Environmental stress on Corbicula fluminea (Bivalvia) in the Paran River delta (Argentina): complex pollution-related disruption of population structures

DEMETRIO BOLTOVSKOY, NANCY CORREA, DANIEL CATALDO, JORGE STRIPEIKIS AND MABEL TUDINO

ARCHIV FUR HYDROBIOLOGIE

Año: 1997 vol. 138 p. 483 - 507

0003-9136

Corbicula jZuminea was collected at monthly intervals in November 1991-June 1993, and in March, April 1995 at a site located in the vicinity of strong sources of industrial and sewage effluents (confluence of the Rivers San Antonio and Vinculacibn, SaV); and in November 1994 and March, April 1995 at a presumably less polluted one (Parana de las Palmas River, PP), in the lower delta of the Parana River (Argentina). Abundances at SaV ranged between 430 and 10,300 ind. me2, being noticeably higher than those at PP, as well as those at 19 stations between and around these two locales. Shell lengths at SaV were monotonous throughout the 19-months period, over 90 % of the clams varying between 16 and 22.5 mm in length; no discernible cohorts were recorded. At PP, on the other hand, juveniles below 5 mm were largely dominant, and shells above 25-30mm in length were very common. Larvae retrieved from the gills of gravid clams showed much greater mortality rates in waters from SaV (up to 75 % after 120 hr), than in those from PP and in the control (approximately 10 % after 192 hr). The first internal growth-related mark in clams from SaV was closer to the umbo (mean: 14.2mm), than that in clams from PP (mean: 24mm). It is concluded that inadequate water quality at SaV is responsible for 100 % mortalities of newborns, for dwarfed adult clams, and for the lack of discernible cohorts.was collected at monthly intervals in November 1991-June 1993, and in March, April 1995 at a site located in the vicinity of strong sources of industrial and sewage effluents (confluence of the Rivers San Antonio and Vinculacibn, SaV); and in November 1994 and March, April 1995 at a presumably less polluted one (Parana de las Palmas River, PP), in the lower delta of the Parana River (Argentina). Abundances at SaV ranged between 430 and 10,300 ind. me2, being noticeably higher than those at PP, as well as those at 19 stations between and around these two locales. Shell lengths at SaV were monotonous throughout the 19-months period, over 90 % of the clams varying between 16 and 22.5 mm in length; no discernible cohorts were recorded. At PP, on the other hand, juveniles below 5 mm were largely dominant, and shells above 25-30mm in length were very common. Larvae retrieved from the gills of gravid clams showed much greater mortality rates in waters from SaV (up to 75 % after 120 hr), than in those from PP and in the control (approximately 10 % after 192 hr). The first internal growth-related mark in clams from SaV was closer to the umbo (mean: 14.2mm), than that in clams from PP (mean: 24mm). It is concluded that inadequate water quality at SaV is responsible for 100 % mortalities of newborns, for dwarfed adult clams, and for the lack of discernible cohorts.mm in length; no discernible cohorts were recorded. At PP, on the other hand, juveniles below 5 mm were largely dominant, and shells above 25-30mm in length were very common. Larvae retrieved from the gills of gravid clams showed much greater mortality rates in waters from SaV (up to 75 % after 120 hr), than in those from PP and in the control (approximately 10 % after 192 hr). The first internal growth-related mark in clams from SaV was closer to the umbo (mean: 14.2mm), than that in clams from PP (mean: 24mm). It is concluded that inadequate water quality at SaV is responsible for 100 % mortalities of newborns, for dwarfed adult clams, and for the lack of discernible cohorts.