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<title>NPWRC :: Wigeongrass: A Literature Review</title>
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    <h1>Wigeongrass (<em>Ruppia maritima</em> L.):<br>
      A Literature Review</h1>
    <h2><em>Abstract</em></h2>
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  Wigeongrass (<em>Ruppia maritima</em> L.) is a submersed macrophyte of nearly 
  cosmopolitan distribution and worldwide importance as a waterfowl food. Unfortunately, 
  the plant no longer inhabits vast areas disturbed by human activities. Taxonomic 
  status of the plant is uncertain, especially in North America. In mild climates, 
  in habitats subject to environmental extremes, the plant behaves as an annual 
  (vegetation perishes), or as a perennial in deeper, more stable habitats (some 
  vegetative parts grow year round). Drupelets (seeds) provide a mechanism for 
  wigeongrass to survive periods of drought and excessive water salinity. These 
  sexual propagules can be washed ashore or carried by birds or fish for long 
  distances.
  <p> Wigeongrass mostly occurs in temporarily to permanently flooded mesohaline-hyperhaline 
    estuarine wetlands, but it also occurs inland in fresh to hypersaline palustrine 
    and lacustrine wetlands. Most populations inhabit warm, relatively unpolluted, 
    and well lit waters < 2.0 m deep where fetches and wave action are not 
    great. The species is probably best adapted to stable water levels but can 
    tolerate significant water level fluctuations, including periodic exposure 
    in tidal areas. Robust growth occurs in areas of slow current. Wigeongrass 
    is alone among the submersed North American angiosperms in tolerance to high 
    salinity, but it is likely at a competitive disadvantage among specialist 
    taxa in soft or acidic waters. The species grows in nearly all common bottom 
    substrates, but growth is favored by aerobic and low H<sub>2</sub>S conditions. 
    Turbidity frequently limits wigeongrass growth in waters overlying easily 
    suspendible bottom substrates.
  <p> Wigeongrass often occurs in monotypic stands, yet grows with many other 
    submersed and emergent macrophytes. Dominance in certain wetlands sometimes 
    alternates with dominance by other submersed macrophytes as salinities, seasonal 
    temperature cycles, or other environmental factors change. The shading effect 
    of metaphytic, planktonic, or epiphytic algae often reduces production.
  <p> Wigeongrass and its detritus provide food and cover for a large invertebrate 
    biota, although direct consumption of the living plants is minimal. Wigeongrass 
    beds in coastal wetlands are heavily used by fish. The plant is recognized 
    worldwide as an important food of migrant and wintering waterfowl, wading 
    birds, and shorebirds. In subtropical climates, wintering waterfowl can quickly 
    consume entire stands.
  <p> Propagation and management of wigeongrass has occurred for nearly 60 years 
    in the southern and eastern United States. During the seventies and eighties, 
    sophisticated water level and salinity management techniques have been developed 
    to encourage growth of the plant.
  <p> Future research should concentrate on determining the means to reduce light-limiting 
    turbidity in many wetland types; understanding the ways in which human activities 
    on and near wetlands affect wigeongrass production; and developing reliable 
    and predictable techniques to stimulate wigeongrass production bywater level 
    manipulations and other means in different environmental settings. Trophic 
    interactions and the effects of biomanipulation of fish populations in managed 
    wigeongrass habitat - now little understood - also require more study. 
  <p> 
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  Return to Contents <br>
  Next Section -- Introduction 
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