科研之友
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摘要
Populations of the toxic dinoflagellate Karenia brevis that remain near the benthos in deep shelf water in the Gulf of Mexico could be the source for toxic bloom occurrences near shore. A biophysical dynamic simulation model and migrating drifters were used to assess whether such 'seed populations' could persist in nature. The vertical migration responses of plankton to an exclusively benthic nutrient source and light limitation would result in near-benthic behavioral trapping of a slowly growing population in conditions found on the West Florida Shelf (WFS). The model indicated that for a 50 m deep bottom, a 2-m-thick layer of >= 2 mu mol NO3-/NO2- fluxing from the benthos was the minimum needed to permit growth for dark-adapted K. brevis in an oligotrophic water column. Growth rates depended more on the duration of exposure to nutrients than on concentration; a 1-m-thick nutrient layer sustained minimum growth levels independently of the nutrient distribution at depths <= 40 m. Field experiments using Autonomous Behaving Lagrangian Explorer drifters (ABLEs) that exhibited biomimetic vertical migration responses to the external environment demonstrated a benthically-oriented movement pattern in response to natural light and cues correlated with elevated near-benthic nutrients. Average measurements of nutrients and light from the bottom 2 m of the water column in a potential bloom-forming region of the WFS were higher than the model-generated requirements for growth, suggesting that coastal nutrient distributions could support a benthic population offshore. Under upwelling conditions, such populations could be advected inshore to frontal convergence zones and form toxic 'red tide' blooms.
- 出版日期2015-6-8
