Haemolytic activity of live Phaeocystis pouchetii during mesocosm blooms

Abstract

Chemical defence is a potential mechanism contributing to the success of Phaeocystis species that repeatedly dominate the phytoplankton in coastal areas. Species within the genus Phaeocystis have long been suspected of imposing negative eVects on co-occurring organisms. Recently a number of toxins have been extracted and identiWed from Phaeocystis samples, but it is not clear if they do enhance the competitive advantage of Phaeocystis species.In the present study the cytotoxic impact of live Phaeocystis pouchetii to human blood cells in close proximity, regardless of the nature of the responsible mechanism, was quantiWed using a bioassay. Haemolytic activity was measured during blooms of P. pouchetii in mesocosms. These environments were chosen to mimic natural conditions including chemically mediated interactions that could trigger defensive and/or allelopathic responses of Phaeocystis.Haemolytic activity correlated with P. pouchetii numbers and was absent during the preceding diatom bloom. Samples containing live P. pouchetii cells showed the highest activity, while Wltered sea water and cell extracts were less haemolytic or without eVect. Dose-response curves were linear up to 70% lysis, and haemolysis in samples containing live P. pouchetii cells reached EC 50 values comparable to known toxic prymnesiophytes (1.9 * 10 7 cells l ¡1 ). Haemolytic activity was enhanced by increased temperature and light. The results indicate that unprotected and thus presumably vulnerable cells present in a P. pouchetii bloom may lyse within days.

Harmful algal blooms of allelopathic microalgal species: The role of eutrophication

“…Exposure from UV light at 255 nm and visible light between 400 and <520 nm completely inactivated extracellular ichthyotoxins from P. parvum within 90 min (Parnas et al, 1962). Another haptophyte, Phaeocystis pouchetii, enhanced haemolytic activity when incubated at higher light intensities (van Rijssel et al, 2007), thus showing a positive stimulation from light.…”

“…As an example, the haemolytic activity of P. pouchetii increased when the temperature was increased from 4 8C to 15 8C (van Rijssel et al, 2007). In contrast, in culture experiments there was no difference in allelopathic effects of the potentially toxic dinoflagellate, Alexandrium tamarense on dinoflagellates S. trochoidea or H. triquetra at 14 8C versus 20 8C (Fistarol et al, 2004a).…”

“…Although it is has been shown that degradation of some allelochemicals when exposed to high light intensities and/or UV radiation can be on the order of hours to 1 day van Rijssel et al, 2007), some evidence exists that degradation by bacteria do occur. Simonsen and Moestrup (1997) found that C. polylepis haemolytic compounds were degraded in 40 h when in darkness, and in 12 h in light, suggesting that although not as efficient as light, the role of bacteria cannot be disregarded in this process.…”

Temperature effects on growth, colony development and carbon partitioning in three Phaeocystis species

“…Dense blooms have also been observed off the coasts of southeast China , Vietnam (Tang et al 2004), and Norway (Larsen et al 2004). The clones isolated from Chinese and Norwegian waters have hemolytic properties as well (Shen et al 2004, van Rijssel et al 2007. Different Phaeocystis species occur over different temperature ranges in the ocean (Schoemann et al 2005).…”

The role of nitrogen on the growth and colony development ofPhaeocystis globosa(Prymnesiophyceae)

“…Dense blooms have been observed off the coasts of the North Sea (Lancelot et al, 1987), North Atlantic (Gieskes et al, 2007), southeast China , Vietnam (Tang et al, 2004) and Norway (Larsen et al, 2004). Clones isolated from Chinese and Norwegian waters have been shown to have haemolytic properties van Rijssel et al, 2007). All of the locations listed above are considered to be eutrophic, due to riverine and anthropogenic nutrient enrichment (Lancelot et al, 1987;Zhang et al, 2000;Cade´e & Hegeman, 2002;Thanh et al, 2004).…”