Meeting Abstract
P2.115 Monday, Jan. 5 Seeding red tides: behavioral experiments with Plankton Mimics WATERS-LINDQVIST, L.G.*; WOLCOTT, T.G.; KAMYKOWSKI, D.; NC State Univ., Raleigh; NC State Univ, Raleigh; NC State Univ, Raleigh lindagwen@gmail.com
How are toxic red tides seeded on the west Florida coast? The dinoflagellate, Karenia brevis, does not form resting cysts. One hypothesis is that "seed" populations persist in deep water offshore, are advected onshore by upwelling, and bloom when they have an ample supply of both light and nutrients. Robot "Plankon Mimics" are testing whether a simple, biologically rational behavioral model could keep such a seed population of motile algae deep, and alive, under realistic field conditions. The model, derived from lab studies and field distributions, uses a clock-driven diel vertical migration (DVM,) but modulated by in-situ conditions via physiology. The Mimics swim upward faster when "hungry" for photosynthate (C) and downward faster when "hungry" for nutrients (N.) The vertical distribution of nutrients near shore, especially during upwelling, may have several peaks. Offshore it is very different. Most of the water column is oligotrophic, and cells encounter significant N only at their DVMs low point when they are in the near-bottom layer, into which N diffuses from the sediment. In field experiments, Mimics under "nearshore" conditions exhibited a DVM with the water surface as its upper bound, while Mimics under "oligotrophic + near-bottom nutrients" conditions returned to the bottom on each diel cycle. Mimics in nearshore conditions filled their C and N pools and "divided" in 3-4d (typical of nutrient-replete cultures) while under oligotrophic conditions about half of them "died" after 10 days without acquiring enough C and N to divide. This indicates that physiological modulation of DVM could allow deep offshore populations to persist, albeit with very low rates of increase, at depths from which they could be moved inshore during upwelling and seed a bloom.
