RESUMEN
The reef system off the Amazon River mouth extends from Amapá state to Maranhão state along the Brazilian Equatorial Margin, encompassing more than 10,000 km2 of rhodolith beds and high-relief hard structures on the outer shelf and upper slope. This unique hard bottom mosaic is remarkable for being influenced by the turbid and hyposaline plume from the world's largest river, and also for representing a connectivity corridor between the Caribbean and Brazil. Bryozoans were recently recognized as major reef builders in the Southwestern Atlantic, but their diversity off the Amazon River mouth remained unknown. Here, we report on recent collections obtained from 23 to 120 m depth in Northern Brazil. Sixty-five bryozoan taxa were characterized using scanning electron microscopy, including 57, five and three taxa of Cheilostomatida, Cyclostomatida and Ctenostomatida, respectively. Cribrilaria smitti and three genera (Cranosina, Glabrilaria and Thornelya) are new records for Brazil, and 13 new species are herein described: Antropora cruzeiro n. sp., Cranosina gilbertoi n. sp., Cribrilaria lateralis n. sp., Crisia brasiliensis n. sp., Glabrilaria antoniettae n. sp., Micropora amapaensis n. sp., Parasmittina amazonensis n. sp., Plesiocleidochasma arcuatum n. sp., Poricella bifurcata n. sp., Pourtalesella duoavicularia n. sp., Stephanollona domuspusilla n. sp., Therenia dianae n. sp., and Thornelya atlanticoensis n. sp. Our results highlight the biodiversity significance of the Amazon reefs and the need for more comprehensive sampling to clarify the role of bryozoans in modern turbid-zone reefs and rhodolith beds.
Asunto(s)
Briozoos , Animales , Biodiversidad , Briozoos/clasificación , Briozoos/fisiología , RíosRESUMEN
Bryozoans are a key group of sessile invertebrates in some reef frameworks but are typically neglected in environmental monitoring programs. Abrolhos Bank (Brazil) is the largest reef complex in the South Atlantic Ocean, encompassing several reef landscapes over an area of 46,000 km2. A transition takes place across the shelf from mangroves to soft sediments, coastal shallow reefs to a volcanic archipelago - surrounded by fringing reefs - and unique mushroom-shaped biogenic structures, with mesophotic pinnacle reefs, rhodolith beds, sink-holes and shelf break deep environments. The taxonomic composition of the bryozoan fauna was studied in 11 core samples taken from shallow to mesophotic mid-shelf reefs (4-25 m deep) on Abrolhos Bank by divers using a submersible drill. Of the 20 bryozoan species sampled, 17 are new records for Abrolhos Bank and seven species are new to science: Crassimarginatella winstonae n. sp., Parasmittina distincta n. sp., Parasmittina abrolhosensis n. sp., Hemismittoidea asymmetrica n. sp., Stylopoma variabilis n. sp., Stylopoma hastata n. sp., and Plesiocleidochasma acuminata n. sp. (described by Ramalho, Taylor Moraes). The most conspicuous species is Celleporaria atlantica. These results increase to 48 the total number of bryozoan species known in this region and reinforce the importance of this group as one of the main components apart from crustose coralline algae and corals of the reef framework-building community of Abrolhos Bank.
Asunto(s)
Arrecifes de Coral , Ecología , Animales , Antozoos , Océano Atlántico , BrasilRESUMEN
In major modern reef regions, either in the Indo-Pacific or the Caribbean, scleractinian corals are described as the main reef framework builders, often associated with crustose coralline algae. We used underwater cores to investigate Late Holocene reef growth and characterise the main framework builders in the Abrolhos Shelf, the largest and richest modern tropical reef complex in the South Western Atlantic, a scientifically underexplored reef province. Rather than a typical coralgal reef, our results show a complex framework building system dominated by bryozoans. Bryozoans were major components in all cores and age intervals (2,000 yrs BP), accounting for up to 44% of the reef framework, while crustose coralline algae and coral accounted for less than 28 and 23%, respectively. Reef accretion rates varied from 2.7 to 0.9 mm yr-1, which are similar to typical coralgal reefs. Bryozoan functional groups encompassed 20 taxa and Celleporaria atlantica (Busk, 1884) dominated the framework at all cores. While the prevalent mesotrophic conditions may have driven suspension-feeders' dominance over photoautotrophs and mixotrophs, we propose that a combination of historical factors with the low storm-disturbance regime of the tropical South Atlantic also contributed to the region's low diversity, and underlies the unique mushroom shape of the Abrolhos pinnacles.
Asunto(s)
Océano Atlántico , Briozoos , Arrecifes de Coral , AnimalesRESUMEN
The Pirabas Formation in Brazil has been studied for many years and a great diversity of animal groups (in particular fishes, molluscs and echinoderms) have been described from there, whereas the Bryozoa have scarcely been mentioned. New samples, collected specifically to focus on bryozoans, have shown that the diversity in this formation is higher than previously thought. Here we describe two new species belonging to the cheilostomate genus Hippopleurifera--H. barbosae sp. nov. and H. confusa sp. nov. Both species were collected at Atalaia Beach, northeastern Pará state, which boasts some of the best marine Cenozoic fossil outcrops in Brazil. After accounting for all described species, plus the two new species and four generic reassignments (new combinations) described herein, some 29 Hippopleurifera species are now known. Most of these are fossils from Europe or the USA, but a handful are known from the Recent Mediterranean, Caribbean and Indo-West Pacific.
Asunto(s)
Briozoos/anatomía & histología , Briozoos/clasificación , Fósiles/anatomía & histología , Animales , Brasil , Briozoos/ultraestructura , Microscopía Electrónica de Rastreo , Especificidad de la EspecieRESUMEN
The continental shelf of Rio Grande do Sul (RS) is predominantly composed of unconsolidated sediments with a few hard substrates represented principally by beachrock. In this area there are elongate deposits of shell gravel material which are interpreted as indicators of the palaeo-shorelines. These Pleistocene deposits are overlapped by Holocene sediments (Recent), but are exposed during erosive events caused by extra-tropical cyclones, which provide the mixture of both sediments mainly during autumn and winter. The few studies on bryozoans made in this area previously recorded seven species, one fossil and the other six from Recent fluvial and marine environments. The aim of the present study was to describe the eight most abundant bryozoan species that occur in the inner RS shelf. Of these, four are new records for RS State (Arachnopusia aff. pusae, Hippomonavella brasiliensis, Turbicellepora pourtalesi, and Lifuella gorgonensis), and the other four are new to science (Chaperia taylori, Micropora nodimagna, Cellaria riograndensis, and Exochella moyani).
Asunto(s)
Briozoos/clasificación , Distribución Animal , Estructuras Animales/anatomía & histología , Estructuras Animales/crecimiento & desarrollo , Animales , Tamaño Corporal , Brasil , Briozoos/anatomía & histología , Briozoos/crecimiento & desarrollo , Tamaño de los ÓrganosRESUMEN
Pirabasoporella gen. nov. is introduced for three new bryozoan species from the Early Miocene of the tropical western Atlantic. The genus is placed in the family Jaculinidae Zabala, a peculiar group of cheilostome bryozoans characterised by reticulate colonies formed by uni- or biserial branches that are connected by kenozooidal struts. This colonial morphology superficially resembles colonies of the Paleozoic order Fenestrata (Stenolaemata) and some Recent Cyclostomata. As jaculinid colonies are anchored to soft sediments via rhizoids, however, they differ in life habit from Paleozoic and modern fenestrate colonies, which are firmly attached to stable substrata by an encrusting base. The three new species are Pirabasoporella atalaiaensis n. sp. from the Brazilian Pirabas Formation, Pirabasoporella baitoae n. sp. from the Baitoa Formation (Dominican Republic), and Pirabasoporella chipolae n. sp. from the Floridan Chipola Formation. Their presence in the Early Miocene western Atlantic represents the earliest record of Jaculinidae, and suggests that the origin of the family, the only living species of which are known from the eastern Atlantic and Mediterranean Sea, extends well into the Paleogene. The Jaculinidae is here transferred from the lepraliomorph superfamily Schizoporelloidea Jullien to the umbonulomorph Lepralielloidea Vigneaux owing to the partly umbonuloid frontal shield and non-schizoporelloid ovicell.