The Contribution of Artificial Structures to Ecosystem Functioning at Landscape Level

Artificial structures (such as pilings, seawalls, jetties, aquaculture and fishery facilities, moorings etc.) are ubiquitous features in Venice Lagoon, yet their contribution to the structure and functioning of the lagoon ecosystem is little known. This thesis investigates how species abundance and composition varies on the two most abundant types of artificial structures within the Venice lagoon, seawalls, and pilings, in relation to variable proximity of these structures to urban centers. The analysis extends to evaluating the profound impact of this variation on a crucial ecosystem service, that is water filtration by filter feeders, primarily oysters and mussels. Field sampling was conducted to determine the composition and abundance of dominant species associated to the two types of structures in 3 locations at different proximity to populated urban centers. Then established equations from existing literature were employed to estimate the filtration rate based on the abundance of filter feeders associated to different structures in various locations. Our findings revealed significant variations in the composition and abundance of species between the two different structures, as well as between the urbanized and less urbanized locations. In total, 24 species were present on seawalls, while 23 species were present on pilings. Three main species were the most abundant which are oysters (Ostreidae sp.), Mytilus galloprovincialis, and barnacles (Cirripeda sp.), with oysters being more abundant on seawalls while the others being more abundant on pilings. Additionally, we compiled an estimate of the filtration rate of oysters and mussels associated to seawalls and pilings over the entire lagoon. These findings are important for understanding how species composition and ecosystem functions vary with specific structure types, and how this variation affects main ecosystem functions. Understanding how species composition vary with structure types and how this variation reflects on ecosystem functioning is crucial within this unique and rapidly changing ecosystem where the need for coastal protection is increasing in the light of predicted climate change.