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Better together? Lessons on sociality from Trichodesmium
Get PDFThe N2-fixing cyanobacterium Trichodesmium is an important player in the oceanic nitrogen and carbon cycles. Trichodesmium occurs both as single trichomes and as colonies containing hundreds of trichomes. In this review, we explore the benefits and disadvantages of colony formation, considering physical, chemical, and biological effects from nanometer to kilometer scale. Showing that all major life challenges are affected by colony formation, we claim that Trichodesmium\u27s ecological success is tightly linked to its colonial lifestyle. Microbial interactions in the microbiome, chemical gradients within the colony, interactions with particles, and elevated mobility in the water column shape a highly dynamic microenvironment. We postulate that these dynamics are key to the resilience of Trichodesmium and other colony formers in our changing environment
Coexistence of dominant marine phytoplankton sustained by nutrient specialization
Get PDFProchlorococcus and Synechococcus are the two dominant picocyanobacteria in the low-nutrient surface waters of the subtropical ocean, but the basis for their coexistence has not been quantitatively demonstrated. Here, we combine in situ microcosm experiments and an ecological model to show that this coexistence can be sustained by specialization in the uptake of distinct nitrogen (N) substrates at low-level concentrations that prevail in subtropical environments. In field incubations, the response of both Prochlorococcus and Synechococcus to nanomolar N amendments demonstrates N limitation of growth in both populations. However, Prochlorococcus showed a higher affinity to ammonium, whereas Synechococcus was more adapted to nitrate uptake. A simple ecological model demonstrates that the differential nutrient preference inferred from field experiments with these genera may sustain their coexistence. It also predicts that as the supply of NO3 2 decreases, as expected under climate warming, the dominant genera should undergo a nonlinear shift from Synechococcus to Prochlorococcus, a pattern that is supported by subtropical field observations. Our study suggests that the evolution of differential nutrient affinities is an important mechanism for sustaining the coexistence of genera and that climate change is likely to shift the relative abundance of the dominant plankton genera in the largest biomes in the ocean. IMPORTANCE Our manuscript addresses the following fundamental question in microbial ecology: how do different plankton using the same essential nutrients coexist? Prochlorococcus and Synechococcus are the two dominant picocyanobacteria in the low-nutrient surface waters of the subtropical ocean, which support a significant amount of marine primary production. The geographical distributions of these two organisms are largely overlapping, but the basis for their coexistence in these biomes remains unclear. In this study, we combined in situ microcosm experiments and an ecosystem model to show that the coexistence of these two organisms can arise from specialization in the uptake of distinct nitrogen substrates; Prochlorococcus prefers ammonium, whereas Synechococcus prefers nitrate when these nutrients exist at low concentrations. Our framework can be used for simulating and predicting the coexistence in the future ocean and may provide hints toward understanding other similar types of coexistence
Tracking carbon from subduction to outgassing along the Aleutian-Alaska Volcanic Arc
No full textSubduction transports volatiles between Earth’s mantle, crust, and atmosphere, ultimately creating a habitable Earth. We use isotopes to track carbon from subduction to outgassing along the Aleutian-Alaska Arc. We find substantial along-strike variations in the isotopic composition of volcanic gases, explained by different recycling efficiencies of subducting carbon to the atmosphere via arc volcanism and modulated by subduction character. Fast and cool subduction facilitates recycling of ~43 to 61% sediment-derived organic carbon to the atmosphere through degassing of central Aleutian volcanoes, while slow and warm subduction favors forearc sediment removal, leading to recycling of ~6 to 9% altered oceanic crust carbon to the atmosphere through degassing of western Aleutian volcanoes. These results indicate that less carbon is returned to the deep mantle than previously thought and that subducting organic carbon is not a reliable atmospheric carbon sink over subduction time scales
Southern Ocean glacial conditions and their influence on deglacial events
No full textThe Southern Ocean is an important regulator of global CO2 levels and likely had a key role in lowering atmospheric CO2 levels during the Last Glacial Maximum (LGM) and driving the subsequent increase during the following deglaciation. Nonetheless, debate continues surrounding the relative importance of Northern versus Southern Hemisphere forcing during deglacial events. In this Review, we compare modern Southern Ocean conditions with those in the LGM and deglacial period, identifying factors that were critical in initiating the glacial termination. During the LGM, North Atlantic sourced waters appear to have shoaled and were largely absent from the glacial Southern Ocean. Increased ocean stratification, shoaling of the chemical divide and increased nutrient utilization at the surface contributed to glacial carbon sequestration in deep waters. Warming at mid-latitudes of the Southern Hemisphere and the Southern Ocean began at ~21 ka, preceding deglaciation, indicating insolation changes could have driven early atmosphere–ocean warming that initiated the shifting of ocean fronts leading to the release of carbon sequestered in the LGM. Southern Ocean dynamics appear to have been substantial, or even the critical, factors initiating the termination of the LGM before deepening of North Atlantic sourced waters. Future research should focus on better resolving deglacial chemical and physical changes in Southern Ocean waters and their representation in numerical models
Every Quilt Tells a Story
No full textThis presentation incorporates the video created through the support of the “Winnie Grant” awarded to Welters, Jerome, and Kelly in Center for Humanities’ Fall 2021 Grant cycle. The video’s title is “Every Quilt Tells a Story.” Textiles in general, and quilts in particular, offer opportunities to explore humanities themes through examination of material culture. Quilts express changes in textile production through their fabrics, in aesthetic preferences, and in stories surrounding the circumstances of their making and use. The seven quilts to be featured in the video explore themes of changing technology, trade, gender, and aesthetic preferences. If possible, one of the quilts will be brought to the presentation to discuss what can be gleaned from a material culture approach to history.
The larger goal is to showcase objects in the Historic Textile and Costume Collection and make URI students and faculty aware of the possibilities for their own research and teaching. The discussion will involve how to fuse object-based research with documentary research. The workshop should attract students and faculty in the fields of textiles, art, and social history as well as the history of Rhode Island and the changing technologies and influences surrounding textile manufacturing in America.
Welters, Jerome, and Kelly’s project is featured in the Rhode Island issue of Quiltfolk magazine
Transects of polycyclic aromatic hydrocarbons and organochlorine pesticides in an urban estuary using passive samplers
Get PDFHydrophobic organic contaminants (HOCs) are tracers of anthropogenic impacts, which can negatively affect water quality. The relative importance of new emissions versus the remobilization of HOCs from legacy reservoirs is not well constrained. Polyethylene passive samplers were deployed in vertical profiles at four sites to determine the concentrations and gradients of atmospheric and freely dissolved polycyclic aromatic hydrocarbons (PAHs) and freely dissolved organochlorinated pesticides (OCPs) in Narragansett Bay, an urban estuary. The concentrations of the sum of 20 PAHs ranged from 4.3 to 240 ng/m3 in the air and 3.2–21 ng/L in the water column, dominated by phenanthrene and pyrene. OCP concentrations varied from below the detection limit to 150 ng/L in the water column. Common OCPs included α-hexachlorocyclohexane, hexachlorobenzene, and aldrin. Gradients displayed net deposition for PAHs, but equilibrium through the water column. Results from this study provided evidence that key OCPs displayed mostly similar concentrations (at or near equilibrium) in the water at both Conimicut Point and Block Island
Shallow Volcano-Tectonic Structures on the Island of Hawai\u27i Imaged by Multimode Rayleigh Wave Ambient Noise Tomography
No full textSeismic tomography of shield volcanoes can be used to better understand its structure, formation, and evolution. Previous tomographic studies on the Island of Hawai\u27i used body waves from earthquakes and active sources and had limited resolution in the shallow crust. In this study, we obtained the empirical Green Functions (EGFs) and empirical Green Tensors (EGTs) from cross-correlating and stacking of multiyear seismic ambient noise recorded on the island. The EGFs/EGTs contained fundamental mode and first higher mode Rayleigh waves. The different modes were separated with a new algorithm and their group velocities were measured. Using the group arrival times, we inverted for two-dimensional group velocity maps, which provide, for the first time, a full coverage of the Island of Hawai\u27i. From the group velocity maps, we inverted for a three-dimensional shear wave velocity model, which shows strong lateral variations and yields new insights into the structure and growth of the volcanoes on the island: Kı̄lauea\u27s East Rift Zone has prominent high velocities at all depths, whereas the current rift zones of Mauna Loa are characterized by intermediate to high velocities only at depths greater than 1 km below ground surface, which may be attributed to their relatively short history and less developed state. The flanks of the volcanoes, some cut by fault zones, displayed low velocities at over a range of depths, generally interpreted as consisting of extrusive rocks, which could be further shattered by faulting
Doppler effects on acoustic ranging uncertainties on autonomous underwater vehicles in the Beaufort Sea
No full textMoving and depth-varying receivers, such as autonomous underwater vehicles (AUVs), provide a great tool for acoustic remote sensing applications. An array of acoustic sources can be used to provide long-range acoustic positioning for AUVs, but there are challenges in the form of subsea position uncertainties that can be exacerbated by Doppler delay shifts. During the Canada Basin Acoustic Propagation Experiment (CANAPE) two M1 Seagliders equipped with WHOI micromodem acoustic receivers were deployed during August 2017. Acting as moving receivers, the Seagliders navigated the Beaufort Sea in and around the CANAPE array, recording transmissions from the broadband acoustic sources at varying ranges and depths of 2-530 km and surface to 750 m, respectively. The sources transmitted 135-second linear frequency modulated signals with a bandwidth of 100 Hz centered around 250 Hz. This work focuses on the Doppler delay shift effects on acoustic ranging uncertainties using these signals. Using vehicle attitude measurements over the duration of the signal receptions, it was found that 91 percent of the acoustic receptions included ranging uncertainties of 10 m or more due to Doppler, with particular impact at closer ranges of 50 km or less
Determining the Effects of Pelleted Cranberry Vine Grains on the Ewe and Offspring during Pregnancy and Lactation
Get PDFWhen creating any new anti-parasitic interventions, it is important to evaluate their effects across all life stages. This study had three objectives, which were to evaluate the effect of feeding cranberry vine pellet (CVP) on (1) ewes’ body weights and BCS during late gestation and lactation; (2) ewes’ milk quality during lactation; and (3) lambs’ body weight and growth parameters from birth to 65 days of age. Across two years, 41 Dorset ewes were fed either a 50% CVP or a matching control pellet (CON) from 104 ± 1.60 days of gestation for 62.8 ± 0.68 days of lactation. Measurements were collected from ewes (BW, BCS, and milk) and lambs (BW and body size). Milk from CVP ewes exhibited reduced milk fat and solids (p \u3c 0.01) and increased concentrations of milk urea nitrogen (p = 0.02) when evaluated for the treatment–time. There was no significant difference in the BCS, protein, lamb BW, or growth measurements for treatment–time (p ≥ 0.05). Additional research that targets blood biochemistry and metabolic assessments is needed to fully determine the impact of this pellet on ewes and lambs
