An Analysis of Mercurials in the Elephant Butte System

Analyses of samples for mercury from Elephant Butte Lake collections were made by a flameless atomic absorption procedure.

Mercury levels are expressed on a wet weight basis for animal tissues and on a dry weight basis for other materials. Analyses revealed mean ppb mercury concentrations of 0.027 in water, 57 in bottom sediments, 109 in phytoplankton, 277 in attached algae and bryophytes, 95 in plant debris, 69 in zooplankton, 90 in crayfish muscle, 26 in visceral mass of mussels, 97 in muscle of nonpredaceous fish, 125 in muscle of small predaceous fish, 253 in muscle of large predaceous fish, and 266 in muscle of two turtle species.

Walleye muscle displayed a mean level above 500 ppb, while other predaceous fish exhibited lower levels. Muscle values above 500 ppb were found in at least one specimen of flathead catfish and white bass. Significant direct relationships between mercury level in muscle and weight and length, or both, were shown by white bass and channel catfish, while general but not significant trends were indicated by other larger predators Smaller predators and nonpredaceous fish showed few relationships of this kind.

Mercury distribution patterns in fish and turtle species were similar to each other. Mean mercury levels in liver exceeded 500 ppb in flathead catfish, white bass, walleye, and two turtle species. Values above 1,000 ppb in liver were exhibited by at least one speciman of each of the two turtle species. Mean levels in kidney approached or exceeded those in muscle and liver for a few individual specimens of walleye, white bass, and flathead catfish. Flathead catfish, walleye, white bass, channel catfish, largemouth bass, longear sunfish, green sunfish, river carp- sucker and two turtle species displayed highest levels in liver. Black crappie displayed highest levels in kidney. Northern pike and warmouth bass displayed highest levels in muscle and buffalofish displayed highest levels in stomach. White crappie, bluegill, carp, and gizzard shad displayed highest levels in spleen.

Tissues grouped by relative levels for the sixteen fish species show consistently lower levels in bone, skin, gills, and eyes; intermediate levels in stomach, intestine, heart, and brain; and higher levels in spleen, muscle, kidney, and liver. General bioamplification at higher trophic levels appears to be diet related, but the relationship does not hold for lower trophic levels.

Mercury levels in the water indicate a decreasing gradient from inlet to dam while sediments display an increasing gradient from inlet to dam.Arguments are given which attempt to account for concentration in some higher trophic level species. There appears to be evidence which suggests that mercury levels are related to seasonal conditions A bioamplification scheme and concentration factors are presented which describe the status of mercury concentrations in existing trophic levels. Recommendations regarding the potential hazards of Elephant Butte fish to human health are discussed.

Project No. A-040-NMEX