Family Isididae Research Articles

Reinterpreting radiocarbon records in bamboo corals – New insights from the tropical North Atlantic

Deep-sea bamboo corals (family Isididae) have been used as archives for reconstructing changes in the past ocean. However, uncertainties remain regarding the interpretation of geochemical signals from their organic nodes, specifically the water depth of the signals recorded by the coral. Here we explore this question by measuring radiocarbon (14C) and nitrogen (15N) isotopic compositions of the organic nodes in six bamboo corals collected from the central and eastern tropical Atlantic between 700 m and 2000 m water depth. By comparing coral 14C to measured seawater data, regional shallow-water coral records and climate-model outputs, we find contrasting results between the two regions. Our bamboo coral 14C results from the eastern tropical Atlantic support previous studies that suggest organic node carbon is sourced primarily from the mixed layer of the ocean. By contrast, the 14C of bamboo coral organic nodes from the oligotrophic central Atlantic better correlates with the 14C content of the subsurface deep chlorophyll maximum layer rather than the surface mixed layer. Combined with nitrogen isotope data, this observation suggests that sinking and/or ambient zooplankton feeding on phytoplankton from the deep chlorophyll maximum layer can contribute a significant proportion of the diet of bamboo corals. These results suggest that the carbon source for bamboo corals organic nodes may not always reside in the mixed layer, especially in oligotrophic regions, which has implications for 14C-based age model development in bamboo corals.

Octocorals (Alcyonacea and Pennatulacea) from Paleogene deep-water strata in western Washington State, USA

AbstractThe fossil record of octocorals from Cenozoic marine strata of western North America is quite limited, and they have not been reported previously from rocks in Washington State, USA. Two late Oligocene specimens from the upper part of the Lincoln Creek Formation in western Washington, referred to Radicipes? sp., are the first fossil record of the family Chrysogorgiidae. The family Isididae is represented by an internode and two holdfasts identified as Isidella sp. collected from the Oligocene Pysht Formation, along with specimens questionably identified as Lepidisis sp., possibly the first fossil record for this genus. Together, these are the first confirmed fossils of the Alcyonacea from north of California in western North America. The axes of sea pens from several late Eocene or early Oligocene localities in the Lincoln Creek Formation in the central part of western Washington, and the Pysht and Makah formations on the north side of the Olympic Peninsula, are the first fossil record for the Pennatulacea from western North America; all are tentatively referred to the genus ‘Graphularia’. Large axes from the Lincoln Creek Formation and Makah Formation are referred to ‘Graphularia’ (?) aff. sasai, because they are similar to the species known only from late Eocene and early Oligocene rocks in Japan.

Incorporation of Na and S in bamboo coral skeletons

Ocean environmental conditions can be inferred from the chemical composition of bamboo coral skeletons. The high magnesium calcite internodes of these long-living octocorals may therefore represent a potential archive for seawater properties such as salinity or temperature where instrumental time series are absent. To extend these time series into the past using a natural archive the principles of temperature and salinity signal incorporation into cold-water coral skeletal material need to be investigated. Since skeletal Na and S concentrations have been proposed as environmental proxies, we mapped the spatial distribution and concentration of these elements in two Atlantic specimens of Keratoisis grayi (family Isididae). These measurements were conducted with an electron microprobe applying a spatial resolution of 4 μm. The mean apparent distribution coefficient of Na/Ca for the two samples was within 2.5 and 2.8*10−4, while that of S shows a similar depletion relative to seawater with 3.8 and 3.6*10−3. The two elements show an inverse correlation in bamboo coral skeletons. The mean apparent distribution coefficient of Na is similar to that of abiotic calcites. This similarity can be interpreted as the absence of significant vital effects for skeletal Na/Ca. Hence it corroborates the idea that the average skeletal composition of bamboo corals holds the potential to record past seawater conditions. In contrast, it appears unlikely that the spatial variations of the element distribution of seemingly simultaneously precipitated material along growth rings are exclusively controlled by environmental factors. We further exclude Rayleigh fractionation, ion-specific pumping, and Ca/proton exchange as the driver of Na and S distribution in bamboo corals. Instead, we adapt a calcification model originally proposed for scleractinians to bamboo corals. This model can explain the observed distribution of Na and S in the skeleton by a combination of Ca/proton pumping, bicarbonate active transport, and the formation of an organic skeletal matrix. The adapted model can further be used to predict the theoretical behaviour of other elements and disentangle vital effects from external factors influencing compositional features. It is therefore a useful tool for future studies on the potential of bamboo corals as environmental archives.

Toward a revision of the bamboo corals: Part 3, deconstructing the Family Isididae.

Bamboo corals are distinguished from most other octocorals by an articulated skeleton. The nodes are proteinaceous and sclerite-free while the internodes are composed of non-scleritic calcium carbonate. This articulation of the skeleton was thought to be unique and a strong synapomorphy for the family Isididae. Our phylogeny, based on the amplification of mtMutS and 18S, shows an articulating skeleton with sclerite-free nodes has arisen independently at least five times during the evolutionary history of Octocorallia rather than being a synapomorphy characteristic of a monophyletic bamboo coral clade. The family Isididae is currently composed of four subfamilies (Circinisidinae, Isidinae, Keratoisidinae, and Mopseinae). Not only is the family polyphyletic, but our genetic analyses suggest also the subfamily Isidinae is polyphyletic based on current taxonomic classifications, and Mopseinae is not monophyletic. The type, Isis, is found outside of the well-supported Calcaxonia Pennatulacea clade where the other members of Isididae cluster. The current classification of the family Isididae does not reflect the evolutionary history of an articulated skeleton. To better reflect the evolutionary history of these taxa we propose that three of the four the subfamilies, the genus Isidoides, and genera within the subfamily Isidinae, be elevated to family level to produce a classification with five families with a bamboo-like skeleton: Chelidonisididae, Isididae, Isidoidae, Keratoisididae, and Mopseidae.

Toward a revision of the bamboo corals: Part 1, species in the Muricellisidinae (Octocorallia: Isididae).

The subfamily Muricellisidinae was erected by Kükenthal in 1915 and placed in the family Isididae in order to accommodate an unusual species collected in Sagami Bay, Japan. In 1931, Thomson and Dean added a second species collected in Indonesia during the Siboga Expedition. The holotypes of both species have been re-examined. Muricellisis echinata was found to be an anthothelid living on the axis of a keratoisid bamboo coral and M. cervicornis is a melithaeid. Both species are redescribed.

Novel diversity in mitochondrial genomes of deep-sea Pennatulacea (Cnidaria: Anthozoa: Octocorallia)

We present the first documented complete mitogenomes of deep-sea Pennatulacea, representing nine genera and eight families. These include one species each of the deep-sea genera Funiculina, Halipteris, Protoptilum and Distichoptilum, four species each of Umbellula and Pennatula, three species of Kophobelemnon and two species of Anthoptilum, as well as one species of the epi- and mesobenthic genus Virgularia. Seventeen circular genomes ranged from 18,513 bp (Halipteris cf. finmarchica) to 19,171 bp (Distichoptilum gracile) and contained all genes standard to octocoral mitochondrial genomes (14 protein-coding genes, two ribosomal RNA genes and one transfer RNA). We found at least three different gene orders in Pennatulacea: the ancestral gene order, the gene order found in bamboo corals (Family Isididae), and a novel gene order. The mitogenome of one species of Umbellula has a bipartite genome (∼13 kbp and ∼5 kbp), with good evidence that both parts are circular.

Incidence of disturbance and damage to deep-sea corals and sponges in areas of high trawl bycatch near the California and Oregon border

We evaluated disturbance and damage to deep-sea corals and sponges (DSCS) in areas of longtime (> 65 years) bottom trawling off southern Oregon and northern California. The incidence of disturbance was quantified from video and still images collected along strip transects conducted with underwater vehicles operating at depths of 600–2100m. All DSCS were identified, counted, and measured, condition (healthy, unhealthy, or dead) was determined, and associated seafloor substratum types were designated. Physical disturbance and damage were classified as DSCS with broken or missing parts, overturned, or detached from the seafloor. Overall frequency of disturbance to DSCS throughout the study area was 2% of the total number observed; most of these were coral colonies while sponges were rarely damaged. There was notable disturbance to corals, particularly to bamboo corals of the family Isididae (45% of 873 colonies were impacted), at depths of 1100–1150m in our most northern study site off southern Oregon and the southern site off Cape Mendocino, California. Nearly 20% (n = 78) of disturbed bamboo corals were sheared off at the base, leaving only small stumps to be counted. Height of intact undisturbed bamboo coral colonies ranged from 5 to 185cm. The Mendocino Ridge area had the highest incidence of coral bycatch in research bottom trawls conducted between 2001 and 2015. Using visual survey tools, we now have a better understanding of the extent of damage and disturbance to DSCS. Conservation areas have been implemented off the U.S. West Coast to protect seafloor habitats, but DSCS in our study site remain vulnerable to impacts from bottom-contact fishing gears.

Bamboo corals from the abyssal Pacific:Bathygorgia

Abstract Deep-sea bamboo corals (Family Isididae: subfamily Keratoisidinae) are a widely distributed group of gorgonian octocorals, commonly found in the deep sea below 200 m, with the deepest specimen to date collected at 4700 m. Two specimens were collected from the seamounts off Tasmania at depths of 3065 to 3950 m. In situ high-definition images, compound microscopy of preserved specimens, and Scanning Electron Microscopy (SEM) provided morphological data on distinguishing morphological characters such as colony shape and branching pattern, polyp arrangement, composition of the axial skeleton, and shape and arrangement of the sclerites. The genus Bathygorgia Wright, 1885 is resurrected and distinguished from Keratoisis, and two new species, B. abyssicola and B. tasmaniensis are added.

Evidence for benthic–pelagic food web coupling and carbon export from California margin bamboo coral archives

Abstract. Deep-sea bamboo corals (order Gorgonacea, family Isididae) are known to record changes in water mass chemistry over decades to centuries. These corals are composed of a two-part skeleton of calcite internodes segmented by gorgonin organic nodes. We examine the spatial variability of bamboo coral organic node 13C/12C and 15N/14N from 13 bamboo coral specimens sampled along the California margin (37–32° N, 792–2136 m depth). Radiocarbon analyses of the organic nodes show the presence of the anthropogenic bomb spike, indicating the corals utilize a surface-derived food source (pre-bomb D14C values of ∼−100‰, post-bomb values up to 82‰). Carbon and nitrogen isotope data from the organic nodes (δ13C = −15.9‰ to −19.2‰; δ15N = 13.8‰ to 19.4‰) suggest selective feeding on surface-derived organic matter or zooplankton. A strong relationship between coral δ15N and habitat depth indicates a potential archive of changing carbon export, with decreased δ15N values reflecting reduced microbial degradation (increased carbon flux) at shallower depths. Using four multi-centennial-length coral records, we interpret long-term δ15N stability in the California Current. Organic node δ15C values record differences in carbon isotope fractionation dictated by nearshore vs. offshore primary production. These findings imply strong coupling between primary production, pelagic food webs, and deep-sea benthic communities.

Taxonomic Study of Suborder Calcaxonia (Alcyonacea: Octocorallia: Anthozoa) from King Sejong Station, Antarctic

Some gorgonians in the families, Primnoidae and Isididae within the suborder Calcaxonia were collected from subtidal zones between depths of 10 and 45 m in the coastal regions of King Sejong Station (<TEX>$62^{\circ}13'S$</TEX>, <TEX>$058^{\circ}47'W$</TEX>), Korea Polar Research Institute of Korea Ocean Research and Development Institute (KORDI) by SCUBA diving from 2009 to 2011. Three species in the Primnoidae, <TEX>$Arntzia$</TEX> <TEX>$gracilis$</TEX> (Molander, 1929), <TEX>$Thouarella$</TEX> (<TEX>$Thouarella$</TEX>) <TEX>$antarctica$</TEX> (Valenciennes, 1846) and <TEX>$Onogorgia$</TEX> <TEX>$nodosa$</TEX> (Molander, 1929), and also one species in the family Isididae, <TEX>$Tenuisis$</TEX> <TEX>$microspiculata$</TEX> (Molander, 1929) are newly recorded to octocorallian fauna in Marian Cove and Potter Cove of King George Island. These four species have been described in detail.

A new genus and species of the family Isididae (Coelenterata: Octocorallia) from a CMAR Biodiversity study, and a discussion on the subfamilial placement of some nominal isidid genera

We describe a new abyssal genus and species of bamboo coral (family Isididae) with some markedly unusual characteris-tics, collected from a depth of just over 2000 m off southern Tasmania. Jasonisis thresheri n. gen., n. sp. possesses a fleshytegument that contains nematocysts, tubular axial internodes that are internally partitioned, scale-shaped sclerites thathave a morphology not recorded before for octocorals, and polyps that lack thorny rods or double stars in the pharynx.Molecular data place Jasonisis n. gen. in the subfamily Keratoisidinae whose definition is altered to incorporate the un-usual characters. We also report some comparative observations on the internal structure of the axial internodes of theisidid genera Keratoisis Wright, 1869, Lepidisis Verrill, 1883 and Isidella Gray, 1857, and we alter the definition of thesubfamily Mopseinae to allow the inclusion of the genera Tenuisis, Echinisis sensu Bayer &amp; Stefani 1987 and Sclerisis sensu Bayer &amp; Stefani 1987.

Reproducibility of trace element profiles in a specimen of the deep-water bamboo coral Keratoisis sp.

Bamboo corals (Order Gorgonacea, Family Isididae) are attractive prospects for deep-sea paleoceanographic reconstruction, capturing trace elements in their calcitic skeletons that may serve as environmental proxies with subdecadal resolution over multi-century timescales. We study the reproducibility and fidelity of trace-element profiles (Ba, Mg, Sr, Mn, U, Pb) in a 420-year-old specimen of the bamboo coral Keratoisis sp. from the SE USA. Using laser-ablation ICP-MS to obtain multiple replicate profiles, we use spectral techniques to distinguish noise and irreproducible variations from fully reproducible geochemical fluctuations that are candidates for environmental signals. By quantifying variability between profiles, we assess the fidelity with which the corals potentially record environmental information. Barium is the most reproducible element in the skeleton, with large fluctuations along different growth radii reproducing to within 4%. Both Mg and Sr have very uniform levels within the coral, but display low-amplitude irreproducible variations that might represent an internal biological process. In the case of Mg, which has been proposed as a paleotemperature proxy, this irreproducibility would represent an intrinsic uncertainty of ∼±0.1 to 0.4 °C. Both Mn and Pb contain some irreproducibility superimposed upon broad reproducible profiles that may be environmental signals. Some of the irreproducible Pb fluctuations correlate with cracks and dark bands in the sample suggesting detrital or surface contamination. Uranium displays large amplitude variations which are not reproducible along different radii. This suggests that uranium cannot be used for paleoenvironmental reconstruction, and may show signs of early diagenesis – a possibility that could complicate attempts to date young Keratoisis sp. samples by U-series geochemistry. The highly reproducible Ba signal allows precise alignment of profiles and thus we can show that growth rate along one radius can vary by a factor of two relative to growth along a different radius. There is no evidence that this large variation in relative growth rate affects either the Mg or Sr incorporation. In addition, geochemical anomalies in Ba and Mg indicate that the very central axis of the specimen may represent a different mode of growth. This study suggests that Keratoisis sp. corals are imperfect recorders of geochemical information, but do contain reproducible variations which are good candidates for environmental signals.

Temperature effects on the calcite skeletal composition of deep-water gorgonians (Isididae)

We test for and calibrate a proxy for ocean temperature based on the skeletal composition of the widely distributed, deep-sea gorgonians in the family Isididae (bamboo corals), through use of three complementary methods: a short-term comparison of element/Ca ratios to a four-year temperature record, a long-term comparison with oceanographic records spanning forty years, and a geographic comparison of Isidids collected at sites ranging from the tropics to Antarctica. The assays consistently support a temperature-dependency for Mg/Ca ratios and suggest S/Ca is indirectly affected by temperature, but indicate little or no effect of temperature on P/Ca and Sr/Ca. The consensus relationship between Mg/Ca and temperature for Isidid calcite from the comparisons with the temperature time-series is T = −0.505 + 0.048 Mg/Ca, where T is in °C, Mg/Ca is in mmol/mol, and the applicable range is 3–6 °C. The results of the geographic assay, though imprecise, suggest the applicable range extends to temperatures below freezing. The scatter of data points around the regression of temperature and Mg/Ca is wide in all assays. This could reflect the effect of factors other than temperature on Mg/Ca ratios, but is also likely to reflect limitations of the field data, the effects of assumed constant growth rates in the corals and instrumental analytical error. The combined effects of micro-scale variability in growth rates and wide confidence intervals for each data point suggests that environmental reconstruction from Isidid internode calcite from sparse data or at time scales less than decades be done with caution. Comparisons within and among colonies do not indicate strong vital effects on ontogenetic variability in the corals, other than possibly close to the central pore of the coral. However, similar Mg/Ca ratios for Isidids from Antarctic and more temperate regions suggest adaptation to local conditions and hence a role for physiology at higher taxonomic levels, at least. Taxonomically higher level vital effects are also suggested by large differences between gorgonian families in their regressions between Mg/Ca and temperature, by Mg/Ca ratios that overlap over a wide temperature and habitat range, and for a non-linear relationship between temperature and the slope of the Mg/Ca-temperature relationship across the order.

Multi-century time-series of 15N and 14C in bamboo corals from deep Tasmanian seamounts: evidence for stable oceanographic conditions

Bamboo corals (Family Isididae) are an important component of seamount benthos south of Tasmania. Besides having lifespans of up to 400 yr, little is known about their basic ecology, nor how to decode potential climate signals encoded in their skeletons. We explored the stable nitrogen isotope and radiocarbon compositions of the skeletal organic fraction of the genera Isidella, Keratoisis and Lepidisis collected from 3 Tasmanian seamounts. Analyses were performed on tissues and organic node growth rings sampled at a temporal resolution of 1 to 4 yr. Radiocarbon chronologies exhibited nuclear bomb signals characteristic of surface waters and constrained radial growth rates to ~35 ± 10 µm yr–1 for 3 specimens of the genus Lepidisis and 113 ± 17 µm yr–1 for 1 specimen of Isidella. δ15N values of the living tissue and underlying gorgonin were similar and averaged 9 to 12‰. Records of δ15N from 8 different specimens showed subtle, quasi-decadal patterns over the last ~100 yr, although the amplitude of these features (~1‰) was similar to the average intra- and intercolony reproducibility. These results demonstrate the utility of deep-sea corals to track seamount biogeochemical processes over long time scales, and suggest that the extent of nutrient depletion of surface waters and associated trophic dynamics have remained relatively constant in this region over centuries. This provides an important baseline for the evaluation of the impacts of anthropogenic climate change.

A new species of Isidella bamboo coral (Octocorallia: Alcyonacea: Isididae) from northeast Pacific Seamounts

Abstract A new species of deep-sea gorgonian, Isidella tentaculum, from 720–1050 m depths on Northeast Pacific seamount peaks, continental slopes, and shelf canyons is described and illustrated. The octocoral colonies were observed alive and in situ using a manned submersible and remotely operated vehicles. The new species is a large (up to 132 cm high), abundant, and conspicuous habitat former. It differs from its closest sister species (I. trichotoma, I. longiflora, I. lofotensis, and I. elongata) in size and stature, polyp size, and polyp arrangement. Distinctive characteristics of I. tentaculum include thornstar-shaped sclerites and large, closely-spaced, dimorphic polyps, never before reported in the family Isididae. Living colonies exhibit long basal zooids trailing from the trunk, similar in appearance to scleractinian ‘sweeper tentacles’. Large colonies have long tentacles (∼40 cm). The flabellum has whorls of 4–5 large (6–9 mm high, 2–3 mm diameter), closely packed (2–4 mm apart) autozooid polyps...

The Mitochondrial Genome of a Deep-Sea Bamboo Coral (Cnidaria, Anthozoa, Octocorallia, Isididae): Genome Structure and Putative Origins of Replication Are Not Conserved Among Octocorals

Octocoral mitochondrial (mt) DNA is subject to an exceptionally low rate of substitution, and it has been suggested that mt genome content and structure are conserved across the subclass, an observation that has been supported for most octocorallian families by phylogenetic analyses using PCR products spanning gene boundaries. However, failure to recover amplification products spanning the nad4L-msh1 gene junction in species from the family Isididae (bamboo corals) prompted us to sequence the complete mt genome of a deep-sea bamboo coral (undescribed species). Compared to the "typical" octocoral mt genome, which has 12 genes transcribed on one strand and 5 genes on the opposite (cox2, atp8, atp6, cox3, trnM), in the bamboo coral genome a contiguous string of 5 genes (msh1, rnl, nad2, nad5, nad4) has undergone an inversion, likely in a single event. Analyses of strand-specific compositional asymmetry suggest that (i) the light-strand origin of replication was also inverted and is adjacent to nad4, and (ii) the orientation of the heavy-strand origin of replication (OriH) has reversed relative to that of previously known octocoral mt genomes. Comparative analyses suggest that intramitochondrial recombination and errors in replication at OriH may be responsible for changes in gene order in octocorals and hexacorals, respectively. Using primers flanking the regions at either end of the inverted set of five genes, we examined closely related taxa and determined that the novel gene order is restricted to the deep-sea subfamily Keratoisidinae; however, we found no evidence for strand-specific mutational biases that may influence phylogenetic analyses that include this subfamily of bamboo corals.