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Biochemical proxies for growth and metabolism in Acartia bifilosa (Copepoda, Calanoida)
Stockholm University, Faculty of Science, Department of Systems Ecology.
Stockholm University, Faculty of Science, Department of Systems Ecology.
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2009 (English)In: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, Vol. 7, 785-794 p.Article in journal (Refereed) Published
Abstract [en]

Biochemical proxies are becoming increasingly common for growth assessment in zooplankton. Their suitability is often unknown, however, and proper calibration is lacking. We investigated correlations between physiological variables (ingestion, egg production, and respiration rates) and biochemical indices related to protein synthesis (RNA content, RNA:DNA ratio, RNA:protein ratio, and protein specific aminoacyl-tRNA synthetases [spAARS] activity) in copepods Acartia bifilosa exposed to different algal concentrations (0–1200 µg C L–1). All variables assayed increased with increasing food concentration either linearly (spAARS) or nonlinearly (all other variables). Egg production and ingestion rates were significantly and positively correlated with RNA content and RNA:protein ratio, whereas correlations with spAARS and RNA:DNA ratio were weaker or nonsignificant. However, when RNA:DNA ratio and spAARS activity were used as predictors of ingestion, together they had higher explanatory value than did either variable separately. As there were substantial differences in saturating food concentrations among the assayed variables, applicability of biomarkers as proxies of physiological rates will be more reliable if restricted to the nonsaturated phase of the functional response of either variable, unless both variables saturate simultaneously. These findings contribute to methodology of zooplankton growth assessment and to our understanding of biochemical processes underlying growth and metabolism in copepods.

Place, publisher, year, edition, pages
2009. Vol. 7, 785-794 p.
National Category
Ecology
Research subject
Marine Ecology
Identifiers
URN: urn:nbn:se:su:diva-32862ISI: 000273294600007OAI: oai:DiVA.org:su-32862DiVA: diva2:281841
Available from: 2009-12-17 Created: 2009-12-17 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Summer cyanobacterial blooms in the Baltic Sea - implications for copepod recruitment
Open this publication in new window or tab >>Summer cyanobacterial blooms in the Baltic Sea - implications for copepod recruitment
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

During summer, the Baltic Sea is subjected to the world’s largest cyanobacterial blooms. These blooms are linked to eutrophication and raise many questions concerning their effects on the ecosystem. To understand their impacts on the food web dynamics, it is essential to assess growth responses of grazers to these cyanobacteria. In the northern Baltic proper, copepods are the most important herbivores providing an essential link between the primary producers and higher trophic levels. In this Thesis, Papers I & II evaluate methods to estimate copepod growth in response to feeding conditions in situ. The most conspicuous diazotrophic filamentous cyanobacterium in the Baltic Sea is Nodularia spumigena, a producer of nodularin which is highly toxic to vertebrates, yet its ecological role is largely unknown. In Paper III, reciprocal interactions between cyanobacteria, sympatric algae and copepods are studied. The results suggest that nodularin is likely involved in allelopathic interactions, but it is not an inducible defense against grazers. Furthermore, the results of Papers IV & V, indicate that natural assemblages of N. spumigena and Anabaena spp. may support copepod reproduction and that total diazotrophic filamentous cyanobacteria appear to provide a beneficial feeding environment for the feeding stages of copepod nauplii, most probably by stimulating the microbial communities that nauplii feed upon. Since cyanobacterial blooms are projected to increase due to global climate change, the combined effects of toxic cyanobacteria, ocean acidification and global warming predicted for year 2100 are further investigated on copepods in Paper IV. Taken together, these studies indicate that filamentous diazotrophic cyanobacteria contribute to sustaining secondary productivity and have potential implications of management practices with respect to combating eutrophication, global climate change and sustaining fish feeding conditions.

Place, publisher, year, edition, pages
Stockholm: Department of Systems Ecology, Stockholm University, 2012. 56 p.
Keyword
Cyanobacteria, Calanoid copepods, Food web interactions, Harmful algae blooms, Zooplankton, Nodularin, Allelopathy, Baltic Sea, Biochemical markers, RNA-based indices, Acidification, Global Climate Change
National Category
Ecology
Research subject
Marine Ecology
Identifiers
urn:nbn:se:su:diva-81680 (URN)978-91-7447-566-1 (ISBN)
Public defence
2012-12-03, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.

Available from: 2012-11-12 Created: 2012-10-30 Last updated: 2015-04-13Bibliographically approved
2. Zooplankton growth and trophic linkages: Implications for fish feeding conditions in the Baltic Sea
Open this publication in new window or tab >>Zooplankton growth and trophic linkages: Implications for fish feeding conditions in the Baltic Sea
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this Thesis was to improve our understanding and assessment of feeding conditions for zooplanktivorous fish in the Baltic Sea.

We investigated (papers I, II) the usefulness of biochemical proxies for assessments of growth and metabolic rates in the dominant Baltic copepod Acartia bifilosa. A predictive model (paper I) for egg production rate (EPR), based on body size, RNA content, and water temperature, was established using females of different geographical origin. This model demonstrates the usefulness of RNA content as a proxy for growth in zooplankton and, together with abundance data, it could be used to evaluate fish feeding conditions. Further (paper II), using A. bifilosa exposed to a food gradient, we evaluated responses of physiological rates and other biochemical proxies for growth and established correlations between physiological and biochemical variables. EPR and ingestion rate were most significantly correlated with RNA content. As assayed variables saturated at different food concentrations, food availability may affect assessments of physiological rates using proxies. In paper III, we explored the effect of high EPR and ingestion rate on astaxanthin content in A. bifilosa. We found that the astaxanthin content decreased at high feeding rates, most likely due to decreased assimilation efficiency. This may impact the quality of zooplankton as prey.

The invasion of Cercopagis pengoi, a zooplanktivorous cladoceran, has altered the trophic linkages in the Baltic Sea food web. In paper IV, we evaluated the feeding of zooplanktivorous fish on C. pengoi and found that irrespective of size both herring and sprat feed on it, with large herring being more selective. In turn, C. pengoi feeds mainly on older copepods (paper V), which are acknowledged important in fish nutrition. These results indicate that C. pengoi may compete with fish due to the diet overlap.

Place, publisher, year, edition, pages
Stockholm: Department of System Ecology, Stockholm University, 2009. 38 p.
Keyword
AARS activity, biochemical markers, Clupea harengus, copepod physiology, food web interactions, non-indigenous species, RNA-based indices, Sprattus sprattus, stable isotopes
National Category
Ecology
Research subject
Marine Ecology
Identifiers
urn:nbn:se:su:diva-29485 (URN)978-91-7155-908-1 (ISBN)
Public defence
2009-10-14, G-salen, Arrheniuslaboratorierna, Svante Arrhenius väg 16, Stockholm, 09:30 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: In progress. Paper 3: Submitted

Available from: 2009-09-22 Created: 2009-09-01 Last updated: 2012-10-31Bibliographically approved

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