Fish and limnology of a thermal water environment in subtropical South America

• Published in: Environmental biology of fishes Vol. 51; no. 3; pp. 265 - 283
• Main Authors: MENNI, R. C, MIQUELARENA, A. M, GOMEZ, S. E
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01.03.1998; Springer Nature B.V
• Subjects: Acclimatization; Agnatha. Pisces; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; Field tests; Fish; Freshwater; Fundamental and applied biological sciences. Psychology; Geographical distribution; Habitats; Limnology; Pisces; Rainforests; Streams; Thermal water; Total dissolved solids; Vertebrata; Water temperature; South America; Argentina; America; Argentina, Jujuy, Agua Caliente; Freshwater environment; Limnology; Subtropical zone; Vertebrata; Temperature; Zoogeography; Thermal resistance; Animal community; Pisces; Stream; Thermal water; Adaptation
• ISSN: 0378-1909; 1573-5133
• DOI: 10.1023/A:1007445417647

Two thermal sources with water temperatures from 51 to 59°C flow into a stream of 2 to 5 m width and about 0.5 m depth at Agua Caliente (23° 44', 64° 38') in Jujuy province, Argentina. Data from 3 years sampling show that the influence of the thermal sources maintains the water temperature of the stream section at a high and constant level (from 24 to 35°C), different from the thermal regime of other streams in the area. Composition of water (N=13) has the following mean values: pH 8.36, conductivity 1591 µS cm^sup -1^, dominant ions (in mg l^sup -1^) CO^sub 3^ ^sup --^ 12.77, CO^sub 3^H^sup -^ 140.27, Cl^sup -^ 246.86, SO^sub 4^ ^sup --^ 460.14, Na^sup +^ 400.45, K^sup +^ 2.18, Ca^sup ++^ 27.68 and Mg^sup ++^ 2.14. Mean total dissolved solids: 1.3 g l^sup -1^. Large amounts of SO^sub 4^ ^sup --^, Na^sup +^, and Cl^sup -^ Sixteen fish species (2460 specimens) were captured in the warmed reach. Dominant families were Characidae, Cichlidae and Loricariidae. New geographic distribution information is provided for eight species, some of them with restricted northwestern Argentina distributions. Most abundant species were the eurytopic characid Astyanax bimaculatus, followed by the cichlid Bujurquina vittata. These species have the highest critical thermal maximum according to field experiments. Temperature of acclimatization is closer to lethal than in fishes from 'normal' habitats. Agua Caliente differs from other thermal habitats in the lack of isolation, its placement in a rain forest area, a high number of species, and the lack of cyprinodontoids. The fish fauna here represents an opportunistic invasion of a habitat with water parameters strongly different from those in the area, particularly temperature and salinity. Both faunistic and limnological traits make of Agua Caliente a new type of environment within the subtropics.[PUBLICATION ABSTRACT]