PRIMARY RESEARCH PAPER Invasive Salix fragilis: altered metabolic patterns in Australian streams Paul J. McInerney . Gavin N. Rees . Ben Gawne . Phil Suter Received: 2 July 2015 / Revised: 24 August 2015 / Accepted: 18 September 2015 / Published online: 30 September 2015 Ó Springer International Publishing Switzerland 2015 Abstract Willows (Salix spp.) are listed as a weed of national significance in Australia. Despite this recog- nition, functional effects of willows on streams compared to native species are largely unknown. Leaves supply carbon to instream food webs, but may also act as surfaces for biofilm, and thus can contribute in different ways to stream metabolism. Salix fragilis L. and Eucalyptus camaldulensis Dehnh. leaves that had been colonised by biofilms were placed into chambers in laboratory conditions, and metabolic rates were measured. Gross Primary Production (GPP) of biofilms on E. camaldulensis leaves after 10 days of incubation were significantly greater than biofilms on S. fragilis leaves. S. fragilis leaves displayed greater rates of microbial decomposition per leaf mass. Autotrophic biomass was one hundred fold greater on E. camaldulensis leaves. The biofilm on E. camaldulensis leaves is likely to support a greater population of grazers, compared to S. fragilis. The alien S. fragilis leaves, therefore, are fuelling a different component of the food web to endemic E. camaldulensis leaves. Endemic Eucalyptus spp. leaves play an important role in temperate Australian streams as a substrate for autotrophic growth and provide a year round pathway for carbon to reach secondary invertebrate consumers. Keywords Invasive Á Leaves Á Willows Á Production Á Respiration Á Freshwater Introduction Globalisation and climate change increasingly drive altered biological communities that become composed of species which do not share long evolutionary histories (Sax et al., 2007). The effects of these non- endemic taxa on ecosystem function are often not well understood (Strayer et al., 2006). Invasive plant species are known to decrease the diversity of endemic plants (Gaertner et al., 2009), increase ecosystem productivity (Ehrenfeld, 2010) and alter the rate of nutrient cycling (Liao et al., 2008). At the broadest scale, a global meta-analysis of ecological impacts of invasive alien plants to endemic communities recog- nised that invasive plant species lead to decreased abundance and diversity of resident species and enhanced productivity and ecosystem processing (Vila ` et al., 2011). Handling editor: Stefano Amalfitano P. J. McInerney (&) Á G. N. Rees Á B. Gawne Murray Darling Freshwater Research Centre, P.O. Box 991, Wodonga, VIC 3689, Australia e-mail: P.McInerney@latrobe.edu.au P. J. McInerney Á P. Suter La Trobe University, P.O. Box 991, Wodonga, VIC 3689, Australia G. N. Rees CSIRO Land and Water, P.O. Box 991, Wodonga, VIC 3689, Australia 123 Hydrobiologia (2016) 767:267–277 DOI 10.1007/s10750-015-2507-7