The shrimp Crangon crangon is a significant predator of the smallest sizes of
plaice during and immediately after the fish settle on sandy beaches. Predation rate is
strongly dependent on the size of both the predator and the prey (Gibson, Yin & Robb
1995). Polychaete worms are dominant predators within the substratum and tend to be
opportunistic and actively pursue prey (although they may have size preferences); their
numbers may be closely related to those of their prey, which includes other worms and
crustaceans (Meire et al. 1994). Many infaunal species also scavenge e.g. Nephtys
and the isopod Eurydice pulchra and quantity of food available determines the
density of scavengers (Hayward 1994; Ansell et al. 1972).
The presence of high densities of adult invertebrates in the sand may inhibit the
recruitment of potential colonising stages from the water column (Olafsson, Peterson &
Ambrose 1994). This may account for juveniles occupying less favourable parts of the
intertidal areas, for example juvenile Arenicola and Nephtys settle in areas
outside the optimal distribution for the adults (usually higher on the shore).
Sandflat communities tend to be relatively poor in species but may have very high
abundances of those species which are present.
Keystone (structuring) species
Importance of habitat for other species
Intertidal areas are well defined as juvenile fish-feeding areas (Costa & Elliott
1991). Sheltered sandflats are important nursery areas for plaice (Lockwood 1972; Marshall
1995; Marshall & Elliott 1997), as well as feeding areas for sea bass Dicentrarchus
labrax and flounder Platichthys flesus (Elliott & Taylor 1989). Fish such
as sole Solea solea and gadoids frequent sandy areas, but many also occur on
coarser and mixed grades of sediment. The most important marine predators on intertidal
sandflats are the sole Solea solea, dab Limanda limanda, flounder Platichthys
flesus and plaice Pleuronectes platessa plaice which feed on polychaetes (for
example Arenicola and Nereis) and tidally active crustaceans such as Bathyporeia
and Eurydice species (Croker & Hatfield 1980; McDermott 1983; McLachlan
1983). In summer, large numbers of juvenile plaice and dab move over flats at high tide to
feed on mobile epifauna, sedentary infauna and protruding siphons and tentacles (Elliott
& Taylor 1989). On sandflats many demersal fish are opportunistic predators and the
prey choice will reflect the infaunal species distribution of the area (Costa &
Elliott 1991). Migratory species of fish such as salmon and shad can be found on sandflats
when on passage to other wetlands e.g. saltmarshes and freshwater areas, although they
appear to have no particular requirement for the sandflats.
The littoral gravel and sand biotopes are also used by important wintering and passage
birds for feeding. Shorebirds are important predators on north-west European intertidal
sandflats during long migrations from breeding to wintering grounds. Intertidal sandflats
also support microphytobenthos in the interstices between the sand grains. Mucilagenous
secretions produced by these algae may stabilise fine substrata (Tait & Dipper 1998).
Macrophytes are usually sparse on intertidal sand unless there are some stones or shells
for the attachment of species. The community may include mats of Enteromorpha spp.
and Ulva spp., possibly in large aggregates to form the so-called
green tides (Piriou, Menesguen & Salomon 1991).
No information available.
Time for community to reach maturity
No information available.