Topographic disturbance of subaqueous gravel substrates by signal crayfish (Pacifastacus leniusculus)

Johnson, Matthew F.; Rice, Stephen P.; Reid, Ian

doi:10.1016/j.geomorph.2010.07.018

Cited by 37 publications

(68 citation statements)

References 83 publications

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“…These findings therefore support a growing body of research highlighting the detrimental impact of non-native signal crayfish on fluvial geochemistry, fluvial geomorphology and native aquatic biota (Crawford et al 2006;Johnson et al 2010;Harvey et al 2011). Their large size (typically 10-15 cm in length), aggressive nature, high population densities (up to 20 per square metre) and ability to rapidly colonise new environments have seen signal crayfish populations spread rapidly across Europe putting an increasing number of freshwater environments at risk (Holdich et al 2014;Kouba et al 2014).…”

Section: Significance and Further Researchsupporting

confidence: 73%

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

2016

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Purpose A small number of recent studies have linked daily cycles in stream turbidity to nocturnal bioturbation by aquatic fauna, principally crayfish, and demonstrated this process can significantly impact upon water quality under baseflow conditions. Adding to this limited body of research, we use highresolution water quality monitoring data to investigate evidence of diel turbidity cycles in a lowland, headwater stream with a known signal crayfish (Pacifastacus leniusculus) population and explore a range of potential causal mechanisms. Materials and methods Automatic bankside monitoring stations measured turbidity and other water quality parameters at 30-min resolution at three locations on the River Blackwater, Norfolk, UK, during 2013. Specifically, we focused on two 20-day periods of baseflow conditions during January and April 2013 which displayed turbidity trends typical of winter and spring seasons, respectively. The turbidity time-series, which were smoothed with 6.5-h Savitzky-Golay filters to highlight diel trends, were correlated against temperature, stage, dissolved oxygen and pH to assess the importance of abiotic influences on turbidity. Turbidity was also calibrated against suspended particulate matter (SPM) over a wide range of values via linear regression.Results and discussion Pronounced diel turbidity cycles were found at two of the three sites under baseflow conditions during April. Spring night-time turbidity values consistently peaked between 21:00 and 04:00 with values increasing bỹ 10 nephelometric turbidity units (NTU) compared with the lowest recorded daytime values which occurred between 10:00 and 14:00. This translated into statistically significant increases in median midnight SPM concentration of up to 76 % compared with midday, with night-time (18:00-05:30) SPM loads also up to 30 % higher than that recorded during the daytime (06:00-17:30). Relating turbidity to other water quality parameters exhibiting diel cycles revealed there to be neither any correlation that might indicate a causal link nor any obvious mechanistic connections to explain the temporal turbidity trends. Diel turbidity cycles were less prominent at all sites during the winter. Conclusions Considering the seasonality and timing of elevated turbidity, visual observations of crayfish activity and an absence of mechanistic connections with other water quality parameters, the results presented here are consistent with the hypothesis that nocturnal bioturbation is responsible for generating diel turbidity cycles under baseflow conditions in headwater streams. However, further research in a variety of fluvial environments is required to better assess the spatial extent, importance and causal mechanisms of this phenomenon.

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Section: Significance and Further Researchsupporting

confidence: 73%

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

2016

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“…This size distribution is consistent with natural coarse river framework gravels and included particles that Pacifastacus leniusculus are known to displace (up to 38 mm in diameter; Johnson et al. ). The two sections were stacked vertically to provide a total substrate depth of 100 mm.…”

Section: Methodssupporting

confidence: 72%

Predator, prey, and substrate interactions: the role of faunal activity and substrate characteristics

2019

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Many taxa possess a range of strategies to reduce the risk of predation, including actively seeking suitable refuge habitats; however, the global spread of invasive species may disrupt these behavioral responses. In lotic ecosystems, interstitial spaces in the substrate are important refugia for small organisms. Some predators are ecosystem engineers that exhibit zoogeomorphic agency-the ability to modify the geomorphology of their environment. It is therefore possible that direct ecological effects of predators on prey may be realized through modifications to the prey's habitat, including the availability of refugia, by predators that are zoogeomorphic agents or via external stressors such as fine sediment loading. This study examined three research questions in a mesocosm study across a gradient of sediment-stress treatments: (1) What affects do predators (Pacifastacus leniusculus, invasive crayfish) and prey (Gammarus pulex, amphipods) have on the ingress of fine sediment into gravel substrates and therefore on available interstitial refugia? (2) Do prey taxa seek refuge from (invasive) predators in the form of vertical movement into subsurface sediments? and (3) How does fine sediment ingress influence predator-prey interactions and prey survival through predator avoidance behavior. Here, we provide direct evidence demonstrating that fine sediment ingress into gravel river beds can be facilitated by zoogeomorphic activity with P. leniusculus increasing the infiltration of fine sand particles (but not coarse sand) during foraging activities. Predator-prey interactions were found to be a primary factor mediating zoogeomorphic activity, with the isolation of crayfish from prey (G. pulex) leading to increased fine sand ingress. When present with signal crayfish, G. pulex displayed vertical avoidance behavior, entering subsurface substrates to evade predation by P. leniusculus. Coarse sand treatments resulted in higher predation rates of G. pulex, most likely due to clogging of interstitial pore spaces between gravels limiting the effectiveness of the prey's vertical avoidance behavior strategy. A new conceptual model that captures the interactions between predator, prey, zoogeomorphic processes and habitat availability is presented. This model highlights how predator-prey interactions can be strongly mediated by dynamic bi-directional interactions between organisms and the physical environment they inhabit as ecological and geomorphological processes are intrinsically linked.

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“…They burrow into river banks causing collapse where densities are high (Guan, 1994). Experiments by Johnson et al (2010; extended work by Statzner et al (2000Statzner et al ( , 2003 to demonstrate that signal crayfish dismantle the sedimentary structures that provide stability to gravel-bed river substrates, increasing entrainment rates and bedload transport. Some work also suggests that crayfish can affect fine, suspended sediment dynamics.…”

Section: Introductionmentioning

confidence: 94%

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

Rice

Johnson

Extence

et al. 2014

CIG

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Topographic disturbance of subaqueous gravel substrates by signal crayfish (Pacifastacus leniusculus)

Cited by 37 publications

References 83 publications

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

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

Predator, prey, and substrate interactions: the role of faunal activity and substrate characteristics

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

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