Short-term and long-term exposure to combined elevated temperature and CO2 leads to differential growth, toxicity, and fatty acid profiles in the harmful dinoflagellate Karlodinium veneficum

Ocean warming and acidification may significantly alter the distribution and intensity of harmful algal blooms as well as their effects on marine food webs. Estimating such effects rely, in part, on understanding the physiological response of individual algal species to controlled laboratory simulations of climate change conditions. Here we report the physiological response of the harmful dinoflagellate Karlodinium veneficum to the combined effects of elevated temperature and CO2 (29°C/1000 ppm CO2). We first examined these effects by comparing ambient control (25°C/441 ppm CO2) and elevated conditions under short-term (~20 generations) growth. Next, we compared the short-term elevated condition to a longer-term (~200 generations) growth scenario under the same elevated temperature and CO2. Under the short-term elevated conditions, K. veneficum growth declined, cell toxicity increased, and saturated and mono-unsaturated fatty acid (FA) composition varied significantly from ambient conditions. Meanwhile, after ~ 200 generations of growth under elevated temperature and CO2, K. veneficum carbon assimilation, growth, and cell toxicity were significantly higher than the short-term elevated treatment. Further, while total saturated FA declined, essential fatty acids increased and likely represented an adaptive temporal response to long-term exposure to high temperature and CO2. Such shifts in FA profiles and cell toxicity may possibly alter K. veneficum nutritional quality as prey and its mixotrophic behavior, thereby affecting the energy and mass transfer through the marine food webs as well as bloom dynamics

Influence of Light on Prymnesium Parvum Growth, Toxicity and Mixotrophy

The haptophyte Prymnesium parvum has a worldwide distribution, with dramatic increase in blooms in the last years. P. parvum blooms are often associated with massive fish kills and great ecological impacts and economic losses as a consequence. P. parvum is a mixotrophic organism, utilizing organic dissolved substances and particles to support its photosynthetic growth. The ability of P. parvum to produce toxic compounds, and being a mixotroph, makes it capable to outcompete other algal species for essential substances. These mechanisms are mostly enhanced when environmental conditions are not optimal for P. parvum growth. Here we report results on the growth, toxicity and mixotrophy, from experiments where P. parvum cells were grown as monocultures or together with Rhodomonas salina and exposed to different light conditions (dark, 100, 700, 2000 μmol photons m-2 s-1). The results showed that P. parvum growth is affected at light intensity of 700 μmol photons m-2 s-1 and the cells were photo-lysed when exposed to irradiances above this value. An inverse relationship between cellular toxicity and light intensity was observed, i.e. lower light irradiation induced higher cell toxicity. Phagotrophy was observed in all the conditions. P. parvum reached significantly higher cell densities when growing together with R. salina than in monocultures, while cellular toxicity was significantly reduced in the mixed cultures. Furthermore the presence of prey attenuated the negative effect of the higher irradiations on P. parvum growth

Table_1_Short-term and long-term exposure to combined elevated temperature and CO2 leads to differential growth, toxicity, and fatty acid profiles in the harmful dinoflagellate Karlodinium veneficum.docx

Ocean warming and acidification may significantly alter the distribution and intensity of harmful algal blooms as well as their effects on marine food webs. Estimating such effects rely, in part, on understanding the physiological response of individual algal species to controlled laboratory simulations of climate change conditions. Here we report the physiological response of the harmful dinoflagellate Karlodinium veneficum to the combined effects of elevated temperature and CO2 (29°C/1000 ppm CO2). We first examined these effects by comparing ambient control (25°C/441 ppm CO2) and elevated conditions under short-term (~20 generations) growth. Next, we compared the short-term elevated condition to a longer-term (~200 generations) growth scenario under the same elevated temperature and CO2. Under the short-term elevated conditions, K. veneficum growth declined, cell toxicity increased, and saturated and mono-unsaturated fatty acid (FA) composition varied significantly from ambient conditions. Meanwhile, after ~ 200 generations of growth under elevated temperature and CO2, K. veneficum carbon assimilation, growth, and cell toxicity were significantly higher than the short-term elevated treatment. Further, while total saturated FA declined, essential fatty acids increased and likely represented an adaptive temporal response to long-term exposure to high temperature and CO2. Such shifts in FA profiles and cell toxicity may possibly alter K. veneficum nutritional quality as prey and its mixotrophic behavior, thereby affecting the energy and mass transfer through the marine food webs as well as bloom dynamics.</p

Alternative Methods for the Detection of Emerging Marine Toxins: Biosensors, Biochemical Assays and Cell-Based Assays

The emergence of marine toxins in water and seafood may have a considerable impact on public health. Although the tendency in Europe is to consolidate, when possible, official reference methods based on instrumental analysis, the development of alternative or complementary methods providing functional or toxicological information may provide advantages in terms of risk identification, but also low cost, simplicity, ease of use and high-throughput analysis. This article gives an overview of the immunoassays, cell-based assays, receptor-binding assays and biosensors that have been developed for the screening and quantification of emerging marine toxins: palytoxins, ciguatoxins, cyclic imines and tetrodotoxins. Their advantages and limitations are discussed, as well as their possible integration in research and monitoring programs