Proceedings of the Second Mediterranean Symposium on Marine

PROCEEDINGS OF THE SECOND MEDITERRANEAN SYMPOSIUM ON MARINE VEGETATION (ATHENS, 12-13 DECEMBER 2003)
236
MAPPING OF THE POSIDONIA OCEANICA
MEADOW ON THE SLOVENIAN COAST
Tihomir MAKOVEC 1 & Robert TURK 2
1 Marine Biology Station Piran, National Institute <strong>of</strong> Biology, Fornace 41, 6330 Piran, Slovenia
2 Institute <strong>of</strong> <strong>the</strong> Republic <strong>of</strong> Slovenia for Nature Conservation, Regional Office Piran, Tartinijev trg 12, 6330 Piran, Slovenia
INTRODUCTION
Mapping <strong>of</strong> seagrass meadows has become an indispensable tool for a proper research
and long-term monitoring <strong>of</strong> <strong>the</strong> meadows in view <strong>of</strong> <strong>the</strong>ir management and protection.
A preliminary investigation on <strong>the</strong> size and morphological features <strong>of</strong> <strong>the</strong> Posidonia
oceanica (L.) Del. meadow on <strong>the</strong> Slovenian coast was carried out by SCUBA divers
already in 1993 (Vukovic & Turk, 1995). More accurate methods were needed in order
to state stability, progression or regression <strong>of</strong> <strong>the</strong> meadow and to take proper
conservation measures. A Memorandum <strong>of</strong> Understanding (2002) between <strong>the</strong> Institute
<strong>of</strong> <strong>the</strong> Republic <strong>of</strong> Slovenia for Nature Conservation, <strong>the</strong> International Cooperation for
Environment and Development <strong>of</strong> <strong>the</strong> Principality <strong>of</strong> Monaco and <strong>the</strong> Regional Activity
Centre for Specially Protected Areas (RAC/SPA) <strong>of</strong> <strong>the</strong> Barcelona Convention enabled <strong>the</strong>
financing <strong>of</strong> aerial photography and <strong>the</strong> elaboration <strong>of</strong> a map <strong>of</strong> <strong>the</strong> meadow.
Study area
The study area is located in <strong>the</strong> Gulf <strong>of</strong> Trieste (nor<strong>the</strong>rn Adriatic), between <strong>the</strong> towns <strong>of</strong>
Izola and Koper, with <strong>the</strong> only site <strong>of</strong> P. oceanica seagrass meadow along <strong>the</strong> nor<strong>the</strong>rn
and western coasts <strong>of</strong> Istria. The patches <strong>of</strong> Posidonia are situated between stony
coastline and mud bottom, at a depth from 0.5 to 4 m. The area is 1 km long and 50
m wide. The meadow density varies between 360 and 588 shoots/m 2 . The area is a
known tourist resort with many recreational activities and has been subjected to some
extent to organic pollution from <strong>the</strong> city <strong>of</strong> Koper.
Mapping and monitoring
A special emphasis was laid on underwater mapping <strong>of</strong> different habitat types (Turk
et al., 2002). The underwater inspection <strong>of</strong> <strong>the</strong> area was carried out at five sampling
stations in <strong>the</strong> years 2000-2001. The diver with camera followed <strong>the</strong> transect rope and
filmed all habitat types. The coverage <strong>of</strong> each habitat type was calculated from <strong>the</strong> habitat
type distribution drawings.
Aerial photography and fur<strong>the</strong>r image processing appears to be a technique which is
particularly suitable in shallow waters (Pasqualini et al., 1998). The aerial photographs <strong>of</strong>
<strong>the</strong> meadow were taken during winter 2002/2003, in <strong>the</strong> period <strong>of</strong> greater transparency
<strong>of</strong> <strong>the</strong> water and when <strong>the</strong> nearby Cymodocea nodosa meadow is not yet grown.The
results were checked out by SCUBA diving in <strong>the</strong> following months. Aerial photographs