Synonyms

Ruppia maritima

  Basis for Listing

Ruppia cirrhosa is an aquatic plant that occurs primarily in the western portion of North America, as well as in South America, Central America, and Europe (Haynes 2000). Detailed floristic surveys of 2,025 lakes throughout the state by the Minnesota Biological Survey have recorded R. cirrhosa only 55 times. That frequency of occurrence ranks R. cirrhosa as one of the rarer aquatic plants in the state. Ruppia cirrhosa was listed as a special concern species in Minnesota in 1996.

  Description

Ruppia cirrhosa is a submerged, aquatic plant. It is a rooted annual or perhaps a perennial with stems that may grow to 55 cm (1.8 ft.) long and 0.1-0.3 mm(0.004-0.012 in.) thick. The leaves are linear in shape with an acute tip and 1 vein running lengthwise down the middle. The leaves are 3.2-45 cm (1.3-17.7 in.) long, 0.2-0.5 mm (0.008-0.020 in.) wide, and the margins are minutely serrulate toward the tip. The inflorescence is terminal, and has fewer than 20 flowers, which are arranged in capitate spikes. The inflorescence is on a 3-30 cm (1.2-11.8 in.) long peduncle that develops 5-30 coils after fertilization. The flowers are bisexual. The fruits are drupaceous, 1.5-2 mm (0.06-0.08 in.) long, and 1.1-1.5 mm (0.04-0.06 in.) wide. Each fruit has an erect lateral beak 0.5-1 mm (0.02-0.04 in.) long.

  Habitat

Water chemistry data are available for 32 of the lakes where Ruppia cirrhosa has been found. The total alkalinity in these lakes ranges from 153 to 481 ppm (mean 239 ppm), and the pH ranges from 8.2 to 9.4 (mean 8.7). The lakes vary in size from 34 ha (85 ac.) to 2,316 ha (5,724 ac.), with a mean size of 534 ha (1,319 ac.). The lakes can, in general terms, be called alkaline or "hardwater" lakes. The species most commonly associated with R. cirrhosa are Stuckenia pectinata (Sago pondweed), Myriophyllum sibiricum (northern watermilfoil), Schoenoplectus acutus var. acutus (hardstem bulrush), Ceratophyllum demersum (coontail), Potamogeton richardsonii (Richardson's pondweed), P. friesii (Fries' pondweed), P. zosteriformis (flatstem pondweed), P. illinoensis (Illinois pondweed), Najas flexilis (flexuous naiad), and Utricularia vulgaris (common bladderwort).

  Biology / Life History

Ruppia cirrhosa has an unusually high tolerance for alkaline conditions; it can easily tolerate the most highly alkaline conditions found in Minnesota lakes. It can also function as an annual or perennial depending on habitat conditions. Ruppia cirrhosa reproduces vegetatively by stem fragments and sexually by seeds. The seeds are eaten by waterfowl, and possibly spread from lake to lake by foraging or migrating ducks. This could result in long distance dispersal. Short distance dispersal, especially dispersal within a watershed, probably occurs by seeds or stem fragments being carried from lake to lake via streams, ditches, or other waterways.

The best time to search for R. cirrhosa is when it is in flower during July and August.

  Conservation / Management

The management considerations for R. cirrhosa are similar to those of most aquatic plants species. The highest priority must be given to the maintenance of water quality. This can be achieved only by careful watershed management that prevents contaminants from reaching lakes. Attempting to remove contaminants that are already in a lake is very costly and, in most cases, not practical. Caution is also needed when using aquatic herbicides to control invasive species such as Potamogeton crispus (curly pondweed) or Myriophyllum spicatum (Eurasian watermilfoil).

Many resources and tools regarding shoreland management, including lakescaping and shoreland restoration, are available for landowners and land managers to help maintain or improve water quality, and any opportunity to incorporate these concepts would benefit R. cirrhosa as well as many other aquatic species.

  References and Additional Information

Fernald, M. L., and K. M. Wiegand. 1914. The genus Ruppia in eastern North America. Rhodora 16:119-127.

Haynes, R. R. 2000. Ruppiaceae. Pages 75-76 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 22. Oxford University Press, New York, New York.

Thorne, R. F. 1993. Potamogetonaceae. Pages 1304-1310 in J. C. Hickman, editor. The Jepson manual: Higher plants of California. University of California Press, Berkeley, Los Angeles, and London.