Climate “winners and losers” are organisms or groups of organisms expected to become more or less (respectively) abundant due to climate change, when climate responses are evaluated at a broad biological scale. -Omics approaches can be used to identify the genetic traits that confer climate resilience or susceptibility and their adaptation rate. Evidence from field studies and in situ observations may be leveraged to make isolated predictions, or to test forecasts made by ecosystem models about future microbial distributions. Likewise, culture manipulations that assess physiological adaptations to different physicochemical conditions can drive predictions of microbial community responses to changing aquatic environments. Whether or not organisms can be accurately and summarily predicted as climate “winners and losers”, either generally or regionally, is an open question with key implications for our language about future impacts of climate change on aquatic microorganisms and the ecosystems they shape. In this session, we invite talks describing evidence for climate resilience or sensitivity of microbial taxa from any aquatic environment. We particularly encourage talks from participants who link empirical and theoretical approaches, or specifically address the capacity of -omics approaches to predict climate impacts on microbial communities. We hope this session will inspire precise language about predicted climate impacts on key groups of aquatic microorganisms and promote dialogue about microbial groups experiencing recent climate impacts.
Lead Organizer: Arianna Krinos, Brown University (akrinos@vt.edu)
Co-organizers:
Christine Palermo, WHOI (christine.palermo@whoi.edu)
Margaret Mars Brisbin, University of South Florida (mmarsbrisbin@usf.edu)
Presentations
04:30 PM
Quantifying microbial nutrient limitation and colimitation in the lab and field (9657)
Primary Presenter: Noelle Held, University of Southern California (nheld@usc.edu)
Nutrient availability is a fundamental control on marine microbial growth, physiology, metabolic activity, and molecular biology. Global and local environmental changes are altering nutrient availability, and it is important to develop a quantitative understanding of what this means for marine microbiological populations and communities. Traditionally, nutrient limitations are studied individually, however there is evidence that microbes can be, and often are, simultaneously limited by multiple resources (colimitation). revious work on colimitation has considered limitation as a binary property (e.g. the resource is limiting or not), and nearly everything that is known about microbial growth and physiology is form a state of strong single nutrient limitation. In this talk, I will discuss recent theoretical and experimental evidence that suggests that clonal populations of bacteria experience nutrient colimitation. I will introduce metrics of nutrient limitation and colimitation that allow for a quantitative perspective on these states, and show data indicating that heterotrophic bacteria experience colimitation for two essential resources (such as glucose and ammonium). I will also provide preliminary evidence that that there is a distinct proteomic response to colimitation, suggesting that by focusing on extreme single nutrient limitation scenarios, we are missing out on key aspects of microbial adaptation and molecular biology. Altogether these findings strengthen the case for increased consideration of nutrient colimitation in biogeochemical, biotechnology, and oceanography contexts, particularly in the process of developing molecular biomarkers of microbial growth and activity and in monitoring the effects of environmental change.
04:45 PM
USING EMPIRICAL DYNAMIC MODELING AND MICROBIAL ISOLATES TO EXPLORE CLIMATE RESPONSES IN THE DEGRADATION OF ORGANIC MATTER FROM THE DIATOM SKELETONEMA. (8861)
Primary Presenter: Bertram Ji, Duke University (bertram.ji@duke.edu)
Bertram-Chuxuan Ji1 †, Jiaqian Li1,3, Jean Philippe Gibert2, Akshaya Mohan1, Rane Parr1, Dana E. Hunt1,2,4, 1 Marine Laboratory, Duke University, Beaufort, NC, USA2 Department of Biology, Duke University, Durham, NC, USA3 School of Environmental Science & Engineering, Center for Marine Environmental Ecology, Tianjin University, China4 Civil & Environmental Engineering, Duke University, Durham, NC, USA † Presenter Bertram.ji@duke.edu; The Piver’s Island Coastal Observatory (PICO) has been sampled for more than a decade to capture environment and microbiome responses to environmental change and disturbance. While observational data can develop predictions of microbial interactions and responses to future climate conditions, we are developing a tractable synthetic microbial community to explore global change impacts on microbial activity and interactions. In order to better understand competition and cooperation in microbial degradation of organic matter (from the diatom Skeletonema), here, we develop a culture library of bacterioplankton and heterotrophic eukaryotes (Labyrinthulomycetes) from PICO seawater and a Skeletonema costatum lysate enrichment. First, we used empirical dynamic modeling (EDM) of uncultured microbial diversity (bacterioplankton, Labyrinthulomycetes, fungi) to identify potential interactions with Skeletonema. While fungi were not strong interactors in the system, bacterial taxa such as Flavobacteriaceae, Cryomorphaceae, and SAR86 clade exhibit strong inhibitory effects on Skeletonema. In contrast, the AEGEAN-169 clade demonstrates variable interactions that are context-dependent, showing both positive and negative effects. EDM results were used to target interaction-relevant bacterioplankton and Labyrinthulomycetes isolations. This culture library provides a valuable resource for exploring how these model microbes interact to degrade algal organic matter and how these interactions may change under global change, specifically warming.
05:00 PM
DIATOM POPULATION HEALTH UNDER PARASITIC INFECTION AND TEMPERATURE STRESS (9146)
Primary Presenter: Katelyn Hickman, Woods Hole Oceanographic Institution, Massachusetts Institute of Technology (jhickman@mit.edu)
Parasitic protists can spread rapidly during diatom blooms, impacting bloom dynamics and redirecting carbon flow through the marine food web. Our understanding of how these interactions vary across climates and in warming ecosystems is lacking. Specifically, the physiological response of diatoms to protist infection has not been adequately studied. Here, we investigated how a novel protistan parasite impacts pennate diatom transcription and growth under two thermal conditions. We coisolated a putative Oomycete parasite from the Scotian Shelf in October 2023 and infected a pennate diatom, Asterionella. Parasitism and temperature impacts on diatoms were assessed by growing infected and uninfected cultures at 15°C and 22°C. Infection was not evident during host exponential growth but proliferated in late exponential phase. Infection did not cause drastic host population decline yet persisted throughout the experiment. Micrographs revealed an increase in infected host cells as growth approached stationary phase, altering the morphology and behavior of individual cells. We expect a difference in host transcriptional profile between infection conditions, with downregulation of carbon fixation pathways in infected cultures. These data point to the important role of undescribed parasites as top-down controls on diatom populations, and their potential to impact bloom dynamics and marine carbon flow. This work illuminates important characteristics of a novel host-parasite system, with likely implications for diatom community responses to future climate change scenarios.
05:15 PM
CALCIFICATION IN A CHANGING OCEAN: AN EVALUATION OF METHODS FOR DETECTING CHANGES IN COCCOLITHOPHORE PIC:POC (9488)
Primary Presenter: Madison Cox, Department of Biology and Marine Biology, University of North Carolina Wilmington, USA (mbc5962@uncw.edu)
Changes to coccolithophore particulate inorganic and organic carbon ratios PIC:POC under projected ocean acidification conditions has been shown to be species and strain specific. Accurate direct measurements of coccolithophore PIC:POC is essential to understanding their role in global ocean carbon flux. In laboratory experiments, measurements of POC are obtained by acid decalcification of filters, typically using fuming HCl before CN Analysis. However, no standard operating procedure exists for decalcification or verifying complete CaCO3 dissolution. We systematically tested the efficacy of acid decalcification for several species prior to CN analysis, by examining factors such as fuming wet or dry filters, fume duration, and whether there is a difference between acid fuming or direct addition of acid to filters. Scanning electron microscopy confirmed complete decalcification regardless of time, with no significant difference in PIC:POC ratios between 30 min and 24 h. Direct addition of 0.5M HCl to wet filters also yielded complete decalcification across all species and cell densities with less variation in subsequent CN analysis. Moreover, we show that the direct addition method is sensitive enough to resolve PIC of haploid holococcolith bearing strains and can detect changes in PIC:POC in response to ion channel blockers that are crucial for calcification and pH homeostasis. We provide recommendations for obtaining accurate and precise PIC:POC ratios for a range heavily and lightly calcified 2N & N coccolithophores.
05:30 PM
DETERMINING THE PHYSIOLOGICAL RESPONSES OF THE MARINE COCCOLITHOPHORE GEPHYROCAPSA HUXLEYI TO NUTRIENT LIMITATION AND TEMPERATURE INTERACTIONS (9569)
Primary Presenter: Yutong Chen, University of Southern California (yutongc@usc.edu)
Marine coccolithophores are calcifying phytoplankton that contribute to both organic carbon fixation through photosynthesis and CaCO₃ production via calcification. Calcification releases CO₂ and the denser CaCO₃ shells enhance carbon export through the ballasting effect, so understanding coccolithophores’ role in the marine carbon cycle is essential, especially under changing environmental conditions. Previous studies have explored individual factor effects on organic and inorganic carbon production, but the interactions of multiple factors remain poorly understood. We examined the responses of the most widespread coccolithophore Gephyrocapsa huxleyi to varying temperatures and nutrient availability by measuring growth, organic carbon fixation, and calcification rates across 6 temperatures under 4 nutrient conditions (replete, N-limited, P-limited, Fe-limited). Our results show that nutrient limitation broadens the optimal temperature range for growth and shifts the balance between calcification and carbon fixation relative to nutrient-replete conditions. N-limited cells had a higher calcification-to-carbon fixation rate ratio at lower temperatures, while P-limited cells showed this at warmer temperatures. Fe limitation strongly reduced the calcification rate relative to the organic carbon fixation rate across all temperatures. These findings suggest that in a warming and increasingly nutrient-depleted ocean, coccolithophore blooms in major nutrient-limited and Fe-limited regimes may contribute very differently to oceanic CO₂ fluxes and carbon export efficiency.
05:45 PM
DO ALL CYANOBACTERIA WIN? USING PALEOLIMNOLOGICAL APPROACHES TO DISENTANGLE THE LONG-TERM NUTRIENT AND CLIMATE DRIVERS OF HARMFUL CYANOBACTERIA BLOOMS (9211)
Primary Presenter: Avery Lamb, University of Maine (avery.lamb@maine.edu)
Paleo, contemporary, and modeling-based limnological studies have documented and forecasted global increases in harmful cyanobacterial blooms, suggesting that cyanobacteria will be climate change “winners”. Characterizing the strength of nutrients and temperature as drivers of cyanobacterial blooms is complicated by differences in species’ responses to environmental change and insufficiently long time series. We employ a multiproxy paleolimnological approach using photosynthetic pigments and environmental DNA (eDNA) metabarcoding to investigate cyanobacteria in Maine lakes that span different climate zones and trophic states. These sediment reconstructions can be used to disentangle the effects of nutrients, temperature, and their interactions on cyanobacterial communities in Maine lakes over the past 125 years. Specifically, we address: 1. Are nutrients or temperature a better predictor of cyanobacterial abundance and diversity in Maine’s temperate lakes? 2. Do nutrients and temperature interact to affect cyanobacterial abundance and diversity, and if so, how? Results will help to further characterize climate “winners”, determine any timing/direction/magnitude of algal community change, and better clarify whether Maine lake ecosystems are moving outside their natural variability. Pairing paleolimnological proxies, including eDNA approaches, over long timescales contributes to a more precise understanding of climate change effects on cyanobacterial taxa and underscores the importance of paleolimnological records in assessing effects of climate change on lake systems.
SS19B - Climate “winners and losers”: predicting and assessing microbial responses to climate change
Description
Time: 4:30 PM
Date: 29/3/2025
Room: W205CD