Nelson J O’Driscoll

• PhD
• Head of Earth and Environmental Science Department; Full Professor at Acadia University

Mercury (Hg) is a global environmental concern due to its wide distribution and myriad of deleterious effects on biota. We studied hepatic Hg in a widespread, top predator in the terrestrial ecosystem of Nova Scotia, Canada, the eastern coyote (Canis latrans), to determine recent concentrations, identify drivers of variation in Hg levels, and asses...

Mercury (Hg) is a naturally-occurring, toxic contaminant that accumulates in ecosystems, potentially having deleterious effects on the health of wildlife and habitat quality. Significant advances have been made in understanding Hg cycling in freshwater and marine ecosystems, but the processes controlling Hg accumulation in bogs and the confounding...

Fifty years after Big Meadow Bog was ditched for agriculture, conservation concern about the possible extirpation from Canada of the Endangered Eastern Mountain Avens initiated and galvanized a restoration program. There were many elements considered in addressing the benchmark research needed prior to on the ground restoration; these are summarize...

An understanding of the geological history and ecosystems evolution of Big Meadow Bog peatland at Brier Island, Nova Scotia is an important element of informing the conservation management of critical habitats for a complex of nationally listed, rare, disjunct wetland species. The ecology of the peatland is influenced by both chemistry and morpholo...

Big Meadow Bog, in the center of Brier Island, Nova Scotia, has long been the nesting site for American herring gulls (Larus smithsoniansus Coues), with recent counts of approximately 3000 pairs of birds at the colony in the summer. Gulls move from the colony to fish-processing plants, mink farms, aquaculture sites, and marine coastlines to feed, a...

Considerable amounts of polyethylene terephthalate (PET) microplastic fibers are released into the environment by the laundering of polyester clothing. Microplastic fibers can be ingested by organisms in the environment. Therefore, it has been suggested that microplastic fibers act as vectors for adsorbed contaminants, which are subsequently desorb...

Water resource development can alter the movement and ecology of sturgeons. We studied total (THg) and methylmercury concentrations in whole blood sampled non-lethally from namew (Moose Cree L-dialect, lake sturgeon, Acipenser fulvescens), an endangered and culturally important subsistence fish. Namew were sampled from two tributaries within the Mo...

We investigated total mercury (THg) and methylmercury (MeHg) concentrations in coastal mussels (Mytilus spp.) sampled from the Minas Basin, Bay of Fundy and evaluated the relationship with condition index (CI). THg concentrations were low in sediment (mean THg = 5.15 ± 2.11 ng/g dw; n = 6) and soft tissues (mean THg = 62.3 ± 13.7 ng/g; mean MeHg =...

A controlled chamber method using continuous gold trap atomic fluorescence spectroscopy (AFS) (Tekran 2537X) for the analysis of Hg(0) emissions from moderate mass rock samples was developed and tested. A series of black shale and other bedrock samples from Nova Scotia, Canada, were used to test the method and its reproducibility. Hg(0) emissions a...

Seabird feces as indicators of the exposure to environmental contaminants have been studied worldwide. Penguins are indicator species for marine pollution, but their role as biovectors of rare earth elements (REEs) to ecosystems have been little studied. The present study quantified the concentration of REEs and trace elements (TEs) in feces of gen...

Seabirds are globally recognized vectors of marine-derived materials, which get deposited on land at their breeding colonies, potentially altering local soil chemistry. We studied mercury (Hg) in soil cores on two islands in west Iceland that host thousands of nesting seabirds, predicting that Hg subsidies from nesting birds would result in elevate...

Hydropower development can alter the movement, diet, and contaminant exposure of riverine fish, including Lake Sturgeon, a species of special concern and an culturally important subsistence fish for Indigenous Communities. We studied mercury (Hg) concentrations in sturgeon whole blood, muscle, and liver from two tributaries of the Moose River in th...

Studies on mercury bioaccumulation and biomagnification in coastal invertebrates in eastern Canada are limited, but these data are necessary to determine risk of mercury exposure effects in upper trophic level organisms. We quantified methylmercury (MeHg), total mercury (THg), and stable isotopes of δ13C and δ15N in 14 species of invertebrates in t...

Penguins are sentinel species for marine pollution, but their role as potential biovectors of REEs or TEs to ecosystems has been poorly studied. The present study analyzed (ICP-MS) feathers of young and adult Gentoo penguins from Fildes Bay, for 63 elements (including 15 REEs). Most of the REEs were present at very low levels, ranging from 0.002 (L...

Due to their natural geochemistry, intertidal estuarine ecosystems are vulnerable to bioaccumulation of methylmercury (MeHg), a neurotoxin that readily bioaccumulates in organisms. Determining MeHg concentrations in intertidal invertebrates at the base of the food web is crucial in determining MeHg exposure in higher trophic level organisms like fi...

Net photoreduction of divalent mercury (Hg(II)) and volatilization of photoreduction products (i.e., elemental mercury (Hg (0))/dissolved gaseous mercury (DGM)) is a mechanism by which mercury burdens in ecosystems are lessened. The effects of salinity on mercury photoreactions were investigated while controlling the concentration of DOM (>1 kDa) u...

Pinnipeds are sentinel species for marine pollution, but their role as vectors of trace elements (TEs) or rare earth elements (REEs) to ecosystems has been poorly studied. The present study tested pinniped feces for 61 elements, including REEs. Feces of adult seals (Mirounga leonina, Hydrurga leptonyx) from Fildes Bay, King George Island, Antarctic...

The biomagnification of toxic methylmercury (MeHg) and selenium (Se) through aquatic food webs using nitrogen stable isotopes (δ¹⁵N) varies among ecosystems but underlying mechanisms are yet unexplained. Given the strong links between MeHg and thiol-containing amino acids and proteins containing selenocysteine, our hypothesis was that cysteine cont...

The Minamata Convention recognized mercury (Hg) as a chemical of global concern. Research in the Tagus Estuary started in the late 70’s; however, knowledge on Hg contamination in this system has greatly improved in the last decade. Results showed two highly contaminated zones, whereas, in areas far from the sources, Hg and monomethylmercury (MMHg)...

Seabirds are important biovectors of contaminants, like mercury, moving them from marine to terrestrial environments around breeding colonies. This transfer of materials can have marked impacts on receiving environments and biota. Less is known about biotransport of contaminants by generalist seabirds that exploit anthropogenic wastes compared to o...

Total photoreducible mercury [Hg(II)RED] and photoreduction rates in the surface waters of four lakes in Kejimkujik National Park, Nova Scotia were measured monthly over a summer. The percent of THg that was photoreducible [%Hg(II)RED] decreased significantly in two of the four lakes from early to late summer: North Cranberry (maximum 42% to minimu...

Forest harvesting affects dissolved organic matter (DOM) and aqueous mercury inputs as well as the food web structure in small headwater streams, but how these upstream changes manifest downstream is unclear. To address this uncertainty, we examined DOM quality, autochthony in the caddisfly Hydropsychidae (using δ2H), and methylmercury (MeHg) conce...

Delays in forest recovery from terrestrial acidification combined with climate change are leading Acadian Forest ecosystems into new territory. The Kejimkujik Calibrated Catchments (KCC) Study Program was established in and adjacent to Kejimkujik National Park and Historic Site (KNP) in Southwest Nova Scotia (SWNS), Canada, in the late 1970s to stu...

Avian biovector transport is an important mechanism for the movement of contaminants and nutrients to remote locations, usually bird colonies, through excretion, molting and decomposition of carcasses. Methylmercury (MeHg) is a bioaccumulative neurotoxin and endocrine disruptor which is present in many remote ecosystems. We collected guano samples...

Methylmercury (MeHg) is a toxic and bioaccumulative organo-metallic compound that is naturally produced in many ecosystems. Organisms that occupy the lower trophic positions in food webs may be key factors in the assessment of MeHg biomagnification between ecosystems. Here we present a review of the peer-reviewed literature examining MeHg bioac-cum...

Quantifying methylmercury (MeHg) concentrations and uptake at the base of the food web is useful for assessing mercury exposure risk to higher trophic level organisms. Higher MeHg concentrations near the base of the food web may result in more MeHg exposure and accumulation in higher trophic organisms. Here, we analyze MeHg in caddisflies, mayflies...

In situ air concentrations of gaseous elemental mercury (Hg(0)) and vegetation–atmosphere fluxes were quantified in both high (Cala Norte, CN) and low-to-moderate (Alcochete, ALC) Hg-contaminated saltmarsh areas of the Tagus estuary colonized by plant species Halimione portulacoides (Hp) and Sarcocornia fruticosa (Sf). Atmospheric Hg(0) ranged betw...

The Leach's storm-petrel (Hydrobates leucorhous) is one of the most abundant and widely distributed marine birds in the North Atlantic but is under global population decline, possibly linked to marine pollution. We determined levels of ingested plastic and hepatic total mercury (THg) in recently fledged juveniles that stranded in Newfoundland and L...

Methylmercury (MeHg) is a global environmental contaminant that poses significant risks to the health of humans, wildlife, and ecosystems. Assessing MeHg exposure in biota across the landscape and over time is vital for monitoring MeHg pollution and gauging the effectiveness of regulations intended to reduce new mercury (Hg) releases. We used MeHg...

Sympatric communities of organisms may exploit different ecological niches to avoid intra- and interspecific competition. We examined the isotopic niches of American black ducks (Anas rubripes) and mallards (A. platyrhynchos) wintering in coastal and urban areas of Atlantic Canada and compared isotopic niche with digestive tract morphologies and bl...

The use of naturally occurring epiphytic lichens can be an effective tool for regional monitoring of mercury (Hg) and other potentially toxic elements (PTEs). Nova Scotia, Canada is a hotspot for mercury and other trace metal accumulation in ecosystems; partially attributed to long-range transport of air pollution. The relative contribution of loca...

The bioaccumulation of Potentially Toxic Elements (PTEs) by benthic invertebrates in estuarine sediments is poorly understood. We sampled and analysed PTEs in sediments and benthic invertebrates from five sites in the Skeena Estuary (British Columbia, Canada), including sites adjacent to an abandoned cannery and a decommissioned papermill. Our aim...

Dissolved gaseous mercury (DGM) production was examined in relation to ultraviolet radiation within a marine aquaculture site in the contaminated Marano and Grado Lagoon (Italy). The measured rates of DGM production relative to time elapsed (17.06 and 20.68 pg h⁻¹, respectively) were substantially (6–20 times) higher than what has been observed in...

Aquatic invertebrates vary in methylmercury (MeHg) levels among systems which has been attributed, in part, to environmental conditions, but may also be linked to differences in their biochemical composition. As MeHg is known to bind to thiol-containing amino acids such as cysteine in proteins of fish, our objective was to determine if these amino...

Relationships between concentrations of Potentially Toxic Elements (PTEs) in estuarine sediments and their impact benthic invertebrate communities are poorly understood. We sampled and analysed PTEs in sediments and benthic invertebrates from five sites surrounding the Skeena Estuary, including sites adjacent to an abandoned cannery and a decommiss...

Methylmercury (MeHg) biomagnifies through aquatic food webs resulting in elevated concentrations in fish globally. Stable carbon and nitrogen isotopes are frequently used to determine dietary sources of MeHg and to model its biomagnification. However, given the strong links between MeHg and sulfur cycling, we investigated whether sulfur isotopes (δ...

Mercury (Hg) is a toxic element which has increased in marine environments for more than a century, due largely to anthropogenic activities, and biomagnifies in food chains to harmful levels in some top predators like waterfowl and seabirds. We analysed total mercury (THg) concentrations in blood, brain and muscle tissue from healthy specimens of 1...

Methylmercury (MeHg) is a neurotoxin and endocrine disruptor that bioaccumulates and biomagnifies through trophic levels, resulting in potentially hazardous concentrations. Although wetlands are known hotspots for mercury (Hg) methylation, the effects of avian biovectors on these processes are poorly understood.We examined Hg speciation and distrib...

Although estuaries are critical habitats for many aquatic species, the spatial trends of toxic methylmercury (MeHg) in biota from fresh to marine waters are poorly understood. Our objective was to determine if MeHg concentrations in biota changed along a salinity gradient in an estuary. Fourspine Stickleback (Apeltes quadracus), invertebrates (snai...

Methylmercury (MeHg) bioaccumulation is a growing concern in ecosystems worldwide. The absorption of solar radiation by dissolved organic matter (DOM) and other photoreactive ligands can convert MeHg into less toxic forms of mercury through photodemethylation. In this study, spectral changes and photoreactivity of DOM were measured to assess the po...

Mercury (Hg) in the Arctic is a significant concern due to its bioaccumulative and neurotoxic properties, and the sensitivity of Arctic environments. Previous research has found high levels of Hg in snowpacks with high chloride (Cl⁻) concentrations. We hypothesised that Cl⁻ would increase Hg retention by decreasing Hg photoreduction to Hg(0) in mel...

Mercury contamination is a growing concern for freshwater food webs in ecosystems without point sources of mercury. Methylmercury (MeHg) is of particular concern, as this is the form of mercury that crosses the blood–brain barrier and is neurotoxic to organisms. Wetlands and benthic sediments have high organic content and low oxygen availability. A...

Mercury is a globally distributed, environmental contaminant. Quantifying the retention and loss of mercury is integral for predicting mercury-sensitive ecosystems. There is little information on how dissolved organic carbon (DOC) concentrations and particulates affect mercury photoreaction kinetics in freshwater lakes. To address this knowledge ga...

Environmental contamination by mercury is a concern in marine food webs, and especially for large fish. We examined methylmercury (MeHg) levels in blood, muscle and liver of 35 individual Atlantic sturgeon (Acipenser oxyrhynchus), a commercially harvested, anadromous fish eastern Canada. Females had higher blood and liver MeHg levels than males, an...

Photodemethylation can be one of the primary processes for loss of neurotoxic methylmercury (MeHg) in freshwater lakes. Few studies have quantified seasonal variations in photodemethylation rate constants as a function of dissolved organic matter (DOM). We conducted 1-week irradiation experiments in two seasons to test for spatial and temporal diff...

Mercury (Hg) dynamics was evaluated in contaminated sediments and overlying waters from Tagus estuary, in two sites with different Hg anthropogenic sources: Cala Norte (CNOR) and Barreiro (BRR). Environmental factors affecting methylmercury (MMHg) production and Hg and MMHg fluxes across sediment/water interface were reported. [THg] and [MMHg] in s...

Intertidal sediments of Tagus estuary regularly experiences complex redistribution due to tidal forcing, which affects the cycling of mercury (Hg) between sediments and the water column. This study quantifies total mercury (Hg) and methylmercury (MMHg) concentrations and fluxes in a flooded mudflat as well as the effects on water-level fluctuations...

This study examines, for the first time, the neurotoxicity of Hg(II) and MeHg in fish (Diplodus sargus) in a time-course comparative perspective and considering realistic exposure levels and routes. Both forms followed an identical time-variation pattern of accumulation in the brain, but dietary MeHg was more efficiently transported to the brain. M...

We used a paleolimnological approach at Long Lake, Nova Scotia, to construct a 10 500-year record of metal deposition in lakebed sediments and elucidate the influence of both natural and anthropogenic environmental changes. Aquatic sediment concentrations of mercury (Hg), arsenic (As), and chromium (Cr) in Long Lake fluctuated substantially and, du...

Salt marshes are ecologically sensitive ecosystems where mercury (Hg) methylation and biomagnification can occur. Understanding the mechanisms controlling gaseous Hg flux from salt marshes is important to predict the retention of Hg in coastal wetlands and project the impact of environmental change on the global Hg cycle. We monitored Hg flux from...

Mercury (Hg) is a ubiquitous heavy metal that occurs naturally in the environment, but its levels have been supplemented for decades by a variety of human activities. Mercury can have serious deleterious effects on a variety of organisms, with top predators being particularly susceptible because methylmercury bioaccumulates and biomagnifies in food...

Methylmercury (MeHg) exposure and adverse health effects in fishes have been documented, but the molecular mechanisms involved in toxicity have not been fully characterized. The objectives of the current study were to (1) determine whether total Hg (THg) in the muscle was predictive of MeHg concentrations in the brain of wild female yellow perch (P...

The Tagus Estuary is one of the most Hg-contaminated estuaries in SW Europe. Sediment cores were sampled at two low Hg-contaminated sites inside the natural park, Alcochete (ALC) and Vale Frades (VF), and analyzed for mercury and methylmercury. Concentrations of Hg and MeHg in sediments were below 1 μg g⁻¹ and 4.4 ng g⁻¹, respectively. While in sum...

The present study examined potential effects of seasonal variations in photoreactive dissolved organic matter (DOM) on methylmercury (MeHg) photodemethylation rates in freshwaters. A series of controlled experiments were carried out using natural and photochemically preconditioned DOM in water collected from one lake in June, August, and October. N...

Currently the spatial patterns of airbourne mercury associated with Nova Scotia lichens are largely unknown. Nova Scotia lichens are poorly represented in the online GenBank sequence database. We collected portions of a range of lichen species, with GPS coordinates and habitat data from opportunistically-selected locations throughout the province....

The current study aims to shed light on the neurotoxicity of MeHg in fish (white seabream − Diplodus sargus) by the combined assessment of: (i) MeHg toxicokinetics in the brain, (ii) brain morphometry (volume and number of neurons plus glial cells in specific brain regions) and (iii) fish swimming behavior (endpoints associated with the motor perfo...

Nitrogen and carbon stable isotopes (?(15) N, ? (13) C) are commonly used to understand mercury (Hg) bioaccumulation and biomagnification in freshwater food webs. Though sulfur isotopes (? (34) S) can distinguish between energy sources from the water column (aqueous sulfate) versus sediments to freshwater organisms, little is known about whether ?...

Methylmercury (MeHg) bioaccumulation in lower-trophic-level organisms and its subsequent biomagnification through food webs differs in magnitude among lakes and results in intraspecific variability of MeHg in top predator fishes. Understanding these differences is critical given the reproductive and neurotoxic effects of MeHg on fishes and their pr...

We investigated the impact of managed retreat on mercury (Hg) biogeochemistry at a site subject to diffuse contamination with Hg. We collected sediment cores from an area of land behind a dyke one year before and one year after it was intentionally breached. These sediments were compared to those of an adjacent mudflat and a salt marsh. The concent...

Beavers (Castor spp.) are ecosystem engineers and important modifiers of freshwater ecosystems. They create impoundments that flood the surrounding landscape and modify the flow of materials through streams, thus potentially increasing nutrients, productivity and the availability of toxic methyl mercury (MeHg) to downstream food webs. Here we quant...

Mercury (Hg) is an important environmental contaminant, due to its neurotoxicity and ability to bioaccumulate. The Arctic is a mercury-sensitive region, where organisms can accumulate high Hg concentrations. Snowpack mercury photo-redox reactions may control how much Hg is transported with melting Arctic snow. This work aimed to: 1) determine the s...

Dragonflies (Odonata: Anisoptera) are an important component of both aquatic and terrestrial food webs and are vectors for methylmercury (MeHg) biomagnification. Variations in mercury content with life stage and body regions may affect the relative transfer of mercury to aquatic or terrestrial food webs; however, there has been little research on t...

Recurring polynyas are important areas of biological productivity and feeding grounds for seabirds and mammals in the Arctic marine environment. In this study, we examined food web structure (using carbon and nitrogen isotopes, δ(13)C and δ(15)N) and mercury (Hg) bioaccumulation and biomagnification in a small recurring polynya ecosystem near Nasar...

Controlled experiments were performed with frozen and melted Arctic snow to quantify relationships between mercury photoreaction kinetics, ultra violet (UV) radiation intensity, and snow ion concentrations. Frozen (-10°C) and melted (4°C) snow samples from three Arctic sites were exposed to UV (280-400nm) radiation (1.26-5.78W·m(-2)), and a parabol...

This review summarizes data and information which have been generated on mercury (Hg) in the marine environment of the Canadian Arctic since the previous Canadian Arctic Contaminants Assessment Report (CACAR) was released in 2003. Much new information has been collected on Hg concentrations in marine water, snow and ice in the Canadian Arctic. The...

Biogeochemistry of methylmercury (MeHg) in sediments is not completely understood, regarding seasonal and spatial variations within estuaries. Historical mercury (Hg) contamination in Tagus estuary is known but MeHg variability is poorly documented. Here, seasonality of MeHg is assessed in pore waters for the first time and in solid sediments from...

Mercury is a toxic and bioaccumulative environmental contaminant, which may be transported to remote regions around the world, such as the Arctic. Snowmelt is a major source of mercury to many surface water environments, but the amount of mercury in snow varies considerably. This variation is due to the balance of mercury retention and losses from...

This study examines mercury exposure in bats across the northeast U.S. from 2005 to 2009. We collected 1,481 fur and 681 blood samples from 8 states and analyzed them for total Hg. A subset (n = 20) are also analyzed for methylmercury (MeHg). Ten species of bats from the northeast U.S. are represented in this study of which two are protected by the...

Mercury (Hg) contamination in aquatic systems remains a global concern because the organic form, methyl Hg (MeHg), can biomagnify to harmful concentrations in fish, fish-eating wildlife, and humans. Food web transfer of MeHg has been explored using models of log MeHg versus relative trophic position (nitrogen isotopes, δ(15)N), but regression slope...

The polychaete worm Nereis diversicolor engineers its environment by creating oxygenated burrows in anoxic intertidal sediments. We carried out a laboratory microcosm experiment to test the impact of polychaete burrowing and feeding activity on the lability and methylation of mercury in sediments from the Bay of Fundy, Canada. The concentration of...

Biomagnification processes and the factors that govern them, including those for mercury (Hg), are poorly understood in streams. Total and methyl Hg concentrations and relative trophic position (using δ15N) were analyzed in biofilm and invertebrates from 21 streams in New Brunswick, Canada to assess food web biomagnification leading to the common m...

Polychaete worms are abundant in many mudflats but their importance to coastal food web Hg biomagnification is not known. We sampled sediments and polychaete worms from mudflats in the Bay of Fundy to investigate the bioaccumulation of mercury (Hg) and methylmercury (MeHg) in the coastal invertebrate food web. Hg concentrations in the sediments wer...

Analysis of dissolved organic matter (DOM) concentration and composition is essential to quantifying biological and chemical oxygen demand and atmosphere–ocean heat flux exchange in natural waters. However, manual water sampling is costly and time consuming over large areas. The purpose of this research was to analyze the applicability of airborne...