In aquatic ecosystems invasive species are among the most important threats to biodiversity worldwide. Understanding the dispersal mechanisms of aquatic invaders is very important for protection and management of vulnerable water bodies. Here we ask how recreational boats that are transported overland could contribute to the dispersal of invasive zebra mussels among lakes in Switzerland. Using a questionnaire sent to registered boat owners, we surveyed properties of transported boats and collected information on self-reported mussel fouling and transport activities of boat owners. We also sampled boat hulls at launching ramps and harbors for biofouling invertebrates. Boats that were kept seasonally or yearround in water were found to have high vector potential with mussel fouling rates of more than 40 %. However, only about 6 % of boats belonging to these groups were transported overland to other water bodies. Considering that approximately 100,000 recreational boats are registered in Switzerland, we estimated that every year around 1400 boats fouled with mussels are transported overland. Such boats pose a high risk of distributing zebra mussels between water bodies. Our results suggest that there is a considerable risk that recreational boats may spread new fouling species to all navigable water bodies within the study area. We speculate that one such species could be the quagga mussel, which has not yet invaded lakes in Switzerland. On a more positive note, our study has identified the group of high-risk boats so that possible control measures would only affect a relatively small number of boat owners.

Harbours are known introduction foci of marine alien species. They act as recipients of new introductions and as sources for regional spread. We report on subtidal surveys of fouling communities from 14 harbours along the coastline of South Africa that were used to identify predictors of high alien species numbers in support of prioritisation of monitoring actions by authorities. The harbours varied in nature from large, international shipping hubs to small, regional fishing harbours and recreational marinas. Fouling assemblages were assessed using visual and scrape sampling to ensure the detection of large, mobile and small inconspicuous species. In total, 29 alien species were recorded, 15 of which were detected outside of their previously known ranges. The number of species recorded per harbour varied from five to. Results revealed that high numbers of alien species were associated with the presence of yachts and low primary productivity. Harbours which had yachts and occurred in areas with mean Chl a minimum levels lower than 0.21 mg.m -3 had the highest number of alien species, while harbours without yachts that were larger than 0.1km 2 supported the fewest alien species. These findings suggest that the presence of yachts can be used to identify harbours with high numbers of alien species, particularly in regions with low productivity. While the applicability of these findings to other regions remains to be tested, this work suggests that harbours that fall within this category could be prioritised for monitoring of marine alien species.

Regulated cell proliferation is a crucial prerequisite for Schwann cells to achieve myelination in development and regeneration. In the present study, we have investigated the function of the cell cycle inhibitors p21 and p16 as potential regulators of Schwann cell proliferation, using p21- or p16-deficient mice. We report that both inhibitors are required for proper withdrawal of Schwann cells from the cell cycle during development and following injury. Postnatal Schwann cells express p21 exclusively in the cytoplasm, first detectable at postnatal day 7. This cytoplasmic p21 expression is necessary for proper Schwann cell proliferation control in the late development of peripheral nerves. After axonal damage, p21 is found in Schwann cell nuclei during the initiation of the proliferation period. This stage is critically regulated by p21, since loss of p21 leads to a strong increase in Schwann cell proliferation. Unexpectedly, p21 levels are upregulated in this phase suggesting that the role of p21 may be more complex than purely inhibitory for the Schwann cell cycle. However, inhibition of Schwann cell proliferation is the overriding crucial function of p21 and p16 in peripheral nerves as revealed by the consequences of loss-of-function in development and after injury. Different mechanisms appear to underlie the inhibitory function, depending on whether p21 is cytoplasmic or nuclear.

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Species level identifications of morphologically simple marine algae have undoubtedly caused biodiversity assessments to be an arduous task. The green algal genus Ulva L., 1753, is notorious for morphological plasticity and cryptic speciation. We used two chloroplast-encoded (rbcL and tufA) molecular markers and the nuclear internal transcribed spacer 1 (ITS1) of the ribosomal cistron to detect Ulva ohnoi M. Hiraoka and S. Shimada, 2004, a species known for forming green tides in Japan, as a new record for the Western Atlantic, including the Gulf of Mexico (GoMX) and Atlantic coast of Florida. All rbcL sequences from this investigation were identical to reports for U. ohnoi. The Western Atlantic isolates showed relatively low genetic diversity in tufA and ITS1 sequences, which suggests that this species is not native to the GoMX and Atlantic Florida. Furthermore, we have identified U. ohnoi as the species that formed an ephemeral, localized overgrowth during July of 2013 in Biscayne Bay, Florida, an area with a persistent bloom of two other green algal species, Anadyomene stellata J. V. Lamouroux, 1812, and Anadyomene sp., due to eutrophication from anthropogenic nutrient loading near canals. A tissue nutrient analysis of samples from this overgrowth of Ulva showed that this species has a high affinity for nitrogen, especially ∂15N, which suggests anthropogenic sources of N. Further investigations are needed to assess the geographical ranges of this species in this region as well as the potential invasiveness of this alga in the Western Atlantic. It is highly recommended to monitor the abundance of this species in response to nutrient discharges in Biscayne Bay.

Harbours are known introduction foci of marine alien species. They act as recipients of new introductions and as sources for regional spread. We report on subtidal surveys of fouling communities from 14 harbours along the coastline of South Africa that were used to identify predictors of high alien species numbers in support of prioritisation of monitoring actions by authorities. The harbours varied in nature from large, international shipping hubs to small, regional fishing harbours and recreational marinas. Fouling assemblages were assessed using visual and scrape sampling to ensure the detection of large, mobile and small inconspicuous species. In total, 29 alien species were recorded, 15 of which were detected outside of their previously known ranges. The number of species recorded per harbour varied from five to. Results revealed that high numbers of alien species were associated with the presence of yachts and low primary productivity. Harbours which had yachts and occurred in areas with mean Chl a minimum levels lower than 0.21 mg.m -3 had the highest number of alien species, while harbours without yachts that were larger than 0.1km 2 supported the fewest alien species. These findings suggest that the presence of yachts can be used to identify harbours with high numbers of alien species, particularly in regions with low productivity. While the applicability of these findings to other regions remains to be tested, this work suggests that harbours that fall within this category could be prioritised for monitoring of marine alien species.

Toxic cyanobacteria, such as Planktothrix rubescens, came to dominate temperate lakes in the mid‐to‐late 20th century, as a result of eutrophication. Even after decades of re‐oligotrophication, where phosphorus levels were reduced by 1–2 orders of magnitude, P. rubescens remains present in various lakes. In this study, we examine the persistence and changes of P. rubescens deep chlorophyll maximum (DCM) in Lake Hallwil (Switzerland) over 35 yr of steadily decreasing phosphorous concentrations. Although lake transparency increased and the euphotic layer deepened during this period, the P. rubescens population maximum moved even deeper. It is now found ca. 7.7 m deeper than its shallowest position in the 2000s, and this depth no longer coincides with the depth of maximal water column stability. P. rubescens neutral buoyancy has now driven it beneath the stable metalimnion into the hypolimnion, where buoyancy regulation is restricted due to reduced metabolic activity at low light and low temperature. If P. rubescens DCM continues to deepen each year, it will eventually reach a region of lower stability in the hypolimnion where turbulent conditions are strong enough to disperse the DCM. We also explore the mechanisms that ensure P. rubescens ongoing presence in peri‐alpine lakes despite strong re‐oligotrophication and ongoing climate change. We find that P. rubescens in the lake is mainly sustained by growth during fully mixed conditions in winter, not during stratification in summer. This may contradict another commonly made prediction that periods of longer stratification will promote future blooms of this cyanobacterium.