The fate of marine-derived nutrients: tracing δ¹³C and δ¹⁵N through oligotrophic freshwater and linked riparian ecosystems following salmon carcass analog additions

Abstract

The oligotrophic condition of salmon-bearing catchments in the Columbia River Basin is a potential limiting factor for the recovery of Pacific salmon (Oncorhynchus spp.). To address this issue, nutrient supplementation programs attempt to mitigate for reduced marine-derived nutrients (MDN). We examined the assimilation of MDN in the biota of tributaries of the Salmon River Basin, Idaho, USA, following the addition of salmon carcass analogs (SCA). We measured carbon (C) and nitrogen (N) stable isotopes from biofilm, macroinvertebrate, salmonid fish, and riparian vegetation samples and found significant 15N enrichment and substantial assimilation of SCA material in all aquatic trophic levels and in riparian vegetation. Our results suggest that SCA are incorporated primarily through indirect pathways and provide a source of MDN to multiple trophic levels in freshwater and linked riparian ecosystems.

Predicting the contributions of novel marine prey resources from angling and anadromy to the diet of a freshwater apex predator

“…Its presence was also consistent with a large body of research that demonstrates the importance of anadromous fishes for maintaining the productivity, diversity, and community structure of many freshwater systems (Richardson et al, 2016;Schindler et al, 2005). This anadromous prey resource was, however, still an important dietary component.…”

“…In freshwater ecosystems, the transfer of nutrients from allochthonous resource subsidies can play a primary role in food-web structuring (Samways, Soto, & Cunjak, 2018;Takimoto, Iwata, & Murakami, 2002). The benefits to freshwater nutrient budgets via marine-derived nutrient (MDN) transfer from anadromous salmonid fishes (via excretion, gamete release and carcass decomposition) have been well established (Richardson, Kohler, Hailemichael, & Finney, 2016;Schindler, Leavitt, Brock, Johnson, & Quay, 2005;Wipfli, Hudson, Caouette, & Chaloner, 2003;Zhang, Negishi, Richardson, & Kolodziejczyk, 2003). However, anadromous fishes can also play an important role in the transfer of MDN to freshwaters via their direct consumption by freshwater apex predators (Guillerault, Bouletreau, Iribar, Valentini, & Santoul, 2017;MacAvoy, Macko, McIninch, & Garman, 2000).…”

Trophic consequences for riverine cyprinid fishes of angler subsidies based on marine‐derived nutrients

“…This is in contrast with the transfer of MDN into fresh waters via migratory salmonid fishes, where the nutrients are more freely available and facilitate the increased production of benthic algae and macroinvertebrates (Schindler et al, 2003). This then enhances the food resources available for the larvae and juveniles of the adult migrants, facilitating their feeding, growth and survival in the early life stages (Wipfli, Hudson, Caouette, & Chaloner, 2003 Hobson, 2016;Richardson et al, 2016), with its influence even affecting the behaviour of terrestrial predator and scavenger species (Schindler et al, 2013).…”

“…Following reproduction and death of these fishes, their MDN could be traced through the macroinvertebrate community and then into a bird that preys upon these, the American dipper Cinclus mexicanus . Indeed, there are now numerous studies that have traced MDN into terrestrial food webs (e.g., McLoughlin, Lysak, Debeffe, Perry, & Hobson, ; Richardson et al., ), with its influence even affecting the behaviour of terrestrial predator and scavenger species (Schindler et al., ).…”

“…Trophic fluxes of energy and nutrient resources can be ecologically significant when they cross the boundaries of ecosystems that differ in their productivity (e.g., Polis & Hurd, 1995;Richardson, Kohler, Hailemichael & Finney, 2016;Zhang, Negishi, Richardson & Kolodziejczyk, 2003). These cross-system fluxes can maintain the productivity, diversity and community structure of recipient ecosystems (Schindler, Leavitt, Brock, Johnson & Quay, 2005).…”