This work has been motivated by the current interest in using fullerenes as a possible reinforcement in structural materials. The fullerenes (of which C60 is the most common) are nanometer in size and have been observed to be stable in contact with various metal systems. Therefore, they offer a nanosize reinforcement that is lightweight and hollow. In this research the emphasis was on processing metals with fullerene additions where the fullerenes were dispersed throughout the metal. Various processing approaches were employed to produce nanocrystalline materials, thin films, and powder-processed composites. Indications are that fullerenes remained unaltered with each processing approach in matrices of tin, copper, and aluminum. A key aspect of the processing of metals containing dispersed fullerenes was the use of fullerene sublimation. Along with the various processing methods identified, the methods of characterizing the fullerenes in the metals were also identified.
Terrestrial runoff can negatively impact marine ecosystems through stressors including excess nutrients, freshwater, sediments, and contaminants. Severe storms, which are increasing with global climate change, generate massive inputs of runoff over short timescales (hours to days); such runoff impacted offshore reefs in the northwest Gulf of Mexico (NW GoM) following severe storms in 2016 and 2017. Several weeks after coastal flooding from these events, NW GoM reef corals, sponges, and other benthic invertebrates ∼185 km offshore experienced mortality (2016 only) and/or sub-lethal stress (both years). To assess the impact of storm-derived runoff on reef filter feeders, we characterized the bacterial communities of two sponges, Agelas clathrodes and Xestospongia muta, from offshore reefs during periods of sub-lethal stress and no stress over a three-year period (2016—2018). Sponge-associated and seawater-associated bacterial communities were altered during both flood years. Additionally, we found evidence of wastewater contamination (based on 16S rRNA gene libraries and quantitative PCR) in offshore sponge samples, but not in seawater samples, following these flood years. Signs of wastewater contamination were absent during the no-flood year. We show that flood events from severe storms have the capacity to reach offshore reef ecosystems and impact resident benthic organisms. Such impacts are most readily detected if baseline data on organismal physiology and associated microbiome composition are available. This highlights the need for molecular and microbial time series of benthic organisms in near- and offshore reef ecosystems, and the continued mitigation of stormwater runoff and climate change impacts.
SummaryTerrestrial runoff can negatively impact marine ecosystems through stressors including excess nutrients, freshwater, and contaminants. Severe storms, which are increasing with global climate change, generate massive inputs of runoff over short timescales (hours to days); such runoff impacted offshore reefs in the northwest Gulf of Mexico (NW GoM) following severe storms in 2016 and 2017. Several weeks after coastal flooding from these events, NW GoM reefs experienced mortality (2016 only) and/or sub-lethal stress (both years). To assess the impact of storm-derived runoff on reef filter feeders, we characterized the microbiomes of two sponges, Agelas clathrodes and Xestospongia muta, during periods of lethal stress, sub-lethal stress, and no stress over a three-year period (2016-2018). Increased anaerobes during lethal stress indicate hypoxic conditions were associated with the 2016 mortality event. Additionally, we found evidence of wastewater contamination (based on 16S libraries and quantitative PCR) in sponges 185 km offshore following storms (2016 and 2017), but not during the non-flooding year (2018). We show that water quality changes following severe storms can impact offshore benthic organisms, highlighting the need for molecular and microbial time series from near- and offshore reef ecosystems, and for the continued mitigation of stormwater runoff and climate change impacts.Originality-Significance StatementStressors associated with terrestrial runoff have contributed to substantial population declines in nearshore marine ecosystems worldwide over the last three decades. It has been assumed that offshore marine ecosystems (>100 km from land) are largely unaffected by terrestrial runoff. Our findings, however, suggest that flooding events can significantly impact offshore marine organisms, based on the detection of shifted microbiomes and human pathogens in offshore sponges after extreme storm events across two separate years, and lack of detection in a non-flooding year.
One way viruses can affect coral health is by infecting their symbiotic dinoflagellate partners (Symbiodiniaceae). Yet, viral dynamics in coral colonies exposed to environmental stress have not been studied at the reef scale, particularly within individual viral lineages. We sequenced the viral major capsid protein (mcp) gene of positive-sense single-stranded RNA viruses known to infect symbiotic dinoflagellates (‘dinoRNAVs’) to analyze their dynamics in the reef-building coral, Porites lobata. We repeatedly sampled 54 colonies harboring Cladocopium C15 dinoflagellates, across three environmentally distinct reef zones (fringing reef, back reef, and forereef) around the island of Moorea, French Polynesia over a three-year period, and spanning a reef-wide thermal stress event. By the end of the sampling period, 28% (5/18) of corals in the fringing reef experienced partial mortality versus 78% (14/18) in the forereef. Over 90% (50/54) of colonies had detectable dinoRNAV infections. Reef zone influenced the composition and richness of viral mcp amino acid types (‘aminotypes’), with the fringing reef containing the highest aminotype richness. The reef-wide thermal stress event significantly increased aminotype dispersion, and this pattern was strongest in the colonies that experienced partial mortality. These findings demonstrate that dinoRNAV infections respond to environmental fluctuations experienced in situ on reefs. Further, viral productivity will likely increase as ocean temperatures continue to rise, potentially impacting the foundational symbiosis underpinning coral reef ecosystems.
Local-scale nutrient pollution can alter coral growth and reproductive output, as well as their resident communities of microorganisms (dinoflagellates in the family Symbiodiniaceae, bacteria). Yet, the ways in which nutrient pollution alters coral interactions with their microorganisms are not fully understood, and no studies have tested for transgenerational impacts of nutrient stress on coral holobionts. To investigate this, colonies of Pocillopora acuta were enriched with nitrate in situ for up to one year and monitored for planulation. Gene expression, resident microbial communities and holobiont traits were characterized in adults, as well as in planulae. Although separated by [ 5 m, clonality and chimerism were observed in the majority of coral colonies. Lineageand treatment-specific effects of nitrate treatment were detected in adults and planulae. Nitrate-enriched adults contained higher densities of Symbiodiniaceae and exhibited downregulation of genes involved in the synthesis of nitrogenous compounds. Planulae harbored higher Symbiodiniaceae and bacteria diversity than adults; this study constitutes the first assessment of these microorganisms from individual planulae. Coral-associated bacteria communities were Endozoicomonas-dominated and were not altered by nutrient treatment. Planula-associated bacteria communities differed from their parents but not from parental exposure to nutrients, and no changes in fecundity or settlement success resulted from enrichment. Taken together, these findings suggest that adult corals acclimate to chronic nutrient pollution by harboring higher Symbiodiniaceae densities, with no observed negative effects on the subsequent generation.
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