CORALLINE ALGAE FORMATIONS
Resplendent corallines are highly noticeable algae, colorful sponges, corals and other attractive marine life.
Colorful and rich corallines are one of the most beautiful sights of the Mediterranean and the second most important ecosystem after Posidonia Meadows. These unique structures are formed by calcified algae in low light conditions and are rich in diversity. Called ‘biogenic reefs’ due to formation by accumulation of biological calcified organisms, they can be compared tropical coral reefs in terms of biodiversity and importance. Light-preferring green and brown algae and high grass meadows like Posidonia give way to low-light corallines at darker depths and, in the Mediterranean, these may be found at habitats with very little light. Corallines starting at 20-25 meters of depth in the Northern Aegean Sea are found at much deeper locations on our Mediterranean coasts because of the high transparency due to oligotrophic conditions in the Mediterranean. Corallines may also be found underneath rocky growths and around shadowy Posidonia roots near the shore/ at shallower depths. Coralline reefs, structurally and functionally complex, are high in diversity; 20% of Mediterranean recorded marine species are found in these reefs. Sponges, corals, Reteporella sp. And Thalia sp. are amongst the most prevalent invertebrate sessile animals with high diversity. Coralline reefs are very important thanks to commercial fisheries and diving activities as they are economically an aesthetically attractive.
Calcified algae, main component of corallines, are attractive due to their bright colors like pink, red, purple and orange. The colonies may be up to 30 cm in diameter and 20 cm in height. Their calcified nature renders them highly fragile and easily thorn off or broken from physical impact. Divers must pay attention to their fins and equipment.
WHY ARE THEY IMPORTANT?
Coralline formations, like kelp forests of oceans and seagrass meadows of coastal Mediterranean Sea, are irreplaceable habitats for some fish, mollusks and crustacean, as well as nursery grounds for many commercial species during breeding season. The three dimensional structure gives way to a complex habitat with macro species living on the surface accompanied by countless tiny organisms in micro habitats woven within. This complexity and richness is one of the reasons it has been placed under protection in the Mediterranean Biodiversity Protocol; each country is required to have their own action plan for this species. They have recently been included in the IUCN’s Red List with status updated to insufficient data.
Many a beautiful marine organism, such as sponges, corals, bryozoans and the Cyprus Bearded Fire worm (Hermodice carunculata) on the left can be observed living on corallines. Many more remain hidden in the micro habitats within corallines. Some of these species are under protection.
Hacelia attenuata starfish amongst yellow sponges and a typical Thalia species, Halocynthia papillosa living on corallines.
Our country has insufficient scientific research despite the ecological and economic importance of marine regions. Typical organisms of the Mediterranean, corallines live on the coasts of Aegean and Mediterranean as well as the Marmara Sea. Western Mediterranean corallines are usually gorgonians, also known as sea fans, with soft skeletons and collagen-like material, and other soft corals, while the Eastern Mediterranean Basin including our country has more sponges and bryozoans. A considerable number of 60 species of anthozoans in the Marmara Sea lives in coralline habitats and some are dominant species (Topçu and Özalp 2016). Sea fans are dominant corallines in some unique areas such as the Ayvalık Region Saros Bay, Bodrum coasts and Gökçeada (Topçu 2015).
Yellow sea fan Eunicella cavolini is a widely distributed sea fan and sometimes observed as meadows.
Above is a colony with the white sea fan Eunicella singularis as the dominant species.
The purple sea fan Paramuricea clavata, rarely seen in the eastern Mediterranean, can be observed amongst the Marmara Sea corallines. Sadly, this beautiful creature is getting rarer by the second. It has recently been classified as ‘vulnerable’ in the Mediterranean but speeches to be a meadow-forming species in the 1990’s (Öztürk and Bourguet, 1990).
Similarly, soft red coral Alcyonim acaule can be observed amongst the Mediterranean corallines.
THREATS AND CONSERVATION
Coralline communities are threatened by many factors such as coastal fisheries, pollution, coastal destruction, sand theft, turbidity, diving activities and global climate change. Extreme temperatures in the Mediterranean in recent years, especially towards the end of summer, cause abnormally high seasonal water temperatures and mass deaths in various marine organisms living on corallines (Garrabou et al. 2009). For this reason, corallines have been placed in the EU Marine Habitat Red List. An ‘action plan for the protection of Mediterranean corallines and other calciferous biological structures’ has been proposed within the Barcelona Convention for the protection and monitoring of the reefs (UNEP-MAP-RAC/SPA, 2008).
One of the marine organisms affected by high water temperatures observed at the end of summer is the stony coral Cladocora caespitose. White spots on the colony indicates the presence of dead tissues (Güreşen et al. 2015).
A coralline algae colony with large numbers of yellow sea fan Eunicella cavolini has recently been destroyed due to anthropogenic sedimentation (Topçu et al. 2019).
WHAT SHOULD WE DO?
Scientific understanding, observation and data gathering of all surrounding seas is an obligation and a responsibility. Action plans for the conservation of a species will always be deficient in the absence of proper research and reliable data. Joint action for eastern and southern Mediterranean including our coasts must be taken to protect the coralline reefs, symbolic structures of the Mediterranean.
In this regard, our foundation has published a Marine Caves book in 2019 that included corallines. Colonies with a heavy presence of sea fans (gorgonians) have also been studied demographically and are being monitored.
We provide data to relevant organizations for the protection of this species and raise awareness by informing future generations about marine biodiversity. Join us by sharing your observations on the subject: Have you noticed a degradation in coralline colonies? Please inform us if you’ve noticed a discoloration in the normally colorful coralline colonies or deterioration in sponges, or peeling coral branches. Contribute through citizen science by sharing this information.
Garrabou, J., Coma, R., …, Cerrano, C., 2009, Mass mortality in Northwestern Mediterranean rocky benthic communities: effects of the 2003 heat wave, Global Change Biology 15, 1090-1103.
Güreşen S. O., Topçu E.N., Öztürk B., 2015. Distribution and mortality of the Mediterranean Stony Coral (Cladocora caespitosa Linnaeus, 1767) around Gökçeada Island (Northern Aegean Sea). Cahiers de Biologie Marine 56 : 283-288.
Öztürk B., Bourguet J.P., 1990, Données préliminaires sur le corail noir de la Mer de Marmara (Turquie) Gerardia savaglia (Bertolini, 1819), Istanbul University Journal of Fisheries 4: 45-48.
Topçu N. E. 2015. Antohozoans of the Aegean Sea, in: Tuncer Katagan, Adnan Tokaç, Sükrü Besiktepe, Bayram Öztürk (eds.) The Aegean Sea; Marine Biodiversity, Fisheries, Conservation and Governance. Istanbul: TÜDAV publ. No 41; 713 pages; pp 200 – 205.
Topçu Nur Eda, Özalp Hasan Baris 2016. Anthozoans of The Sea Of Marmara in: Emin Özsoy; M. Namık Çagatay; Neslihan Balkıs; Nuray Balkıs; Bayram Öztürk (Eds.) The Sea of Marmara, Marine Biodiversity Fisheries Conservation and Governance. Türk Deniz Arastırmaları Vakfı yayınları No 42, 957 pages; pp 428 – 448.
Topçu NE, Turgay E, Yardımcı RE, Topaloğlu B, Yüksek A, Steinum TM, Karataş S, Öztürk B (2019). Impact of excessive sedimentation caused by anthropogenic activities on benthic suspension feeders in the Sea of Marmara. Journal of the Marine Biological Association of the United Kingdom 99(5): 1075-1087.
UNEP-MAP-RAC/SPA, 2008, Action plan for the conservation of the coralligenous and other calcareous bio-concretions in the Mediterranean Sea, RAC/SPA, Tunis.