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Evidence of population genetic effects of long-term exposure to contaminated sediments: A multi-endpoint study with copepods
Stockholm University, Faculty of Science, Department of Systems Ecology.
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Systems Ecology.
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
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2008 (English)In: Aquatic Toxicology, ISSN 0166-445X, E-ISSN 1879-1514, Vol. 86, no 3, 426-436 p.Article in journal (Refereed) Published
Abstract [en]

In the environment, pollution generally acts over long time scales and exerts exposure of multiple toxicants on the organisms living there. Recent findings show that pollution can alter the genetics of populations. However, few of these studies have focused on long-term exposure of mixtures of substances. The relatively short generation time (ca. 4–5 weeks in sediments) of the harpacticoid copepod Attheyella crassa makes it suitable for multigenerational exposure studies. Here, A. crassa copepods were exposed for 60 and 120 days to naturally contaminated sediments (i.e., Svindersviken and Trosa; each in a concentration series including 50% contaminated sediment mixed with 50% control sediment and 100% contaminated sediment), and for 120 days to control sediment spiked with copper. We assayed changes in FST (fixation index), which indicates if there is any population subdivision (i.e., structure) between the samples, expected heterozygosity, percent polymorphic loci, as well as abundance. There was a significant decrease in total abundance after 60 days in both of the 100% naturally contaminated sediments. This abundance bottleneck recovered in the Trosa treatment after 120 days but not in the Svindersviken treatment. After 120 days, there were fewer males in the 100% naturally contaminated sediments compared to the control, possibly caused by smaller size of males resulting in higher surface: body volume ratio in contact with toxic chemicals. In the copper treatment there was a significant decrease in genetic diversity after 120 days, although abundance remained unchanged. Neither of the naturally contaminated sediments (50 and 100%) affected genetic diversity after 120 days but they all had high within treatment FST values, with highest FST in both 100% treatments. This indicates differentiation between the replicates and seems to be a consequence of multi-toxicant exposure, which likely caused selective mortality against highly sensitive genotypes. We further assayed two growth-related measures, i.e., RNA content and cephalothorax length, but none of these endpoints differed between any of the treatments and the control. In conclusion, the results of the present study support the hypothesis that toxicant exposure can reduce genetic diversity and cause population differentiation. Loss of genetic diversity is of great concern since it implies reduced adaptive potential of populations in the face of future environmental change

Place, publisher, year, edition, pages
2008. Vol. 86, no 3, 426-436 p.
Keyword [en]
Long-term exposure, Contaminant mixtures, Biodiversity, Genetic diversity, Genetic differentiation, RNA, Environmental risk assessment
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-24661DOI: 10.1016/j.aquatox.2007.12.003ISI: 000254449600010OAI: oai:DiVA.org:su-24661DiVA: diva2:198034
Available from: 2008-02-07 Created: 2008-02-07 Last updated: 2016-03-30Bibliographically approved
In thesis
1. Coping with environmental stress: from the individual and population perspective
Open this publication in new window or tab >>Coping with environmental stress: from the individual and population perspective
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Natural stress and disturbances are important factors affecting the structure and function of ecosystems. However the magnitude of stress has escalated due to anthropogenic activities. Environmental monitoring and toxicity assessments try to protect ecosystems from unwanted human alterations. The aim of this Doctoral thesis was to increase the understanding of the complex effects that environmental stress has on individuals and invertebrate populations. The low saline environment in the Baltic Sea is perceived as stressful for most organisms living there. In Paper I, it was found that Baltic blue mussels living in the less saline northern Baltic Proper (~5 psu) had lower basal metabolism and were more susceptible to toxic exposure than the mussels in the south (~7 psu). There was no genetic differentiation between the mussels from the northern and southern areas while there were genetic differences between mussels from sites within the respective areas (Paper III), indicating that there is not a simple relationship between the health of the mussels and genetic diversity in the microsatellite loci studied. In Paper IV it was found that the heat tolerance of the intertidal dogwhelk Nucella lapillus is oxygen dependent. Increased oxygen levels resulted in higher survival rate. Protein expression profiles also became more similar to those of the controls, compared to the whelks exposed to high temperature and normal oxygen levels. In Paper V and VI it was found that exposure to a single toxicant for more than one generation decreased the genetic diversity in exposed copepod populations even though abundances remained unaltered. In Paper VI, exposure to naturally contaminated sediments, which contained of a mixture of toxicants, did not decrease genetic diversity. However the genetic divergence (FST) within the treatments was very high, probably due to small effective population sizes in the replicates. Likewise in Paper III, the very low blue mussel abundance in the north together with the stressful environment suggests a small effective population in the northern Baltic Proper. In conclusion, my studies show that, measuring effects on several levels, including both functional and structural endpoints will both increase the sensitivity of the tests and increase their ecological relevance.

Place, publisher, year, edition, pages
Stockholm: Systemekologiska institutionen, 2008. 37 p.
Keyword
Environmental stress, Genetic diversity, Multi-level approach, Invertebrates
National Category
Ecology
Research subject
Systems Ecology
Identifiers
urn:nbn:se:su:diva-7311 (URN)978-91-7155-566-3 (ISBN)
Public defence
2008-02-29, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 10:00
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Available from: 2008-02-07 Created: 2008-02-07Bibliographically approved

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