Limited genomic signatures of population collapse in the critically endangered black abalone (Haliotis cracherodii).

The black abalone, Haliotis cracherodii, is a large, long-lived marine mollusc that inhabits rocky intertidal habitats along the coast of California and Mexico. In 1985, populations were impacted by a bacterial disease known as withering syndrome (WS) that wiped out >90% of individuals, leading to the closure of all U.S. black abalone fisheries since 1993. Current conservation strategies include restoring diminished populations by translocating healthy individuals. However, population collapse on this scale may have dramatically lowered genetic diversity and strengthened geographic differentiation, making translocation-based recovery contentious. Additionally, the current prevalence of WS remains unknown. To address these uncertainties, we sequenced and analysed the genomes of 133 black abalone individuals from across their present range. We observed no spatial genetic structure among black abalone, with the exception of a single chromosomal inversion that increases in frequency with latitude. Outside the inversion, genetic differentiation between sites is minimal and does not scale with either geographic distance or environmental dissimilarity. Genetic diversity appears uniformly high across the range. Demographic inference does indicate a severe population bottleneck beginning just 15 generations in the past, but this decline is short lived, with present-day size far exceeding the pre-bottleneck status quo. Finally, we find the bacterial agent of WS is equally present across the sampled range, but only in 10% of individuals. The lack of population genetic structure, uniform diversity and prevalence of WS bacteria indicates that translocation could be a valid and low-risk means of population restoration for black abalone species' recovery.

Limited genomic signatures of population collapse in the critically endangered black abalone (Haliotis cracherodii).

The black abalone, Haliotis cracherodii, is a large, long-lived marine mollusc that inhabits rocky intertidal habitats along the coast of California and Mexico. In 1985, populations were impacted by a bacterial disease known as withering syndrome (WS) that wiped out >90% of individuals, leading to the species' designation as critically endangered. Current conservation strategies include restoring diminished populations by translocating healthy individuals. However, population collapse on this scale may have dramatically lowered genetic diversity and strengthened geographic differentiation, making translocation-based recovery contentious. Additionally, the current prevalence of WS is unknown. To address these uncertainties, we sequenced and analyzed the genomes of 133 black abalone individuals from across their present range. We observed no spatial genetic structure among black abalone, with the exception of a single chromosomal inversion that increases in frequency with latitude. Genetic divergence between sites is minimal, and does not scale with either geographic distance or environmental dissimilarity. Genetic diversity appears uniformly high across the range. Despite this, however, demographic inference confirms a severe population bottleneck beginning around the time of WS onset, highlighting the temporal offset that may occur between a population collapse and its potential impact on genetic diversity. Finally, we find the bacterial agent of WS is equally present across the sampled range, but only in 10% of individuals. The lack of genetic structure, uniform diversity, and prevalence of WS bacteria indicates that translocation could be a valid and low-risk means of population restoration for black abalone species' recovery.

Determination of phosphorus and sulfur in uranium ore concentrates by triple quadrupole inductively coupled plasma mass spectrometry.

The analysis of impurities in a uranium ore concentrate (UOC) could provide information regarding the source, production history, and potential intended use of the UOC. This study involves the analysis of UOC samples for phosphorus and sulfur. Concentrations were determined by triple quadrupole inductively coupled plasma - mass spectrometry and compared with results from a pyrohydrolysis method as well as previously reported results. The sulfur and phosphorus concentrations, determined by the mass spectrometer, were used to explore possible trends in a series of UOC material, and the uncertainties were calculated using GUM workbench software. The triple quadrupole inductively coupled plasma - mass spectrometer method allows for the removal of interferences in the analysis of species.

Metal accumulation in dragonfly nymphs and crayfish as indicators of constructed wetland effectiveness.

Constructed wetland effectiveness is often assessed by measuring reductions of contaminant concentrations in influent versus departing effluent, but this can be complicated by fluctuations in contaminant content/chemistry and hydrology. We assessed effectiveness of a constructed wetland at protecting downstream biota from accumulating elevated metal concentrations-particularly copper and zinc in effluents from a nuclear materials processing facility. Contaminants distributed throughout a constructed wetland system and two reference wetlands were assessed using six dragonfly nymph genera (Anax, Erythemis, Libellula, Pachydiplax, Tramea, and Plathemis) as biomonitors. Additionally, the crayfish, Cambarus latimanus, were analyzed from the receiving and two reference streams. Concentrations of Cu, Zn, Pb, Mn, Cr, Cd, and Al were evaluated in 597 dragonfly nymph and 149 crayfish whole-body composite samples. Dragonfly genera varied substantially in metal accumulation and the ability to identify elevated metal levels throughout components of the constructed wetland. Genera more closely associated with bottom sediments tended to accumulate higher levels of metals with Libellula, Pachydiplax, and Erythemis often accumulating highest concentrations and differing most among sites. This, combined with their abundance and broad distributions make the latter two species suitable candidates as biomonitors for constructed wetlands. As expected, dragonfly nymphs accumulated higher metal concentrations in the constructed wetland than reference sites. However, dragonfly nymphs often accumulated as high of metal concentrations downstream as upstream of the water treatment cells. Moreover, crayfish from the receiving stream near the constructed wetland accumulated substantially higher Cu concentrations than from downstream locations or reference streams. Despite reducing metal concentrations at base flow and maintaining regulatory compliance, metal fluxes from the wetland were sufficient to increase accumulation in downstream biota. Future work should evaluate the causes of downstream accumulation as the next step necessary to develop plans to improve the metal sequestering efficiency of the wetland under variable flow regimes.

Basins, beaver ponds, and the storage and redistribution of trace elements in an industrially impacted coastal plain stream on the Savannah River Site, SC, USA.

Accumulation of eleven trace elements in sediment was evaluated throughout an industrially disturbed headwater stream on the Savannah River Site, SC, USA. Sampling began at upstream sedimentation basins at the margins of industrial areas, continued longitudinally downstream to a beaver pond representing a potential sink in the mid-reaches, and ended in downstream reaches. Additionally, sediment from beaver impacted areas in another industrially disturbed stream and a reference stream were analyzed to assess the natural tendency of these depositional features to settle out trace elements. We further compared trace element accumulation in sediment and biota from downstream reaches before and after an extreme rainy period to evaluate the potential redistribution of trace elements from sink areas. Trace elements accumulated in the headwater basins from which elements were redistributed to downstream reaches. The mid-reach beaver affected area sediments accumulated elevated concentrations of most analyzed elements compared to the free-flowing stream. The elevated accumulation of organic matter in these sink areas illustrated the effectiveness of reduced water velocity areas to settle out materials. The natural tendency of beaver ponds to accumulate trace elements and organic matter was further illustrated by sediments from the reference beaver pond accumulating higher concentrations of several elements than sediments from the free flowing section the stream impacted by industrial activity. However, concentrations in sediment from sedimentation basins and the beaver impacted area of the disturbed stream were highest. Trace elements and organic matter appeared to be redistributed from the sinks after the record rainy period resulting in increased trace element concentrations in both sediment and biota. These data suggest that assessments of contaminants in stream systems should include such slow-water, extreme depositional zones such as beaver impacted areas or basins to verify what contaminants may be pulsing through the stream.

Stability of silver nanoparticle sulfidation products.

The adoption of silver nanoparticles in consumer goods has raised concerns about the potential environmental harm of their widespread use. We studied chemical transformations that Ag NPs may undergo as they pass through sulfide-rich conditions common in waste water treatment plants (WWTPs), which may limit the release of Ag+ from Ag NPs due to the formation of low-solubility silver sulfide (Ag2S). However, it is uncertain whether sulfidation is complete and if sulfidized Ag NPs continue to release Ag+. To address these uncertainties, we monitored the reaction of Ag NPs with various levels of sulfide with an ion selective electrode and UV/visible spectrophotometry over the course of two months. We characterized the products of the sulfidation reactions with a purge-and-trap acid volatile sulfide (AVS) analysis, which served as a measure of the stability of the sulfidized products because sulfide would be readily lost to oxidation unless it is stabilized as Ag2S. The Ag NP surface plasmon resonance (SPR) absorbance peak was initially diminished and then returned over the course of several days after reaction with limited amounts of sulfide, suggesting a dynamic system that may retain some characteristics of the pristine Ag NPs. However, ICP-MS analysis of sulfidized Ag NP suspensions over a two-month period demonstrates that sulfidation limits the release of Ag+ ions from nanosilver that pass through a WWTP, even when sulfide concentrations are limited relative to silver.

Sediment and biota trace element distribution in streams disturbed by upland industrial activity.

Extensive industrial areas in headwater stream watersheds can severely impact the physical condition of streams and introduce contaminants. We compared 3 streams that received stormwater runoff and industrial effluents from industrial complexes to 2 reference streams. Reference streams provide a benchmark of comparison of geomorphic form and stability in coastal plain, sandy-bottomed streams as well as concentrations of trace elements in sediment and biota in the absence of industrial disturbance. We used crayfish (Cambarus latimanus, Procambarus raneyi, Procambarus acutus) and crane fly larvae (Tipula) as biomonitors of 15 trace elements entering aquatic food webs. Streams with industrial areas were more scoured, deeply incised, and less stable. Sediment organic matter content broadly correlated to trace element accumulation, but fine sediments and organic matter were scoured from the bottoms of disturbed streams. Trace element concentrations were higher in depositional zones than runs within all streams. Despite contaminant sources in the headwaters, trace element concentrations were generally not elevated in sediments of the eroded streams. However, element concentrations were frequently elevated in biota from these streams with taxonomic differences in accumulation amplified. In eroded, sand-bottomed coastal plain streams with unstable sediments, single snapshots of sediment trace element concentrations did not characterize well bioavailable trace elements. Biota that integrated exposures over time and space within their home ranges better detected bioavailable contaminants than sediment. Environ Toxicol Chem 2019;38:115-131. © 2018 SETAC.