ALBERT

Description: ABSTRACT Planktonic foraminiferal species identification is central to many paleoceanographic studies, from selecting species for geochemical research to elucidating the biotic dynamics of microfossil communities relevant to physical oceanographic processes and interconnected phenomena such as climate change. However, few resources exist to train students in the difficult task of discerning amongst closely related species, resulting in diverging taxonomic schools that differ in species concepts and boundaries. This problem is exacerbated by the limited number of taxonomic experts. Here, we document our initial progress towards removing these confounding and/or rate‐limiting factors by generating the first extensive image library of modern planktonic foraminifera, providing digital taxonomic training tools and resources, and automating species‐level taxonomic identification of planktonic foraminifera via machine learning using convolution neural networks. Experts identified 34,640 images of modern (extant) planktonic foraminifera to the species level. These images are served as species exemplars through the online portal Endless Forams (endlessforams.org) and a taxonomic training portal hosted on the citizen science platform Zooniverse (zooniverse.org/projects/ahsiang/endless‐forams/). A supervised machine learning classifier was then trained with ~27,000 images of these identified planktonic foraminifera. The best‐performing model provided the correct species name for an image in the validation set 87.4% of the time, and included the correct name in its top three guesses 97.7% of the time. Together, these resources provide a rigorous set of training tools in modern planktonic foraminiferal taxonomy and a means of rapidly generating assemblage data via machine learning in future studies for applications such as paleotemperature reconstruction and salinity indicator counting.

Description: 〈span〉〈div〉Abstract〈/div〉Habitat patterns of subtropical and tropical planktic foraminifers in the Caribbean Sea were obtained from plankton samples collected in spring 2009 and 2013. The spatial distribution in surface waters (3.5 m water depth) and depth habitat patterns (surface to 400 m) of 33 species were compared with prevailing water-mass conditions (temperature, salinity, and chlorophyll-〈span〉a〈/span〉 concentration) and planktic foraminiferal test assemblages in surface sediments. Distribution patterns indicate a significant relationship with seawater temperature and trophic conditions. A reduction in standing stocks was observed close to the Orinoco River plume and in the Gulf of Paria, associated with high turbidity and concomitant low surface-water salinity. In contrast, a transient mesoscale patch of high chlorophyll concentration in the eastern Caribbean Sea was associated with higher standing stocks in near surface waters, including high abundances of 〈span〉Globigerinita glutinata〈/span〉 and 〈span〉Neogloboquadrina dutertrei〈/span〉. 〈span〉Globorotalia truncatulinoides〈/span〉 mainly lives close to the seasonal pycnocline and can be linked to winter conditions indicated by lower sea-surface temperatures (SSTs) of ∼20°C. 〈span〉Globigerinoides sacculifer〈/span〉 and 〈span〉Globoturborotalita rubescens〈/span〉 were associated with oligotrophic conditions in the pelagic Caribbean Sea during early spring and showed a synodic lunar reproduction cycle. The live assemblages in the water column from 2009 and 2013 were similar to those reported in earlier studies from the 1960s and 1990s and to assemblages of tests in the surface sediments. Minor differences in faunal proportions were attributed to seasonal variability and environmental differences at the local scale. An exception was the low relative abundance of 〈span〉Globigerinoides ruber〈/span〉 in the Caribbean Sea in 2009 compared to surface sediment samples and plankton net samples collected in the 1960s and 1990s. Decreasing abundance of 〈span〉Gs. ruber〈/span〉 white in the Caribbean Sea may be associated with increasing SSTs over past decades and changes in nutrient flux and primary production.〈/span〉

Description: Abstract Homogeneity, mass fractions of about forty trace elements and Sr isotope composition of Ca carbonate reference materials (RMs) between original and nano‐powdered pellets are compared. Our results using nanosecond and femtosecond LA‐(MC)‐ICP‐MS show that the nano‐pellets of the RMs MACS‐3NP, JCp‐1NP and JCt‐1NP are about a factor of 2–3 more homogeneous than the original samples MACS‐3, JCp‐1 and JCt‐1, and are therefore much more suitable for microanalytical purposes. With the exception of Si, the mass fractions of the synthetic RM MACS‐3 agree with its fine‐grained analogue MACS‐3NP. Very small, but significant, differences between original and nano‐pellets are observed in the RMs JCp‐1 and JCt‐1 for some trace elements with very low contents, indicating the need for re‐certification. Strontium mass fractions in the analysed RMs are high (1500–7000 mg kg‐1) and their isotope compositions determined by LA‐MC‐ICP‐MS in the original and the nano‐pellets agree within uncertainty limits. This article is protected by copyright. All rights reserved.

Description: Habitat patterns of subtropical and tropical planktic foraminifers in the Caribbean Sea were obtained from plankton samples collected in spring 2009 and 2013. The spatial distribution in surface waters (3.5 m water depth) and depth habitat patterns (surface to 400 m) of 33 species were compared with prevailing water-mass conditions (temperature, salinity, and chlorophyll-a concentration) and planktic foraminiferal test assemblages in surface sediments. Distribution patterns indicate a significant relationship with seawater temperature and trophic conditions. A reduction in standing stocks was observed close to the Orinoco River plume and in the Gulf of Paria, associated with high turbidity and concomitant low surface-water salinity. In contrast, a transient mesoscale patch of high chlorophyll concentration in the eastern Caribbean Sea was associated with higher standing stocks in near surface waters, including high abundances of Globigerinita glutinata and Neogloboquadrina dutertrei. Globorotalia truncatulinoides mainly lives close to the seasonal pycnocline and can be linked to winter conditions indicated by lower sea-surface temperatures (SSTs) of ∼20°C. Globigerinoides sacculifer and Globoturborotalita rubescens were associated with oligotrophic conditions in the pelagic Caribbean Sea during early spring and showed a synodic lunar reproduction cycle. The live assemblages in the water column from 2009 and 2013 were similar to those reported in earlier studies from the 1960s and 1990s and to assemblages of tests in the surface sediments. Minor differences in faunal proportions were attributed to seasonal variability and environmental differences at the local scale. An exception was the low relative abundance of Globigerinoides ruber in the Caribbean Sea in 2009 compared to surface sediment samples and plankton net samples collected in the 1960s and 1990s. Decreasing abundance of Gs. ruber white in the Caribbean Sea may be associated with increasing SSTs over past decades and changes in nutrient flux and primary production.

Description: Determination of Mg/Ca in foraminifer shells as a proxy of seawater temperature is of particular interest in paleoclimate reconstruction. Here we show that femtosecond–200 nm–laser ablation–inductively coupled plasma–mass spectrometry is a suitable technique to precisely and accurately determine Mg/Ca in the micrometer-sized calcareous chambers of foraminifers. At low fluence (0.3–0.6 J/cm 2 ) the double-charged 44 Ca ++ and the single-charged 25 Mg + ions are measured nearly simultaneously. Integrated single-shot measurements using a pulse repetition rate of 1 Hz enable precise analyses at a depth resolution of about 50–100 nm/pulse corresponding to an ablated material of 0.3–0.6 ng calcite/pulse for a spot size of 55 μm. High-resolution analyses can be performed until a depth of 10–20 μm and thus particularly suitable for thin-shelled foraminifers. Reproducibility (relative standard deviation) is about 5% as approved by homogeneous reference materials. Calibration is performed with the microanalytical synthetic reference material MACS-3. Magnesium and Ca data of different carbonate and silicate reference materials agree within uncertainties with reference values. The procedure has been successfully applied for detailed analyses of single chambers and shell-depth profiles of live individuals and empty planktic and benthic foraminifer tests from different ocean basins.