MoNa

Seagrass meadows of the Mediterranean endemic Posidonia oceanica - a marine habitat type of high EU conservation priority – presented extensive cover in the shallows of Santorini Caldera. This habitat fringes much of the coastline along the Akrotiri peninsula in Thera, south Aspronissi islet, and parts of the bays of Agia Irini and Korfou in Thirassia island, at depths varying between 3-25 m

An interesting marine diversity, mostly featuring various sponge species, characterizes the coralligenous reefs in the Caldera’s deep twilight zone (>30 m).

Rocky formations, covering about 70% of the inner-rim coastline, are the dominant underwater habitat in the Caldera, most typically consisting of steep sloping cliffs, continuous rocky platforms, outcrops, or variously-sized boulders.

Unique submarine geological structures, as these meandering rockwalls in Aspronissi islet, are yet another distinguishing feature of Caldera’s rich geodiversity.

Strictly unique to the volcanic islets of Nea and Palia Kameni, shallow rocks and boulders appear here in the colour of rust, owed to iron-oxidizing bacteria that thrive in iron-rich environments such as the islets’ popular thermal springs

A cargo ship, sank several decades ago between the islets of Nea and Palia Kameni, serves now as an artificial reef, offering ground and shelter to numerous marine species but also an appealing wreck dive to Santorini’s scuba enthusiasts.

Don’t shoot the messenger: The impressive lionfish (Pterois miles) of Red Sea origin, is one of the many exotic newcomers in the increasingly warming seas of the Eastern Mediterranean. Lack of drastic measures to fight climate change and reckless depauperazation of local marine natural predators are the actual culprits for this alarming underwater transformation.

Uncontrolled anchoring as well as the arbitrary placement of numerous non-ecological-safe moorings (especially in the bays of Thirassia), were identified as the most acute pressure on Caldera’s Posidonia meadows.

Numerous mussel farms along the western coast of the Butrint Lagoon harvest its naturally eutrophic environment, providing significant income to the local community since as early as the 1960’s.

Patchy meadows of the lesser seagrass Cymodocea nodosa, here fringing the famous Ali Pasha’s castle, develop at both ends of the Vivari Channel which connects the lagoon with the sea. These patches become denser on the shallow soft bottom plateau where the channel meets the open sea, eventually forming dense meadows at depths between 1 - 5 m.

According to locals, this lush Cymodocea nodosa meadow at the mouth of the Vivari Channel used to host a large and thriving population of the Mediterranean endemic fan mussel Pinna nobilis. Unfortunately, the ongoing mass mortality decimating this protected species across the Mediterranean basin over these last couple of years, has apparently reached the Albanian coasts as well: only dead individuals were spotted during this survey.

Between Ksamil and the mouth of Butrint, calcareous rocky reefs predominate at depths ranging from as shallow as the sea surface and down to over 30 m at steeper locations. Although perennial brown algal “forests” are expected to thrive in such well-illuminated Mediterranean reefs, these were here recorded sporadically only in the very shallow horizons (0 -1 m). Various shrubby algae (e.g. Padina pavonica, Jania rubens, Corallina elongata, Dictyota dichotoma, Laurencia spp.) instead prevailed, frequently though interrupted by extensive sea urchin barrens, or heavily destructed facies indicating illegal date mussel (Lithophaga lithophaga) fishing activities.

Entering the twilight zone, here at depths of ~ 30 m and on, coralligenous formations take over the seascape, mostly characterized by a rich diversity of massive, erect, or encrusting sponges. Other common encounters include various species of erect bryozoans, sea squirts and starfish. The highly invasive green alga Caulerpa cylindracea was frequently recorded smothering these communities.

Fishing nets, fishing lines and various other marine litter were also commonly detected in this zone.

Posidonia oceanica meadows, a habitat type offering significant ecosystem services and thus of high conservation priority, were found to characterize much of the studied coasts at depths between 5 - 28 m, reaching their lower limit off the Ksamil islets. The rapid and largely uncontrolled coastal development taking place in this area within the last decades, however, has obviously taken its toll on this valuable ecosystem: heavy epiphytism indicating organic pollution, as well as various type of marine litter and frequent anchor scars fragmenting the meadows, were commonly detected in this area.

Cystoseira (=Gongolaria) barbata algal forests, one of the most valuable and threatened marine habitat across the Mediterranean nowdays, were the most representative feature of the shallow rocky reefs around both Nessebar and Ravda. These lush Cystoseira stands, here usually intermixed with patches of various green and red algae, offer precious shelter and feeding ground to a rich diversity of other marine species, such as the peacock wrasses Symphodus tinca and the stone crabs Eriphia verrucosa.

Multiple seagrass species, and specifically Zostera noltei, Zostera marina, and the brackish water species Zannichelia palustris, are known to occur on the shallow sandy beds of Bulgaria; in terms of cover and extent, some of the most important such mixed meadows were found at depths between 1 - 5 m west off Cape Acrotiria, presenting healthy state and even progressive trends during the last 15 year.

An interesting, mixed phase of hard- and soft-bottom habitat types was observed in Ravda, where rocky reefs with Cystoseira (=Gongolaria) barbata forests intermix with Zostera seagrass beds. This ‘mixed’ Zostera - C. barbata community had not been previously reported from other locations along the Bulgarian Black Sea coast.

In terms of absolute cover and extent, sandy seabeds dominate most of this marine area at depths greater than 10 m. Where not covered by seagrass meadows, these sands still offer crucial habitat to rich infaunal (=living within the sediment) communities; these include various bivalves, but also the mud shrimp Upogebia pusilla.