Abstract
The spatial distribution of sea bed covers and seagrass in coastal waters is of key importance in monitoring and managing Mediterranean shallow water environments often subject to both increasing anthropogenic impacts and climate change effects. In this context we present a methodology for effective monitoring and mapping of Posidonia oceanica (PO) meadows in turbid waters using remote sensing techniques tested by means of LAI (Leaf Area Index) point sea truth measurements. Preliminary results using Daedalus airborne sensor are reported referring to the PO meadows at Civitavecchia site (central Tyrrhenian sea) where vessel traffic due to presence of important harbors and huge power plant represent strong impact factors. This coastal area, 100 km far from Rome (Central Italy), is characterized also by significant hydrodynamic variations and other anthropogenic factors that affect the health of seagrass meadows with frequent turbidity and suspended sediments in the water column. During 2011–2012 years point measurements of several parameters related to PO meadows phenology were acquired on various stations distributed along 20 km of coast between the Civitavecchia and S. Marinella sites. The Daedalus airborne sensor multispectral data were preprocessed with the support of satellite (MERIS) derived water quality parameters to obtain here improved thematic maps of the local PO distribution. Their thematic accuracy was then evaluated as agreement (R2) with the point sea truth measurements and regressive modeling using an on purpose developd method.
Highlights
Posidonia oceanica (L) Delile (PO) is one of the most important Mediterranean seagrass and is distributed along many Italian coasts which currently host more than 40% of European PO meadows.While PO ecosystems guarantee stability of the littoral zones affected by erosion and play a fundamental ecological role by providing indispensables oxygen and biomass from their photosynthetic activity to other sea organisms, here they are threatened and under stress from many factors and generally exibit a meadows surface and productivity reduction [1]
Considering that, due to evident local PO meadows fragmentation, the per pixel classification results are enough scattered, classified PO density could be retained assimlable to local PO meadow % coverage directly linked to measured leaf area index (LAI) distribution within the different neighborhood areas of each sampling station
Such classified PO point density values were assessed from SAM classification result (Figure 7), using a GIS focal analysis algorithm with different focal square wind ows compatibles with sea truth sampling schema
Summary
While PO ecosystems guarantee stability of the littoral zones affected by erosion and play a fundamental ecological role by providing indispensables oxygen and biomass from their photosynthetic activity to other sea organisms, here they are threatened and under stress from many factors and generally exibit a meadows surface and productivity reduction [1] Both the direct disturbances arising from marine activities (harborages, dredging and escavation works, ...) and the shallow waters turbidity coming from increased human factors (urban settlement concentration, agriculture, land use, ...) focusing on the coastal areas and the consequent rise of sediment and pollution discharged by the rivers are within the main reasons for Mediterranean and Italian PO decline [2]. Many biological tests have been carried out on PO as good indicator of water quality and status of marine ecosystems [4,5], its accurate spatial patterns mapping is still in progress in various Italian coastal zones affected by high anthropogenic pressure and often characterized by diffused shallow waters turbidity which often makes difficult their extensive detection by means of remote sensing techniques
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
