Crayfish as trophic agents: Effect ofAustropotamobius torrentiumon zoobenthos structure and function in small forest streams

Abstract

Crayfish are among the largest and most threatened invertebrates in freshwater habitats. Due to their size, behaviour and feeding activity they may affect structure and function of aquatic ecosystems and their organisms. Despite their importance in many freshwaters and available information on their ecology for several species little is known about the European crayfish Austropotamobius torrentium. In order to evaluate the potential effects of indigenous crayfish presence on the structural and functional composition of the zoobenthic community, we measured population size and densities of three A. torrentium populations and compared macroinvertebrate assemblages and physicochemical parameters in three streams with and three without crayfish. The experimental setup considered crayfish effects at a large scale in defined reaches of pristine headwaters in association with the whole benthic fauna under natural conditions. Presence of A. torrentium significantly affected zoobenthic abundance, diversity and the relative proportions of functional feeding groups. In crayfish streams, especially Trichoptera and collector gatherers were more abundant and diverse, while sites without crayfish had significantly higher abundances and diversities of shredders and wood feeders. Our study provided strong evidence that the presence of the indigenous crayfish A. torrentium had important effects on the trophic cascades of headwater stream communities. Les écrevisses sont parmi les invertébrés les plus menacés dans les habitats aquatiques. En raison de leur taille, de leur comportement et de leur nourriture, elles peuvent modifier la structure et le fonctionnement des écosystèmes aquatiques. Malgré leur importance dans beaucoup de milieux d'eau douce et les connaissances disponibles pour plusieurs espèces, peu de chose est connu sur l'écrevisse européenne Austropotamobius torrentium. Pour évaluer les effets potentiels de la présence de l'écrevisse indigène sur la structure spécifique et fonctionnelle de la communauté du zoobenthos, nous avons évalué les taille et densité de population de trois populations d'A. torrentium et comparé les assemblages de macroinvertébrés et les paramètres physico-chimiques dans trois ruisseaux avec écrevisses et trois sans écrevisses. Le dispositif expérimental considère les effets de l'écrevisse à une large échelle dans des tronçons de tête de bassin vierges de Article published by EDP Sciences M. Weinländer and L. Füreder: Knowl. Managt. Aquatic Ecosyst. (2011) 401, 22 tout impact en association avec l'ensemble de la faune benthique dans ces conditions naturelles. La présence d'A. torrentium affecte significativement l'abondance du zoobenthos, sa diversité et les proportions relatives des groupes fonctionnels du réseau trophique. Dans les ruisseaux avec écrevisses, les trichoptères en particulier et les filtreurs sont plus abondants et variés, alors que dans les sites sans écrevisses l'abondance des brouteurs et décomposeurs de bois est significativement plus élevée. Notre étude montre clairement ...

The decline of endangered stone crayfish (Austropotamobius torrentium) in southern Germany is related to the spread of invasive alien species and land‐use change

“…The submerged roots of broad‐leafed trees stabilize shelters for juvenile and adult stone crayfish against strong currents, decrease bank erosion, favour heterogeneous flow patterns, and may accumulate food particles, whereas pools constitute potential refuges during droughts (Souty‐Grosset et al ., ; Füreder, ). Foliage input from broad‐leafed trees and shrubs also supports food webs in headwater streams with direct or indirect positive trophic effects on stone crayfish (Weinländer and Füreder, ). Therefore, stone crayfish populations benefit from riparian buffers composed of broad‐leafed woods in many ways (Souty‐Grosset et al ., ; Füreder, ; Chucholl and Dehus, ).…”

“…Among these three species it has the smallest natural distribution range, and is the most ecologically demanding in that the species is mostly confined to mid‐to‐high elevation lotic habitats with stony substrata and good water quality (Bohl, ; Streissl and Hödl, ; Pöckl and Streissl, ; Pârvulescu et al ., ; Svobodová et al ., ; Kouba et al ., ). In these headwater habitats, stone crayfish represent a keystone species that structures species composition and trophic pathways (Weinländer and Füreder, ). In addition, stone crayfish are hosts to several native species of branchiobdellid worms that depend on crayfish and are of conservation concern because of declining host populations (Nesemann, ).…”

The effects of decapod crustacean macroconsumers on leaf detritus processing and colonization by invertebrates in stream habitats: A meta‐analysis

“…The huge body of literature available on community-wide effects of native and exotic crayfish in European autotrophic systems (e.g. [57,81,82]) actually testifies to strong impacts on lower trophic levels, indicating that this group has the potential to play a crucial functional role also in heterotrophic systems. International Review of Hydrobiology 2013, 98, 206-216…”

Causes and consequences of crayfish extinction: Stream connectivity, habitat changes, alien species and ecosystem services

“…Crayfish are often considered good indicators of freshwater ecosystem quality and functioning (Grandjean, Momon, & Bramard, 2003;Nardi et al, 2005). They play a fundamental role in maintaining structure and equilibrium within benthic communities (Weinlander & Fureder, 2011), especially considering their large biomass (Richman et al, 2015). Freshwater crayfish are found in a wide variety of habitats and have significant economic importance in some areas (Jones, Andriahajaina, Ranambinintsoa, Hockley, & Ravoahangimalala, 2006;Westman, 1998).…”