Geology topics

Connor I. Olson

Publications and source records attributed to Connor I. Olson.

5 recordsLinked to original sources

USGS2025

Elevated mercury concentrations in riparian predators unaccounted for by trophic magnification

Riparian predators integrate both nutrients and contaminants from neighboring aquatic systems through their predation of emerging aquatic insects. The reliance of some riparian taxa on aquatic subsidies has led to them to being utilized as biosentinels of aquatic contamination, often justified through stable isotope studies (δ 13 C, δ 15 N) and trophic magnification models. However, evidence suggests that both isotopic signatures and contaminant burdens can be altered during insect metamorphosis, which could propagate to riparian predators. Here, we measured total mercury and δ 15 N in riparian and aquatic organisms in the headwater streams of southern Appalachia to compare biomagnification in both systems. We found that biomagnification rates were similar, but that mercury concentrations in riparian organism were approximately six times higher than neighboring aquatic organisms. We propose possible ecological mechanisms, occurring separately or simultaneously, that might explain these surprising observations: (1) metamorphosis bioamplifies mercury, (2) metamorphosis enriches δ 15 N values, and/or (3) the fractionation of δ 15 N that occurs during predation is less for the observed riparian predators than for the aquatic organisms. Further study is needed to elucidate the exact mechanism driving elevated mercury concentrations in riparian predators.

Environmental Science & Technology↗

USGS2025

Climate-driven deoxygenation of lakes alters the nutrient-toxin profile of a food fish

Climate change is rapidly altering fisheries supporting aquatic ecosystems. The implications for food security depend not only on harvest biomass but also concentrations of nutrients and toxins in fish. Using brook trout from Adirondack lakes (New York, USA), we tested whether ongoing lake deoxygenation trends will affect fish muscle omega-3 fatty acids, selenium, and mercury concentrations. Across space (16 lakes: 1 year) and time (6 years: 1 lake), anoxia decreased selenium and was associated with elevated fish mercury, with no effect on omega-3 content. Because selenium may mitigate some end points of mercury toxicity, highly variable Se:Hg molar ratios (0.70–35.79) in neighboring lakes may have health risk implications. For fish consumers, ongoing lake deoxygenation under climate change could potentially reduce selenium intake while enhancing mercury exposure. Simultaneous alteration of beneficial compounds and toxins by environmental change complicates the development of fish consumption advisories to safeguard public health in a warming world.

New York↗

USGS2022

Mercury in soils of the conterminous United States: Patterns and pools

Soils account for the largest global mercury reservoirs, but observations are sparse in many regions. The accumulation and turnover of mercury in soils determines whether they act as an atmospheric source or sink. Here, we present a spatial analysis of soil mercury from a large soil survey (three horizons, ∼4800 sites) across the conterminous United States conducted by the U.S. Geological Survey. Soil mercury pools were calculated for 11 layers, cumulatively representing the top 1 m of soil, and totaling 158 ± 2 Gg (±SD) of mercury (20.3 ± 0.2 mg m −2 ). Mercury areal density was greatest in mixed forest (27.3 ± 0.5 mg m −2 ), cropland (25.3 ± 0.3 mg m −2 ), and deciduous forest (25.6 ± 0.5 mg m −2 ) ecosystems and lowest in barren (13.5 ± 0.3 mg m −2 ) and shrubland (12.6 ± 0.2 mg m −2 ) ecosystems. Assessment of the provenance of soil mercury using bedrock titanium normalization suggests that 62%–95% of soil mercury is unexplained by parental sources.

conterminous United States↗

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↗

USGS2020

Practical considerations for the incorporation of insect-mediated contaminant flux into ecological risk assessments

Insect-mediated contaminant flux is truly an interdisciplinary concept that merges ideas from many technical areas of science (e.g., environmental chemistry, landscape ecology, and entomology). This chapter introduces risk assessors to this emerging and ecologically relevant concept by distilling the main mechanisms that drive insect-mediated contaminant flux and integrating them together so that more informed decisions can be made on whether the phenomenon presents a potential risk at a site.

Book chapter↗