MP4 Metals in the Environment: Aquatic Biological Perspectives
Room 16A/B, Level 4
2:10 PM - 5:30 PM, Monday, 10 November 2003
Chair: Green, Andrew ,
Co-chair: Bielmyer, Gretchen ,
(119) Relationship between boron concentrations and rainbow trout in the Rio de los Patos, Argentina.
Meyer, J.1, Schlekat, C.2, 1 University of Wyoming, Laramie, WY, USA2 U.S. Borax, Inc., Valencia, CA, USA
ABSTRACT- Since they were stocked in 1973, a self-sustaining population of rainbow trout (RBT; Oncorhynchus mykiss) has inhabited the Rio de los Patos (RDLP) in the altiplano of northwest Argentina. This scenic river flows approximately 100 km before it disappears into the Salar del Hombre Muerto at an elevation of 4,000 m. Because (1) laboratory studies have reported teratogenic effects to RBT at concentrations as low as 0.1 mg B/L, making RBT a species of regulatory concern for boron in Europe, and (2) the RDLP contains elevated concentrations of boron and has no low-boron tributaries, this relatively undisturbed river system has important implications for establishing discharge limits for boron. In December 2002, we investigated the feasibility of trout reproduction studies in this remote and challenging environment. In the upper and middle reaches of the river, we found abundant trout and rooted aquatic macrophytes that were inhabited by amphipods (the dominant macroinvertebrate in the RDLP and in the RBT stomachs we examined). The local game warden described two major RBT spawning sites in the upstream and middle reaches, where we found boron concentrations of 3 and 12 mg B/L, respectively. Although we visited the RDLP one month after the spring (November) spawning period, we found remnant spawning redds at these and other sites. Our limited survey of the lowest reach of the RDLP revealed no fish, fewer rooted macrophytes, and higher concentrations of boron and two of the dominant inorganic ions (Na+ and Cl-). Future studies will examine the relationship between boron concentrations and in situ recruitment. For the enjoyment of the audience, we will show fewer graphs and more pictures than usual.
Key words: Argentina, Altiplano, Boron, Rainbow trout