Announcing the Final Examination of Victoria Roberts Devillier for the degree of Doctor of Philosophy in Biology
In this work, we investigated the use of a modified kaolinite clay (Modified Clay II aka MC II) as a potential option to control harmful algal blooms of Karenia brevis in Florida. Clay-based compounds are used globally for water treatment and suppression of marine blooms, and may be a promising option to treat K. brevis blooms, given the low cost, ease of application, and negligible impacts of this technique. As clays are developed and investigated for use on K. brevis, concerns and challenges must be addressed regarding environmental safety, such as effects on water quality, fate of toxins, and potential impacts to non-target organisms. In a series of experiments, we evaluated removal efficiency, water chemistry dynamics, and physiological responses in blue crab (Callinectes sapidus), sea urchin (Lytechinus variegatus), and hard clam (Mercenaria campechiensis). First, we conducted an experiment with blue crabs in 20 L aquarium tanks (N = 48), exposing the animals to cultured K. brevis (1 x 106 cells L-1) and MC II (0.5 g L-1) over 192 hours. In our second experiment, K. brevis (1x106 cells L-1) and MC II (0.2 g L-1) were applied to 1,400 L mesocosms (N = 9) containing blue crabs, sea urchins, and hard clams, which were observed over 96 hours. In our final experiment, we again examined K. brevis (1x106 cells L-1) and MC II (0.2 g L-1) with the same model species in 1,400 L mesocosms (N = 12) over 72 hours. Our results were congruent across our three experiments. Treatment with MC II significantly reduced cell concentrations but did not reduce toxin concentrations in the water column. We found no notable impacts of clay treatment to reflexes, respiration rates, or internal toxin content for either of our three species. Among other chemical effects, we found clay significantly reduced dissolved phosphorus from the water column, indicating a potential for this treatment to improve water quality in scenarios where nutrient pollution is a concern. Use of clay-based compounds may relieve the damaging effects of K. brevis blooms by reducing algal cells and toxins and thereby preventing mortalities that would otherwise occur were blooms allowed to persist. We therefore recommend that clays, including MC II, be considered for additional laboratory and field tests, with the goal of obtaining further information on potential ecological impacts so that managers and researchers can make informed decisions on the use of bloom control technologies in Florida waters.
Committee in Charge:
Dr. Kristy Lewis (Chair)
Dr. Lisa Chambers
Dr. Chase Mason
Dr. Emily Hall (External Committee Member)
Read More