Past and present ecological status of the soft bottom macrozoobenthos in a large mediterranean lagoon: any signals of climate change?

Abstract

Coastal lagoons are transitional areas between land and sea, particularly vulnerable to human impact. The aim of this work was to compare soft bottom macrozoobenthic communities in the Lagoon of Marano and Grado, before (past period: 1993 to 1995) and after the entry into force of the Water Framework Directive-WFD (present period: 2008 to 2021). In the present period higher richness, abundances, and diversity were observed, also considering each water type (euhaline, polihaline and mesohaline) and basin (Marano and Grado) separately. The multivariate analyses also showed differences among periods and water types. According to the AMBI index, most stations were slightly disturbed in all periods and water types, and biocoenotic affinity did not vary significantly. The frequency of echinoderms increased in all water types, whereas the frequency of the polychaete Hediste diversicolor decreased in eu- and polihaline water bodies. These changes can mainly be explained by a general increase in salinity, and therefore probably the result of a marinization process, a decreasing confinement of the lagoon. As the calculation of M-AMBI is derived from AMBI, diversity and richness, this process could lead to a better ecological status sensu WFD, but with the loss of the characteristics and ecological functions of this paralic ecosystem.