Identification and Diversity of Deep-sea Sponges (Porifera) from The Denmark Strait : A Taxonomic Study

Porifera is a highly diverse phylum that can be found all over our planet, being particularly important in the deep-sea. Deep-sea sponges serve a great purpose for the welfare of many other organisms, providing ecosystem services such as habitat, nutrient recycling, and food sources. They are also exposed to several anthropogenic disturbances such as trawling and climate change which increases the conservation interests regarding this group. Despite this, there is a huge knowledge gap regarding the diversity of deep-sea sponges, their abundance, as well as their distribution. One location where this is the case is in the Denmark Strait and around Iceland. The deep-sea in these regions has a unique oceanographic setting with cold Arctic waters and warm Atlantic saline waters, which allows for a great diversity of benthic communities. By examining the spicule content as well as sequencing the COI marker of specimens from the Icelandic AS11-2016 cruise, the diversity of boreo-arctic deep-sea sponges could be investigated. With the help of spicules, the classes Hexactinellida and Demospongiae were identified, as well as nine different demosponge orders. Demospongiae was the largest part of this collection, and the most abundant order was Tetractinellida. Amongst these nine orders, 52 different species were identified. With COI barcoding, a subset of specimens could be determined either to species level or identified further than with morphology. This study sheds light on the diversity of Porifera that exists in the deep-sea of the Denmark Strait and around Iceland. The diversity and rarity of some species that were found highlight the conservation value for this area, making this study particularly important regarding the distribution and diversity of deep-sea sponges.