Marine Habitats

Seagrasses, as the name implies, are closely related to plants on land, and have roots, stems, leaves, flowers and seeds. Seagrass meadows, are an important habitat, and are afforded protection through several legal instruments.
They offer/constitute important feeding and nursery areas for various marine animals, and are crucial in supporting marine biodiversity. Seagrasses also stabilise the sediment, which reduces erosion and wave and current energy, protecting the coastline and beaches. They also absorb nutrients from runoff and cycle nutrients into the water, improving water clarity and quality, and are an important carbon sink, helping to combat climate change.
These meadows are sensitive to anchoring, overfishing and pollution. One should not anchor, moor or sit on seagrass meadows.

Algal communities are found growing on reefs, in caves, along rocky shores and in the vicinity of seagrass meadows. The characteristic species vary, depending on the conditions present. For example, well-lit areas on gently sloping rocky shores support macroalgal communities with belts of brown algae such as Cystoseira species that form three-dimensional canopies, whereas shaded rocks are inhabited by calcareous red algae (Corallinales).

Several species of the genus Cystoseira and Sargassum are under strict protection, therefore they cannot be damaged or picked.

The sheer vertical cliffs along the southwestern coast are favoured by the red alga Lithophyllum byssoides, which form concretions in the form of platforms, also referred to as algal rims or ‘trottoirs’.

Reefs are an important habitat that are very diverse in terms of the communities they support They are considered ‘biodiversity hotspots’ and host a variety of different species, including corals, sponges, molluscs, crustaceans and fish.

Geogenic reefs are made of geological features, such as boulders or rocks that create a three-dimensional structure. There are a variety of coastal reefs, such as vertical rock walls (the underwater part of coastal cliffs), sheer or stepped drop-offs (underwater cliffs), rocky shoals and boulder fields. In deeper waters, geogenic reefs may take the form of escarpments and seamounts.

Species growing on reefs are fragile and sensitive, and therefore they should not be touched. In view of this, they are afforded protection through several legal instruments.

Biogenic reefs are concretions formed from dead or living organisms, which provide a surface where other species can live. Malta’s offshore waters are home to such reef habitats, including diverse deep sea communities of cold water corals at depths of 300 – 1000m and a fossilised stony sponge reef, at depths of around 300m off the North coast of Gozo.

Many of areas in which these deep sea habitats are have been designated as marine protected areas due to the presence of these reefs, while a number of the cold water coral species (Cnidaria) that form these reefs are also strictly protected in themselves, such as the Smooth Black Coral (Leiopathes glaberrima), Zigzag Coral (Madrepora occulata), Red Coral (Corallium rubrum) and Stony Coral/Deep Water Coral (Lophelia pertusa).

Caves around the Maltese Islands have been formed over time through wave action and geological processes. So called ‘karst caves’ and ‘sinkholes’ along the coast create impressive landscapes on land and under water.
The environmental conditions within underwater caves vary depending on the size and structure of the caves, the extent to which they are submerged, the exposure to waves and currents, as well as changes in temperature, salinity and light. These varying conditions will in turn affect which communities of living organisms are found within.
Sea caves harbour communities of marine invertebrates and algae near the mouth of the cave. These communities change along the gradients of light intensity and turbulence occurring from the entrance to the inner parts of the cave. The conditions of low light and temperature found in caves can be similar to deep-water habitats, so that organisms usually found in deeper waters often inhabit caves, even in relatively shallow water.

Species growing on cave walls, such as sponges and bryozoans, are fragile and sensitive, and therefore they should not be touched. In view of this, caves are afforded protection through several legal instruments.

A number of deep sea caves have also been discovered at depths of 200 to 780m, which are thought to have been formed a very long time ago, possibly during the Messinian age 5-7million years ago, when the Mediterranean Sea was dry in many places.

Sediment habitats are the most widespread type of habitat found on the ocean floor. These habitats range from boulders and cobbles, through pebbles and shingle, coarse sands, sands, fine sands, muds, and mixed sediments.
Although these seabed habitats often appear barren, they are in fact home to many benthic (bottom-living) species that live in, or on, the sediments, including molluscs, crustaceans and fish. For this reason these habitats are often important fisheries grounds.

Rhodolith accumulations are a particular sedimentary habitat, that have been recorded in several sites off Malta’s eastern coast at depths of 50 m to 100 m. Rhodoliths are colourful, unattached nodules formed by calcareous red algae, which may take a number of different forms, ranging from compact spherical nodules to ones with twiglike branches. Accumulations can range from sparse nodules occurring individually to dense beds. Due to this complex architecture, this habitat supports a rich biodiversity and in Maltese is referred to as ‘ramel ħaj’ which translates to ‘living sand’.