Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Sites sampled in 2010 (n = 7) are denoted by a circle, while sites sampled in 2010 and 2011 (n = 4) are denoted by a star. Sites with baseline data from 1990–1992 (Galveston, Dauphin) are marked with a purple circle.
