Growth,abundance, morphometric and metabolic parameters of three populations of Diplodon chilensis subject to different levels of natural and anthropogenic organic matter input in a glaciar lake of North Patagonia |
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| Institution: | 1. Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales-IQUIBICEN CONICET, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, Pab. II, Ciudad Universitaria, 1428 Buenos Aires, Argentina;2. Instituto de Investigaciones Marinas y Costeras (IIMyC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata (UNMDP), CC 573 Correo Central (B7600WAG), Mar del Plata, Argentina;3. Laboratorio de Ecotoxicología Acuática, INIBIOMA(CONICET-UNCo) – CEAN, ruta provincial N° 61, km 3, CCP 7, Junín de los Andes, 8371 Neuquén, Argentina |
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| Abstract: | Three populations of Diplodon chilensis (Hiridae, Bivalvia) from North Patagonia (Lacar lake, Argentina) have been studied to determine how organic matter (OM) influence their growth, density, morphometric and metabolic parameters in two pristine sites (Yuco and Nonthué) and in a growing touristic locality (San Martín de los Andes Bay, site SMA) affected by urban discharges. In Nonthué (chemical and biological oxygen demand ratio COD/BOD ratio of 4.7), a dense neighboring forest provides higher quantities of vegetal detritus compared to Yuco, while in SMA the OM input increase is related to anthropogenic impact, mainly sewage discharges, which is more biodegradable (COD/BOD ratio of 1.7). Our results show that population's size distribution and growth rates are affected positively by increased OM, independently of its natural or anthropogenic origin. The modal shell length interval for SMA and Nonthué is two-fold higher (70 mm), in agreement to the growth rate increase (k = 0.079), compared to Yuco (35 mm, k = 0.045). The morphometric relationships between size–size and size–mass show a higher slope for SMA and Nonthué, which underline allometric differences between these two populations and the Yuco's one. The lower population densities in both sites (SMA 33 ind./m2 and Nonthué 76 ind./m2) compare to Yuco (176 ind./m2) and the absence of individuals younger than 7 and 5 years old, respectively, in SMA and Nonthué could be related to the higher allochthonous OM content in the sediments and total suspended solids in water. Increased OM due to urban pollution in SMA bivalves leads to higher oxidative damage to lipids, which is not counterbalanced by the higher detoxification enzyme glutathione-S-transferase activity. Hence, we can conclude that pollution would explain the drastic reduction in population density, probably related to a high impair in the juvenile's survival/recruitment, the higher observed mortality and the lower population longevity. When increased OM is supply by the forest, like in Nonthué, this has less negative effect on population density and no effect on longevity at all. However, a negative effect of oxygen depletion due to increased OM (either anthropogenic or natural) on juvenile survival cannot be discarded, but further studies should be carried out to support this idea. |
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| Keywords: | Freshwater bivalves Growth rates Population parameters Allochthonous organic matter Anthropogenic impact Sewage pollution |
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