The current article presents 18 new records from seven Mediterranean countries. These records include one rhodophyte, fournudibranchs, two crustaceans, one stingray and 10 bony fishes. They are grouped by country as follows: Lebanon - first record ofthe Striped bass Morone saxatilis, the stingray Himantura leoparda, the Areolate grouper Epinephelus areolatus and the Spot-finporcupinefish Diodon hystrix from various parts of the country; Turkey - first record of the invasive red alga Grateloupia turuturufrom the sea of Marmara (region of Bandırma), the sea slug Goniobranchus obsoletus and the crab Arcania brevifrons from theGulf of Antalya and the cladoceran Pleopis schmackeri from several locations along the Aegean Sea; Cyprus - first record of thealien sea slug Berthellina citrina from the region of Cape Greco and an observation of a butterflyfish Heniochus sp. from the northeasternside of the island; Greece - first record of the alien sea slug Anteaeolidiella lurana from the region of Heraklion in Creteand the record of the Atlantic spadefish Chaetodipterus faber and the Black surgeonfish Acanthurus cfr gahhm from SalaminaIsland; Slovenia - first record of the alien sea slug Thecacera pennigera from Izola; Italy - first record of the hybrid Striped bass(Morone saxatilis × Morone chrysops) from the northern Tyrrhenian Sea and a first record of the goldfish Carassius auratus fromthe region of Apulia; Libya - first record of the Red Sea goatfish Parupeneus forsskali and the African surgeonfish Acanthurusmonroviae, respectively from the eastern (Al-Tamimi area) and the western shore (Al-Khums area).

Mesozooplankton was studied during 2008 in coastal waters of the İskenderun Bay in order to determine seasonal changes in abundance, biomass, community structure and their relationship with environmental factors. Samples were collected seasonally at five stations using WP-2 net of 200 µ mesh size by vertical hauls. A total of 23 planktonic groups including 30 copepod species, 4 cladocerans and 4 chaetognaths were identified. Copepods were the most important group during the whole period of survey. Penilia avirostris was found to be dominant in spring, while Paracalanus parvus in summer and winter, and Acrocalanus gibber in autumn. Mesozooplankton abundance varied from 438 ind m⁻³ (autumn) to 7163 ind m⁻³ (spring), while biomass varied between 2.2 mg m⁻³ (summer) and 52.9 mg m⁻³ (autumn). Differences in abundance and biomass between seasons were statistically significant (P < 0.01). Clear seasonal distribution patterns were observed in the area. Two peaks in abundance were defined: a major peak in spring and a second minor one in autumn. It seems that the trophic element was the main factor affecting the density distribution of zooplankton populations, whereas species distributions were more affected by hydrographical parameters, namely: seawater temperature and salinity.

Pleopis schmackeri, a podonid cladoceran not previously recorded in the Mediterranean Sea, was found in the İskenderun Bay for the first time. The samples were collected seasonally during 2012–2015 in the coastal area of İskenderun Bay using a WP-2 zooplankton net (200 µm). Six cladoceran species were found in total, and Penilia avirostris, Pseudevadne tergestina and Evadne spinifera constituted the bulk of the population, while the contribution of P. schmackeri was very low. Although only a single individual was observed in July 2012, the abundance and frequency of P. schmackeri increased in the following years, attaining the abundance of 25.10 ind.m-3 in 2015. Thus, P. schmackeri could be considered as established in İskenderun Bay; however, it seems that it did not affect the distribution of other cladoceran species in the area up to now. P. schmackeri could have entered in İskenderun Bay either as Lessepsian migrant or by ballast waters of commercial ships.

Among non-native copepods, the calanoid Pseudodiaptomus marinus Sato, 1913 is the species probably spreading at the fastest pace in European and neighbouring waters since its first record in the Adriatic Sea in 2007. In this contribution, we provide an update on the distribution of P. marinus in the Mediterranean and Black Seas, along the Atlantic coasts of Europe, in the English Channel and in the southern North Sea. Starting from a previous distribution overview, we include here original and recently (2019–2023) published data to show the novel introduction of this species in different geographical areas, and its secondary spreading in already colonised regions. The picture drawn in this work confirms the strong ability of P. marinus to settle in environments characterised by extremely diverse abiotic conditions, and to take advantage of different vectors of introduction. The data presented allow speculations on realistic future introductions of P. marinus and on the potential extension of its distribution range.

Seasonal variations in species composition and abundance of tintinnids were investigated in the eutrophic coastal and offshore waters of Mersin Bay. Twelve sampling cruises were performed from September 2008 to February 2011. A total of 85 tintinnid taxa were identified. Among the recorded genera, agglutinated Tintinnopsis had the largest number of species (12 species), followed by hyaline loricated Eutintinnius (9 species), and Proplectella (7 species). Stenosemella ventricosa, Tintinnopsis beroidea, T. compressa, Favella azorica, and Helicostemella subulata were the dominant species during the study period. There were clear seasonal variations in species composition and abundance of tintinnids. The highest number of tintinnid species occurred in January 2009 and November 2010 in the entire study area, while the lowest species number occurred in March 2009. Morever, species numbers were higher in offshore stations than coastal stations. Some species were present in the coastal area of the bay, and other species were present offshore. The highest tintinnid abundance values were found in September 2008 (820 ind L-1) and August 2009 (749 ind L-1) at coastal stations. The high abundance values in the coastal stations indicates that an increase of tintinnids is closely related to trophic status of the marine environment. In connection with these results, correlation analysis revealed that chlorophyll-a had an important effect on tintinnid abundance. Tintinnid communities may be used as a potential bio-indicator for assessing the trophic state of the coastal seas and bays.