Associations of ostracods in shallow lakes in the northeast of La Pampa province (Argentina)

Romina Kihn,Santiago Andrés Echaniz,César Stella,Gabriela Cabrera,Alicia María Vignatti

doi:10.22179/revmacn.22.679

Abstract

Shallow lakes are common in the center of Argentina. Although many characteristics of its biota are known, information on the distribution and ecology of ostracods is scarce despite their importance as biological indicators and in actuopaleontology. The objective of this study was to determine the taxonomic composition, the density of ostracods, and their relationships with environmental parameters in lakes in the northeast of La Pampa. Five aquatic ecosystems were studied from September 2016 to March 2017. Samples of superficial sediments were collected, and conductivity, temperature, and transparency were measured in situ. Water samples were collected to determine salinity, pH, and ionic composition. The lakes differed in salinity, ionic composition, and transparency. Ten taxa were registered, some previously found in the province of Buenos Aires (Heterocypris similis, Heterocypris incongruens, Cypridopsis vidua, and Chlamydotheca incisa), the Llancanelo basin (H. incongruens and C. vidua), and North Patagonia lakes (C. incisa, C. vidua, Potamocypris unicaudata, H. incongruens, and Amphicypris argentiniensis). The influence of salinity was verified because some species (A. argentinensis, Limnocythere rionegroensis, and Limnocythere titicaca) were found only in the most saline lake. The existence in La Pampa of three different ecoregions (Pampean Plains, Espinal, and Patagonian Steppe) and the presence of ostracods in the studied lakes of northwestern Argentina (L. titicaca), the Buenos Aires province plain (H. similis, H. incongruens), and Patagonia (L. rionegroensis) allowed for affirming that the lakes of La Pampa are in a transition zone among different ostracods faunas.

Highlights

Most aquatic ecosystems of La Pampa Province are shallow lakes
Study area Ostracods from the following five aquatic ecosystems located in northeastern La Pampa were studied: La Tradicion East (LTE) (35° 17’ 57” S; 63° 37’ 36” W), La Tradicion West (LTW) (35° 17’ 43” S; 63° 37’ 52” W), Dos Molinos (DMo) (35° 22’ 20” S; 63° 36’ 19” W), Ustarroz (Ust) (35° 22’ 30”S; 63° 34’ 45” W) and El Bellaco (EBe) (35° 27’ 08” S; 63° 36’ 18” W) (Fig. 1)
Two ecosystems (Ust and LTW) could be considered saline lakes (Hammer, 1986), with a predominance of Cl, the analysis showed that LTW was relatively different because its salinity was much higher, which was reflected by the association of the species

Summary

Introduction

Most aquatic ecosystems of La Pampa Province are shallow lakes. Most of these ecosystems are saline lakes (TDS > 3 g/L (Hammer, 1986), in which Cl- and Na+ are the dominant ions. Many physical-chemical and biological characteristics of the lakes in La Pampa Province have been studied, but of the latter, the most attention has been given to phytoplanktonic and zooplanktonic communities (Echaniz & Vignatti, 2017; 2019; Echaniz et al, 2006; 2012; Vignatti et al, 2007). As the benthic community can be a useful tool to evaluate the characteristics of lakes, the study of ostracods has taxonomic, biogeographic, and ecological importance. Knowledge about living ostracods can be used in actuopaleontology studies to examine the evolution of lakes in the recent past (Laprida et al, 2006; DAmbrosio et al, 2017), especially considering the current scenarios of climate change (Barros et al, 2014)

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Conclusion