Flight distance of mosquitoes (Culicidae): A metadata analysis to support the management of barrier zones around rewetted and newly constructed wetlands

Society responds to changes in climate and land use via mitigation measures, including rainwater retention and storage in rewetted and newly constructed wetlands. Humans living close to these wetlands express concerns about future mosquito nuisance situations, and request the necessary distance between human occupation and wetlands to avoid such problems. Wetland managers need to know the distance required, as well as the type of management needed for such buffer or barrier zones. Here we performed an extensive literature survey to collect quantitative information on mosquito flight distance and the relevant environmental conditions. Mosquitoes have an average maximum flight distance of between 50 m and 50 km, depending on the species. Long-distance or migratory flights are strongly related to species ecological preferences and physiology, are survived by few specimens, and do not relate to nuisance situations. Nuisance-related or non-oriented flights are also species-specific and cover much shorter distances-between 25 m and 6 km for the 23 species analyzed. Based on these results, we made regression-based estimations of the percentages of the population that cross certain distances. A 90% reduction in breeding site population density would require minimal distances of 56 m for Anopheles saperoi and 8.6 km for Anopheles sinensis, and much greater distances for Aedes vexans, Culex quinquefasciatus, and Culiseta morsitans. Little useful information was available regarding the environmental conditions under which non-oriented flights took place. Qualitatively, the review showed that flight capacity was influenced by landscape structure, meteorological conditions (temperature, humidity, and illumination), and species physiology (energy available for flight). Overall, our findings suggest that predictions regarding the construction of barrier zones around breeding sites can be made based on mosquito and host density and human nuisance perception, and that barrier zone usefulness strongly depends on the mosquito species involved. Additional quantitative research is needed to better document the non-oriented dispersal patterns of the mosquitoes that populate rewetted and newly constructed wetlands, and the effects of vegetation types in barrier zones on mosquito densities. (C) 2013 Elsevier GmbH. All rights reserved

Stekende insecten Griendtsveen : situatie 2015

Naar aanleiding van het advies van de Tijdelijke Adviescommissie LIFE+ Mariapeel om een onderzoek naar de muggenoverlast te verrichten is door de gemeente Horst aan de Maas gezamenlijk met de provincie Limburg een onderzoeksopdracht aan Alterra – Wageningen UR verstrekt. Alterra is gevraagd om de muggenoverlast te monitoren en daarmee de nulsituatie vast te stellen, de mate van overlast aan te geven en te adviseren over de effecten van voorgenomen maatregelen op de overlast

Zandsuppletie in de Leuvenumse beek: monitoring van de fysische en biologische effecten 2014-2015

In 2014-2105 zijn de fysische en biologische korte-termijn-effecten van het herhaaldelijk suppleren van zand op een drietal locaties in de Leuvenumse beek onderzocht. Er is gekeken naar de mate van ophoging en verspoeling van het ingebrachte zand, de interactie tussen het zand en houtpakketten, de consequenties van depositie van organisch materiaal als gevolg van verstuwing van de beek en tenslotte naar de effecten op de macrofauna

The significance of refuge heterogeneity for lowland stream caddisfly larvae to escape from drift

The process of macroinvertebrate drift in freshwater lowland streams is characterized by dislodgement, drift distance and subsequent return to the bottom. Refuges are important to all drift phases, since they may help larvae to avoid dislodgement and to escape from drift, even more so if the refuge structure is complex and heterogeneous. The aim of the present study was therefore to determine the influence of refuge heterogeneity on the ability of caddisfly larvae to return to the bottom from drift and to avoid secondary dislodgement. To this purpose a series of indoor flume experiments were undertaken, testing six Limnephilidae (Trichoptera) species, that occur on a gradient from lotic to lentic environments. Bed morphology (plain, refuges with or without leaf patches) and flow velocity (low (0.1 m/s), intermediate (0.3 m/s) and high (0.5 m/s) were manipulated. We showed that all species were favoured by refuges and that especially for species on the lentic end of the gradient (L. lunatus, L. rhombicus and A. nervosa), the ability to escape from drift and to avoid secondary dislodgement was increased. Moreover, we showed that all species spent more time in refuges than in open channel parts and more time in heterogeneous refuges (leaf patches) than in bare refuges, the latter being especially the case for larvae of the lotic species. For lentic species, not well adapted to high flow velocity, refuges are thus crucial to escape from drift, while for the lotic species, better adapted to high flow velocity, the structure of the refuge becomes increasingly important. It is concluded that refuges may play a crucial role in restoring and maintaining biodiversity in widened, channelized and flashy lowland streams.</p

Flow velocity tolerance of lowland stream caddisfly larvae (Trichoptera)

The process of macroinvertebrate drift in streams is characterized by dislodgement, drift distance and subsequent return to the bottom. While dislodgement is well studied, the fate of drifting organisms is poorly understood, especially concerning Trichoptera. Therefore, the aim of the present study was to determine the ability of six case-building Trichoptera species to return to the stream bottom under different flow velocity conditions in a laboratory flume. The selected species occur in North-West European sandy lowland streams along a gradient from lentic to lotic environments. We determined species specific probability curves for both living and dead (control) specimens to return to the bottom from drift at different flow velocities and established species specific return rates. Species on the lotic end of the gradient had highest return rates at high flow velocity and used active behaviour most efficiently to return to the bottom from drift. The observed gradient of flow velocity tolerance and species specific abilities to settle from drift indicate that, in addition to dislodgement, the process of returning to the bottom is of equal importance in determining flow velocity tolerance of Trichoptera species

Flow thresholds for leaf retention in hydrodynamic wakes downstream of obstacles

Leaves are the major component of terrestrial litter input into aquatic systems. Leaves are distributed by the flow, accumulate in low flow areas, and form patches. In natural streams, stable leaf patches form around complex structures, such as large woody debris. Until now, little is known about flow conditions under which leaf patches persist. This study aims to quantify flow conditions for stable leaf patches and entrainment of leaf patches. We hypothesize that entraining flow processes, such as turbulence, Reynolds stress, or lift forcing (vertical flow velocity), best explain local leaf retention. This study was performed in an unscaled flume experiment, which conditions coincide with conditions found in low-energetic lowland streams. We positioned a wooden obstacle perpendicular to the flow on the bed of the flume. A leaf patch was positioned downstream from the wooden obstacle. The experiment was performed under 5 flow conditions. We monitored leaf patch cover and near-bed flow conditions in the area downstream of the wooden obstacle. We showed that near-bed flow velocities explain leaf retention better than more complex flow velocity derivatives such as turbulence, Reynolds stress, and vertical flow velocity. The entrainment near-bed flow velocity for leaves ranges from 0.037 to 0.050 m/s. Flow velocities frequently exceed those values, even in low-energetic lowland streams. Therefore, complex structures, such as woody debris, create flow conditions to support stable leaf patches. Thus, adding instead of removing obstacles may be a key strategy in restoring biodiversity in deteriorated streams.</p

Optimaliseren herinrichting van diepe plassen : Technisch achtergronddocument bij de MCA Verondiepen, een multicriteria-instrument om locatiekeuze en inrichtingsvariant te optimaliseren

Het nuttig toepassen van grond of baggerspecie kan als kans worden gezien in gebiedsontwikkeling of natuurontwikkeling in en rond een diepe plas. Om een optimale keuze voor inrichting en functie te kunnen maken, moeten verschillende aspecten worden afgewogen. Hiervoor is de MCA Verondiepen ontwikkeld, een multicriteria-instrument om stakeholders op een gestructureerde wijze een analyse te kunnen doen van de huidige functie en kwaliteit, impact van herinrichting, en mogelijke nieuwe functie en kwaliteit. De toepassing van de MCA Verondiepen wordt geïllustreerd aan de hand van verschillende praktijkvoorbeelden. Dit document bevat achtergrondinformatie bij een excelinstrument