Chapter 22
Predation in Seagrass Beds
Kenneth L. Heck Jr.
∗
1 Dauphin Island Sea Lab and
2 University of South Alabama, 101 Bienville Boulevard,
Dauphin Island, AL 36528, USA; email: kheck@disl.org
Robert J. Orth
Virginia Institute of Marine Science, School of Marine Science, College of William and Mary
Gloucester Point, VA 23062, USA; email: jjorth@vims.edu
I. Introduction
The ability of leaves, roots, and rhizomes to reduce
the rate of predation on associated animals is as
well studied as any topic having to do with seagrass
beds, and is one of the major tenets of the seagrass
‘nursery role hypothesis’ (Beck et al., 2001). The
past two decades have each produced detailed reviews of the effects of seagrasses on the outcome
of predator–prey interactions (e.g. Heck and Orth,
1980; Orth et al., 1984; Heck and Crowder, 1991;
Orth, 1992; Bartholomew et al., 2000; Hemminga
and Duarte, 2000; Williams and Heck, 2001). In addition, Duffy and Hay (2001) have written a comprehensive overview of consumer–prey relationships in
marine environments. Although the major conclusions of these reviews, that seagrass leaves, roots,
and rhizomes reduce the rate of predation on both
mobile and sessile animals, whether they are infaunal or epifaunal, have remained unchallenged, new
issues have been raised. In this chapter, we first summarize the previous generalizations that continue to
be supported by recent work, and then focus attention on results that challenge the conventional wisdom on predator–prey interactions in seagrass meadows. Throughout, we provide suggestions for studies
that seem to be capable of resolving controversies or
breaking new ground.
∗ Author for correspondence: Kenneth L. Heck Jr. email:
kheck@disl.org
Virginia Institute of Marine Science Contribution Number 2655;
Dauphin. Island Sea Lab Contribution Number 362.
II. Effects of Seagrasses on Predator–Prey
Interactions in Ecological Time
By far, the greatest attention has been focused on
how seagrass biomass, surface area, and physical
structure (principally estimated by shoot density)
influence the outcome of predator–prey interactions
among epifaunal macro-organisms. All this work has
been concerned with events occurring on ecological
time scales, that is, lasting from a few hours to a few
generations for the predators and prey being studied. Motile, macro-epifauna (e.g. amphipods, crabs,
shrimps) have been emphasized in these studies because they are the most conspicuous components
within the seagrass canopy and because it is easier
to study epifaunal macrofauna than epifaunal microor meiofauna, or infauna of any size. Also, a few of
these species are commercially valuable and funding has been available for elucidating the factors
that determine their survival, e.g. blue crabs, spotted
seatrout, prawns, lobsters (see Heck et al., 2003). As
intuition and observations suggested to earlier investigators, and a recent meta-analysis of experimental
data has confirmed, the presence of seagrass shoots
significantly reduces the effectiveness of fish predation on a variety of epifaunal invertebrate and fish
taxa, relative to their success on unvegetated substrates (Orth et al., 1984; Heck and Crowder, 1991;
Heck et al., 2003).
What is perhaps more interesting, and challenging, is to untangle the interconnected roles that seagrass species’ morphologies, biomass, surface areas, structural complexity, habitat patchiness, and
537–550.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp.
c
2006 Springer. Printed in the Netherlands.
Predation in Seagrass Beds
Kenneth L. Heck Jr.
∗
1 Dauphin Island Sea Lab and
2 University of South Alabama, 101 Bienville Boulevard,
Dauphin Island, AL 36528, USA; email: kheck@disl.org
Robert J. Orth
Virginia Institute of Marine Science, School of Marine Science, College of William and Mary
Gloucester Point, VA 23062, USA; email: jjorth@vims.edu
I. Introduction
The ability of leaves, roots, and rhizomes to reduce
the rate of predation on associated animals is as
well studied as any topic having to do with seagrass
beds, and is one of the major tenets of the seagrass
‘nursery role hypothesis’ (Beck et al., 2001). The
past two decades have each produced detailed reviews of the effects of seagrasses on the outcome
of predator–prey interactions (e.g. Heck and Orth,
1980; Orth et al., 1984; Heck and Crowder, 1991;
Orth, 1992; Bartholomew et al., 2000; Hemminga
and Duarte, 2000; Williams and Heck, 2001). In addition, Duffy and Hay (2001) have written a comprehensive overview of consumer–prey relationships in
marine environments. Although the major conclusions of these reviews, that seagrass leaves, roots,
and rhizomes reduce the rate of predation on both
mobile and sessile animals, whether they are infaunal or epifaunal, have remained unchallenged, new
issues have been raised. In this chapter, we first summarize the previous generalizations that continue to
be supported by recent work, and then focus attention on results that challenge the conventional wisdom on predator–prey interactions in seagrass meadows. Throughout, we provide suggestions for studies
that seem to be capable of resolving controversies or
breaking new ground.
∗ Author for correspondence: Kenneth L. Heck Jr. email:
kheck@disl.org
Virginia Institute of Marine Science Contribution Number 2655;
Dauphin. Island Sea Lab Contribution Number 362.
II. Effects of Seagrasses on Predator–Prey
Interactions in Ecological Time
By far, the greatest attention has been focused on
how seagrass biomass, surface area, and physical
structure (principally estimated by shoot density)
influence the outcome of predator–prey interactions
among epifaunal macro-organisms. All this work has
been concerned with events occurring on ecological
time scales, that is, lasting from a few hours to a few
generations for the predators and prey being studied. Motile, macro-epifauna (e.g. amphipods, crabs,
shrimps) have been emphasized in these studies because they are the most conspicuous components
within the seagrass canopy and because it is easier
to study epifaunal macrofauna than epifaunal microor meiofauna, or infauna of any size. Also, a few of
these species are commercially valuable and funding has been available for elucidating the factors
that determine their survival, e.g. blue crabs, spotted
seatrout, prawns, lobsters (see Heck et al., 2003). As
intuition and observations suggested to earlier investigators, and a recent meta-analysis of experimental
data has confirmed, the presence of seagrass shoots
significantly reduces the effectiveness of fish predation on a variety of epifaunal invertebrate and fish
taxa, relative to their success on unvegetated substrates (Orth et al., 1984; Heck and Crowder, 1991;
Heck et al., 2003).
What is perhaps more interesting, and challenging, is to untangle the interconnected roles that seagrass species’ morphologies, biomass, surface areas, structural complexity, habitat patchiness, and
537–550.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp.
c
2006 Springer. Printed in the Netherlands.