Spatial changes in community composition and food web structure of mesozooplankton across the Adriatic basin (Mediterranean Sea)

[摘要] Zooplankton are critical to the functioning of ocean food websbecause of their utter abundance and vital ecosystem roles. Zooplanktoncommunities are highly diverse and thus perform a variety of ecosystemfunctions; thus changes in the community or food web structure may provideevidence of ecosystem alteration. Assemblage structure and trophodynamics ofmesozooplankton communities were examined across the Adriatic basin, thenorthernmost and most productive basin of the Mediterranean Sea. Sampleswere collected in June–July 2019 within the framework of the MEDIAS (MEDiterranean International Acoustic Survey) project, along coastal–offshoretransects and from the surface to ca. 200 m depth, covering the wholewestern Adriatic side; consistently environmental variables were alsorecorded. Results showed a clear separation between samples from thenorthern-central Adriatic and the southern ones, with a further segregation,although less clear, of inshore vs. offshore stations, the latter being mostlydominated in the central and southern stations by gelatinous plankton. Suchpatterns were mainly driven, based on the outputs of the distance-basedlinear model, by fluorescence (as a proxy for primary production) fornorthern-central stations, i.e. closer to the Po River input, and by dissolvedoxygen, together explaining 44 % of the total variance. Overall, at the basinlevel, the analysis of stable isotopes of nitrogen and carbon allowed foridentifying a complex food web characterized by three trophic levels from filterfeeders–herbivores to carnivores, passing through a general pattern ofomnivory with varying preference towards herbivory or carnivory. Stableisotope signatures spatially varied between inshore vs. offshore communitiesand across sub-areas, with the northern Adriatic exhibiting greater δ 15 N and more variable δ 13 C than the other two sub-areas,likely attributable to the occurrence in the area of organic matter of bothterrestrial and marine origin. Our results contribute to the knowledge ofmesozooplankton community and trophic structure, at the basin scale across acoastal–offshore gradient, also providing a baseline for the future assessment ofpelagic food webs within the European Council (EC) Marine Strategy Framework Directive.

[学科分类] 大气科学