Effect of fully characterized unsteady flow on population growth of the dinoflagellate Lingulodinium polyedrum

Abstract

Dinoflagellate population growth is inhibited by fluid motion, which is typically characterized by some average flow property, regardless if the flow is steady or unsteady. This study compares the effect of fully characterized steady and unsteady flow on net population growth of the red tide dinoflagellate Lingulodinium polyedrum. The unsteady flow fields were generated using oscillatory laminar Couette flow and characterized analytically to provide complete knowledge of the fluid shear exposure over space and time throughout the chamber. Experimental conditions were selected so all cells experienced a similar shear exposure regardless of their position within the chamber. Unsteady flow with maximum shears of 6.4 s 21 and 6.7 s 21 and an average absolute shear of 4 s 21 , comparable with levels found at the ocean surface on a windy day, resulted in higher levels of growth inhibition than for steady Couette flow with shears of 4 and 8 s 21 . Over the parameter space studied, growth inhibition increased with increasing treatment duration (5-120 min) but was insensitive to oscillation period (60-600 s) or whether the unsteady flow changed in direction. These results indicate that over the parameter space studied, unsteady flow is more inhibitory to net growth than steady flow, for the same average flow conditions, and demonstrate that flow characterization on the basis only of average flow properties is inadequate for comparing population growth in unsteady and steady flows.

Contrasting effects of high‐intensity photosynthetically active radiation on two bloom‐forming dinoflagellates

“…, Maldonado and Latz , Latz et al. ). However, in regards to light, synthesis and release of DMSP did not appear to play a role in the short‐term stress response of the dinoflagellates in our study, except as mediated by cell lysis.…”

“…We did not see increased dissolved DMSP in association with A. fundyense handling; the signal might have been too small to permit detection, or eliminated by rapid bacterial degradation. Many large, thecate dinoflagellates are known to be sensitive to shear stress, which can inhibit population growth, stimulate bioluminescence, and increase cell toxin content (Juhl et al 2001, Maldonado and Latz 2007, Latz et al 2009). However, in regards to light, synthesis and release of DMSP did not appear to play a role in the short-term stress response of the dinoflagellates in our study, except as mediated by cell lysis.…”

Species-specific effects of fluid shear on grazing by sea urchin larvae: comparison of experimental results with encounter-model predictions

“…The flow chambers used in this study were the same previously used in growth studies (Juhl et al 2001, Latz et al 2009). They were constructed of clear acrylic with the following dimensions: inner radius (r i ) = 20.5 mm; outer radius (r o ) = 24 mm; height of fluid (h) = 200 mm; fluid volume in gap = 265 ml.…”

“…The bottom end cap of the outer cylinder was mounted to a pulley system with plastic chain to couple 4 replicate chambers to a Silvermax servomotor (QuickSilver Controls). Motor speed was controlled by custom software on a personal computer (Latz et al 2009). The mean shear rate, G, within the gap is calculated as:…”