The sea

Landscape Park Strunjan is the only area of state-level protection in Slovenia that includes the sea: it comprises a 200-metre belt of coastal sea (also protected within the Strunjan Nature Reserve) and the entire Bay of Strunjan as far as Pacug.

The Strunjan Sea

The varied types of sea bottom and the living conditions characterising the individual marine zones compose a collage of habitats with vibrant animal and plant worlds. Along with the area surrounding the natural monument of Cape Madona at the far end of the Peninsula of Piran, the marine portion of the Strunjan Nature Reserve is the site of the greatest biodiversity in the Slovene sea.

Sea Shore, Littoral Zones and Sea Bottoms

The individual rock components of the flysch rubble spalling from the cliff faces into the sea do not all have the same resistance; the sandstone debris smooths into round gravel-stones under the constant motion of the waves, forging a rocky shore; marlstone decomposes rapidly and is one of the chief agents for the formation of silty sea bottom; while the most sturdy rocks are the occasional boulders that you can come across on the beach and in the shallower areas of the sea, originating from thick carbonate interlayers.

Almost all types of the seafloor characteristic of the Slovene coast are featured within the area of the park, with the exception of the limestone bottom, which is only present to a small extent off Izola.

The rocky sea bottom is home to organisms that require a firm base for their growth. The hard substrate is mostly covered by algae and sponges, while larger stones and rocks serve as hiding places for big fish and crabs.

The soft sandy and silty bottoms in the shallower areas still receive the necessary light for the growth of vast underwater meadows, providing shelter to numerous animal species, while at somewhat greater depths, where light intensity falls, life mostly moves into the seafloor, leaving the floor with a false appearance of bareness.

The Supralittoral Zone

The zone of the coastline regularly splashed by the droplets of seawater from the breaking waves is called the supralittoral, or spray, zone. The living conditions here are extreme due to the high salinity and exposure to wide temperature variations.

  • The rock samphire (Crithmum maritimum) is a true halophyte, which grows in the soils of the supralittoral zone characterised by a high concentration of salt.
  • The small periwinkle (Melarphe neritoides) is a species of sea snail (a little one) that defines the spray zone borderline. When exposed to the air and the drying heat of the sun, it withdraws into the shell and bars the entrance with its corneous operculum. It can survive like that for several months.

The Eulittoral Zone

The rhythm of life in the eulittoral, or intertidal, zone is dictated by the tides. The sea organisms living here pass the periods of low tide outside the water, unsheltered from the hot sun, dehydration, wind and rain.

  • The acorn barnacle Chthamalus depressus has a calcareous shell which protects it from scorching heat and dehydration during low tide. As the tide comes up and the sea washes over it, the barnacle extends its feather-like limbs from its shell to comb the water for plankton and other floating food particles.
  • Fucus virsoides is a common brown alga of rocky seacoasts. It is characterised by holdfasts for clinging to rocks and mucilage-covered leaves that resist desiccation during periods of low tide. virsoides is an endemic species, found exclusively in the Adriatic Sea.
  • The Mediterranean shag (Phalacrocorax aristotelis desmarestii) is a subspecies of the family of cormorants. This sea bird is an excellent swimmer, diving up to 80 m deep to capture its prey. From late spring until autumn, over 1,500 specimens – i.e., 11 % of the global population of this subspecies – sojourn in the area of the Slovene sea. In Slovenia, the Mediterranean shag is a protected bird species.

The Sublittoral Zone

The more favourable living conditions of the sublittoral zone, which is permanently covered by seawater, make for a greater variety of life forms. The animals and plants that reside here are fully aquatic organisms, unable to survive out of water for even short periods of time.

On the Rocky Bottom

The characteristic underwater landscape of well-lit rocky substrate is covered by green and brown algae, with the mermaid’s wine glass and the peacock’s tail among their finest representatives. The seaweed from the Cystoseira genus can form genuine underwater forests, which provide unique habitats for numerous marine organisms, particularly nudibranchs, sponges and echinoderms, as well as blennies, gobies, sea breams and porgies among fish species.

Due to their numerous cavities, tunnels and nooks the huge blocks of rock, a peculiarity of Landscape Park Strunjan, are excellent hiding places for large fish, including brown meagre, brown wrasse and European conger, and decapod crustaceans, such as the sponge crab and the lesser spider crab. A particularly fascinating inhabitant of the rocky bottom is the Mediterranean stony coral, the only polyp occurring in the Mediterranean Sea to form reef structures.

  • The date shell (Lithophaga lithophaga) is a mollusc that cannot be farmed. It is characterised by extremely slow growth – merely 1 centimetre in 3 to 5 years. It bores into rocks by secreting a weak acid and using its foot for mechanical abrasion. Date shell gatherers cause enormous damage to the marine environment, as they resort to extremely destructive methods to pick these molluscs, including explosives. Such actions endanger not only the date shell, but also numerous populations of sea organisms which use rock crevices as shelter, food and breeding sites.
  • The brown alga Cystoseira barbata forms underwater swards of up to 50 cm tall bushes, home to inshore fish. The Cystoseira genus habitat is a natural environment characterised by a diverse species composition. Though it is still well-represented and preserved in the waters of Strunjan Nature Reserve, it has already been identified as one of the endangered habitat types in the broader Mediterranean area.
  • The Mediterranean rainbow wrasse (Coris julis) is a thermophilic fish, which has gradually migrated to the Slovene sea from the more southern parts of the Adriatic due to a rise in the temperature of the shallower waters of the Gulf of Trieste.
  • With its bright colour, the yellow tube sponge (Aplysina aerophoba) is one of the most typical representatives of the sponge population in our sea.
  • Mediterranean stony coral (Cladocora caespitosa) is a cold-water reef-building coral species. The anomalously high temperatures in the Slovene sea in 2011 and 2012 caused their extensive mortality and damage (so-called coral bleaching). It is a well-known fact that climate change has a greater impact on those sea species that are already under stress from anchoring, pollution and ocean acidification, and are thus increasingly rare.

In the Sea Meadows

Sea meadows are good indicators of the quality of seawater. Although as bathers, we are usually less than impressed by floating leaf-like blades of seaweed – which, however, is a perfectly natural phenomenon, analogous to trees-shed leaves – we should take comfort in knowing that their presence proves that the water is clean.

The flowering plants of Landscape Park Strunjan – the slender seagrass, the dwarf eelgrass and eelgrass – cover the shallow sandy bottom in expanses of underwater meadows. They can only be found at up to 8 metres of depth, as in deeper areas the amount of sunlight penetrating the water is insufficient to allow photosynthesis. The seaweed is also home to seahorses, fries, tube-dwelling worms, cuttlefish, octopuses, violet sea urchins, sea cucumbers and warty venuses, as well as the largest Mediterranean mollusc, the noble pen shell.

  • The noble pen shell (Pinna nobilis) is the largest Mediterranean bivalve, which can grow to a length of up to 120 cm. With its pointed end firmly anchored into the soft sea bottom, it serves as bearer of various species of invertebrates and algae, and often hides inside its shell the pinna pea crab (Pinnotheres pinnotheres). The noble pen shell is endemic to the Mediterranean and in the Slovene waters recognised as a species at risk due to anchoring, pollution and overharvesting by environmentally-insensitive divers hunting for souvenirs.
  • The slender seagrass (Cymodocea nodosa) is the most widespread of the three types of seaweeds found in the park. The beds of seagrasses contribute essential oxygen and form an important underwater living space for numerous animal species.
  • The European fan worm (Sabella spallanzanii) is a marine worm hiding inside a calcium tube it builds for itself and with a fan-shaped crown of feeding tentacles as the only part of its body projecting from the tube. In the event of danger, it will retract the tentacles into the tube or even discard the entire crown, growing it back later.
  • The long-snouted seahorse (Hippocampus guttulatus) is a fish with a typical upright posture, and just like the short-snouted seahorse (Hippocampus hippocampus) it is a threatened species due to the sales of desiccated specimens as tourist souvenirs.
  • The damselfish (Chromis chromis) is the only Adriatic coral reef fish.

On the Silty Bottom

The most common type of seabed in the Slovene sea is silt. In this seemingly modest area you can observe numerous animals crawling over, digging into or attaching to the sediment covered bottom, such as brittle stars, the tunicates, starfish, sea urchins and sea anemones. The presence of life is also indicated by holes in the muddy soil, dwellings of small crabs and molluscs. The level of threat for the organisms in the silty substrate is high, as such bottoms allow fishing with various fishing gear.

  • The hermit crab (Paguristes oculatus) can support algae and sea anemones on the shell to scare off predators, forging a symbiotic relationship: the anemone that protects the crab is repaid by receiving pieces of the crab’s meals.
  • Brittle stars (Ophiuroidea) belong to the group of echinoderms. They resemble starfish in body outline, but their whip-like arms are sharply marked off from the body disk.
  • The loggerhead turtle (Caretta caretta), a regular guest in the Slovene sea, is one of the highly threatened Mediterranean species. Several dozen animals get tangled in fishing nets every year in our waters alone, and most of them drown. In addition to the nets, the turtles are also endangered by powered vessels and the general degradation of the marine environment.