WEBVTT
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Hello, my name is Meri Bilan and I'm a PhD
student from the University of Salento.
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My thesis is focused on the physiology and
ecology of cold-water corals from Blanes
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submarine canyon. In this presentation we
will discuss some general aspects of cold-
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water corals, their distribution, and look at some
colonies and communities from Blanes Canyon.
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So first of all, cold-water corals is a name
associated with a group of corals from
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all suborders that share some
characteristics laid down here.
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Firstly, they don't have zooxanthellae, the
symbiotic algae which we can find in
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tropical or temperate corals living in sunlit
coastal areas. This means that they are
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heterotrophs, actively acquiring food from
their environment, either as zooplankton
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or as marine snow from falling from the
euphotic zone. They thrive in cold waters
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between 4-12°C. Nevertheless, there are
some exceptions, like in the Mediterranean
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Sea, where the cold-water corals
are found at around 13.5°C.
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Due to their cold water preference, they are
often found in deeper parts of the ocean,
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below 200 metres depth where
sunlight is none or minimum.
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This is why they are also
called deep-sea corals.
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Of course this also has exceptions, for
example in the higher latitudes the
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cold-water corals can be
found from 40 metres depth.
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They are usually found in areas of relatively
high current speed that brings food,
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which we can find in submarine geomorphic
features such as seamounts or canyons.
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Since they live in cold waters, their
metabolism is slower compared to
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their shallow water cousins. Alongside
temperature, relatively scarce food is
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another possible reason why cold-water
corals develop certain life strategies.
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They are long-living. They live from several
decades to several thousands of years.
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They are slow-growing, usually
growing several millimetres per year.
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They have low fecundity and
they produce less larvae.
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These characteristics are important
in understanding their rarity, spatial
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distribution, connectivity between
populations, and ultimately, their
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resilience to anthropogenic
and environmental change.
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In order to get an idea where we can
find cold-water corals, we can use OBIS,
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which is Ocean Biodiversity Information
System, a depository providing diversity data.
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As we can see in this screenshot, I used
the filter for Anthozoa and a Depth filter
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for deeper than 200 metres. This
yielded more than 500,000 records.
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As you can see, there are some areas
where there there seems to be more corals,
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and in some areas there are less, but we
should keep in mind also that some areas
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of the deep ocean are better-explored.
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So for example, the Indian Ocean seems to
have fewer records, but it is also the least
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explored ocean in regards to deep sea,
and from the geomorphic characteristics
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of the Indian Ocean there are probably
many cold-water corals to be explored.
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More exploration is underway, and we are
expanding our knowledge on cold-water
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corals, and as we can see they are
very diverse and globally distributed.
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Cold-water corals are recognised as
animal forests, which is a concept that
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includes all benthic animals that provide
functional and structural complexity
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similar to trees or to terrestrial forests.
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They form extensive 3-dimensional
structures such as trees do, for
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example, mussel beds, coral reefs, coral
mounds, sponge grounds, et cetera.
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They all increase habitat complexity.
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Animal forests provide different services
for benthic and mobile animals, such as
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shelter for crustaceans, feeding and mating
grounds for fish or gastropods or ophiuroids
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suitable settlement for benthic organisms
such as anemones and bivalves.
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Considering the global distribution of cold-
water corals, these animal forests are
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frequent ecosystems in the deep sea and
that harbour high biodiversity and need
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to be adequately protected
for future generations.
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We recognise two main forms of animal
forest from cold-water corals, and these
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are coral gardens, usually formed by
octocorals and or black corals,
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and also coral mounds which are
characterised by scleractinian corals
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but there we can also find other animals
including different species of cold-water corals.
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Here we have some images from Blanes
Canyon, filmed in February 2020 during the
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ABRIC cruise. This is a black coral garden
dominated by the orange morph of
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Leiopathes glaberrima. On the wall you can
see here the solitary coral Desmophyllum
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dianthus that can provide additional
area for settlement and growth of corals.
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Here we have the monospecific garden of
Muriceides lepida, and their densities can
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vary depending on many
environmental factors.
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This is a garden of Callogorgia
verticillata, another deep-sea coral.
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And sometimes there can be mixed gardens
and here we can find, for example the
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Callogorgia verticillata, and
some black corals here and here,
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and there are some solitary
scleractinians here and here.
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They are quite impressive old animals.
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They are also under different anthropogenic
pressures such as fishing activities, where
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they can be accidentally caught during
fishing activities using nets or lines.
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This is also imagery from Blanes Canyon
filmed during the ABRIC cruise in February
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2020. These are scleractinian colonial
corals, mostly Madrepora oculata,
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and here we have Lophelia pertusa,
now called Desmophyllum pertusum
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and again the solitary
Desmophyllum dianthus.
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As we can see here we have for
example the bivalves, some shrimp,
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other octocorals - they are
quite diverse ecosystems.
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One important thing about these cold-water
scleractinians is that as they grow from here
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the older part of the colony dies. It still
maintains the calcium carbonate skeleton
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but it's not alive, while the apical part of
the colony stays alive and grows further.
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Therefore, they form these coral
mounds, which are quite important
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as biogenic calcium carbonate structures,
which can be used for settlement by other
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benthic organisms or shelter and feeding
grounds for some mobile animals, such as fish.
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So today we got introduced to the
characteristics of cold-water corals.
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We also had a look at OBIS global depository
of biodiversity data where you can find
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different information on the distribution of
species. We confirmed that cold-water corals
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are globally distributed, and we got
introduced to the animal forest concept,
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and we had a look at some cold-water
communities from Blanes Canyon,
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filmed during the ABRIC cruise
in 2020. Thank you for listening.