Stylasterid Corals Research Articles

Ba/Ca of stylasterid coral skeletons records dissolved seawater barium concentrations

The concentration of dissolved barium in seawater ([Ba]SW) is influenced by both primary productivity and ocean circulation patterns. Reconstructing past subsurface [Ba]SW can therefore provide important information on processes which regulate global climate. Previous Ba/Ca measurements of scleractinian and bamboo deep-sea coral skeletons exhibit linear relationships with [Ba]SW, acting as archives for past Ba cycling. However, skeletal Ba/Ca ratios of the Stylasteridae – a group of widely distributed, azooxanthellate, hydrozoan coral – have not been previously studied.Here, we present Ba/Ca ratios of modern stylasterid (aragonitic, calcitic and mixed mineralogy) and azooxanthellate scleractinian skeletons, paired with published proximal hydrographic data. We find that [Ba]SW and sample mineralogy are the primary controls on stylasterid Ba/Ca, while seawater temperature exerts a weak secondary control. [Ba]SW also exerts a strong control on azooxanthellate scleractinian Ba/Ca. However, Ba-incorporation into scleractinian skeletons varies between locations and across depth gradients, and we find a more sensitive relationship between scleractinian Ba/Ca and [Ba]SW than previously reported.Paired Sr/Ca measurements suggest that this variability in scleractinian Ba/Ca may result from the influence of varying degrees of Rayleigh fractionation during calcification. We find that these processes exert a smaller influence on Ba-incorporation into stylasterid coral skeletons, a result consistent with other aspects of their skeletal geochemistry. Stylasterid Ba/Ca ratios are therefore a powerful, novel archive of past changes in [Ba]SW, particularly when measured in combination with temperature sensitive tracers such as Li/Mg or Sr/Ca. Indeed, with robust [Ba]SW and temperature proxies now established, stylasterids have the potential to be an important new archive for palaeoceanographic studies.

Stylasterid corals build aragonite skeletons in undersaturated water despite low pH at the site of calcification

Anthropogenic carbon emissions are causing seawater pH to decline, yet the impact on marine calcifiers is uncertain. Scleractinian corals and coralline algae strongly elevate the pH of their calcifying fluid (CF) to promote calcification. Other organisms adopt less energetically demanding calcification approaches but restrict their habitat. Stylasterid corals occur widely (extending well below the carbonate saturation horizon) and precipitate both aragonite and high-Mg calcite, however, their mode of biocalcification and resilience to ocean acidification are unknown. Here we measure skeletal boron isotopes (δ11B), B/Ca, and U/Ca to provide the first assessment of pH and rate of seawater flushing of stylasterid CF. Remarkably, both aragonitic and high-Mg calcitic stylasterids have low δ11B values implying little modification of internal pH. Collectively, our results suggest stylasterids have low seawater exchange rates into the calcifying space or rely on organic molecule templating to facilitate calcification. Thus, despite occupying similar niches to Scleractinia, Stylasteridae exhibit highly contrasting biocalcification, calling into question their resilience to ocean acidification.

Facies character and skeletal composition of heterozoan carbonates in a high-energy confined embayment (Miocene, Finale Ligure Limestone, NW Italy)

During the early and middle Miocene, diverse photozoan to heterozoan carbonate and mixed carbonate-siliciclastic depositional systems characterized the Mediterranean region at palaeo-latitudes of 30–40°N, during a time of warm climate. These systems ranged from carbonate ramp to rimmed platforms to current-swept flooded incised palaeo-valleys, seaways and straits. This study focuses on the facies character, skeletal biota composition, diagenesis and stable carbon and oxygen isotope signature of a mixed carbonate-siliciclastic succession (lower-middle Miocene Finale Ligure Limestone and underlying Oligocene-lower Miocene siliciclastic deposits) accumulated in a high-energy coastal setting (Finale Ligure, NW Italy) to improve the knowledge on the variety and controlling factors of Miocene heterozoan skeletal carbonates.The 3D reconstruction of the geometry of the early-middle Miocene Finale Ligure basin identifies an embayment, about 35 km2 wide, limited by uplifted and eroded Alpine tectonic units and connected to the open sea through a strait. The Oligocene-Miocene sedimentary succession unconformably overlying the Alpine deformed substrate consists of 14 lithofacies (L1-L14). Besides pockets of karstic breccias (L1) preceding the marine transgression, discontinuous outcrops of glaucony-bearing litharenite, siltstone, conglomerate and wackestone/packstone with planktonic foraminifera (L2-L4) represent the preserved remnants of an eroded marine shelf affected by tectonic uplift and subsequent erosion, approximately in the Aquitanian-Burdigalian, overlain through an angular unconformity by transgressive conglomerates and bioturbated litharenites (L5-L7). The onset of carbonate skeletal production characterizes the overlying compositionally mixed carbonate-siliciclastic Langhian-Serravallian Finale Ligure Limestone succession (up to 100–150 m thick, L8-L14). These cross-bedded skeletal packstone and grainstone/rudstone are composed of barnacles, echinoderms, bryozoans, bivalves, scleractinian and stylasterid corals, and lack halimedacean algae as previously published. They accumulated in a high-energy setting with strong bottom currents, driven by the amplification of tidal and/or storm currents in a confined embayment, promoting the formation of seaward prograding metre-scale subaqueous dunes.Unlike other lower-middle Miocene carbonate systems, the Finale Ligure heterozoan carbonates contain rare coralline red algae and larger benthic foraminifera but are enriched in barnacles, scleractinian and stylasterid corals. The coastal palaeo-environmental conditions, with hard rocky substrates, strong bottom currents, high nutrients and water turbidity, influenced the composition of the skeletal carbonate producers. These distinctive lithofacies character and composition resulted from the confined embayment morphology inherited from the marine flooded Alpine bedrock that was subjected to land runoff driving nutrient input.

Distribution of deep-water scleractinian and stylasterid corals across abiotic environmental gradients on three seamounts in the Anegada Passage

In the Caribbean Basin the distribution and diversity patterns of deep-sea scleractinian corals and stylasterid hydrocorals are poorly known compared to their shallow-water relatives. In this study, we examined species distribution and community assembly patterns of scleractinian and stylasterid corals on three high-profile seamounts within the Anegada Passage, a deep-water throughway linking the Caribbean Sea and western North Atlantic. Using remotely operated vehicle surveys conducted on the E/V Nautilus by the ROV Hercules in 2014, we characterized coral assemblages and seawater environmental variables between 162 and 2,157 m on Dog Seamount, Conrad Seamount, and Noroît Seamount. In all, 13 morphospecies of scleractinian and stylasterid corals were identified from video with stylasterids being numerically more abundant than both colonial and solitary scleractinians. Cosmopolitan framework-forming species including Madrepora oculata and Solenosmilia variabilis were present but occurred in patchy distributions among the three seamounts. Framework-forming species occurred at or above the depth of the aragonite saturation horizon with stylasterid hydrocorals being the only coral taxon observed below Ωarag values of 1. Coral assemblage variation was found to be strongly associated with depth and aragonite saturation state, while other environmental variables exerted less influence. This study enhances our understanding of the factors that regulate scleractinian and stylasterid coral distribution in an underreported marginal sea and establishes a baseline for monitoring future environmental changes due to ocean acidification and deoxygenation in the tropical western Atlantic.

Stylasterid corals: A new paleotemperature archive

Stylasterids are a ubiquitous deep-sea coral taxon that build their skeletons from either calcite, aragonite, or both. Yet, robust geochemical proxy data from these corals are limited. In this study, 95 modern stylasterids, spanning a wide range of depths (63 to 2894 m) and ambient seawater temperatures (0 to 17°C), were tested for their potential use as paleoceanographic archives. Stable oxygen and carbon isotopic composition (δ18O and δ13C) were measured from the main trunk of all specimens and five specimens were further sub-sampled to assess internal chemical variability. The isotope data show non-equilibrium precipitation from seawater for both δ18O and δ13C, with the growing tips of colonies yielding the isotopically lowest values. Overall, the calcitic corals showed lower isotope values for δ18O and δ13C than aragonitic specimens. Within the aragonite corals, we present a δ18O:temperature calibration that exhibits a significant linear relationship with the equation δ18Ocoral-seawater = −0.22(±0.01)×T(°C) + 3.33(±0.06) across a temperature range of 0 to 30°C, using samples from this study and published data. This work highlights the potential application of stylasterid coral δ18O data to reconstruct paleo seawater temperature.

Refining trace metal temperature proxies in cold-water scleractinian and stylasterid corals

The Li/Mg, Sr/Ca and oxygen isotopic (δ18O) compositions of many marine biogenic carbonates are sensitive to seawater temperature. Corals, as cosmopolitan marine taxa with carbonate skeletons that can be precisely dated, represent ideal hosts for these geochemical proxies. However, efforts to calibrate and refine temperature proxies in cold-water corals (<20°C) remain limited. Here we present skeletal Li/Mg, Sr/Ca, δ18O and carbon isotope (δ13C) data from live-collected specimens of aragonitic scleractinian corals (Balanophyllia, Caryophyllia, Desmophyllum, Enallopsammia, Flabellum, Lophelia, and Vaughanella), both aragonitic and high-Mg calcitic stylasterid genera (Stylaster and Errina), and shallow-water high-Mg calcite crustose coralline algae (Lithophyllum, Hydrolithon, and Neogoniolithon). We interpret these data in conjunction with results from previously explored taxa including aragonitic zooxanthellate scleractinia and foraminifera, and high-Mg calcite octocorals. We show that Li/Mg ratios covary most strongly with seawater temperature, both for aragonitic and high-Mg calcitic taxa, making for reliable and universal seawater temperature proxies. Combining all of our biogenic aragonitic Li/Mg data with previous calibration efforts we report a refined relationship to temperature: Li/MgAll Aragonite = 5.42exp⁡(−0.050×T(°C)) (R2=0.97). This calibration now permits paleo-temperature reconstruction to better than ±3.4°C (95% prediction intervals) across biogenic aragonites, regardless of taxon, from 0 to 30°C. For taxa in this study, aragonitic stylasterid Li/Mg offers the most robust temperature proxy (Li/MgStylasterid (Arag) = 5.64exp⁡(−0.046×T(°C)) (R2=0.95)) with a reproducibility of ±2.3°C. For the first time, we show that high-Mg calcites have a similar exponential relationship with temperature, but with a lower intercept value (Li/Mg = 0.63exp⁡(−0.050×T(°C) (R2=0.92)). This calibration opens the possibility of temperature reconstruction using high-Mg calcite corals and coralline algae. The commonality in the relationship between Li/Mg and temperature transcends phylogeny and suggests a similar abiogenic trace metal incorporation mechanism.

A New Distichopora Species (Cnidaria: Stylasteridae) from the Mesophotic Zone of Palau1

Stylasterid corals are widely distributed in all oceans from the intertidal zone to the deep sea. They are habitat-forming species, reaching high densities and establishing a wide range of associations with other taxa. In the last decades, many new deep-water stylasterids have been described and the faunas of several regions of the globe have been revised; however, the tropical Pacific Ocean remains relatively understudied. In this paper, a new mesophotic species of Distichopora, D. cryptostylus, is described from the Republic of Palau, Caroline Islands. The new Distichopora is distinguished from congenerics by its uniquely shaped coenosteal pores, a paucity of dactylostyles, and apical dactylotomes.

Large‐Scale Intrusion of Circumpolar Deep Water on Antarctic Margin Recorded by Stylasterid Corals

AbstractWe present centennial‐scale radiocarbon (14C) records archived by deep sea stylasterid corals from the outer shelf and upper slope of the Antarctic margin. These novel stylasterids (Errina spp.) were collected from the western Ross Sea shelf (500 m) and slope (1,700 m), as well as the eastern Wilkes Land shelf (670 m). We provide two corals from each region and document an abrupt reversal of 14C ages in the upper (younger) part of each coral. We test the statistical robustness of each record and demonstrate the significance of the age reversals, as well as the ability of these corals to record environmental change. We discuss a variety of possible drivers for this 14C reversal and conclude that it is most likely an encroachment of 14C‐depeleted Circumpolar Deep Water (CDW). This water mass has regionally intruded onto the Antarctic margin in recent decades, facilitating loss of grounded Antarctic ice; which has implications for global sea level, deep‐water formation, and carbon sequestration in the Southern Ocean. Thus, understanding the past variability of CDW on the margin is vital to better constrain climate change trajectories in the near future. We estimate large‐scale encroachment of CDW onto the shelf likely commencing after 1830 CE (±120 year). We present possible drivers for the intrusion, but highlight the need for additional chronologic constraint. This study not only demonstrates the utility of a novel coral taxon but also presents the paleoceanographic community with a testable hypothesis concerning a recent, widespread CDW intrusion.

First Record ofLepidopora(Hydrozoa: Stylasteridae) from the North Pacific Ocean with Description of a New Species

Abstract: Stylasterid corals from the North Pacific Ocean have been well studied and revised only in the Northeastern Temperate Region and in the tropical area around the Hawai‘i archipelago. However, few studies concerning stylasterids have been conducted in the Japanese region, and the number of species (including subspecies) known for the area is 26. Here we describe a new species of genus Lepidopora, L. iwasakii Pica & Puce, n. sp., from the deep sea off the Ryukyu Islands (Japan). The new species is characterized by having gastropores and dactylopores randomly arranged, reticulate-granular to linear-imbricate texture, presence of ring palisade, and short dactylopore spines without dactylostyles. Moreover, in the Northern Hemisphere in the Pacific Ocean the genus Lepidopora is not listed among the 11 genera recorded so far. Therefore, L. iwasakii represents the first record of this genus from Japan and the entire North Pacific Ocean.

Microboring organisms in living stylasterid corals (Cnidaria, Hydrozoa)

ABSTRACTMicroboring or euendolithic microorganisms, which colonize and penetrate various carbonate substrates, are abundant in coral reef ecosystems and play a major role in reef carbonate dissolution. A few studies reported the presence of euendoliths in stylasterid coral skeletons but the biological identity, distribution and abundance of these microorganisms remain largely unknown. Observations of over 100 stylasterid colonies, collected in the Indo-Pacific area, revealed for the first time that the association between these corals and euendolith organisms appears to be quite common in shallow tropical waters. The most abundant euendolith was identified as a cryptic stage in the development of the rhodophyte Porphyra (Conchocelis stage). The euendoliths were observed in the skeletons of seven species of three genera (four Stylaster, two Distichopora and one Lepidotheca). The presence of euendoliths inside skeletons conferred a particular colour to the studied stylasterid corals. Distribution and abundance of microborings varied significantly among stylasterid species and among branches of a single colony and so did the colour of their skeletons. Colonization of skeletons and the associated colour distribution were almost uniform in some stylasterids, forming an upward gradually diminishing or sharply limited gradient. This study shows that patterns of euendolith colonization and growth in stylasterid skeletons may depend on the stage of the euendolith development as well as on their environmental requirements such as light exposure.

Southern hemisphere deep-water stylasterid corals including a new species, Errinalabrosa sp. n. (Cnidaria, Hydrozoa, Stylasteridae), with notes on some symbiotic scalpellids (Cirripedia, Thoracica, Scalpellidae).

A number of stylasterid corals are known to act as host species and create refuges for a variety of mobile and sessile organisms, which enhances their habitat complexity. These include annelids, anthozoans, cirripeds, copepods, cyanobacteria, echinoderms, gastropods, hydroids and sponges. Here we report the first evidence of a diverse association between stylasterids and scalpellid pedunculate barnacles and describe a new stylasterid species, Errina labrosa, from the Tristan da Cunha Archipelago. Overall, five stylasterid species are found to host eight scalpellid barnacles from several biogeographic regions in the southern hemisphere (Southern Ocean, temperate South America and the southern Indo-Pacific realms). There is an apparent lack of specificity in this kind of association and different grades of reaction to the symbiosis have been observed in the coral. These records suggest that the association between pedunculate barnacles and hard stylasterid corals has a wide distribution among different biogeographic realms and that it is relatively rare and confined largely to deep water.

Leptohelia flexibilis gen. nov. et sp. nov., a remarkable deep-sea stylasterid (Cnidaria: Hydrozoa: Stylasteridae) from the southwest Pacific.

Leptohelia flexibilis gen. nov. et sp. nov., the first stylasterid with a combined calcified and non-calcified skeleton, is described from seamounts and the slope off the islands of New Caledonia, in the southwestern Pacific. The new species is distinguished from all other species of the family Stylasteridae by having a non-calcified organic axis, internal to the basal portion of the calcified corallum. The internal axis is flexible and enclosed by a series of up to 10 calcified annuli, allowing passive lateral bending of the colony. Molecular phylogenetic analyses confirm that Leptohelia flexibilis is a stylasterid coral and reveal that the species is closely related to Leptohelia microstylus comb. nov., a southwestern Pacific stylasterid that lacks an internal axis.

Habitat Characterization, Distribution, and Areal Extent of Deep-sea Coral Ecosystems off Florida, Southeastern U.S.A.

Abstract. The deep-sea (200–1000 m) seafloor off the southeastern U.S. has a variety of extensive deep-sea coral ecosystem (DSCE) habitats including: deep-water coral mounds; various hard-bottom habitats off Florida including the Miami Terrace, Pourtales Terrace, and deep-water canyons (Agassiz and Tortugas Valleys); and deep island slopes off western Bahamas and northern Cuba. The dominant structure-forming scleractinian corals are Lophelia pertusa and Enallopsammia profunda; other structure-forming taxa include stylasterid corals, gorgonians, black corals, and sponges. This biota is associated with hard-bottom seafloor of variable high-relief topography which can be remotely identified from bathymetric data. NOAA bathymetric contour maps and digital elevation models were used to identify and delineate the areal extent of potential DSCE habitat in the region from northeastern Florida through the Straits of Florida. These were ground-truthed with 241 dives with submersibles and remotely operated vehicles ...

The association between a deep-sea gastropod Pedicularia sicula (Caenogastropoda: Pediculariidae) and its coral host Errina dabneyi (Hydrozoa: Stylasteridae) in the Azores

Abstract Braga-Henriques, A., Carreiro-Silva, M., Porteiro, F. M., de Matos, V., Sampaio, Í., Ocaña, O., and Ávila, S., P. 2011. The association between a deep-sea gastropod Pedicularia sicula (Caenogastropoda: Pediculariidae) and its coral host Errina dabneyi (Hydrozoa: Stylasteridae) in the Azores. – ICES Journal of Marine Science, 68: 399–407. The Azores region harbours the richest communities of stylasterid corals in the Northeast Atlantic area. Of the nine deep-water species found there, Errina dabneyi seems to be the most abundant species; it is commonly collected as bycatch from longline fishing. E. dabneyi host Pedicularia gastropods on their branches, and a detailed study of shell shape and morphometry at different growth stages, complemented by shell characterization through scanning electron microscopy, allows the individuals to be identified as Pedicularia sicula. The incidence of this species on E. dabneyi was high (69.8%), with abundances ranging between 1 and 223 individuals per colony. The pediculariids exhibited a high degree of plasticity and produced evident traces on the stylasterid skeletons at their fixation points, suggesting that they are ectoparasites and not predators of E. dabneyi. The stylasterid colonies also hosted a rich associated fauna dominated by suspension-feeders using the coral as substratum and for protection.

First evidence of a specific association between a stylasterid coral (Cnidaria: Hydrozoa: Stylasteridae) and a boring cyanobacterium

First evidence of a specific association between a stylasterid coral (Cnidaria: Hydrozoa: Stylasteridae) and a boring cyanobacterium

From offshore to onshore: multiple origins of shallow-water corals from deep-sea ancestors.

Shallow-water tropical reefs and the deep sea represent the two most diverse marine environments. Understanding the origin and diversification of this biodiversity is a major quest in ecology and evolution. The most prominent and well-supported explanation, articulated since the first explorations of the deep sea, holds that benthic marine fauna originated in shallow, onshore environments, and diversified into deeper waters. In contrast, evidence that groups of marine organisms originated in the deep sea is limited, and the possibility that deep-water taxa have contributed to the formation of shallow-water communities remains untested with phylogenetic methods. Here we show that stylasterid corals (Cnidaria: Hydrozoa: Stylasteridae)—the second most diverse group of hard corals—originated and diversified extensively in the deep sea, and subsequently invaded shallow waters. Our phylogenetic results show that deep-water stylasterid corals have invaded the shallow-water tropics three times, with one additional invasion of the shallow-water temperate zone. Our results also show that anti-predatory innovations arose in the deep sea, but were not involved in the shallow-water invasions. These findings are the first robust evidence that an important group of tropical shallow-water marine animals evolved from deep-water ancestors.

Cold-water coral reef frameworks, megafaunal communities and evidence for coral carbonate mounds on the Hatton Bank, north east Atlantic

Offshore banks and seamounts sustain diverse megafaunal communities, including framework reefs formed by cold-water corals. Few studies have quantified environmental effects on the alpha or beta diversity of these communities. We adopted an interdisciplinary approach that used historical geophysical data to identify topographic highs on Hatton Bank, which were surveyed visually. The resulting photographic data were used to examine relationships between megafaunal communities and macrohabitat, the latter defined into six categories (mud, sand, cobbles, coral rubble, coral framework, rock). The survey stations revealed considerable small-scale variability in macrohabitat from exposed Late Palaeocene lava flows to quiescent muddy habitats and coral-built carbonate mounds. The first reported evidence for coral carbonate mound development in UK waters is presented, which was most pronounced near present-day or former sites of topographic change, suggesting that local current acceleration favoured coral framework growth and mound initiation. Alpha diversity varied significantly across macrohabitats, but not between rock and coral rubble, or between smaller grain sized categories of cobbles, sand and mud. Community composition differed between most macrohabitats, and variation in beta diversity across Hatton Bank was largely explained by fine-scale substratum. Certain megafauna were clearly associated with particular macrohabitats, with stylasterid corals notably associated with cobble and rock habitats and coral habitats characterized by a diverse community of suspension-feeders. The visual surveys also produced novel images of deep-water megafauna including a new photographic record of the gorgonian coral Paragorgia arborea, a species not previously reported from Rockall Plateau. Further interdisciplinary studies are needed to interpret beta diversity across these and other environmental gradients on Hatton Bank. It is clear that efforts are also needed to improve our understanding of the genetic connectivity and biogeography of vulnerable deep-water ecosystems and to develop predictive models of their occurrence that can help inform future conservation measures.

A new species of Hexagonalia (Crustacea: Brachyura: Trapeziidae) from the Solomon Islands

ABSTRACT A new trapeziid crab species of the genus Hexagonalia Galil, 1986, whose congeners are typically symbiotic with stylasterid corals, is described from deep water off the Solomon Islands. Its association with a host remains unknown.

Distichopora robusta sp. nov., the first shallow-water stylasterid (Cnidaria: Hydrozoa: Stylasteridae) from the tropical eastern Pacific

Distichopora robusta, the first shallow-water stylasterid coral from the tropical eastern Pacific, is described from the west coast of Panama. The new species is distinguished from all species of Distichopora described thus far by having robust branches and poorly defined pore rows.

Alectona Species From North-Western Pacific (Demospongiae: Clionidae)

Alectona species which bore into the scleraxis of several colonies of Corallium elatius and the stem of a stylasterid coral, Distichopora sp. have been studied. The genus Alectona consists of rarely collected species. Five species, of the eight known for the genus, are here recorded. Two new species of Alectona sorrentini and A. microspiculata and one uncertain species are described.In recent reefs Cliona species are the predominant boring sponges while Alectona and Thoosa were common in the Eocene/Miocene coral reefs. The deep precious red coral communities of the western Pacific may be interpreted as refuge habitats of these ancient boring sponges.