As significant biotic components of aquatic and
terrestrial ecosystems, soil animals are multipurpose
workers, for example, consumers, litter
decomposers, and habitat modifiers, which passively
and/or actively disturb the substrate.
Bioturbation is defined as biological reworking of
soils and sediments through animal activities like
Received 22 November 2009; accepted 6 May 2010;
published online 2 June 2010
Electronic supplementary material: The online version of this article
(doi:10.1007/s10021-010-9342-5) contains supplementary material,
which is available to authorized users.
Author Contributions: J. Q. Wang and X. D. Zhang are equal contributors.
Conceived of study: JQW, CMF, JKC, TH, BL; performed
research: JQW, XDZ, LFJ; analyzed data: JQW, XDZ; wrote the paper:
JQW, XDZ, MDB, BL
*Corresponding author; e-mail:
[email protected]Ecosystems (2010) 13: 586–599
DOI: 10.1007/s10021-010-9342-5
2010 Springer Science+Business Media, LLC
586
burrowing and feeding (Meysman and others
2006). Animal bioturbation and its ecological roles
in shaping soil ecosystem processes were first
appreciated by Darwin (1881) and were described
in great detail in his last book On the Formation of
Vegetable Mounds through the Action of Worms with
Observations on their Habits. Invertebrate feeding on
resources in the sediments evidently affects key
processes, such as organic carbon mineralization
(Otani and others 2010), nutrient dynamics
(Karlson and others 2007; McHenga and Tsuchiya
2008), sulfur and iron cycling (Gribsholt and others
2003; Nielsen and others 2003), sediment texture
modification and particle mixing (Paarlberg and
others 2005). The altered soil characteristics might
further impact microbial activities (Bertics and
Ziebis 2009), zooplankton recruitment (Gyllstro¨m
and others 2008) and other biotic components
(Reinsel 2004; Canepuccia and others 2008), or the
spatial heterogeneity might generate niches for
smaller organisms (van Nugteren and others 2009).
Furthermore, long term functions of bioturbation
play important roles in digenetic reaction, and
facilitate the development of pristine ecosystems
(Herringshaw and Solan 2008). One type of dominant
bioturbations in coastal ecosystems is crab
burrowing which can transport sediments and
modify sediment texture, accelerating ecosystem
nutrient cycling.
Salt marshes in coastal wetlands are one of the
most productive natural ecosystems (Mitsch and
Gosselink 1993) and provide considerable ecosystem
services for human society (Costanza and
others 1997). The decomposition and transformation
of primary products from salt marshes provide
nutrients for the growth of marsh plants and for
export to adjacent ecosystems, subsidizing oceanic
productivity (Odum 1980). Sediment biogeochemical
processes play important roles in the
metabolism and nutrient cycling of salt marshes
(Webb and Eyre 2004).
Burrowing sesarmid (Grapsidae) and fiddler
crabs (Ocypodidae) are the most important
macroinvertebrates in many salt marshes (Emmerson
1994; Montague 1982). They are often
present in large numbers; and their burrowing
activities can directly break and transport sediments,
decrease the hardness of the soil (Bortolus
and Iribarne 1999; Botto and Iribarne 2000; Botto
and others 2005), modify microtopography, and
increase the density of coarse particles on the
soil surface (Warren and Underwood 1986).
Crab burrowing also affects soil chemistry and
associated microbial processes, increases soil oxygenation,
and alters pore water salinity (Fanjul
and others 2007). Burrowing crabs significantly
affect belowground processes that can impact
marsh plants (Bertness 1985; Iribarne and others
1997; Bortolus and Iribarne 1999; Smith and
others 2009) in at least three ways. First, crab
burrowing increases the passage of liquid and gas
between the soil and environment (that is, increase
drainage), increasing soil oxidation (Katz
1980; Daleo and Iribarne 2009; Weissberger and
others 2009) and the decomposition rate of organic
debris (Lee 1998; Reinsel 2004; Fanjul and
others 2007). Second, crab burrows can selectively
trap sediments that have high organic
matter concentrations, finer grain size and low
density through the interactions of the burrow
opening with tidal water, which can facilitate
organic matter decomposition, which can in turn
increase nutrient availability and thus, promote
their growth (Iribarne and others 1997, 2000;
Botto and others 2006). Third, crab excavation
transports soil and nutrients from deep layers to
the marsh surface (Fanjul and others 2007, 2008),
which might accelerate the turnover of soil and
nutrients. Soil properties and plant assemblage
characteristics influenced by crab excavation and
burrow deposition can in turn affect burrowing
processes (Neira and others 2006). Few attempts,
however, have been made to examine these
processes (but see Botto and Iribarne 2000; Gutierrez
and others 2006), and the interactive effects
of plant communities and crab burrowing remain