Meeting Abstract
The movement of plankton is often dictated by local flow patterns, particularly during storms and in environments with strong flows. Reefs, macrophyte beds, and other immersed structures can provide shelter against washout and drastically alter the distributions of plankton as these structures alter and slow the flows through them. Advection diffusion and agent-based models are often used to describe the movement of plankton within marine and freshwater environments and across multiple scales. Experimental validation of such models of plankton movement within complex flow environments is challenging, however. In this study, we experimentally investigate plankton dispersion through various, rigid macrophyte models in complex flow environment at the scale of tens of centimeters. We use Artemia spp., or brine shrimp, as a model organism given their availability and ease of culturing. Experiments were conducted within a flow tank with simplified physical models of macrophytes. These simplified models were 3D-printed arrays of cylinders of varying heights and densities. Artemia nauplii were injected within these arrays and their distributions over time were recorded with multiple video recorders. The detailed three-dimensional flow fields were quantified using computational fluid dynamics and validated experimentally with 2D particle image velocimetry. Complementary agent-based simulations of the movement of brine shrimp through these structures were also performed. The results show that increasing density and the height of the macrophyte bed drastically increases the average time it takes the plankton to be swept downstream. It was also observed that some brine shrimp can entirely avoid being swept away in the presence of macrophyte model. This phenomenon was observed only in the close vicinity after the model and only at the bottom of the flow tank, where the effect of the boundary layer is significant. Moreover, more brine shrimp stayed attached with the increased density and height and the zone of attachment extended, as well. However, no shrimps could avoid being swept away in the model. Agent-based models of brine shrimp that move with random motion and are advected with the flow show similar trends.
