Search

The <3% dissimilar Amplicon Sequence Variant (ASV) clusters of the 18S‐V4 barcode were used as species‐proxies for the evaluation of ASV composition and ASV diversity indices characterizing the hitherto poorly investigated meiofaunal communities of the south‐eastern part of the Levantine basin. Accompanied by abundance measurements, the relationships of these characteristics with sedimentary and bottom terrain parameters were interpreted. The construction of community composition profiles, namely ASVs' list and their estimated abundances, was done using our previously established procedure (Harbuzov et al., 2022, Marine Genomics 65, 100980), combining metabarcoding with sample reads normalization by the abundance of hard‐bodied meiofaunal taxa. The study province included the 54–1418 m depth range, across vertical sub‐bottom horizons ranging 0–17 cm. Oxygen, hydrogen sulfide and methane concentrations in the pore water, as well as sediment grain size spectra and sedimentary protein and carbohydrate levels, were measured, followed by an evaluation of their involvement in the shaping of the meiofaunal communities' characteristics. Community composition was generally site‐and‐horizon dependent and its abundance decreased with increasing bottom depth and across sub‐bottom horizons, typical to benthic habitats which are nourished by organic carbon from the euphotic zone. The relatively sharply inclined continental slope bottom located in the northern part of the Israeli coast was an exception. Its meiofaunal community characteristics were speculated to be affected by intensive sediment mixing and lateral transport of food from the shelf, in addition to the effect of the euphotic zone‐originated food sources. [ABSTRACT FROM AUTHOR]

New data on 52 non-indigenous mollusks in the Eastern Mediterranean Sea is reported. Fossarus sp. (aff. aptus sensu Blatterer 2019), Coriophora lessepsiana Albano, Bakker & Sabelli, sp. nov., Cerithiopsis sp. aff. pulvis, Joculator problematicus Albano & Steger, sp. nov., Cerithiopsis sp., Elachisina sp., Iravadia aff. elongata, Vitrinella aff. Vitrinella sp. 1 (sensu Blatterer 2019), Melanella orientalis, Parvioris aff. dilecta, Odostomia cf. dalli, Oscilla virginiae, Parthenina cossmanni, Parthenina typica, Pyrgulina craticulata, Turbonilla funiculata, Cylichna collyra, Musculus coenobitus, Musculus aff. viridulus, Chavania erythraea, Scintilla cf. violescens, Iacra seychellarum and Corbula erythraeensis are new records for the Mediterranean. An unidentified gastropod, Skeneidae indet., Triphora sp., Hypermastus sp., Sticteulima sp., Vitreolina cf. philippi, Odostomia (s.l.) sp. 1, Henrya (?) sp., and Semelidae sp. are further potential new non-indigenous species although their status should be confirmed upon final taxonomic assessment. Additionally, the status of Dikoleps micalii, Hemiliostraca clandestina comb. nov. and H. athenamariae comb. nov. is changed to non-indigenous, range extensions for nine species and the occurrence of living individuals for species previously recorded from empty shells only are reported. Opimaphora blattereri Albano, Bakker & Sabelli, sp. nov. is described from the Red Sea for comparison with the morphologically similar C. lessepsiana Albano, Bakker & Sabelli, sp. nov. The taxonomic part is followed by a discussion on how intensive fieldwork and cooperation among institutions and individuals enabled such a massive report, and how the poor taxonomic knowledge of the Indo-Pacific fauna hampers non-indigenous species detection and identification. Finally, the hypothesis that the simultaneous analysis of quantitative benthic death assemblages can support the assignment of non-indigenous status to taxonomically undetermined species is discussed. [ABSTRACT FROM AUTHOR]

• A foraminiferal succession is studied along an anthropogenic C org gradient. • Two biotic indices, TSI-Med and Foram-AMBI, are tested along the C org gradient. • For two major species, a corrected ecological assignment is proposed. • Both foraminiferal indices describe the organic pollution gradient very well. • It is important to distinguish between stress-tolerant and opportunistic species. Coastal environments are affected by multiple pressures resulting from anthropogenic activities, among which organic enrichment (C org) is particularly important. Foraminiferal communities react to organic enrichment by changes in community structure (density, diversity, species composition) and behaviour (metabolism, feeding strategy, reproduction, mortality, etc.). A number of biotic indices based on foraminiferal faunas have been developed to measure the impact of anthropogenic organic enrichment on the ecological quality of marine soft bottom environments. However, the multiple origins of organic matter and its diffuse dispersion make it difficult to clearly identify enrichment gradients and the community changes along them. In this context, marine disposals of activated sewage sludge, which represent localised point sources of organic matter, offer the possibility to study faunal successions along a well-developed stress gradient. The main objectives of this study are to test 1) the ecological assignments of Mediterranean foraminifera species as recently proposed by Jorissen et al. (2018) , and 2) two biotic indices, based on groups of indicator species, developed in the Mediterranean Sea, TSI-Med and Foram-AMBI, along such an organic matter gradient, resulting from a sewage outlet off the Israeli coast, south of Tel-Aviv. Along the studied organic enrichment gradient, Caronia silvestrii dominated the foraminiferal faunas in the most severely impacted zone. Further away from the sewage outlet, faunas were characterised by the dominance of Ammonia tepida. Finally, in the least affected area, farthest away from the sewage outlet , Leptohalysis scottii was the dominant taxon. Our observations strongly contrast with earlier assignments of C. silvestrii and L. scottii to ecological groups III (3rd order opportunists) and V (1st order opportunists), respectively (Jorissen et al., 2018). This discrepancy strongly suggests that additional studies are urgently needed to better characterise the ecological strategies of major ecological index species. When, as we propose here, L. scottii is not included in the group of stress-tolerant taxa for TSI-Med, and C. silvestrii and L. scottii are reassigned respectively to ecological groups V and III for Foram-AMBI, both tested indices clearly show the decreasing impact of organic enrichment with greater distance from the sewage outlet. These species reassignments underline the need to distinguish between stress-tolerant and opportunistic taxa, which do not give the same information about environmental quality. [ABSTRACT FROM AUTHOR]