Journal of Environmental Biology

Chaetognatha in the Bah?a Magdalena lagoon complex, Baja

California Sur, m?xico: Species composition and assemblages

Author Details

M.S. Cota Meza (Corresponding author)

Centro Interdisciplinario de Ciencias Marinas (CICIMAR-IPN). Laboratorio de Plancton y Ecolog?a

Marina. A. P. 476, La Paz BCS, M?xico

e-mail: mcota@ipn.mx

Publication Data

Paper received:

31 August 2009

Revised received:

17 July 2010

Accepted:

23 September 2010

Abstract

The chaetognaths from 187 zooplankton samples collected from the Bah?a Magdalena lagoon complex, Baja California Sur, M?xico during March, June, July, August, September, November, and December 1982 were studied. Twelve species belonging to two genera were identified. Sagitta euneritica and S. enflata were the most abundant and most frequent species with maximum abundance? in July (40,000 org/100 m³ and 6100 org/100 m³ respectively). Sagitta pacifica, S. regularis and S. pseudoserratodentata were stenothermic (21 to 25^oC), whereas the rest of the species were eurythermic (15.5 to 29.5^oC). Sagitta euneritica contributed considerably to the zooplanktonic biomass, increasing the density in particular in Bah?a Almejas.? The analysis of the species assemblages (Morisita index) showed that S. pacifica and S. regularis interact more frequently in August when there is a change of the water masses that converge in this zone during summer, when the California Countercurrent predominates. The composition of taxa during winter is characterized by the dominance of S. euneritica. Entering the warm period, an abrupt change occurs in taxa composition of the three zones studied: channels, Bah?a Magdalena, and Bah?a Almejas. The amplitude and distribution of S. peruviana was influenced possibility by the oceanographic conditions of ENSO 1982.

Key words

Chaetognaths assemblages, Seasonality, ENSO, Bahia magdalena, Mexico

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