Programma della conferenza

Energy exchanges between benthic and pelagic domains are regulated by physical processes and trophic interactions among species, which support the Benthic-Pelagic coupling (BPC). Identifying the species or groups of species that most contribute to BPC and act as key couplers is of interest for understanding this important ecosystem process. This analysis explores the species contribution to the BPC within the Northern Ionian Sea (NIS) and Aegean Sea (AS) food webs modelled through the Ecopath mass-balance modelled approach.
Two original NIS and AS models composed by 51 and 44 functional groups (FGs) of species, respectively, were reorganized in a standard food-web model structure of 25 FGs for each one, to compare the results. Starting from consumption flows matrices of each standard model, the contribution of FGs to BPC was calculated through a Benthic-Pelagic Coupling Index (BPCI). BPCI summarized pelagic and benthic flows (downward, dQf) and those between benthic and pelagic domains (upward, uQf) based on consumption flows (t km^-2 y^-1) estimated for each FG, considered as both predators and prey (excluding non-living detritus groups), through the pelagic, benthopelagic, demersal, and benthic domains. In addition, FGs were classified as direct, mediating or partial couplers according to their domains of membership and completeness in coupling between the benthic and pelagic domains.
In both food webs, zooplankton and suprabenthic crustaceans were the main direct couplers. In the NIS, the main mediating couplers contributing to uQf were benthopelagic decapod crustaceans (35% of the total uQf), demersal non-piscivorous fishes (21%) and benthopelagic fishes (19%). In the AS, demersal non-piscivorous fishes (mediating couplers) showed the highest contribution to uQf (45%), while benthopelagic cephalopods contributed to 31% of the total dQf.
Results stress the importance of demersal and benthopelagic FGs in BPC mechanisms, supporting the energy and matter recycling in the ecosystem, and thus its productivity.

Climate change is inducing profound alterations at all levels of biological organization, from individual organisms to entire ecosystems. These shifts are expected to continue in response to ongoing climate warming, which is largely mediated by metabolic rate. As metabolic rate is one of the first traits of organisms to respond to climate change, forecasting the extent of this change by the end of the century would lay the groundwork for disentangling higher ecological impacts and informing conservation decisions for potential mitigation. Here, we aimed to predict the metabolic rate response of invertebrates, which serve as primary consumers in the trophic web, under the CMIP5 climate change scenarios. Our predictions showed that metabolic rates could increase substantially, with more pronounced increases in species living at high latitudes under the modest climate change scenario.

In marine phytoplankton ecology, biomass indices such as cell number or chlorophyll a determination may provide estimates of population abundances, but they do not account for the functional activity of species or groups. Conversely, molecular traits based on DNA and RNA, and ribosomal small subunit (18S rDNA) may be key for the metabolic dynamics in pelagic ecosystems. In this study, the metabolic activity has been assessed in two diatom species, Chaetoceros socialis and Skeletonema marinoi, typically occurring in the northwestern Adriatic Sea phytoplankton assemblages, by applying RNA/DNA and taxon-specific 18S rRNA/rDNA ratios. Significant correlations between abundance, chlorophyll a, carbon content and proteins were found (from rs=0.570 to rs =0.986, p<0.001). Biomass trend followed the logistic curve and during the initial stages of growth, the RNA/DNA and species-specific 18S rRNA/rDNA ratios of C. socialis and S. marinoi reached their maximum values (i.e., 23.2±1.5 and 15.3±0.8, and 16.2±1.6 and 30.1±5.4) after 2 and 6 days, respectively, in individual culture, with a subsequent sharp decreasing value for both species. In the co-cultured experiment, the maximum molecular ratio values were obtained after 4 days, in the exponential phase, showing values of 13.4±0.4 and 9.4±0.7 for total RNA/DNA and diatom 18S rRNA/rDNA ratios, respectively. Considering the molecular ratios for each target taxon, C. socialis and S. marinoi 18S rRNA/rDNA ratios showed maximum values of 24.4±2.0 and 8.2±0.7, for each species respectively, 4 days after the initial inoculum. These findings showed that changes in functional activity of primary producers may be associated with differences in RNA/DNA ratios, suggesting their potential as predictive tools for phytoplankton dynamics in coastal ecosystems that are subjected to pollution and climate pressures. Moreover, phytoplankton represents an important share of the first level of the trophic web and these ratios may be useful to evaluate coastal marine ecosystem productivity.