Effects of the toxic haptophyte Prymnesium parvum on the survival and feeding of a ciliate: the influence of different nutrient conditions

Abstract

We studied the growth and feeding response of the ciliate Euplotes affinis when exposed to algal cultures of Prymnesium parvum and Rhodomonas cf. baltica as monocultures or as mixtures. Cultures of P. parvum grown under nutrient-limited (N or P) or nutrient-sufficient conditions were tested for toxicity against E. affinis. Ciliates grew well when fed R. cf. baltica, but avoided grazing on monocultures of P. parvum, regardless of algal concentration. Increasing abundances of P. parvum decreased survival of the ciliate, even if supplied as a mixture together with high concentrations of R. cf. baltica as an alternative prey. This implies that P. parvum produces substances that were fatal to the ciliate when released to the medium. The lethal effect of P. parvum was dependent on the physiological status of the cells, with the highest toxicity in nutrient-stressed cultures. Our results suggest that toxin production in P. parvum may be a chemical defense to repel predators.

The Global, Complex Phenomena of Harmful Algal Blooms

“…For example, it has long been argued that production of allelopathic exudates allows some harmful species to outcompete co-occurring phytoplankton (e.g., Smayda, 1998;Granéli and Johansson, 2003). Some species may even use cyst formation as a survival strategy against strong allelochemicals produced by another HAB species (Fistarol et al, 2004).…”

Pseudo-nitzschia physiological ecology, phylogeny, toxicity, monitoring and impacts on ecosystem health

“…inhibitory effects on the growth of competitors caused by production of certain allelopathic substances, are known from prymnesiophytes and dinoflagellates and this may contribute to their ability to form monospecific blooms (Arzul et al, 1993;Grané li and Johansson, 2003). Pseudo-nitzschia species are also known to form dense blooms (10 6 to 10 8 cells l À1 ), which are often more or less monospecific, accounting for up to 99% of the total phytoplankton and sometimes lasting for a long time, up to two months (e.g.…”

Haemolytic activity and allelopathy of the haptophyte Prymnesium parvum in nutrient-limited and balanced growth conditions

“…P. parvum is allelopathic to co-existing algae by excreting toxins into the water , Granéli & Johansson 2003b, and it may immobilise its prey before utilising it . In addition, it may use its toxins to damage or reduce the growth of its grazers, for example dinoflagellates, ciliates and copepods (Nejstgaard et al 1995, Nejstgaard & Solberg 1996, Koski et al 1999, Granéli & Johansson 2003a, Rosetta & McManus 2003, Tillmann 2003. Allelopathy is important in aquatic interactions as it can affect algal succession (Keating 1977(Keating , 1978.…”