State-of-the-art approach on the management of invasive faunistic aquatic alien species: The American bullfrog in Belgium

Invasive alien species are worldwide one of the main reasons for the decline of species in native communities and hence biodiversity. Control or eradication programs are often fragmented leading to cost-inefficient and inadequate results. This paper addresses a state-of-the-art framework of an integrated management approach based on the case study on the control of the American bullfrog in the Flemish region in Belgium. This approach is based on the close cooperation of scientists, policymakers, field managers and conservationists to create a science-based policy in the management of invasive alien species. Innovative applied research poses an important foundation in the steering process to establish efficient control measures. These are integrated in the management process that is coincided with raising awareness and dissemination of information throughout the whole plan. The results are based on 10 years of experience and cooperation in the management of the American bullfrog in Flanders, Belgium. The several stages of which this framework is built are crucial in the strategy to tackle the invasion in the most integrated way and can be transposed to control other invasive aquatic alien animals

Migration, domaine vital et utilisation saisonnière de l'habitat chez le barbeau adulte dans la Meuse mitoyenne

Fourteen adult (F.L. 47,5 -57,0 cm) barbel (Barbus barbus) were radio tagged (40 MHz) in the Border Meuse (Borgharen- Maaseik): 5 in May 2001, 3 in October 2001 and 6 in April 2002. From May 2001 till September 2002 fishes were localised weekly throughout the year and daily in April and May in order to localise spawning grounds and investigate seasonal migrations and habitat use. In winter with flows ranging from 250 to 2.500 m3/s four barbel present at the time were found in the main river bed at all times. Large structures such as boulders and trees were used as shelter. No migrations to different parts of the river occurred. In spring five out seven fishes near Maasmechelen migrated to a spawning ground near one of the islands. Both upstream (0,2 km) and downstream migrations (up to 2,6 km) were observed. The spawning ground was characterised by the presence of fine gravel. Three barbel present in the Geul, a tributary of the Meuse, showed distinctive different migrations towards potential spawning places. Migrations in summer and autumn are directed by changes in flow and habitat suitability. The home ranges of the barbel, ranging from 0,5 to 27,3 km, differ significantly in size between different parts of the river. Microhabitat suitability is determined by water depth, water current, flow and bottom structure. In spring daily migrations of up to 1,1 km are observed. In summer and winter daily migrations are usually limited. Reproduction of barbel in this part of the river Meuse is hypothecated by the availability of fine gravel, high water velocities and hydro peaking in spring. Home ranges of fishes occupying highly structured parts in the river, with continuous availability of suitable habitat for spawning as well as resting and foraging in both summer and winter, are significantly smaller

Feasibility of grass co-digestion in an agricultural digester, influence on process parameters and residue composition

The European Union states that by 2020, 20% of the European energy consumption should come from renewable energy. This study investigated the potential of co-digestion of grass clippings (waste) in a typical Flemish agro-digester characterized by an input of 30% manure, 30% maize silage and 40% side streams. No significant adverse effects in the microbiological functioning of the reactors were detected when 10 to 20% out of the 30% maize input was replaced by grass. However at the highest dosage of grass input, dry matter content and the viscosity of the reactor content increases substantially. These elevated parameters could subsequently be reduced again by enzyme addition in the form of MethaPlus L100, although they remained higher than those of the reference reactor receiving maize. It can be concluded that co-digestion of 20% grass in a typical agricultural digester would not pose any problem if dry matter content and viscosity are improved by the use of an enzyme mixture. This is good news for a region like Flanders, where arable land for (energy) crop production is scarce and where grass wastes remain in many cases unused

eDNA quantification to evaluate bullfrog management

Biological invasions contribute now more than ever to the global homogenization of fauna and flora. Large-scale monitoring programs are therefore needed to detect incipient invasions and to evaluate management interventions. As conventional monitoring methods are constrained by large costs, environmental DNA (eDNA)-based methods are increasingly recognized as valuable monitoring tools. However, accurately estimating species abundance from eDNA concentrations in natural systems remains challenging and consequently hinders their integration in management applications. Here, we used droplet digital PCR (ddPCR) in eDNA surveys to estimate the abundance of invasive American bullfrogs (Lithobates catesbeianus). We first introduced bullfrog tadpoles in natural ponds to assess the relationship between abundances and eDNA concentrations under field conditions. Next, we combined eDNA sampling with fyke netting in naturally colonized ponds to investigate whether bullfrog eDNA concentrations can estimate bullfrog capture success and conventional abundance measures obtained via depletion sampling. Finally, we evaluated eradication measures by comparing bullfrog eDNA concentrations before and after fyke netting. We found a strong linear relationship between the numbers of introduced tadpoles and eDNA concentrations (r2 = 0.988). Bullfrog eDNA concentrations were not only linearly related to the catch-per-unit-effort (r2 = 0.739), but also to conventional abundance estimates (r2 = 0.716), particularly when eDNA concentrations were standardized for pond area (r2 = 0.834) and volume (r2 = 0.888). Bullfrog tadpoles were only captured when eDNA concentrations exceeded 1.5 copies µL-1, indicating that quantitative eDNA analyses enable the localization of breeding ponds. We found a significant reduction in eDNA concentrations after fyke netting proportional to the number of captured bullfrogs. These results demonstrate that eDNA quantification is a reliable tool that accurately estimates bullfrog abundance in natural lentic systems. We show that quantitative eDNA analyses can complement the toolbox of natural resource managers and facilitate the coordination of eradication campaigns targeting alien invasive species.Overview of the collected data types: Experimental ponds Period of collected data: between the 30th of June and the 23rd of July 2021 Types of collected data Species-specific environmental DNA data Water quality variables pH Turbidity pH Pond volumes .. Management ponds Period of collected data: between June and September 2021 Types of collected data Species-specific environmental DNA data Bullfrog depletion sampling data Water quality variables pH Turbidity pH Pond volumes Overview of the way the collected data types were acquired Species-specific eDNA data Primer/probe assay validated for western European usage in Everts et al. (2021). Droplet Digital PCR according to protocol described in Everts et al. (2021). Calculation of final eDNA concentrations according to formula in this article. Water quality data pH and conducitivity were measured from the same volume of water as was filtered for eDNA sampling, using a WTW multiLine® Multi 3620 IDS SET KS1 multimeter. Turbidity was measured from the same volume of water as was filtered for eDNA sampling that was deep-frozen and measured afterwards, using a 2100Q Portable Turbidity meter (Hach®) Bullfrog catch data Bullfrogs were caught using double fyke nets with a mesh size of 8mm, consisting of two fykes interconnected with a seven meters long leader net, each with an initial hoop of 80 x 90 cm followed by three narrowing funnels in each fyke The number of fyke nets and period that they were used per pond were given in Table 1 in the Research Article. Catch-per-unit-effort was for all management ponds where bullfrogs were captured Conventional population size estiamtions were obtained via depletion sampling. Subsampling of the data was necessary to comply with the assumptions, which has been reported extensively in the Research Article. Pond volumes (a detailled description is given in the Appendix of the Research Article) Pond volumes were quantified using a 999 CXI HDSI multibeam (Humminbird®) sonar device and the associated software. Pond volumes of extremely shallow ponds (< 50 cm deep) were quantified using a RTK satellite navigation technique using a Trimble® S6 total station with Trimble® R6 receptors

Using quantitative eDNA analyses to accurately estimate American bullfrog abundance and to evaluate management efficacy

Biological invasions contribute now more than ever to the global homogenization of fauna and flora. Large-scale monitoring programs are, therefore, needed to detect incipient invasions and to evaluate management interventions. As conventional monitoring methods are constrained by large costs, environmental DNA (eDNA)-based methods are increasingly recognized as valuable monitoring tools. However, accurately estimating species abundance from eDNA concentrations in natural systems remains challenging and consequently hinders their integration in management applications. Here, we used droplet digital PCR (ddPCR) in eDNA surveys to estimate the abundance of invasive American bullfrogs (Lithobates catesbeianus). We first introduced bullfrog tadpoles in natural ponds to assess the relationship between abundances and eDNA concentrations under field conditions. Next, we combined eDNA sampling with fyke netting in naturally colonized ponds to investigate whether bullfrog eDNA concentrations can estimate bullfrog capture success and conventional abundance measures obtained via depletion sampling. Finally, we evaluated eradication measures by comparing bullfrog eDNA concentrations before and after fyke netting. We found a strong linear relationship between the numbers of introduced tadpoles and eDNA concentrations (r2 = 0.988). Bullfrog eDNA concentrations were not only linearly related to the catch-per-unit-effort (r2 = 0.739), but also to conventional abundance estimates (r2 = 0.716), particularly when eDNA concentrations were standardized for pond area (r2 = 0.834) and volume (r2 = 0.888). Bullfrog tadpoles were only captured when eDNA concentrations exceeded 1.5 copies µl−1, indicating that quantitative eDNA analyses enable the localization of breeding ponds. We found a significant reduction in eDNA concentrations after fyke netting proportional to the number of captured bullfrogs. These results demonstrate that eDNA quantification is a reliable tool that accurately estimates bullfrog abundance in natural lentic systems. We show that quantitative eDNA analyses can complement the toolbox of natural resource managers and facilitate the coordination of eradication campaigns targeting alien invasive species

Structural and Functional Role of the Disulfide Bridges in the Hydrophobin SC3

Hydrophobins function in fungal development by self-assembly at hydrophobic-hydrophilic interfaces such as the interface between the fungal cell wall and the air or a hydrophobic solid. These proteins contain eight conserved cysteine residues that form four disulfide bonds. To study the effect of the disulfide bridges on the self-assembly, the disulfides of the SC3 hydrophobin were reduced with 1,4-dithiothreitol. The free thiols were then blocked with either iodoacetic acid (IAA) or iodoacetamide (IAM), introducing eight or zero negative charges, respectively. Circular dichroism and infrared spectroscopy showed that after opening of the disulfide bridges SC3 is initially unfolded. IAA-SC3 did not self-assemble at the air-water interface upon shaking an aqueous solution. Remarkably, after drying down IAA-SC3 or after exposing it to Teflon, it refolded into a structure similar to that observed for native SC3 at these interfaces. Iodoacetamide-SC3 on the other hand, which does not contain extra charges, spontaneously refolded in water in the amyloid-like β-sheet conformation, characteristic for SC3 assembled at the water-air interface. From this we conclude that the disulfide bridges of SC3 are not directly involved in self-assembly but keep hydrophobin monomers soluble in the fungal cell or its aqueous environment, preventing premature self-assembly.

Van gras tot groen gas

Gras dat afkomstig is van wegbermen en graslandbeheer wordt vaak als een ongewenste biomassastroom beschouwd waarmee de dag van vandaag weinig gedaan wordt. Aan de andere kant zijn voor biogasproductie via vergisting vaak dure biomassastromen zoals energiemaïs nodig, welke de economische rendabiliteit van de vergistingsinstallatie onder druk zetten. Het Vlaams-Europese project Graskracht (2010-2012) testte daarom de mogelijkheid van co-vergisting van gras ter vervanging van energiemaïs