File:American malacological bulletin (1987) (17535828223).jpg

Title: American malacological bulletin
Identifier: americanmal4519861987amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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arfiiqineum 0 12 3 4 TOTAL ALKALINITY mg CaCG3 L"1 Fig. 4. Trends in natalities of three species of mollusks common in low-alkalinity lakes in south-central Ontario. Curves are based on data reported by Servos ef al. (1985). in low-alkalinity lakes of southern Ontario, Canada (Figs. 6, 7). Rooke and Mackie (1984c) reported greater levels of an- nual production of Amnicola limosa in higher alkalinity lakes (70 - 80 mg m"2) than in low-alkalinity lakes (0 - 26 mg m"2). However, the annual production of some species of Pisidiidae (Pisidium casertanum, P. ferrugineum) appeared to be similar between low- and high-alkalinity lakes. Nevertheless, the an- nual production of other pisidiids (including P. compressum, P. variabile, and Sphaerum striatinum) must be affected because they are not found in low-alkalinity lakes. Using data in Mackie and Flippance (1983c), figure 7 shows extremely large variations in the numbers of species of freshwater mollusks in lakes with high alkalinities (greater than about 20 mg CaCo3 M). Hence, factors other than pH and alkalinity seem to affect the diversity of mollusks in en- vironments with alkalinities exceeding about 20 mg CaCo3 I"1, but below this value, pH and alkalinity explain a large part of the variation in diversity. Harman and Berg (1971), Harrel and Dorris (1968), Harrison ef al. (1970), and Houp (1970) have all reported direct correlations between alkalinity and production and diversity of mollusks, but all studies were done on waters with alkalinities exceeding 20 mg CaC031"1. Hunter (1964) claims that calcium is a better predictor of species diversity; waters with > 25 mg Ca I"1 can support all molluscan species in a geographic region, waters with 10 to 25 mg Ca I"1 can support 55%, waters with 5 to 10 mg Ca I"1 can support about 40%, and waters with < 3 mg Ca I"1 support less than 5%. Finally, the type of faunal community also seems to be affected. The community appears to change from one con- taining a large proportion of epifaunal grazers (e.g. gastropods) to infaunal filter feeders (e.g. Pisidiidae). The organisms that survive the longest in low-alkalinity lakes ap- pear to be those that are associated with the sediments, perhaps because the sediments have a greater capacity to buffer additions of hydrogen ions than does the water. Cont ro 6.4-6.9
Text Appearing After Image:
TIME (DAYS) Fig. 5. Graph to show the times at which eggs of Amnicola limosa kept at different pH's fail to keep pace with eggs kept at pH 6.4 to 6.9 (i.e. control) (e.g. eggs kept at pH 5 are at the same stage of development as the control eggs for up to 10 days, after which eggs at pH 5 fail to develop). Graph is based on data in Servos ef al. (1985).

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