Diel patterns of suspended sediment flux and the zoogeomorphic agency of invasive crayfish

Abstract

ABSTRACT. The role of biotic forcing in fluvial geomorphology is understudied. This paper investigates the suggestion that the activities of signal crayfish

Diel turbidity cycles in a headwater stream: evidence of nocturnal bioturbation?

“…These timings are also consistent with the observations of Harvey et al (2014) and Rice et al (2014), who similarly found turbidity peaked at around midnight in the River Windrush, Oxfordshire and River Nene, Northamptonshire, UK, respectively, with both studies linking these cycles to the nocturnal activities of signal crayfish.…”

“…Assuming nocturnal bioturbation is the causal factor of increased SPM concentrations, these night-time SPM loads based on the smoothed turbidity data are~16 % greater at site A and~30 % greater at site E compared to what can be considered the baseline, lower bioturbation, daytime loads. These load estimates are comparable to those obtained by Rice et al (2014) in the headwaters of the River Nene, UK, who calculated an increase in night-time suspended sediment load of 46.9 % compared to daytime load under baseflow conditions. This reduced to a 20.3 % increase in night-time loads when higher-flow flood days were included due to the reduced importance of bioturbation in initiating sediment mobilisation during heavy precipitation events.…”

“…Turbidity measurements, which can be used as a proxy for SPM concentration after calibration, were found to be elevated during the night and lower during the day, a trend attributed to in-stream bioturbation processes. Specifically, it has been demonstrated that the feeding and burrowing activities of nocturnal fish, crayfish and other aquatic organisms stir-up and entrain into suspension fine streambed and channel bank sediments, and it has been suggested that this is responsible for peaks in night-time turbidity measurements (Harvey et al 2011(Harvey et al , 2014Rice et al 2014). There is, therefore, the potential for diel turbidity cycles to occur in other riverine environments similarly inhabited by populations of sediment-mobilising aquatic fauna.…”

Bed disturbance via foraging fish increases bedload transport during subsequent high flows and is controlled by fish size and species

“…With regard to fluvial systems, reviews by Statzner (2011), Rice et al (2012), and Albertson and Allen (2014) highlight the geomorphic capabilities of fish and macroinvertebrate fauna; but the number of studies is small and limited to a few species and impact mechanisms. The majority of research has focused on bed bioturbation during spawning by Salmonids (Field-Dodgson, 1987;Kondolf et al, 1993;Montgomery et al, 1996;Hassan et al, 2008), bed and bank bioturbation by crayfish (Statzner et al, 2003a;Zhang et al, 2004;Johnson et al, 2011;Harvey et al, 2014;Rice et al, 2014) and substrate consolidation through silk secretion by hydropsychid caddisflies (Cardinale et al, 2004;Johnson et al, 2009;. Rice et al (2012, their Figure 19.6) highlight a range of additional mechanisms by which fish and invertebrates might affect bed material conditions and thence sediment transport in gravel-bed rivers.…”

Por qué la geomorfología es una ciencia global

“…This parallels the interrelationships between geomorphology and animals. Rice et al (2014) reported a correlation between the daily activity of an invasive crayfish in British rivers and the pattern of suspended sediment transport, and Borghi et al (1990) demonstrated the important role of micro-mammals in conditioning the soil for erosion in the subalpine belt of the Pyrenees.…”