Vectors with autonomy: what distinguishes animal‐mediated nutrient transport from abiotic vectors?

Abstract

Animal movements are important drivers of nutrient redistribution that can affect primary productivity and biodiversity across various spatial scales. Recent work indicates that incorporating these movements into ecosystem models can enhance our ability to predict the spatio‐temporal distribution of nutrients. However, the role of animal behaviour in animal‐mediated nutrient transport (i.e. active subsidies) remains under‐explored. Here we review the current literature on active subsidies to show how the behaviour of active subsidy agents makes them both ecologically important and qualitatively distinct from abiotic processes (i.e. passive subsidies). We first propose that animal movement patterns can create similar ecological effects (i.e. press and pulse disturbances) in recipient ecosystems, which can be equal in magnitude to or greater than those of passive subsidies. We then highlight three key behavioural features distinguishing active subsidies. First, organisms can transport nutrients counter‐directionally to abiotic forces and potential energy gradients (e.g. upstream). Second, unlike passive subsidies, organisms respond to the patterns of nutrients that they generate. Third, animal agents interact with each other. The latter two features can form positive‐ or negative‐feedback loops, creating patterns in space or time that can reinforce nutrient hotspots in places of mass aggregations and/or create lasting impacts within ecosystems. Because human‐driven changes can affect both the space‐use of active subsidy species and their composition at both population (i.e. individual variation) and community levels (i.e. species interactions), predicting patterns in nutrient flows under future modified environmental conditions depends on understanding the behavioural mechanisms that underlie active subsidies and variation among agents' contributions. We conclude by advocating for the integration of animal behaviour, animal movement data, and individual variation into future conservation efforts in order to provide more accurate and realistic assessments of changing ecosystem function.

Filling the Information Gap in Meta-Ecosystem Ecology

“…Information also mediates microbial contributions to ecosystem dynamics, for example, by catalyzing the formation of (Hall-Stoodley et al 2004) and dispersal from (McDougald et al 2012) biofilms, which alter how bacteria and other microorganisms contribute to carbon and nutrient cycling. These ecosystem effects can form feedback loops as altered information elicits further behavioral, life history, or dispersal responses (Earl & Zollner 2017;McInturf et al 2019).…”

“…Disentangling the mechanisms and impacts of agent-mediated information transfer will be an essential step towards integrating information into the metaecosystem framework. Indeed, the current rising interest in developing meta-ecosystem models accounting for agent-based transfers of nutrients and energy across ecosystems (Gounand et al 2018a;Subalusky & Post 2018;Guzman et al 2019;McInturf et al 2019) offers a unique opportunity to include information as a third currency in ecological interactions. Furthermore, these models could consider how the spatial arrangement of and relationships between ecosystems (Box 3), and reduced animal movement driven by habitat loss and fragmentation (Tucker et al 2018), affect the flow of information between ecosystems.…”

Landscapes shaped from the top down: predicting cascading predator effects on spatial biogeochemistry

“…Animals may roam and interact widely across landscapes, all the while consuming and redistributing nutrients via egestion, excretion, and carcass deposition (Bauer and Hoye 2014, Schmitz et al 2018, Subalusky and Post 2018, McInturf et al 2019, Pausas and Bond 2020.…”

Individual consumer movement mediates food web coupling across a coastal ecosystem

“…Understanding the role of animals in the transfer of trophic subsidies across coastal seascapes requires information on the patterns of faunal space use over time (Pittman 2018). Consumer‐mediated nutrient subsidies differ from physically mediated nutrient subsidies (e.g., current, wind) in that they can transport nutrients counter to abiotic gradients, respond to self‐generated patterns of nutrient distribution, and be modified by interactions with other consumers (McInturf et al 2019). These features can generate feedback loops and form patterns in the distribution of nutrients across seascapes that influence ecological function (McInturf et al 2019).…”

“…Consumer‐mediated nutrient subsidies differ from physically mediated nutrient subsidies (e.g., current, wind) in that they can transport nutrients counter to abiotic gradients, respond to self‐generated patterns of nutrient distribution, and be modified by interactions with other consumers (McInturf et al 2019). These features can generate feedback loops and form patterns in the distribution of nutrients across seascapes that influence ecological function (McInturf et al 2019). The movement and foraging patterns that mediate food web coupling can vary widely within species due to the diverse array of behavioral traits that underlie intraspecific differences within populations (e.g., personality‐dependent dispersal; Cote et al 2010).…”