Abstract
The ichthyotoxic dinoflagellate Karlodinium veneficum has a worldwide distribution and produces highly potent lytic toxins (karlotoxins) that have been associated with massive fish kill events in coastal environments. The capacity of K. veneficum to gain energy from photosynthesis as well as phagotrophy enables cellular maintenance, growth and dispersal under a broad range of environmental conditions. Coastal ecosystems are highly dynamic in light of the prevailing physicochemical conditions, such as seawater carbonate speciation (CO2, HCO3−, and CO32−) and pH. Here, we monitored the growth rate and ichthyotoxicity of K. veneficum in response to a seawater pH gradient. K. veneficum exhibited a significant linear reduction in growth rate with elevated seawater acidity [pH(totalscale) from 8.05 to 7.50]. Ichthyotoxicity was assessed by exposing fish gill cells to K. veneficum extracts and subsequent quantification of gill cell viability via resorufin fluorescence. Extracts of K. veneficum indicated increased toxicity when derived from elevated pH treatments. The variation in growth rate and toxin production per cell in regard to seawater pH implies that (1) future alteration of seawater carbonate speciation, due to anthropogenic ocean acidification, may negatively influence physiological performance and ecosystem interactions of K. veneficum and (2) elevated seawater pH values (>8.0) represent favorable conditions for K. veneficum growth and toxicity. This suggests that prey of K. veneficum may be exposed to increased karlotoxin concentrations at conditions when nutrients are scarce and seawater pH has been elevated due to high photosynthetic activity from prior autotrophic phytoplankton blooms.
Highlights
The accumulation of anthropogenic carbon dioxide in the atmosphere and its concomitant absorption by the ocean surface causes distinct chemical changes, known as ocean acidification
The experimental protocol applied to alter the seawater carbonate chemistry mimics the process of ocean acidification and resulted in elevated total dissolved inorganic carbon concentrations at constant total alkalinity (Table 1)
Growth rates of K. veneficum were positively correlated with seawater pH (Figure 1A), resulting in a maximum observed growth rate of 0.47 days−1 at a pH of 8.03
Summary
The accumulation of anthropogenic carbon dioxide in the atmosphere and its concomitant absorption by the ocean surface causes distinct chemical changes, known as ocean acidification (reduction of pH and increase of CO2). Nutrient availability and other environmental drivers, such as seawater carbonate chemistry, have the potential to alter growth and cellular toxicity of K. veneficum (Fu et al, 2010). We present controlled laboratory experiments investigating the autotrophic growth and ichthyotoxicity of one K. veneficum strain in response to an extended seawater pH gradient.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
