The promotion of long-term monitoring in ports is crucial for the early detection of non-native species (NNS). In 2018, we started a continuous NNS monitoring across five marinas in the Gulf of La Spezia, using a standardized protocol developed by the Smithsonian Environmental Research Center (SERC). This method utilizes horizontally oriented 14x14 cm PVC settlement panels attached beneath a brick. Each year, 50 panels were deployed at a depth of 1 meter for a three-month summer immersion period.

Over the eight-year monitoring program, 324 panels were recovered and 198 sessile taxa identified (including 16 NNS). Temporal and spatial variability were observed in both the fouling assemblage structure and NNS richness. Notably, this monitoring detected the arrival year of the barnacle Balanus trigonus in the study area: it was first observed at two marinas in 2023 and expanded to all investigated marinas by 2024, outcompeting native barnacles.

In addition, the effectiveness of the SERC method in detecting NNS was evaluated in 2021 at two sites in the Gulf of La Spezia, by comparing it with three alternative approaches: vertical PVC panels, in-water scraping within a fixed quadrat and off-water scraping using a hand-held rigid net. A total of 75 sessile taxa were identified across all methods, including 13 NNS. Fouling assemblages differed significantly between the four methods, except for the samples taken using the PVC panels at one site. While both the SERC method and vertical panels yielded comparable species richness, the first one was most effective in detecting NNS. Conversely, certain taxa were exclusively observed in scraping samples, suggesting that integrating multiple approaches may optimizes the assessment of fouling community.