Bent
Shavonna M.
Bent
Shavonna M.
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ArticleDifferential patterns of microbiota recovery in symbiotic and aposymbiotic corals following antibiotic disturbance(American Society for Microbiology, 2021-04-13) Bent, Shavonna M. ; Miller, Carolyn A. ; Sharp, Koty H. ; Hansel, Colleen M. ; Apprill, AmyMicrobial relationships are critical to coral health, and changes in microbiomes are often exhibited following environmental disturbance. However, the dynamics of coral-microbial composition and external factors that govern coral microbiome assembly and response to disturbance remain largely uncharacterized. Here, we investigated how antibiotic-induced disturbance affects the coral mucus microbiota in the facultatively symbiotic temperate coral Astrangia poculata, which occurs naturally with high (symbiotic) or low (aposymbiotic) densities of the endosymbiotic dinoflagellate Breviolum psygmophilum. We also explored how differences in the mucus microbiome of natural and disturbed A. poculata colonies affected levels of extracellular superoxide, a reactive oxygen species thought to have both beneficial and detrimental effects on coral health. Using a bacterial and archaeal small-subunit (SSU) rRNA gene sequencing approach, we found that antibiotic exposure significantly altered the composition of the mucus microbiota but that it did not influence superoxide levels, suggesting that superoxide production in A. poculata is not influenced by the mucus microbiota. In antibiotic-treated A. poculata exposed to ambient seawater, mucus microbiota recovered to its initial state within 2 weeks following exposure, and six bacterial taxa played a prominent role in this reassembly. Microbial composition among symbiotic colonies was more similar throughout the 2-week recovery period than that among aposymbiotic colonies, whose microbiota exhibited significantly more interindividual variability after antibiotic treatment and during recovery. This work suggests that the A. poculata mucus microbiome can rapidly reestablish itself and that the presence of B. psygmophilum, perhaps by supplying nutrients, photosynthate, or other signaling molecules, exerts influence on this process. IMPORTANCE Corals are animals whose health is often maintained by symbiotic microalgae and other microorganisms, yet they are highly susceptible to environmental-related disturbances. Here, we used a known disruptor, antibiotics, to understand how the coral mucus microbial community reassembles itself following disturbance. We show that the Astrangia poculata microbiome can recover from this disturbance and that individuals with algal symbionts reestablish their microbiomes in a more consistent manner compared to corals lacking symbionts. This work is important because it suggests that this coral may be able to recover its mucus microbiome following disturbance, it identifies specific microbes that may be important to reassembly, and it demonstrates that algal symbionts may play a previously undocumented role in microbial recovery and resilience to environmental change.
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ArticleIron depletion in the deep chlorophyll maximum: mesoscale eddies as natural iron fertilization experiments(American Geophysical Union, 2021-11-17) Hawco, Nicholas J. ; Barone, Benedetto ; Church, Matthew J. ; Babcock-Adams, Lydia ; Repeta, Daniel J. ; Wear, Emma K. ; Foreman, Rhea K. ; Björkman, Karin M. ; Bent, Shavonna M. ; Van Mooy, Benjamin A. S. ; Sheyn, Uri ; DeLong, Edward F. ; Acker, Marianne ; Kelly, Rachel L. ; Nelson, Alexa ; Ranieri, John ; Clemente, Tara M. ; Karl, David M. ; John, Seth G.In stratified oligotrophic waters, phytoplankton communities forming the deep chlorophyll maximum (DCM) are isolated from atmospheric iron sources above and remineralized iron sources below. Reduced supply leads to a minimum in dissolved iron (dFe) near 100 m, but it is unclear if iron limits growth at the DCM. Here, we propose that natural iron addition events occur regularly with the passage of mesoscale eddies, which alter the supply of dFe and other nutrients relative to the availability of light, and can be used to test for iron limitation at the DCM. This framework is applied to two eddies sampled in the North Pacific Subtropical Gyre. Observations in an anticyclonic eddy center indicated downwelling of iron-rich surface waters, leading to increased dFe at the DCM but no increase in productivity. In contrast, uplift of isopycnals within a cyclonic eddy center increased supply of both nitrate and dFe to the DCM, and led to dominance of picoeukaryotic phytoplankton. Iron addition experiments did not increase productivity in either eddy, but significant enhancement of leucine incorporation in the light was observed in the cyclonic eddy, a potential indicator of iron stress among Prochlorococcus. Rapid cycling of siderophores and low dFe:nitrate uptake ratios also indicate that a portion of the microbial community was stressed by low iron. However, near-complete nitrate drawdown in this eddy, which represents an extreme case in nutrient supply compared to nearby Hawaii Ocean Time-series observations, suggests that recycling of dFe in oligotrophic ecosystems is sufficient to avoid iron limitation in the DCM under typical conditions.
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ArticleSixty years of glacial retreat behind Palmer Station, Antarctica(Cambridge University Press, 2023-12-12) Cimino, Megan A. ; Goerke, Marissa A. ; Bent, Shavonna M.Palmer Station is the smallest of three US scientific research bases in Antarctica. It is located on the south-western coast of Anvers Island, which is mostly glaciated, on the western side of the Antarctic Peninsula. Here, the temperature is considered mild (on average -4.7°C in winter and 1.9°C in summer from 1997 to 2023), but rapid warming is occurring despite high interannual variability (Jones et al. Reference Jones, Bromwich, Nicolas, Carrasco, Plavcová, Zou and Wang2019, Carrasco et al. Reference Carrasco, Bozkurt and Cordero2021). Palmer Station was constructed in 1968 to support scientific research, replacing ‘Old Palmer’ established in 1965 on Amsler Island (~2 km north-west of Palmer Station). The station was named after Nathaniel B. Palmer, an American sealer from Connecticut, who may have been the first person to see Antarctica during an exploratory voyage in 1820. Palmer Station is built on solid rock, and it has two main buildings and three smaller ones, two fuel tanks and a pier with a station maximum capacity of 44 people. In 1990, it was designated a Long-Term Ecological Research (LTER) site (Smith et al. Reference Smith, Baker, Fraser, Hofmann, Karl and Klinck1995), but it also supports various research efforts on climate, aeronomy, astrophysics, glaciology and marine and terrestrial organisms. Behind Palmer Station sits the Marr Ice Piedmont, which once covered most of the rocky terrain (Fig. 1). Here, we present for the first time a 60 year record of glacial retreat behind Palmer Station from 1963 to 2023 (some years shown in McClintock et al. Reference McClintock, Ducklow and Fraser2008, Groff et al. Reference Groff, Beilman, Yu, Ford and Xia2023).