Atlas of Benthic Foraminifera from Cold-Water Coral Reefs
Cold-water coral reef ecosystems occur worldwide and are especially developed along the European margin, from northern Norway to the Gulf of Cadiz and into the western Mediterranean Sea. Their widespread occurrence presents a challenge to understand their development, preservation and possible importance in the geologic record.
The dominant reef-building scleractinian coral Lophelia pertusa settles on suitable hard substrates, in environments characterized by elevated currents and high food availability. Along the European margin these cold-water coral reefs grew during different times and with different morphologies. Extended living reefs developed on elevated hard substrates along the upper slope of the Norwegian shelf, whereas large carbonate mounds were built-up by L. pertusa along the Irish margin (Rockall and Porcupine Bank, Porcupine Seabight) and in the Gulf of Cadiz.
The cold-water coral reefs provide important ecological niches for the marine benthic fauna in the present ocean, they are considered as ‘hot spots’ of biodiversity. In comparison to the macrofauna, the microfauna, particularly the foraminifers associated with these ecosystems, are poorly known.
We present here the last ~12 years of our studies on foraminiferal assemblages associated with cold-water coral ecosystems along the European continental margin and in the Mediterranena Sea. The sub-Recent benthic foraminifera] assemblages in the Porcupine/Rockall region on the Irish margin and along the Norwegian coasts are strictly related to environmental parameters and on the distribution of different sedimentary facies. In particular, benthic assemblages from these ecosystems indicate that their living strategies and microhabitats are very similar, although species composition may vary, and that cold-water coral reef associated benthic fauna and non-reef associated fauna are remarkably different. However, in the Porcupine Seabight both microhabitats and facies can develop over hundreds of meters, whereas, along the Norwegian margin they can change within meters.
Benthic foraminiferal assemblages from cold-water coral reefs show similarities between those of Holocene sediments from the Alboran Sea and Lopphavet, and those of Recent/sub-Recent sediments from the Porcupine/Rockall Bank and the Norwegian margin. Assemblages are dominated by epifaunal-attached species such as Discanomalina coronata, Cibicides refulgens, and Lobatula lobatula, but also infaunal foraminifera such as Trifarina angulosa, Globocassidulina spp., Epistominella spp., Cassidulina spp. are highly abundant. In particular, the benthic fauna associated with cold-water coral ecosystems is typical of an environment characterized by high energy, well oxygenated waters and high organic matter supply derived from phytoplankton blooms reaching the seafloor. Based on these observations the benthic fauna is interpreted to require similar ecological conditions to cold-water corals. In conclusion, our data suggest that, although cold-water coral ecosystems occur at different latitudes, the associated foraminiferal assemblages are consistent from Norway to the Western Mediterranean. Thus, they can be used to identify these ecosystems even in the geologic record, when the corals are often strongly dissolved like in the Alboran Sea.
Selected species of benthic foraminifera including those poorly reported in the literature are documented in 37 plates.
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