**National Irrigation Water Quality Program**\
U.S. Department of the Interior

**Biological Effects of Selenium and other Contaminants associated with
Irrigation Drainage in the Salton Sea Area, California 1992-1994**

Jewel Bennett\
U.S. Fish and Wildlife Service

ABSTRACT

The National Irrigation Water Quality Program (NIWQP) investigated
contaminants associated with drainwater in the Salton Sea area from
1986-1990 and concluded that Department of the Interior (DOI) trust
resources were adversely at risk to contaminants, especially reduced
reproductive capacity due to elevated levels of selenium, organochlorine
pesticides and possibly boron in the Salton Sea environment. The Salton
Sea project advanced to Phase IV, remediation planning, in the NIWQP.
Typically, in that phase of work, remediation projects are planned,
and/or additional data collection is conducted if needed. In the case of
the Salton Sea project, fairly extensive additional data collection was
conducted during 1992-1994 to clarify the biological effects of the
environmental contaminates documented to occur in the previous
investigations.

This report describes the biological effects of environmental
contaminants on several important fish and wildlife species in the
Salton Sea area that were investigated in 1992-94. Three studies were
conducted to obtain information about species either thought to be at
particular risk, or those for whom the effects of selenium and DDE (a
DDT-metabolite) are fairly well understood. The studies: 1) determined
embryotoxicity of colonial waterbirds (fish-eaters); 2) determined the
embryotoxicity and nesting proficiency of black-necked stilts (shoreline
aquatic invertebrate feeders); and 3) determined contaminant body
burdens of sailfin mollies, a surrogate species for the endangered
desert pupfish that inhabits agricultural drains. The recent bird
die-offs which have occurred at the Salton Sea are being investigated
separately because of the need to incorporate disease and biotoxicity
studies in addition to contaminants data.

The finding indicated: 1) colonial nesting water birds (great egrets,
snowy egrets, and black-crowned night herons) are at risk of reduced
reproduction from DDE-induced eggshell thinning and, to a lesser extent,
selenium-induced embryo mortality; in addition, egret embryos displayed
a high incidence of abnormalities (possibly over 100 times normal) of
unknown causes; 2) 95% of black-necked stilt eggs sampled indicated they
came from nests with a four-fold increased risk of nest failure due to
selenium-induced embryo mortality, and that stilts are experiencing a
4.5% reduction in nesting proficiency due to selenium exposure in the
Salton Sea area; and 3) the federal and state endangered desert pupfish
inhabiting agricultural drains are at risk of reproductive failure due
to selenium concentration in the adult fishes sampled.

Management implications are that the biological effects of selenium in
the Salton Sea area are more clearly understood. These effects include
reproductive depression in black-necked stilts, hazard to reproduction
of the desert pupfish, and selenium levels in fish which make them
hazardous food items for fish-eating birds. The apparent high incidence
of egret embryo abnormalities would require additional verification to
identify management options.