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Ecology of freshwater mussels in disturbed environments
Karlstad University, Faculty of Social and Life Sciences.
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The number of species extinctions is increasing at an alarming rate. Long-lived freshwater mussels of the order Unionoida, which include a parasitic stage on a host fish, are highly threatened. Habitat degradation by turbidity and sedimentation is thought to be one major reason for their decline. The objective of this thesis was to examine recruitment patterns and identify the causes of the lack of recruitment in the threatened unionoid freshwater pearl mussel (Margaritifera margaritifera). In addition, I investigated the effects of turbidity on non-endangered dreissenid mussels, where turbidity was manipulated through use of bioturbating mayflies.

In a survey of 107 Swedish streams, mussel population size and trout density were both positively correlated to recruitment probability of M. margaritifera. A more in-depth study of the age-structure of nine populations revealed that four of these populations showed no signs of recruitment over the last ten years. Within-stream variation in recruitment was high as both mussels and trout had patchy distribution, and may be important for population regulation. Moreover, examination of different life stages revealed no differences in the gravid mussel stage or the stage when mussels infect salmonid fish. Instead, differences were observed for the juvenile, benthic stage, presumably related to differences in turbidity and sedimentation. High turbidity may affect filter-feeding efficiency of mussels and high sedimentation may reduce survival by clogging sediments, thereby altering, for example, oxygen and food conditions. In the study of the effects of turbidity, bioturbating mayflies increased turbidity and filter-feeding dreissenid mussels reduced turbidity. Mussel growth both decreased and increased with increasing turbidity, depending on sediment type.

Turbidity and sedimentation often impact entire stream systems, and a holistic, catchment-based management strategy may be needed to reduce the effects of sedimentation on freshwater pearl mussels. The effects of restoration take a long time and must start soon if recruitment of mussels is to be re-established. Restoration may also be more urgent in some streams than in others, as the maximum age of M. margaritifera populations in my study differed by as much as 60 years. As mussel and trout densities seem to be important for recruitment success, one conservation method may be to concentrate mussels into sites where trout density is high.

Place, publisher, year, edition, pages
Fakulteten för samhälls- och livsvetenskaper , 2006.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2006:53
Keywords [en]
Unionoida, Margaritifera margaritifera, Dreissena, Salmo trutta, habitat degradation, turbidity, sedimentation, recruitment, conservation.
National Category
Biological Sciences
Research subject
Biology
Identifiers
URN: urn:nbn:se:kau:diva-734ISBN: 91-7063-084-4 (print)OAI: oai:DiVA.org:kau-734DiVA, id: diva2:6445
Public defence
2006-12-08, Andersalen, 11D 121, Karlstads universitet, 651 88 Karlstad, Karlstad, 13:15
Opponent
Supervisors
Available from: 2007-03-15 Created: 2007-03-15
List of papers
1. Recruitment in populations of freshwater pearl mussels (Margaritifera margaritifera) in relation to mussel population size and host density
Open this publication in new window or tab >>Recruitment in populations of freshwater pearl mussels (Margaritifera margaritifera) in relation to mussel population size and host density
(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:kau:diva-2092 (URN)
Available from: 2007-03-15 Created: 2007-03-15 Last updated: 2015-01-29Bibliographically approved
2. Population structure of Margaritifera margaritifera in streams with and without recent recruitment
Open this publication in new window or tab >>Population structure of Margaritifera margaritifera in streams with and without recent recruitment
(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:kau:diva-2093 (URN)
Available from: 2007-03-15 Created: 2007-03-15 Last updated: 2010-05-25Bibliographically approved
3. Early life stages of Margaritifera margaritifera populations – is there a coupling to recruitment patterns?
Open this publication in new window or tab >>Early life stages of Margaritifera margaritifera populations – is there a coupling to recruitment patterns?
(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:kau:diva-2094 (URN)
Available from: 2007-03-15 Created: 2007-03-15 Last updated: 2010-05-25Bibliographically approved
4. Habitat degradation and the decline of the threatened mussel Margaritifera maragaritifera: influence of turbidity and sedimentation on mussel an its host
Open this publication in new window or tab >>Habitat degradation and the decline of the threatened mussel Margaritifera maragaritifera: influence of turbidity and sedimentation on mussel an its host
2010 (English)In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 47, no 4, p. 759-768Article in journal (Refereed) Published
Abstract [en]

1. Habitat degradation is a major reason for species extinctions. For parasite–host interactions, the decline of a parasite may not only be related to the parasite’s tolerance to habitat degradation but also indirectly through the host’s tolerance to the same disturbance.

2. Our objective was to explore the cause of population declines of the freshwater pearl mussel Margaritifera margaritifera by relating the age distribution, density and growth of the mussels with turbidity, sedimentation rates and density of the mussel’s host, trout Salmo trutta, in 26 Swedish streams.

3. An analysis of the age structure of nine mussel populations showed that maximum age differed by 60 years, with five populations having low proportions of juvenile mussels. Adult mussel density was higher at sites where juvenile mussels occurred than at sites lacking juvenile mussels.

4. Growth of adult mussels during the past 10 years was lower in the five streams lacking recent recruitment than in the four streams with recent recruitment, indicating that some environmental factor may be negatively impacting these populations.

5. A comparison among 24 populations indicated that turbidity and sedimentation may be responsible for recruitment failure in 58% of the populations. The age of the youngest mussel was positively related to turbidity and sedimentation, and juvenile mussel density was negatively related to turbidity and sedimentation. In contrast, trout density was not related to recruitment of mussels or sedimentation, but was positively related to turbidity in all streams, both with and without recent mussel recruitment.

6.Synthesis and applications. Recruitment failure of M. margaritifera appears to be related to its own vulnerability to turbidity and sedimentation rather than to its host’s response to this type of habitat degradation. The results from our study suggest that managers might be able to evaluate the potential viability of mussel populations by measuring stream turbidity. Restoration activities to improve the mussels’ environment should focus on reducing fine material transport into streams.

Keywords
Habitat degradation, host-parasite, Margaritifera margaritifera, recruitment, Salmo trutta, sedimentation, turbidity, Unionoida
National Category
Biological Sciences Zoology Fish and Aquacultural Science
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-2095 (URN)10.1111/j.1365-2664.2010.01827.x (DOI)000279405100006 ()
Available from: 2007-03-15 Created: 2007-03-15 Last updated: 2018-07-19Bibliographically approved
5. Indirect environmental interactions between filter feeding mussels and bioturbating mayflies
Open this publication in new window or tab >>Indirect environmental interactions between filter feeding mussels and bioturbating mayflies
Show others...
(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:kau:diva-2096 (URN)
Available from: 2007-03-15 Created: 2007-03-15 Last updated: 2010-05-25Bibliographically approved

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