This research is part of the LTER (Long-Term Ecological Research) project, a network of terrestrial, freshwater, transitional water and marine sites, on which ecological research is conducted on a multi-decade scale. LTER studies ecosystems, their dynamics and evolution, the relationships between biodiversity and ecological functionality, water quality, productivity, the role of resource availability, the effects of pollution and climate change. The research focuses on the study of the variability of zooplankton groups in the Portofino marine protected area, in Punta Faro. The samplings were carried out in the years 2018–2019, and the results were compared with the values of the years 2003–2005, interesting from a meteorological climatic and biological point of view. The plankton community of the Punta Faro system was analyzed by means of a modeling approach to obtain information on the functionality and health status of the system and to verify whether this has undergone any alterations in the last decade. The analyses carried out show a clear difference between the three-year period 2003–2005 and the two-year period 2018–2019, highlighting how environmental changes, such as the increase in temperature, have led to higher costs of system functioning in the last two years. The mesozooplankton community has changed both in terms of abundance of organisms and in terms of organization and functionality.

The water column of harbors contains significant amounts of (priority) hazardous trace metals that may be released into coastal areas of high societal and economic interests where they may disturb their fragile equilibria. To deepen our understanding of the processes that influence the transport of the various metal fractions and allow for a more rigorous environmental risk assessment, it is important to spatially monitor the relevant chemical speciation of these metals. It is of particular interest to assess their so-called dynamic fraction, which comprises the dissolved chemical forms that are potentially bioavailable to living organisms. In this study this was achieved in the Genoa Harbor (NW Italy) for copper (Cu), lead (Pb), cadmium (Cd) and zinc (Zn) by applying a multi-method approach. For the first time in this system the dynamic fractions of the target metals (Cu_Dyn, Cd_Dyn, Pb_Dyn, Zn_Dyn) were observed in real-time on-board by voltammetry using innovative electrochemical sensing devices. Trace metals in the operationally defined dissolved <0.2 μm and <0.02 μm fractions were equally quantified through sampling/laboratory-based techniques. The obtained results showed a clear spatial trend for all studied metals from the enclosed contaminated part of the harbor towards the open part. The highest Cu_Dyn and Cd_Dyn fractions were found in the inner part of the harbor while the highest Pb_Dyn fraction was found in the open part. The proportion of Zn_Dyn was negligible in the sampled area. Small and coarse colloids were involved in Cu, Cd and Zn partitioning while only coarse colloids played an important role in Pb partitioning. The determined concentrations were compared to the Environmental Quality Standards (EQS) established by the EU and those determined by the Australia and New Zealand to trigger for 99 and 95% species protection values. The results of this work allow us to highlight gaps in the EQS for which metal concentration thresholds are excessively high or non-existent and should urgently be revised. They also reflect the need to quantify the potentially bioavailable fraction of hazardous trace metals instead of just their total dissolved concentrations. The data support the establishment of environmental quality standards and guidelines based on realistic risk assessment to protect aquatic life and resources and ultimately human health.

Phytoplankton and zooplanktonic communities form the base of the Antarctic food web. This study examines the evolution of the mesozooplanktonic system in Terra Nova Bay during the austral summer (December–February), focusing on the impact of sea ice dynamics and the resulting phytoplankton blooms. Terra Nova Bay (Ross Sea) offers a valuable context given its high productivity and ecological variability. Using a diachronic approach, we analyzed data spanning twelve years to understand how the system’s structure and functionality change over time. A novel key metric, Days since Sea Ice Melting, was employed to track shifts in phytoplankton community development and trophic dynamics. The results indicate that the system enters the summer season increasing primary productivity and creating the support for the development of a more complex and organized system during the season. The phytoplankton bloom recorded during mid-season, coped by an increase in biomass, is followed by the establishment of a well-organized grazing system. A secondary phytoplankton bloom is observed towards the end of the summer, but it does not significantly affect mesozooplankton communities. Overall, this study highlights the dynamic nature of Terra Nova Bay’s mesozooplanktonic community and evaluates the influence of climate change on Antarctic marine ecosystems.

The skeleton of most Porifera species consists of siliceous spicules that, after the sponge death, persist for a long time in the sediment. The reduced suspension occurring within the meadows of the seagrass Posidonia oceanica makes these habitats a stable deposit for sponge spicules. Spicules trapped into the network of rhizomes progressively buried, named “matte”, represent a sedimentary sequence interpretable on a temporal scale. By means of a vertical corer we collected samples of sediment at 0.5, 1, 1.5 and 2 m depth along the matte profile in order to quantify the amount of biogenic silica used to assess past dynamics of the sponge community in four P. oceanica meadows of the Ligurian sea. The content in biogenic silica was determined by spectrophotometric analysis of the sediments. While at Prelo Bay the values are constant in the core sample, a general decreasing trend with depth was observed in the meadows of Punta Pedale, while in the site of Punta Manara the major amount of silica was found deeper in the matte. The temporal variations of sponge abundance were probably due to historical anthropogenic factors. In the meadow of Bergeggi, BSi concentrations, significantly lower compared to all other sites, were likely caused from inputs from the close Savona harbor and strong bottom currents avoiding spicule deposition.

Zooplankton plays a crucial role in marine ecosystems by mediating trophic interactions, recycling nutrients, and attenuating carbon flux via the biological pump. Understanding zooplankton community structure and functioning is key to predicting ecosystem responses to environmental change and global carbon cycling. The eLTER network provides long-term ecological data to disentangle natural variability from directional environmental change. Here we analysed a 20-year (2003-2022) time-series of zooplankton abundance and community composition data (Povero et al. 2024) from the pelagic compartment of the eLTER site Promontory of Portofino (eLTER-IT15-001-M), station Punta Faro (44° 17.750’ N; 9° 13.050’ E) (Fig. 1). Our analysis aimed to: 1) assess changes in zooplankton community composition over time, 2) identify common trends across taxonomic descriptors, and 3) investigate the influence of environmental variables. To explain observed patterns, we combined time-series analysis with two complementary modelling approaches. An Ecopath model was use to compare community structure and functioning between early (2003-2005) and later (2018-2019) periods (Vassallo et al. 2022). Stable isotope mixing models based on carbon isotope fingerprints of amino acids (Larsen et al. 2013) estimated the proportional contributions of distinct production sources (i.e., marine autotrophs, heterotrophic bacteria, and terrestrially-derived organic matter). Our results revealed strong seasonal cycles and long-term changes in environmental variables, accompanied by shifts in zooplankton abundance and community composition. Total mesozooplankton and copepod abundance increased since 2019, particularly in summer and autumn (Fig. 1). Species richness increased from 2009, while the Simpson index declined, indicating a more even distribution of individuals across taxa. These trends were accompanied by increased contributions of carnivorous (Corycaeus spp.) and detritivorous (Oncaea spp.) copepods, other typically carnivorous groups (Chaetognatha), and gelatinous suspension-feeders (Thaliacea). In parallel, we observed decreased contributions of typically herbivorous (e.g., Calocalanus styliremis, Euterpina acutifrons, Paracalanus nanus, Clausocalanus parapergens) and small copepods (Oithona. nana), Appendicularia, and meroplankton. Zooplankton variability modestly correlated with environmental changes, including positive temperature seasonal anomalies since 2012 and increased oligotrophy. Our findings suggest a transition from a herbivore-dominated food web towards a system increasingly supported by detrital and microbial processes. The Ecopath model indicated increased consumption on detritus and heterotrophs (Fig. 2; Vassallo et al. 2022). Isotope models estimated highest proportional contributions from marine autotrophs but increased contributions from microbial secondary production to summer zooplankton, especially bacterivores and detritivores (Fig. 2). Thus, while stability in the role of zooplankton of capturing newly fixed carbon and exporting it to depth is confirmed, at least at the study site, these shifts may reflect the ecosystem’s capability to reorganise under changing environmental conditions, potentially at the cost of reduced energy transfer efficiency and higher metabolic demands.