Dynamics of mesoplankton community related to sea ice melting in Terra Nova Bay during the austral summer: a diachronic analysis Aim: Characterize mesoplankton dynamics during austral summer, studying sea-ice melting moment to normalize data from several years Study area : Terra Nova Bay (Ross Sea) Why plankton? Plankton represents the base of the sea trophic web and is a fundamental compartment for marine system (also Antarctic) Samplings: 44 samplings were collected in Faraglione Station (74° 43' S ,164° 6’ E) during 12 years of PNRA (Italian National Project for Antarctica Research) expeditions Network Analysis: Provides Ecological Indicators describing functional and structural characteristics of a system 𝑇𝑆𝑇 = ෍ 𝑖=1,𝑗=1 𝑛 𝑇𝑖𝑗 𝑇𝐿𝑗= 1 + ෍ 𝑖=1 𝑛 𝐷𝐶𝑗𝑖× 𝑇𝐿𝑖 𝐴𝑀𝐼= 𝐾 × ෍ 𝑖,𝐽 𝑇𝑖𝑗 𝑇𝑆𝑇 × 𝑙𝑜𝑔𝑇𝑖𝑗 × 𝑇𝑆𝑇 𝑇𝑖× 𝑇𝑗 Trophic Level (TL): TL=1 to primary producers and detritus, other calculated as: Total System Throughput (TST): Sum of all flows in the system Average Mutual Information: Measure of flows organization Mass balanced models Modelling approach based on mass-balanced models flows analysis (Ecopath with Ecosim) Required: - Biomass - Production/Biomass, - Consumption/Biomass - Diet Matrix Days Since Sea-Ice Melting (DaSIM): A novel method to normalize data from different years on the same temporal scale, based on sea ice melting threshold (Dataset of Sea-Ice Coverage from Copernicus), defining four phases in austral summer General Additive Models (GAM) was used to study statistical relationship between DaSIM and Ecological Indicators. Ecological Indicators Discussion - Biomass evidencing the importance of copepods in plankton composition, particularly for Calanidae family. - Phytoplankton biomass and Primary Production identify the moment of phytoplanktonic bloom (Early Season) in correspondence to sea ice melting. A possible second bloom, with the increase of this parameters during end of season. - However, the second phytoplankton bloom is not mirrored by system functionality indicators, probably because the response is too slow or the biomass produced is addressed to other compartments (e.g. microplankton) not considered here. - In Late Season Mean Trophic Level, AMI, TST having they’re maximum values pointing out a system well developed and efficient together with higher equilibrium in term of biomass distribution and groups presence. The mesoplanktonic compartments in Terra Nova Bay starts with the Phytoplanktonic bloom in Early Season, producing a lot of biomass. The system uses this biomass very rapidly, in the beginning, and optimizes the flows organization later when the biomass decreases and the trophic level raises. Biomass GAM Results A. Guida 1,2, P. Povero 1,3, M. Castellano 1, S. Magozzi 1,3, A. Novellino 2, C. Paoli 1,3, P. Vassallo 1,3 Introduction Materials and methods Results 1 DISTAV, Dipartimento di Scienze della Terra dell’Ambiente e della Vita, Università degli Studi di Genova, corso Europa 26, 16132, Genova, Italia 2 ETT S.p.A., Via Sestri 37, 16154, Genova, Italia 3 NBFC (National Biodiversity Future Center), Palermo, Italia 𝐷𝐶𝑗𝑖= fraction of prey i in diet of predator j 𝑇𝐿𝑖= Trophic Level of prey i 𝑇𝑖𝑗= flux out of i- group going in j- group K= scalar constant Distribution of twelve years of expeditions, colors connected with the samplings in the austral summer period Ecopath master equations Consumption = production + respiration + unassimilated part Production = predation mortality + fishing mortality + biomass accumulation + net migration + other mortality DaSIM Temperature Salinity Legends Total System Throughput 0.0102 . 0.1-0.05 Average Mutual Information 0.00296 0.0486 0.0331 * 0.05-0.01 Mean Trophic Level 0.00245 0.0057 ** 0.01-0.001 Primary Production 1.19E-03 *** <0.001 Total Biomass 2.00E-16 0.0669 Phytoplankton Zooplankton - Copernicus Climate Change Service (C3S) Climate Data Store (CDS). Copernicus Climate Change Service (C3S) (2024): Sea Ice Concentration Daily Gridded Data from 1979 to Present