Geology topics

Matthew M. Chumchal

Publications and source records attributed to Matthew M. Chumchal.

4 recordsLinked to original sources

USGS2025

Predictors of mercury and pesticide fluxes by emerging adult aquatic insects from prairie pothole wetlands

Aquatic and terrestrial food webs are linked by movements of aquatic insects during their development from larvae to adults. Contaminants can affect these linkages by reducing insect survival and increasing tissue contaminant concentrations through adult metamorphosis, thus changing contaminant flux from water to land. Most anthropogenically influenced freshwater ecosystems are exposed to multiple contaminants. To better understand the combined effects of contaminants on aquatic–terrestrial linkages, we investigated how adult aquatic insect emergence and tissue contaminant concentrations affect insect-mediated contaminant flux of mercury and pesticides from wetlands. In a field survey of 15 wetlands in the Prairie Pothole Region, an important agricultural region of North America, we found that insect-mediated mercury flux was 3.5 times more strongly predicted by emergence biomass than tissue mercury concentration. Thus, factors that were previously found to influence aquatic insect emergence biomass in this system—including insecticide tissue concentrations in adult insects, open water surface area, and agricultural land use—were the most likely to drive insect-mediated mercury flux. Pesticide flux, however, was 3.3 times more strongly predicted by the tissue pesticide concentration than by emergence. Thus, factors that influence pesticide exposure and, to a smaller extent, emergence biomass were the most likely to drive pesticide flux. Our results show how factors driving contaminant fluxes by adult aquatic insects differ by contaminant class, and they suggest one mechanism by which toxic effects of one contaminant (pesticides) could influence the flux of another (mercury). Predicting contaminant fluxes in areas where different mixtures of contaminants are present can aid in identifying risk to insectivores.

Prairie Pothole Region↗

USGS2022

Use of riparian spiders as sentinels of persistent and bioavailable chemical contaminants in aquatic ecosystems: A review

Aquatic ecosystems around the world are contaminated with a wide range of anthropogenic chemicals, including metals and organic pollutants, that originate from point and nonpoint sources. Many of these chemical contaminants have complex environmental cycles, are persistent and bioavailable, can be incorporated into aquatic food webs, and pose a threat to the health of wildlife and humans. Identifying appropriate sentinels that reflect bioavailability is critical to assessing and managing aquatic ecosystems impacted by contaminants. The objective of the present study is to review research on riparian spiders as sentinels of persistent and bioavailable chemical contaminants in aquatic ecosystems. Our review of the literature on riparian spiders as sentinels suggests that significant progress has been made during the last two decades of research. We identified 55 published studies conducted around the world in which riparian spiders (primarily of the families Tetragnathidae, Araneidae, Lycosidae, and Pisauridae) were used as sentinels of chemical contamination of lotic, lentic, and estuarine systems. For several contaminants, such as polychlorinated biphenyls (PCBs), Hg, and Se, it is now clear that riparian spiders are appropriate sentinels. However, many contaminants and factors that could impact chemical concentrations in riparian spiders have not been well characterized. Further study of riparian spiders and their potential role as sentinels is critical because it would allow for development of national-scale programs that utilize riparian spiders as sentinels to monitor chemical contaminants in aquatic ecosystems. A riparian spider sentinel program in the United States would be complementary to existing national sentinel programs, including those for fish and immature dragonflies.

Environmental Toxicology and Chemistry↗

USGS2016

Disparity between state fish consumption advisory systems for methylmercury and US Environmental Protection Agency recommendations: A case study of the South Central United States

Fish consumption advisories are used to inform citizens in the United States about noncommercial game fish with hazardous levels of methylmercury (MeHg). The US Environmental Protection Agency (USEPA) suggests issuing a fish consumption advisory when concentrations of MeHg in fish exceed a human health screening value of 300 ng/g. However, states have authority to develop their own systems for issuing fish consumption advisories for MeHg. Five states in the south central United States (Arkansas, Louisiana, Mississippi, Oklahoma, and Texas) issue advisories for the general human population when concentrations of MeHg exceed 700 ng/g to 1000 ng/g. The objective of the present study was to estimate the increase in fish consumption advisories that would occur if these states followed USEPA recommendations. The authors used the National Descriptive Model of Mercury in Fish to estimate the mercury concentrations in 5 size categories of largemouth bass–equivalent fish at 766 lentic and lotic sites within the 5 states. The authors found that states in this region have not issued site‐specific fish consumption advisories for most of the water bodies that would have such advisories if USEPA recommendations were followed. One outcome of the present study may be to stimulate discussion between scientists and policy makers at the federal and state levels about appropriate screening values to protect the public from the health hazards of consuming MeHg‐contaminated game fish.

Arkansas, Louisiana, Mississippi, Oklahoma, Texas↗

USGS2013

Effects of mercury deposition and coniferous forests on the mercury contamination of fish in the south central United States

Mercury (Hg) is a toxic metal that is found in aquatic food webs and is hazardous to human and wildlife health. We examined the relationship between Hg deposition, land coverage by coniferous and deciduous forests, and average Hg concentrations in largemouth bass (Micropterus salmoides)-equivalent fish (LMBE) in 14 ecoregions located within all or part of six states in the South Central U.S. In 11 ecoregions, the average Hg concentrations in 35.6-cm total length LMBE were above 300 ng/g, the threshold concentration of Hg recommended by the U.S. Environmental Protection Agency for the issuance of fish consumption advisories. Percent land coverage by coniferous forests within ecoregions had a significant linear relationship with average Hg concentrations in LMBE while percent land coverage by deciduous forests did not. Eighty percent of the variance in average Hg concentrations in LMBE between ecoregions could be accounted for by estimated Hg deposition after adjusting for the effects of coniferous forests. Here we show for the first time that fish from ecoregions with high atmospheric Hg pollution and coniferous forest coverage pose a significant hazard to human health. Our study suggests that models that use Hg deposition to predict Hg concentrations in fish could be improved by including the effects of coniferous forests on Hg deposition.

Arkansas;Louisiana;Mississippi;Oklahoma;Tennessee;↗