Cold-Water Soft Corals (Cnidaria: Nephtheidae) as Habitat for Juvenile Basket Stars (Echinodermata: Gorgonocephalidae)

Abstract

Nephtheidae soft corals are a common component of benthic ecosystems in the Northwest (NW) Atlantic and in the Arctic, but little is known about their functional roles. Here we investigated their role as habitat for basket stars (Ophiuroidea). By examining over 4500 soft coral colonies of Drifa glomerata, Duva florida, Gersemia spp., and Pseudodrifa racemosa collected during trawl surveys in the regions of Newfoundland, Labrador and West Baffin Bay, we show that Nephtheidae soft corals are habitat for juvenile Gorgonocephalus sp. basket stars. Juvenile Gorgonocephalus sp. were found on all soft corals species, but Drifa glomerata was the soft coral species with the highest occurrence of associated juvenile basket stars (32%), with a maximum of 111 basket stars found on a single 4.8 cm tall (contracted state) colony. Individual basket star disc diameter did not change with colony height, but it varied with season for individuals found on D. glomerata. On the other hand, colony height was positively related with maximum disc diameter (D. glomerata), and presence and number of basket stars on a colony (D. glomerata and D. florida). One very young ophiuroid was found within one polyp of a D. florida colony collected in July. We also examined bottom trawl survey data from 2011 to 2017 from Newfoundland to Baffin Bay, and other locations in the Eastern Canadian Arctic and found that for our largest database, 45% of trawl sets that contained basket stars also contained corals, of which 67% were Nephtheidae soft corals. In this study we show that all four Nephtheidae soft coral taxa studied act as habitat for juvenile basket stars, which are conspicuous components of benthic communities in cold-water environments. Soft corals are commonly exposed and vulnerable to bottom fishing gear in the North Atlantic. We urge future studies evaluating the nature of this relationship, the potential role of soft corals as nurseries, and the potential degree of dependency/preference between basket stars and soft corals in relation to other organisms.

Megabenthic biodiversity in culturally and ecologically important coastal regions of Northern Labrador

“…Soft corals reported in this study are known to provide habitat to juvenile basket stars (Gorgonocephalus sp. ; Neves et al 2020). In fact, juvenile basket stars were observed attached to soft coral colonies at several instances in the Nain archipelago, and the single observation of an errant basket star in this study was also reported there.…”

“…However, our in situ observations in Nain reinforce that co-occurrence rates might change spatially and that at this site Gersemia sp. might provide habitat to juvenile basket stars at potentially higher occurrence rates than those described by Neves et al (2020) based on physical specimens. Nephtheidae soft coral gardens have also been suggested for consideration as VME indicators (Long et al 2020).…”

“…In fact, juvenile basket stars were observed attached to soft coral colonies at several instances in the Nain archipelago, and the single observation of an errant basket star in this study was also reported there. Neves et al (2020) reported that among soft corals in the family Nephtheidae, Gersemia sp. was the taxon with the lowest cooccurrence with juvenile basket stars.…”

The Biodiversity of Calcaxonian Octocorals from the Irish Continental Slope Inferred from Multilocus Mitochondrial Barcoding

“…These gardens are important for the wider faunal community. They provide a significant structural role, as octocorals house unique commensal species on their branches [9], harbour eggs of charismatic species such as catsharks [10] and cephalopods [11], and act as a nursery for juvenile invertebrates, e.g., basket stars [12]. Many corals are slow-growing and long-lived, with radiocarbon ( 14 C) ageing of some individuals of Paramuricea sp.…”

Local ecological knowledge and multidisciplinary approach lead to discovery of hidden biodiversity in the deep ocean of Labrador, Canada

“…In some cases, vulnerable taxa can support elevated biodiversity (Cerrano et al 2010). For example, deepwater corals and sponges are habitat-forming species, modifying environmental conditions with their presence (Zedel and Fowler 2009) and creating foraging (Buhl- Mortensen 2004, Gale et al 2013), nursery (Aldrich and Lu 1968, Baillon et al 2012, Neves et al 2020, and refuge (Wulff 2006) areas for other taxa. At the same time, their sessile nature, fragile structures, and slow growth make them extremely vulnerable to disturbance from human activities, such as bottom-contact trawling, from which they can take decades or more to recover (Neves et al 2014).…”