Maas Amy E.

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Amy E.

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  • Article
    The metabolic response of pteropods to acidification reflects natural CO2-exposure in oxygen minimum zones
    (Copernicus Publications on behalf of the European Geosciences Union, 2012-02-15) Maas, Amy E. ; Wishner, Karen F. ; Seibel, Brad A.
    Shelled pteropods (Thecosomata) are a group of holoplanktonic mollusks that are believed to be especially sensitive to ocean acidification because their aragonitic shells are highly soluble. Despite this concern, there is very little known about the physiological response of these animals to conditions of elevated carbon dioxide. This study examines the oxygen consumption and ammonia excretion of five pteropod species, collected from tropical regions of the Pacific Ocean, to elevated levels of carbon dioxide (0.10%, 1000 ppm). Our results show that pteropods that naturally migrate into oxygen minimum zones, such as Hyalocylis striata, Clio pyramidata, Cavolinia longirostris and Creseis virgula, were not affected by carbon dioxide at the levels and duration tested. Diacria quadridentata, which does not migrate, responds to high carbon dioxide conditions with reduced oxygen consumption and ammonia excretion. This indicates that the natural chemical environment of individual species may influence their resilience to ocean acidification.
  • Article
    Exposure to CO2 influences metabolism, calcification and gene expression of the thecosome pteropod Limacina retroversa
    (The Company of Biologists, 2018-02-13) Maas, Amy E. ; Lawson, Gareth L. ; Bergan, Alexander J. ; Tarrant, Ann M.
    Thecosomatous pteropods, a group of aragonite shell-bearing zooplankton, are becoming an important sentinel organism for understanding the influence of ocean acidification on pelagic organisms. These animals show vulnerability to changing carbonate chemistry conditions, are geographically widespread, and are both biogeochemically and trophically important. The objective of this study was to determine how increasing duration and severity of CO2 treatment influence the physiology of the thecosome Limacina retroversa, integrating both gene expression and organism-level (respiration and calcification) metrics. We exposed pteropods to over-saturated, near-saturated or under-saturated conditions and sampled individuals at 1, 3, 7, 14 and 21 days of exposure to test for the effect of duration. We found that calcification was affected by borderline and under-saturated conditions by week two, while respiration appeared to be more strongly influenced by an interaction between severity and duration of exposure, showing complex changes by one week of exposure. The organismal metrics were corroborated by specific gene expression responses, with increased expression of biomineralization-associated genes in the medium and high treatments throughout and complex changes in metabolic genes corresponding to both captivity and CO2 treatment. Genes associated with other physiological processes such as lipid metabolism, neural function and ion pumping had complex responses, influenced by both duration and severity. Beyond these responses, our findings detail the captivity effects for these pelagic organisms, providing information to contextualize the conclusions of previous studies, and emphasizing a need for better culturing protocols.
  • Dataset
    Pteropod respiration rates from NW Atlantic and NE Pacific; OC473 (2011) and NH1208 (2012)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact:, 2014-02-05) Maas, Amy E.
    Respiration rates of thecosome pteropod exposed to several O2 and CO2 concentrations. Specimens were collected and measurements taken at sea.
  • Dataset
    ZooSCAN images of zooplankton collected during OAPS MOCNESS tows during R/V Oceanus cruise OC473 in the northwest Atlantic in 2011 and R/V New Horizon cruise NH1208 in the northeast Pacific in 2012
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact:, 2021-12-03) Blanco-Bercial, Leocadio ; Maas, Amy E. ; Gossner, Hannah ; York, Amber D.
    ZooSCAN images of zooplankton collected during OAPS MOCNESS tows during R/V Oceanus cruise OC473 in the Northwestern Atlantic in 2011 and R/V New Horizon cruise NH1208 in the Northeastern Pacific in 2012. Day and night stations were sampled between 0 to 1000m depths from 35 to 50 N in the northwest Atlantic in 2011, and from 35 and 50N along CLIVAR line P17N in 2012. Some chaetognaths and all pteropods were removed prior to imaging in association with the original OAPS and ancillary projects.
  • Article
    Reexamination of the species assignment of Diacavolinia pteropods using DNA barcoding
    (Public Library of Science, 2013-01-15) Maas, Amy E. ; Blanco-Bercial, Leocadio ; Lawson, Gareth L.
    Thecosome pteropods (Mollusca, Gastropoda) are an ecologically important, diverse, and ubiquitous group of holoplanktonic animals that are the focus of intense research interest due to their external aragonite shell and vulnerability to ocean acidification. Characterizing the response of these animals to low pH and other environmental stressors has been hampered by continued uncertainty in their taxonomic identification. An example of this confusion in species assignment is found in the genus Diacavolinia. All members of this genus were originally indentified as a single species, Cavolinia longirostris, but over the past fifty years the taxonomy has been revisited multiple times; currently the genus comprises 22 different species. This study examines five species of Diacavolinia, including four sampled in the Northeast Atlantic (78 individuals) and one from the Eastern tropical North Pacific (15 individuals). Diacavolina were identified to species based on morphological characteristics according to the current taxonomy, photographed, and then used to determine the sequence of the “DNA barcoding” region of the cytochrome c oxidase subunit I (COI). Specimens from the Atlantic, despite distinct differences in shell morphology, showed polyphyly and a genetic divergence of <3% (K2P distance) whereas the Pacific and Atlantic samples were more distant (~19%). Comparisons of Diacavolinia spp. with other Cavolinia spp. reveal larger distances (~24%). These results indicate that specimens from the Atlantic comprise a single monophyletic species and suggest possible species-level divergence between Atlantic and Pacific populations. The findings support the maintenance of Diacavolinia as a separate genus, yet emphasize the inadequacy of our current taxonomic understanding of pteropods. They highlight the need for accurate species identifications to support estimates of biodiversity, range extent and natural exposure of these planktonic calcifiers to environmental variability; furthermore, the apparent variation of the pteropods shell may have implications for our understanding of the species’ sensitivity to ocean acidification.
  • Preprint
    The effect of elevated carbon dioxide on the sinking and swimming of the shelled pteropod Limacina retroversa
    ( 2017-01) Bergan, Alexander J. ; Lawson, Gareth L. ; Maas, Amy E. ; Wang, Zhaohui Aleck
    Shelled pteropods are planktonic molluscs that may be affected by ocean acidification. Limacina retroversa from the Gulf of Maine were used to investigate the impact of elevated carbon dioxide (CO2) on shell condition as well as swimming and sinking behaviours. Limacina retroversa were maintained at either ambient (ca. 400 μatm) or two levels of elevated CO2 (800 and 1200 μatm) for up to four weeks, and then examined for changes in shell transparency, sinking speed, and swimming behaviour assessed through a variety of metrics (e.g., speed, path tortuosity, wing beat frequency). After exposures to elevated CO2 for as little as four days, the pteropod shells were significantly darker and more opaque in the elevated CO2 treatments. Sinking speeds were significantly slower for pteropods exposed to medium and high CO2 in comparison to the ambient treatment. Swimming behaviour showed less clear patterns of response to treatment and duration of exposure, but overall, swimming did not appear to be hindered under elevated CO2. Sinking is used by L. retroversa for predator evasion, and altered speeds and increased visibility could increase the susceptibility of pteropods to predation.
  • Preprint
    Metabolic suppression in thecosomatous pteropods as an effect of low temperature and hypoxia in the eastern tropical North Pacific
    ( 2011-10) Maas, Amy E. ; Wishner, Karen F. ; Seibel, Brad A.
    Many pteropod species in the eastern tropical north Pacific Ocean migrate vertically each day, transporting organic matter and respiratory carbon below the thermocline. These migrations take species into cold (15-10ºC) hypoxic water (< 20 µmol O2 kg-1) at depth. We measured the vertical distribution, oxygen consumption and ammonia excretion for seven species of pteropod, some of which migrate and some which remain in oxygenated surface waters throughout the day. Within the upper 200 meters of the water column, changes in water temperature result in a ~60-75% reduction in respiration for most species. All three species tested under hypoxic conditions responded to low O2 with an additional ~35-50% reduction in respiratory rate. Combined, low temperature and hypoxia suppress the metabolic rate of pteropods by ~80-90%. These results shed light on the ways in which expanding regions of hypoxia and surface ocean warming may impact pelagic ecology.
  • Preprint
    Transcriptome-wide analysis of the response of the thecosome pteropod Clio pyramidata to short-term CO2 exposure
    ( 2015-01) Maas, Amy E. ; Lawson, Gareth L. ; Tarrant, Ann M.
    Thecosome pteropods, a group of calcifying holoplanktonic molluscs, have recently become a research focus due to their potential sensitivity to increased levels of anthropogenic dissolved CO2 in seawater and the accompanying ocean acidification. Some populations, however, already experience high CO2 in their natural distribution during diel vertical migrations. To achieve a better understanding of the mechanisms of pteropod calcification and physiological response to this sort of short duration CO2 exposure, we characterized the gene complement of Clio pyramidata, a cosmopolitan diel migratory thecosome, and investigated its transcriptomic response to experimentally manipulated CO2 conditions. Individuals were sampled from the Northwest Atlantic in the fall of 2011 and exposed to ambient conditions (~380 ppm) and elevated CO2 (~800 ppm, similar to levels experienced during a diel vertical migration) for ~10 hrs. Following this exposure the respiration rate of the individuals was measured. We then performed RNA-seq analysis, assembled the C. pyramidata transcriptome de novo, annotated the genes, and assessed the differential gene expression patterns in response to exposure to elevated CO2. Within the transcriptome, we identified homologs of genes with known roles in biomineralization in other molluscs, including perlucin, calmodulin, dermatopontin, calponin, and chitin synthases. Respiration rate was not affected by short-term exposure to CO2. Gene expression varied greatly among individuals, and comparison between treatments indicated that C. pyramidata down-regulated a small number of genes associated with aerobic metabolism and up-regulated genes that may be associated with biomineralization, particularly collagens and C- type lectins. These results provide initial insight into the effects of short term CO2 exposure on these important planktonic open-ocean calcifiers, pairing respiration rate and the gene expression level of response, and reveal candidate genes for future ecophysiological, biomaterial and phylogenetic studies.
  • Article
    The metabolic response of thecosome pteropods from the North Atlantic and North Pacific oceans to high CO2 and low O2
    (Copernicus Publications on behalf of the European Geosciences Union, 2016-11-17) Maas, Amy E. ; Lawson, Gareth L. ; Wang, Zhaohui Aleck
    As anthropogenic activities directly and indirectly increase carbon dioxide (CO2) and decrease oxygen (O2) concentrations in the ocean system, it becomes important to understand how different populations of marine animals will respond. Water that is naturally low in pH, with a high concentration of carbon dioxide (hypercapnia) and a low concentration of oxygen, occurs at shallow depths (200–500 m) in the North Pacific Ocean, whereas similar conditions are absent throughout the upper water column in the North Atlantic. This contrasting hydrography provides a natural experiment to explore whether differences in environment cause populations of cosmopolitan pelagic calcifiers, specifically the aragonitic-shelled pteropods, to have a different physiological response when exposed to hypercapnia and low O2. Using closed-chamber end-point respiration experiments, eight species of pteropods from the two ocean basins were exposed to high CO2 ( ∼  800 µatm) while six species were also exposed to moderately low O2 (48 % saturated, or  ∼  130 µmol kg−1) and a combined treatment of low O2/high CO2. None of the species tested showed a change in metabolic rate in response to high CO2 alone. Of those species tested for an effect of O2, only Limacina retroversa from the Atlantic showed a response to the combined treatment, resulting in a reduction in metabolic rate. Our results suggest that pteropods have mechanisms for coping with short-term CO2 exposure and that there can be interactive effects between stressors on the physiology of these open ocean organisms that correlate with natural exposure to low O2 and high CO2. These are considerations that should be taken into account in projections of organismal sensitivity to future ocean conditions.
  • Article
    Daily cycle in oxygen consumption by the sea anemone Nematostella vectensis Stephenson
    (The Company of Biologists, 2016-01-15) Maas, Amy E. ; Jones, Ian T. ; Reitzel, Adam M. ; Tarrant, Ann M.
    In bilaterian animals, the circadian clock is intimately involved in regulating energetic metabolism. Although cnidarians exhibit diel behavioral rhythms including cycles in locomotor activity, tentacle extension and spawning, daily cycles in cnidarian metabolism have not been described. To explore a possible circadian metabolic cycle, we maintained the anemone Nematostella vectensis in a 12 h light/dark cycle, a reversed light cycle, or in constant darkness. Oxygen consumption rates were measured at intervals using an optical oxygen meter. Respiration rates responded to entrainment with higher rates during light periods. During a second experiment with higher temporal resolution, respiration rates peaked late in the light period. The diel pattern could be detected after six days in constant darkness. Together, our results suggest that respiration rates in Nematostella exhibit a daily cycle that may be under circadian control and that the cycle in respiration rate is not driven by the previously described nocturnal increase in locomotor activity in this species.
  • Article
    Diel metabolic patterns in a migratory oceanic copepod
    (Elsevier, 2021-10-13) Tarrant, Ann M. ; McNamara-Bordewick, Nora ; Blanco-Bercial, Leocadio ; Miccoli, Andrea ; Maas, Amy E.
    Diel vertical migration of zooplankton profoundly impacts the transport of nutrients and carbon through the water column. Despite the acknowledged importance of this active flux to ocean biogeochemistry, these contributions remain poorly constrained, in part because daily variations in metabolic rates are not considered or are modeled as simple functions of temperature. To address this uncertainty, we sampled the subtropical copepod Pleuromamma xiphias at 4- to 7-h intervals throughout the daily migration and measured rates of oxygen consumption, ammonium excretion, fecal pellet production and metabolic enzyme activity. No significant patterns were detected in rates of oxygen consumption or ammonium excretion for freshly caught animals over the diel cycle. Fecal pellet production was highest during mid-night, consistent with several hours of feeding near the surface. Surface feeding resulted in fecal pellet production at depth in the morning, providing direct evidence that active flux of particulate organic carbon occurs in this region. Electron transport system activity was highest during the afternoon, contrary to our prediction of reduced daytime metabolism. Activity of both glutamate dehydrogenase and citrate synthase increased during early night, reflecting higher capacity for excretion and aerobic respiration, respectively. Overall, these results show that activities of metabolic enzymes vary during diel vertical migration. The surprising observation of elevated afternoon enzyme activity coupled with daytime fecal pellet and ammonium production suggests that additional characterization of the daytime activity of migratory zooplankton is warranted.
  • Preprint
    Life cycle and early development of the thecosomatous pteropod Limacina retroversa in the Gulf of Maine, including the effect of elevated CO2 levels
    ( 2015-10) Thabet, Ali A. ; Maas, Amy E. ; Lawson, Gareth L. ; Tarrant, Ann M.
    Thecosome pteropods are pelagic molluscs with aragonitic shells. They are considered to be especially vulnerable among plankton to ocean acidification (OA), but to recognize changes due to anthropogenic forcing a baseline understanding of their life history is needed. In the present study, adult Limacina retroversa were collected on five cruises from multiple sites in the Gulf of Maine (between 42° 22.1’–42° 0.0’ N and 69° 42.6’–70° 15.4’ W; water depths of ca. 45–260 m) from October 2013−November 2014. They were maintained in the laboratory under continuous light at 8° C. There was evidence of year-round reproduction and an individual life span in the laboratory of 6 months. Eggs laid in captivity were observed throughout development. Hatching occurred after 3 days, the veliger stage was reached after 6−7 days, and metamorphosis to the juvenile stage was after ~ 1 month. Reproductive individuals were first observed after 3 months. Calcein staining of embryos revealed calcium storage beginning in the late gastrula stage. Staining was observed in the shell gland, shell field, mantle, and shell margin in later stages. Exposure of two batches of larvae at the gastrula stage to elevated CO2 levels (800 and 1200 ppm) resulted in significantly increased mortality in comparison with individuals raised under ambient (~400 ppm) conditions and a developmental delay in the 1200 ppm treatment compared with the ambient and 800 ppm treatments.
  • Preprint
    Assembly of a reference transcriptome for the gymnosome pteropod Clione limacina and profiling responses to short-term CO2 exposure
    ( 2017-03) Thabet, Ali A. ; Maas, Amy E. ; Saber, Samy A. ; Tarrant, Ann M.
    The gymnosome (unshelled) pteropod Clione limacina is a pelagic predatory mollusc found in polar and sub-polar regions. It has been studied for its distinctive swimming behavior and as an obligate predator on the closely related thecosome (shelled) pteropods. As concern about ocean acidification increases, it becomes useful to compare the physiological responses of closely-related calcifying and non-calcifying species to acidification. The goals of this study were thus to generate a reference transcriptome for Clione limacina, to expose individuals to CO2 for a period of 3 days, and to explore differential patterns of gene expression. Our Trinity assembly contained 300,994 transcripts of which ~26% could be annotated. In total, only 41 transcripts were differentially expressed following the CO2 treatment, consistent with a limited physiological response of this species to short-term CO2 exposure. The differentially expressed genes identified in our study were largely distinct from those identified in previous studies of thecosome pteropods, although some similar transcripts were identified, suggesting that comparison of these transcriptomes and responses may provide insight into differences in OA responses among phylogenetically and functionally distinct molluscan lineages.
  • Working Paper
    EXPORTS Measurements and Protocols for the NE Pacific Campaign
    (NASA STI Program and Woods Hole Oceanographic Institution, 2021-02) Behrenfeld, Michael J. ; Benitez-Nelson, Claudia R. ; Boss, Emmanuel S. ; Brzezinski, Mark A. ; Buck, Kristen N. ; Buesseler, Ken O. ; Burd, Adrian B. ; Carlson, Craig A. ; Cassar, Nicolas ; Cetinić, Ivona ; Close, Hilary G. ; Craig, Susanne E. ; D'Asaro, Eric A. ; Durkin, Colleen A. ; Estapa, Margaret L. ; Fassbender, Andrea ; Fox, James ; Freeman, Scott ; Gifford, Scott M. ; Gong, Weida ; Graff, Jason R. ; Gray, Deric ; Guidi, Lionel ; Halsey, Kim ; Hansell, Dennis A. ; Haëntjens, Nils ; Horner, Tristan J. ; Jenkins, Bethany D. ; Jones, Janice L. ; Karp-Boss, Lee ; Kramer, Sasha J. ; Lam, Phoebe J. ; Lee, Craig M. ; Lee, Jong-Mi ; Liu, Shuting ; Mannino, Antonio ; Maas, Amy E. ; Marchal, Olivier ; Marchetti, Adrian ; McDonnell, Andrew M. P. ; McNair, Heather ; Menden-Deuer, Susanne ; Morison, Francoise ; Nelson, Norman B. ; Nicholson, David P. ; Niebergall, Alexandria K. ; Omand, Melissa M. ; Passow, Uta ; Perry, Mary J. ; Popp, Brian N. ; Proctor, Chris ; Rafter, Patrick ; Roca-Martí, Montserrat ; Roesler, Collin S. ; Rubin, Edwina ; Rynearson, Tatiana A. ; Santoro, Alyson E. ; Siegel, David A. ; Sosik, Heidi M. ; Soto Ramos, Inia ; Stamieszkin, Karen ; Steinberg, Deborah K. ; Stephens, Brandon M. ; Thompson, Andrew F. ; Van Mooy, Benjamin A. S. ; Zhang, Xiaodong
    EXport Processes in the Ocean from Remote Sensing (EXPORTS) is a large-scale NASA-led and NSF co-funded field campaign that will provide critical information for quantifying the export and fate of upper ocean net primary production (NPP) using satellite information and state of the art technology.
  • Article
    Variations in copepod proteome and respiration rate in association with diel vertical migration and circadian cycle
    (University of Chicago Press, 2018-08-16) Maas, Amy E. ; Blanco-Bercial, Leocadio ; Lo, Ali ; Tarrant, Ann M. ; Timmins-Schiffman, Emma
    The diel vertical migration of zooplankton is a process during which individuals spend the night in surface waters and retreat to depth during the daytime, with substantial implications for carbon transport and the ecology of midwater ecosystems. The physiological consequences of this daily pattern have, however, been poorly studied beyond investigations of speed and the energetic cost of swimming. Many other processes are likely influenced, such as fuel use, energetic trade-offs, underlying diel (circadian) rhythms, and antioxidant responses. Using a new reference transcriptome, proteomic analyses were applied to compare the physiological state of a migratory copepod, Pleuromamma xiphias, immediately after arriving to the surface at night and six hours later. Oxygen consumption was monitored semi-continuously to explore underlying cyclical patterns in metabolic rate under dark-dark conditions. The proteomic analysis suggests a distinct shift in physiology that reflects migratory exertion and changes in metabolism. These proteomic analyses are supported by the respiration experiments, which show an underlying cycle in metabolic rate, with a peak at dawn. This project generates molecular tools (transcriptome and proteome) that will allow for more detailed understanding of the underlying physiological processes that influence and are influenced by diel vertical migration. Further, these studies suggest that P. xiphias is a tractable model for continuing investigations of circadian and diel vertical migration influences on plankton physiology. Previous studies did not account for this cyclic pattern of respiration and may therefore have unrepresented respiratory carbon fluxes from copepods by about 24%.
  • Article
    Seasonal controls of aragonite saturation states in the Gulf of Maine
    (John Wiley & Sons, 2017-01-22) Wang, Zhaohui Aleck ; Lawson, Gareth L. ; Pilskaln, Cynthia H. ; Maas, Amy E.
    The Gulf of Maine (GoME) is a shelf region especially vulnerable to ocean acidification (OA) due to natural conditions of low pH and aragonite saturation states (Ω-Ar). This study is the first to assess the major oceanic processes controlling seasonal variability of the carbonate system and its linkages with pteropod abundance in Wilkinson Basin in the GoME. Two years of seasonal sampling cruises suggest that water-column carbonate chemistry in the region undergoes a seasonal cycle, wherein the annual cycle of stratification-overturn, primary production, respiration-remineralization and mixing all play important roles, at distinct spatiotemporal scales. Surface production was tightly coupled with remineralization in the benthic nepheloid layer during high production seasons, which results in occasional aragonite undersaturation. From spring to summer, carbonate chemistry in the surface across Wilkinson Basin reflects a transition from a production-respiration balanced system to a net autotropic system. Mean water-column Ω-Ar and abundance of large thecosomatous pteropods show some correlation, although patchiness and discrete cohort reproductive success likely also influence their abundance. Overall, photosynthesis-respiration is the primary driving force controlling Ω-Ar variability during the spring-to-summer transition as well as over the seasonal cycle. However, calcium carbonate (CaCO3) dissolution appears to occur near bottom in fall and winter when bottom water Ω-Ar is generally low but slightly above 1. This is accompanied by a decrease in pteropod abundance that is consistent with previous CaCO3 flux trap measurements. The region might experience persistent subsurface aragonite undersaturation in 30–40 years under continued ocean acidification.
  • Article
    Shelled pteropods in peril : assessing vulnerability in a high CO2 ocean
    (Elsevier, 2017-04-09) Manno, Clara ; Bednarsek, Nina ; Tarling, Geraint A. ; Peck, Vicky L. ; Comeau, Steeve ; Adhikari, Deepak ; Bakker, Dorothee ; Bauerfeind, Eduard ; Bergan, Alexander J. ; Berning, Maria I. ; Buitenhuis, Erik T. ; Burridge, Alice K. ; Chierici, Melissa ; Flöter, Sebastian ; Fransson, Agneta ; Gardner, Jessie ; Howes, Ella L. ; Keul, Nina ; Kimoto, Katsunori ; Kohnert, Peter ; Lawson, Gareth L. ; Lischka, Silke ; Maas, Amy E. ; Mekkes, Lisette ; Oakes, Rosie L. ; Pebody, Corinne ; Peijnenburg, Katja T. C. A. ; Seifert, Miriam ; Skinner, Jennifer ; Thibodeau, Patricia S. ; Wall-Palmer, Deborah ; Ziveri, Patrizia
    The impact of anthropogenic ocean acidification (OA) on marine ecosystems is a vital concern facing marine scientists and managers of ocean resources. Euthecosomatous pteropods (holoplanktonic gastropods) represent an excellent sentinel for indicating exposure to anthropogenic OA because of the sensitivity of their aragonite shells to the OA conditions less favorable for calcification. However, an integration of observations, experiments and modelling efforts is needed to make accurate predictions of how these organisms will respond to future changes to their environment. Our understanding of the underlying organismal biology and life history is far from complete and must be improved if we are to comprehend fully the responses of these organisms to the multitude of stressors in their environment beyond OA. This review considers the present state of research and understanding of euthecosomatous pteropod biology and ecology of these organisms and considers promising new laboratory methods, advances in instrumentation (such as molecular, trace elements, stable isotopes, palaeobiology alongside autonomous sampling platforms, CT scanning and high-quality video recording) and novel field-based approaches (i.e. studies of upwelling and CO2 vent regions) that may allow us to improve our predictive capacity of their vulnerability and/or resilience. In addition to playing a critical ecological and biogeochemical role, pteropods can offer a significant value as an early-indicator of anthropogenic OA. This role as a sentinel species should be developed further to consolidate their potential use within marine environmental management policy making.
  • Article
    An operational overview of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) Northeast Pacific field deployment
    (University of California Press, 2021-07-07) Siegel, David A. ; Cetinić, Ivona ; Graff, Jason R. ; Lee, Craig M. ; Nelson, Norman B. ; Perry, Mary J. ; Soto Ramos, Inia ; Steinberg, Deborah K. ; Buesseler, Ken O. ; Hamme, Roberta C. ; Fassbender, Andrea ; Nicholson, David P. ; Omand, Melissa M. ; Robert, Marie ; Thompson, Andrew F. ; Amaral, Vinicius ; Behrenfeld, Michael J. ; Benitez-Nelson, Claudia R. ; Bisson, Kelsey ; Boss, Emmanuel S. ; Boyd, Philip ; Brzezinski, Mark A. ; Buck, Kristen N. ; Burd, Adrian B. ; Burns, Shannon ; Caprara, Salvatore ; Carlson, Craig A. ; Cassar, Nicolas ; Close, Hilary G. ; D'Asaro, Eric A. ; Durkin, Colleen A. ; Erickson, Zachary K. ; Estapa, Margaret L. ; Fields, Erik ; Fox, James ; Freeman, Scott ; Gifford, Scott M. ; Gong, Weida ; Gray, Deric ; Guidi, Lionel ; Haëntjens, Nils ; Halsey, Kim ; Huot, Yannick ; Hansell, Dennis A. ; Jenkins, Bethany D. ; Karp-Boss, Lee ; Kramer, Sasha J. ; Lam, Phoebe J. ; Lee, Jong-Mi ; Maas, Amy E. ; Marchal, Olivier ; Marchetti, Adrian ; McDonnell, Andrew M. P. ; McNair, Heather ; Menden-Deuer, Susanne ; Morison, Francoise ; Niebergall, Alexandria K. ; Passow, Uta ; Popp, Brian N. ; Potvin, Geneviève ; Resplandy, Laure ; Roca-Martí, Montserrat ; Roesler, Collin S. ; Rynearson, Tatiana A. ; Traylor, Shawnee ; Santoro, Alyson E. ; Seraphin, Kanesa ; Sosik, Heidi M. ; Stamieszkin, Karen ; Stephens, Brandon M. ; Tang, Weiyi ; Van Mooy, Benjamin ; Xiong, Yuanheng ; Zhang, Xiaodong
    The goal of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field campaign is to develop a predictive understanding of the export, fate, and carbon cycle impacts of global ocean net primary production. To accomplish this goal, observations of export flux pathways, plankton community composition, food web processes, and optical, physical, and biogeochemical (BGC) properties are needed over a range of ecosystem states. Here we introduce the first EXPORTS field deployment to Ocean Station Papa in the Northeast Pacific Ocean during summer of 2018, providing context for other papers in this special collection. The experiment was conducted with two ships: a Process Ship, focused on ecological rates, BGC fluxes, temporal changes in food web, and BGC and optical properties, that followed an instrumented Lagrangian float; and a Survey Ship that sampled BGC and optical properties in spatial patterns around the Process Ship. An array of autonomous underwater assets provided measurements over a range of spatial and temporal scales, and partnering programs and remote sensing observations provided additional observational context. The oceanographic setting was typical of late-summer conditions at Ocean Station Papa: a shallow mixed layer, strong vertical and weak horizontal gradients in hydrographic properties, sluggish sub-inertial currents, elevated macronutrient concentrations and low phytoplankton abundances. Although nutrient concentrations were consistent with previous observations, mixed layer chlorophyll was lower than typically observed, resulting in a deeper euphotic zone. Analyses of surface layer temperature and salinity found three distinct surface water types, allowing for diagnosis of whether observed changes were spatial or temporal. The 2018 EXPORTS field deployment is among the most comprehensive biological pump studies ever conducted. A second deployment to the North Atlantic Ocean occurred in spring 2021, which will be followed by focused work on data synthesis and modeling using the entire EXPORTS data set.
  • Article
    Migratory zooplankton excreta and its influence on prokaryotic communities
    (Frontiers Media, 2020-12-01) Maas, Amy E. ; Liu, Shuting ; Bolaños, Luis M. ; Widner, Brittany ; Parsons, Rachel ; Kujawinski, Elizabeth B. ; Blanco-Bercial, Leocadio ; Carlson, Craig A.
    Particulate organic matter (POM) (fecal pellets) from zooplankton has been demonstrated to be an important nutrient source for the pelagic prokaryotic community. Significantly less is known about the chemical composition of the dissolved organic matter (DOM) produced by these eukaryotes and its influence on pelagic ecosystem structure. Zooplankton migrators, which daily transport surface-derived compounds to depth, may act as important vectors of limiting nutrients for mesopelagic microbial communities. In this role, zooplankton may increase the DOM remineralization rate by heterotrophic prokaryotes through the creation of nutrient rich “hot spots” that could potentially increase niche diversity. To explore these interactions, we collected the migratory copepod Pleuromamma xiphias from the northwestern Sargasso Sea and sampled its excreta after 12–16 h of incubation. We measured bulk dissolved organic carbon (DOC), dissolved free amino acids (DFAA) via high performance liquid chromatography and dissolved targeted metabolites via quantitative mass spectrometry (UPLC-ESI-MSMS) to quantify organic zooplankton excreta production and characterize its composition. We observed production of labile DOM, including amino acids, vitamins, and nucleosides. Additionally, we harvested a portion of the excreta and subsequently used it as the growth medium for mesopelagic (200 m) bacterioplankton dilution cultures. In zooplankton excreta treatments we observed a four-fold increase in bacterioplankton cell densities that reached stationary growth phase after five days of dark incubation. Analyses of 16S rRNA gene amplicons suggested a shift from oligotrophs typical of open ocean and mesopelagic prokaryotic communities to more copiotrophic bacterial lineages in the presence of zooplankton excreta. These results support the hypothesis that zooplankton and prokaryotes are engaged in complex and indirect ecological interactions, broadening our understanding of the microbial loop.