Current status (as of end of 2020) of marine alien species in Turkey

Abstract

The 2020’s update of marine alien species list from Turkey yielded a total of 539 species belonging to 18 taxonomic groups, 404 of which have become established in the region and 135 species are casual. A total of 185 new alien species have been added to the list since the previous update of 2011. The present compilation includes reports of an ascidian species (Rhodosoma turcicum) new to the marine fauna of Turkey and range extensions of six species. Among the established species, 105 species have invasive characters at least in one zoogeographic region, comprising 19% of all alien species. Mollusca ranked first in terms of the number of species (123 species), followed by Foraminifera (91 species), Pisces (80 species) and Arthropoda (79 species). The number of alien species found in seas surrounding Turkey ranged from 28 (Black Sea) to 413 (Levantine Sea). The vectoral importance of the Suez Canal diminishes when moving from south to north, accounting for 72% of species introductions in the Levantine Sea vs. only 11% of species introductions in the Black Sea. Most alien species on the coasts of Turkey were originated from the Red Sea (58%), due to the proximity of the country to the Suez Canal. Shipping activities transported 39% of alien species, mainly from the Indo-Pacific area (20%) and the Atlantic Ocean (10%). Misidentified species (such as Pterois volitans, Trachurus declivis, etc.) and species those classified as questionable or cryptogenic were omitted from the list based on new data gathered in the last decade and expert judgements. The documented impacts of invasive species on socio-economy, biodiversity and human health in the last decade as well as the legislation and management backgrounds against alien species in Turkey are presented.

Alien Species Threat across Marine Protected Areas of Turkey—An Updated Inventory

“…The present inventory revealed that (i) existing MPAs were exposed to different levels of alien biota impact, with a clear decreasing trend from the Levantine coasts to the northernmost regions of the Aegean Sea; (ii) the Suez Canal was the most important vector for species introductions, and was also responsible for the existence of the huge proportion of Red Sea-originated biota; and (iii) the high rates of established aliens and invasive species were obvious in every MPA. These results were in accordance with the general trends observed for the alien biota of the entire coast of Turkey during the last decade [12,35]. The low number of species determined in the northern Aegean protected areas should be carefully monitored, since they may be related to lower research efforts, in comparison to the northern Levantine coasts.…”

“…in Libya [41]. Receiving 185 new alien species introductions just during the last decade, the immense impact of bioinvasions to the Turkish marine realm reflected the diversity estimates, now reaching to 539 species, 404 of which were established in the region [12]. Thus, it was not surprising that there was a high number of alien species (289 sp.)…”

“…An updated version of this file (including floral elements) focusing solely on alien taxa was used in a recent comprehensive inventory [12], which formed the core data of the present study. For better presenting the distributional patterns of alien species, we also included previously unpublished observations (not new for the country or the region but overlooked occurrences in corresponding MPAs).…”

“…The terminology of alien species followed [10], referring to species introduced by human activities, while species undergoing climate-shifted range expansions, without humanassisted spread, were not considered to be alien. Species that formed self-maintaining populations with at least two records in the area (three records for fish) spread over time and space, were classified as established species, while those having been recorded only once (no more than twice for fish) with no evidence of self-sustaining populations were classified as casual species [12]. Established aliens whose populations had proliferated and rapidly expanded their distributional range by overcoming biotic and abiotic barriers in the region were treated as invasive species [35].…”

“…The latter phenomenon is of special importance throughout the Mediterranean Sea, since the basin is among the most ecologically altered marine regions globally, representing a hotspot of biological invasions [10,11]. Human-mediated alien species introductions are regarded as one of the main causes of drastic biodiversity changes in the region, causing a troublesome problem because of the unprecedented rate of their invasion, and the irreversible impacts they pose on local ecosystems, human health and the socio-economy [12,13], and so their impact on protected areas could thus be much more severe [14,15]. Despite the widespread theory that MPAs are resistant to invasion owing to their high species diversity and putative abundance of predators, competitors and parasites of alien species, this hypothesis is not fully supported and marine reserves may even promote the introduction of alien species [10,16].…”