Evaluation of Macrophyte Community Dynamics (2015–2020) in Southern Lake Garda (Italy) from Sentinel-2 Data

Abstract

Macrophytes are of fundamental importance to the functioning of lake ecosystems. They provide structure, habitat, and a food source and are a required component in monitoring programs of lake ecological quality. The key aim of this study is to document the variation in spatial extent and density of macrophytes seasonally between 2015 and 2020 of the Sirmione Peninsula (Lake Garda, Italy), using Sentinel-2 imagery. In addition to this, our results were compared to previous data from imaging spectrometry; individual parameters affecting macrophyte communities were tested, and the possible effect of the COVID-19 lockdown on macrophyte colonization was evaluated. Satellite images allowed the mapping of the spatiotemporal dynamics of submerged rooted macrophytes in order to support monitoring of the shallow water ecosystem under study. Substantial changes were found in both spatial extent and density over the period from 2015 to 2020, particularly in 2019 when there was almost a complete absence of dense macrophytes. Variables found to influence the amount of macrophytes included transparency, chlorophyll–a, water level, winter wave height, and grazing by herbivores. A separate analysis focusing on areas associated with boat transit found a recovery in macrophyte coverage during the period of COVID-19 lockdown. The outcome of the study highlights a decline in the density of the macrophytes and a shift towards deeper areas compared to the situation in 1997. The area examined is part of an internationally important site containing the highest abundance and diversity of overwintering water birds in Italy. Exploiting satellite data at high frequency provided an insight to understand the dynamic changes and interactions with herbivorous birds, environmental factors, and anthropogenic pressures, revealing a delicately balanced and threatened ecosystem.

Satellite-derived multivariate world-wide lake physical variable timeseries for climate studies

“…EsA CCI Lakes product. Data generated in the ESA CCI Lakes project have been used in five use cases [81][82][83][84] , including a case study on Greenland lakes which has been currently submitted to Scientific Report 85 . The case studies were part of the project and they focused on analysing the five thematic variables available in the product: lake water level, lake water extent, lake ice cover, lake surface water temperature and lake water leaving reflectance.…”

A Bibliometric Analysis of Lake Restoration with Submerged Macrophytes

“…For example, Ghirardi et al (2022) [161] and Xia et al (2022) [162] explored the decade scale of SAV dynamics using remote sensing images, providing a reference area for restoration. The classification accuracy of SAV changed from 60% to nearly 95% in existing studies [158,[163][164][165], which were mainly limited by the resolution of images, water depth, water color, and spectral traits of specific submerged macrophytes [158,166].…”

A Satellite-Based Tool for Mapping Evaporation in Inland Water Bodies: Formulation, Application, and Operational Aspects

“…There are also likely to be applications in ecological management as evaporation contributing to a significant decrease in the water level can also alter the light climate in the littoral zone of lakes. This would be particularly important in the south of Lake Garda, where a delicate ecological balance is maintained between submerged aquatic plants, supporting an overwintering waterfowl population ranked the most diverse and abundant in Italy [75,76]. Finally, the dependence of the LakeVap tool on any type of satellite-derived LSWT data gives the possibility to enlarge its applicability to even medium-small sized water bodies exploiting the relatively high spatial resolution (30 m) of Landsat sensors.…”