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-Rhodoliths beds. From South Espírito Santo: A) Shallow SES, 20 m depth. B) Deep SES, 50 m depth. From Abrolhos Continental Shelf: C) Shallow ACS, 30 m depth. D) Deep ACS, 55 m depth.
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The structure and composition of rhodoliths in two regions of the Brazilian shelf, Abrolhos Continental Shelf (ACS) and South Espírito Santo State (SES) were examined and compared. Rhodoliths were sampled at depth ranges of 10–20 m and 50–60 m in SES, and 20–30 m and 50–75 m in ACS. Rhodoliths in SES are algal boundstones, built mainly of melobesio...
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Context 1
... differences in structure and composition were observed between rhodoliths from sampling sites within the same depth range (hereafter termed zone) in any of the regions. By contrast, rhodoliths from different zones (Fig. 2) show marked dissimilarity in several features of their internal structure and composition. The main characteristics of rhodoliths from each region and zones are described in the following ...
Context 2
... rhodolith size ranges from ~ 1 to ~ 17 cm (Fig. 3, Table 2). Although spheroidal to subspheroidal shapes are the most common, subdiscoidal to discoidal rhodoliths account for 38% of the nodules measured (Table 2). As in the shallower ACS nodules, thin encrusting coralline algae partially or totally cover a structureless mass resulting from repeated phases of boring and filling the original ...
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Citations
... Rhodoliths have been reported from numerous fossil and modern environments (e.g., Foster et al. 2020;Braga et al. 2012;Kamenos et al., 2017;Aguirre et al. 2017), from shallow-to deep-water depths (e.g., Figueiredo et al. 2012;Brasileiro et al. 2018) and tropical to polar marine environments (e.g., Teichert et al. 2014;Amado-Filho et al. 2017). Rendina et al. (2022) show that most scientific works related to rhodoliths are associated with terms such as macroalgae carbonate/sedimentology, paleontology, and biodiversity/fauna. ...
... Rhodoliths with an extremely bioeroded inner part and intense lithification of the infilled borings have been described elsewhere in mesophotic environments (Reid and Macyntire 1988;Matsuda and Iryu 2011;Brasileiro et al. 2018). Sedimentation rate and frequency of overturning control the settlement and residence time of boring organisms, which is longer in deeper waters (. 40 m) (Bassi et al. , 2013(Bassi et al. , 2020Brasileiro et al. 2018). ...
... Rhodoliths with an extremely bioeroded inner part and intense lithification of the infilled borings have been described elsewhere in mesophotic environments (Reid and Macyntire 1988;Matsuda and Iryu 2011;Brasileiro et al. 2018). Sedimentation rate and frequency of overturning control the settlement and residence time of boring organisms, which is longer in deeper waters (. 40 m) (Bassi et al. , 2013(Bassi et al. , 2020Brasileiro et al. 2018). New bioerosion can take place in lithified infills and cements, giving way to cycles of bioerosion-sediment filling-cementation (Bromley 1994). ...
Rhodoliths are nodules mainly composed of crustose coralline algae with subordinate encrusting organisms, formed by successive overlapping encrustation. The subspheroidal rhodoliths from the Vitória-Trindade Seamount Chain (Jaseur Seamount and Trindade Island shelf; Brazil, southwestern Atlantic), sampled at water depths from 65 to 74 m, were built by crustose coralline algae (Harveylithon, Lithophyllum, Lithothamnion, Mesophyllum, Roseolithon, and Sporolithon) and subordinated encrusting foraminifera (agglutinated, unidentified hyaline, and Homotrema rubrum), bryozoans, serpulids, and balanids. Successive taphonomic phases of bioerosion, boring filling, and cement precipitation modified the original rhodolith inner structures resulting in a complex structureless mass of coralline algal fragments, encrusting organisms, borings, lithified fine-grained sediment, and carbonate cement. Borings include the ichnogenera Entobia (produced by etching sponges), Gastrochaenolites (boring bivalves) and Trypanites (polychaetes and sipunculid worms). The lithification of the material filling the borings (micrite and carbonate cements) created new substrates for subsequent bioerosion. Radiocarbon dating of selectively sampled invertebrate and algal skeletons in the rhodolith interior yielded calibrated ages of hundreds of years (up to 912 ± 152 years cal. BP on the Trindade insular shelf and up to 763 ± 131 years cal. BP on Jaseur Seamount). These values indicate growth rates from 0.1 to 0.5 mm/year, which are significantly higher than those recorded from rhodoliths at similar depths on the Brazilian shelf. Low sedimentation settings and high productivity at the tops of the seamounts and island shelf promoted the growth of nodule frame builders, both autotrophs and heterotrophs, and favored continuous activity of bioeroders.
... Occasional or frequent overturning of biogenic nodules, generally achieved by currents and/or biological activity, is likely to be a prerequisite for nodule accretion (e.g., Hottinger, 1983;Prager and Ginsburg, 1989;Aguirre et al., 2017). The different shapes and internal structures of these nodules record changes in environmental factors, such as hydrodynamic conditions, substrate characteristics, trophic levels and sedimentation rate (e.g., Adey and Macintyre, 1973;Prager and Ginsburg, 1989;Foster et al., 2013;Aguirre et al., 2017;Sletten et al., 2017;Brasileiro et al., 2018;Tâmega et al., 2019;O'Connell et al., 2021;Bracchi et al., 2023). It has been assumed that changes in these environmental factors produce similar effects in rhodolith and macroids with different proportions of coralline algae and encrusting foraminifera (e.g., Prager and Ginsburg, 1989;Aguirre et al., 1993;Baarli et al., 2012). ...
... Abrupt transitions in age have been noted from older bored and infilled cores to the still-living outer layers, indicating major discontinuities in growth (e.g., McMaster and Conover, 1966;Focke and Gebelein, 1978;Bosence and Pedley, 1982;Prager and Ginsburg, 1989;Littler et al., 1991;Halfar et al., 2013;Brasileiro et al., 2018;Vale et al., 2018;Lewis et al., 2017). These abrupt transitions in age have been interpreted as due to the intermittent growth of rhodolith beds, interrupted by changes in water energy and sedimentation rate (Littler et al., 1991;Figueiredo et al., 2015;Vale et al., 2022). ...
... Worm boring Trypanites and Maeandropolydora are the most commonly recognized boring traces in nucleated rhodoliths, sponge boring Entobia and bivalve boring Gastrochaenolites being rare or absent. Near-permanent motion of nodules, low nutrient supplies, prolonged burial, substrate instability, small size of the carbonate nodule, competition with other borers, and high sedimentation rates are limiting factors for the settlement and thriving of bioeroders (Hallock 1988;Perry 1998;Martin 1999;Hutchings 2008;Bassi et al. 2011Bassi et al. , 2012Bassi et al. , 2020Brasileiro et al. 2018;Cardona-Gutiérrez and Londoño-Cruz 2020). Shallow-water subtidal sampling sites of St. Barth Island and Flat Point Beach are contrasted settings in terms of water clarity, water temperature, nature and texture of bottom substrates, and available trophic resources but compare well in terms of hydrodynamic conditions. ...
Encrusting (Ei), Macroboring (Mi), and Dissymmetry (Di) indices are proposed as quantitative descriptors of biogenic nodules. (Ei) measures the amount of encrustation, (Mi) the contribution of boring traces affecting the internal structure of nodules, and (Di) the regularity of the biogenic accretion around the nucleus. The latter has been used to construct a classification scheme of possible shapes for encrustations. Raw data to calculate the indices were obtained from numerical treatments of digitized photographs of nodule cross-sections. The morphometric (Di) and taphonomic (Ei and Mi) indices have been calculated for carbonate nodules from subtidal temperate and tropical settings in New Zealand (Flat Point Beach) and in the Caribbean (St. Bartholomew Island), respectively. Results for nucleated rhodoliths collected from shallow high-energy settings in these two climatic settings show that their morphometric and taphonomic characters are not species-specific (Lithoporella/Mastophora rhodoliths from St. Barth, and Lithothamnion-Sporolithon rhodoliths from New Zealand), but depend instead on hydrodynamic conditions and on the original shape of nuclei. Acervulinid macroids sampled in deeper waters (28 m) off St. Barth are nucleus-free and have a Macroboring index (Mi) significantly higher than that of rhodoliths from shallower environments, due to discontinuous influence of waves and currents, and low sedimentation rates.
The quantitative descriptors proposed here might: (1) complement the characterization of biogenic nodules in specific depositional environments; (2) aid in hydrodynamic and paleoenvironmental reconstructions of biogenic nodule-bearing deposits; and (3) constitute valuable tools in future comparative studies.
... Light at bottom, which depends on depth and turbidity, as well as CaCO 3 saturation state and water temperature, are among the main predictors of RB occurrence and community structure variation [e.g., 19,23,60]. The ESA shelf is in a tropical-subtropical transition [25] with sharp differences in sedimentation patterns [61], sea surface temperature and water column stratification (S1 Fig) within less than two latitudinal degrees. For instance, among the region's reefs, the dominant coral in the northerly Parcel dos Abrolhos reefs, Mussismillia braziliensis, does not occur in the Esquecidos reefs (70 km south of the former) and southwards. ...
... Conversely, fish species that are abundant in subtropical reefs such as the dusky grouper (Epinephelus marginatus) do not occur, or are extremely rare, northwards of Espírito Santo [45]. Rhodolith beds' size and composition also present a sharp contrast within the ESA shelf [61]. Macroalgae cover in RBs is at least 5 times higher eastward to the Abrolhos reefs than in the southerly Paleovalleys Shelf [21,23,31], where macroalgae diversity, richness and cover is concentrated in the nearshore lateritic reefs. ...
Continental shelves encompass gently sloped seascapes that are highly productive and intensively exploited for natural resources. Islands, reefs and other emergent or quasi-emergent features punctuate these shallow (<100 m) seascapes and are well known drivers of increased biomass and biodiversity, as well as predictors of fishing and other human uses. On the other hand, relict mesoscale geomorphological features that do not represent navigation hazards, such as incised valleys (IVs), remain poorly charted. Consequently, their role in biophysical processes remains poorly assessed and sampled. Incised valleys are common within rhodolith beds (RBs), the most extensive benthic habitat along the tropical and subtropical portions of the mid and outer Brazilian shelf. Here, we report on a multi-proxy assessment carried out in a tropical-subtropical transition region (~20°S) off Eastern Brazil, contrasting physicochemical and biological variables in IVs and adjacent RBs. Valleys interfere in near bottom circulation and function as conduits for water and propagules from the slope up to the mid shelf. In addition, they provide a stable and structurally complex habitat for black corals and gorgonians that usually occur in deeper water, contrasting sharply with the algae-dominated RB. Fish richness, abundance and biomass were also higher in the IVs, with small planktivores and large-bodied, commercially important species (e.g. groupers, snappers and grunts) presenting smaller abundances or being absent from RBs. Overall, IVs are unique and vulnerable habitats that sustain diverse assemblages and important ecosystem processes. As new IVs are detected by remote sensing or bathymetric surveys, they can be incorporated into regional marine management plans as conservation targets and priority sites for detailed in situ surveys.
... The mud in the southern sector and the mesophotic bioconstructions seem to be temporally and spatially related. The mesophotic reefs over the Brazilian Margin started to develop during the Holocene Marine Transgression at last 7 kyr BP (Brasileiro et al., 2018). During this period, the La Plata River plume reached the Santos Basin (green arrow in Fig. 8) at 4.7 kyr BP (Mahiques et al., 2020(Mahiques et al., , 2004Mathias et al., 2014). ...
... During this period, the La Plata River plume reached the Santos Basin (green arrow in Fig. 8) at 4.7 kyr BP (Mahiques et al., 2020(Mahiques et al., , 2004Mathias et al., 2014). Reefs in this sector were buried by mud accumulation at an extraordinary rate of 134 mm kyr −1 (Brasileiro et al., 2018;Mahiques et al., 2004). ...
The Santos Basin mesophotic zone comprises one area of 104,915 km², occupying 78% of the entire basin. Santos Basin is one of the most under stress and sensitive marine regions in the Brazilian territory due to several major ports, Oil & Gas industry, and coastal marine environmental management areas. Scientific literature recognizes that rhodolith beds and biogenic rigid-bottom patches occur on the shelf, but because lack of high-resolution seismic data, these seabed features are not yet wholly mapped at Santos Basin. However, an unprecedented gathering of historical depth sounding points and surface sediment data collection, in conjunction with an extensive field campaign of seabed sampling and sub-bottom shallow seismic records, points out new evidence of biogenic sediment distribution reefal structures in the Santos Basin. The patches of calcareous algae crusts, terraces mounds, pinnacles, and free-living rhodolith beds compose the carbonate facies on the outer shelf. Rugged bottom relief and pinnacles up to 10 m in height correlate with carbonate gravels and sandy areas. Bioconstructions are more common northward and gradually decrease southward. Geomorphological features such as rugged bottom relief might indicate the occurrence of mesophotic bioconstructions off Paraná, and Santa Catarina State coast. The mesophotic bioconstructions have evolved through four stages: 1- LGM fully sposed shelf, 2- sea-level transgression and bioconstrutions pioneers, 3- influence of the La Plata plume at the southern sector, and 4- establishment of mud patches in the northern sector due to local input.
... The rhodoliths analyzed in this study started to grow between 1.9 and 1.8 ka cal BP, a long time after the Holocene flooding of the SEAL shelf [35]. The bathymetry of the investigated rhodolith beds lies within the large range of rhodolith beds in Brazil, which occur between 12 and 95 m depth [59][60][61][62][63][64][65]. Temperature, nutrients, sedimentation and water current velocity are considered the main environmental drivers of rhodolith development in the Brazilian ecoregions [65]. ...
... Shelf-incised valleys, canyons and riverine plumes led to the patchy distribution in large-scale rhodolith beds on the SEAL shelf ( Figure 1). On wider shelves, such as the Abrolhos shelf, which also has low sediment input, rhodolith beds are extensive and more continuous [63,66]. At a smaller scale, within individual rhodolith beds mapped on the SEAL shelf (Figure 1), the distribution of rhodoliths is patchy with varying rhodolith density. ...
... The concentric arrangement and high proportions of constructional void in rhodolith covers in sites of the south sector of the SEAL shelf are common in shallow-water rhodoliths in the south Espirito Santo and Rio Doce shelves [59,63]. High proportions of constructional voids were interpreted as reflecting low energy conditions [63], whereas concentric arrangements with little destruction by bioerosion indicate relatively short residence times of rhodoliths on the seafloor before burial. ...
A Margem Continental Amazônica (MCA) e Bacia Sergipe-Alagoas (SEAL) se destacam pelo desenvolvimento de formações carbonáticas/siliciclásticas, desde períodos geológicos passados até o presente. O foco deste estudo foi avaliar a evolução das estruturas recifais da MCA e rodolitos da Bacia SEAL após o Último Máximo Glacial (LGM). Com os resultados obtidos, foi possível definir a estrutura das formações recifais; as fácies dominantes nas amostras estudadas, caracterizando-as nas distintas idades de sua formação. Três principais formações foram reconhecidas em diferentes faixas de profundidade: bancos de rodolitos, concreções carbonáticas e ‘recifes’. Um total de 22 morfo-taxons de algas vermelhas (rodofíceas) foram identificadas nos locais de estudo. A transição entre a plataforma externa e a quebra da plataforma no Setor Norte da MCA traz consigo uma série de estruturas proeminentes de alto relevo. Os topos destas feições estão entre 110-165 m de profundidade e parecem ter se originado durante o baixo nível do mar (NM), através da erosão dos arenitos Pleistocênicos. Os depósitos carbonáticos e siliciclásticos acumulados no topo dessas feições durante o LGM e deglaciação precoce foram gradualmente submersos pela elevação do NM e pela subsidência. Uma fina camada de organismos incrustantes (algas coralináceas, esponjas, briozoários e serpulídeos) coloniza atualmente a maioria dessas superfícies e contribui para a agregação de uma camada carbonática fina com siliciclásticos de grão fino. O Setor Central, em frente à foz do rio, está associado ao acúmulo de sedimentos a longo prazo e carece de uma ruptura na plataforma. No entanto, comunidades bentônicas vivas ocorrem em afloramentos rochosos. O Setor Sul é menos influenciado pela pluma do rio e inclui uma plataforma mais rasa e um cânion proeminente. Os afloramentos rochosos do Pleistoceno a 180 m carregam coberturas finas de uma comunidade bentônica dominada por esponjas e algas coralináceas, que são responsáveis pelo acúmulo de um depósito fino de bioclastos, areia de quartzo e lama sobre o substrato rochoso. Assim, os ‘recifes’ da plataforma externa e a margem mesofótica da Amazônia são tipicamente rochas antigas erodidas, colonizadas por organismos incrustantes durante o LGM e deglaciação formando uma camada carbonática, que agora suporta uma comunidade mesofótica. Operações com Veículo Operado Remotamente e a amostragens com rede de arrasto de fundo na Bacia SEAL revelaram a ocorrência de bancos de rodolitos entre 25-54 m de profundidade. Nas profundidades mais rasas, rodolitos ramificados (maërl) aparecem nos leitos de ondulações (ripples) e outros rodolitos não ramificados ocorrem associados a corais e esponjas circundadas por areia bioclástica. Rodolitos também ocorrem em manchas e alguns são fundidos entre 30-39 m de profundidade. Em profundidades maiores (40- 54 m) a abundância de rodolitos aumenta e ocorre associada a macroalgas carnosas, localmente alguns são maërl e outros são parcialmente enterrados por sedimentos de granulação fina. Duas fases de crescimento podem ser distinguidas em alguns rodolitos. Os núcleos apresentaram idades entre 1.600-1.850 anos, enquanto as camadas externas eram muito mais jovens (180-50 anos). As camadas de crescimento pareciam ter sido separadas por um longo período de enterramento no sedimento do fundo do mar.
... The data reported in this study expands upon the present knowledge concerning the mineralogy of coralline algae species worldwide, encompassing for the first time coralline algae species data from the Southwest Atlantic Ocean, where this group is the main frame-builders in coral reefs and the major inner component in rhodoliths 16,26 . Mineralogical analysis revealed that coralline algae species of the Brazilian Shelf were mainly formed of high-Mg calcite. ...
Coralline algae constitute one of the main groups of highly vulnerable calcified benthic organisms to ocean acidification. Although damaging effects of seawater acidification on the coralline algae skeleton have been widely demonstrated, the susceptibility to dissolution varies according to the Mg²⁺ in the calcite lattice. Even though the Southwest Atlantic Ocean exhibits the world’s largest rhodolith beds, which occupies 20,902 km², there is no information regarding the coralline algae species mineralogy in this area. Here, we provide mineralogical data of twenty-four coralline algae species, examine the similarity in taxonomic groups, spatial occurrence and the vulnerability of these algae to seawater acidification. Mineralogy revealed that coralline algae skeletons were mainly composed of high-Mg calcite (> 70%) with minor presence of aragonite (< 30%) and dolomite (< 3%). There were no similarities between the skeletal mineralogy of taxonomic groups and sampling regions. Remarkably, the mean Mg-substitution of encrusting coralline algae from the Brazilian Shelf was 46.3% higher than global average. Because of the higher mean Mg-substitution in calcite compared with worldwide coralline algae, these algae from Southwest Atlantic Ocean would be highly susceptible to dissolution caused by the expected near-future ocean acidification and will compromise CaCO3 net production across the Brazilian Shelf.
... The rhodoliths analyzed in this study started to grow between 1.9 and 1.8 ka cal BP, a long time after the Holocene flooding of the SEAL shelf [35]. The bathymetry of the investigated rhodolith beds lies within the large range of rhodolith beds in Brazil, which occur between 12 and 95 m depth [59][60][61][62][63][64][65]. Temperature, nutrients, sedimentation and water current velocity are considered the main environmental drivers of rhodolith development in the Brazilian ecoregions [65]. ...
... Shelf-incised valleys, canyons and riverine plumes led to the patchy distribution in large-scale rhodolith beds on the SEAL shelf ( Figure 1). On wider shelves, such as the Abrolhos shelf, which also has low sediment input, rhodolith beds are extensive and more continuous [63,66]. At a smaller scale, within individual rhodolith beds mapped on the SEAL shelf (Figure 1), the distribution of rhodoliths is patchy with varying rhodolith density. ...
... The concentric arrangement and high proportions of constructional void in rhodolith covers in sites of the south sector of the SEAL shelf are common in shallow-water rhodoliths in the south Espirito Santo and Rio Doce shelves [59,63]. High proportions of constructional voids were interpreted as reflecting low energy conditions [63], whereas concentric arrangements with little destruction by bioerosion indicate relatively short residence times of rhodoliths on the seafloor before burial. ...
Rhodolith beds are biogenic benthic habitats mainly formed by unattached, non-geniculate coralline algae, which can be inhabited by many associated species. The Brazilian continental shelf encompasses the largest continuous rhodolith bed in the world. This study was based on samples obtained from seven sites and videos taken by a Remotely Operated Vehicle (ROV) at four transects off the Sergipe-Alagoas Coast on the northeast Brazilian shelf. ROV operations and bottom trawl sampling revealed the occurrence of rhodolith beds between 25 and 54 m depths. At the shallower depths, fruticose (branching) rhodoliths (maërl) appear in troughs of ripples, and other non-branching rhodoliths occur associated with corals and sponge patches surrounded by bioclastic sand. Rhodoliths also occur in patches from 30 to 39 m depth; some are fused, forming larger, complex tridimensional structures. At deeper depths, from 40 to 54 m, the abundance of rhodoliths increases and occur associated with fleshy macroalgae on a smooth seafloor; some rhodoliths are fused into complex structures, locally some are fruticose (maërl), and others are partially buried by fine-grained sediment. The collected rhodoliths vary from fruticose in two sites to encrusting to lumpy, concentric and boxwork nodules in the rest; their size ranges from small (<1.5 cm) to large (~6 cm) and are mostly sub-spheroidal to spheroidal. A total of 16 red algal morpho-taxa were identified in the study sites. Two phases of growth can be distinguished in some rhodoliths by changes in color. The brownish inner cores yielded ages of 1600–1850 cal years before the present, whereas outer layers were much younger (180–50 years BP old). Growth layers appeared to have been separated by a long period of burial in the seafloor sediment. Other rhodoliths have ages of hundreds of years.
... Leonard et al., 1981;Henrich et al., 1992Henrich et al., , 1995; eastern Caribbean (see Foster, 2001; and references therein); the Mediterranean (Bosence, 1985;Fornos et al., 1992;Fornos & Ahr, 1997); the Brazilian shelf (Abrolhos continental shelf; e.g. Amado-Filho et al., 2012;Brasileiro et al., 2018); the Gulf of California (Halfar et al., 2000(Halfar et al., , 2004(Halfar et al., , 2006b; Japan (Matsuda, 1989;Tsuji, 1993;Matsuda & Iryu, 2011); Australia (e.g. James et al., 1994James et al., , 1999James & Bone, 2011;Fig. ...
The carbonate factories model, as defined at the beginning of the century, provides a subdivision of marine carbonate sediment production-systems based on the style of carbonate precipitation. The main factors controlling marine carbonate precipitation are light, water temperature, nutrients, salinity, substrate and carbonate saturation. Site-specific controls influencing the systems comprise ocean currents, upwelling and non-upwelling systems, ocean-atmosphere systems, atmospheric systems, shallow-water dynamics, and terrestrial sediment and water input.
Each factory has its own sediment-production window linking optimal sediment production with selected environmental controls. Sediment production in the tropical factory (T-factory) is light and temperature dependent and negatively impacted by nutrients. Sediment production and export depends on the size of the shallow-water areas within the photic zone. The cold-water-coral factory (CWC-factory) is nutrient dependent, but light independent. Sediment production relates to nutrient supply enabling the growth of the cold-water corals. The cool-water factory (C-factory) displays a strong link to nutrients and water temperature, with parts that are light-dependent, for example, sediment production in kelp dominated environments. The sediment mineralogy and sediment production area within the high-energy hydrodynamic zone govern sediment distribution with sediment behaviour comparable to siliciclastics. The Microbial/Mud-Mound factory (M-factory) is nutrient dependent and to some extent temperature and light independent. Sediment production and export is referred to here as slope shedding and links to the main sediment production on the upper slope. The planktic factory (P-factory) depends on variations in light, temperature and nutrients resulting in fluctuating pelagic fall-out.
Platform morphologies and slope profiles are also factory specific: T-factories show a rimmed flat-topped platform with adjacent exponential slopes or a carbonate ramp morphology; CWC-factories display mound morphologies with steep slopes; C-factories are associated with open shelf systems and Gaussian shaped slope profiles; while M-factories are characterized by individual steep-sided mounds or flat-topped platforms with deepened margins and a linear shaped slope profile. The P-factory provides biotic grains to all environments and at times, like for the Cretaceous, may dominate sedimentation patterns in the basin realm.
The sequence stratigraphic patterns substantially differ between factories. The T-factory being light-dependent is characterized by higher sediment production when the platform tops are flooded (highstand shedding). It displays decoupled sediment wedges with the partial infill of accommodation in the shallow-water realm and major sediment export towards the slopes and surrounding basins. The CWC-factory is marked by in situ production and deposition with limited sediment export forming single CWC spots or sediment accumulation ridges. The C-factory has a siliciclastic equivalent style of sediment distribution with lowstand-dominated, shelf edge wedges and a shaved-off shelf during sea-level highstands. Slope shedding marks the M-factory in which sediment production occurs within the upper slope realm of the flat-topped platforms both during highstands and lowstands in sea-level. This allows for fairly continuous sediment production exhibiting minor impact of sea-level changes, but with progradation, aggradation and retrogradation of the system being only limited by local environmental changes. P-factory sediment production may vary in accordance with variations in sea-level, providing time-lines and systems tracts boundaries in the pelagic realm.
In summary, each factory is branded by an individual set of features, for example, production window, sediment production and export, morphologies and slopes. It is this unique set of variables marking each factory that determines the factory-dependent response to small-scale and large-scale environmental changes through space and time as shown in the sequence stratigraphic development.
... In this inner shelf, maximum temperatures at the sea bottom may often exceed the upper limits for rhodolith bed occurrence along the SW Atlantic (~28.8 • C) (Carvalho et al., 2020). Additionally, fast currents and a complex sedimentary dynamic may favor rhodolith breakage and burial (Bosence, 1983;Brasileiro et al., 2018). Particularly, a high sediment resuspension seems to be a major factor structuring the shallow benthic communities in this area (Soares et al., 2017;Ximenes Neto et al., 2018a;2018b), a condition that is known to negatively affect the size and density of rhodololiths along the SW Atlantic Ocean and elsewhere (Perry, 2005). ...
Rhodolith growth and CaCO3 production remain poorly quantified along the SW Atlantic Ocean, and it is difficult to relate the available measurements with biomass estimates. Suboptimal conditions may clarify how harsh environments influence nodule growth and abundance, elucidating their relationship. Off the energetic South American equatorial coast a rhodolith bed (∼65 km²), formed mainly by Mesophyllum sp. and Lithophyllum sp., alters the regional sedimentary pattern and sustains a diverse biota. Its nodules present fast growth rates (2.8 mm∙year⁻¹), but small biomasses (18 nodules∙m⁻² covering 26 ± 3 % of the substrate), resulting in a CaCO3 production of 163.33 g∙m⁻²∙year⁻¹. Despite the small biomass, the bed seems stable, with living and dead nodules both on and inside the substrate. And the suboptimal environment apparently affects growth and abundance independently. Therefore, fast growth rates and relevant structural roles are not necessarily associated with dense rhodolith assemblages, and ecological assessments of rhodolith beds should consider the dynamics of both individual nodules and the whole population.
