Variation in tolerance to low environmental pH by the crayfish Orconectes rusticus, O. propinquus, and Cambarus robustus

Abstract

We compared the tolerance of three common Ontario crayfish species to low pH under natural and laboratory conditions in water varying in aluminum concentration and hardness. Both transplant and laboratory experiments indicated that exposure to a pH range of 5.4–6.1 in soft water was toxic to attached juvenile stages of Orconectes rusticus and O. propinquus but not to females carrying the broods. In contrast, stage III juveniles of Cambarus robustus molted and survived in soft water at pH 4. Cambarus robustus is clearly far less sensitive to low pH stress than the two Orconectes species. No increased mortality due to the presence of elevated aluminum occurred among stage III juveniles of the three species exposed to pH 4.5–5.0 in soft water. Physiological differences, augmented by differences in life cycle, may account for the continued presence of C. robustus in acid-stressed lakes and streams.

The Bioavailability and Toxicity of Aluminum in Aquatic Environments

“…Aluminum could, therefore, act as an additional stress and be important in determining crayfish survival in the pH range 5 to 6. In more acidic conditions, acidity alone is so toxic to crayfish that Al has no additional effect on survival of Orconectes propinquus, Orconectes rusticus, and Cambarus robustus (15-d exposures to pH 4.5 to 5.0, ~1000 to 2000 µg · L -1 Al, 60 µM Ca; Berrill et al, 1985). Liming a reach of an experimentally acidified stream (pH ~4.5, ~700 µg · L -1 Al, ~60 µM Ca, 24 h) appeared to alleviate some of the Na loss from the hemolymph in the crayfish Austropotamobius pallipes (Weatherley et al, 1989).…”

The effects of short-term laboratory pH depressions on molting, mortality and major ion concentrations in the mayflies Stenonema femoratum and Leptophlebia cupida

“…Therefore, we have little indication to what degree toxicity or ion loss is correlated with the observed loss of aquatic insects from streams currently undergoing acidification. In contrast, the degree of toxicity and wholebody Na and Cl loss during laboratory exposures to low pH is correlated with interspecific differences in the acid sensitivity of some fish, amphibians and crustaceans observed in the field (Fraser & Harvey, 1984;Freda & Dunson, 1984;Havas & Likens, 1985;Berrill et al, 1985;Hollett et al, 1986). Given that aquatic insects, including mayflies, share similar mechanisms of ionic regulation as these taxa (Shaw & Stobbart, 1963;Komnick, 1977) we should expect greater mortality and whole-body ion loss in species lost from acidified streams than those that are not.…”

Influence of lake pH on the distribution, abundance and health of crayfish in Canadian Shield lakes

“…Several studies have demonstrated the distribution of crayfish to be dependent upon lake pH (Svardson in France, 1983;Berrill et al, 1985). Further evidence suggests Cambarus spp.…”

“…to be more tolerant of acidity than Orconectes spp. (Collins et al, 1981: Berrill et al, 1985Hollett et al, 1986). In the present study, however, there -Olconetes spp.…”