The natural salt springs on Saltspring Island, southwestern British Columbia, originate from a source at least 1000 m deep and are distinct in chemical composition not only from the surrounding seawater but also from the groundwater-based salt springs on nearby Mayne Island. Spring water is approximately 2.2-fold more saline than average seawater and is characterized by having significantly higher levels of chloride, sodium, sulphate, silica, iron, alumina, and boron; similar levels of calcium, potassium, fluoride, and nitrogen; but less magnesium. The pH levels in different springs vary between 7.3 and 7.9, compared with pH 8.2 for average surface seawater. Near-surface water temperatures range from 7 °C in mid-winter to 16–21 °C in late summer.The flora and fauna that exploit this unique habitat are characterized by halophilic species known from other saline environments such as saline lakes, brackish water, beaches, and the intertidal zone. Organisms that have been isolated and identified include the following: seven species of bacteria, none of which depends exclusively on a saline environment; a blue-green alga that lives within the springs; an abundant filamentous green alga; and halophilic higher plants and grasses. Two species of spiders [Zelotes sp. (Gnaphosidae) and Pardosa sp. (Lycosidae)] are active in the salt-impregnated areas surrounding the springs.Collembola are represented by Anurida sp. (Poduridae); and insects by Saldula comatula (Saldidae, Hemiptera), the chironomids (Chironomidae, Diptera) Thalassosmittia marina plus two unidentified species, brine flies (Ephydridae, Diptera), and two unidentified cyclorrhaphan dipterans. Among the Hymenoptera, there are two species of Eupteromalus (Pteromalidae), Cyrtogaster capitanea (Pteromalidae), Urolepis rufipes (Pteromalidae), and Stigmus sp. (Pemphredonidae). Ants (Formica spp.) and yellowjackets (Vespula sp.) are frequent foragers in the immediate vicinity of the salt spring. There are three species of Coleoptera, Bembidion indistinctum (Carabidae), Ochthebius lecontei (Hydraenidae), and Thicanus mimus (Anthicidae). These insects are discussed in terms of their distribution within, and preference for, saline environments.