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Aquatic Microbial Ecology

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AME 83:131-146 (2019)  -  DOI:

Phytoplankton strategies to exploit nutrients in coastal lagoons with different eutrophication status during re-oligotrophication

A. Leruste1,*, F. Guilhaumon1, R. De Wit1, N. Malet2, Y. Collos1,†, B. Bec1

1MARine Biodiversity Exploitation and Conservation MARBEC, Université de Montpellier, IRD, Ifremer, CNRS. Bât. 24, Place Eugène Bataillon, 34095 Montpellier cedex 5, France
2Ifremer, LEPAC-Corse, ZI Furiani, Im Agostini, 20600 Bastia, France
*Corresponding author:

ABSTRACT: We studied a mesotrophic and a hypertrophic Mediterranean coastal lagoon, both of which had been simultaneously subjected to a nutrient input reduction for 9 yr. We compared these 2 lagoons to an oligotrophic coastal lagoon. Using bioassays comprising 24 h incubations with added phosphorus and/or ammonium, we investigated the response of the phytoplankton communities to nutrient enrichment during summer in terms of biomass, size class structure, abundance and growth. For nitrogen and phosphorus, we identified which nutrient limited phytoplankton growth, and what strategies of nutrient exploitation the communities adopted to cope with these limitations. Ultraphytoplankton dominated the 3 communities, but it differed in composition among the lagoons. Green algae dominated in the hypertrophic lagoon, whereas the mesotrophic lagoon presented a higher diversity of phytoplankton groups. Picocyanobacteria and small diatoms were the most abundant groups in the oligotrophic lagoon, although they accounted for less biomass than green algae. The communities of the mesotrophic and the hypertrophic lagoons strongly responded to the nutrient pulse, showing that the re-oligotrophication trajectories of these lagoons were still very vulnerable to occasional eutrophication events. On the other hand, the oligotrophic lagoon marginally responded to the enrichment, indicating its adaptation to nutrient-depleted conditions. We observed a shift along the eutrophication gradient, from a co-limitation by N and P in the oligotrophic and the mesotrophic lagoons to a single and strong N limitation in the hypertrophic lagoon. Each community demonstrated specific use of internal, external or recycled nutrient pools under experimentally induced limitation.

KEY WORDS: Growth rate · Nutrient limitation · Dilution experiment · HPLC

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Cite this article as: Leruste A, Guilhaumon F, De Wit R, Malet N, Collos Y, Bec B (2019) Phytoplankton strategies to exploit nutrients in coastal lagoons with different eutrophication status during re-oligotrophication. Aquat Microb Ecol 83:131-146.

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