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Yasufumi Iryu - One of the best experts on this subject based on the ideXlab platform.
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Boring bivalve traces in modern reef and deeper-water macroid and Rhodolith beds
Progress in Earth and Planetary Science, 2020Co-Authors: Davide Bassi, Julio Aguirre, Juan C. Braga, Masato Owada, Jere H. Lipps, Hideko Takayanagi, Yasufumi IryuAbstract:Macroids and Rhodoliths, made by encrusting acervulinid foraminifera and coralline algae, are widely recognized as bioengineers providing relatively stable microhabitats and increasing biodiversity for other species. Macroid and Rhodolith beds occur in different depositional settings at various localities and bathymetries worldwide. Six case studies of macroid/Rhodolith beds from 0 to 117 m water depth in the Pacific Ocean (northern Central Ryukyu Islands, French Polynesia), eastern Australia (Fraser Island, One Tree Reef, Lizard Island), and the Mediterranean Sea (southeastern Spain) show that nodules in the beds are perforated by small-sized boring bivalve traces (Gastrochanolites). On average, boring bivalve shells (gastrochaenids and mytilids) are more slender and smaller than those living inside shallow-water rocky substrates. In the Pacific, Gastrochaena cuneiformis, Gastrochaena sp., Leiosolenus malaccanus, L. mucronatus, L. spp., and Lithophaga/Leiosolenus sp., for the first time identified below 20 m water depth, occur as juvenile forms along with rare small-sized adults. In deep-water macroids and Rhodoliths the boring bivalves are larger than the shallower counterparts in which growth of juveniles is probably restrained by higher overturn rates of host nodules. In general, most boring bivalves are juveniles that grew faster than the acervulinid foraminiferal and coralline red algal hosts and rarely reached the adult stage. As a consequence of phenotypic plasticity, small-sized adults with slow growth rates coexist with juveniles. Below wave base macroids and Rhodoliths had the highest amounts of bioerosion, mainly produced by sponges and polychaete worms. These modern observations provide bases for paleobiological inferences in fossil occurrences.
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To Be or Not to Be a Fossil Rhodolith? Analytical Methods for Studying Fossil Rhodolith Deposits
Journal of Coastal Research, 2012Co-Authors: Davide Bassi, Yasufumi Iryu, James H. NebelsickAbstract:Abstract BASSI, D.; IRYU, Y., and NEBELSICK, J.H., 2012. To be or not to be a fossil Rhodolith? Analytical methods for studying fossil Rhodolith deposits. The past environment is often reconstructed by measuring certain proxy data, such as changes in oxygen isotopes, taxonomic assemblages, and taphonomic signatures in a palaeoenvironmental archive (e.g., Rhodoliths, corals, invertebrate shells, trees, ice cores, speleothems, etc.). Proxy analysis usually yields a record that has to be compared with present-day analogues to yield meaningful results. This also holds true for the interpretation of the palaeoenvironment of Rhodolith deposits. The characteristics of Recent Rhodoliths and the environments in which they are formed, thus, need to be known to interpret their fossil counterparts. The comparison of fossil and Recent Rhodoliths and their environment is, however, not straightforward because the respective analytical methods applied to them are usually different and often difficult to reconcile. To red...
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To Be or Not to Be a Fossil Rhodolith? Analytical Methods for Studying Fossil Rhodolith Deposits
Journal of Coastal Research, 2012Co-Authors: Davide Bassi, Yasufumi Iryu, James H. NebelsickAbstract:The past environment is often reconstructed by measuring certain proxy data, such as changes in oxygen isotopes, taxonomic assemblages, and taphonomic signatures in a palaeoenvironmental archive (e.g., Rhodoliths, corals, invertebrate shells, trees, ice cores, speleothems, etc.). Proxy analysis usually yields a record that has to be compared with present day analogues in order toto yield meaningful results. This also holds true for the interpretation of the palaeoenvironment of Rhodolith deposits. The characteristics of Recent Rhodoliths and the environments in which they are formed, thus, need to be known in order toto interpret their fossil counterparts. The comparison of fossil and Recent Rhodoliths and their environment is, however, not straightforward, because the respective analytical methods applied to them are usually different and often difficult to reconcile. In order toTo reduce the uncertainties of this problem and to facilitate direct comparisons, we describe a number of analytical methods applied to fossil Rhodoliths that can also be performed on Recent material. The analytical methods introduced here correspond to three different scales of analysis: (1) the outcrop scale as completed in field studies, and the study of (2) isolated specimens and (3) thin sections in the laboratory
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Present-day and fossil Rhodolith pavements compared: Their potential for analysing shallow-water carbonate deposits
Sedimentary Geology, 2009Co-Authors: Davide Bassi, James H. Nebelsick, Alessio Checconi, Johann Hohenegger, Yasufumi IryuAbstract:Coralline red algae represent the main biogenic components in most shallow-water carbonate successions from the Eocene to the Recent. They contribute significantly to sediment production on open platforms. Carbonate sediments formed by unattached coralline algae include Rhodolith pavements (RPs) which represent dense accumulations of Rhodoliths, as well as maërl which is composed of Rhodoliths, coralline algal branches and their detritus. Recent RPs sampled off Sesoko-jima (Okinawa-jima, southern Japan) occur at depths of 50–70 m on a submarine terrace. The taxonomic coralline composition is dominated by melobesioids associated with minor amounts of mastophoroids and sporolithaceans. The Rhodoliths are characterised by various nuclei, an encrusting inner arrangement, encrusting to warty outer growth-forms and sub-spheroidal shapes. Bioerosion, encrustation and abrasion are the most prevalent taphonomic features. Possible fossil counterparts were identified in Chattian and Priabonian RPs from middle-ramp depositional systems from the Venetian area, north-east Italy. A direct comparison between Recent and fossil RPs is possible by contrasting the constituent Rhodolith characteristics including taxonomic composition, nature of the nucleus, inner arrangement, outer growth-forms, size and shape as well as taphonomic signatures. This allows factors controlling Rhodolith formation and growth in RPs to be compared especially with respect to hydrodynamic regimes and substrate type
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Present-day and fossil Rhodolith pavements compared: Their potential for analysing shallow-water carbonate deposits
Sedimentary Geology, 2008Co-Authors: Davide Bassi, James H. Nebelsick, Alessio Checconi, Johann Hohenegger, Yasufumi IryuAbstract:Abstract Coralline red algae represent the main biogenic components in most shallow-water carbonate successions from the Eocene to the Recent. They contribute significantly to sediment production on open platforms. Carbonate sediments formed by unattached coralline algae include Rhodolith pavements (RPs) which represent dense accumulations of Rhodoliths, as well as maerl which is composed of Rhodoliths, coralline algal branches and their detritus. Recent RPs sampled off Sesoko-jima (Okinawa-jima, southern Japan) occur at depths of 50–70 m on a submarine terrace. The taxonomic coralline composition is dominated by melobesioids associated with minor amounts of mastophoroids and sporolithaceans. The Rhodoliths are characterised by various nuclei, an encrusting inner arrangement, encrusting to warty outer growth-forms and sub-spheroidal shapes. Bioerosion, encrustation and abrasion are the most prevalent taphonomic features. Possible fossil counterparts were identified in Chattian and Priabonian RPs from middle-ramp depositional systems from the Venetian area, north-east Italy. A direct comparison between Recent and fossil RPs is possible by contrasting the constituent Rhodolith characteristics including taxonomic composition, nature of the nucleus, inner arrangement, outer growth-forms, size and shape as well as taphonomic signatures. This allows factors controlling Rhodolith formation and growth in RPs to be compared especially with respect to hydrodynamic regimes and substrate type.
Davide Bassi - One of the best experts on this subject based on the ideXlab platform.
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Boring bivalve traces in modern reef and deeper-water macroid and Rhodolith beds
Progress in Earth and Planetary Science, 2020Co-Authors: Davide Bassi, Julio Aguirre, Juan C. Braga, Masato Owada, Jere H. Lipps, Hideko Takayanagi, Yasufumi IryuAbstract:Macroids and Rhodoliths, made by encrusting acervulinid foraminifera and coralline algae, are widely recognized as bioengineers providing relatively stable microhabitats and increasing biodiversity for other species. Macroid and Rhodolith beds occur in different depositional settings at various localities and bathymetries worldwide. Six case studies of macroid/Rhodolith beds from 0 to 117 m water depth in the Pacific Ocean (northern Central Ryukyu Islands, French Polynesia), eastern Australia (Fraser Island, One Tree Reef, Lizard Island), and the Mediterranean Sea (southeastern Spain) show that nodules in the beds are perforated by small-sized boring bivalve traces (Gastrochanolites). On average, boring bivalve shells (gastrochaenids and mytilids) are more slender and smaller than those living inside shallow-water rocky substrates. In the Pacific, Gastrochaena cuneiformis, Gastrochaena sp., Leiosolenus malaccanus, L. mucronatus, L. spp., and Lithophaga/Leiosolenus sp., for the first time identified below 20 m water depth, occur as juvenile forms along with rare small-sized adults. In deep-water macroids and Rhodoliths the boring bivalves are larger than the shallower counterparts in which growth of juveniles is probably restrained by higher overturn rates of host nodules. In general, most boring bivalves are juveniles that grew faster than the acervulinid foraminiferal and coralline red algal hosts and rarely reached the adult stage. As a consequence of phenotypic plasticity, small-sized adults with slow growth rates coexist with juveniles. Below wave base macroids and Rhodoliths had the highest amounts of bioerosion, mainly produced by sponges and polychaete worms. These modern observations provide bases for paleobiological inferences in fossil occurrences.
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Rhodoliths and Rhodolith Beds in the Rock Record
Rhodolith Maërl Beds: A Global Perspective, 2016Co-Authors: Julio Aguirre, Juan C. Braga, Davide BassiAbstract:Calcareous coralline algae (Rhodophyta; Corallinales, Hapalidiales, and Sporolithales; corallines hereafter) constitute one of the most widespread and successful groups of marine macrophytes. They occur as crusts partially coating hard or soft substrates, as laminar thalli growing directly on the seabed, or forming structures rolling freely on the substrate with an inner nucleus or without it. These latter structures are called Rhodoliths. They can be one of the most abundant components in carbonate platform deposits, forming the so-called rhodalgal facies. In assessments of the Rhodoliths, internal and external algal growth morphology, Rhodolith external form, Rhodolith inner arrangement, and assemblages of organisms forming the Rhodoliths can provide valuable information for reconstructing palaeoenvironmental and palaeoclimatic conditions. Rhodoliths can occur massively concentrated in beds several meters thick. These concentrations are referred as Rhodolith beds. These Rhodolith beds may be the result of biotic (autochthonous Rhodolith beds), abiotic (allochthonous Rhodolith beds) concentrations or due to a mixture of processes (paraautochthonous Rhodolith beds). Taphonomic and facies analyses, as well as faunal assemblages, can provide the information needed to confidently differentiate among them. The rock record offers unique information to envisage the founding conditions and the long-term maintenance of the Rhodolith beds. In this chapter, we review and update the information on fossil Rhodoliths and Rhodolith beds, and discuss their value for palaeoenvironmental and palaeoclimatic reconstructions. Also, we discuss the sedimentary and the sequence stratigraphy contexts in which Rhodolith beds are preferentially formed and developed.
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Re-sedimented Rhodoliths in Channelized Depositional Systems
Rhodolith Maërl Beds: A Global Perspective, 2016Co-Authors: Davide Bassi, Lucia Simone, James H. NebelsickAbstract:The knowledge of re-sedimented Rhodolith deposits has always lagged behind that of in situ deposits, which can be formed in shallow and deeper water carbonate and mixed siliciclastic-carbonate depositional settings. A combination of detailed outcrop analyses from three published case studies reveals a series of palaeobiological and taphonomic signals that are used to identify fossil re-sedimented Rhodoliths. The re-sedimented Rhodolith deposits of the middle Eocene carbonates in the Venetian area (northeast Italy), the lower Miocene carbonates from southern Sardinia (Italy), and the lower–middle Miocene carbonates from Southern Apennines (southern Italy) are described in terms of Rhodolith morphology, coralline algal assemblages, inner arrangement, outer growth-forms, and taphonomic signatures. In all the cases, shallow water Rhodolith beds were redeposited to feed offshore deposits through submarine channel systems. The sedimentological features, Rhodolith characteristics and taphonomic signatures of the Rhodolith deposits are compared from the carbonate factory, through the shelf-margin to the proximal and distal parts of the tributary belt. Within submarine channelized carbonate settings, complex relationship patterns of autochthonous/parautochthonous and allochthonous Rhodolith deposits were governed by the interplay of changes in environmental factors such as water energy, light irradiance, substrate characteristics, and residence time on the sediment-water interface.
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Origin and resedimentation of Rhodoliths in the Late Paleocene flysch of the Polish Outer Carpathians
Facies, 2012Co-Authors: Stanisław Leszczyński, Davide Bassi, Bogusław Kołodziej, Ewa Malata, M. Adam GasińskiAbstract:This study analyses the Rhodolith-bearing deposits in the largest and most Rhodolith-rich outcrop of the Polish Outer Carpathian flysch, located in the Silesian Nappe, at the village of Melsztyn. The Rhodoliths and sparse associated biota occur as resedimented components in a deep-marine succession of siliciclastic conglomerates and coarse-grained sandstones, deposited by high-density turbidity currents and debris flows. The sediment was derived from a fan-delta system located at the southern margin of the Silesian flysch basin. Stratigraphic data indicate that the succession represents the Upper Istebna Sandstone deposited during the Late Paleocene. The Rhodoliths are composed mostly of coralline red algae with seven genera and eight species representing the family Sporolithaceae and the subfamilies Mastophoroideae and Melobesioideae. Rhodoliths show sub-spheroidal and sub-ellipsoidal shapes with encrusting, warty and lumpy growth forms. Lumpy growth forms show massive inner arrangements, whereas the encrusting growth forms are usually made of thin thalli and show more loosely packed inner arrangements. The Rhodoliths grew on a moderately mobile siliciclastic substrate in a shallow-marine environment with a low net sedimentation rate. It is inferred that the growth of Rhodoliths was favored during a relative sea-level rise. During the subsequent sea-level fall, the Rhodoliths and associated siliciclastic deposits were resedimented by gravity flows into the deep-sea setting. The analyzed deposits, like other Paleocene–Eocene deposits of the Polish Outer Carpathians, provide no evidence of coeval widespread shallow-marine carbonate sedimentation along the margins of the Outer Carpathian flysch basins.
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To Be or Not to Be a Fossil Rhodolith? Analytical Methods for Studying Fossil Rhodolith Deposits
Journal of Coastal Research, 2012Co-Authors: Davide Bassi, Yasufumi Iryu, James H. NebelsickAbstract:Abstract BASSI, D.; IRYU, Y., and NEBELSICK, J.H., 2012. To be or not to be a fossil Rhodolith? Analytical methods for studying fossil Rhodolith deposits. The past environment is often reconstructed by measuring certain proxy data, such as changes in oxygen isotopes, taxonomic assemblages, and taphonomic signatures in a palaeoenvironmental archive (e.g., Rhodoliths, corals, invertebrate shells, trees, ice cores, speleothems, etc.). Proxy analysis usually yields a record that has to be compared with present-day analogues to yield meaningful results. This also holds true for the interpretation of the palaeoenvironment of Rhodolith deposits. The characteristics of Recent Rhodoliths and the environments in which they are formed, thus, need to be known to interpret their fossil counterparts. The comparison of fossil and Recent Rhodoliths and their environment is, however, not straightforward because the respective analytical methods applied to them are usually different and often difficult to reconcile. To red...
Gilberto M. Amado-filho - One of the best experts on this subject based on the ideXlab platform.
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Structure of Rhodolith Beds and Surrounding Habitats at the Doce River Shelf (Brazil)
Diversity, 2020Co-Authors: Vitoria L. Holz, Ricardo G. Bahia, Rodrigo L Moura, Nicholas F. Vale, Fernando C. Moraes, Claudia S. Karez, Fernanda V. Vieira, Daniela Bueno Sudatti, Leonardo T. Salgado, Gilberto M. Amado-filhoAbstract:The world’s largest Rhodolith beds have been reported from the Brazilian continental shelf. Highly biodiverse beds are located in Southeast Brazil, but ecological aspects of these beds remain unknown. Despite their ecological importance, Rhodolith beds (RBs) have recently been subjected to a severe threat, when more than 35 million cubic meters of mining residues slid down a mountainside on 5 November 2015, after a collapse of a gigantic dam upstream (the Mariana disaster), causing a huge impact on the Doce River. Our aim is to assess Rhodolith beds and adjacent coralline formations on the Doce River Shelf (DRS) after the dam collapse. This paper describes the distribution, abundance, vitality, size and shape, as well as unmapped bryozoan rich sediment formations in this area, serving as baseline knowledge for environmental monitoring. Four distinct biogenic sea bottom habitats (bryozoan bottoms, Rhodolith beds, carbonate concretions, and reefs) were recognized at different depth ranges with distribution indicated to be mostly related to the local sedimentary regime. Mud sediments dominated the seafloor up to 35 m depth. On the mid shelf, bryozoan bottoms were recorded from 35 to 45 m depth. Crustose coralline algae (CCA) occurring as Rhodoliths and carbonate concretions extend over 1953 km2 in the mid and outer shelf. Rhodolith beds predominate in these areas, totaling 1521 km2 of sea bottom and were more abundant at depths between 45 and 65 m, occupying an extensive area south of the Doce River mouth. Northward, Rhodolith beds are less abundant or absent likely due to the long-term deposition of fine sediments in this region. Carbonate concretions and reefs covered by CCA occupy sparse areas on the outer shelf (65–105 m depth). Differences in Rhodolith features recorded, including coverage, density and size, may be related to the Doce River sedimentation and related factors (e.g., hydrodynamics, depth, and light). However, since there are no previous detailed studies on RBs along the DRS, we could not assess the impact of sedimentation of dam wastes on RBs’ abundance and density. In any case, these are valuable results for the further monitoring of long-term effects. Considering that the growth of these Rhodoliths is relatively slow, and that they are affected by the sedimentation from the Doce River, the implementation of a management and conservation plan for this area is necessary in order to preserve this ecosystem.
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Heterogeneity of Rhodolith beds expressed in backscatter data
Marine Geology, 2020Co-Authors: Gabriella Aleixo Rocha, Gilberto M. Amado-filho, Rodrigo L Moura, Alex Cardoso Bastos, G. Boni, Natacha OliveiraAbstract:Abstract Rhodoliths play a major role as benthic habitats and are important calcium carbonate bio-factories. Several studies have acoustically mapped Rhodolith beds as a homogeneous habitat but spatial changes in nodule coverage, or density, commonly occur. Here, the objective is to acoustically recognize heterogeneities in Rhodolith bed structure using the response of backscatter to map changes in nodule coverage and density. High-resolution multibeam sonar (MBSS) data were acquired on April 2018, in the Marine Protection Area (MPA) Costas das Algas, located in the Espirito Santo continental shelf, Eastern Brazilian coast. Three areas were selected based on available data, totalizing 73km2 of data acquisition. Ground truth was obtained at 80 stations, using a drop camera system. Seabed classification was determined by applying an image segmentation process on multibeam sonar backscatter mosaic. Ground truth data was used to statistically show the relation between backscatter and seabed types. Results identified three classes related to Rhodoliths in different coverage densities: low Rhodolith coverage (inferior to 25% of Rhodoliths over a determined area), moderate Rhodolith coverage (between 25% and 35% of Rhodoliths), and high Rhodolith coverage (>35%). Classes associated with sediment, bioconcretions and red algae genus Peyssonelias were also identified. A map showing changes in Rhodolith coverage across the shelf depth gradient were produced. The seabed classes had a statistically significant correlation with the segmented backscatter classes. In general, higher Rhodolith coverage correlates with higher backscatter. The backscatter mosaic over the area is marked by an extensive presence of the red algae Peyssonelias, resulting in a lower correlation index, when compared to the areas with no Peyssonelia. The seabed mapping approach used in this work provided an efficacious tool to map benthic habitats and to detail nodules distribution across a Rhodolith bed. Moreover, the recognition of heterogeneities in Rhodolith bed structure provides important information for monitoring and protecting these vulnerable marine ecosystems. The main driver of the coralligenous algae nodule coverage, in the research area, seems to be the morphology of the area and the influence of mesoscale circulation.
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Drivers of biodiversity associated with Rhodolith beds from euphotic and mesophotic zones: Insights for management and conservation
Perspectives in Ecology and Conservation, 2020Co-Authors: Priscila De Cerqueira Veras, Gilberto M. Amado-filho, Rodrigo L Moura, Ivan Pierozzi-jr., Jaqueline Barreto Lino, André R. Senna, Cinthya Simone Gomes Santos, Flávio Dias Passos, Vinicius J. Giglio, Guilherme H. Pereira-filhoAbstract:Abstract Ecologically important marine ecosystems should be identified and protected, as is the case of the poorly known SW Atlantic Rhodolith beds. Understanding the main variables predicting biodiversity patterns is essential for determining priority areas for conservation. Here, we analyzed the macroinvertebrate associated with Rhodoliths from euphotic and mesophotic zones from the Fernando de Noronha Archipelago investigating the drivers of diversity distribution in this habitat. Rhodoliths were sampled and vagile macroinvertebrates (>500 μm) were classified and quantified. We verified that estimated density of organisms associated with Rhodoliths in the euphotic zone was 17 % greater than the mesophotic zone. The communities along depth zones show dissimilarities, suggesting that both environments are ecologically distinct. Comparisons with other ecosystems revealed that Rhodolith beds have similar diversity of macroinvertebrates. We also found that four of the six tested variables predicted 85 % of the variability observed in the vagile macroinvertebrate community (i.e. average diameter, depth, biomass of macroalgae and density of Rhodoliths in the bed). These variables should be taken into account in future research in modeling the biodiversity associated with the Rhodolith beds. This is especially relevant in the SW Atlantic where the Rhodolith beds seem to harbor an associated biodiversity greater than previous works had indicated, moreover, they represent one of the main ecosystems that are often superimposed with mining activities.
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Structure and composition of Rhodoliths from the Amazon River mouth, Brazil
Journal of South American Earth Sciences, 2018Co-Authors: Nicholas F. Vale, Ricardo G. Bahia, Gilberto M. Amado-filho, Juan C. Braga, Alex Cardoso Bastos, Poliana S. Brasileiro, Cláudia Santiago Karez, Fernando C. Moraes, Rodrigo L MouraAbstract:Abstract Rhodolith beds are one of the main habitats of the Brazilian Equatorial Margin continental shelf due to their wide extent and provision of ecosystem services. Northern, Central and Southern zones of the Amazon River mouth were sampled between water-depths of 23 and 120 m, covering a continental shelf area of 9500 km2, to characterize the structure and composition of Rhodoliths along depth gradients and related river plume influence. The deepest Rhodoliths consist of a thin algal/bryozoan/encrusting foraminifer cover around relatively large nuclei that determine the nodule size and shape. At 120-m depth in the Northern zone the nuclei are made of fragments of invertebrate boundstone or oolite rudstone, whereas at 100-m depth in the Central zone the nuclei consist of sandstone clasts. In both cases, the nuclei are fragments of sedimentary rocks that accumulated on the outer shelf during significantly lower sea level. Low-light levels prevent substantial growth of the algal cover around the nuclei. Reduced illumination an d high nutrient levels led to the composition of Rhodoliths at 95-m depth in the Northern zone, predominantly built by bryozoans with subordinate coralline algae around small bioclastic nuclei. In the Central zone at 50–55 m depths, coralline algae are the main components of mostly sub-spheroidal Rhodoliths. They have relatively recent ages of hundreds of years or show two phases of growth with the older phase beginning 1300 years ago and then being interrupted from about 1000 years BP to 600 years BP. All this suggests relatively high burial rates due to sediment flux, changing in time to favor exhumation after burial in some instances. The Rhodoliths from 23 m in the Southern zone are growing under a low influence of the river plume and have the highest diversity of coralline algae and other builders. The Rhodolith structure in the different sampling zones and depths reflects plume influence on light penetration, nutrient and organic matter levels, and sedimentation on the shelf, determining residence times of Rhodoliths on the seafloor before burial.
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South Atlantic Rhodolith Beds: Latitudinal Distribution, Species Composition, Structure and Ecosystem Functions, Threats and Conservation Status
Rhodolith Maërl Beds: A Global Perspective, 2017Co-Authors: Gilberto M. Amado-filho, Ricardo G. Bahia, Guilherme H. Pereira-filho, Leila L. LongoAbstract:The largest continuous latitudinal distribution of Rhodolith beds occur in the South Atlantic Ocean. Up to now Rhodolith beds were referred exclusively to the western portion of the South Atlantic. Here we describe the recent advances in the South Atlantic taking into account latitudinal distribution, species composition, structure and ecosystem functions, threats and conservation status. Rhodolith beds have been mapped and ecologically described from extensive areas of the continental shelf (Abrolhos Bank), seamounts tops (Vitoria Trindade Chain), insular shelfs of oceanic islands (Fernando de Noronha Archipelago) and atolls (Rocas Atoll). Thirty three species of crustose coralline algae were recorded forming Rhodoliths. Despite some initiatives, the richness of fauna associated with Rhodoliths in SW Atlantic is still poorly known. Specific microbiome described associated with Rhodoliths indicates important role in biomineralization process. The environmental services provided by the recently described Rhodolith beds (Abrolhos Banks and Vitoria Trindade Seamounts) as calcium carbonate production, increase habitat complexity, benthic diversity and associated fish assemblages justify urgent actions to protect these ecosystems.
Markes E. Johnson - One of the best experts on this subject based on the ideXlab platform.
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Heterozoan carbonate-enriched beach sand and coastal dunes—with particular reference to Rhodoliths, Dirk Hartog Island, Shark Bay, Western Australia
Facies, 2018Co-Authors: Adela S. Harvey, Markes E. Johnson, Robert HarveyAbstract:This is a preliminary interdisciplinary study on the enrichment of heterozoan carbonates on Dirk Hartog Island, Shark Bay, Western Australia, with particular reference to Rhodolith (free-living non-geniculate) coralline algae. The current study aims to investigate the geological impact of shallow-water Rhodoliths in Shark Bay, as well as fill critical information gaps on the biogeographical distribution of Rhodoliths in Australia. We analyzed the composition of sand from eight sites (totaling 21 beach and sand dune samples) on the eastern (windward) shore of the island, and investigated the origin of the coralline algal grains. Heterozoan carbonates (shell, geniculate coralline algae grains, and Rhodolith grains) together comprised 3–84% of the carbonate-enriched beach and dune sand samples. While shell fragments often comprised the highest percentage (up to 73%), Rhodolith grains (up to 27%) were found in 12 of 21 samples, with Rhodolith grains also occurring in two dune samples. Geologically, the study has shown that Rhodoliths and Rhodolith beds are important shallow-marine habitats in Shark Bay, with a proven capacity to enrich beach/dune sands in Shark Bay and potentially other areas along the Australian coast. Biogeographically, the study confirmed the presence of a previously undescribed shallow Rhodolith bed in Shark Bay (the first bed documented on the Western shore) with the possibility of a third bed near Sandy Point on Dirk Hartog Island. It also confirmed the presence of Rhodolith forming Neogoniolithon brassica-florida and Lithophyllum sp. in Shark Bay, and is the first record of Hydrolithon reinboldii Rhodoliths in Australia.
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Taphonomic Range and Sedimentary Dynamics of Modern and Fossil Rhodolith Beds: Macaronesian Realm (North Atlantic Ocean)
Rhodolith Maërl Beds: A Global Perspective, 2016Co-Authors: Markes E. Johnson, B. Gudveig Baarli, Carlos Marques Da Silva, Ricardo S. Ramalho, Eduardo Mayoral, Ana Santos, Jorge Ledesma-vázquez, Ana Cristina Rebelo, Mário CachãoAbstract:Distribution of living Rhodoliths in the Macaronesian realm is limited by extensive rocky shores and narrow insular shelves that rapidly drop off beyond the 50-m isobath. Wind and wave erosion is most intense on north and northeast-facing shores due to the prevailing northeasterly trade winds over much of the region. Southern shores offer more sheltered, leeward settings. Rhodolith beds tend to thrive on eastern shores with strong long-shore currents and southeastern shores that benefit from wave refraction. Rhodoliths are not entirely absent off northern shores, but may fail to reach maximum size before being washed ashore to make berms and beaches. Islands considered in greater detail in this survey include Santiago, Maio, and Sal from the Cape Verde Islands, Fuerteventura and the related islet of Lobos in the Canary Islands, Selvagem Grande and Pequena from the Savage Islands, Porto Santo in the Madeira Islands, and Santa Maria in the Azores. This contribution expands on the concept that living Rhodoliths enter the fossil record through a range of taphofacies defined by the degree of breakage and corrosion and further characterized by sedimentological criteria regarding the amount of matrix and packing among bioclasts. Rhodolith deposits in Macaronesia seldom reflect settings under natural growth conditions. Rather, Rhodoliths are subject to transportation and post-mortem disintegration resulting in the accumulation of Rhodolith materials captured by subtidal storm deposits, tidal pools and platform over-wash deposits, as well as beachrock, beach, berm, hurricane, tsunami, and coastal dune deposits. Some of this material is transferred farther offshore, but exposed island strata show a tendency for shoreward migration of taphofacies. Rhodolith beds provide a habitat for some species of marine invertebrates, including epifaunal and infaunal elements directly associated with whole Rhodoliths and these features play a role in Rhodolith biostratinomy.
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Rocking around a volcanic island shelf: Pliocene Rhodolith beds from Malbusca, Santa Maria Island (Azores, NE Atlantic)
Facies, 2016Co-Authors: Ana Cristina Rebelo, Markes E. Johnson, Ricardo S. Ramalho, Michael W. Rasser, Andreas Kroh, Carlos Melo, Alfred Uchman, Björn Berning, Luís Silva, Vittorio ZanonAbstract:Rhodoliths are a common producer of carbonates on modern and ancient shelves worldwide, and there is growing evidence that they thrive on volcanic insular shelves. However, little is still known on how Rhodoliths cope with the demands of this particularly dynamic environment. In this study, the focus is placed on fossil Rhodoliths from a Pliocene sequence at Santa Maria Island, Azores, in order to gain further insight into the life cycle (and death) of Rhodoliths living within a mid-ocean active volcanic setting. These Rhodoliths occur as a massive accumulation within a larger submarine volcano-sedimentary sequence that was studied from the macro- to the micro-scale in order to reconstruct the paleoenvironmental conditions under which the Rhodolith accumulation was deposited and buried. All fossil Rhodoliths from this setting are multi-specific and demonstrate robust growth forms with a lumpy morphology. Moreover, taphonomical analyses show the succession of several destructive events during Rhodolith growth, suggesting life under a highly dynamic system prior to stabilization and burial. The Rhodoliths therefore tell a story of an eventful life, with multiple transport and growth stages, owing to the environment in which they lived. Transport and deposition to their final resting place was storm-associated, as supported by the general sedimentary sequence. In particular, the sequence features an amalgamation of tempestites deposited under increasing water depths, sediment aggradation, and before burial by volcanic activity. This transgressive trend is also attested by the overall characteristics of the volcano-sedimentary succession, which exhibits the transition to subaerial environment in excess of 100 m above the Rhodolith bed.
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Recent Rhodolith Deposits Stranded on the Windward Shores of Maio (Cape Verde Islands): Historical Resource for the Local Economy
Journal of Coastal Research, 2016Co-Authors: Markes E. Johnson, B. Gudveig Baarli, Carlos Marques Da Silva, Mário Cachão, Ricardo S. Ramalho, Ana Santos, Eduardo MayoralAbstract:ABSTRACT Johnson, M.E.; Baarli, B.G.; da Silva, C.M.; Cachao, M.; Ramalho, R.S.; Santos, A., and Mayoral, E.J., 2016. Recent Rhodolith deposits stranded on the windward shores of Maio (Cape Verde Islands): Historical resource for the local economy. Maio is a volcanic island with an area of 269 km2 in the Cape Verde archipelago off the west coast of Africa. Although considered a leeward island, it absorbs NE trade winds that typically register 5 to 6 on the Beaufort Scale (moderate to fresh breeze). The trade winds produce ocean swells commonly 3.5 m in height that scour the island's north coast but also generate eastern longshore currents. Outcrops with Pleistocene Rhodoliths occur on the SE and south shores and include lithified dunes mainly composed of crushed Rhodolith debris. In contrast, the modern beaches and Pleistocene dunes on the more sheltered west coast are practically devoid of Rhodoliths. Present-day Rhodolith banks off the north coast would seem to be precluded by intense wave action. This ...
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Rhodoliths, uniformitarianism, and Darwin: Pleistocene and Recent carbonate deposits in the Cape Verde and Canary archipelagos
Palaeogeography Palaeoclimatology Palaeoecology, 2012Co-Authors: Markes E. Johnson, B. Gudveig Baarli, Carlos Marques Da Silva, Mário Cachão, Ricardo S. Ramalho, Eduardo Mayoral, Jorge Ledesma-vázquez, Ana SantosAbstract:Abstract Visiting “St. Jago” (Santiago) in the Cape Verde Islands in 1832 and again in 1836 aboard HMS Beagle , Charles Darwin was the first to trace and describe the tri-part sequence of white limestone and sandstone beds stratigraphically located between two levels of basalt exposed almost uninterrupted for 10 km along coastal cliffs. The Pleistocene carbonate sediments dominated by Rhodoliths and Rhodolith debris accumulated on a basalt shelf and subsequently became buried by subaerial and submarine basalt on the southeast coastline of Santiago. The main goal of this contribution is to re-examine Darwin's stratigraphic sequence. The secondary goal is to provide a general taphonomical model based on the observation of Recent Rhodolith deposits for evaluation of fossil Rhodolith assemblages. Environmental uniformitarianism is employed to understand the depositional history of the southern Santiago Rhodolith-bearing strata. The mixed clastic-carbonate sequence includes a basalt-derived basal conglomerate with an intertidal to shallow subtidal fossil assemblage mainly denoted by limpets and oysters. Upper layers typically demonstrate swaley and hummocky cross stratification incorporating Rhodolith debris further modified by bioturbation. Pillow basalts from 10 to 18 m in thickness succeeded by subaerial flows imply swift burial of the carbonate succession under equivalent water depths. The calcareous nannofossil assemblage was investigated to more precisely date the deposits. Darwin's paleoshore is reinterpreted to represent two different transgressions occurring between approximately 1.1 and 0.7 Ma. Taphonomic grades from whole Rhodoliths to finely crushed Rhodolith debris observed under present-day conditions on Maio (Cape Verde Islands) and Fuerteventura (Canary Islands) were used to model Rhodolith preservation and to constrain the depositional settings to which Rhodoliths may be transported from the offshore banks where they naturally thrive. Coastward transport of Rhodoliths commonly ends with deposition in subtidal storm beds, tidal pools, and platform over-wash deposits, as well as beach, berm, hurricane, tsunami, and coastal dune deposits.
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Natural History of Rhodolith/Maërl Beds: Their Role in Near-Shore Biodiversity and Management
Rhodolith Maërl Beds: A Global Perspective, 2016Co-Authors: Rafael Riosmena-rodríguezAbstract:Rhodolith/maerl beds are living and dead aggregations of free-living non-geniculate coralline algae that cover extensive benthic areas in recent oceans and are common in fossil deposits. They are slow growing organisms and can be long-lived (>100 years), distributed over a wide depth range from intertidal sites to 270 m. Rhodolith/maerl beds are a common feature of modern and ancient carbonate shelves worldwide that represent a sedimentary transition from sandy/muddy areas to the rocky substrate. They are bioengineers and provide a three-dimensional habitat for associated species. It has been demonstrated that Rhodolith/maerl grounds are a suitable habitat for multispecies recruitment and provide refuge for juvenile life stages of commercially important shellfish species. Rhodoliths are resilient to a variety of environmental disturbances, but can be severely impacted by harvesting these commercial species, ocean acidification or global warming. The value of Rhodoliths as a unique biotope around the world is under threat from different kinds of human activities. Despite the importance of Rhodolith/maerl beds in the marine environment, a major limitation for protection is the lack of a clear definition of an ecosystem. A thorough review of the literature revealed a total of 12 vernacular/scientific terms that have been applied to free-living coralline red algae and these should be treated as synonyms. The Challenger Expedition (1872–1876) was one of the first voyages that promoted the understanding of the rich flora and fauna associated with coralline deposits. During the nineteenth century additional surveys in other areas of the world have confirmed the value of this ecosystem. During twentieth and twenty-first centuries many researchers have produced a vast scientific literature, documenting the importance of Rhodolith/maerl, to understand their relevance regarding biodiversity in nearshore habitats. The relevance includes the description of new species or where the distribution of poorly known species has been extended, but more importantly the high number of associated species which includes species under protection, species ecologically relevant or species which are part of a formal fisheries. As a consequence of the concern about the state of the ecosystems in Europe at the end of the twentieth century, the EU developed a network of protected areas known as Natura 2000 sites. A series of publications on the conservation status of the maerl/Rhodoliths in Atlantic and Mediterranean waters, Brittany, Gulf of California, and their relationship with fisheries, stated clearly that the health of Rhodolith habitats in some areas of the world is decreasing, and there is an urgent need for management strategies. The combination of the interest in developing Rhodolith/maerl conservation in other countries, the decline of the French Atlantic maerl deposits, and the correlation of Rhodolith/maerl presence in or near oil deposits has motivated the exploration of Rhodoliths in other areas such as Brazil, Mexico, Australia and New Zealand. Understanding is increasing about the ecological role of Rhodoliths in nearshore environments worldwide, the biodiversity associated with Rhodoliths, and how human activities are having an increasing impact. The recognition of the importance of Rhodolith beds as biodiversity centers has increased with the number of published papers and the growth in knowledge about the taxonomic status of the associated species.
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Phylogenetic analysis of Rhodolith formation in the Corallinales (Rhodophyta)
European Journal of Phycology, 2014Co-Authors: Jazmin J. Hernandez-kantun, Rafael Riosmena-rodríguez, Jason M. Hall-spencer, Viviana Peña, Christine A. Maggs, Fabio RindiAbstract:Although the ecological importance of Rhodolith (maerl, free-living coralline algae) beds is well-known, Rhodolith-forming species have been neglected in molecular phylogenetic studies. This is the first molecular systematic study aimed at understanding whether the Rhodolith habit is a fixed feature in lineages and determining the relationship (phylogenetic vs. environmental) between Rhodolith and crustose habits. Phylogenetic relationships of Rhodolith-forming species and encrusting coralline algae at generic and species levels were analysed using SSU rDNA and psbA sequences. Extensive sampling in the European North Atlantic, Pacific and Caribbean Mexico of Phymatolithon, Lithothamnion, Lithophyllum and Neogoniolithon taxa forming Rhodoliths and crusts was accompanied by examination of type or topotype material. Phylogenetic reconstruction showed that Neogoniolithon contained a monophyletic group of Rhodolith-forming species whereas other Rhodolith-formers were closely related to encrusting forms in the ...
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Rhodolith beds in the South-East Pacific
Marine Biodiversity, 2014Co-Authors: Erasmo C. Macaya, Rafael Riosmena-rodríguez, Roland R. Melzer, Roland Meyer, Günter Försterra, Vreni HäussermannAbstract:Rhodolith or maerl are the most common terms used for free living coralline red algae which live and produce sediments (Nelson 2009). They are common in the North Atlantic, Mediterranean, tropical West Atlantic, Gulf of California, Southern Japan, Western Australia and New Zealand (Foster 2001). Rhodolith beds reach the deepest section of the euphotic zone, their maximum is at approximately 286 m (Foster 2001). These beds provide habitat, refuge, settlement sites and nursery ground for a variety of marine life, but also information about past and present climate changes and represent an important economic resource used as fertilizer in agriculture (Foster 2001). Climate change, ocean acidification and fisheries have negative impacts on Rhodolith beds, resulting in calls for conservation (Hall-Spencer et al. 2010). In the Eastern Pacific, Rhodolith beds are known from the Gulf of California to Alaska and the Galapagos Islands, Costa Rica, and Panama. The knowledge on coralline algae along the Chilean coast is still scarce focusing on crustose and non free-living forms (e.g. Vidal et al. 2003). Here we give the first record of Rhodolith beds in the South-East Pacific, based on scientific expeditions to Guarello Island (Madre de Dios Archipelago, c. 50°S 75°W), Melinka and Amita Island (Guaitecas, c. 43°S 73°W,), and Robinson Crusoe Island (Juan Fernandez Archipelago, c. 33°S 78°W). At three sites, Robinson Crusoe, Guarello and Amita, we found areas of average downward slope on rocky ground mixed with sediment spots. At depths from about 10–25 m many of these spots were covered with Rhodolith beds showing a lumpy growth form in Robinson Crusoe (Fig. 1a) and fruticose habit in Guarello and Amita (Fig. 1b, c). Plants were approximately 5 cm in diameter and had one or two branches per cm in lumpy material and four to six branches per cm in fruticose material. In Melinka (Fig. 1d), Rhodoliths with a lumpy growth form were found at intertidal pools. These records extend the distribution of Rhodoliths and raises interesting questions about their distribution, taxonomy, evolution and ecology. Thus, Rhodolith beds in the South-East Pacific need to be analyzed in detail in the future and their role in coastal processes evaluated.
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Community structure of Rhodolith-forming beds on the central Brazilian continental shelf
Helgoland Marine Research, 2014Co-Authors: Alexandre B. Villas-boas, Rafael Riosmena-rodríguez, Marcia Abreu De Oliveira FigueiredoAbstract:The community structure of Rhodoliths beds in the central Brazilian continental shelf was studied under the hypothesis that nongeniculate coralline algae are the major contributors of the individual Rhodoliths. Samples were collected from five localities within a single area at 17–18 m depth. At each locality, Rhodoliths were collected in 10 random quadrat samples along a 20-m transect. Our results show that dead cores of Rhodoliths were significantly composed by nongeniculate coralline red algae rather than bryozoans, corals, or inorganic material. The live outer layers of the Rhodoliths are composed mainly of 7 species of nongeniculate red coralline algae ( Lithophyllum coralline, L. johansenii, L. depressum, L. stictaeformis, Neogoniolithon brassica - florida, Spongites fruticosus , and Lithothamnion muellerii ) associated with other encrusting organisms such as bryozoans, sponges, corals, barnacles, and Peyssonnelia red algae. Significant differences were found in the proportion of Lithophyllum species in relation to other red coralline algae found in this study. Our results show that on the Brazilian continental shelf, the Rhodolith-forming species are quite higher in size than in any other studied areas in the world. There was no difference in the proportion of live-to-dead Rhodolith materials, suggesting an old bed deposit. Also, the amount of calcium carbonate material in the specimens is relevant to take in account in terms of the CO_2 balance worldwide.
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Rhodoliths and Rhodolith beds
2013Co-Authors: Michael S. Foster, Rafael Riosmena-rodríguez, Gilberto M. Amado Filho, Nicholas A. Kamenos, Diana L StellerAbstract:Rhodolith (maerl) beds, communities dominated by free living coralline algae, are a common feature of subtidal environments worldwide. Well preserved as fossils, they have long been recognized as important carbonate producers and paleoenvironmental indicators. Coralline algae produce growth bands with a morphology and chemistry that record environmental varia- tion. Rhodoliths are hard but often fragile, and growth rates are only on the order of mm/yr. The hard, complex structure of living beds provides habitats for numerous associated species not found on otherwise entirely sedimentary bottoms. Beds are degraded locally by dredging and other an- thropogenic disturbances, and recovery is slow. They will likely suffer severe impacts worldwide from the increasing acidity of the ocean. Investigations of Rhodolith beds with scuba have enabled precise stratified sampling that has shown the importance of individual Rhodoliths as hot spots of diversity. Observations, collections, and experiments by divers have revolutionized taxonomic stud- ies by allowing comprehensive, detailed collection and by showing the large effects of the environ- ment on Rhodolith morphology. Facilitated by in situ collection and calibrations, corallines are now contributing to paleoclimatic reconstructions over a broad range of temporal and spatial scales. Beds are particularly abundant in the mesophotic zone of the Brazilian shelf where technical diving has revealed new associations and species. This paper reviews selected past and present research on Rhodoliths and Rhodolith beds that has been greatly facilitated by the use of scuba.