Polyfluoroalkyl compounds in the aquatic environment: a review of their occurrence and fate

The occurrence and fate of polyfluoroalkyl compounds (PFCs) in the aquatic environment has been recognized as one of the emerging issues in environmental chemistry. PFCs comprise a diverse group of chemicals that are widely used as processing additives during fluoropolymer production and as surfactants in consumer applications for over 50 years. PFCs are known to be persistent, bioaccumulative and have possible adverse effects on humans and wildlife. As a result, perfluorooctane sulfonate (PFOS) has been added to the persistent organic pollutants (POPs) list of the Stockholm Convention in May 2009. However, their homologues, neutral precursor compounds and new PFCs classes continue to be produced. In general, several PFCs from different classes have been detected ubiquitously in the aqueous environment while the concentrations usually range between pg and ng per litre for individual compounds. Sources of PFCs into the aqueous environment are both point sources (e.g., wastewater treatment plant effluents) and nonpoint sources (e.g., surface runoff). The detected congener composition in environmental samples depends on their physicochemical characteristics and may provide information to their sources and transport pathways. However, the dominant transport pathways of individual PFCs to remote regions have not been conclusively characterised to date. The objective of this article is to give an overview on existing knowledge of the occurrence, fate and processes of PFCs in the aquatic environment. Finally, this article identifies knowledge gaps, presents conclusions and recommendations for future work.     

New Fabrics and their Potential Application

Considering fabric filtration, particularly the fabrics and their ability to handle submicron particulate and fumes, it is noted that the value of new developments are measured in terms of both improved operational and economic efficiency. The types of available fibers dictate fabric production characteristics as well as the limits of application for the manufactured fabric.     

Identification of archaeogastropod larvae from a hydrothermal vent community

Dispersal is essential in order that endemic species living in ephemeral, patchy vent environments may persist over evolutionary time. Quantitative field studies of larval dispersal, however, require specieslevel identification of the larval forms because each individual must be distinguished from related vent species, and from non-vent species living in the surrounding deep-sea environment. Methods for culturing these larvae to an identifiable stage have not yet been developed. To solve the larval identification problem for the archaeogastropod molluscs (a prominent component of vent communities), we used a scanning electron microscope (SEM) to image shells of larvae collected in the water column near vents along the East Pacific Rise (9°40′ to 9°50′N; 104°W). Larval shell size, shape and ornamentation were compared to protoconchs retained in juvenile or adult shells of identified species, and used to assign five larval groups unequivocally to species (Cyathermia naticoides Warén and Bouchet, 1989; Neomphalus fretterae McLean, 1981; Clypeosectus delectus McLean, 1989; Rhynchopelta concentrica McLean, 1989; and Lirapex granularis Warén and Bouchet, 1989) and seven groups tentatively to species or genus [Lepetodrilus spp. (three groups); Gorgoleptis sp; Peltospira ?operculata McLean, 1989; and ?Melanodrymia sp. (two groups)].     

Effects of low oxygen concentrations on the hatching and viability of eggs of marine calanoid copepods

Hatching of the eggs of four species of copepods, Acartia tonsa, Labidocera aestiva, Tortanus discaudatus, and Centropages hamatus was suppressed at oxygen concentrations less than 0.02 ml O₂/l. When such eggs were subsequently exposed to normal oxygen concentrations, hatching varied among the species, indicating variability in the capacity of eggs to survive exposure to low oxygen. Incubation of eggs at low oxygen concentrations resulted in an increase in the duration of embryonic development. Experiments were conducted in closed systems and oxygen concentration was determined by thermal conductivity using gas chromatography.     

Environmental signals: synthetic humic substances act as xeno-estrogen and affect the thyroid system of Xenopus laevis

According to outdated paradigms humic substances (HS) are considered to be refractory or inert that do not directly interact with aquatic organisms. However, they are taken up and induce biotransformation activities and may act as hormone-like substances. In the present study, we tested whether HS can interfere with endocrine regulation in the amphibian Xenopus laevis. In order to exclude contamination with phyto-hormones, which may occur in environmental isolates, the artificial HS1500 was applied. The in vivo results showed that HS1500 causes significant estrogenic effects on X. laevis during its larval development and results of semi-quantitative RT-PCR revealed a marked increase of the estrogenic biomarker estrogen receptor mRNA (ER-mRNA). Furthermore, preliminary RT-PCR results showed that the thyroid-stimulating hormone (TSHbeta-mRNA) is enhanced after exposure to HS1500, indicating a weak adverse effect on T3/T4 availability. Hence, HS may have estrogenic and anti-thyroidal effects on aquatic animals, and therefore may influence the structure of aquatic communities and they may be considered environmental signaling chemicals.     

Heterozygosity,growth, and survival of the hard clam,Mercenaria mercenaria,in seagrass vs sandflat habitats

Populations of the hard clam,Mercenaria mercenaria L., sampled from dissimilar, adjacent habitats (October and November 1987), were used to assess environmental effects on associations among multi-locus heterozygosity, growth, and survival. Individuals were collected from three widely separated localities along the east coast of North America with each consisting of a seagrass bed and an adjacent, unvegetated sandflat. Demographic differences between adjacent populations were attributed to habitat type. Samples from intertidal sandflats at two of the localities were dominated by younger individuals than those from seagrass beds. Differential growth between adjacent populations was detected at only one locality wherein seagrass individuals grew faster than those from the sandflat. Allelic frequencies revealed adjacent populations that were genetically homogeneous. Nearly all of the genetic variance (98%) was within populations, yet a small (1.7%), but significant, portion occurred between localities. Observed and expected heterozygosities revealed a deficiency of heterozygotes in all six samples. Inbreeding and small-scale population subdivision were discounted as causative factors because deficiencies were heterogeneous across loci. Multi-locus heterozygosity was not correlated with growth rate in samples from any locality. Using a consensus test, multilocus heterozygosity was positively associated with ageclass in sandflat, but not seagrass, samples. We suggest that heterozygosity-fitness trait associations in marine bivalves are more likely to occur in populations inhabiting more stressful, fluctuating environments