Climatically induced changes in late Quaternary bathyal ostracod assemblages of the Camamu Basin, Brazil

Bathybic ostracods (i.e., bathyal and abyssal assemblages) are important indicators of temperature and productivity changes of Cenozoic marine ecosystems. The present work presents the first study on Quaternary ostracods of the Camamu Basin, off the state of Bahia, northeastern Brazilian continental margin. The analysis of 59 samples from the piston-core CMU 14 (14°24’S, 38°49’W; 965 m water depth), revealed rich and abundant assemblages. The 14C accelerator mass spectrometry (AMS) dating indicates that the studied interval covers the last 108 kyr, corresponding to the oxygen stable isotope stages (MIS) 5 to 1. Comparison with data from previous publications allowed discernment of three groups of ostracod species in CMU 14: Pandemic Group of species registered in more than one oceanic basin; Atlantic/Mediterranean Group of species restricted to the Atlantic Ocean and Mediterranean; and Brazilian Group of species restricted to the Brazilian continental margin). Four new species are herein proposed: Cytherella pindoramensis sp. nov., Ambocythere amadoi sp. nov., Pseudobosquetina pucketti sp. nov., and Bythoceratina bonaterrae sp. nov. Ostracod occurrences reveal the influence of glacial/interglacial cycles on assemblages composition. Interglacial stages 5 and 1 in the Camamu Basin are characterized by the association Bythocypris affinis–Cytherella pindoramensis sp. nov.– Cytheropteron perlaria–Bradleya dictyon; glacial stages (i.e., 2 to 4) register decreased diversity, possibly due to lower oceanic productivity

Paleoecological characterization of ostracods in beachrocks from the Northern sector of the Rio Grande do Sul Coastal Plain, Brazil

A micropaleontological analysis on 15 beachrock samples from the Northern sector of Rio Grande do Sul Coastal Plain (RSCP), southern Brazil, revealed a relatively diverse and well-preserved ostracod assemblage composed of 16 species, including Cyprideis multidentata Hartmann, Callistocythere nucleoperiscum Whatley et al., Cytheretta punctata Sanguinetti, Caudites ohmerti Coimbra & Ornellas, and Argenticytheretta levipunctata Sanguinetti et al. Eleven ostracod species are left in open nomenclature or tentatively identified. Besides ostracods, some foraminifers, echinoderm spines, and fish remains (teeth) were also recovered; however, the scarcity of specimens or poor preservation precluded identification at species level. Based on the Ostracoda taxonomic composition it is proposed that the beachrocks characterize environmentally condensed assemblages. This preliminary study reveals the importance and potentiality of micropaleontology for understanding the processes involved in the formation of beachrocks.O estudo micropaleontológico de 15 amostras de arenitos de praia provenientes do setor norte da Planície Costeira do Rio Grande do Sul (PCRS), sul do Brasil, revelou uma assembleia relativamente diversa e bem preservada de ostracodes, composta por 16 espécies, incluindo Cyprideis multidentata Hartmann, Callistocythere nucleoperiscum Whatley et al., Cytheretta punctata Sanguinetti, Caudites ohmerti Coimbra & Ornellas e Argenticytheretta levipunctata Sanguinetti et al. Onze espécies são registradas em nomenclatura aberta ou tentativamente identificadas. Além dos ostracodes, foraminíferos, espinhos de equinodermos e vestígios de peixes (dentes) foram também recuperados, contudo, a baixa abundância e/ou preservação impediram a identificação em nível de espécie. A composição taxonômica dos ostracodes indica que estas rochas registram assembleias ecologicamente condensadas. Este estudo preliminar revela a importância e potencialidades da micropaleontologia para a caracterização dos processos envolvidos na formação de arenitos de praia

Paleobiología de la conservación : sumando la ecología del pasado para comprender el presente

El cambio climático global está modificando de modo acelerado las características de los hábitats, y eso tiene un impacto sobre las comunidades que ya se encuentran alteradas por impactos antrópicos anteriores. ¿Cómo eran las comunidades no impactadas? Las únicas evidencias que tenemos están alojadas en los restos de los organismos, hallados sobre la superficie o en los primeros centímetros debajo del sedimento, en registros históricos y sitios arqueológicos. ¿Cómo serán esas comunidades en la nueva configuración climática? La paleontología tiene un amplio registro de las respuestas de las comunidades a los cambios ambientales, que pueden utilizarse como modelos para el diseño de planes de conservación de la biodiversidad. ¿Estamos en medio de una extinción en masa? La paleontología puede aportar significativamente a contestar esta pregunta, a partir del conocimiento de los fenómenos relacionados con las cinco extinciones masivas, y de otras de menor escala, registradas en los sedimentos y rocas pretéritos. La paleobiología de la conservación tiene el objetivo de contribuir a los proyectos de conservación con la información proveniente del registro de la vida en el pasado

Bioerosion on late Quaternary Planktonic Foraminifera related to paleoproductivity in the western South Atlantic

Planktonic Foraminifera are widely used in paleoceanographic reconstructions, although studies of their trophic interactions are still rare, especially those focusing on predation. Drilling holes are the most frequent traces of bioerosion in foraminifer tests, but environmental factors that control bioerosion are not yet understood. To determine if paleoceanographic variables are associated with bioerosion rates in late Quaternary planktonic foraminifers of the western South Atlantic, geochemical and assemblage analyses were made on a 46 kyr record from a piston core. An age model was constructed based on 10 AMS 14C dates. To reconstruct the paleoproductivity, δ13C, benthic/planktonic foraminifer and the relative abundances of Globigerina bulloides and Globigerinoides ruber (high and low productivity, respectively) were used. Bioeroded tests were counted and found in 21 of the 25 identified species, with frequencies ranging from 8.84% to 16.7%. Bioerosion was different in two groups identified by cluster analysis, with a higher intensity during glacial times, showing a strong correlation with paleoceanographic fluctuations. Paleoproductivity estimates and bioerosion rates show a significant correlation, suggesting that bioerosion is more frequent in eutrophic environments and more inhibited in oligotrophic conditions. However, even with a strong correlation between bioerosion and productivity, there is also a negative correlation with sea surface temperature in the study area. Since conditions that promote higher productivity are accompanied by a decrease in surface temperature, the precise distinction between the influence of both variables is hampered. Further research will allow us to explore the potential of planktonic foraminiferal bioerosion as a tool in paleoceanographic studies

The tricky task of fisher-gardener research in conservation paleobiology

The study of sambaquis (ancient shell mounds) in conservation paleobiology is a complicated subject, especially when comparing body sizes of current and past mollusk valves to observe possible changes. There is a lack of information regarding how ancient fisher-gardeners collected these shellfish. Another obstacle is finding the hypothesis tests and data that can be used to compare current and past body sizes. To this end, we use the t-test (tt), Mann-Whitney (mw), and Bootstrap (bt) analyses to determine data scenarios for yellow clam (Amarilladesma mactroides) shells from two sambaquis units, and from two transects along the beaches of Rio Grande do Sul in southern Brazil. The study finds that the average body size of an Amarilladesma mactroides adult specimen is greater in sambaquis than the current valves across all tests (tt, p = 0.0005; mw, p = 0.006; bt, p = 0.04), even after reducing the sample number. However, when the comparison is only between valves that are larger than average, this does not hold true for two of the statistics (tt, p = 0.24; mw, p = 0.04; bt, p = 0.25). By refining the comparison for recent valves from different levels in the swash zone (upper, middle, and lower levels) with the past valves, we find that body sizes only differ at the middle level of the swash zone (tt, p = 0.004; mw, p = 0.004; bt, p = 0.005), where smaller adults, recruits, and juveniles live. This result could indicate that fisher-gardeners collected large organisms at distinct levels depending on the season (i.e., adults are collected in the upper level during summer and in the lower level during winter)