Marine Research Findings of the VECTORS Project

This website provides access to the research results of the VECTORS project, which can be used to support marine management decisions, policies and governance as well as future research and investment. VECTORS was a large scale project that brought together more than 200 expert researchers from 16 different countries. It examined the significant changes taking place in European seas, their causes, and the impacts they will have on society.

Impact of the non-indigenous Chinese mitten crab (Eriocheir sinensis) on sedimentary ecosystems

Eriocheir sinensis (Chinese mitten crab) is an aggressive invader spreading around the UK coast and is on the IUCN list of the 100 most damaging invasive species in the UK and was also included in the handbook of the most invasive alien species in Europe. The mitten crab is known for its burrowing activity. Organisms which modify their physical environment and regulate the availability of resources for other species through burrowing activities and bioturbation are recognised as ecosystem engineers. Bioturbators can have significant influences on ecosystem processes which can vary depending on a range of factors. Targeted experiments were carried out to (a) examine the influence of the crabs at different densities on ecosystem functioning (sediment destabilisation, sediment erosion) in synthetic assemblages to reveal the effect on the ecosystem as the invader becomes established and (b) to test how bioturbatory activity varies with temperature and size of the crabs.

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There was a significant reduction in sediment stability (expressed as equivalent horizontal shear stress1, Nm-2) of all Chinese mitten crab density treatments when compared to controls. Invaded habitats therefore have reduced resistance to sediment erosion.

Using a cohesive strength meter (CSM)2 VECTORS researchers examined sediment stability in experimental mesocosm under varying densities of mitten crabs. The erosion threshold (psi) was established for each mesocosm by exposing the sediment to erosive water jets of gradually increasing pressure. The pressure at which sediment erodes is then expressed as an equivalent horizontal shear stress1. There was a significant reduction in sediment stability of all crab treatments when compared to controls for both males and females. Reduced sediment stability will destabilise affected depositional habitats resulting in increased erosion and therefore changes in the ecology and dynamics, as well as the services provided by these ecosystems.

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There was no significant difference in the bioturbation depth profiles between the two size classes and three temperature treatments, which suggests both sizes of mitten crabs were equally active across the temperatures examined.

VECTORS researchers used a mesocosm approach to quantify the contributions that individual Chinese mitten crabs make to the bioturbation of surface sediments. As body size is known to be a strong determinant of a species bioturbation potential and infaunal activity is affected by temperature, two size classes were investigated across three temperature levels (10°C, 15°C and 19°C) that reflect the range experienced at the study site across the annual cycle. Faunal mediated sediment particle reworking was estimated non-invasively using a sediment profile imaging camera, optically modified to allow preferential imaging of fluorescently labelled sand-based particulate tracers under UV light (f-SPI)3. Overall, vertical particle redistribution revealed a slightly non-significant effect of size class, but we found no evidence for the effects of “Temperature” or the interactive effects of “size class and temperature” for any of our response variables. This has implications for increased turbidity, nutrient release from sediments and potentially increased siltation of gravel beds, including fish spawning grounds.

Relevance for Policy:
  • Alien Invasive Species Directive
  • Habitats and Birds Directive
  • Marine Strategy Framework Directive
  • Water Framework Directive
Further information:

Deliverable 3.1.3: Novel experimental evidence for impacts of biodiversity on ecosystem functioning

Bioturbation in action – time-lapse video of the Chinese mitten crab reworking its sediment habitat. Side view of an experimental mesocosm with a luminophore (fluorescent sand) layer over a sediment substratum. The Chinese mitten crab was introduced to the mesocosm and its activity was recorded over a 48 hour period.


References

Lead Author:

Andrew Blight and David Paterson & Andrew Blight
(dp1@st-nospamandrews.ac.uk)
USTAN
Date of research: November 2014

Related articles:

Invasive ecosystem engineers and biodiversity

Ecosystem impacts of non-indigenous species

Impact of invasive mussels on carbon flow 

Invasive species and ballast waters mitigation 

Non-indigenous and invasive alien species

Alien Species database 

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 266445
© Vectors 2015. Coordinated by Plymouth Marine Laboratory.