1 Laboratoire Mer Molécules Santé (MMS), Faculté des Sciences et Techniques, Université du Maine, 72085 Le Mans, France
2 Department of Marine Science, Faculty of Mathematics and Natural Sciences, Universitas Tanjungpura, Jl. Prof. Dr. H. Hadari Nawawi, Pontianak 78124, Indonesia
3 Department of Coastal Resource Management, Faculty of Fisheries and Marine Sciences, Universitas Diponegoro, Semarang, Indonesia
4 Research Center of Biotechnology and Bioinformatics, Universitas Padjadjaran, Jl. Raya Bandung Sumedang KM 21, Jatinangor 40600, Indonesia
5 Faculty of Fisheries and Marine Sciences, Universitas Padjadjaran, Jl. Raya Bandung Sumedang KM 21, Jatinangor 40600, Indonesia
Keywords: Allelopathy, aquaculture, Haslea ostrearia, marennine, microalgae
The pennate marine diatom Haslea ostrearia is known to synthesize and release a water-soluble blue-green pigment, the so-called marennine. In ponds along the French Atlantic Coast (Marennes-Oléron), marennine is responsible for the greening of oysters, a phenomenon increasing oysters’ market value. The seasonal dominance of H. ostrearia in oyster ponds is concomitant with a decrease in the diversity and abundance of phytoplankton. In a previous study1, purified marennine has been shown to reduce in a dose-dependent manner the growth of different diatoms present in the oyster ponds, Skeletonema costatum, Cylindrotheca closterium and H. crucigera, but not of Entomoneis pseudoduplex. Furthermore, light attenuation by marennine in solution in the water column can reinforce the growth inhibition1. In the line of this previous work, we investigated the possible allelopathic activity of H. ostrearia against several microalgae relevant to aquaculture: Chaetoceros calcitrans, Skeletonema costatum, Phaeodactylum tricornutum, Tetraselmis suecica and Isochrysis galbana. Allelopathic experiments were conducted by co-culturing these target species with H. ostrearia with respect to similar initial biovolumes, both in batch and in semi-continuous culture mode. Our results showed an inhibition of the growth of target microalgae due to the presence of H. ostrearia and marennine released in culture medium, which was species dependent. S. costatum, C. calcitrans, and I. galbana were significantly more sensitive, while T. suecica and P. tricornutum seemed to be more resistant. Allelopathy occurred during the exponential phase of growth, in absence of any limitation in light and nutrients. Allelopathy was also examinated under different irradiances (20, 100, and 500 μmol photons m-2 s-1) using S. costatum, one of the most susceptible species. Increasing irradiance level significantly influenced the allelophatic effect and the growth inhibition of S. costatum, as H. ostrearia released more marennine at high irradiance. The present study supports the hypothesis that marennine released into the culture medium possibly acts as an allelochemical compound, and may be the main factor explaining the dominance of H. ostrearia and loss of sensitive microalgae in oyster ponds. Furthermore, in addition to the greening phenomenon, marennine displayed biological activities, such as antioxidant properties, antiproliferative, antiviral, and antibacterial, with possibly promising applications in aquaculture. This could imply the utilisation of H. ostrearia in aquaculture (e.g. for larvae of bivalves), but using insensitive species as a mixed algal diet for animals.
[1] Pouvreau, J.-B. B., Housson, E., Tallec, L. Le, Morançais, M., Rincé, Y., Fleurence, J., & Pondaven, P. (2007). Growth inhibition of several marine diatom species induced by the shading effect and allelopathic activity of marennine, a blue-green polyphenolic pigment of the diatom Haslea ostrearia (Gaillon/Bory) Simonsen. Journal of Experimental Marine Biology and Ecology, 352(1), 212–225. https://doi.org/10.1016/j.jembe.2007.07.011
[2] Prasetiya, F. S., Safitri, I., Widowati, I., Cognie, B., Decottignies, P., Gastineau, R., Morançais, M., Windarto, E., Tremblay, R., Mouget, J. L. (2015). Does allelopathy affect co-culturing Haslea ostrearia with other microalgae relevant to aquaculture? Journal of Applied Phycology, 1–14. https://doi.org/10.1007/s10811-015-0779-y
