RMP News Volume 3, Issue 1

Regional Monitoring News

Volume 3, Issue 1 Spring 1997

Contents

Mercury in the Estuary
In Brief: 1995 RMP Results
1997 Cruise Schedule
Five-Year Review
Annual Meeting Summary
Trends in Aquatic Toxicity
RMP Data on the Web
Data Usage and Publication Policy
Newsletter Survey
Calendar
Announcements

Mercury In the Estuary

by Rainer Hoenicke, Jay Davis, and Adrienne Yang

Mercury (or quicksilver) is a naturally occurring metal which has several
forms. It is also one of the most toxic substances, especially when combined
with other elements to produce organic mercury compounds like methylmercury.
Mercury has been found throughout the San Francisco Estuary at elevated
concentrations in water, sediment, and organisms. It is of particular
concern as a human health issue, as it accumulates in tissues and its
levels increase up the food web. For example, fish bioaccumulate mercury
of the most toxic form--monomethylmercury--and fish at the top of the
food web can harbor mercury concentrations over one million times the
mercury concentration in the water in which they swim. 

As a result of the tremendous increase in mercury production and use
in this century, as well as the ease with which many forms of mercury
dissolve in water, contamination of this metal is virtually world-wide.
It travels easily through different environmental media including the
atmosphere, in a variety of chemical forms, and is toxic to humans and
other organisms in very low concentrations. California is unique in
mercury contamination because in addition to the general, industrially
related global increases, it also contains specific contamination sites.
The California Coast Range contains one of the world's great geologic
deposits of mercury. This mercury was mined intensively during the late
1800s and early 1900s primarily in support of gold mining in the Sierra
Nevada where the mercury was used in the gold extraction process. A
legacy of leaking Coast Range mercury mines and lost Sierra Nevada quicksilver
is providing a significant, ongoing burden of mercury to the Estuary
from both sides of the State (see also Estuary, Vol. 5, No. 5,
October 1996, available from the San Francisco Estuary Project (510)
286-4392). 

Toxicity and Health Concerns

As mercury cycles through various forms and media, its bioavailability
(ability to contaminate organisms) and...