Amphistegina lobifera, a large symbiont-bearing benthic foraminifer native to the Red Sea, entered the Eastern Mediterranean through the Suez Canal, an artificial waterway opened in 1869. The species has already successfully colonized the Levantine basin and more recently has been reported from the Sicily Channel (Central Mediterranean) and the southern Adriatic Sea. However, very little is known about the current distribution and establishment status of this alien species as well as its possible impact on native benthic communities. This PhD project addresses three specific research questions corresponding to three main aims: Aim 1) evaluating the current distribution and establishment status of A. lobifera and other cryptogenic benthic foraminifera in the Sicily Channel; Aim 2) reconstructing the invasion dynamics of A. lobifera and A. lessonii in the Maltese Islands; Aim 3) assessing the potential impact of the highly invasive A. lobifera on native foraminiferal assemblages from the Maltese Islands, Southern Sicily and Southeastern Sicily. This PhD project is a pioneer study that applies an unprecedented multidisciplinary approach, which combines for the first time methods commonly used in Marine Ecology with those used in Micropaleontology for the investigation of marine bioinvasions. In order to address Aim 1, the current distribution, range expansion and establishment status of the target species and other cryptogenic foraminifera were investigated in sediment and algal samples from four different areas of the Sicily Channel (Maltese Islands, Southern Sicily, Pantelleria and Favignana islands) and one area of the Western Mediterranean (Northwestern Sicily). Several new records of both amphisteginid species were achieved: A. lobifera was documented for the first time in Southern Sicily and in Pantelleria and Favignana islands; A. lessonii was recorded for the first time in the Maltese archipelago and Pantelleria and Favignana islands. The results also allowed for updating the species distribution model for A. lobifera, which is expected to colonize wide areas in the Central and Western Mediterranean and in the Adriatic Sea, in the next 50 and 100 years, favoured by the ongoing sea warming. In order to address Aim 2, the invasion dynamics of both A. lobifera and A. lessonii were reconstructed in one selected locality of Malta, also relating the recorded abundance patterns with the temporal trends of sea surface temperature (SST) measured in the area since 1950. To this purpose, a ‘micropaleontological approach’ was applied through the analysis of the benthic foraminiferal content along two sediment cores chronologically constrained through radiometric dating. Results showed that the current invasion of both species in Malta started at the beginning of the 1940s but they remained undetected for about 60 years. Data also evidenced a clear positive correlation between the abundance increase of Amphistegina spp. and the SST increase recorded in the Central Mediterranean. Moreover, this study allowed to document an early invasion of Amphistegina spp. in Malta at the beginning of the twentieth century, which failed due to the tsunami wave generated by the 1908 Messina earthquake. Finally, in order to address Aim 3, the potential impact of the highly invasive A. lobifera on native benthic foraminiferal assemblages in the Sicily Channel (Central Mediterranean) was evaluated. To this purpose, a nested sampling design was applied through the comparison of benthic foraminiferal community structure across three areas that, through the results of Aim 1, are known to be at advanced, medium and early stages of invasion. Collected data documented a severe loss of biodiversity in the Maltese Islands, where A. lobifera was highly abundant. On the contrary, this phenomenon seems to be only at the beginning in Southern and Southeastern Sicily, where A. lobifera displayed lower abundances and the community structure was more diversified.
|Titolo:||Marine invasion by non-indigenous benthic foraminifera in the Sicily Channel (Central Mediterranean Sea): distribution, dynamics and impact|
|Data di pubblicazione:||25-gen-2021|
|Appare nelle tipologie:||8.01 Tesi di dottorato|