|Basic Information||Biotope classification||Ecology||Habitat preferences and distribution||Species composition||Sensitivity||Importance|
Image Harvey Tyler-Walters - Edge of a Phragmites reed bed in February, Tamar Estuary. Image width ca 1 m in foreground.
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SS.IMU.Ang.S4 recorded () and expected () distribution in Britain and Ireland (see below)
The terrestrial animal and plant communities of Phragmites reed beds have been well studied (Haslam, 1972; Ranwell, 1972; Haslam, 1978; Fuller, 1982; Cowie et al., 1992; Ditlhogo et al., 1992; Fojt & Foster, 1992; Ward, 1992; Rodwell, 1995; Hawke & José, 1996), while the aquatic community, especially invertebrates, has been less well studied (Arnold & Ormerod, 1997) and the benthic infauna are poorly known (Connor et al. 1997a). In the information that follows inferences concerning ecological relationships have been made from other aquatic communities (see £IMU.NVC_A12£ or £IMS.Rup£) where appropriate. Phragmites australis forms extensive perennial systems of rhizomes that bind, oxygenate and stabilize the sediment.
The rhizomes, litter and upright stems of Phragmites australis provide a substratum for a wide variety of microalgae, macroalgae, aquatic invertebrates, terrestrial invertebrates and amphibians, and substratum and nesting material for some birds (e.g. the reed warbler Acrocephalus scirpaceus and the bittern Botaurus stellaris) and the harvest mouse (Micromys minutus).
Phragmites australis and other aquatic macrophytes or helophytes (e.g. the common marsh bedstraw Galium palustre, bogbean Menyanthes trifoliata, and the spear-leaved orache Atriplex prostrata) provide primary productivity within the biotope and are fed on by numerous phytophagous insects.
Phragmites australis is fed on directly by numerous species of Lepidoptera (butterflies and moths), Diptera (flies), Hymenoptera (bees and wasps), Coleoptera (beetles), Homoptera (true bugs and aphids), and Acari (mites). Notable examples include, the large wainscot Rhizedra lutosa, the twin-spotted wainscot Archanara geminipunctata, Fenn's wainscot Photedes brevilinea, the reed leopard moth Phragmataecia castaneae, the gall forming midge Giraudiella inclusa, gall-forming flies e.g. Lipura spp., and aphids such as Hyalopterus pruni (for details see Haslam, 1972; Ditlhogo et al., 1992; Tscharntke, 1992, 1999; Fojt & Foster, 1992; Hawke & José, 1996; Drake, 1998).
Short, young shoots or rhizomes of Phragmites australis may be grazed by sheep, deer, water voles, some species of wild birds (e.g. Canada or grey lag geese) (Haslam, 1972, Hawke & José,1992; Rodwell, 1995).
Additional primary productivity is provided by benthic microalgae (Wainright et al., 2000), microalgal (e.g. blue-green algae and diatoms) periphyton and epiphytes growing on the stems of Phragmites australis (Müller, 1999), a mat of filamentous algae (e.g. Ulva prolifera and Cladophora spp.) in more saline situations and, when present, stoneworts (e.g. Chara aspera and Lamprothamnium papulosum) (Connor et al., 1997a).
Decomposition of leaves and stems, especially in autumn and winter, support a detrital food chain within the biotope and probably also provide primary productivity to deeper water and the strandline. Wainright et al. (2000) suggested that Phragmites australis contributed secondary productivity to aquatic food webs in tidal marshes (see productivity below).
The most important role in the food chain for isopods (e.g. the water louse Asellus aquaticus, the isopod Sphaeroma rugicauda and the wood louse Philoscia vittata) and gammarids (e.g. Orchestia spp., Gammarus zaddachi and Gammarus duebeni) is the break down of decomposing leaves, stems and other plant material into fine particles of detritus suitable for suspension and deposit feeders and microbes in the detrital food chain (Hawke & José, 1996; Arnold & Ormerod, 1997; Fell et al., 1998). Other decomposers include midge larvae, nematodes, oligochaetes (e.g. Heterochaeta costata) and Collembella (spring tails).
The periphyton, epiphytes and algal mats may be grazed by gastropods (e.g. Hydrobia ulvae and Potamopyrgus spp.), amphipods (e.g. Gammarus salinus and other Gammarus species), isopods (probably Jaera spp., and Idotea spp.), probably mysids (Mauchline, 1980), and tadpoles where present.
Suspension feeders filter both phytoplankton and detritus (organic particulates), for example amphipods (e.g. Corophium volutator), the mysids, the epiphytic bryozoan Conopeum seurati where present (see Bamber et al., 2001), and some polychaetes (e.g. Hediste diversicolor).
Surface and infaunal deposit feeders probably include oligochaetes (e.g. Heterochaeta costata), amphipods (e.g. Corophium volutator), and chironomid larvae.
Small aquatic invertebrates and fish fry or larvae are probably preyed on by small mobile predators such as dragonfly larvae, water boatmen (e.g. Sigara spp.), mysids, shrimp (e.g. Crangon crangon), and small fish such as sticklebacks e.g. Gasterosteus aculeatus).
The larva of the silky wainscot Chilodes maritimus preys on the pupae of other reed moths.
Other fish such as the gobies and the eel Anguilla anguilla are generalist predators.
Mysids, shrimp (e.g. Crangon crangon or Palaemonetes varians) and crabs probably act a scavengers within the biotope.
The terrestrial and aquatic macroinvertebrate population probably supports a variety of fish species, which enter the habitat from shallow water or with the tide, and a variety of bird species from the surrounding area.
Small fish such as sticklebacks, minnow, fish fry, together with frogs may be important food sources for the bittern or grey heron (Hawke & José, 1996).
Terrestrial insects are probably food sources for frogs, birds and small mammals, both within the reed bed and the surrounding area. For example, chironomids (midges) are an important food source for warblers and bearded tit (Panurus biarmicus), while aphids are an important food for migratory warblers, e.g. the sedge warbler Acrocephalus schoenobaenus. Water voles and water shrews are common on ditches and the harvest mouse may reach high numbers in reed beds feeding on insects in summer and seed (including Phragmites seed) in winter (Hawke & José, 1996).
Where present the otter (Lutra lutra) may feed on frogs and fish, while the grass snake (Natrix natrix) feeds primarily on frogs (Hawke & José, 1996).
In saline and brackish conditions Phragmites australis competes with other halophytic plants e.g. cord grasses Spartina spp. at its seaward limit, where conditions favour Spartina species (Ranwell, 1972). In drier areas of marsh Phragmites may be out-competed by bulrush Typha latifolia, the common club rush Schoenoplectus lacustris, Buck's horn plantain Plantago coronopus or the slender sedge Carex lasiocarpa (Haslam, 1972). However, in areas of habitat disturbance, where for example Spartina spp. is removed, Phragmites may invade the habitat (Amsberry et al., 2000). Once established, Phragmites australis is tall and a dominant competitor for light, so that dense stands of the common reed tend to be species poor in other plant species (Haslam, 1972; Rodwell, 1995; Bertness et al., 2002). But Phragmites itself may be suppressed by shading (Haslam, 1972), presumably by shrub and trees (e.g. alder or willow carr) at the inland edge of the shore.
Phragmites australis first flowers after 3-4 years in moderately good conditions and individual rhizomes live for only 3-6 years, dying from behind (Haslam, 1972). However, the Phragmites community can be very long-lived if not disturbed, and vegetative clones of Phragmites australis can be up to 1000 years old (Rudescu et al., 1965 cited in Rodwell, 1995).Growth of filamentous algae and algal mats is greatest in the summer months. The aquatic and terrestrial invertebrate populations probably vary seasonally, peaking in numbers during spring and summer when the aerial shoots are growing. Some species over-winter as pupae in the dead stems of the common reed e.g. the reed leopard moth Phragmataecia castaneae, while others probably use the reed as an attachment for their pupae. Gall forming midges over-winter in the galls formed on Phragmites (Tscharntke, 1992), emerging to infest summer shoots of the reed.
The aquatic invertebrates of Phragmites reed beds may show similar seasonal change to those reported in Potamogeton and Myriophyllum beds in Portugal (see IMU.NVC_A12) (Cunha & Moreira, 1995). They reported that polychaetes showed little seasonal changes in abundance while molluscs and leeches showed high densities in spring to summer but low numbers or even absence in autumn to winter. Crustaceans (e.g. gammarids) were most abundant in autumn, while insects were rare but abundant in winter and summer. Oligochaetes were most abundant in winter, although some species of oligochaete were also abundant in spring. Seasonal changes in the macrofauna was related to seasonal changes in temperature, dissolved oxygen, tidal regime and low or high rainfall and hence freshwater runoff and salinity (Cunha & Moreira, 1995).Phragmites reed beds may be grazed by Canada and grey lag geese in spring, while other species e.g. warblers use reed beds as pre-migration feeding areas. Reed beds are used by numerous nesting birds in the spring and summer mating season, e.g. the bearded tit, reed warbler, bittern and the marsh harrier (Fuller, 1982; Hawke & José 1996).
Phragmites australis, macroalgae and microalgae supports consumers such as grazing gastropods and phytophagous insects, while its litter supports a wide variety of secondary consumers, including e.g. gammarid amphipods, isopods, chironomids, and bacteria. Wainwright et al., 2000 estimated that in Delaware Bay reed beds, Phragmites australis supported 73% of secondary productivity. Phragmites litter, resultant detritus, organic particulates and dissolved organic matter probably contribute to the wider aquatic food chain (Lee, 1990; Wainright et al., 2000). A summary of the net production and detritus dynamics in Mai Po Marshes, Hong Kong was given by Lee (1990).
Seed germination is variable and usually poor in the field, especially on organic soils (e.g. peat and within reed beds). Germination occurs over a wide range of temperatures, is slower at lower temperatures (ca 10-30 °C) and stopped by frost. The effect of water varies, some worker suggesting sowing at or below water level, other reporting germination in 1.5m of water and other no germination in 5 or 15cm of water and increased germination with drying. Germination also varies with salinity. In addition, seedlings are killed by frost, damaged by saline conditions, leave die underwater and may be stunted on organic soils, preferring mineral soils or muds with a flow of nutrient rich water (Haslam, 1972). Overall, sexual reproduction by seed is limited and seedlings are rarely observed in the field, except in new habitats devoid of other macrophytes (e.g. resulting form disturbance). However, propagation by seed is probably adequate to the long-lived clones of Phragmites (Haslam, 1972).Vegetation reproduction by clonal spread of horizontal rhizomes is probably more important to the maintenance and expansion of established beds. Once established the Phragmites produces horizontal rhizomes that spread across the surface producing new vertical shoots and roots at each internode (Hawke & José, 1996). Hawke & José (1996) reported expansion rates of 1-10m per year, sometimes faster, depending on temperature and water depth. Amsberry et al. (2000) noted that underground rhizomes spread horizontally about 1-1.5m per year. Pieces of rhizome may be transported by water or man (but die at sea) and may act as an effective mode of dispersal. Cutting of rhizomes, stems and shoots are used to propagate reed beds and fragments of the common reed would probably root in the wild if they arrived on suitable substrata.
The microalgae and filamentous macroalgae found within the biotope are wide-spread and ubiquitous, producing numerous spores, and can colonize rapidly. Similarly, bryozoans such as Conopeum seurati probably produce numerous but short lived pelagic larvae, so that local recruitment from adjacent populations is probably rapid. For example, Electra crustulenta is probably adapted to rapid growth and reproduction (r-selected), capable of colonizing ephemeral habitats, but may also be long lived in ideal conditions (Hayward & Ryland, 1998). In settlement studies, Electra crustulenta recruited to plates within 5 -6months of deployment (Sandrock et al., 1991). Boström & Bonsdorff (2000) examined the colonization of artificial seagrass beds by invertebrates. They reported colonization by abundant nematodes, oligochaetes, chironomids, copepods, juvenile Macoma baltica and the polychaete Pygospio elegans within 33-43 days. Disturbance by strong winds after 43 days resulted in a marked increase in the abundance of species by day 57, except for Pygospio elegans. They noted that settlement of pelagic larvae was less important than bedload transport, resuspension and passive rafting of juveniles from the surrounding area in colonization of their artificial habitats. The above observation suggests that most aquatic macrobenthic species in reed beds may recruit rapidly.
The stickleback Gasterosteus aculeatus may be associated with reed beds. The males set up a territory and build nests, in which the female lays eggs that are subsequently fertilized and guarded by the males (Fishbase, 2000). The abundance of vegetation provided by the reed bed and its associated algal mats probably provides nesting material for the males and a refuge for developing juveniles. While associated with this biotope, sticklebacks are mobile species capable of colonizing the habitat from adjacent areas or the open sea. Similarly, amphibians, reptiles and birds are highly mobile and probably recruit to the habitat rapidly from the surrounding areas.
This review can be cited as follows:
Tyler-Walters, H. 2002. Phragmites australis swamp and reed beds. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 29/05/2015]. Available from: <http://www.marlin.ac.uk/habitatecology.php?habitatid=304&code=1997>