Ciliate micrograzer dynamics of the New England Shelf

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2017Protists play important roles in grazing and nutrient recycling, but quantifying these roles has been hindered by difficulties in collecting, culturing, and observing these often-delicate cells. During long-term deployments at theMartha’s Vineyard Coastal Observatory (MVCO) (Massachusetts, USA), Imaging FlowCytobot (IFCB) made it possible to study live cells in situ without the need to culture or preserve. IFCB records images of cells with chlorophyll fluorescence above a trigger threshold, so taxonomically resolved analysis of protists is limited to mixotrophs and herbivores, which have eaten recently. To overcome this limitation, I coupled a broad-application ‘live cell’ fluorescent stain with a modified IFCB so that protists which do not contain chlorophyll (such as consumers of unpigmented bacteria and other heterotrophs) can also be recorded. Staining IFCB (IFCB-S) revealed higher abundances of grazers than the original IFCB, as well as some cell types not previously detected. To analyze a 10-year time series of herbivorous ciliates at MVCO and address broad patterns of seasonality of major ciliate classes and their components, I employed a statistical model that estimates a seasonal density pattern and simultaneously accounts for and separates any annual-scale effects. I describe the seasonality of three functional groups: a phototrophic ciliate, a mixotroph, and a group of strict heterotrophs, and comment on potential drivers of these patterns. DNA sequencing has also contributed to the study of protist communities, providing new insight into diversity, predator-prey interactions, and discrepancies between morphologically defined species and genotype. To explore how well IFCB images can be used to detect seasonal community change of the class Spirotrichea, an important and numerous group, I used high-throughput sequencing (HTS), which does not discriminate between chlorophyll-containing cells and the rest of the community. I report on species and genera of ciliates for which morphotype and genotype displayed high congruency. In comparing how well temporal aspects of genotypes and morphotypes correspond, I found that HTS was critical to detect and identify certain ciliates occupying a niche associated with warmer temperatures. I further showed that when these types of analyses are combined with IFCB results, they can provide hypotheses about food preferences.This research was supported in part by NSF (grants OCE-1130140, OCE-1434440), NASA (grants NNX11AF07G and NNX13AC98G), the Gordon and BettyMoore Foundation (grants 934 and 2649), theWoods Hole Oceanographic Institution’s Innovative Technology Program, student awards from the WHOI Ocean Ventures Fund and Hill Foundation Fund

Microzooplankton community structure investigated with imaging flow cytometry and automated live-cell staining

© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Ecology Progress Series 550 (2016): 65-81, doi:10.3354/meps11687.Protozoa play important roles in grazing and nutrient recycling, but quantifying these roles has been hindered by difficulties in collecting, culturing, and observing these often-delicate cells. During long-term deployments at the Martha’s Vineyard Coastal Observatory (Massachusetts, USA), Imaging FlowCytobot (IFCB) has been shown to be useful for studying live cells in situ without the need to culture or preserve. IFCB records images of cells with chlorophyll fluorescence above a trigger threshold, so to date taxonomically resolved analysis of protozoa has presumably been limited to mixotrophs and herbivores which have eaten recently. To overcome this limitation, we have coupled a broad-application ‘live cell’ fluorescent stain with a modified IFCB so that protozoa which do not contain chlorophyll (such as consumers of unpigmented bacteria and other heterotrophs) can also be recorded. Staining IFCB (IFCB-S) revealed higher abundances of grazers than the original IFCB, as well as some cell types not previously detected. Feeding habits of certain morphotypes could be inferred from their fluorescence properties: grazers with stain fluorescence but without chlorophyll cannot be mixotrophs, but could be either starving or feeding on heterotrophs. Comparisons between cell counts for IFCB-S and manual light microscopy of Lugol’s stained samples showed consistently similar or higher counts from IFCB-S. We show how automated classification through the extraction of image features and application of a machine-learning algorithm can be used to evaluate the large high-resolution data sets collected by IFCBs; the results reveal varying seasonal patterns in abundance among groups of protists.This research was supported in part by NSF (grants OCE-1130140, OCE-1434440), NASA (grants NNX11AF07G and NNX13AC98G), the Gordon and Betty Moore Foundation (grants 934 and 2649), and the Woods Hole Oceanographic Institution’s Innovative Technology Program

Sixty years of Sverdrup : a retrospective of progress in the study of phytoplankton blooms

Author Posting. © The Oceanography Society, 2014. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 27, no. 1 (2014): 222–235, doi:10.5670/oceanog.2014.26.One of the most dramatic large-scale features in the ocean is the seasonal greening of the North Atlantic in spring and summer due to the accumulation of phytoplankton biomass in the surface layer. In 1953, Harald Ulrik Sverdrup hypothesized a now canonical mechanism for the development and timing of phytoplankton blooms in the North Atlantic. Over the next 60 years, Sverdrup's Critical Depth Hypothesis spurred progress in understanding of bloom dynamics and offered a valuable theoretical framework on which to build. In reviewing 60 years of literature, the authors trace the development of modern bloom initiation hypotheses, highlighting three case studies that illuminate the complexity, including both catalysts and impediments, of scientific progress in the wake of Sverdrup's hypothesis. Most notably, these cases demonstrate that the evolution of our understanding of phytoplankton blooms was paced by access not only to technology but also to concurrent insights from several disciplines. This exploration of the trajectories and successes in bloom studies highlights the need for expanding interdisciplinary collaborations to address the complexity of phytoplankton bloom dynamics

High Grazing Rates on Cryptophyte Algae in Chesapeake Bay

Cryptophyte algae are globally distributed photosynthetic flagellates found in freshwater, estuarine, and neritic ecosystems. While cryptophytes can be highly abundant and are consumed by a wide variety of protistan predators, few studies have sought to quantify in situ grazing rates on their populations. Here we show that autumnal grazing rates on in situ communities of cryptophyte algae in Chesapeake Bay are high throughout the system, while growth rates, particularly in the lower bay, were low. Analysis of the genetic diversity of cryptophyte populations within dilution experiments suggests that microzooplankton may be selectively grazing the fastest-growing members of the population, which were generally Teleaulax spp. We also demonstrate that potential grazing rates of ciliates and dinoflagellates on fluorescently labeled (FL) Rhodomonas salina, Storeatula major, and Teleaulax amphioxeia can be high (up to 149 prey predator−1 d−1), and that a Gyrodinium sp. and Mesodinium rubrum could be selective grazers. Potential grazing was highest for heterotrophic dinoflagellates, but due to its abundance, M. rubrum also had a high overall impact. This study reveals that cryptophyte algae in Chesapeake Bay can experience extremely high grazing pressure from phagotrophic protists, and that this grazing likely shapes their community diversity

Recommendations for advancing mixoplankton research through empirical-model integration

Protist plankton can be divided into three main groups: phytoplankton, zooplankton, and mixoplankton. In situ methods for studying phytoplankton and zooplankton are relatively straightforward since they generally target chlorophyll/photosynthesis or grazing activity, while the integration of both processes within a single cell makes mixoplankton inherently challenging to study. As a result, we understand less about mixoplankton physiology and their role in food webs, biogeochemical cycling, and ecosystems compared to phytoplankton and zooplankton. In this paper, we posit that by merging conventional techniques, such as microscopy and physiological data, with innovative methods like in situ single-cell sorting and omics datasets, in conjunction with a diverse array of modeling approaches ranging from single-cell modeling to comprehensive Earth system models, we can propel mixoplankton research into the forefront of aquatic ecology. We present eight crucial research questions pertaining to mixoplankton and mixotrophy, and briefly outline a combination of existing methods and models that can be used to address each question. Our intent is to encourage more interdisciplinary research on mixoplankton, thereby expanding the scope of data acquisition and knowledge accumulation for this understudied yet critical component of aquatic ecosystems

Dressings and securements for the prevention of peripheral intravenous catheter failure in adults (SAVE): a pragmatic, randomised controlled, superiority trial

Background: Two billion peripheral intravenous catheters (PIVCs) are used globally each year, but optimal dressing and securement methods are not well established. We aimed to compare the efficacy and costs of three alternative approaches to standard non-bordered polyurethane dressings. Methods: We did a pragmatic, randomised controlled, parallel-group superiority trial at two hospitals in Queensland, Australia. Eligible patients were aged 18 years or older and required PIVC insertion for clinical treatment, which was expected to be required for longer than 24 h. Patients were randomly assigned (1:1:1:1) via a centralised web-based randomisation service using random block sizes, stratified by hospital, to receive tissue adhesive with polyurethane dressing, bordered polyurethane dressing, a securement device with polyurethane dressing, or polyurethane dressing (control). Randomisation was concealed before allocation. Patients, clinicians, and research staff were not masked because of the nature of the intervention, but infections were adjudicated by a physician who was masked to treatment allocation. The primary outcome was all-cause PIVC failure (as a composite of complete dislodgement, occlusion, phlebitis, and infection [primary bloodstream infection or local infection]). Analysis was by modified intention to treat. This trial is registered with the Australian New Zealand Clinical Trials Registry, number ACTRN12611000769987. Findings: Between March 18, 2013, and Sept 9, 2014, we randomly assigned 1807 patients to receive tissue adhesive with polyurethane (n=446), bordered polyurethane (n=454), securement device with polyurethane (n=453), or polyurethane (n=454); 1697 patients comprised the modified intention-to-treat population. 163 (38%) of 427 patients in the tissue adhesive with polyurethane group (absolute risk difference −4·5% [95% CI −11·1 to 2·1%], p=0·19), 169 (40%) of 423 of patients in the bordered polyurethane group (–2·7% [–9·3 to 3·9%] p=0·44), 176 (41%) of 425 patients in the securement device with poplyurethane group (–1·2% [–7·9% to 5·4%], p=0·73), and 180 (43%) of 422 patients in the polyurethane group had PIVC failure. 17 patients in the tissue adhesive with polyurethane group, two patients in the bordered polyurethane group, eight patients in the securement device with polyurethane group, and seven patients in the polyurethane group had skin adverse events. Total costs of the trial interventions did not differ significantly between groups. Interpretation: Current dressing and securement methods are commonly associated with PIVC failure and poor durability, with simultaneous use of multiple products commonly required. Cost is currently the main factor that determines product choice. Innovations to achieve effective, durable dressings and securements, and randomised controlled trials assessing their effectiveness are urgently needed

2012 labeled IFCB images

This zipped content contains Annotated Plankton Images from one year and is part of the WHOI-Plankton Collection that spans multiple years. Click on the WHOI-Plankton link below to view all items (other years) in this collection

2007 labeled IFCB images

This zipped content contains Annotated Plankton Images from one year and is part of the WHOI-Plankton Collection that spans multiple years. Click on the WHOI-Plankton link below to view all items (other years) in this collection

2006 labeled IFCB images

This zipped content contains Annotated Plankton Images from one year and is part of the WHOI-Plankton Collection that spans multiple years. Click on the WHOI-Plankton link below to view all items (other years) in this collection

2014 labeled IFCB images

This zipped content contains Annotated Plankton Images from one year and is part of the WHOI-Plankton Collection that spans multiple years. Click on the WHOI-Plankton link below to view all items (other years) in this collection