The Slovenian part of the Adriatic coast is so exceptional largely due to its northerly position and geological structure. This is reflected in its numerous and significant characteristics, which in turn exert influence upon its underwater plant and animal life.
The entire Gulf of Trieste is for the greater part of the year the coldest part of the Mediterranean Sea as well as greatly desalinated due to its numerous freshwater influents. This is the reason why these waters are isolately inhabited by some representatives of cold-loving creatures, e.g. fucus virsoides. In the summer months, however, the Gulf of Trieste warms up to such extent that the majority of the characteristic Mediterranean species can live in it as well.
Cape Madona (the Piran punta) represents one of the most distinct, accessible and at the same time endangered (fishing, recreation) parts of the Slovenian coastal waters with its extremely diverse animal and plant life. The hard rocky bottom, which extends along the entire Slovenian coast, descends more or less evenly from the coastline to the depth of a few meters, and then suddenly takes a greater plunge right down to the sedimentary floor. This "plunge" is particularly explicit off the Cape Madona.
On the north-eastern part of the cape, the rocky bottom initially slopes gently to some four or five meters deep, then becomes very steep and between some ten and fifteen meters turns into a sandy floor. The shallow part of the rocky bottom is overgrown with algae, mostly Cystoseira, Sargassum, Distyota, Halimeda and Padina, from there on Pseudolithophillum sp. and representatives of the genus Codium become more frequent. The cavities, juts and crevices of the steep part of the rocky bottom are home to numerous animal species, particularly to various tubeworms (Spirographis spallanzani, Protula tubularia, Serpula vermicularis), sponges (Euspongia officinalis, Verongia aerophoba, Haliclonia mediterranea) and fish (Serranellus scriba, Chromis chromis, Crenilabrus sp., Corvina nigra, Diplodus sargus, Oblada melamura).
Upon a closer look, however, we may even come across a spider crab (Maia verrucosa) covered with algae, the Sponge crab (Dromia personata), a sea horse (Hippocampus guttulatus), a scorpion fish (Scorpaena scrofa) and the sea snail Chestnut turban (Astrea rugosa). The latter, which happens to be the symbol of the Cape Madona Nature Monument, is today one of the endangered species, for due to its magnificent white operculum, it has become a very popular target of the visitors of the underwater world of the Piran punta as well as of jewelers. Another important animal species of the lower infralittoral is also the coral Cladocora (Cladocora cespitosa) on the southern side of the cape.
This largest of the Slovenian coral species has built some truly dense formations, which here and there almost entirely cover the sea floor. The relief of the floor along the southern side of the cape is less varied. Somewhat more distinct is only the part that descends from two to six meters in depth. This side of the cape is almost void of algae because of the numerous sea urchins (Paracentrotus lividus) living here. Thus, the most numerous inhabitants of this part of the sea floor are sponges, ascidians (Phalusia sp.), coelenterates (Anemonia sulcata), shellfish (Ostrea sp.) and sea cucumbers (Holothuria sp.).
The underwater world of Cape Madona is due to the extreme diversity of its habitants as well as plant and animal species undoubtedly unique not only in the Slovenian coastal waters but in the entire Gulf of Trieste as well. In spite of its small size, it is an indispensable fragment in the mosaic of biodiversity in this northernmost part of the Mediterranean.