| Zusammenfassung: | ABSTRACT: Although eutrophication and biological invasions are recognized as important elements of global change, few studies have assessed how their synergism can affect structural and functional traits of marine ecosystems. The present study aimed to evaluate the effect of seawater nutrient enrichment on the spread of the introduced ChlorophytaCaulerpa racemosavar.cylindraceaand the interactive effects of nutritional enrichment andC. racemosainvasion on the native macroalgal assemblages of a subtidal rocky bottom. To achieve these objectives, a manipulative field experiment was carried out at 24 m depth in the northwestern Mediterranean Sea by addingC. racemosaand supplying the water column with nutrients. The following treatments were applied: non-manipulated assemblages, nutrient enrichment, addition ofC. racemosa, and both nutrient enrichment and addition ofC. racemosa. Results showed thatC. racemosaspread was enhanced by nutrient enrichment. Moreover, a significant interaction between nutritional increase andC. racemosainvasion was detected: the effects ofC. racemosainvasion on native macroalgal assemblages were amplified by nutrient enrichment. Results suggested that synergism between effects of different anthropogenic impacts can have severe consequences on the integrity of marine ecosystems.
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