Aggregations of the invasive ctenophore Mnemiopsis leidyi in a hypersaline environment, the Mar Menor lagoon (NW Mediterranean)

Abstract

The perennial red macroalga Gracilaria vermiculophylla (Ohmi) Papenfuss has recently been introduced to the Baltic Sea and is a potential competitor to Fucus vesiculosus, the most common native perennial alga in large parts of the Baltic Sea. Gracilaria might interfere with Fucus through direct competition for resources. In addition, Gracilaria is a favoured refuge for mesograzers, which prefer to feed on Fucus. Mesocosm-experiments were conducted over one year in the Kiel Fjord in order to test the direct and indirect effects of Gracilaria on Fucus. Fucus was incubated with Gracilaria at three different densities and grazers in high or low abundances. High densities of Gracilaria inhibited the growth of Fucus adults and also reduced the half-life-time of Fucus germlings. Associated grazers also had a negative effect on Fucus adults. Our results suggest that Gracilaria is able to influence Fucus in the Baltic Sea through direct competition for resources and by exposing it to higher grazer pressure.

First detection of Mnemiopsis leidyi (Ctenophora, Bolinopsidae) in Sardinia (S’Ena Arrubia Lagoon, Western Mediterranean): a threat for local fishery and species recruitment

“…This feature is a characteristic one, since it distinguishes M. leidyi from the closest species Bolinopsis vitrea (L. Agassiz, 1860), the oral lobes of which originate in the middle of the body (Öztürk et al, 2011). The total length of specimens collected in the S'Ena Arrubia Lagoon in autumn 2015 is in the same range as those from the Mar Menor Lagoon (Marambio et al, 2013), but smaller than those from the Black Sea, which can grow up to 180 mm TL .…”

“…Mnemiopsis leidyi is reported in the western Mediterranean mainly in coastal waters (Boero et al, 2009;Fuentes et al, 2010), but the most recent observations include transitional environments, such as lagoons (Marambio et al, 2013;Thibault et al, 2014). The presence of M. leidyi in the S'Ena Arrubia Lagoon represents the first report in Sardinia and the first report of the species in a transitional ecosystem along the Italian coasts.…”

“…From there, the species reached the Eastern Mediterranean Sea, being reported in the Aegean Sea (1990), in coasts of Turkey (Mersin Bay, 1992), and in Syria (1993). Since the 2000s, the species was detected in the central and western Mediterranean: Adriatic Sea (Marambio et al, 2013). In Italy, the species was recorded in Ligurian, Tyrrhenian and Ionian seas (Boero et al, 2009).…”

“…The species finds suitable conditions in eutrophic waters, and it tolerates wide ranges of salinity, temperature and dissolved oxygen (Purcell et al, 2001;Marambio et al, 2013). Additionally, it actively preys on First record of Mnemiopsis leidyi (Ctenophora, Bolinopsidae) in Sardinia (S'Ena Arrubia Lagoon, Western Mediterranean): a threat to local fishery?…”

“…Thus, all the reports of this species in marine or transitional systems such as ponds, lagoons, estuaries and gulfs, have to be taken into account for the related ecological implications and the potential effects on fisheries and tourism (Marambio et al, 2013(Marambio et al, , 2014Thibault et al, 2014).…”