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Abstract. The rapid response of foraminiferal assemblages to changing climate makes their shells an invaluable geological record of the past. However, the time frame over which foraminifera respond to climatic signals and the specific drivers influencing assemblage composition and abundance remain obscure. We focus on the impact of ongoing, anthropogenic climate change on planktic foraminifera in the California Current ecosystem, which would appear as a nearly instantaneous event in the sediment record. The Santa Barbara Basin sediment trap, located off the coast of California, USA since 1993, provides a record of more than 30 years of particulate and foraminiferal flux in the basin. The sediment trap captures the superposition of the annual cycle of seasonal upwelling, Pacific multiannual El Niño–Southern Oscillation-driven temperature changes, and anthropogenically forced climate change. We present data on planktic foraminiferal flux collected between 2014–2021, at two-week intervals (164 samples, 60 006 individuals) and compare results to previously published data from 1993–1998. Consistent with previous studies, the most abundant species from 2014–2021 were Globigerina bulloides, Neogloboquadrina incompta, and Turborotalita quinqueloba, with peak fluxes occurring in the spring and summer. Lower fluxes and an increase in the abundance of N. incompta and subtropical species characterize the winter season. We find a 37.9 % decrease in total foraminiferal flux relative to the 1990s, primarily driven by a decrease in G. bulloides abundance. This decrease is accompanied by a 21.0 % overall reduction in calcium carbonate flux. We also find a decrease in the relative abundance of subtropical species (Globigerinoides ruber, Orbulina universa, and Neogloboquadrina dutertrei) and their fluxes compared to the 1990s, opposite expectations if assemblages and fluxes were to follow anthropogenic warming signals. We hypothesize that the observed decrease in subtropical species abundance and flux is likely related to an increase in acidification and in the timing and magnitude of upwelling along the California coast. The extremely rapid responses of foraminifera to ongoing changes in carbonate chemistry and temperature suggest that climate change is already having a meaningful impact on coastal carbon cycling. The observed decrease in particulate inorganic carbon (PIC) flux relative to particulate organic carbon (POC) flux may facilitate increased oceanic uptake of atmospheric CO2. 

Abstract Understanding and quantifying the microbial contribution to particulate organic matter (POM) flux and carbon cycling in the ocean relies largely on the collection of sinking POM. A critical aspect of evaluating microbial communities on sediment trap‐collected POM is their preservation until recovery and sample processing. While RNAlaterhas emerged as a recent preservative in sediment trap studies, no comparisons have been made between RNAlaterand the more established preservative, formalin, to determine their effectiveness in capturing POM‐attached microbial communities. Our work evaluates these preservatives through laboratory testing and sediment trap deployments (lasting days to months). Formalin‐fixed POM required decrosslinking (undoing bonds between DNA and proteins) to extract DNA. When decrosslinking was included, no community differences were observed from subsequent DNA extraction or amplification when preserved in the lab. However, when preservatives were deployed inside sediment traps, significant differences were observed among unpreserved, RNAlater‐preserved, and formalin‐preserved POM. In these samples, some copiotrophs, such as Gammaproteobacteria, Verrucomicrobiae, and Flavobacteria, demonstrated greater relative abundances in RNAlater, and the overall magnitude of these differences was greater for RNAlater‐preserved vs. formalin‐fixed POM, indicating differing abilities of each preservative to halt microbial activity, contributing to the overrepresentation of some taxa. Together, these results suggest that formalin preservation is the best option for use in sediment traps, especially for long‐term deployments (> 5 d), common for moored sediment trap timeseries studies. A skewed view of microbial community structure on POM has implications for our understanding of the taxa and metabolisms contributing to carbon turnover in the ocean. 

There have been many efforts to broaden participation and diversity in the geosciences with varying degrees of success. The goal of the National Science Foundation-funded GeoScholar Program in the School of the Earth, Ocean & Environment (SEOE) at the University of South Carolina was to increase geoscience exposure and the number of geoscience undergraduate majors (environmental, geological, and marine sciences) from low-income, minority, and first-generation college backgrounds. 

ABSTRACT The trace element composition of planktic foraminifera shells is influenced by both environmental and biological factors (‘vital effects’). As trace elements in individual foraminifera shells are increasingly used as paleoceanographic tools, understanding how trace element ratios vary between individuals, among species, and in response to high frequency environmental variability is of critical importance. Here, we present a three-year plankton tow record (2010–2012) of individual shell trace element (Mg, Sr, Ba, and Mn) to Ca ratios in the planktic species Globigerina ruber (pink), Orbulina universa, and Globorotalia menardii collected throughout the upper 100 m of Cariaco Basin. Plankton tows were paired with in situ measurements of water column chemistry and hydrography. The Mg/Ca ratio reflects different calcification temperatures in all three species when calculated using species-specific temperature relationships from single-species averages of Mg/Ca. However, individual shell Mg/Ca often results in unrealistic temperate estimates. The Sr/Ca ratios are relatively constant among the four species. Ratios of Mn/Ca and Ba/Ca are highest in G. menardii and are not reflective of elemental concentrations in open waters. The Mn/Ca ratio is elevated in all species during upwelling conditions, and a similar trend is demonstrated in Neogloboquadrina incompta shells from the California margin collected during upwelling periods. Together this suggests that elevated shell Mn/Ca may act as a tracer for upwelling of deeper water masses. Our results emphasize the large degree of trace element variability present among and within species living within a limited depth habitat and the roles of biology, calcification environment, and physical mixing in mediating how trace element geochemistry reflects environmental variability in the surface ocean. 

Measurements of particulate organic carbon (POC) are critical for understanding the ocean carbon cycle, including biogenic particle formation and removal processes, and for constraining models of carbon cycling at local, regional, and global scales. Despite the importance and ubiquity of POC measurements, discrepancies in methods across platforms and users, necessary to accommodate a multitude of needs and logistical constraints, commonly result in disparate results. Considerations of filter type and pore size, sample volume, collection method, and contamination sources underscore the potential for dissimilar measurements of the same variable assessed using similar and different approaches. During the NASA EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) 2018 field campaign in the North Pacific Ocean, multiple methodologies and sampling approaches for determining POC were applied, including surface inline flow-through systems and depth profiles using Niskin bottles, in situ pumps, and Marine Snow Catchers. A comparison of results from each approach and platform often resulted in significant differences. Supporting measurements, however, provided the means to normalize results across datasets. Using knowledge of contrasting protocols and synchronous or near-synchronous measurements of associated environmental variables, we were able to reconcile dataset differences to account for undersampling of some particle types and sizes, possible sample contamination and blank corrections. These efforts resulted in measurement agreement between initially contrasting datasets and insights on long-acknowledged but rarely resolved discrepancies among contrasting methods for assessing POC concentrations in the ocean.