Effects of small‐scale turbulence on copepods: The case of Oithona davisae

Abstract

We report the effects of small-scale turbulence on the feeding rates of the marine copepod Oithona davisae. Laboratory experiments were conducted under a range of turbulence dissipation rates between 10 Ϫ4 and 10 1 cm 2 s Ϫ3 . Net enhancements of feeding were observed only at the lowest, whereas negative net effects appeared only at the highest, turbulence intensities. These results contrast with expectations from an encounter-based model for this copepod species that predicted positive feeding enhancements at all turbulence intensities. This disagreement suggests the presence of detrimental effects at moderate and high turbulence intensities, very likely driven by either a lower mechanosensor perception capability or lower capture success. In comparison to other ambush copepods, O. davisae appears much more sensitive to the presence of turbulence, which might be the result of its strict ambush behavior, whereas copepods like Acartia tonsa or Centropages typicus, which can switch into different feeding modes, appear to benefit more from turbulence. The response of O. davisae feeding to turbulence in our experiments agrees with recent field observations on changes in the vertical distribution of Oithona as a function of wind-driven turbulence events. Hence, O. davisae seems to choose those depths where small-scale turbulence favors feeding.

Hydrodynamic and tidal controls of small-scale phytoplankton patchiness

“…Saiz & Kiørboe 1995, Saiz et al 2003. In the present work, increasing turbulence decreased phytoplankton patchiness in inshore and offshore waters (see Figs.…”

First report of the planktonic copepod Oithona davisae in the northern Wadden Sea (North Sea): Evidence for recent invasion?

“…However, the other four species were all calanoid copepods. In the Atlantic and its adjacent seas, O. davisae has only been reported from the western Mediterranean and the Black Sea (Saiz et al 2003;Temnykh and Nishida 2012). Originally, O. davisae is considered to be endemic to the temperate coastal waters of East Asia (review in Temnykh and Nishida 2012).…”

Seasonal abundance and egg production rates of Oithona similis and Pseudocalanus elongatus in the northern North Sea: a first comparison of egg-ratio and incubation methods

“…This is important as Oithona, unlike many calanoids, does not create feeding currents (Paffenhöfer 1993). It is a raptorial ambush feeder in which levels of turbulence can impact feeding rates (Saiz et al 2003). While the egg-ratio method overcomes many of the concerns with incubations, it requires accurate collection of adults and eggs, their correct identifi- Table 4.…”