Direct and indirect effects of the invasive crayfish Pacifastacus leniusculus on leaf decomposition and invertebrate communitites

• Author(s): Carvalho, Francisco André Costa ; Pascoal, Cláudia ; Cássio, Fernanda ; Teixeira, Amílcar ; Sousa, Ronaldo Gomes
• Date: 2018
• Persistent ID: https://hdl.handle.net/1822/73120
• Origin: RepositóriUM - Universidade do Minho
• Document Type: Other
• Language: English
• Contributor(s): Universidade do Minho

Description

The crayfish Pacifastacus leniusculus is one of the most problematic invasivespecies in aquatic ecosystems in Europe. The crayfish may play an important role in plant-litter decompositionthrough directconsumption of plant litteror by changing the density and/or the behavior of native invertebratedetritivores.However,these effects remain poorly studiedand may be context dependent.Therefore, we selected two riversinNorthern Portugal(Rabaçal and Tuela) subjected to very low human disturbance, but where P.leniusculuswas recently introduced and is currently spreading. In each river,threedifferent sites where selected according to records of the crayfish density (absent, low density high density). At each site, wemeasureddirect and indirect effectsof P.leniusculuson leaf decompositionusing aset a four-treatmentscontrolling the presence/absence of crayfishin rectangular baskets containing leaf litter and allowing or not the entry of other aquatic benthic invertebrates,by covering the basketswith fine (500 μm poresize) or coarse mesh(5 mm poresize). Results showed differences in both rivers regardingabiotic conditions, mainly conductivity. After 28 days,leaf mass loss was 18% higher in Tuela than in Rabaçal. In Tuela,leaf mass loss was affected by the crayfish presence and crayfish density in situand by theinteractionbetween factors. In Rabaçal,leaf mass loss was significantly affected by crayfish in situdensity and interaction. Crayfish presence increased leaf mass loss in both rivers. Invertebrate abundance, richness, equitabilityand species compositionwereaffected differently in both rivers. Further microbial analyses arebeing performed to better understand the different patterns between rivers. Overall, results indicate that P.leniusculusmay directly alter plant-litter decomposition and affected associated invertebrate communities; however, effects are highly context dependent