Benthic-pelagic coupling (BPC) is a combination of downward (from pelagic to benthic) and upward (from benthic to pelagic) flows of organic matter and nutrients mediated by trophic interactions in the food web. Hydrological changes in marine ecosystems affect BPC patterns at several temporal and spatial scales. Thus, a food-web perspective help to to quantify and disentangle the role of ecosystem components and high trophic levels species in the BPC. This study investigated the spatio-temporal variability of energy and matter flows between the benthic and pelagic domains in two areas (Salento and Calabria) of the Northern Ionian Sea (Central Mediterranean Sea) during two different periods. The region is subject to large-scale oceanographic changes, e.g., the Adriatic-Ionian Bimodal Oscillating Systems (BiOS), that might result in relevant spatial and temporal BPC changes. Four food-web models describe the trophic structure, the role of ecosystem components and energy flows in the Salento and Calabrian areas, during two BiOS periods, the anticyclonic (1995-1997) and the cyclonic phases (2003-2005). The food webs are described by 58 functional groups obtained by aggregating species into ecological domains, depth gradients and biological traits. The role of species in the BPC has been quantified using a new Benthic-Pelagic Coupling Index calculated on the basis of food web flows estimated by models. The results highlight the pivotal role of deep faunal communities, in which demersal and benthopelagic species sustain upward energy flows towards the pelagic domain and shelf faunal communities. Temporal changes driven by BiOS affect the trophic state of the deep communities resulting in considerable variations in their amount of consumption flows. In addition, the presence of submarine canyons seems to better support the stability of the Calabrian food web in both investigated periods, whereas geomorphological traits of the Salento area seem to support greater pelagic production during the cyclonic period than the anticyclonic one. Benthopelagic species show an important role as couplers. In particular, Aristaemorpha foliacea, Hoplostetus mediterraneus, Macrourids and Plesionika martia are important couplers of bathyal communities in both areas.

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Although the Mediterranean Sea is a crucial hotspot in marine biodiversity, it has been threatened by numerous anthropogenic pressures. As flagship species, Cetaceans are exposed to those anthropogenic impacts and global changes. Assessing their conservation status becomes strategic to set effective management plans. The aim of this paper is to understand the habitat requirements of cetaceans, exploiting the advantages of a machine-learning framework. To this end, 28 physical and biogeochemical variables were identified as environmental predictors related to the abundance of three odontocete species in the Northern Ionian Sea (Central-eastern Mediterranean Sea). In fact, habitat models were built using sighting data collected for striped dolphins Stenella coeruleoalba, common bottlenose dolphins Tursiops truncatus, and Risso’s dolphins Grampus griseus between July 2009 and October 2021. Random Forest was a suitable machine learning algorithm for the cetacean abundance estimation. Nitrate, phytoplankton carbon biomass, temperature, and salinity were the most common influential predictors, followed by latitude, 3D-chlorophyll and density. The habitat models proposed here were validated using sighting data acquired during 2022 in the study area, confirming the good performance of the strategy. This study provides valuable information to support management decisions and conservation measures in the EU marine spatial planning context.

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Bottlenose dolphins have a complex vocal repertoire that varies depending on behavioral context, social structure, group composition, and anthropogenic pressures. This current study describes the whistle characteristics of bottlenose dolphins for the first time in the South Adriatic Sea while assessing the potential differences between whistle characteristics of geographically separated dolphins within neighbouring waters of the North Ionian Sea. The results show that whistle characteristics were similar between Taranto Gulf (Italy) and Boka Bay (Montenegro), despite their spatial differences. The mean peak frequency was 10kHz for each study location while the mean minimum and maximum frequency ranged from 7 to 14kHz. The average duration of whistles was 500 milliseconds. These results share similarities with previous literature, although several studies reported slightly different mean peak frequencies, ranging up to 15kHz in the neighbouring waters of Croatia and Italy. Further, harmonics were produced and formed in 40% of the whistles in Taranto Gulf and 30% of the whistles in Boka Bay. A high incidence of harmonics has previously been associated with behavioral states (i.e., travelling) and with certain types of marine traffic (i.e., fishing vessels). Therefore, it is important to collect simultaneous data on the visual behavior of the focal group as well as document the type and density of marine traffic within the proximity of the dolphins to have an in-depth understanding of vocal behavior. Despite the similarities of whistle characteristics of Taranto and Boka Bay, the whistle contours showed notable variations. Upsweep whistles were the most regularly produced whistle type in each location, which coincides with previous studies in the Mediterranean Sea. However, the least produced whistle had a concave contour in Taranto and was flat in Boka Bay. Previous studies have confirmed that flat whistles account for the least produced whistle contour in the Mediterranean Basin. Examining the whistle characteristics and the variation in whistle contours provides an in-depth understanding of the behavioral complexity as well as its plasticity in the presence of pressure. Therefore, future studies need to include behavior, group composition, noise levels, and human presence to enable an effective understanding of variation in whistle characteristics of bottlenose dolphins.