Terrestrial-Aquatic Linkages: Riparian Arthropod Inputs Alter Trophic Cascades in a Stream Food Web

Abstract

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From autochthonous to allochthonous resources: seasonal shifts in food use by stream‐dwellingYOYArctic charrSalvelinus alpinusthrough the ice‐free season

“…Thus, terrestrial insects may constitute an important energy subsidy for YOY S. alpinus during late summer, a period when interspecific interactions from S. salar and C. poecilopus may be high (Gabler & Amundsen, 1999, 2010. The role of terrestrial insects in stream food webs is indisputable (Nakano et al, 1999b), but the extensive contribution of terrestrial prey in the diet of small-sized S. alpinus observed in this study is very high. The consumption of this resource can have a direct consequence on fish growth (Sweka & Hartman, 2008) and facilitate niche partitioning between sympatric fish species through fish segregation in water column use (Nakano et al, 1999a;Sánchez-Hernández et al, 2013).…”

Diurnal feeding strategies of the Ferruginous Duck (Aythya nyroca) in Lake Tonga (Northeastern Algeria)

“…Another kind of behavioral adjustment involves switching search methods (Stephens & Krebs 1986). Short-term switches or the short-term changes in food searching methods were observed and analysed in numerous animal groups as a rapid and reversible adaptation response to different conditions of food availability (Thomas 1974, Davies 1977, Recher et al 1983, Formanowicz & Bradley 1987, Grant & Noakes 1987, Village 1990, Bell 1991, Nakano et al 1999. The Ferruginous Duck is an excellent diver, but we have also highlighted other feeding methods less frequent than diving, but have crucial importance in the subventions of nutritional needs.…”

Getting quantitative about consequences of cross-ecosystem resource subsidies on recipient consumers

“…As several authors have demonstrated, subsidies (or their exclusion) can lead to trophic cascades and other community-level impacts (e.g., Nakano et al 1999;Sato et al 2016). There are certainly many examples of subsidies boosting production at lower trophic levels that contribute to bottom-up increases at higher trophic levels (e.g., Wallace et al 1999;Wipfli et al 1999).…”

“…Additions or removal of sea wrack on small Caribbean islands has shown that this too is a key resource affecting recipient populations (e.g., Piovia-Scott et al 2011). Exclusion of terrestrial arthropods from dropping into a stream resulted in reduced growth and shifts in foraging by trout (Nakano et al 1999), and exclusion of nematomorph-infected crickets from streamsides resulted in much lower growth rates of char compared with control reaches (Sato et al 2011). Exclusion of adult aquatic insects from riparian areas show that many web-building spiders use this resource (Marczak and Richardson 2007).…”

“…Of course, there are many potential higher order consequences at a community level, driven through trophic and indirect interactions. For instance, terrestrial arthropods eaten by stream fishes can lead to trophic cascades as pressure on in situ resources is relaxed (e.g., Nakano et al 1999;Sato et al 2016). Additional prey as a result of sea wrack can reduce predation pressure by island lizards on herbivorous insects leading to indirect effects from a subsidy resource at the shoreline resulting in benefits to plants (Piovia-Scott et al 2011).…”