Habitats targeted by Life BaĦAR for N2K
Our team of scientists at Fundaćion Oceana and at the Department of Biology within the University of Malta are collecting and analysing new information on:
1. Sandbanks which are slightly covered by sea water all the time (Code 1110 – Annex 1 Habitats Directive)
2. Reefs (Code 1170 – Annex 1 Habitats Directive)
3. Submerged or partially sub-merged sea caves (Code 8330 – Annex 1 Habitats Directive)
The precise location, extent and conservation status of most of these marine habitats within Maltese waters is not available and therefore such information is being collected through this project. By mapping these habitats and developing an inventory with all the relevant data collected we will be in a position to identify new areas that can serve as MPAs and designating them as Sites of Community Importance in terms of the Habitats Directive.
Sandbanks which are slightly covered by sea water all the time
Sandbanks are permanently submerged banks and surrounded by deeper water, which are composed mainly of sandy sediment, but may also include boulders, cobbles, and mud and other varying grain sizes. Sandbanks form elevated, elongated, rounded or irregular topographic features. Sandbanks play an important part in the beach-dune coupling system wherein sandbanks act as a sand store mostly during the winter season.
Within the project area some sandbanks have been identified and a small percentage of this habitat is within the boundaries of Marine Protected Areas MT0000101, MT0000104 and MT0000105. Sandbanks found within these MPAs are generally found in inlets along the coast and beyond the Posidonia meadows. The sediment forming these banks ranges in size from fine sands to course sands and gravel. Cymodocea nodosa is sometimes found associated with these sandbanks. These sandbanks support diverse epifauna, mostly echinoderms and endobiotic species.
The variety in the seabed is partly the result of marine species such as corals that are able to build their own habitat. Such reefs are referred to as biogenic reefs, since they are formed by living species. Geogenic reefs are areas where non-biogenic substrata form a raised or protruding seabed. Changes in elevation result in different environmental conditions (for example light, currents, salinity); thus species preferring such conditions tend to live in these zones. Reefs can be found in shallow waters and in deeper water.
Two reef-forming coral species of particular interest are Lophelia pertusa and Madrepora oculata. These two species are cold water scleratinians (calcium-carbonate secreting species forming a hard skeleton) that are more frequent in the North East Atlantic and form deep cold water (between 4°C and 13°C) coral reefs. Cold water corals are found at depths ranging between -200m and -2000m, where moderate current velocities of 0.5 knots occur. These species occur on seamounts, knolls, banks, carbonate mounds, canyons, channels, slope failures and slumps on continental slopes. These reefs form at a relatively slow rate of 1.3 to 3 m per 1000 years. Cold water reefs are deep-water biodiversity hotspots. Hence due to their rarity in the Mediterranean, their sessile nature, slow growth rate and associated species richness, conservation and management is essential.
In the Mediterranean Sea these species have been recorded in a few areas such as in the Bari Canyon, in Santa Maria di Leuca (southeast Italy) and in the Gulf of Lions (South France). In Maltese waters, these two species have been discovered off the southern and southwestern coast of Malta. Surveys are being carried out in this area as part of this project in order to identify the extent, location and conservation status of deep water coral reefs, as is required in order to designate marine Natura 2000 sites.
Another reef forming species is the coralline alga Lithophyllum lichenoides. This reef forming shore-dwelling species is found on the northwestern coast of Malta, and this area has already been included the coastal Site of Community Importance MT0000024.
There are a variety of geogenic reefs, including the following:
– Vertical rock walls (the underwater part of coastal cliffs)
– Sheer or stepped drop-offs (underwater cliffs)
– Rocky shoals (in Maltese: “sikka”)
– Boulder fields
In deeper waters, geogenic reefs may take the form of escarpments and seamounts.
A common feature amongst these geogenic reefs is that they rise from a level seabed, thus having a nearly vertical rock face with a very steep gradient with attached algae and invertebrates. This types of reef shows a zonation pattern, meaning that species that prefer light conditions (‘photophilic’ species) are found in the brighter upper part, whereas shade loving species (‘sciaphilic’ species) are located in the deeper and darker parts of the reef.
In Maltese waters, geogenic reefs are known to occur in all of the MPAs that have been designated to date. Reefs of geogenic origin are present in the rich and diverse MT0000101. These reefs are colonised by brown algae (‘phaeophytes’) which cover a high percentage of hard substrata, with the commonest species being Cystoseira spinosa var. tenuior particularly at shallower depths. At depths greater than -15m associations of Dictyopteris polypodioides, Cystoseira squarrosa and Sargassum vulgare are more dominant. MT0000102 hosts geogenic reefs which are in very good status with associations of Cystoseira spp., the green alga Flabellia petiolata and the red alga Peyssonnelia squamaria that are all relatively abundant in the area very close to Filfla. Geogenic reefs found within SCI MT0000103 consist of reefs that rise vertically from a sandy bottom littered with large boulders to join submarine bedrock platforms or submarine continuations of emergent cliffs. Associations with F. petiolata and P. squamaria cover most reef areas. The reefs found in this SCI cover an area of 26.13 hectares MT0000104 hosts a significant area of geogenic reefs (1.44ha) with associations of F. petiolata and P.squamaria and other important associations include that with D. polypodioides. MT0000105 hosts geogenic reefs occurring on hard beds and rocks covering an area of 45.01 hectares. The following subtypes occur within this site: reefs with associations of the brown alga D. polypodioides; reefs with associations of the brown algae Halopteris scoparia and Padina pavonica; reefs with associations of the green alga F. petiolata and the red alga P. squamaria; reefs with associations of Cystoseira spp.
Submerged or partially submerged sea caves
This habitat type (code 8330 in Annex I of the Habitats Directive) includes caves that are situated under the sea or opened to it including partially submerged sea caves. Their bottom and sides harbour communities of marine invertebrates and algae. Three distinct zones exist in marine caves which is mainly attributed to the steep light gradients and differing turbulence. Since some light is able to penetrate into the marine cave the first zone is dominated by photophilic algae which further inwards progresses to sciaphilic species. The mid-section is dominated by sessile invertebrates such as sponges, corals, tubicolous polychaetes, bryozoans, hydroids, brachiopods and foraminifera, and generally lacks algae although some encrusting coralline algae may be present. The deepest part of the cave is almost completely devoid of sessile organisms, being in complete darkness. Depending on the depth below sea-level, the size, shape and aspect of the mouth dictate the extent of these three zones. Other factors that contribute to the type of species assemblage present relate to temperature changes, presence of salinity gradients (haloclines), presence of particular geomorphologic features, and the sea floor which may be loose sediment or rock.
Caves cover a small length of the coastline within SCI MT0000101. A total of five fully submerged caves and six semi-submerged caves are present in MT0000103, supporting very diverse assemblages characteristic of semi-obscure caves. The macrofaunal component of this assemblage type consists of a large number of bryozoans, sponges and serpulid polychaetes. The submerged caves, mostly located in the northern half of the site, have a very complex physiognomy and a bottom characterised by fine sediment. The largest of these appear to be two caves lying below the shore of Il-Ħofra ta’ Birwin and Iż-Żerqa area. The emergent caves, which are distributed throughout the study area, also have a very complex physiognomy, both underwater and above sea-level. The bottom inside the emergent caves consists of bedrock, with small boulders, cobbles and pebbles present in some places. Two fully submerged caves are present below the shore on the western side of the inlet at MT0000104, supporting typical cave species, for example the stony sponge Petrobiona massilliana. Partially submerged caves are known to occur in MT0000105 mainly along the coast of the island of Comino, however no quantitative data is available.