Characterization and role of major deep-sea pennatulacean corals in the bathyal zone of Eastern Canada

Pennatulaceans (Octocorallia: Pennatulacea), commonly called sea pens, are colonial corals that typically anchor themselves into soft sediment (mud, sand), allowing them to colonize large areas of the sea floor from the intertidal zone down to the abyssal plain. Sea pens can occur sparsely or form large aggregations, suggesting that they may provide an important structural habitat to other organisms by increasing the complexity of the muddy seabed. The investigation of the three most common sea pens (Anthoptilum grandiflorum, Halipteris finmarchica and Pennatula aculeata) of the continental slope of Newfoundland and Labrador (Northwest Atlantic) showed different morphologies and adaptations to environmental parameters. Variations in their morphology were visible along bathymetric and latitudinal gradients, following food availability. This study identified different feeding strategies according to stable isotope signatures and macromorphologies (polyp diameter, colony length, shape). Different defense strategies were also identified based on the presence and localisation of sclerites in the tissues. Reproductive strategies were determined for A. grandiflorum and H. finmarchica, with both species presenting a seasonal spawning between April (Southern Newfoundland) and July/August (Labrador). The latitudinal shift in spawning followed the development of the surface phytoplankton bloom (i.e. sinking of phytodetritus). Low fecundity at the polyp level (13 and 6 oocytes polyp-1, respectively) yielded similar whole-colony fecundity in the two species (500-6000 oocytes colony-1). The measure of fecundity is discussed to highlight the importance of standardizing metrics (mature oocyte just before spawning) to avoid an overestimation of the fecundity and to allow comparison among species. Only ~20% of the oocyte matured in both species. The remaining oocytes in A. grandiflorum disappeared, indicating that oogenesis develops and culminates over 12 months. In H. finmarchica the persistence of the small oocytes indicates protracted oogenesis (>12 months). Finally, an analysis of the associated biodiversity showed that sea pens have relatively few associates but that they play an important role in their life history. Some associates are obligate (e.g. parasitic copepods) and others facultative symbionts (the sea anemone Stephanauge nexilis). The seasonal (April-May) presence of fish larvae (Sebastes spp.) and shrimp larvae (Pandalus borealis, Pasiphae multidentata and Acanthephyra pelagica) emphasize the role of sea pens as nursery habitat, and provides an argument to recognize them as an essential fish habitat

Diversity, Distribution and Nature of Faunal Associations with Deep-Sea Pennatulacean Corals in the Northwest Atlantic

Anthoptilum grandiflorum and Halipteris finmarchica are two deep-sea corals (Octocorallia: Pennatulacea) common on soft bottoms in the North Atlantic where they are believed to act as biogenic habitat. The former also has a worldwide distribution. To assist conservation efforts, this study examines spatial and temporal patterns in the abundance, diversity, and nature of their faunal associates. A total of 14 species were found on A. grandiflorum and 6 species on H. finmarchica during a multi-year and multi-site sampling campaign in eastern Canada. Among those, 7 and 5 species, respectively, were attached to the sea pens and categorized as close associates or symbionts. Rarefaction analyses suggest that the most common associates of both sea pens have been sampled. Biodiversity associated with each sea pen is analyzed according to season, depth and region using either close associates or the broader collection of species. Associated biodiversity generally increases from northern to southern locations and does not vary with depth (∼100–1400 m). Seasonal patterns in A. grandiflorum show higher biodiversity during spring/summer due to the transient presence of early life stages of fishes and shrimps whereas it peaks in fall for H. finmarchica. Two distinct endoparasitic species of highly modified copepods (families Lamippidae and Corallovexiidae) commonly occur in the polyps of A. grandiflorum and H. finmarchica, and a commensal sea anemone frequently associates with H. finmarchica. Stable isotope analyses (δ13C and δ15N) reveal potential trophic interactions between the parasites and their hosts. Overall, the diversity of obligate/permanent associates of sea pens is moderate; however the presence of mobile/transient associates highlights an ecological role that has yet to be fully elucidated and supports their key contribution to the enhancement of biodiversity in the Northwest Atlantic

Stable isotope values (δ¹⁵N and δ¹³C) for sea pens (Ag: <i>Anthoptilum grandiflorum</i> and Hf: <i>Halipteris finmarchica</i>) and their associated species (Lb: <i>Lamippe bouligandi</i>, Sn: <i>Stephanauge nexilis</i> and Uc: undescribed Corallovexiidae).

<p>To locate and compare the signature of the sea pens, values for other invertebrates are shown, Am: Amphipods, Eu: Euphausiids, Pm: <i>Pasiphae multidentata</i>, Pb: <i>Pandalus borealis</i> and Sc: snow crab from Sherwood & Ross <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111519#pone.0111519-Sherwood2" target="_blank">[42]</a>, as well as sedimentary organic matter (SOM) from Muzuka & Hillaire-Marcel <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111519#pone.0111519-Muzuka1" target="_blank">[41]</a>. Result shown as mean ± SE (n = 2–5). Black: <i>A. grandiflorum</i> and its associates, Blue: <i>H. finmarchica</i> and this associates, Grey: other invertebrates and SOM.</p

Associates of <i>Anthoptilum grandiflorum</i>: (A) decapod larva, (B) unidentified sp. 3, (C) unidentified sp. 1, (D) unidentified sp. 4, (E) unidentified sp. 2, (F) unidentified copepod.

<p>Unidentified sp. 1 to 4 correspond to potential egg mass. Associates of <i>Halipteris finmarchica</i>: (G) unidentified Lamippidae, (H and I) unidentified sp. 7. Scale bar in A = 200 µm, B, F and H = 500 µm, C and D = 2 mm, E = 4 mm, I = 100 µm. Species numbers linked to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111519#pone-0111519-t001" target="_blank">Table 2</a>.</p

Lunar Rhythms in the Deep Sea: Evidence from the Reproductive Periodicity of Several Marine Invertebrates

While lunar rhythms are commonly documented in plants and animals living in terrestrial and shallow-water environments, deep-sea organisms have essentially been overlooked in that respect. This report describes evidence of lunar periodicity in the reproduction of 6 deep-sea species belonging to 2 phyla. Occurrences of gamete release in free spawners and larval release in brooders exhibited significant peaks around the new and full moons, respectively. The exact nature of this lunar period (endogenous or exogenous rhythm) and its adaptive significance in the deep sea remain elusive. Current knowledge suggests that proxies of moon phases at depth may include fluxes in particulate matter deposition, cyclic currents, and moonlight for species living in the disphotic zone. </jats:p

Map showing the five geographic regions where colonies of the sea pens <i>Anthoptilum grandiflorum</i> and <i>Halipteris finmarchica</i> were collected along the continental slope.

<p>LC: Laurentian Channel, GB: Grand Banks, FC: Flemish Cap, NNL: North Newfoundland, LB: Labrador.</p