Bioaccumulation of mining derived metals in blood, liver, muscle and otoliths of two Arctic predatory fish species (Gadus ogac and Myoxocephalus scorpius).

Mining activities can cause adverse and long-lasting environmental impacts and detailed monitoring is therefore essential to assess the pollution status of mining impacted areas. Here we evaluated the efficacy of two predatory fish species (Gadus ogac i.e. Greenland cod and Myoxocephalus scorpius i.e. shorthorn sculpin) as biomonitors of mining derived metals (Pb, Zn, Cd and Hg) by measuring concentrations in blood, liver, muscle and otoliths along a distance gradient near the former Black Angel Pb-Zn mine (West Greenland). We detected metals in all tissues (except Cd and Hg in otoliths) and sculpin generally displayed higher concentrations than cod. For both species, concentrations were generally highest closest to the dominant pollution source(s) and gradually decreased away from the mine. The clearest gradient was observed for Pb in blood and liver (both species), and for Pb in otoliths (sculpin only). Similar to dissolved concentrations in seawater (but in contrast to bottom sediment), no significant decrease was found for Zn, Cd and Hg in any of the tissues. This demonstrates that by including tissues of blood (representing recent accumulation) and otolith (representing more long-term exposure signals) in the sampling collection, the temporal information on contaminant exposure and accumulation can be extended. We therefore conclude that both fish species are suitable as biomonitors near Arctic mine sites and, moreover, that blood and otoliths can serve as important supplementary monitoring tissues (in addition to liver and muscle traditionally sampled) as they provide extended temporal information on recent to long-term contaminant exposure.

Selenium and mercury in freshwater fish muscle tissue and otoliths: a comparative analysis.

Evaluating potential ecological and human health risks of exposure to bioaccumulative trace elements is typically implemented using analysis of tissue samples. Increasingly, the microchemistry of fish calcified structures is used to elucidate the lifetime exposure to trace elements. In the present study, we measured total mercury (THg), methylmercury (MeHg), and selenium (Se) in muscle tissue and otolith samples from 12 species of fish collected at reference sites and locations influenced by power plant wastewater. Muscle tissue concentrations of Se were sensitive to recent wastewater exposure magnitude, stream type, trophic level, and species (p < 0.001). For Hg, concentrations in muscle tissue and otoliths were affected only by trophic level and species. Levels of THg and Se in muscle tissue and otolith samples were positively correlated for those species with a robust sample size. Some individual fish from 3 species (channel catfish, hybrid striped bass, and freshwater drum) showed significantly increasing or decreasing lifetime concentrations of either THg or Se in otolith samples. Multiple regression analysis indicated that for bluegill muscle tissue Se concentrations could be best explained utilizing water concentrations of selenium, sulfate, and molybdenum (r2 = 0.87; p < 0.001). Because of the increased cost and specialized sample processing requirements of analyzing trace elements in otolith structures, it may be prudent to limit these analyses to those species where insights into temporal trends are sought or where evidence indicates that fish move into or out of contaminated water bodies. Environ Toxicol Chem 2019;38:1467-1475. © 2019 SETAC.

Migration tactics affect spawning frequency in an iteroparous salmonid (Salvelinus malma) from the Arctic.

Otolith strontium and multi-year mark-recapture information were used to characterize associations between migration patterns and spawning frequencies in an anadromous Dolly Varden (Salvelinus malma) population (Rat River, Northwest Territories, Canada) that undertakes a long migration between freshwater spawning/overwintering (Fish Creek; a tributary to Rat River) and marine feeding habitats (Beaufort Sea) (~800 km round trip). Reconstructions of lifetime annual migration histories among otolith annuli was matched to information on reproductive status (current-year 'spawner' or 'non-spawner') that was known in two different, sometimes successive, years for each fish. Two migratory life histories were observed: fish either migrated annually after smoltification or periodically skipped an annual ocean migration to remain in freshwater and spawn. Different spawning frequencies were detected where fish not migrating annually tended to spawn in alternate years (84.6%) more often than those migrating annually (50%). Additionally, annually migrating fish had lower longevity (≤9 years vs. ≤13 years). The evaluation of differences in spawning frequency between sexes, independent of migration tactic, revealed males (84.6%) skipped spawning more often than females (51.2%) suggesting fitness trade-offs between life histories differ between sexes. Further, some fish returned from the sea considerably earlier than the majority of other current-year migrants. Our findings demonstrate intrapopulation diversity in migration behaviour and reproductive frequency.

Microchemical analysis of selenium in otoliths of two West Virginia fishes captured near mountaintop removal coal mining operations.

Otoliths, calcified inner ear structures, were collected from creek chubs (Semotilus atromaculatus) and green sunfish (Lepomis cyanellus) living in mountaintop mining-impacted and reference streams and analyzed for selenium (Se) content using laser ablation-inductively coupled mass spectrometry. Significant differences in otolith Se were found between the 2 fish species. Results from the present study suggest that a retrospective reconstruction of Se concentrations in muscle can be derived from Se concentrations in otoliths in creek chub but not green sunfish, exemplifying the importance of species differences when determining partitioning of Se among specific tissues. Green sunfish otoliths from all sites contained background (<1 µg/g) or low (1-4 µg/g) average concentrations of whole-otolith Se. In contrast, creek chub otoliths from the historically mined site contained much higher (≥5 µg/g) concentrations of Se than for the same species in the unmined site or for the green sunfish. These data suggest that body burdens of Se in fish can vary considerably over time and that both the timing of sampling and species choice could heavily influence Se assessments.

Exposure histories derived from selenium in otoliths of three cold-water fish species captured downstream from coal mining activity.

Establishing exposure to contaminants within a given environment is often difficult for fish species with large home ranges. Chemical analyses of muscle or visceral tissue are useful indicators of recent exposure, but depuration, metabolic transformation, and tissue redistributions can alter temporal resolution. Otoliths are metabolically stable and thus provide complete chemical records within their calcified tissues that, when coupled to the annular structure, can provide temporal resolution for exposure to trace metals. Otoliths from bull trout, cutthroat trout, and mountain whitefish from an area rich in seleniferous soils and with active coal mining activity were analyzed for selenium to determine any history of exposure to elevated levels of selenium. Selenium concentrations in otolith primordia tended to be low, indicating that these fish emerged in low selenium areas. Later life stages showed peaks of high Se concentrations, suggesting that individuals moved into areas of increased selenium later in life. Individuals captured from the same area had a wide variety of selenium exposure profiles, indicating that these fish do not move en masse into and out of high-selenium areas. Year-to-year variability of selenium exposure patterns within an otolith suggests inconsistent utilization of high- and low-selenium areas by the individual. The inconsistent exposure profiles for these fish, in addition to their home range of tens of kilometres, indicate that soft tissue concentrations, while useful indicators of recent exposure, cannot be relied upon to provide a life history recording of exposure.

Laser ablation inductively coupled plasma mass spectrometric analyses of base metals in arctic char (Salvelinus alpinus) otoliths collected from a flooded base metal mine.

Otoliths from arctic char recovered from the water body formed from an abandoned open-pit nickel-copper mine contain a trace element record related to the geology of the immediate watershed, past mining activity in the area, and the fish's diet. Laser ablation inductively coupled plasma mass spectrometric analyses across the annular structure of the otoliths detected trace amounts of nickel, copper, and chromium believed to be related to the metal-bearing, mafic-ultramafic minerals in the pit. Oscillatory strontium, barium, and zinc profiles may reflect changing water temperature, diet, or fish metabolism. Lead was detected in very low concentrations and may be related to anthropogenic influence. This closed lake system provides a unique opportunity to study an introduced exotic species in a setting where neither migration nor recruitment have been possible. The fish have successfully occupied the lake and continue to breed despite the influence of the surrounding rocks and local contamination. The chemical record retained within otoliths provides a method of monitoring trace elements affecting fish on a yearly basis and may be regarded as a useful assessment tool for examining the exposure of wild organisms to trace elements.

Determining exposure history of northern pike and walleye to tailings effluence using trace metal uptake in otoliths.

Determining the effects of mining activity on fish populations is complicated by the uncertainty of fish residency in an affected area. Otoliths are considered to be metabolically inert and can contain complete chemical records of environments in which individuals have lived. When coupled with the annular structure, otoliths provide temporal information to the history of exposure to pollutants. In this preliminary study, northern pike and walleye otoliths collected from two lakes adjacent to base metal mine tailings at Lynn Lake, Manitoba, Canada, were analyzed using laser ablation inductively coupled plasma mass spectrometry to determine background levels of trace metals. The presence of overlapping Zn, Cu, and Pb peaks above background levels in some otoliths is interpreted as a record of elevated levels in the environment. These otoliths provided a record of the history of fish movement into and out of the affected area.

Alkali element uptake in otoliths: a link between the environment and otolith microchemistry.

Otoliths taken from fish in the vicinity of rare element pegmatites in eastern Manitoba, Canada, were analyzed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and found to contain lithium, sodium, rubidium, cesium, and strontium at levels ranging from a few ppm to a few 10s of ppm. In some otoliths, the concentrations varied in correspondence to the annular structure of the otoliths, suggesting a periodicity to their incorporation. This is the first reported detection and resolution of periodic signals of Rb and Cs in otoliths. The correspondence between the elements in the otoliths and surrounding rocks suggests there can be a strong link between the microchemistry of a fish's otoliths and its environment particularly where there are distinctive rock types. These elements may serve as natural markers in certain environments and may be used to characterize and monitor lacustrine environments over a period of time.

Determining residence patterns of rainbow trout using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis of selenium in otoliths.

Toxicological studies are often hampered by concerns of fish residency in the industrial effluent being evaluated. Contaminants in muscle or visceral tissue are useful indicators of recent exposure, but depuration, metabolic transformation, and tissue recompartmentalization of contaminants makes their use as temporal markers tenuous. Otoliths are metabolically stable and can provide temporal resolution for exposure to some elements that are incorporated into their calcified structure, including the divalent cations Sr, Zn, and Mn. Here we provide the first determinations of selenium, an anion in biological systems, in the otoliths of rainbow trout captured from a site receiving runoff with elevated selenium from a coal mine operation. Concentrations of selenium in annual growth zones of otoliths suggest that fish from the mine-impacted system are recent immigrants from nearby reference streams not receiving selenium-bearing effluent.