Habitat Suitability Modeling to Identify the Potential Nursery Grounds of the Atlantic Mackerel and Its Relation to Oceanographic Conditions in the Mediterranean Sea

Our knowledge for the distribution of Atlantic mackerel (Scomber scombrus) in the Mediterranean Sea is limited and fragmented. In the current work habitat suitability modeling was applied to summer acoustic surveys data of Atlantic mackerel juveniles derived from the north part of the Mediterranean (i.e., acoustic data from the Gulf of Lions, pelagic trawls held during acoustic surveys in Spanish Mediterranean waters, south Adriatic Sea, Strait of Sicily, and North Aegean Sea) using generalized additive models (GAMs) along with satellite environmental and bathymetry data. Bathymetry along with sea surface temperature and circulation patterns, expressed through sea level anomaly and the zonal component of the absolute geostrophic velocity, were the environmental variables best to describe nursery grounds. The selected model was used to produce maps presenting the potential nursery grounds of Atlantic mackerel throughout the Mediterranean Sea as a measure of habitat adequacy. However, the assessed potential nursery grounds were generally marked as “occasional,” implying that although there are areas presenting high probability to encounter Atlantic mackerel, this picture can largely vary from year to year stressing the high susceptibility of the species to environmental conditions. In a further step and toward a spatial management perspective, we have estimated and visualized the overlap between Atlantic mackerel and anchovy/ sardine juvenile grounds throughout the basin. Results showed that although the degree of overlapping was generally low, not exceeding 15% in general, this varied at a regional level going up to 30%. The potential of the output of this work for management purposes like the implementation of spatially-explicit management tools is discussedVersión del edito

Density dependence in the spatial behaviour of anchovy and sardine across Mediterranean systems

A spatial indicator—the spreading area index—is used to describe anchovy and sardine spatial distribution in relation to biomass variation and to look for ecosystem differences within the Mediterranean basin. Specifically, the variation in the spreading area index in relation to biomass was examined for different areas of the Mediterranean Sea (i.e. Aegean Sea, western Adriatic Sea, Strait of Sicily, Gulf of Lion, and Spanish Mediterranean waters). In order to capture the spatial variability of the population at different levels of fish density, acoustic survey data for the years of highest, lowest, and intermediate abundance were used. In a subsequent step standardized values of spreading area and biomass were estimated to allow comparisons. Results showed pronounced area differences. A significant relationship was revealed in the case of anchovy for areas with extended continental shelf (i.e. Aegean Sea, Adriatic Sea, and Gulf of Lion), indicating an increase in biomass with an increase in the spreading area. No relationship was found for areas dominated by narrow continental shelf and strong currents (i.e. Spanish Mediterranean waters and the Strait of Sicily). With regard to sardine, an increase in biomass was followed by an increase in the spreading area when estimates from the Aegean Sea, the Adriatic Sea, and the Strait of Sicily were considered together. The relationship was even more Abstracts–Theme Session B 9 pronounced when analysis was limited to the Aegean Sea and the Strait of Sicily. No relationship was found for the Spanish Mediterranean waters and the Gulf of Lion. This clearly implies that spatial indicators should be integrated into ecosystem management, taking into account that they can be area‐ or ecosystem‐dependent

The rapid spread of SARS-COV-2 Omicron variant in Italy reflected early through wastewater surveillance

The SARS-CoV-2 Omicron variant emerged in South Africa in November 2021, and has later been identified worldwide, raising serious concerns. A real-time RT-PCR assay was designed for the rapid screening of the Omicron variant, targeting characteristic mutations of the spike gene. The assay was used to test 737 sewage samples collected throughout Italy (19/21 Regions) between 11 November and 25 December 2021, with the aim of assessing the spread of the Omicron variant in the country. Positive samples were also tested with a real-time RT-PCR developed by the European Commission, Joint Research Centre (JRC), and through nested RT-PCR followed by Sanger sequencing. Overall, 115 samples tested positive for Omicron SARS-CoV-2 variant. The first occurrence was detected on 7 December, in Veneto, North Italy. Later on, the variant spread extremely fast in three weeks, with prevalence of positive wastewater samples rising from 1.0% (1/104 samples) in the week 5–11 December, to 17.5% (25/143 samples) in the week 12–18, to 65.9% (89/135 samples) in the week 19–25, in line with the increase in cases of infection with the Omicron variant observed during December in Italy. Similarly, the number of Regions/Autonomous Provinces in which the variant was detected increased fromone in the first week, to 11 in the second, and to 17 in the last one. The presence of the Omicron variant was confirmed by the JRC real-time RT-PCR in 79.1% (91/115) of the positive samples, and by Sanger sequencing in 66% (64/97) of PCR amplicons

PICOPHYTOPLANKTON DYNAMICS IN NOISY MARINE ENVIRONMENT

We present a stochastic reaction-diffusion-taxis model to describe the picophytoplankton dynamics along a water column. The model, which is valid for poorly mixed waters, typical of the Mediterranean Sea, considers intraspecific competition of picophytoplankton for light and nutrients. Random fluctuations of environmental variables are taken into account by adding a source of multiplicative noise to the diffusion equation for the picophytoplankton biomass concentration, whose distribution along the water column shows a maximum at a certain depth. After converting our results into chlorophyll a concentrations, we compare theoretical distributions, obtained for different noise intensities, with the experimental chlorophyll a distribution sampled in a site of the Strait of Sicily. Specifically, we find that position and height of the chlorophyll a peak concentration obtained from the model are in a very good agreement with field observations. Finally, we consider the effects of seasonal variations on phytoplankton dynamics by adding an oscillating term in the equation for the light intensity

Preliminary Analysis on Correlations between Spatial Distribution of Chlorophyll-a and Experimental Data of Biomass in the Strait of Sicily

This study, using both remotely sensed and measured in situ data, is directed to the analysis of the correlations between the chlorophyll-a concentration and the biomass of sardines and anchovies acoustically evaluated in the Strait of Sicily. This work, inter alia, shows the usefulness of remote observation of seas in determining possible relationships between fish stocks and some oceanographic parameters (Sea Surface Temperature, Chlorophyll-a, Zooplankton)