Journal of Applied Biological Sciences

Yazarlar: Erhan MUTLU

Konular:-

Anahtar Kelimeler:Acoustics,Mesozooplankton,Hydrography,Black Sea

Özet: Two dominant acoustical scatterers of fodder zooplankton (Calanus euxinus and Sagitta setosa) performed diel emigrational speeds depending highly on the profile of dissolved oxygen (DO) in the Black Sea: C. euxinus started accelerating upon entering the oxycline while S. setosa accelerated only after entering well-oxygenated subsurface water. The speed and their daytime depths suggest profile of the DO, sub-region classification and thickness of the oxic layer. Oxygen profile: layer where Sagitta migrate very fast is subsurface maximum oxygen and chl-a (σ θ=14.0-14.7), layer where Sagitta speed down whereas Calanus still swim fast is oxycline (σ θ =15.3-15.9), layer where Sagitta spend their daytime is a zone just above oxygen minimum zone (OMZ) (σ θ =15.9-16.0), and layer where Calanus spend their daytime is OMZ (σ θ =16.15 to 16.20). Sub-regions: If Calanus start the upward migration very fast, the region is downwelling. If they perform slow ascendance and then speed up (this means that they settle down in a layer with σ θ =16.15 to 16.20 during day), the region is upwelling. Thickness of oxic layer is depth between surfaces to a depth where Calanus are found during the daytime; Calanus and Sagitta coexist in OMZ during the cold season. Depth preference of Calanus in sub-regions must be taken into account of the thickness estimates.

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