## 5 Discussion  
A very limited number of foraminiferal studies has included such a high number of samples, and despite intensive studies in the Adriatic Sea, the only research is likely the comprehensive investigation of Jorissen [34], analysing the distribution of benthic foraminifera in 285 samples. A wide range of environmental factors simultaneously shape foraminiferal assemblages, as functions of Adriatic circulation and hydrodynamics. However, determining the effects and magnitude of those factors is challenging, especially when considering such regional distribution. Nevertheless, we identified depth intervals that reflect rapid foraminiferal assemblage turnovers that are recognized at 28-29 m, 58-59 m, and 215 m water depth intervals. It is worth noting that the 28-29 m and 215 m intervals match well the boundary between the inner to middle meritic (i.e., 30 m) and outer meritic to upper bathyal (i.e., 200 m), respectively. These subdivisions have been widely used for depth reconstructions based on foraminiferal zonation in the Cenozoic [62; 63]. On the other hand, the foraminiferal turnover identified at 58-59 m cannot be associated with the middle-outer meritic boundary (i.e., 100 m); this change corresponds to the bathymetric subdivision between infralittoral and circaltitoral zones of the meritic Mediterranean zones [64]. This has also been applied for benthic foraminiferal distribution in the Gulf of Naples (Tyrrhenian Sea) [65], where the circaltitoral zone is defined as between 40-50 m and 150-200 m. In the wide-ranging overview of foraminiferal distribution in the Adriatic Sea, [PERSON] [34] inferred that the most important parameters influencing the distribution of the 50 most abundant foraminiferal species were bathymetry, sand fraction, calcium carbonate, and organic matter. Indeed, the author identified several biofacies units (i.e., 7.5-25 m, 20-100 m, and 50-1225 m) that are not only defined on the bathymetric range but also on sand and organic matter contents. Our Gf model does not exactly identify the same \"bioracies\" units of [PERSON] [34] and this might be ascribed to a different sampling strategy: (a) sampling device (i.e., grab and piston core vs. box-core); (b) assemblages (i.e., total vs. living assemblages); (c) sieve-size (i.e., 150 \(\upmu\)m vs. 63 \(\upmu\)m) and/or investigated areas: (i) geographical extension (i.e., the entire Adriatic Sea vs. the central-southern part of the western side of the Adriatic Sea); (ii) bathymetric range (i.e., 7.5-1152 m vs. 13-703 m) and/or temporal changes in the benthic environment. In our study, the factors that most contributed to shaping foraminiferal assemblages across the entire depth gradient were organic matter contents (OC), followed by grain-size (sand) and anthropogenic contaminations (PLI). These variables match well those (organic matter and sand) identified by [PERSON] [34]. Interestingly, our Gf models for 13-28 m and 59-215 m bathymetric ranges reveal which factors shape the foraminiferal assemblages. While organic matter (i.e., OC and N) is still the most important factor at greater depths (59-215 m), at shallower depths the grain-size (i.e., sand content) and pollution (i.e., PLI) seem to turn out to be the most important variables. Figure 8: Performance of structural equation modelling along three depth ranges (**A**) 13–703 m, (**B**) 13–28 m and (**C**) 59–215 m. Total Nitrogen [N], Pollution Load Index [PLI]. The interpretations of putative causal relationships between abiotic and biotic variables are quite challenging. For the full depth gradient, abiotic and biotic parameters are scarcely-to-moderately correlated with depth, exhibiting only a direct negative influence on infauna (\(\text{SPC}=-0.35\)). The percentages of infaunal taxa are expected to decrease in shelf/bathyal areas, where the organic matter supplied to the bottom is limited.