Coral Framework Research Articles

High-resolution bathymetry and acoustic geophysical data from Santa Maria di Leuca Cold Water Coral province (Northern Ionian Sea—Apulian continental slope)

Abstract A total of 800 km 2 of multibeam echo-sounder coverage, roughly 800 km of chirp-sonar data and 18 km of side-scan sonar profiles (100/500 kHz) were acquired a few km offshore Santa Maria di Leuca (south-eastern Italy), from 200 m to 1300 m water depth. The explored area belongs to the upper slope of the gently south-eastward dipping Apulian continental margin (northern Ionian Sea). Acoustic datasets were collected, by three different oceanographic expeditions, where evidence of living cold-water coral (CWC) colonies were documented by previous surveys and samples. High-resolution multibeam bathymetry indicated an extensive rough seafloor with an irregular faulted upper surface to the west (reflecting large-scale tectonic control on the margin) and a highly disrupted upper slope formed by prominent downslope mass-movements to the north. A broad area in the east was influenced by mass-transport deposition, which resulted in a very complex hummocky seafloor, mainly shaped by detached block-like features and failure-related bedforms (i.e. low scarps, downslope lineations and compressional ridges). From the shallow seismic-stratigraphic data, failure events appeared to be multiple and recurrent and chaotic reflectors, both buried and exposed at the seafloor, affected most of the investigated area. Drift sedimentation was also recognised along a central large ridge, resulting in an interplay between contour currents and downslope turbidity currents. The spatial distribution of the CWC reefs was inferred from the acoustic facies interpretation based on video images and ground-truthed by sediment samples. It appeared that: (1) within the investigated area, living coral frameworks were located along large topographic highs facing the main flow of the bottom currents, where hard and firm substrata and/or failure-related sediment bedforms occurred; (2) CWC mainly settled on clustered (and isolated) mound-like features, tens to a few hundreds of metres long and no more than 25 m high and were located between 600 and 900 m water depth, within the broad area affected by downslope mass-transport deposits. Such mound-like morphologies could thus be interpreted as a result of sediment accreted by coral growth, with the consequent sediment trapping on small-scale positive seafloor irregularities; formed by different types of Pleistocene-exposed mass-transport deposits, their burial prevented by bottom currents.

The Holocene occurrence of cold water corals in the NE Atlantic: Implications for coral carbonate mound evolution

U-series dating of constructional cold-water corals is a powerful tool to reconstruct the evolution of corals on carbonate mounds. Here we have investigated the time framework of corals such as Lophelia pertusa and Madrepora oculata on five different mound settings of the eastern North Atlantic (on Rockall Bank and in Porcupine Seabight), sampled at variable depth and location (610–880 m water depth). We have found that the past 11 ka reflect a period generally favourable for coral development. We further determined local mound growth rates and identified mound surface erosion (framework collapse) during times of active coral framework construction. “Local” vertical mound growth rates vary between less than 5 cm ka − 1 and up to 220 cm ka − 1 . We interpret rates exceeding 15 cm ka − 1 as representative of densely populated coral reefs. During times of reduced or absent coral development, mound evolution rates are by far smaller (0 to < 5 cm ka − 1 ). The time resolution achieved here furthermore provides first evidence for reduced coral (ecosystem) activity at 1.8–2.0 ka, 4.2–4.8 ka and between 6 and 8.2 ka within the Holocene that may be related to climate driven changes of the coral growth environments. During Glacial periods coral growth in those areas seems apparently extremely reduced or is even absent on mounds.

Calcification of the cold-water coral &amp;lt;i&amp;gt;Lophelia pertusa,&amp;lt;/i&amp;gt; under ambient and reduced pH

Abstract. The cold-water coral Lophelia pertusa is one of the few species able to build reef-like structures and a 3-dimensional coral framework in the deep oceans. Furthermore, deep cold-water coral bioherms may be among the first marine ecosystems to be affected by ocean acidification. Colonies of L. pertusa were collected during a cruise in 2006 to cold-water coral bioherms of the Mingulay reef complex (Hebrides, North Atlantic). Shortly after sample collection onboard these corals were labelled with calcium-45. The same experimental approach was used to assess calcification rates and how those changed due to reduced pH during a cruise to the Skagerrak (North Sea) in 2007. The highest calcification rates were found in youngest polyps with up to 1% d−1 new skeletal growth and average rates of 0.11±0.02% d−1±S.E.). Lowering pH by 0.15 and 0.3 units relative to the ambient level resulted in calcification being reduced by 30 and 56%. Lower pH reduced calcification more in fast growing, young polyps (59% reduction) than in older polyps (40% reduction). Thus skeletal growth of young and fast calcifying corallites suffered more from ocean acidification. Nevertheless, L. pertusa exhibited positive net calcification (as measured by 45Ca incorporation) even at an aragonite saturation state (Ωa) below 1.

Sediment dynamics and palaeo-environmental context at key stages in the Challenger cold-water coral mound formation: Clues from sediment deposits at the mound base

IODP Expedition 307, targeting the 160 m high Challenger Mound and its surroundings in the Porcupine Seabight, NE Atlantic, was the first occasion of scientific drilling of a cold-water coral carbonate mound. Such mound structures are found at several locations along the continental margin but are especially numerous off Ireland. All rooted on a common unconformity (RD1) and embedded in drift sediments, the mounds in the Porcupine Seabight remain enigmatic structures, and their initial trigger and formation mechanisms are still not entirely clear. This paper discusses the sedimentary environment during the initial stages of Challenger Mound, and at the start-up of the embedding sediment drift. The results are interpreted within the regional palaeo-environmental context. Based on detailed grain-size analyses and planktonic foraminifera assemblage counts, a 14-m interval overlying the regional base-of-mound unconformity RD1 is characterised at IODP Sites U1317 (on mound), U1316 (off mound), and U1318 (background site). Several sedimentary facies are identified and interpreted in relation to regional current dynamics. Using the foraminifera counts, existing age models for the initial stages of on-mound and off-mound sedimentation are refined. Sedimentation within the initial mound was characterised by a two-mode system, with the observed cyclicities related to glacial/interglacial stages. However, the contrast in environmental conditions between the stages was less extreme than observed in the most recent glacial/interglacial cycles, allowing continuous cold-water coral growth. This sustained presence of coral framework was the key factor for fast mound build-up, baffling sediments at periods of slack currents, and protecting them from renewed erosion during high-current events. The off-mound and background sedimentation consisted mainly of a succession of contourite beds, ranging from sandy contourites in the initial stages to muddy contourites higher up in the sequence, representing the true onset of drift sedimentation. The latter illustrate the increasing importance of glacial conditions after the Mid-Pleistocene Revolution. The overall findings are summarised in a descriptive conceptual model.

The cold‐water coral community as hotspot of carbon cycling on continental margins: A food‐web analysis from Rockall Bank (northeast Atlantic)

We present a quantitative food‐web analysis of the cold‐water coral community, i.e., the assembly of living corals, dead coral branches and sediment beneath, associated with the reef‐building Lophelia pertusa on the giant carbonate mounds at ~800‐m depth at Rockall Bank. Carbon flows, 140 flows among 20 biotic and abiotic compartments, were reconstructed using linear inverse modeling by merging data on biomass, on‐board respiration, δ15N values, and literature constraints on assimilation and growth efficiencies. The carbon flux to the coral community was 75.1 mmol C m−2 d−1 and was partitioned among (phyto)detritus (81%) and zooplankton (19%). Carbon ingestion by the living coral was only 9% of the carbon ingestion by the whole community and was portioned among (phyto)detritus (72%) and zooplankton (28%). Carbon cycling in the community was dominated by suspension‐ and filter‐feeding macrofauna associated with dead coral branches. Sediment traps mounted on a bottom lander trapped 0.77 mmol C m−2 d−1 (annual average), which is almost two orders of magnitude lower than total carbon ingestion (75.1) and respiration (57.3 mmol C m−2 d−1) by the coral community. This discrepancy is explained in two ways: the coral community intercepts organic matter that would otherwise not settle on the seafloor, and through their action as ecosystem engineers, the increased turbulence generated by the coral framework and organic‐matter depletion in the boundary layer augment the influx to the coral community. A comparison of macrofaunal biomass and respiration data with soft sediments reveals that coral communities are hot spots of biomass and carbon cycling along continental margins.

The role of topography and erosion in the development and architecture of shallow-water coral bioherms (Tortonian–Messinian, Cabo de Gata, SE Spain)

During the Miocene, Mediterranean shallow-water carbonates were rich in scleractinian corals, which thrive in various depositional settings. A Tortonian–Messinian bioherm belt developing in a heterozoan-dominated ramp was investigated along a 1.2 km continuous transect located in the Cabo de Gata region. The interval studied displays four depositional environments from mid-to-inner ramp, dominated by swell waves and storm energy, deposited as a single, large-scale depositional sequence during a 3rd to 4th order transgressive–regressive cycle. The bioherms grew in three phases, and were essentially composed of in-place primary frameworks. Three coral genera were the main framebuilders ( Porites, Tarbellastrea and rare Siderastrea), associated with melobesioid and mastophoroid red algae and bryozoans as secondary framebuilders. The corals display five morphotypes, from a fast-growing branched type to slow-growing domal to plate morphologies, with an uncommon form of mesh Porites as the dominant morphotype. Changes in coral morphotype and composition of micro-encrusters communities reveal changes in hydrodynamics, detrital influx and perhaps nutrient levels. Bioherms architecture was driven by sea level, palaeotopography and erosion. The coral framework was affected during its development by erosion surfaces metres to tens of metres deep and hundreds of metres wide. Unexpectedly, these surfaces are better developed on the inner edges of the bioherms. This could indicate the circulation of strong bottom currents between the volcanic palaeohighs and the synoptic relief created by the buildups. Finally, a major sub-aerial erosional episode associated with increasing detrital influxes, ended bioherm development, thus allowing the colonization of the dead coral substratum by red algae.

Sediment accumulation on a cold-water carbonate mound at the Southwest Rockall Trough margin

Cold-water corals build isolated and clustered carbonate mound ridges, several kilometres long and wide and up to 380 m high at the Southwest Rockall Trough margin. Photo and video observations as well as coring have shown that mainly the upper mound flanks and summits are covered with a thriving living coral cover and associated fauna. Box cores prove the presence of living coral colonies on top of a thick layer of coral debris, which is to a large extent abraded and bio-eroded, before being buried. The coral framework is filled with sediment from settling pelagic material and parts of the fauna living at the mounds, resulting in a 120 cm thick layer of sediments since 10,800 yr. Component analysis of a piston core from the top of a carbonate mound shows a complete record of cold-water coral mound facies, comprising many different species living at the mounds. An alternation of skeletal and cement dominated intervals was distinguished in the piston core. Stable isotope analysis of planktonic and benthic foraminifera indicates a continuous sedimentation pattern since the Younger Dryas. The deeper and older part of the core, showing mainly intermediate isotope values, is dominated by the presence of large hiatuses, spanning a total of up to 200,000 yr. Hiatuses in the core may reflect periods of non-deposition or erosion, which may be linked to glacial–interglacial variability. Environmental conditions probably change at glacial–interglacial timescales, influencing the local hydrodynamic regime, food supply and sedimentation rate around the carbonate mounds affecting coral growth and therefore carbonate mound development.

MDE for SoC design

We employ the principles of model-driven engineering to assist the design of system-on-chip (SoC) architectures. As a concrete example, we look at the MICAS architecture, for which we propose a graphical specification language, defined via metamodeling techniques, that models the architecture at different abstraction levels. Model transformations are defined to support the refinement of MICAS specification towards implementation. In addition, several libraries are put in place, to enable reuse and automation throughout the design process. Tool support for editing the specifications, enforcing their consistency, and for running the transformations is provided via the Coral modeling framework. The approach shows that model-driven engineering can be seen as an enabler in providing computer-aided software engineering (CASE) tool support and automation for the development of SoC architectures.

Near-bed particle deposition and resuspension in a cold-water coral mound area at the Southwest Rockall Trough margin, NE Atlantic

Cold-water coral reefs and mounds are observed mainly on slopes and topographic highs, in areas with high current speeds. Previous investigations of the near-bed hydrodynamic regime around cold-water coral mounds at the Southwest Rockall Trough margin have revealed the presence of internal waves with a diurnal tidal frequency. Hitherto only short-term measurements existed on the particle supply to the corals and data are lacking on the seasonal variability. Bottom landers equipped with sensors recording near-bottom current dynamics were deployed at two sites in a mound area on the Southwest Rockall Trough margin, one with a dense coral cover and one without coral cover. At both sites a similar seasonal variation in internal-wave activity was recorded with high activity during winter and summer months and less dynamic conditions in spring and autumn. Increased intensity of internal-wave activity, reflected in higher average near-bottom current speed and amplitude of daily temperature fluctuations, results in higher mass fluxes as recorded in the sediment traps. On the site without coral cover, mass fluxes are two times higher, compared to the site with dense coral cover. During periods of high mass fluxes a predominance of resuspended material was observed at both sites, as indicated by reduced 210Pb activity and low organic matter concentrations. The flux of resuspended material largely masked the primary pelagic signal. However, low δ 15N values in early spring and summer marked the arrival of fresh particles on both sites. A dense coral framework, baffling a large amount of particles settling between the coral branches, results in differences in particle flux, chemical composition and freshness of the trapped material. On the long term the presence of a coral framework plays a crucial role in the build-up of cold-water coral mounds.

Carbonate budget of a cold-water coral mound (Challenger Mound, IODP Exp. 307)

Cold-water coral ecosystems represent a worldwide distributed carbonate factory, which is so far not considered in global carbonate budget estimations. The herein presented study evaluates the carbonate budget of a complete cold-water coral mound sequence from Challenger Mound (Belgica Mound Province, Porcupine Seabight, SW offshore Ireland; drilled during IODP Expedition 307) reaching back to the Late Pliocene (< 2.7 Ma) especially focusing on the different carbonate sources (coral-derived aragonite versus background-sediment-derived calcite-dominated carbonate). Cores from adjacent drift deposits were examined for comparison studies. Challenger Mound, which developed in a fast growth phase (unit M1; ~ 2.7 to ~ 1.6 Ma) and a slower growth phase or mound-decline (unit M2; ~ 0.8 Ma until today), separated by a so called ‘mound crisis’, displays increased carbonate accumulation rates for both phases (17.3 g/(cm 2 × ka) for unit M1 and 5.7 g/(cm 2 × ka) for unit M2) compared to adjacent drift deposits. But only about 33 to 40 wt.% of the carbonate is derived from corals. Bulk sedimentation rates of on- and off-mound deposits suggest a decline of Challenger Mound since the onset of drift deposition in the area about 1.2 Ma ago. Yet total carbonate accumulation rates as well as hemipelagic Background-Sediment-Derived Carbonate accumulation rates from Challenger Mound (unit M2) still exceed the carbonate accumulation rates of the adjacent drift deposits. The selective enrichment of Background-Sediment-Derived Carbonate (by a factor of 2.0) in a CWC Mound is herein observed for the first time. This might be caused by the different hydrodynamic behaviour and slower settlement of marine fluff rich in calcareous detritus, compared to siliciclastic sediments, and its effective baffling by the coral framework and/or the active catch of the calcareous plankton by the corals. The carbonate accumulation rates of Challenger Mound are about 4 to 12% of the carbonate accumulation rates of tropical shallow-water reefs but exceeds the carbonate accumulation rates of continental slopes by a factor of 3.9 to 11.8. The carbonate production for the entire Belgica Mound Province is estimated with 3.2 × 10 3 t/a for unit M1 and 1.0 × 10 3 t/a for unit M2.

Estimation of photosynthesis and calcification rates at a fringing reef by accounting for diurnal variations and the zonation of coral reef communities on reef flat and slope: a case study for the Shiraho reef, Ishigaki Island, southwest Japan

Seven coral reef communities were defined on Shiraho fringing reef, Ishigaki Island, Japan. Net photosynthesis and calcification rates were measured by in situ incubations at 10 sites that included six of the defined communities, and which occupied most of the area on the reef flat and slope. Net photosynthesis on the reef flat was positive overall, but the reef flat acts as a source for atmospheric CO2, because the measured calcification/photosynthesis ratio of 2.5 is greater than the critical ratio of 1.67. Net photosynthesis on the reef slope was negative. Almost all excess organic production from the reef flat is expected to be effused to the outer reef and consumed by the communities there. Therefore, the total net organic production of the whole reef system is probably almost zero and the whole reef system also acts as a source for atmospheric CO2. Net calcification rates of the reef slope corals were much lower than those of the branching corals. The accumulation rate of the former was approximately 0.5 m kyr−1 and of the latter was ~0.7–5 m kyr−1. Consequently, reef slope corals could not grow fast enough to keep up with or catch up to rising sea levels during the Holocene. On the other hand, the branching corals grow fast enough to keep up with this rising sea level. Therefore, a transition between early Holocene and present-day reef communities is expected. Branching coral communities would have dominated while reef growth kept pace with sea level rise, and the reef was constructed with a branching coral framework. Then, the outside of this framework was covered and built up by reef slope corals and present-day reefs were constructed.

Importance of seep primary production to Lophelia pertusa and associated fauna in the Gulf of Mexico

To investigate the importance of seep primary production to the nutrition of Lophelia pertusa and associated communities and examine local trophic interactions, we analyzed stable carbon, nitrogen, and sulfur compositions in seven quantitative L. pertusa community collections. A significant seep signature was only detected in one of the 35 species tested ( Provanna sculpta, a common seep gastropod) despite the presence of seep fauna at the three sample sites. A potential predator of L. pertusa was identified ( Coralliophila sp.), and a variety of other trophic interactions among the fauna occupying the coral framework were suggested by the data, including the galatheid crab Munidopsis sp. 2 feeding upon hydroids and the polychaete Eunice sp. feeding upon the sabellid polychaete Euratella sp. Stable carbon abundances were also determined for different sections of L. pertusa skeleton representing different stages in the growth and life of the aggregation. There was no temporal trend detected in the skeleton isotope values, suggesting that L. pertusa settles in these areas only after seepage has largely subsided. Isotope values of individual taxa that were collected from both L. pertusa and vestimentiferan habitats showed decreasing reliance upon seep primary production with average age of the vestimentiferan aggregation, and finally, no seep signature was detected in the coral collections. Together our data suggest that it is the presence of authigenic carbonate substrata, a product of past seep microbial activity, as well as hydrodynamic processes that drive L. pertusa occurrence at seep sites in the Gulf of Mexico, not nutritional dependence upon primary production by seep microbes.

Microbioerosion in Tahitian reefs: a record of environmental change during the last deglacial sea‐level rise (IODP 310)

The main motivation for Integrated Ocean Drilling Program Expedition 310 to the Tahitian Archipelago was the assumption that the last deglacial sea-level rise is precisely recorded in the coral reefs of this far-field site. The Tahitian deglacial succession typically consists of coral framework subsequently encrusted by coralline algae and microbialites. The high abundance of microbialites is uncommon for shallow-water coral reefs, and the environmental conditions favouring their development are still poorly understood. Microbioerosion patterns in the three principal framework components (corals, coralline algae, microbialites) are studied with respect to relative light availability during coral growth and subsequent encrustation, in order to constrain the palaeobathymetry and the relative timing of the encrustation. Unexpectedly for a tropical, light-flooded setting, ichnotaxa typical for the deep-euphotic to dysphotic zone dominate. The key ichnotaxa for the shallow euphotic zone are scarce in the analysed sample set, and are restricted to the base of the deglacial succession, thus reflecting the deglacial sea-level rise. At the base of the deglacial reef succession, the ichnocoenoses present in the corals indicate shallower bathymetries than those in the encrusting microbialites. This is in agreement with radiocarbon data that indicate a time gap of more than 600 years between coral death and microbialite formation. At the top of the deglacial reef succession, in contrast, the microbioerosion patterns in the three framework components indicate a uniform palaeobathymetry, and radiocarbon ages imply that encrustation took place shortly after coral demise. An enigma arises from the fact that the ichnocoenoses imply photic conditions that appear very deep for zooxanthellate coral growth. During the deglacial sea-level rise increased nutrients and fluvial influx may have led to (seasonal?) eutrophication, condensing the photic zonation. This would have exerted stress on the coral ecosystem and played a significant role in initiating microbialite development.

Morphology and sedimentology of (clustered) cold-water coral mounds at the south Rockall Trough margins, NE Atlantic Ocean

Cold-water coral mounds on both margins of the Rockall Trough (NE Atlantic Ocean) have a strongly different morphology. Single, isolated mounds occur on the SE margin and are mainly found on the upper slope between 900 and 650 m water depth, while large mound clusters are found on the SW margin in water depths between 600 and 1,000 m, in a narrow zone almost parallel to the slope. Sedimentation rates on the mounds are higher than on the surrounding seabed as a result of baffling of biogenic carbonate debris and siliciclastic particles by the coral framework covering the mounds. This is confirmed by 210Pb measurements. The individual coral growth rate can be three times higher then the vertical growth rate of the coral cover (±10 mm year−1) which in turn is more than an order of magnitude higher then the present-day overall mound growth rate (±0.25 mm year−1). The presence of extensive hardgrounds and firmgrounds and the three-dimensional coral framework are considered to be responsible for the stability of the relatively steep slopes of the mounds. High current velocities in the intramound areas result in local non-sedimentation and erosion, as is shown by the presence of IRD (ice-rafted debris) lag deposits on the seabed and moats around some of the mounds. The morphology and sedimentology of cold-water coral-covered (mainly Lophelia pertusa and Madrepora oculata) mounds on the southern Rockall Trough margins (NE Atlantic Ocean) is discussed and a model describing the development of these mounds is presented.

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.

Coral communities of the deep Gulf of Mexico

Habitat formation by foundation species is a major ecological force affecting community structure in numerous systems. On the upper continental slope of the Gulf of Mexico, the cold-water scleractinian coral Lophelia pertusa creates complex habitat on cold seep-associated carbonates. In this study, the communities associated with the cold-water coral L. pertusa are described from the Gulf of Mexico for the first time. A total of 68 taxa was identified in close association with the coral framework. Three species with specific relationships to L. pertusa were identified: Eunice sp., a polychaete which may facilitate colony formation in L. pertusa; Coralliophila sp., a species of corallivorous gastropod ; and Stenopus sp., a decapod crustacean which may act in a cleaner shrimp role in these habitats. Similarity among coral-associated communities was best explained by similarity in depth of collection and the proportion of live coral in the collections. These variables were somewhat confounded with location as the sites to the east were both shallower and contained higher proportions of live coral; however, distance between collections per se was not as significant in the analyses. The coral-associated communities also showed a low degree of similarity to communities inhabiting vestimentiferan tubeworm aggregations that occur nearby at the same sites. The increased habitat heterogeneity in the coral structure, differences in the niches constructed by the two foundation species, and different direct interspecific interactions between foundation species and members of the associated community contributed to the presence of dissimilar communities in these two biogenic habitats.

Boring sponges and the modeling of coral reefs in the east Pacific Ocean

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 356:113-122 (2008) - DOI: https://doi.org/10.3354/meps07276 Boring sponges and the modeling of coral reefs in the east Pacific Ocean José Luis Carballo1,*, Eric Bautista-Guerrero1, Gerardo E. Leyte-Morales2 1Instituto de Ciencias del Mar y Limnología, UNAM (Estación Mazatlán), Apartado postal 811, 82000 Mazatlán, México 2Universidad del Mar, Campus Puerto Ángel, Oaxaca, Apartado postal 47, Puerto Ángel, 70902 Oaxaca, México *Email: jlcarballo@ola.icmyl.unam.mx ABSTRACT: A total of 900 coral fragments collected across 2 fringing reefs located southwest of Mexico, La Entrega (LE) and San Agustín (SA), were examined for the presence of boring sponges. Of all samples, 43% were invaded by boring sponges, and 7 species belonging to 5 genera (Aka, Cliona, Pione, Cliothosa and Thoosa) were identified. The most abundant species were Cliona vermifera (17.9%), Cliona sp. (10.8%), A. cryptica (7.8%) and P. carpenteri (6.0%). The distribution and abundance of the species varied considerably throughout the reef area (margin and platform) and displayed certain selectivity for specific calcareous substrata. C. vermifera, Cliona sp., A. cryptica and P. carpenteri were most common on the reef margins, while T. calpulli was common on the central platform. A. cryptica, P. carpenteri, and Cliothosa hancocki were frequently found living in the immediate vicinity of live coral tissue, contrary to C. vermifera, T. calpulli and Cliona mucronata, which preferentially bored coral rubble. The results showed that reef margins had a significantly higher infestation level than the platforms (mean infestations of 60.6 and 26.2%, respectively). There were also differences between reefs. The infestation was higher on LE than on SA (48.6 and 38.2%, respectively), and these differences were larger between the platforms of the 2 reefs (41.3 and 11.1%, respectively). In general, the results of the present study have demonstrated that the diversity and abundance of species, as well as the infestation of coral frameworks by sponges, was significantly higher in the margin at both reefs studied and on the platform of LE, where the availability of exposed carbonate substrate was higher. In the margin of these reefs, the consequences of boring went far beyond the mere hollowing out of a few cavities, since by weakening the coral’s attachment to the substrate, the sponges accelerated coral loss and restructured the reef edge. This pattern may have important implications for the preservation of the reef framework. KEY WORDS: Bioerosion · Boring sponges · Fringing coral reefs · Reef margin · Reef flat · Mexican Pacific Full text in pdf format PreviousNextCite this article as: Carballo JL, Bautista-Guerrero E, Leyte-Morales GE (2008) Boring sponges and the modeling of coral reefs in the east Pacific Ocean. Mar Ecol Prog Ser 356:113-122. https://doi.org/10.3354/meps07276 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 356. Online publication date: March 18, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Carbonate mounds in a mud volcano province off north-west Morocco: Key to processes and controls

This paper presents a new cluster of carbonate mounds discovered in 2002 in the Gulf of Cadiz off Morocco ( R/V Belgica 2002) in water depths of 500 to 600 m amidst a field of giant mud volcanoes. Multibeam bathymetry, side scan sonar imagery and 2D seismics are analyzed to present four mound provinces: (1) the Pen Duick Mound Province on the Pen Duick Escarpment, (2) the Renard Mound Province on the Renard Ridge, (3) the Vernadsky Mound Province on the Vernadsky Ridge and the Al Idrisi Mound Province on the gas-blanked sediments above the buried Al Idrisi Ridge. Video imagery and surface samples are described to ground-truth the different mound areas. The paradox is that nearly no live corals are presently being observed at the surface of the mounds, while the mound cores display throughout a high number of reef-forming cold-water coral fragments (scleractinians) in association with numerous associated fauna formerly inhabiting the econiches provided by the coral framework. Environmental and oceanographic conditions during the recent past (glacials/stadials) were probably more favourable for cold-water coral growth. Pore water analyses in on-mound cores at the south-eastern edge of Pen Duick Escarpment give evidence of focused, higher methane fluxes and sulphate reduction rates on mounds than in the surrounding sediments. Cores from several mounds display horizons of strong corrosion and dissolution of the coral fragments. A three-phase model for carbonate mound evolution in these settings is proposed. (1) In a first stage external controls (positive oceanographic and environmental conditions, the presence of an active planktonic food chain, based on a high primary production, and a suitable substrate) are responsible for the initiation of cold-water coral growth. (2) Once the cold-water corals established an initial framework, sedimentation becomes an important factor controlling mound growth: the cold-water corals baffle the sediments. (3) Throughout mound growth, the mound may episodically be affected by diagenetic processes responsible for aragonite dissolution and probably carbonate precipitation.

Franken Mound: facies and biocoenoses on a newly-discovered “carbonate mound” on the western Rockall Bank, NE Atlantic

Cold-water coral carbonate mounds are widespread along the Irish continental margin. Whereas the Porcupine Seabight and the Rockall Trough are relatively well studied with regard to mound topography, coral coverage, and benthic life diversity, the situation on the western Rockall Bank is rather unknown. Detailed facies and biocoenoses mapping based on video footage analyses was conducted on the newly-discovered Franken Mound. Facies were identified ranging between cliff-like to planar hardgrounds and soft sediments that are partly rippled. A variety of biocoenoses are associated with these facies comprising discrete live coral colonies, dense live and dead coral framework coverage, abundant to scattered coral debris, and a soft sediment faunal community, whereas the latter is three times less speciose as biocoenoses containing live framework-building corals. The facies and biocoenosis classes are supplemented by exposed dropstones, lost fishery nets, and rubbish. The distribution of the classes clearly indicates a close relationship with local current effects and current intensification. Due to the dominance of dead coral framework and the partially exposed internal sediment sequences on the mound flanks, it is assumed that Franken Mound is approaching the “mound retirement” mound growth state.

Syn-depositional alteration of coral reef framework through bioerosion, encrustation and cementation: Taphonomic signatures of reef accretion and reef depositional events

Abstract The development of coral reef framework and the preservational character of both in-situ and rubble coral is strongly influenced by a range of physical, chemical and biologically-mediated taphonomic processes. These operate at, or just below, the reef framework–water interface and can be defined as having either a constructive or destructive effect upon primary reef framework (i.e., coral) constituents. Constructional activities add additional calcium carbonate to the primary framework structure via secondary framework growth and early cementation. Destructive processes, which remove or degrade primary (and secondary) framework carbonate, are associated with the effects of either physical (mainly storm) disturbance or biological erosion (termed bioerosion). Key bioeroding groups include the grazing fish and echinoid groups, as well as the activities of an array of infaunal borers. These include specific groups of sponges, bivalves and worms (termed macroborers), as well as cyanobacteria, chlorophytes, rhodophytes and fungi (termed microborers). The relative importance of each process and the rates at which they operate vary spatially across individual reef systems. In addition, many of these processes leave distinctive signatures on, or in, the coral framework. In some cases (e.g., calcareous encrusters) these are the skeletons of the organisms themselves, whilst in other cases the organism may leave behind a trace of their activity (e.g., macro- and microborers). These represent useful palaeoenvironmental tools, firstly because they often have good preservation potential and, secondly because the range and extent of many of the individual species, groups and processes involved exhibit reasonably well-constrained environment and/or depth-related distributions. As a result these taphonomically important organisms or processes can be used to delineate between reef environments in core or outcrop, and to aid the interpretation of reef depositional processes and ‘events’. This review summarises current understanding regarding the distribution of these species/processes within contemporary reef settings and considers the suites of taphonomic signatures that may aid in the recognition and interpretation of depositional environments and events.