Testing coastal Lichen and Moss species as a bioindicator of atmospheric Total Mercury and Monomethylmercury in Santa Cruz County, CA

Belle Zheng1, Wendy Lin2, Peter Weiss-Penzias3, Ken Kellman4, Alfred Freeberg5 and Brian Young6

Lichen are unique terrestrial organisms that form stable mutualistic associations between fungi, algae and cyanobacteria.. They have also been used as indicators of healthy air as they are able to accumulate airborne pollutants such as heavy metals like mercury in their thalli (vegetative tissue). A previous study done in the Canadian High Arctic found that lichen had median monomethylmercury (MMHg) and median total mercury (THg) concentrations that were two orders higher of magnitude than the soils underlying them. Intrigued by these data, we decided to test the concentrations of MMHg and THg in lichen and moss in Santa Cruz, CA. The main purpose of the study is to find out whether lichens and mosses can be used as bioindicators of environmental mercury, especially the effects of coastal fog. Various lichen and moss species were collected in Santa Cruz County, then freeze-dried and homogenized, and then analyzed for MMHg and THg concentrations. Lichen and moss THg concentrations ranged from 31.9 to 400.4 ng g-1, with an average of 178.9±111 ng g-1. Lichen and moss MMHg concentrations ranged from 3.86 ng g-1 to 73.3 ng g-1, with an average of 30.3±37.8 ng g-1. In a similar study the median THg and median MMHg were found at 66.8 ng g-1 and 4.27 ng g-1 respectively. From our preliminary data, we are optimistic that lichen and moss are good indicators of airborne mercury concentrations. We will continue this idea by sampling along a coastal-inland transect (fog frequency gradient) at the end of the fog season. Our study may be able to provide insight on how MMHg and THg enter the coastal food chain through fog water deposition.


1University of California, Santa Cruz, pweiss@ucsc.edu
2University of California, Santa Cruz, wlin24@ucsc.edu
3University of California, Santa Cruz, pweiss@ucsc.edu
4University of California, Santa Cruz, kkellman@ucsc.edu
5University of California, Santa Cruz, afreeber@ucsc.edu
6University of California, Santa Cruz, brpayoun@ucsc.edu