Changes in biofilms induced by flow regulation could explain extinctions of aquatic snails in the lower River Murray, Australia

Notopala sublineata, Notopala hanleyi(Viviparidae) andThiara balonnensis (Thiaridae) are prosobranchgastropodsthat were once abundant in the lower River Murray. These andothersnail taxa have declined markedly over the last 50 years,coinciding with increased flow regulation by dams and weirs.Inthis p...

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Bibliographic Details
Published in:Hydrobiologia 1997-03, Vol.347 (1-3), p.97-108
Main Authors: SHELDON, F, WALKER, K. F
Format: Article
Language:English
Subjects:
Algae
Animal and plant ecology
Animal populations
Animal reproduction
Animal, plant and microbial ecology
Animals
Biofilms
Biological and medical sciences
Biomass
Demecology
Detritus
Food resources
Freshwater
Fundamental and applied biological sciences. Psychology
Gastropoda
Mollusks
Nutritive value
Protozoa. Invertebrata
River ecology
Rivers
Turbidity
Water levels
Weirs
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Summary:Notopala sublineata, Notopala hanleyi(Viviparidae) andThiara balonnensis (Thiaridae) are prosobranchgastropodsthat were once abundant in the lower River Murray. These andothersnail taxa have declined markedly over the last 50 years,coinciding with increased flow regulation by dams and weirs.Inthis paper we speculate that the decline may be linked tochangesin the nature of food resources. Before regulation, most ofthebiofilm biomass in the lower Murray probably was microbial, asfluctuating water levels and high turbidity would havemaintainedthese communities in a state of early succession. Bystabilisingseasonal water levels, we suggest that regulation has promotedthegrowth of filamentous algae, perhaps at the expense ofbacteria.Evidence from gut and faecal pellet analysis, and fromanalysis ofcarbon stable-isotopes, suggests that the gastropod taxa aredetritivores, feeding mainly on amorphous organic detritus.Algaehave a relatively high C:N ratio (low nutritional value) andmay bean inadequate food to maintain female growth and reproduction,especially in viviparous snails.[PUBLICATION ABSTRACT]
ISSN:0018-8158
1573-5117
DOI:10.1023/A:1003019302094