Composition of abyssal macrofauna along the Vema Fracture Zone and the hadal Puerto Rico Trench, northern tropical Atlantic

Abstract

We analyzed composition and variations in benthic macrofaunal communities along a transect of the entire length of the Vema-Fracture Zone on board of RV Sonne (SO-237) between December 2014 and January 2015 in order to test whether the Mid-Atlantic Ridge serves as a barrier limiting benthic taxon distribution in the abyssal basins on both sides of the ridge or whether the fracture zone permits the migration of species between the western and eastern abyssal Atlantic basins. The Puerto Rico Trench, much deeper than the surrounding abyssal West Atlantic, was sampled to determine whether the biodiversity of its hadal macrofauna differs from that of the abyssal Atlantic. The composition of the macrofauna from the epibenthic sledge catches yielded a total of 21,332 invertebrates. Crustacea occurred most frequently (59%) with 12,538 individuals followed by Annelida (mostly Polychaeta) (26%) with 5,491 individuals, Mollusca (7%) with 1,458 individuals, Echinodermata (4%) with 778 individuals, Nematoda (2%) with 502 individuals and Chaetognatha (1%) with 152 and Porifera (1%) with 131 individuals. All other taxa occurred with overall less than ten individuals (Hemichordata, Phoronida, Priapulida, Brachiopoda, invertebrate Chordata, Echiurida, Foraminifera (here refereed to macrofaunal Komokiacea only), Chelicerata, Platyhelminthes). Within the Crustacea, Peracarida (62.6%) with 7,848 individuals and Copepoda (36.1%) with 44,526 individuals were the most abundant taxa. Along the abyssal Vema-Fracture Zone macrofaunal abundances (ind./1,000 m 2) were generally higher on the eastern side, while the highest normalized abundance value was reported in the Puerto Rico Trench at abyssal station 14-1 2,313 individuals/1,000 m 2. The lowest abundance was reported at station 11-4 with 120 ind./1,000 m 2 located at the western side of the Vema-Fracture Zone. The number of major macrofaunal taxa (phylum, class) ranged between five (stations 12-5, 13-4 and 13-5 at hadal depths in the Puerto Rico Trench) and 14 (station 9-8) in the western abyssal basin of the Vema-Fracture Zone. Differences are seen in the distribution of Porifera at macrofaunal level between eastern and western sides of the Vema-Fracture Zone. Macrofaunal composition of the study area is compared with data from other expeditions in the Atlantic and the northwest Pacific Ocean.

Megafaunal Community Structure From the Abyssal to Hadal Zone in the Yap Trench

“…Additionally, Hemichordata and Ctenophora were also firstly reported in the Yap Trench. Hemichordata is a prominent member of the epibenthic community in the deep sea (Osborn et al, 2011), which has been reported from several hadal trenches in both the Pacific and Atlantic Ocean (Jamieson, 2015;Brandt et al, 2018). Besides the single observation of Hemichordata, many of their traces were observed majorly from the surface of sediment, just as previous observations (Heezen and Hollister, 1971;Lemche et al, 1976;Gallo et al, 2015).…”

“…Our observations showed that benthic sessile fauna, such as sponges and actiniarians, were mostly restricted to hard or mixed substrates, whereas small crustaceans such as mysids, amphipods, and munnopsids dominated the sedimentary seafloor ( Figure 7B). A trend of reduction in the munnopsid abundance from abyssal to hadal depths was revealed in the Puerto-Rico Trench and Kuril-Kamchatka Trench (Brandt et al, 2018;Malyutina and Brandt, 2020). In contrast, the abundance of munnopsids increased with depth in the Yap Trench, which may be attributed to the higher sediment coverage in the hadal zone.…”

“…Since the early 2000s, multiple projects such as the UK-Japan HADEEP, US-UK-NZ HADES (Jamieson et al, 2009b) and German-Russian expedition KuramBio II (Brandt et al, 2018) have been carried out to fill this knowledge gap, particularly from a biological perspective. Hadal landers provide a time/cost effective way of exploring the deep-sea biological community, such as the first report of decapods in the hadal zone (Jamieson et al, 2009a), a large aggregation of hadal fish (Fujii et al, 2010;Linley et al, 2016), a better understanding of the amphipod community (Jamieson, 2015;Lacey et al, 2016Lacey et al, , 2018, and the first reliable report of a hadal cephalopod (Jamieson and Vecchione, 2020).…”

Integrative systematics and ecology of a new deep-sea family of tanaidacean crustaceans

“…Recently, more material was collected on board RV Meteor in 2011 during the Icelandic Animals Genetic and Ecology (IceAGE) program in waters of Iceland 22 , and on board RV Sonne , in 2014/2015 on both sides of the Mid-Atlantic Ridge at the Vema Fracture Zone during the Vema-TRANSIT project 23 , and in 2015 from the Central Pacific within the framework of the Joint Programming Initiative Healthy and Productive Seas and Oceans platform (JPI Oceans) 24 . That material was collected, fixed and handled following protocols for fixation as described in Riehl et al .…”

Recent speciation and hybridization in Icelandic deep-sea isopods: an integrative approach using genomics and proteomics

“…Deep-sea benthos fosters a high diversity of invertebrates with peracarid crustaceans like Isopoda being particularly species-rich (Wilson & Ahyong, 2015;Brandt et al, 2018). The underlying factors that shaped this diversity and the potential role of past climatic changes or physical barriers, such as deep-sea ridges, are not well understood.…”