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Non-indigenous zooplankton: the role of predatory cladocerans and of copepods in trophic dynamics
Stockholm University, Faculty of Science, Department of Systems Ecology.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Human-mediated introductions of non-indigenous species now threaten to homogenize the biota of the Globe, causing huge economic and ecological damage. This thesis studies the ecological role of 3 invasive planktonic crustaceans, the omnivorous copepod Acartia tonsa (western Atlantic and Indo-Pacific) and the predatory cladocerans, Cercopagis pengoi (Ponto-Caspian) and Bythotrephes longimanus (Eurasian). B. longimanus invaded the North American Great Lakes in 1982, C. pengoi the Baltic in 1992 and the Great Lakes in 1999, while A. tonsa has an extensive invasion history that includes the Baltic.

We review current knowledge on feeding biology of the predatory cladocerans. A study of stable C and N isotope ratios indicated mesozooplankton as the main food source of C. pengoi in the northern Baltic Sea proper, with young C. pengoi also eating microzooplankton, such as rotifers. Young-of-the-year herring did eat C. pengoi and herring trophic position shifted from 2.6 before the invasion to 3.4 after, indicating that C. pengoi had been “sandwiched” into the modified food web between mesozooplankton and fish.

Salinity tolerance experiments on Acartia tonsa and co-occurring Acartia clausi showed the formers euryhaline character and high grazing potential. Energy partitioning between ingestion, production and respiration was rather constant over the tested salinity range of 2 to 33, with small differences in gross growth efficiency and cost of growth, but maximum ingestion at 10-20. Egg hatching in A. tonsa was only reduced at the lowest salinity. Extreme changes in salinity were needed to cause significant mortality of A. tonsa in the field, but its feeding activity could be severely reduced by salinity changes likely to occur in estuaries. A study of a hypertrophic estuary showed that A. tonsa can sustain a population despite very high mortality rates, caused by predation, high pH and low oxygen, helping explain the success of A. tonsa as an invader of estuaries.

Place, publisher, year, edition, pages
Stockholm: Systemekologiska institutionen , 2009. , 53 p.
Keyword [en]
Acartia tonsa, Bythotrephes longimanus, Cercopagis pengoi, egg production, fitness, food web changes, ingestion rates, invasive species, metabolic balance, mortality, non-indigenous zooplankton, predation impact, salinity tolerance, stable isotopes
National Category
Ecology
Research subject
Marine Ecology
Identifiers
URN: urn:nbn:se:su:diva-8506ISBN: 978-91-7155-822-0 (print)OAI: oai:DiVA.org:su-8506DiVA: diva2:200390
Public defence
2009-03-13, sal G, Arrheniuslaboratorierna, Svante Arrhenius väg 14-18, Stockholm, 13:00
Opponent
Supervisors
Available from: 2009-02-19 Created: 2009-02-11Bibliographically approved
List of papers
1. The feeding biology of invasive predatory cladocerans
Open this publication in new window or tab >>The feeding biology of invasive predatory cladocerans
Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-25729 (URN)
Note
Part of urn:nbn:se:su:diva-8506Available from: 2009-02-19 Created: 2009-02-11 Last updated: 2010-01-13Bibliographically approved
2. Stable isotopes show food web changes after invasion by the predatory cladoceran Cercopagis pengoi in a Baltic Sea bay
Open this publication in new window or tab >>Stable isotopes show food web changes after invasion by the predatory cladoceran Cercopagis pengoi in a Baltic Sea bay
2005 (English)In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 143, no 2, 251-259 p.Article in journal (Refereed) Published
Abstract [en]

Cercopagis pengoi, a recent invader to the Baltic Sea and the Laurentian Great Lakes, is a potential competitor with fish for zooplankton prey. We used stable C and N isotope ratios to elucidate trophic relationships between C. pengoi, zooplankton (microzooplankton, 90–200 m, mostly copepod nauplii and rotifers; mesozooplankton, >200 m, mostly copepods), and zooplanktivorous fish (herring, size range 5–15 cm and sprat, 9–11 cm) in a coastal area of the northern Baltic Sea. The isotope ratios in C. pengoi and fish were much higher than those of zooplankton, showing general trends of enrichment with trophic level. Young-of-the-year (YOY) herring had a significantly higher 15N/14N ratio than C. pengoi, suggesting of a trophic linkage between the two species. To evaluate the possible relative importance of different food sources for C. pengoi and YOY herring, two-source isotope-mixing models for N were used, with micro- and mesozooplankton as prey for C. pengoi and mesozooplankton and C. pengoi as prey for YOY herring. These models indicate that mesozooplankton was the major food source of both species. However, microzooplankton may be important prey for young stages of C. pengoi. Comparative analyses of the herring trophic position before and after the invasion by C. pengoi showed a trophic level shift from 2.6 to 3.4, indicating substantial alterations in the food web structure. Our findings contribute to a growing body of evidence, showing that C. pengoi can modify food webs and trophic interactions in invaded ecosystems.

Keyword
Diet, Effects of preservation and storage, Invasive species, Zooplankton, Zooplanktivorous fish
National Category
Ecology
Identifiers
urn:nbn:se:su:diva-25730 (URN)10.1007/s00442-004-1791-0 (DOI)
Available from: 2009-02-19 Created: 2009-02-11 Last updated: 2017-12-13Bibliographically approved
3. Salinity modulates the energy balance and reproduction success of co-occurring copepods Acartia tonsa and A. clausi in different ways
Open this publication in new window or tab >>Salinity modulates the energy balance and reproduction success of co-occurring copepods Acartia tonsa and A. clausi in different ways
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2006 In: Marine Ecology Progress Series, ISSN 0171-8630, Vol. 312, 177-188 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25731 (URN)
Note
Part of urn:nbn:se:su:diva-8506Available from: 2009-02-19 Created: 2009-02-11Bibliographically approved
4. Instantaneous salinity reductions affect the survival and clearance rates of the co-occurring copepods Acartia tonsa and A. clausi differently
Open this publication in new window or tab >>Instantaneous salinity reductions affect the survival and clearance rates of the co-occurring copepods Acartia tonsa and A. clausi differently
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2008 In: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, Vol. 362, no 1, 18-25 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25732 (URN)000258354800003 ()
Note
Part of urn:nbn:se:su:diva-8506Available from: 2009-02-19 Created: 2009-02-11Bibliographically approved
5. High reproduction, but low biomass: mortality estimates of the copepod Acartia tonsa in a hyper-eutrophic estuary
Open this publication in new window or tab >>High reproduction, but low biomass: mortality estimates of the copepod Acartia tonsa in a hyper-eutrophic estuary
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2008 In: Aquatic Biology, ISSN 1864-7782, Vol. 2, no 1, 93-103 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25733 (URN)
Note
Part of urn:nbn:se:su:diva-8506Available from: 2009-02-19 Created: 2009-02-11Bibliographically approved

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