Response of Gonyaulax tamarensis to the presence of a pycnocline in an artificial water column |
| |
Authors: | Rasmussen Jeff; Richardson Katherine |
| |
Institution: | Danish Institute for Fisheries and Marine Research, Charlottenlund Castle DK-2920 Charlottenlund, Denmark |
| |
Abstract: | In nature, large concentrations of the toxic bloom-forming dinoflagellate,Gonyaulax tamarensis, are frequently observed in the vicinityof the pycnocline. In the absence of a pycnocline the organismis usually recorded near the surface, where light levels aremore advantageous for photosynthesis. In this paper we examinethe swimming behaviour of G.tamarensis when exposed to varyingdegrees of stratification and investigate whether the maintenanceof a subsurface (pycnocline) population is the result of retentionof the algae by a physical barrier or active accumulation ofthe organisms at a density interface. The study indicates thatG.tamarensis cells presented with a halocline of S<{smalltilde}67 (occurring over a few centimeters) cross thissalinity barrier and accumulate at the highest available photonflux density ({small tilde}100 µmol m2 s1).Cells exposed to a gradient of S>{small tilde}7 remain atthe halocline (pfd={small tilde}40 µmol m2 s1).However, when light above the pycnocline is attenuated by theaddition of food colour to the medium, the cells cross a haloclineof S=10 and accumulate at the highest available photon fluxdensity. In the absence of added nutrients (inorganic N andP) the organism fails to exhibit a phototactic response. Thus,the presence of a strong halocline does not represent an inpenetrablephysical barrier for G.tamarensis and the development of pycnoclinepopulations of this organism is a function of density, lightand nutrient climate. |
| |
Keywords: | |
本文献已被 Oxford 等数据库收录! |
|