A roadmap for the conservation of freshwater mussels in Europe

Europe has a long history of human pressure on freshwater ecosystems. As pressure continues to grow and new threats emerge, there is an urgent need for conservation of freshwater biodiversity and its ecosystem services. However, whilst some taxonomic groups, mainly vertebrates, have received a disproportionate amount of attention and funds, other groups remain largely off the public and scientific radar. Freshwater mussels (Bivalvia, Unionida) are an alarming example of this conservation bias and here we point out six conceptual areas that need immediate and long-term attention: knowledge, threats, socioeconomics, conservation, governance and education. The proposed roadmap aims to advance research, policy and education by identifying the most pressing priorities for the short- and long-term conservation of freshwater mussels across Europe.     

Assessment of non-occupational exposure to polycyclic aromatic hydrocarbons through personal air sampling and urinary biomonitoring

Non-occupational inhalation and ingestion exposure to polycyclic aromatic hydrocarbons (PAHs) has been studied in 8 non-smoking volunteers through personal air sampling and urinary biomonitoring. The study period was divided into 4 segments (2 days/segment), including weekdays with regular commute and weekends with limited traffic related exposures; each segment had a high or low PAH diet. Personal air samples were collected continuously from the subjects while at home, at work, and while commuting to and from work. All urine excretions were collected as individual samples during the study. In personal air samples, 28 PAHs were measured, and in urine samples 9 mono-hydroxylated metabolites (OH-PAHs) from 4 parent PAHs (naphthalene, fluorene, phenanthrene and pyrene) were measured. Naphthalene was found at higher concentrations in air samples collected at the subjects' residences, whereas PAHs with four or more aromatic rings were found at higher levels in samples taken while commuting. Urinary OH-PAH biomarker levels increased following reported high inhalation and/or dietary exposure. On days with a low PAH diet, the total amount of inhaled naphthalene during each 24-hour period was well correlated with the amount of excreted naphthols, as was, to a lesser extent, fluorene with its urinary metabolites. During days with a high dietary intake, only naphthalene was significantly correlated with its excreted metabolite. These findings suggest that this group of non-occupational subjects were exposed to naphthalene primarily through indoor air inhalation, and exposed to other PAHs such as pyrene mainly through ingestion.     

The dilemma of chromosomal mosaicism in chorionic villus sampling—‘direct’ versus long-term cultures

Chromosomal mosaicism is one of several unanswered dilemmas in first-trimester prenatal diagnosis. We report the course of a pregnancy in which a normal karyotype was detected on direct CVS preparation and fetal blood, 100 per cent trisomy 21 in one long-term CVS culture, and low-rate trisomy 21 mosaicism in a second long-term CVS culture and amniocentesis. The phenotypically normal infant had a 6 per cent mosaicism of trisomy 21. It appears that a persistent low-rate mosaicism in different tissues may be indicative of the true status of the fetus.     

Blooms of surf-zone diatoms along the coast of the Olympic Peninsula,Washington. I. Physiological investigations of Chaetoceros armatum and Asterionella socialis in laboratory cultures

Two species of diatoms, Chaetoceros armatum T. West and Asterionella socialis Lewin and Norris, which account for virtually all of the plant biomass present in the surf zone along the Olympic Peninsula (USA), have been isolated and grown in culture, and comparisons have been made with respect to their physiological behavior in response to aeration, light, temperature, salinity, and nutrients. A. socialis displayed the greater maximum growth rate under most situations, which would give this species a natural advantage over C. armatum. However, in the natural habitat, C. armalum is by far the more important of the two, since the blooms often consist of almost pure stands of this species. This may be due to its apparent ability to use low light levels more efficiently. The maximum growth rate of C. armatum was reached at light levels of 750 to 1000 lux in cultures, whereas A. socialis required a higher light intensity (4000 lux) for maximum growth. C. armatum did not produce its mucilage envelope under any culture conditions. Such a mucilage envelope, with its accompanying clay particles, is invariably present surrounding the diatom chains when they are collected from the natural habitat. The absence of the mucilage envelope (and clay particles) may explain the peculiarities of iron nutrition which were observed in culture experiments, i.e., a dependence on the presence of iron as NaFe-EDTA or ferric citrate, and failure to utilize ferric choloride as a source of Fe for growth.Contribution No. 652 from the Department of Oceanography, University of Washington.     

Persistent blooms of surf diatoms along the Pacific coast,USA

Productivity was studied in two diatom species, Chaetoceros armatum T. West and Asterionella socialis Lewin and Norris, which form persistent dense blooms in the surf zone along the Pacific coast of Washington and Oregon, USA. Past observations have shown that surf-diatom standing stock usually declines in summer along with concentrations of nitrate and ammonium. Using the ¹⁴C method, photosynthetic rates in natural surf samples were measured monthly for one year (October 1981 through September 1982) at a study site on the Washington coast. Also measured were temperature, salinity, dissolved nutrients, particulate carbon and nitrogen (used as estimates of phytoplankton C and N), and chlorophyll a. Assimilation numbers (P _max) were higher in summer (5 to 8 g C g^-1 chl a h^-1) than in winter (3 to 4gC). Specific carbon incorporation rates (µ_max) showed no obvious seasonality, mostly falling within the range of 0.09 to 0.13 g C g^-1 C(POC) h^-1. The discrepancy between the seasonal trends for chlorophyll-specific and carbon-specific rates reflects a change in the carbon-to-chlorophyll ratio. Because of seasonal differences in daylength and light intensity, daily specific growth rates () are thought to be higher in summer than in winter. Neither ammonium enrichment assays nor particulate carbon-to-nitrogen ratios provided convincing evidence for nitrogen limitation during summer, and the observed changes in diatom abundance cannot be explained on this basis. Both the high diatom concentrations and their seasonal variations probably are due mainly to factors other than growth rates; two factors considered important are diatom flotation and seasonal changes in wind-driven water transport. C. armatum usually dominates the phytoplankton biomass in the surf zone, and evidence suggests that this species is strongly dominant in terms of primary production.Contribution No. 1391 of the School of Oceanography, University of Washington, Seattle, Washington, USA