Brackish water pool (S2)
Brackish water pools occur on the Isles of Shoals in small depressions within maritime rocky barrens. They typically range from a few to several square meters in size. Depending on salinity, fresh and/or brackish water graminoids and forbs occur within and along the margins of these pools. Salinity fluctuates as a result of salt inputs from storm waves and salt spray, fresh water precipitation, and evaporation. The substrate consists of various types of bedrock.
Characteristic vegetation: Fresh water species include Anagallis arvensis (scarlet pimpernel), Epilobium ciliatum (ciliated willowherb), Hordeum jubatum (foxtail barley), Iris versicolor (northern blue flag), Lemna minor (lesser duckweed), Lycopus uniflorus (common water horehound), Lythrum salicaria (purple loosestrife), Persicaria hydropiper (water pepper), P. pensylvanica (Pennsylvania smartweed), P. punctata (dotted smartweed), Portulaca oleracea (common purslane), Ranunculus sceleratus (cursed crowfoot), Scutellaria galericulata (marsh skullcap), and Typha latifolia (common cattail).
Species present that are often associated with brackish conditions, especially when they are commonly found together, include Agrostis stolonifera (common creeping bentgrass), Argentina egedii ssp. groenlandica (coastal silverweed), Bolboschoenus robustus (stout bulrush), Carex hormathodes (necklace sedge), Eleocharis uniglumis (salt-loving spike-rush), Juncus bufonius (inland toad rush), J. gerardii (salt marsh rush), J. pelocarpus (mud rush), Lythrum hyssopifolium (hyssop-leaved loosestrife), Plantago maritima var. juncoides (salt marsh plantain), Schoenoplectus pungens (three-square rush), Solidago sempervirens (seaside goldenrod), Spergularia salina (seabeach sand spurrey), Symphyotrichum novi-belgii (New York aster), S. subulatum (small salt marsh aster), and Typha angustifolia (narrow-leaved cattail).
Good examples of this community can be found on the Isles of Shoals.
Brackish water pools sometimes occur as part of a larger maritime rocky shore system.
Brackish water pool on the Isles of Shoals (photo by Dan Sperduto)