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Many different techniques are used to extract microplastics (MPs) from sediment samples of variable composition and grain size. The lack of uniform methodology makes it challenging to compare results across studies and to select methods appropriate to local sedimentary conditions. This study (a) evaluates the separation efficiency, yield, and contamination (blank) of settling compared centrifugation density separation, and (b) examines the distribution of MP across successive separation phases (interstitial water, organic matter, sediment). Two different density-separation dependent extraction methods were tested with tropical marine sediments from the US Virgin Islands with variable grain size and composition: (1) suspension within a settling column, and (2): centrifugation. The samples were processed under a laminar flow hood using published best practices to minimize contamination. The two separation techniques produced similar MP yields (85-100%), which were calculated by tracing polyethylene microspheres. However, processing in the settling column sometimes produced incomplete settling of fine organic matter and took a significantly longer time (week vs. minutes) than did separation via centrifugation. Analytical blanks (contamination) were also slightly greater using a settling column (avg: 5.3±1.1) vs the centrifuge (avg: 3.6±0.9). However, the most important reason why the centrifugation is preferable is that it allows for the complete removal of separatory solutions via compaction of the sediment. This allows phased separation of MPs through sequential interstitial water removal, hydrogen peroxide treatment and removal (to target organic matter bound MP), and density separation phases. Our experiments showed that a significant portion of the total MP in the samples were potentially located in the interstitial water phase (16±12%) and the following hydrogen peroxide phase (25±20%). In the literature, intermediate treatment solutions are often discarded, resulting in an underestimation of total MP in the sediments. In summary, we found that the most effective method of MP extraction from organic rich or fine-grained sediments is a phased centrifugation process which includes counting MP from all phases. 

The GEOPATHS program is an inter-institutional oceanographic research program, which aims to inspire and train diverse students to pursue careers in the geosciences through experiential research, and to assess the effectiveness of this approach. This program connects students, researchers and faculty from a land-locked HSI (CSUB) and a coastal liberal arts university (USD) with researchers from the Scripps Institution of Oceanography to engage in shipboard research, mentored research internships, geoscience career outreach, curriculum development, a teacher training workshop, and the generation of curated oceanographic samples and shipboard videos available for future education and research. Between 2018-22, over 170 undergraduate students (including undecided majors and pre-service teachers) and secondary teachers engaged as shipboard scientists on one of three 4-day and/or seven 12-hour research voyages aboard UNOLS research vessels. Most of the students had never been at sea and some had never seen the ocean, so living and working at sea was an empowering, transformative, life-changing experience. The intense, immersive 24-hour working environment aboard ship provided unique opportunities for professional socialization as well as exciting, hands-on training using sophisticated state-of-the-art analytical equipment. Additional students engaged in the voyages through new curricula that included voyage samples, data, and videos of student impressions and scientific operations. New courses in oceanography were added to CSUB’s curriculum and voyage data/activities were incorporated into existing courses. Over 20 students pursued mentored research internships and most presented at professional conferences. Geoscience career outreach activities connected students with local geoscience professionals. Several students have pursued graduate studies related to oceanography. Student responses to assessment surveys and a dissertation that focused on the impacts of the GEOPATHS research experiences indicated that regardless of their major, student participants in the program were positively impacted by the hands-on experiences at sea, highlighting the effectiveness of oceanographic and paleontologic research in engaging students in geoscience. 

ABSTRACT: Although plastics are becoming more prevalent, even in the far reaches of the deep sea, the influence of these novel attachment surfaces has yet to be systematically studied regarding the ecology and distribution patterns of attached fauna. Herein, we report the abundances and vertical distribution patterns of epibenthic foraminifera living on plastics after 2 yr on the seafloor at 4000 m water depth and compare these populations with those of nearby naturally occurring substrates and their surrounding sediments. After 2 yr, 239 foraminifera were found attached to 4 Seafloor Epibenthic Attachment Cubes (SEA3s). Dominant taxa included Cibicidoides wuellerstorfi var. lobatulus, Pyrgoella sp., and arborescent foraminifera. Variations in colonization height and abundance between plastic types were observed, but no clear drivers of these patterns can be ascertained from this study. Foraminiferal populations from elevated substrates and the nearby sediment cores showed no significant overlap in populations, suggesting that foraminifera colonizing SEA3s did not originate from surrounding sediments and likely recruited from other elevated substrates common in the area (e.g. glass sponges). This study demonstrates that plastics serve as hard substrates which deep-sea foraminifera inhabit and that plastics may persist for extended periods of time, potentially altering ecosystem compositions in environments dominated by soft sediments. There is a significant difference between colonizing epifaunal and sediment populations, which raises interesting questions about colonization and distribution processes in deep bathyal and abyssal environments. Epi benthic foraminifera at - tached to elevated substrates may be underrepresented in the sedimentary record through preservation and sampling biases. 

Foraminifera are single celled organisms that have tests that are composed of calcium carbonate or detrital materials. The assemblages of foraminifera have been influenced by their immediate environment which depict the influence and results of man’s activities and other natural processes that occur in the environment. These environmental changes include salinity, pH, hydrocarbon pollution and organic matter. With these factors, paleoenvironmental interpretations are made by identifying the different patterns in the foraminifera communities. Variations in oxygen concentrations at the sediment-water interface have a significant impact on benthic foraminiferal assemblages and morphologic properties. This is seen in the vertical distribution of foraminifera in response to factors such as food, pore water, and oxygen. This study documents foraminiferal ecology and abundances across an oxygen transect off the coast of San Diego. Available oxygen ranges from >1.0ml/l are considered oxic; O2 values from 0.1 - 1.0ml/l will be considered dysoxic and O2 values <0.10ml/l will be considered anoxic. Previous work in this region has suggested that sediment grain size, rather than oxygen availability, may have as much of an impact on foraminiferal assemblages. These observations were made based on the fact that Cibicidoides wuellerstorfi, an epibenthic foraminifera preferring elevated substrates in well-oxygenated environments, were found in greater abundances at areas with coarser grained materials despite low available oxygen. C. wuellerstorfi has also been found to have I/Ca and test porosity (size and abundance of pores on the surface of the test) which correlate to the available oxygen in bottom waters at the time of test formation. Not only will this study document foraminiferal assemblages and abundances across an oxygen transect, but C. wuellerstorfi from key oxygen environments will be examined under SEM and used in porosity and I/Ca analyses which will contribute to the development of a quantitative oxygen proxy. The development of this quantitative oxygen proxy is essential because despite oxygen being one of the primary variables influencing major geochemical and faunal responses within the world’s ocean, no clear proxy currently exists in paleoceanographic reconstructions. 

Upwelling systems on eastern boundaries of subtropical ocean basins are some of the most climatically dynamic regions of the oceans. Anthropogenic climate change has implications for these marine ecosystems, such as driving marine deoxygenation, driving ecosystem zonation, and driving the expansion of oxygen minimum zones (OMZ). There have been multiple studies evaluating drivers of marine oxygenation changes, yet there is still a need to understand surface processes and source waters influence on bottom-water oxygenation. The California continental margin is a well-studied upwelling system, where source water mixing of oxygen-rich subarctic waters to oxygen-poor subtropical waters is strongly influenced by the California Current, leading to one of the most primary production areas in the Pacific. Here we present data of redox sensitive trace metals to evaluate changes in the bottom water ventilation off the coast of Southern California due to climatic changes. Samples from several sediment cores were recovered via the RV Roger Revelle Expedition RV2206 during the summer of 2022. The sediment samples were digested applying a multi-acid digestion technique and analyzing together with pore water samples via inductively coupled plasma mass spectrometry. Interestingly, we observe a strong flux of specific heavy metals from the sediments into the overlying water column, likely impacting the benthic community and altering the primary metal-proxy signal at these sites with potential implications for the reconstruction of current ventilation through these geochemical and microfossil tracers. Overall, our preliminary results indicate fluctuations in the OMZ seaward expansion with implications for the oxygenation condition of the deeper water. 

The concentration of dissolved oxygen (DO) has decreased by about 2% over the past 50 years due to rising global temperatures and models predict further declines this century. However, little research has been done to examine how benthic foraminifera communities vary across a DO gradient offshore of southern California. The southern California continental margin is characterized by variable bathymetry and isolated low oxygen basins and high productivity and is an ideal location to investigate the impacts of DO and changing climate on benthic foraminifera. The objectives of this research were to 1) characterize how foraminifera communities vary spatially and with depth and DO and 2) to examine if there have been changes in these communities over the past 20 years. In 2018-19, sediment samples from the sedimentwater interface were collected using a multicorer at five sites of variable depth (200-900 m) from 10 to 170 kilometers offshore of southern California. Two of these sites had been sampled annually from 2001- 2012. Though the communities at all sites included most taxa, the relative percent and abundance of each taxa varied between sites. Sites with reduced DO were dominated by Uvigerina and Bolivina, with a large decrease in Cassidulina. Generally, the same morphotypes were seen across two decades of observation at two sites without a clear pattern of secular variability. Further studies should be done to examine how hypoxic-associated species vary across the full depth range of the oxygen minimum layer and whether these taxa are developing morphological adaptations to cope with the changing environment. 

The Tijuana River Watershed encompasses 1750 square miles of territory in both Mexico and the United States, culminating at the National EstuarineResearch Reserve. While this area comprises one of the largest undisturbed wetlands in the state, it is one of the most polluted rivers in SouthernCalifornia, draining raw sewage and nonpoint source pollution. Despite extensive research, microplastic pollution along the beaches has not been explored. The objective of this study is to determine how the abundance and morphology of microplastic pollution in beach sediments vary with distance along the littoral cell from the Tijuana River outfall. Twenty samples were collected at 10 sites that span from the Tijuana River outfall to Mission Beach, San Diego. They are characterized as outfall sites, low-visitation beaches near the outfall, and high-visitation beaches further from the outfall. Solutions of 100ml sediment and 400ml hyper-saline solution were mixed and settled for 16 hours before being processed using a vacuum filtration system in a laminar fl ow hood. The microplastics (MP)were counted and classified using light microscopy. Laboratory practices to reduce laboratory contamination were employed and analytical blanks were run for every 3 samples. MPs ranged from 1 to 199/100ml sediment, of which approximately 91% were fibers. The greatest MP abundance occurred at the river outfall sites, but recovery rates were highly variable, and the analytical blanks ranged from 3-63/100ml sediment. The results oft his study suggest that microplastic distribution in sandy beach sediments is patchy but higher near the Tijuana River Outfall, and that future studies should report analytical blanks and employ methods to reduce contamination. Understanding the relationship between watersheds and microplastic distributions may inspire policy change on water quality protections in watersheds. 

Coral reefs in the US Virgin Islands (USVI) are threatened by multiple human impacts such as coastal development and pollution. In St. John,USVI, watershed development and unpaved roads have been shown toincrease the delivery of sediment and land-based pollutants to sensitive coral reef habitats. Hallock et al. (2003) described a “FORAM Index” (FI),based on the proportion of symbiont-bearing foraminifera. The FI is used asa proxy for water quality in tropical coral reef environments and predicts whether water quality is adequate for reef growth or recovery. The objectives of this study are 1) to examine differences between the FI in coral reefs below areas of watershed development (with abundant unpaved roads) compared to below undeveloped watersheds that are protected within the Virgin Islands National Park, and 2) to examine if the FI changed from 2011 to 2013. Benthic sediment samples (top 1-2 cm) were collected using snorkel and SCUBA in 2010, 2011, and 2013 from three coral reef sites, one below a developed watershed, one below a minimally developed watershed and one from a mangrove area with coral reefs (Hurricane Hole).Samples were wet sieved (63μm), split, and 150-200 Foraminifera were picked and counted. Foraminifera were then identifi ed and classified as symbiont-bearing, opportunistic, or heterotrophic. Finally, the FI was calculated for each site. The FIs at minimally developed sites were greater than at developed sites, indicating better water quality at sites protected by the national park. The FI increased between the years, suggesting a slight improvement in water quality over time, which may be related to the paucity of large storms or the implementation in 2011 of watershed restoration. The FORAM Index can be used as part of regular reef monitoring to track the condition of coral reefs. 

Foraminifera (single celled protists with tests primarily of Calcium Carbonate) are directly influenced by ocean warming and hydrographic changes such as expansion of the low oxygen areas associated with anthropogenic climate change. Benthic and planktonic foraminifera communities are good indicators of hydrographic conditions at the sea-floor and sea surface, respectively. Though previous studies have demonstrated that there has been overall ocean surface warming in Southern California and that the oxygen minimum zone has expanded, the relationship between water temperature, dissolved oxygen and foraminifera abundance in the area offshore San Diego has not been extensively examined. Cored sediment samples along with hydrographic data collected during annual research cruises (2001-2012, 2018) on the RV Sproul at three stations (water depth 100 m, 200m 300 m) due west from San Diego, CA provide an opportunity to evaluate how benthic and planktonic foraminiferal communities have changed over the past 19 years. The objective of this research was to identify the foraminifera in these sediments and compare patterns between years to temperature and dissolved oxygen (DO). Sediment samples from the upper 1 cm of the seafloor using a multicore were sieved and the foraminifera were picked and examined under a Leica S9i microscope for identification to genus. Sea surface and bottom water temperature and DO concentrations were measured using a CTD. Analyses of the variation between sites and over time will indicate whether benthic and planktonic community changes track environmental changes in temperature and dissolved oxygen, providing valuable data to assess whether climate change is impacting marine communities. 

Microplastics are abundant in beach and bay sediments near urban areas. However, it is less well known whether they are present in the sediments of the shelves and isolated deep basins offshore of southern California. The objectives of this research were a) to test the best methodologies to extract microplastics from organic-rich sediments (silty sands), and b) to determine how the abundance of microplastics in sediments collected from offshore shelves and deep basins compared to their abundance in sediments of San Diego Bay (< 5m depth). Surface sediment samples were collected using a multicore from shelves (10-14km offshore; 100-300 m deep) and basins (90-130km offshore; 618-997m deep) on two cruises in 2018 on the RV Sally Ride and RV Sproul. For comparison, shallow (2-5m deep) sediments were collected in San Diego Bay. To extract microplastics from the samples, 78-100mL of sediment from the upper 1cm layer of the core was processed by density floatation in Zinc Chloride (1.5 g/cm ³). Floating material was then vacuum filtered and identified by counting under a light microscope. Analytical blanks were processed everythree samples and methods were further modified to minimize the amount of contaminant plastic found on filters. The mean [SD] abundance of microplastics in the sediments of San Diego Bay (2.5 [2.3] pieces/ml)was over 4 times greater than in the shelf (0.42 [.11] pieces/ml) and offshore deep basin sediments(0.57 [0.22] pieces/ml). We found microplastic abundances above analytical blanks at all 10 off shore sites including the deep basins. A better understanding of the microplastic distributions in off shore sediments will help us better predict the impact of plastics on deep-sea marine