Causes and consequences of invertebrate drift in running waters: from individuals to populations and trophic fluxes

Abstract

Invertebrate drift, the downstream transport of aquatic invertebrates, is a fundamental ecological process in streams with important management implications for drift-feeding fishes. Despite long-standing interest, many aspects of drift remain poorly understood mechanistically, thereby limiting broader food web applications (e.g., bioenergetics-based habitat models for fish). Here, we review and synthesize drift-related processes, focusing on their underlying causes, consequences for invertebrate populations and broader trophic dynamics, and recent advances in predictive modelling of drift. Improving predictive models requires further resolving the environmental contexts where drift is driven by hydraulics (passive drift) versus behaviour (active drift). We posit this can be qualitatively inferred by hydraulic conditions, diurnal periodicity, and taxa-specific traits. For invertebrate populations, while the paradox of population persistence in the context of downstream loss has been generally resolved with theory, there are still many unanswered questions surrounding the consequences of drift for population dynamics. In a food web context, there is a need to better understand drift-foraging consumer-resource dynamics and to improve modelling of drift fluxes to more realistically assess habitat capacity for drift-feeding fishes.Résumé : La dérive d'invertébrés, soit le transport vers l'aval d'invertébrés aquatiques, est un processus écologique fondamental dans les cours d'eau qui a d'importantes conséquences pour les poissons qui se nourrissent d'aliments à la dérive. Malgré un intérêt de longue date, de nombreux aspects de la dérive demeurent mal compris d'un point de vue mécaniste, ce qui limite les applications plus larges des réseaux trophiques (p. ex. les modèles d'habitat reposant sur la bioénergétique pour les poissons). Nous passons en revue et résumons les processus associés à la dérive, en mettant l'accent sur leurs causes sous-jacentes, les conséquences pour les populations d'invertébrés et la dynamique trophique plus large, ainsi que les avancées récentes en modélisation prédictive de la dérive. L'amélioration des modèles prédictifs nécessite une meilleure résolution des milieux dans lesquels la dérive est mue, d'une part, par l'hydraulique (dérive passive) ou, d'autre part, par le comportement (dérive active). Nous postulons que cela peut être inféré de manière qualitative à partir des conditions hydrauliques, de la périodicité diurne et de caractères propres aux taxons. Pour les populations d'invertébrés, si le paradoxe de la persistance des populations dans le contexte de perte en aval a généralement été résolu en faisant appel à la théorie, de nombreuses questions demeurent quant aux conséquences de la dérive pour la dynamique des populations. Dans un contexte de réseaux trophiques, il est nécessaire de mieux comprendre la dynamique dérive-consommateur s'alimentant-ressource et d'améliorer la modélisation des flux de dérive pour évaluer de manière plus réaliste la capacité des habitats p...

Three‐dimensional tracking of the motion of benthic copepods in the free water and inside the transparent sediment bed of a laboratory flume

“…For instance, it will be possible to study the fine‐scale displacement of copepods between streambed patches of different flow velocity, to quantify their activity in response to thermal variations and increase in shear stress, and to investigate the role of self‐induced motion on drift entry, drifting distance, and settlement process. Multiple lines of evidence indicate a substantial role of behavior in the ecology of benthic organisms and in the processes generating or terminating drift (Malmqvist ; Naman et al ). Our setup enables the detailed observation of behavioral processes that could not be approached in field studies due to logistic constraints, and provides opportunities for taxon‐specific mechanistic studies, with useful ecological applications such as more realistic models of drift flux.…”

Extrinsic Factors Influencing Somatic Growth of Lake Sturgeon

“…The quantity of macroinvertebrates drifting in running waters is known to vary on a seasonal basis, a consequence of passive (i.e., flow‐mediated) and active (i.e., behavioral) release of individuals from the substrate (see review by Naman et al. ). For example, on the middle Nelson River (Gull and Stephens lakes), the quantity of organisms captured in bottom‐set drift traps was ~50% greater during July and August relative to late September (Gill , ).…”

Environmental constraints structuring fish assemblages in riffles: evidences from a tropical stream

“…The differential availability of food resources among riffles must be one of the explanations for the distribution of species according to their trophic group. The high water flow velocity should contribute to the carrying of drift items such as detritus, plant material, terrestrial, and aquatic insects out of the riffles (Naman et al, 2016), while food items that are adhered in rigid substrates, such as periphyton tend to persist. On the other hand, the less restrictive influence of flow in deeper riffles should favor the occurrence of pelagic drift feeders (Casatti & Castro, 1998), such as Knodus cf.…”