Branchinecta Gaini Daday, 1910 (Branchiopoda, Anostraca) As a Bioindicator of Oligotrophic and Low Conductivity Shallow Ponds in Southern Chilean Patagonia

BRANCHINECTA GAINI DADAY, 1910 (BRANCHIOPODA, ANOSTRACA) AS A BIOINDICATOR OF OLIGOTROPHIC AND LOW CONDUCTIVITY SHALLOW PONDS IN SOUTHERN CHILEAN PATAGONIA

PATRICIO DE LOS RÍOS1,3), D. CHRISTOPHER ROGERS2,4) and NELSON RIVERA1) 1) Universidad Católica de Temuco, Facultad de Recursos Naturales, Escuela de Ciencias Ambientales, Casilla 15-D, Temuco, Chile 2) Ecoanalysts, 1307 L Street, Davis, CA 95616, U.S.A.

ABSTRACT

The south of Patagonia is characterized by its semi-arid weather and numerous small, temporary and permanent shallow ponds. The aquatic crustaceans of these water bodies are characterized by their endemism and species richness. The present study was done in the surroundings of Punta ◦ Arenas (53 S, Chile), and included six shallow ponds. Samples for conductivity, total dissolved solids, chlorophyll, and crustacean zooplankton as well as littoral species of crustacea were collected. Our study revealed that Branchinecta gaini Daday, 1910 occurred at low conductivity (0.55 mS/cm), and low total dissolved solids (0.28 g/l) and chlorophyll (2.70 μg/l) concentrations, such compared to sites without fairy shrimp populations, that had signiﬁcantly high conductivity (3.58 mS/cm), and high total dissolved solids (1.80 mg/l) and chlorophyll (12.80 μg/l) concentrations. The results partially agree with the ﬁrst descriptions of Patagonian water bodies that indicated the presence of fairy shrimps in low conductivity waters. The observations of the presence of B. gaini and other associated microcrustaceans are similar to descriptions of unpolluted water bodies in Antarctica, and those results would support the observations of the present paper. Other reports on fairy shrimp habitats mentioned a wide range of both salinity and trophic status. Other ecological and biogeographical topics on fairy shrimps are also discussed.

RESUMEN

La zona sur de la Patagonia se caracteriza por su clima semi-árido, y presenta numerosas lagunas poco profundas, ya sea superficiales o permanentes. La fauna acuática de estos ecosistemas se caracteriza por su alto endemismo y riqueza de especies. El presente estudio se realizó en las ◦ cercanías de la ciudad de Punta Arenas (53 S, Chile), y este incluyó seis pequeñas lagunas superficiales. Se colectaron muestras para análisis de conductividad, sólidos totales disueltos, clorofila

3) e-mails: [email protected] or [email protected] 4) e-mail: [email protected] © Koninklijke Brill NV, Leiden, 2008 Crustaceana 81 (9): 1025-1034 Also available online: www.brill.nl/cr DOI:10.1163/156854008X360789 1026 P. DE LOS RÍOS, D.CH. ROGERS & N. RIVERA y crustáceos zooplanctónicos y litorales. El presente estudio reveló que la especie Branchinecta gaini Daday, 1910 fue observada en condiciones de baja conductividad (0,55 mS/cm), sólidos totales disueltos (1,80 g/l) y baja concentración de clorofila (2,70 μg/l); valores notablemente bajos en cuanto a la conductividad (3,58 mS/cm), sólidos totales disueltos (1,80 g/l) y concentración de clorofila (12,80 μg/l) observados para sitios sin poblaciones de Branchinecta. Los resultados observados concuerdan parcialmente con las primeras descripciones para la zona sur de la Patagonia. La presencia de B. gaini y otros microcrustáceos asociados es similar a las descripciones para cuerpos de aguas continentales prístinos de la Antártica. Los resultados publicados para otros biotopos de camarones duende denotan un amplio gradiente de salinidad y condiciones tróficas. Se discutieron tópicos ecológicos y biogeográficos.

INTRODUCTION The south of Patagonia (51-53◦S), is characterized by its cold and semi-arid climate and by the presence of numerous permanent and temporary shallow ponds, that have a wide range of conductivity and trophic status (Soto et al., 1994; Soto & De los Ríos, 2006). The aquatic crustaceans of these ecosystems are characterized by their marked endemism and a relatively high species richness under conditions of low and moderate conductivity (Soto et al., 1994; De los Ríos, 2005; De los Ríos & Contreras, 2005; Soto & De los Ríos, 2006). These patterns are similar to descriptions for sub-Antarctic islands in the South Atlantic (Hannsson et al., 1996; Pugh et al., 2002; Dartnall, 2005). The aquatic crustacean assemblages of southern Patagonian water bodies show a marked dominance of calanoid copepods of the genus Boeckella,whichis represented by many species (Modenutti et al., 1998; De los Ríos, 2005; Soto & De los Ríos, 2006). The main regulating factors of this assemblage are conductivity and chlorophyll concentration, because at oligotrophy and low to moderate conductivity the calanoids are dominant, whereas in mesotrophy and low conductivity, daphniids (Cladocera, Daphniidae) are abundant (Soto & De los Ríos, 2006) and ﬁnally, at high conductivity, the anostracan, Artemia persimilis (Piccinelli & Prosdocimi, 1968) is the dominant species (Campos et al., 1996; De los Ríos, 2005). Among the species described from zooplankton assemblages at low conductivity, the presence of the fairy shrimps, Branchinecta spp., has been reported (De los Ríos, 2005). Currently, there is only a scarce literature about Chilean fairy shrimp populations, as the available literature only described the presence of species of the genus Branchinecta, for southern Patagonian shallow ponds (Soto, 1990; De los Ríos, 2005). However, there are also descriptions of fairy shrimp populations in Antarctic water bodies (Campos et al., 1978; Peck, 2004, 2005). Those results agree with the descriptions of Brték & Mura (2000) and Belk & Brték (1995), that indicate the exclusive presence of the genus Branchinecta for southern South America as far Anostraca are concerned. According to the descriptions of De los