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MEPS 608:13-32 (2019)  -  DOI: https://doi.org/10.3354/meps12814

Re-oligotrophication trajectories of macrophyte assemblages in Mediterranean coastal lagoons based on 17-year time-series

Ines Le Fur1,*, Rutger De Wit2, Martin Plus3, Jocelyne Oheix1, Valérie Derolez1, Monique Simier1, Nathalie Malet4, Vincent Ouisse1

1MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, CS 30171, 34203 Sète, France
2MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, CC093, 34095 Montpellier, France
3Ifremer, Laboratoire d’écologie pélagique (DYNECO-PELAGOS), Centre Bretagne, ZI Pointe du Diable, CS 10070, 29280 Plouzané, France
4Ifremer, Laboratoire Environnement Ressources Provence-Azur-Corse, station de Corse, Immeuble Agostini, Z.I. Furiani, 20600, Bastia, France
*Corresponding author:

ABSTRACT: Since the mid-20th century, Mediterranean lagoons have been affected by eutrophication, leading to significant changes in primary producers. In the early 2000s, management actions have been implemented to reduce nutrient inputs with the aim to achieve a good ecological status as requested by the EU water framework directive. As a result of these actions, a sharp decline in nutrient loads has been recorded in several lagoons leading to an oligotrophication of the water column. The analyses of a long-term data set (1998-2015) of 21 polyhaline and euhaline lagoons with contrasting trophic status allowed us to infer a general scheme for the changes in macrophyte assemblages during the oligotrophication process. Placing hypertrophic and oligotrophic conditions end to end, we inferred that the general pattern for the re-oligotrophication trajectory in Mediterranean coastal lagoons is described by the following sequence, with regime shifts between each state: (1) bare non-vegetated sediments, phytoplankton-dominated state; (2) opportunistic macroalgae; (3) seagrass and perennial macroalgae dominated state. However, we did not observe the latter regime shift for the most eutrophicated lagoons, which, so far, remained stuck in the opportunistic macroalgae state. So far, the shift from dominance of opportunistic macroalgae to a system dominated by seagrasses was only observed in a single lagoon where seagrasses had never completely disappeared, which possibly relates to resilience. More generally, the conditions favoring regime shifts from opportunistic macroalgae to seagrasses are still poorly understood. In conclusion, we describe a generic pattern for re-oligotrophication of Mediterranean coastal lagoons, although a full recovery from highly eutrophied to oligotrophic conditions may require more than a decade and may include conditions that remain so far poorly recognized.


KEY WORDS: Submerged aquatic vegetation · Recovery · Nutrient reduction · Restoration · Long-term data series · Resilience · Regime shift · Coastal lagoon


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Cite this article as: Le Fur I, De Wit R, Plus M, Oheix J and others (2019) Re-oligotrophication trajectories of macrophyte assemblages in Mediterranean coastal lagoons based on 17-year time-series. Mar Ecol Prog Ser 608:13-32. https://doi.org/10.3354/meps12814

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