|Basic Information||Biotope classification||Ecology||Habitat preferences and distribution||Species composition||Sensitivity||Importance|
Image Anon. - Ruppia maritima in reduced salinity infralittoral muddy sand. Image width ca 40 cm.
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SS.SMp.SSgr.Rup recorded () and expected () distribution in Britain and Ireland (see below)
The rhizomes and roots of Ruppia maritima help to stabilize, and oxygenate, the sediment surface, while the stems and leaves provide additional substratum for a variety of algae and invertebrates. Although the functional groups within the ecosystem probably remain fairly constant the abundance and diversity of species within each group varies with the habitat, especially the salinity regime (e.g. Verhoeven & van Vierssen, 1978). Ruppia maritima and Ruppia cirrhosa provide primary production and substratum within the biotope. Few organisms, except wildfowl, feed on the Ruppia spp. directly, however, 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 drift line communities (Verhoeven & van Vierssen, 1978; Zieman et al., 1984; Kantrud, 1991).
Additional, primary productivity is provided by microbial (e.g. diatoms) and macroalgal epiphytes growing on the leaves of Ruppia spp., and a floating mat of filamentous algae (e.g. Chaetomorpha sp. and Cladophora spp.) and, when present, stoneworts (e.g. Chara aspera and Lamprothamnium papulosum).
The leaves of Ruppia spp. and the algal mats may provide temporary substratum for juvenile anemones and bivalves (e.g. Anemonia sulcata, Mytilus edulis, Cerastoderma glaucum) and the larvae and pupae of aquatic insects (e.g. the shore fly, Ephydra riparia) (Verhoeven & van Vierssen, 1978; Verhoeven 1980a; Boström & Bonsdorf, 2000). Aquatic insects probably utilize any available aquatic macrophytes as substratum.
The epiphytes and algal mats may be grazed by gastropods (e.g. Rissoa spp., Hydrobia spp. or Potamopyrgus spp.), amphipods (e.g. Gammarus spp.) and isopods (e.g. Jaera spp., and Idotea spp.) and probably mysids (e.g. Neomysis integer).
Verhoeven & van Vierssen (1978) and Verhoeven (1980b) suggested that isopods and amphipods may feed directly on Ruppia spp., however, their most important role in the food chain was the breaking down of decomposing leaves into fine particles of detritus suitable for suspension and deposit feeders in the detrital food chain.
Suspension feeders filter both phytoplankton and detritus (organic particulates), for example Corophium spp., Cerastoderma glaucum, Mya arenaria, hydroids, bryozoans, and polychaetes (Hediste diversicolor, Polydora spp.).
Surface and infaunal deposit feeders include polychaetes (e.g. Arenicola marina, Manayunkia aestuarina and Pygospio elegans), amphipods (e.g. Corophium volutator), bivalves (e.g. Macoma baltica), and chironomid larvae.
Small invertebrates are preyed on by small mobile predators that use the Ruppia beds for shelter, for examples insect larvae, mysids, shrimp and sticklebacks (e.g. Gasterosteus aculeatus and Spinachia spinachia).
Several species of wildfowl feed directly on Ruppia spp., although the exact species will vary with location, season and salinity, e.g. the tufted duck Aythya fuligula, the coot Fulica atra, the wigeon Anas penelope, the mute swan Cygnus olor.
Mysids, shrimp and crabs probably act as scavengers within this biotope.
Detailed lists of species and their position within the habitat for several locations in western Europe (Finland, the Netherlands, and France) are given by Verhoeven and his co-author (Verhoeven & van Vierssen, 1978; Verhoeven, 1979, 1980a, b).
Seed germinate in a wide variety of temperatures and salinity. For example, in Europe Ruppia maritima seeds began to germinate when the water temperature exceeded a minimum/maximum interval of 10/15 °C, and mainly between 15-30 °C. Prior desiccation may stimulate germination. Seeds will germinate in as little as 5-10cm of water in culture, although seed production is reduced in shallow waters (Kantrup, 1991). The effect of salinity on germination is temperature dependant. For example, Ruppia maritima seeds germinate well at 43.4 psu at 28°C but germination rates is lower at high temperatures and low salinities (<3.5psu) than at low temperatures and salinities up to 26 psu (Kantrup, 1991). Germination may also be affected by oxygen levels and seeds in poorly oxygenated sediments lie dormant until the next year (Kantrup, 1991).
Ruppia maritima can also colonize by rhizomes. Over-wintering rhizomes bud in early spring, at about the same time as germination, probably in response to temperature (Kantrup, 1991). Over-wintering rhizomes is of greater importance than seed set in perennials such as Ruppia cirrhosa. In perennials the pollination occurs at the water interface, which is less efficient than underwater, and their allocation to reproductive shoots is less than to vegetative production. Orth & Moore (1982) reported that recolonization of sediment denuded of Ruppia spp. by a boat propeller occurred at about 0.25 m/yr.
Ruppia species distribution is affected by the isolated nature of their habitats (e.g. lagoons) and their ability to disperse. Seeds and rhizomes can be transported by currents attached to floating detached plant material. After desiccation, dried plants and attached seed can be transported considerable distances by the wind. A proportion of the seed consumed by wildfowl pass through the birds unharmed, therefore, wildfowl could potentially transport seed considerable distances. For example, 30% of the freshwater eelgrass Naja marina seeds fed to ducks in Japan survived and successfully germinated after passage through their alimentary canals and could be potentially transported 100-200km (Fisherman & Orth 1996). Verhoeven (1979) noted that Ruppia maritima produces large amount of seed and was the most cosmopolitan Ruppia species, suggesting the potential for wide dispersal.
However, competition with infauna such as Hediste diversicolor or Arenicola marina have been suggested to hamper potential recruitment in Zostera noltii (see review) (Hughes et al., 2000; Philippart, 1994a). Similarly, Corophium volutator has been reported to inhibit colonization of mud by Salicornia sp. (Hughes et al., 2000). Therefore, the above infaunal species could potentially inhibit recruitment in Ruppia spp.
The microalgae and filamentous macroalgae found within the biotope are wide-spread and ubiquitous, producing numerous spores, and can colonize rapidly. Similarly, bryozoans and hydroids probably produce numerous but short lived pelagic larvae, so that local recruitment from adjacent populations is probably rapid.
Boström & Bonsdorff (2000) examined the colonization of artificial seagrass and Ruppia maritima 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. Other polychaetes, such as Arenicola marina do not possess a pelagic larvae, but migrate as juveniles and can swim as adults. Recolonization in Arenicola marina is thought to be rapid where adjacent populations are present, although recolonization may take longer in isolated populations.
The sticklebacks Gasterosteus aculeatus and Spinachia spinachia are associated with Ruppia beds. In both species 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 Ruppia 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.
Ruppia spp. seed and rhizomes can be transported considerable distances by wildfowl or by water currents and wind (when dry). Floating fragments of Ruppia spp. grow roots freely, sink and attach to the bottom. For example, Orth & Moore (1982; cited in Kantrup, 1991) reported that sediments denuded by a boat propeller were recolonized at about 0.25m /year. However, little other evidence of colonization rates was found.
Community development will depend on the time taken for Ruppia propagules to reach the available habitat. Once rhizomes or seed arrive in the habitat recovery may take several years. In areas connected by water flow or regularly frequented by wildfowl recovery will take many years, but in isolated area habitat recovery may be prolonged, possibly taking up to 5-10 years.
The benthic infauna probably colonizes the associated sediment more slowly but still relatively rapidly. For example, Broström & Bonsdorff (2000) found that abundant infauna colonized artificial seagrass and Ruppia maritima habitats within 33 - 57 days (1-2 months). Few species found in Ruppia dominated communities are associated with Ruppia spp. alone (Verhoeven & van Vierssen, 1978; Verhoeven, 1980a) and most probably colonize the vegetation from the surrounding habitats.
This review can be cited as follows:
Tyler-Walters, H. 2001. Ruppia maritima in reduced salinity infralittoral muddy sand. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 11/03/2014]. Available from: <http://www.marlin.ac.uk/habitatecology.php?habitatid=266&code=2004>
Ruppia maritima in reduced salinity infralittoral muddy sand
Ruppia maritima in reduced salinity infralittoral muddy sand