Faunal biogeography, community structure, and genetic connectivity of North Atlantic seamounts

Abstract

The mechanisms of faunal dispersal across ocean basins are key unknowns toward understanding of the modern biogeography and biodiversity of deep-sea fauna. Seamounts are considered to play a defining role in faunal evolution, acting as regional centers of speciation, "stepping-stones" for dispersal, and/or refugia for deep-sea populations. The overarching goal of this dissertation was to examine the role of seamounts in structuring marine biodiversity and biogeography. This study focused on North Atlantic seamounts, specifically the New England seamount chain, the Corner Rise seamounts, and Muir seamount, areas damaged and threatened by deep-sea fisheries and currently a focus of conservation efforts. Videographic analyses of biological community structure revealed distinct faunal assemblages, dominated by the Porifera, Cnidaria, and Echinodermata and structured by geographic region, depth regions (with apparent taxonomic breaks at 1300 m, 2300 m, and 2600 m), and substrate type (including natural/anthropogenic and abiotic substrates and biotic substrates). Amongst these assemblages, seven highly specific coral host-invertebrate associate relationships were identified. To investigate whether or not these broad community patterns were discernible at a genetic level, the 16S mtDNA gene was utilized as a genetic "barcode" within the Class Ophiuroidea, through which 22 putative species were identified, including four target species (Asteroschema clavigera, Ophiocreas oedipus, Ophioplinthaca abyssalis, and Ophioplinthaca chelys) for subsequent population genetic studies. Analyses of mitochondrial 16S and COI gene sequences revealed evidence for recent population expansion and estimates of recent high gene flow across all four species throughout the North Atlantic seamount region. However, genetic differentiation within populations of A. clavigera and O. chelys within seamount regions was significant, suggesting that historical diversification has been mediated by a long-distance dispersal mechanism that homogenizes this genetic signal on a regional scale. In addition, comparisons of all ophiuroid populations revealed no congruent pattern of historical migration amongst seamounts, which may also be attributed to the varying levels of host specificity and reproductive strategy of each ophiuroid species. These results will guide future studies and conservation efforts to protect seamount communities vulnerable to deep-sea fishery activities.

First records of Geodia demosponges from the New England seamounts, an opportunity to test the use of DNA mini-barcodes on museum specimens

“…However, the fauna of the NES remained largely ignored until a series of Census of Seamounts (CENSEAM) campaigns in [2000][2001][2002][2003][2004][2005], part of the Census of Marine Life, began to collect and identify the fish and some invertebrates (Moore et al 2003b(Moore et al , 2004. These campaigns clearly confirmed with video analysis that Communicated by H. Stuckas suspension feeders dominate these seamounts; the most abundant phyla in the NES were by far Porifera (sponges) at 54%, followed by Cnidaria (mainly corals) at 23% (Cho 2008). These studies also supported the idea that these seamounts represented biodiversity hotspots, which needed protection from deep-sea fishing.…”

“…and Rossellidae sp., the demosponges Geodia sp., and Cladorhizidae sp. (Moore et al 2003b;Cho 2008). The closest formal sponge records (570-800 km away) are from the Challenger Expedition (1872-76), which dredged around the Bermuda islands some deep-sea temperate Tetractinellida demosponges-Geodia pachydermata Sollas, 1886 (st. 56: 1,966 m), Stelletta tenuispicula Sollas, 1886 (station unknown) and Leiodermatium pfeifferae Carter, 1873 (st. 33: 795 m;st.…”

Biodiversity of the Deep-Sea Continental Margin Bordering the Gulf of Maine (NW Atlantic): Relationships among Sub-Regions and to Shelf Systems

“…As a consequence of these expeditions, Bear Seamount is now comparatively well-sampled and characterized from a biological and physical perspective, although species accumulation curves suggest more taxa may still be discovered. Coral assemblages appear to be stratified by depth [65], but local endemics have not been found [60]. Several fish species found at Bear are rare in the northwest Atlantic, and some are only known from the eastern Atlantic [19], [64], [66].…”

Incongruent patterns of genetic connectivity among four ophiuroid species with differing coral host specificity on North Atlantic seamounts

“…To assess the specificity and abundance of these coral host‐epifaunal invertebrate relationships on seamounts, the distribution and host specificity of 22 ophiuroid morphospecies on the Northwestern Atlantic seamounts were surveyed via high‐definition video (Cho 2008). Markedly varying degrees of ophiuroid association with their coral hosts were identified.…”