Patrick T. Schwing

The North Atlantic is an ocean basin with a diversity of deep-sea ecosystems. Here we provide a summary of the topography and oceanography of the North Atlantic including the Gulf of Mexico and Caribbean Sea, provide a brief overview of the history of scientific research therein, and review the current status of knowledge of each of 18 pelagic and benthic deep-sea ecosystems, with a particular focus on knowledge gaps. We analyse biodiversity data records across the North Atlantic and highlight spatial data gaps that could provide important foci for future expeditions. We note particular data gaps in EEZs of nations within and bordering the Caribbean Sea. Our data provide a baseline against which progress can be tracked into the future. We review human impacts caused by fishing, shipping, mineral extraction, introduction of substances, and climate change, and provide an overview of international, regional and national measures to protect ecosystems. We recommend that scientific research in the deep sea should focus on increasing knowledge of the distribution and the connectivity of key species and habitats, and increasing our understanding of the processes leading to the delivery of ecosystem services. These three pillars - distribution, connectivity, ecosystem function - will provide the knowledge required to implement conservation and management measures to ensure that any deep-sea development in the future is sustainable. Infrastructure and capacity are unevenly distributed and implementation of strategies that will lead to more equitable deep-sea science is required to ensure that essential science can be delivered.

Microplastic pollution is an increasingly alarming concern with widespread global distribution in aquatic environments. Spatial and temporal differences in microplastic abundance were evaluated in the Eastern Oyster, Crassostrea virginica, at six sites within Tampa Bay. Oyster tissue was digested using 30 % hydrogen peroxide (H 2 O 2) and microplastics were quantified using Nile Red stain and fluorescent particle excitement. A total of 3025 microplastics were found throughout six study sites over two seasons (winter 2021 and summer 2022) with varying site types. Microfragments (n=2867) made up the majority of microplastics, as compared to microfibers (n=158). Significant differences were observed among the sites studied, site type, and their location in the bay. Outflow and marina areas had significantly higher (p<0.01) amounts of microplastics compared to preserve areas, and the east bay had significantly higher (p<0.05) amounts than the west bay. Findings suggest micro-plastic contamination is associated with higher urbanization, proximity to drainage basins, and recreation.

The Gulf of Mexico (GoM) is a unique ecosystem due to its physical characteristics, being influenced by the Mississippi River in the north and the Loop Current from the south, resulting in a gradient of organic to carbonate sediment composition from north to south. The continental slope of the northern and southwestern portions of the GoM are generally well studied; however, less is known about the southeastern GoM along the slope of Cuba. To fill this knowledge gap, sediment cores were collected in 2017 at nine stations (974–1580 m depth) to determine abiotic controls on the deep-sea benthic macrofauna community. Oceanographic data indicated a stratified water column typical of an oligotrophic ocean and no evidence of hypoxia. Sediment texture and composition indicated a west-east gradient likely determined by downslope transport of terrigenous material in the eastern part with a high proportion of carbonate in the west. Heavy metals (Cu, Hg, Pb, and Zn) at concentrations known to cause adverse benthic effects were present in the east near the city of Havana, with the macrofauna community showing characteristics indicative of environmental stress. Overall, this region supported a diverse community of macrofauna families of low abundance, typically only 1–2 animals, and high variability among replicates within stations. Rarefaction curves revealed higher biodiversity per number of individuals in the samples from Cuba compared to those from the nGoM at similar depths, though more samples would be needed to better reveal the true diversity. The major factors influencing macrofauna communities in the continental slope off northwestern Cuba are most likely the lack of organic-rich sediment and low sediment deposition rates, both of which can be attributed to the strong currents and lack of major terrigenous input, along with the regular natural disturbances which prevents domination.
•Along the Cuban slope, there was a total of 275 macrofauna collected from 65 families and 9 phyla in 25 cores.•Evidence of toxic levels of heavy metals and adverse community impacts were observed from the station offshore of Havana.•Southeast GoM has low abundance, but higher diversity and evenness compared to northern GoM samples from comparable depths.•Highly heterogenous habitat along Cuban slope resulting in large variation in macrofauna communities.

Sediment cores were collected in the Gulf of Mexico (GoM) to investigate the sediment record of synthetic based drilling mud (SBM) and evaluate the scope of the Deepwater Horizon (DwH) oil spill. Synthetic drilling mud containing barium sulfate is used at oil drilling sites to control the temperature and pressure inside the well during drilling activities. On April 20, 2010, the DwH oil spill triggered the release of over 4 million barrels of oil in the ocean. Attempts were made to stop the flow of oil from the well, including pumping synthetic barium sulfate (barite) drilling mud into the well. This failed to stop or reduce the oil flow and nearly 30,000 barrels of drilling mud were dispersed onto the seafloor. Due to the unique characteristics and uses of SBMs, they may be used as tracers in deep-sea sediments to investigate the environmental implications of barium from oil drilling and assist with the evaluation of the implications of barium increases in benthic environments. The objectives of this research are as follows: (I) Determine if there is variability of barium in sediments in northeast the GoM, (II) If yes, determine if this can be attributed to oil drilling activities and/or other anthropogenic activities. Sediment cores were analyzed by X-ray Fluorescence (XRF) spectroscopy to determine the elemental composition of sediment samples and evaluate variability in Ba concentrations. Short lived radioisotope analyses ( (super 210) Pb) were conducted to provide age control over the past approximately 100 years to determine timing of Ba input. Preliminary findings indicate that sediment surrounding the DwH site exhibit increased concentrations of Ba at the surface, likely due to the DwH event. Samples collected from areas of active drilling exhibit spikes in Ba concentrations at various intensities possibly indicating drilling activities from surrounding wells. This research can be used to evaluate the effectiveness of regulations on synthetic drilling mud put in place to prevent contamination and toxicity to benthic communities, as well as provide a potentially more persistent tracer of oil spill events. This will help further determine the spatial extent of the DwH event on the seafloor as well as its preservation in the sedimentary record.

Microplastics have accumulated in the environment since plastic production began, with present-day observations that range from marine trenches to mountains. However, research on microplastics has only recently begun so it is unclear how they have changed over time in many oceanic regions. Our study addressed this gap by quantifying the temporal and spatial dynamics of microplastics in two deep-water regions of the Gulf of Mexico (GOM). We isolated agglutinated foraminifera from sediment cores and assessed microplastics that were incorporated into their tests. Our results indicated that microplastics were incorporated by agglutinated foraminifera after plastic production began. Microplastics were higher at deep-water sites and closer to the Mississippi River. This study confirms the presence of microplastic incorporation into agglutinated foraminifera tests and investigates microplastics in deep-water sediments in the GOM. Additional work is needed to fully identify the distribution of microplastics across the GOM and other oceanic basins.

This dataset includes CTD and environmental data for four stations collected onboard R/V Weatherbird II cruise WB-0522 in the Gulf of Mexico from 2022-05-16 to 2022-05-19. The dataset includes 4 profiles/casts of temperature, salinity, conductivity, chlorophyll-a and colored dissolved organic matter fluorescence, turbidity, oxygen saturation, sound velocity, altimetry and Photosynthetically Available Radiation (PAR). R/V Weatherbird II cruise WB-0522 was led by chief scientists Dr. Patrick Schwing, Dr. Rebekka Larson, and Dr. Gregg Brooks. Processed data are in text format.

This dataset includes CTD and environmental data for four stations collected onboard R/V Weatherbird II cruise WB-0523 in the Gulf of Mexico from 2023-05-23 to 2023-05-31. The dataset includes profiles/casts of temperature, salinity, conductivity, chlorophyll-a and colored dissolved organic matter fluorescence, turbidity, oxygen saturation, sound velocity, altimetry and Photosynthetically Available Radiation (PAR). R/V Weatherbird II cruise WB-0523 was led by chief scientists Dr. Patrick Schwing, Dr. Rebekka Larson, and Dr. Gregg Brooks. Processed data are in CNV fromat.

The first full-scale deep-sea polymetallic nodule mining test in 44 years was carried out late 2022 in the Clarion-Clipperton Fracture Zone of the abyssal Pacific Ocean. Deep-sea mining generates sediment plumes, posing potential ecological risks to benthic communities. To understand these impacts it is crucial to define the spatial breadth and magnitude of these ambient collector plumes. This study utilizes X-ray fluorescence (XRF) and X-ray diffraction (XRD) techniques for monitoring deep-sea mining plumes to evaluate sediment deposition and removal in an area actively targeted for commercial mining. To obtain representative samples and spatial coverage, coring sites were selected based on their location in or adjacent to a modeled plume from this collector test. Ultimately six cores were chosen for evaluation based on model projections and distance from source - "track" sites were located within the path of the collector vehicle, 0.2 km East from track, 0.5 km East from track, 2 km East from track, and a control site 4 km away and to the northwest. After retrieval the cores were split, photographed, and frozen while aboard the research vessel for later transport and analysis in the lab. Elemental analysis was carried out in two phases. During phase one the frozen cores were scanned in 1-cm increments utilizing an XRF spectrometer and data were compiled in down-core concentrations per element. In phase two, five subsamples per core were selected based on the down-core data. The samples were then freeze-dried, finely ground (<65mu m), homogenized, and pressed into pucks for reanalysis by XRF to eliminate artifacts from in-situ scanning. Mineralogic analysis was conducted with a desktop XRD using the Crystallography Open Database (COD) for peak matching and Rietveld refinement for quantification. Initial results from down-core XRF data show correlative marker horizons among multiple cores and suggest a removal of the top approximately 4-5 cm of sediment from the collector track. Phase two XRF analysis eliminated variances in core surface scans and provided a more accurate quantification of elements in the top 3 cm. XRD analysis shows a mix of iron and manganese oxides with mainly silica clays and some carbonates. Spatial comparisons are in progress between the coring sites for Phase 2 XRF as well as XRD. This work is being performed by an undergraduate marine geology student at Eckerd College.

The Deep Water Horizon (DWH) oil spill occurred in the Northern Gulf of Mexico (NGoM) in 2010. Over 700 million liters of oil spilled into the NGoM in the 87 days the wellhead was actively leaking. Samples were taken from sites annually to semi-annually from 2010-2023 to provide a spatial and temporal benthic assessment for the NGoM. Reference conditions provide an ecological snapshot of the marine environment and allow for quantitative assessment of impact and response in the case of future oil spills. Benthic foraminifera, which are single-celled, testate organisms that inhabit the seafloor have proven to be excellent indicators and records of ecological change. Stable carbon isotopes in benthic foraminifera shells (tests) have also proven to be effective indicators of petroleum carbon incorporation into the benthic system. Seafloor sediment cores were most recently collected in 2023, at specific time series sites in the NGoM, as a part of the Scientist-At-Sea program. The sediment cores were subsampled at 2 mm increments. Calcareous foraminifera species, Cibicidoides pachyderma and C. wuellerstorfi, were isolated for stable isotope (oxygen and carbon) analysis using a stable isotope ratio mass spectrometer (SIRMS). Stable isotopes from benthic foraminifera from two of the time-series sites have been measured continually from 2010 to 2017. This study will provide a comparison of the latest benthic foraminifera stable carbon isotopes profiles with previous collections to determine long-term recovery of the system, gain insight into natural variability, and establish long-term preservation of the DWH signal in fossil (downcore) benthic foraminifera tests. These records will continue to aid in the understanding of natural seafloor carbon cycling, and also in the event of future pollution events such as oil spills.