernika behaved similarly to those described for Mediterranean Streblospio populations as regards practically continuous recruitment, but the number of individuals and the annual average density were considerably lower on the Basque coast.

Highlights

The estuary of Gernika (Basque Country, northern Iberian Peninsula) has a high botanical and faunistic diversity with a wide variety of aquatic and terrestrial habitats
With regard to the benthos, most of the studies in the Gernika estuary have been done on molluscs (Navarro et al, 1989; Borja, 1991; Soto et al, 1996), but the ecology and STREBLOSPIO DYNAMICS AND PRODUCTION 193 distribution of other benthic taxa are poorly known
To evaluate the recruitment of S. benedicti in Gernika, we considered the presence of individuals in meiofauna samples and the number of individuals from the smaller size classes of macrofauna

Summary

Introduction

The estuary of Gernika (Basque Country, northern Iberian Peninsula) has a high botanical and faunistic diversity with a wide variety of aquatic and terrestrial habitats. It is an important over-wintering and migratory site for birds. With regard to the benthos, most of the studies in the Gernika estuary have been done on molluscs (Navarro et al, 1989; Borja, 1991; Soto et al, 1996), but the ecology and STREBLOSPIO DYNAMICS AND PRODUCTION 193 distribution of other benthic taxa are poorly known. Streblospio benedicti Webster, 1879 has a widespread distribution in the intertidal muddy sand areas of the Gernika estuary, where it is one of the most abundant polychaete species, mainly in fine sediments with a relatively high organic matter content

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Discussion

Conclusion