A central paradigm in conservation biology is that population bottlenecks reduce genetic diversity and population viability. In an era of biodiversity loss and climate change, understanding the ...determinants and consequences of bottlenecks is therefore an important challenge. However, as most studies focus on single species, the multitude of potential drivers and the consequences of bottlenecks remain elusive. Here, we combined genetic data from over 11,000 individuals of 30 pinniped species with demographic, ecological and life history data to evaluate the consequences of commercial exploitation by 18th and 19th century sealers. We show that around one third of these species exhibit strong signatures of recent population declines. Bottleneck strength is associated with breeding habitat and mating system variation, and together with global abundance explains much of the variation in genetic diversity across species. Overall, bottleneck intensity is unrelated to IUCN status, although the three most heavily bottlenecked species are endangered. Our study reveals an unforeseen interplay between human exploitation, animal biology, demographic declines and genetic diversity.
For understanding and assessing aerosol–cloud
interactions and their impact on climate, reliable measurement data on
aerosol particle hygroscopicity and cloud condensation nuclei (CCN) activity
are ...required. The CCN activity of aerosol particles can be determined by
scanning particle size and supersaturation (S) in CCN measurements. Compared
to an existing differential mobility analyzer (DMA) with CCN activity
measurement, a broad supersaturation scanning CCN (BS2-CCN) system, in which
particles are exposed to a range of S simultaneously, can measure the CCN
activity with a high time resolution. Based on a monotonic relation between
the activation supersaturation of aerosol particles (Saerosol) and the
activated fraction (Fact) of the BS2-CCN measurement, we can derive
κ, a single hygroscopicity parameter, directly. Here, we describe
how the BS2-CCN system can be effectively calibrated and which factors can
affect the calibration curve (Fact−Saerosol). For calibration,
size-resolved CCN measurements with ammonium sulfate and sodium chloride
particles are performed under three different thermal gradient (dT)
conditions (dT=6, 8, and 10 K). We point out key processes that can affect
the calibration curve and thereby need to be considered as follows: first,
the shape of the calibration curve is primarily influenced by Smax, the
maximum S in the activation tube. We need to determine appropriate Smax
depending on the particle size and κ to be investigated. To minimize the
effect of multiply charged particles, a small geometric mean diameter
(Dg) and geometric standard deviation (σg) in
number size distribution are recommended when generating the calibration
aerosols. Last, Fact is affected by particle number concentration and
has a decreasing rate of 0.02 per 100 cm−3 due to
the water consumption in the activation tube. For evaluating the BS2-CCN
system, intercomparison experiments between typical DMA-CCN and BS2-CCN
measurements were performed with a laboratory-generated aerosol mixture and
ambient aerosols. Good agreement of κ values between DMA-CCN and
BS2-CCN measurements for both experiments shows that the BS2-CCN system can
measure CCN activity well compared to the existing measurement method and can
measure a broad range of hygroscopicity distributions with a high
time resolution (∼1 s vs. a few minutes for a standard CCN
activity measurement). As the hygroscopicity can be used as a proxy for the
chemical composition, our method can also serve as a complementary approach
for fast and size-resolved detection and estimation of aerosol chemical
composition.
Stir bar sorptive extraction (SBSE) is an equilibrium extraction method used amongst others for the analysis of polycyclic aromatic hydrocarbons (PAH) in aqueous samples. We compared SBSE to ...liquid–liquid extraction (LLE) for aqueous eluates obtained from batch and column tests of PAH contaminated soils to check whether SBSE might be considered as an alternative sample preparation method. We used soils with different particle size distribution, organic matter content, and resulting eluate turbidity to test the sample preparation methods on eluates with matrices of varying complexity. Furthermore, we studied the influence of diluted organic matter (DOM) on the PAH sorption process to the polymer coating of the stir bar during SBSE. In the majority of cases, we found higher PAH concentrations (up to 288%) with SBSE than with LLE. The turbidity correlates with the difference in PAH results, i.e. the greater the turbidity in the eluate, the more PAH we found with SBSE compared to LLE. We observed no similar trend regarding the amount of total organic carbon (TOC). The presence of DOM in the eluate seems to hamper the SBSE slightly, the PAH recovery varied between 82 and 104%.
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