Jessica Griffin, Gihong Park and Hans G. Dam Department of Marine Sciences, University of Connecticut, Avery Point

1. INTRODUCTION

Effects of Nutrients and Alarm Cues in Toxin Production of MarineDinoflagellate Alexandrium fundyense

2. MATERIALS & METHODS• A. fundyense were placed in 500 mL bottles of either nutrient

replete F/2 or nutrient limited filtered seawater (FSW)• Toxin analysis done by HPLC• Concentration of A. fundyense cells: 300 cells/mL• Experiment occurred during exponential phase of high toxin and

low toxin cells• Crushed cells added had equivalent carbon content for each bottle

* Acknowledgement: Research supported by Sea Grant

3. RESULTS

Experiment was run on plankton wheel to simulate motion that copepods and algae experience in the ocean.

Alexandrium fundyense cells. Photo by Don Anderson, Woods Hole Oceanographic Institute

As an inducible defense, Red tide algae Alexandrium fundyense produces a suite of neurotoxins, such as paralytic shellfish toxin (PST). These algae can increase production of toxin in response to the activity of grazers and to other environmental factors. A. fundyense co-occurs with grazer copepod Acartia hudsonica. Biotic cues that increase toxin production must be specific and effective to alerting the prey to the predator’s presence. These factors include conspecific alga-alga signals, kairomones released by the grazer, and feeding cues. Abiotic factors, also influence the toxin production. More toxins tends to be produced in nitrogen rich environments, since many of the toxins produced are composed of nitrogen compounds.

Hypotheses• Toxin production is induced in response to conspecific alarms,

but not induced in response to alarms of distantly related algae• Ammonium excreted by grazers may induce toxin production• Direct grazing causes a larger increase in toxin production than

any other alarm cue

Conclusions A.fundyense may have the ability to sense alarm cues from unrelated algal species,

like tetraselmis spp. or T. weissflogii Direct grazing causes a much larger increase in toxin production than any other alarm

cue A. fundyense may have a differing response to urea presence based on whether it is

present in nutrient replete F2 or nutrient limited FSW

• Significantly more toxin was produced when A. fundyense are exposed to direct grazing than exposure to any other alarm cue

• This is true when A. fundyense are tested in either nutrient replete F2 or nutrient limited filtered sea water (FSW)

• Approximately 46% more toxin is produced when A. fundyense is exposed to crushed T. weissflogii than when exposed to other biotic alarm cues in F2 (excluding direct grazing)

• Approximatley 31% more toxin is produced when A. fundyense is exposed to crushed tetraselmis spp. and T. weissfloggi than when exposed to biotic alarm cues in FSW (excluding direct grazing)

• Approximately 45% less toxin is produced when A. fundyense is exposed to urea than when exposed to other abiotic alarm cues in F2

• Approximately 50% more toxin is produced when A. fundyense is exposed to NH4+ without K media and urea than when exposed to other abiotic alarm cues in FSW

Total induced toxins (pM/cell): F2-Biotic

Total induced toxins (pM/cell): FSW Biotic

Total induced toxins (pM/cell): F2- Abiotic

Total induced toxins (pM/cell): FSW-Abiotic

Total induced toxins (pM/cell): F2 overall

Total induced toxins (pM/cell): FSW overall