Role of planktonic bacteria in biodegradation of fish-exuded kairomone in laboratory bioassays of diel vertical migration

Beklioglu, M
Gözen, Ayşe Gül
Zorlu, P
Ay-Zog, D
Daphnia, freshwater crustaceans that graze algae, often rely on predatory chemical cues termed kairomones as signals for predator-avoidance. Using laboratory bioassays, we studied how planktonic bacteria may modify kairomone activity. We measured the amplitude of diel vertical migration (DVM) of Daphnia pulex DE GEER among treatments with different amounts of bacteria. We used temperature incubation to increase bacterial densities and filtration to reduce abundance. Daphnids exposed to fish cue (F) and filtrate of fish cue (FF) (i. e. 3.0 fold decrease in the planktonic bacteria) exhibited a strong DVM response. In addition, the strength of the response remained the same for both treatments. However, daphnids exposed to an incubated fish cue (IF), which had higher bacterial densities, showed similar migration to daphnids in the control treatment. This IF treatment showed a 3-fold enrichment of bacteria. Besides observing a gradient in DVM response with bacterial density, we also found that DVM response varied seasonally in our experiments. DVM response to fish cue developed quickly in the experiments carried out in March and May compared to a delayed response that we observed in a similar experiment in January. A seasonal shift also occurred in the population sizes of cultivable planktonic bacteria. Responsiveness of D. pulex to predator cues may vary seasonally, possibly due to higher vulnerability during seasons with high fish production. Kairomone concentrations may also fluctuate due to varied release or degradation rates. Our results suggest that the in-situ, tight coupling between production and degradation of kairomone appears to be the cause of DVM response for daphnids during summer.


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A one-dimensional coupled physical and intermediate-complexity biochemical model comprising large and small phytoplankton and zooplankton groups, particulate organic nitrogen, ammonium and nitrate was developed to study the physical-biogeochemical interactions and parameters that control plankton production in the Alboran and Balearic Sea ecosystems. The model findings suggest that pelagic fish predation and resource availability through lateral and vertical nutrient inputs jointly characterize the plankton...
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Diel vertical migration (DVM) is a complex and dynamic behaviour against predation because the reaction of migrating organisms to light intensity plays a primary role, but is modified by other factors. In the relatively shallow but thermally stratified Lake Eyrnir, Daphnia pulex de Geers utilized vertical refugia afforded by the hypolimnion during both day and night. Differences in general vulnerability to fish predation determined the differences in their mean residence depths (MRDs) of different populatio...
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Beklioğlu, Meryem; Tuzun, I (Springer Science and Business Media LLC, 2003-01-01)
Nutrient loading in lakes is recognized as a serious threat to water quality. Over 25 years of raw sewage effluent discharge shifted Lake Eymir from a state dominated by submerged plants to a turbid water state. Successful effluent diversion undertaken in 1995 achieved 88% and 95% reductions in the areal loading of total phosphorus (TP) and dissolved inorganic nitrogen (DIN), respectively. Furthermore, the reduced load of TP was very close to the suggested threshold areal load (0.6 g m(-2) yr(-1)) to attain...
Long-term changes in littoral fish community structure and resilience of total catch to re-oligotrophication in a large, peri-alpine European lake
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The littoral zone of lakes is used as spawning, shelter, or feeding habitat for many fish species and hence is of key importance for overall lake functioning. Despite this, hardly any studies exist examining the long-term dynamics and response of the littoral fish community, composed mostly of juvenile fish, to environmental change. Here, we study the response of total catch per unit effort (CPUE) and individual species CPUE of such a community to 17 years of oligotrophication and examine whether the specie...
Citation Formats
M. Beklioglu, A. G. Gözen, P. Zorlu, and D. Ay-Zog, “Role of planktonic bacteria in biodegradation of fish-exuded kairomone in laboratory bioassays of diel vertical migration,” ARCHIV FUR HYDROBIOLOGIE, pp. 89–104, 2006, Accessed: 00, 2020. [Online]. Available: