News, Events and Happenings
PhD student Sarah Loftus attended the 2019 ASLO Aquatic Sciences Meeting in San Juan, Puerto Rico. ASLO’s mission is to “foster a diverse, international scientific community that creates, integrates and communicates knowledge across the full spectrum of aquatic sciences, advances public awareness and education about aquatic resources and research, and promotes scientific stewardship of aquatic resources for the public interest.” Loftus presented her PhD research in the special session on Phytoplankton-Bacteria Interactions, with a talk titled “Effects of DOC pools on phytoplankton growth and bacteria communities.” She was also selected to participate in ASLO’s Journalist for a Day program, which involves writing an article about research presented at the conference. Articles from this program will be published in the August issue of the Limnology & Oceanography Bulletin.
Subsurface chlorophyll maximum layers (SCMLs) are nearly ubiquitous in stratified water columns and exist at horizontal scales ranging from the submesoscale to the extent of oligotrophic gyres. These layers of heightened chlorophyll and/or phytoplankton concentrations are generally thought to be a consequence of a balance between light energy from above and a limiting nutrient flux from below, typically nitrate (NO3). Here we present multiple lines of evidence demonstrating that iron (Fe) limits or with light colimits phytoplankton communities in SCMLs along a primary productivity gradient from coastal to oligotrophic offshore waters in the southern California Current ecosystem. SCML phytoplankton responded markedly to added Fe or Fe/light in experimental incubations and transcripts of diatom and picoeukaryote Fe stress genes were strikingly abundant in SCML metatranscriptomes. Using a biogeochemical proxy with data from a 40-y time series, we find that diatoms growing in California Current SCMLs are persistently Fe deficient during the spring and summer growing season. We also find that the spatial extent of Fe deficiency within California Current SCMLs has significantly increased over the last 25 y in line with a regional climate index. Finally, we show that diatom Fe deficiency may be common in the subsurface of major upwelling zones worldwide. Our results have important implications for our understanding of the biogeochemical consequences of marine SCML formation and maintenance.
Salmon
id feeds can be formulated with high quality microalgae to maintain sustainability in the aquaculture industry. But, the suitability of different microalgae species as potential feed ingredients needs to be documented to enable ready acceptance by the farming industry. The aim of the present study is to investigate the potential of the microalga Scenedesmus sp. as a major ingredient in low fishmeal feeds of Atlantic salmon. Three feeds were formulated with Scenedesmus/fishmeal, at inclusion levels of 0/10, 10/5 and 20/2.5% (CT, SCE 10 and SCE 20, respectively); to investigate the effect of the ingredient on the weight gain, growth rate, feed conversion ratio, nutrient retention and chemical composition and nutrient digestibility in Atlantic salmon. In addition, the physical characteristics of feeds were investigated to assess the impact of the alga-incorporation on the quality of the feeds. Fish (initial average weight of 229 g) in 6 replicate tanks were fed one of the experimental feeds for 65 days. The results showed that fish fed SCE 20 had significantly lower weight gain, specific growth rate, thermal growth coefficient and feed conversion ratio than the CT group, which did not receive the microalga. Furthermore, the condition factor and protein efficiency ratio of the microalga-fed groups were lower than the CT group. Hepatosomatic and viscerosomatic indices of the groups did not differ significantly. Ash and protein content of whole fish fed SCE 20 were significantly higher, but dry matter, lipid, and energy of this group were lower than either the CT or the SCE 10 group. Retention of lipid and energy of all groups differed significantly, while that of protein was significantly different in the Scenedesmus-fed groups. Compared to the CT feed, digestibility of dry matter, protein, and energy in the algal feeds were significantly reduced. The highest fat leakage observed for the feed devoid of the alga and the hardness of the SCE 20 feed points to the better physical stability of the alga-containing feeds. Higher contents of n-3 fatty acids and PUFAs were found in the whole body of fish fed SCE 10. In conclusion, Scenedesmus sp. can be incorporated in low fishmeal diets for Atlantic salmon, at inclusion levels below 10%.
The Second State of the Carbon Cycle Report (SOCCR2) was released by the U.S. Global Change Research Program (USGCRP) via https://carbon2018.globalchange.gov on Friday, November 23, 2018. With over 200 contributing experts including PI Johnson, this interagency Highly Influential Scientific Assessment was led by the Carbon Cycle Interagency Working Group (CCIWG) and U.S. Carbon Cycle Science Program under USGCRP auspices. SOCCR2 is an authoritative decadal assessment of carbon cycle science across North America, developed by over 200 experts from the U.S., Canadian and Mexican governments, national laboratories, universities, private sector, and research institutions. SOCCR2 is a Sustained Assessment Product of the U.S. Global Change Research Program.
USGCRP, 2018: Second State of the Carbon Cycle Report (SOCCR2): A Sustained Assessment Report. [Cavallaro, N., G. Shrestha, R. Birdsey, M. A. Mayes, R. G. Najjar, S. C. Reed, P. Romero-Lankao, and Z. Zhu (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, 878 pp., https://doi.org/10.7930/SOCCR2.2018.
Peggy Mullin, visiting UNC student who is working with the Johnson Lab on modeling outdoor large scale algae growth, successfully defended her undergraduate honor’s thesis. The thesis, “Development of a laboratory metric to predict large scale algae productivity” uses small scale, rapid laboratory measurements in conjunction with environmental data and mathematical modeling to predict outdoor algae production. This work is an important step towards the broader implementation of the use of marine algae for the sustainable production of food, feed and fuel. Congratulations Peggy!
PhD graduate student Sarah Loftus was the top prize winner of the biology section at the Algae Biomass Summit. The Summit is the algae industry’s premier event, where leading producers of algae products go to network with industry suppliers and technology providers, where project developers converse with utility executives, and where researchers and technology developers rub elbows with venture capitalists. Ms. Loftus presented on recycled water use for industrial applications of algae. Congratulations!
Recycled algae cultivation water steadily accumulates dissolved organic carbon
Summary: Reusing cultivation water is required for economical and environmentally sustainable production of algal biofuels and co-products. However, recycled water contains compounds released by algae that can affect their growth. Previous studies have measured dissolved organic carbon (DOC) accumulation in recycled water, yet none have determined if recycled water affects DOC release or if DOC concentrations predict growth success in recycled water. Here, lab-scale water recycling experiments showed that different algae responded uniquely to recycled growth medium, but growth responses did not correlate with DOC concentration. DOC release rates were lower on average in recycled medium, although there was no trend of decreasing release rates across multiple water reuses. Accumulated DOC in recycled water was also not degraded, so at least a portion may be recalcitrant (i.e., non-biodegradable). Results can inform algae selection and cultivation decisions to maximize both the quality of recycled water and the carbon retained in algae biomass.
There is a growing awareness of the ecological and biogeochemical importance of fungi in coastal marine systems, while highly diverse fungi have been discovered in these marine systems, still little is known about their seasonality and associated drivers in coastal waters. Here, we examined fungal communities over three years of weekly samples at a dynamic, temperate coastal site (Piver’s Island Coastal Observatory (PICO), Beaufort NC USA). Fungal 18S rRNA gene abundance, OTU richness and Shannon’s diversity exhibited prominent seasonality. Fungi 18S rRNA gene copies peak in abundance during the summer and fall, with positive correlations with chlorophyll a, SiO4 and oxygen saturation. Diversity (measured using Internal Transcribed Spacer: ITS libraries) was highest during winter and lowest during summer; it was linked to temperature, pH, chlorophyll a, insolation, salinity, and DIC. Fungal community ITS libraries were dominated throughout the year by Ascomycota with contributions from Basidiomycota, Chytridiomycota and Mucoromycotina, with seasonal patterns linked to water temperature, light, and the carbonate system. Network analysis revealed that while co-occurrence and exclusion existed within fungal network, exclusion dominated the fungi and phytoplankton network, in contrast with reported pathogenic and nutritional interactions between marine phytoplankton and fungi. Compared with the seasonality of bacterial community in the same samples, the timing, extent and associated environmental variables for fungi community are unique. These results highlighted the fungal seasonal dynamics in coastal water and improve our understanding of the ecology of planktonic fungi.ImportanceCoastal fungal dynamics were long assumed to be due to terrestrial inputs; here, a high-resolution time-series, reveals strong, repeating annual patterns linked to in situ environmental conditions, arguing for a resident coastal fungal community shaped by environmental factors. These seasonal patterns do, however, differ from those observed in the bacterioplankton at the same site: e.g., fungal diversity peaks in winter whereas bacterial diversity maxima occur in the spring and fall. While dynamics of these communities are linked to water temperature and insolation, fungi are also influenced by the carbonate system (pH and DIC). As both fungi and heterotrophic bacteria are thought to be key organic material metabolizers, differences in their environmental drivers may offer clues as to which group dominates secondary production at this dynamic site. Overall, this study suggests the unique ecological roles of mycoplankton and their potentially broad niche complementarities to other microbial groups in the coastal ocean.
The unicellular Labyrinthulomycete protists have long been considered to play a significant role in ocean carbon cycling. However, their distribution and biogeochemical function remain poorly understood. We present a large‐scale study of their spatiotemporal abundance and diversity in the coastal waters of Bohai Sea using flow cytometry and high‐throughput sequencing. These protists display niche preferences and episodic higher biomass than that of bacterioplankton with much phylogenetic diversity (> 4000 OTUs) ever reported. They were ubiquitous with a typical abundance range of 100–1000 cells ml−1 and biomass range of 0.06–574.59 μg C L−1. The observed spatiotemporal abundance variations support the current ‘left‐over scavengers’ nutritional model and highlight these protists as a significant component of the marine microbial loop. The higher average abundance and phylogenetic diversity in the nearshore compared with those in the offshore reveal their predominant role in the terrigenous matter decomposition. Furthermore, the differential relationship of the protist genera to environmental conditions together with their co‐occurrence network suggests their unique substrate preferences and niche partitioning. With few subnetworks and possible keystone species, their network topology indicates community resilience and high connectance level of few operational taxonomic units (OTUs). We demonstrate the significant contribution of these protists to the secondary production and nutrient cycling in the coastal waters. As secondary producers, their role will become more important with increasingly coastal eutrophication.
The annual Duke Marine Lab Open House had exceptional attendance this year as it coincided with alumni weekend and a visit from Duke University President Vincent Price. Johnson Lab members hosted two stations at Open House on the sunny July afternoon. One station showcased the open raceway ponds, a feature of the DOE-funded large-scale algae cultivation project. Visitors were even invited to enter a rubber duck race, cheering for their small plastic toy as it rounded the bend of the raceway pond. Another station taught visitors about the diversity and lifestyles of the algae we research in lab. President Price even peered into a microscope to watch Tetraselmis cells whip around using their tail-like flagella. More photos from the weekend can be viewed on Duke’s Nicholas School news page.
First year PhD student Laura Givens receive an IBIEM Graduate Trainee award. IBIEM (Integrative Bioinformatics for Investigating and Engineering Microbiomes) is an interdisciplinary graduate training program between Duke University and North Carolina A&T State University which brings together scientists from various fields with an interest in microbiome research. IBIEM trainees participate in the Boot Camp, Collaborative Science Practica, and an Interactive seminar Course and other informal interactions to be exposed to multiple levels of interdisciplinary experiences to enable them to address issues of quantitative biology in the context of varying industrial sectors. Congratulations Laura!
The Pivers Island Coastal Observatory (PICO) weekly (and sometimes more) time-series turned eight today. Started in 2010 as an undergraduate independent student project focusing on ocean acidification, the coastal time-series has matured into a long term coastal sentinel, observing seasonal, yearly and interannual changes in the physics, chemistry and biology of the coastal marine environment with weekly sampling. Additional offshore longitudinal sampling (PICO-LOVE) provides spatial context. Data is available through BCO-DMO. Happy Birthday and hooray for PICO!
Volunteers from over a dozen regional institutions welcomed over 160 middle school girls to the event this Saturday. GEST’s mission is to provide hands-on STEM opportunities and female STEM role models to girls in eastern NC. PhD students Courtney Swink and Sarah Loftus were on the GEST planning team, which organized this collaborative outreach event in which girls rotated through different STEM activities and a panel discussion. Courtney Swink led one of the twelve STEM activities. She explained the concept of algae cultivation for biofuels and other products, had girls set up their own algae cultures, and described the outdoor cultivation ponds with a tour.
Ph.D. student Courtney traveled to Washington, D.C. to volunteer at the USA Science & Engineering Festival on Saturday, April 6th. This free 2 day event was held at the Walter E. Washington Convention Center and had over 3,000 exhibitors and 350,000 visitors! The mission of this festival is to stimulate interest in the nation’s youth in science, technology, engineering and math (STEM) related fields.
As a student member of ASLO (Association for the Sciences of Limnology and Oceanography), Courtney participated as a volunteer for the CASS (Consortium of Aquatic Science Societies) booth which shared activities and information about aquatic sciences for all age levels. Students were taught about the different morphologic adaptations of all types of plankton and asked to build their own plankton models to “race” to see who’s creation would sink the slowest. Students also learned about turbidity and how to use a secchi disk. The CASS booth alone interacted with ~3,300 young students, parents and teachers! Many students left the booth with a better understanding of what plankton look like and why they are important in the environment.
Second year PhD student Courtney Swink was awarded a NSF Graduate Research Fellowship Program Fellowship. Her selection as an NSF Graduate Fellowship awardee is a significant accomplishment and was based on her demonstrated potential to contribute to strengthening the vitality of the U.S. science and engineering enterprise. Courtney is researching microbial communities associated with large, industrial scale marine microalgae ponds.
Bioenergy Carbon Capture and Storage (BECCS) has been proposed to reduce atmospheric CO2 concentrations, but concerns remain about competition for arable land and freshwater. The synergistic integration of algae production, which does not require arable land or freshwater, with BECCS (called “ABECCS”) can reduce CO2 emissions without competing with agriculture. This study presents a techno-economic and life-cycle assessment for co-locating a 121-ha algae facility with a 2,680-ha eucalyptus forest for BECCS. The eucalyptus biomass fuels combined heat and power generation (CHP) with subsequent amine based carbon capture and storage (CCS). A portion of the captured CO2 is used for growing algae and the remainder is sequestered. Biomass combustion supplies CO2, heat, and electricity, thus increasing the range of sites suitable for algae cultivation. Economic, energetic, and environmental impacts are considered. The system yields as much protein as soybeans while generating 61.5 TJ of electricity and sequestering 29,600 t of CO2 per year. More energy is generated than consumed and the freshwater footprint is roughly equal to that for soybeans. Financial break-even is achieved for product value combinations ranging from 1) algal biomass sold for $1,780/t without a carbon credit to 2) algal biomass sold for $100/t with a carbon credit of $396/t. Sensitivity analysis shows significant reductions to the cost of carbon sequestration are possible. The ABECCS system represents a unique technology for negative emissions without reducing protein production or increasing water demand, and should therefore be included in the suite of technologies being considered to address global sustainability.
Happy holidays from the Johnson Lab! Hope plankton brings you something good this year. (Plankton converts to coal in ~300 million years.)
Johnson announced a Sustaining Fellow of the Association for the Sciences of Limnology and Oceanography (ASLO). ASLO Sustaining Fellows are recognized as having sustained excellence in their contributions to ASLO and the aquatic sciences.
Microbial science at Duke is taking a major step forward with the launch of the Duke Microbiome Center (DMC), which is intended to address growing scientific interest in the roles microbial communities play in human health, the environment and biotechnology. The new center expands on the mission of the five-year-old Duke Center for Genomics of Microbial Systems (GeMS) by going beyond genomic analysis of microorganisms. See related article at Duke Today.
Marine aggregates play a critical role in the biological pump, both as a dominant component of carbon flux and as hotspots for organic matter remineralization by microbial communities. In this study, we used laboratory experiments to investigate how aggregate thin layers, such as those commonly found in the coastal ocean, affect the distribution of bacteria and their activity. Diatom aggregates were added to a stratified water column, forming layers within which both microbial concentration and extracellular enzyme activity were substantially increased relative to background levels. Importantly, this enhancement of bacterial concentration and activity persisted long after the marine snow aggregates settled through the tank—that is, 10 times longer than the duration of the aggregate layer at the density interface. Thus, these small-scale microbial interactions within aggregate layers leave behind considerable “carbon processing footprints” in the water column that may affect biogeochemical cycles at much larger temporal and spatial scales.
Prochlorococcus, the smallest and most abundant phytoplankter in the ocean, is highly sensitive to hydrogen peroxide (HOOH), and co-occurring heterotrophs such as Alteromonas facilitate the growth of Prochlorococcus by scavenging HOOH. Temperature is also a major influence on Prochlorococcus abundance and distribution in the ocean, and studies in other photosynthetic organisms have shown that HOOH and temperature extremes can act together as synergistic stressors. To address potential synergistic effects of temperature and HOOH on Prochlorococcus growth, high- and low-temperature adapted representative strains were cultured at ecologically relevant concentrations under a range of HOOH concentrations and temperatures. Higher concentrations of HOOH severely diminished the permissive temperature range for growth of both Prochlorococcus strains. At the permissive temperatures, the growth rates of both Prochlorococcus strains decreased as a function of HOOH, and cold temperature increased susceptibility of photosystem II to HOOH-mediated damage. Serving as a proxy for the natural community, co-cultured heterotrophic bacteria increased the Prochlorococcus growth rate under these temperatures, and expanded the permissive range of temperature for growth. These studies indicate that in the ocean, the cross-protective function of the microbial community may confer a fitness increase for Prochlorococcus at its temperature extremes, especially near the ocean surface where oxidative stress is highest. This interaction may play a substantial role in defining the realized thermal niche and habitat range of Prochlorococcus with respect to latitude.
Associate Professor Zackary Johnson presented on the trends and patterns of coastal and ocean acidification in coastal North Carolina at the Southeastern Ocean and Coastal Acidification Network NC Stakeholder meeting. The presentation was titled, ‘Variability of the carbonate system (including acidity) in a dynamic coastal NC system’. Ocean and coastal acidification are changing the chemistry of seawater with potential effects for economically important marine life and coastal communities. Runoff pollution, land-use change, and a vibrant shellfish industry render North Carolina among the most socioeconomically vulnerable states to future acidification impacts, but an understanding of these changes can provide the tools necessary for coastal industries and ecosystems to mitigate and adapt to these changes.
Dr. Zhiying “Bruce” Lu joined the Johnson Lab as a postdoctoral research associate and funded by the China Research Council. Dr. Lu’s research focuses on using recycled medium (used water) for growing microalgae as a source of food and fuel. At the Johnson Lab he will work as part of the MAGIC team, to cultivate algae at large scale for sustainable food and fuel production.
Five large scale ponds, three ~1000L and two ~4500L , have been installed and are growing microalgae as part of the Marine Algae Industrialization Consortium (MAGIC). The ponds will grow ~10 strains of microalgae to compare their growth characteristics, algae biochemical signatures, and product suitability across a range of potential applications.
The North Pacific Ocean (between approximately 0°N and 50°N) contains the largest continuous ecosystem on Earth. This region plays a vital role in the cycling of globally important nutrients as well as carbon. Although the microbial communities in this region have been assessed, the dynamics of viruses (abundances and production rates) remains understudied. To address this gap, scientific cruises during the winter and summer seasons (2013) covered the North Pacific basin to determine factors that may drive virus abundances and production rates. Along with information on virus particle abundance and production, we collected a spectrum of oceanographic metrics as well as information on microbial diversity. The data suggest that both biotic and abiotic factors affect the distribution of virus particles. Factors influencing virus dynamics did not vary greatly between seasons, although the abundance of viruses was almost an order of magnitude greater in the summer. When considered in the context of microbial community structure, our observations suggest that members of the bacterial phyla Proteobacteria, Planctomycetes, and Bacteroidetes were correlated to both virus abundances and virus production rates: these phyla have been shown to be enriched in particle associated communities. The findings suggest that environmental factors influence virus community functions (e.g., virion particle degradation) and that particle-associated communities may be important drivers of virus activity.
Scientists rejoice!
In this study, we investigated the environmental impacts of scallop culture on two coastal estuaries adjacent the Bohai Sea including developing a quantitative PCR assay to assess the abundance of the bacterial pathogens Escherichia coli and Vibrio parahaemolyticus. Scallop culture resulted in a significant reduction of nitrogen, Chlorophyll a, and phosphorous levels in seawater during summer. The abundance of bacteria including V. parahaemolyticus varied significantly across estuaries and breeding seasons and was influenced by nitrate as well as nutrient ratios (Si/DIN, N/P). Bacterioplankton diversity varied across the two estuaries and seasons, and was dominated by Proteobacteria, Cyanobacteria, Actinobacteria, Bacteroidetes. Overall, this study suggests a significant influence of scallop culture on the ecology of adjacent estuaries and offers a sensitive tool for monitoring scallop contamination.
In spite of challenging weather, the Duke Marine Lab hosted about 500 visitors for it’s 2017 Open House extravaganza. The Marine Microbe Group presented 3 exhibits including examples of ocean acidification, phytoplankton/algae in the coastal ocean and a demonstrating the large scale of production of microalgae for food and fuel. Lots of good questions and participation and looking forward to showing off even more next year.
The Duke Marine Lab joined the Beaufort NC July 4th parade to promote it’s upcoming open house. Lead by REU student Ford Fishman, the R/V Richard Barber was paraded through the streets to cheering residents and visitors alike!
ZIJ presented on the diversity and activity of Prochlorococcus at the OCB2017 summer meeting at WHOI in Woods Hole, MA. The presentation, “Ribosomal RNA and DNA (23S) of Prochlorococcus reveal variable activity and abundance relationships across taxonomic ranks” was based on a study with lead author and former student Alyse Larkin, now at UCI. The work highlights how the fine taxonomic scale of Prochlorococcus has unexpected patterns in activity and suggests population ecological differentiation, regulation and biogeochemistry that are still poorly understood for this keystone microbe.
Abstract: Phytoplankton communities in oligotrophic temperate and tropical oceans are numerically dominated by Prochlorococcus sp., a genetically diverse and biogeochemically important marine cyanobacterium. The phylogenetic clades and subgroups of Prochlorococcus exhibit niche partitioning based on light, temperature and other resources in the ocean, but it is unknown how these clades/ecotypes differ in their in situ activity across large spatiotemporal environmental gradients. Here using relative 23S rRNA:rDNA ratios as a proxy for specific activity, we examine high light (HL) adapted Prochlorococcus across environmental gradients in the surface North Pacific Ocean to (1) determine the coupling between activity and abundance across taxonomic ranks and (2) examine the specific activity among closely related operational taxonomic units (OTUs). We show that activity and abundance are highly correlated for all 97% similarity OTUs of Prochlorococcus across all sites in the surface ocean. However, finer molecular scale resolution (oligotyping) shows significantly more variability in rRNA:rDNA ratios and reveals differing trends among closely related OTUs including different patterns between high and low abundance oligotypes. These results suggest that HL Prochlorococcus populations respond quickly to (a)biotic changes and the mechanisms that lead to uncoupling between activity and abundance (e.g. density dependent processes) are less important for this community at course molecule scales. These findings also suggest that relative Prochlorococcus population abundances at a given location can serve as a proxy for activity, providing an important tool for ecosystem model development. However, uncoupling at fine molecular scales suggests population differentiation and mechanisms of regulation that are still poorly understood, but important for understanding their relative role to biogeochemical cycles.
Alyse Larkin & Zackary Johnson OCB217
Thraustochytrids are unicellular fungi-like (heterotrophic) marine protists and have long been considered to play an important role in the biogeochemical cycles of the coastal oceans. However, the significance of their ecological functions and diversity in marine ecosystems remain largely unknown. In this report, we examined the spatial and temporal variations of planktonic thraustochytrids, their relationship with other environmental factors, and their diversity in the subtropical coastal waters of China. The abundance of planktonic thraustochytrids ranged from 2.56 × 105 to 17.57 × 105 cells L−1 with highest abundance detected in polluted coastal water and the Spring (March) season. Thraustochytrids biomass was greater than bacterial biomass in most of seawater samples, ranging from 32.29 to 359.51% that of bacterioplankton. The abundance of thraustochytrids appeared to be largely related to that of bacterioplankton and chemical oxygen demand (COD) in water columns. High-throughput sequencing analyses revealed a total of 105 OTUs (97% similarity), which were members of genera Thraustochytrium, Aplanochytrium, Oblongichytrium, Ulkenia, Labyrinthula and undescribed novel phylotypes. Results of this study indicated unprecedented high diversity of labyrinthulomycetes as well as the presence of novel labyrinthulomycetes and thraustochytrids lineage, and also provided new information on the significant role of thraustochytrids in microbial food webs in a coastal marine ecosystem.
Trace metals and B-vitamins play critical roles in regulating marine phytoplankton growth and composition. While some microorganisms are capable of producing certain B-vitamins, others cannot synthesize them and depend on an exogenous supply. Therefore, external factors influencing vitamin synthesis, such as micronutrient concentrations, alter the extent to which B-vitamins are available to auxotrophs in surface waters. We examined iron, B7 (biotin) and B12 (cobalamin) dynamics in diatoms through laboratory culture experiments and within natural diatom assemblages present along an iron gradient in the Northeast Pacific Ocean. In laboratory cultures of the diatom Pseudo-nitzschia granii, biotin synthase (BIOB) expression decreased 2-fold under iron limitation, suggesting iron status may affect B7 production in diatoms. Additionally in laboratory cultures of the diatom Grammonema cf. islandica, which contains a B12-independent methionine synthase (METE), a 15-fold increase in the expression of METE was observed when grown in the absence of B12 with no significant influence of iron status, suggesting METE expression can be driven by B12 status alone. Iron and B-vitamin amendment experiments with natural diatom assemblages in iron-limited waters of the Northeast Pacific Ocean provide evidence for vitamin-associated molecular responses that suggest elevated B7 biosynthesis and the emergence of B12 limitation following iron addition. Furthermore B-vitamin gene modules comprised of partial and/or complete B-vitamin biosynthetic pathways in diatoms increased in response to iron addition, including genes potentially involved in the processing of B12 intermediates. Our results indicate that vitamins may play an important role in regulating phytoplankton growth and composition in this region, particularly following natural iron addition events.
On Saturday, April 1st, 135 middle school girls visited the Duke Marine Lab to take part in hands-on activities in the fields of microbiology, remote sensing, geographic information systems, environmental engineering, developmental biology, marine science, physics, and more. The goal of GEST is to expose girls to STEM opportunities and role models in eastern North Carolina.
Activities were led by local researchers and educators with a passion for outreach. Volunteers came from a wide range of institutions and organizations, including Duke, UNC, NC State, NOAA, the NC Coastal Federation, Ocracoke School, and Marine Corps Air Station Cherry Point. PhD student and Johnson Lab member Sarah Loftus is a co-founder of GEST and worked on the planning team to
organize the event. PhD student Courtney Swink was an activity leader, conducting an experiment with algae cultures and teaching the girls about biofuel applications. Girls were inquisitive and curious, and Courtney’s activity received some high praise in the event survey. We’re already looking forward to hosting GEST again next year.
Current high costs of commercial-scale algal biofuel production prevent the widespread use of this renewable fuel source. One cost-saving approach is the reuse of algae cultivation water after biomass harvesting, which reduces water pumping and treatment costs. However, dissolved compounds, cell debris, and microorganisms remaining in the water could affect subsequent algae generations. Previous studies demonstrate a variety of effects of recycled medium on algae growth, yet their results have not been collectively analyzed. Here we integrate data across 86 studies to determine the relative importance of different factors influencing algae growth in recycled medium. We found that algae taxa can have the greatest influence, while the harvesting method is less influential on growth outcomes. This meta-analysis identifies favorable taxa and thus provides a tool for algae cultivation decision-making when medium reuse is an important driver. Results can also aid in estimating relative algae yield and growth rates for technoeconomic assessments that incorporate water recycling.
Supplementary Information includes full dataset.
The fluorescent stain Nile Red has been used extensively for the quantification of lipids in phytoplankton, including microalgae, because it preferentially stains neutral lipids and it is economical and sensitive to use for screening purposes. Although its basic application has not changed for several decades, recent improvements have been made to improve its utility across applications. Here we describe additional refinements in its application and interpretation as a high-throughput method for the rapid quantification of neutral lipids in liquid cultures of marine phytoplankton. Specifically we address (1) interspecies comparisons, (2) fluorescence excitation and emission wavelengths, and (3) the time course of the Nile Red signal in the context of using bulk or cell-specific fluorescence to quantify neutral lipids of live or preserved cells. We show that with proper caution in its interpretation across species and physiological states the quantity of lipid in hundreds of small volume samples can be reliably assessed daily using a refined Nile Red protocol.
Sarah and Courtney travelled to Durham on Saturday, February 25th to lead activities at the annual FEMMES Capstone event on main campus. FEMMES (Females Excelling More in Math, Engineering, and Science) is an undergraduate-led organization that seeks to provide STEM opportunities and role models to local female students. Hundreds of 4th-6th graders attended the event and each participated in 4 various STEM activities led by Duke researchers.
Thirty girls participated in Sarah and Courtney’s activities throughout the day. After learning about algae growth requirements and applications of algae, they designed and set up an experiment to test how different light levels affect algae growth. Sarah and Courtney brought the “results” previously grown in our lab, and girls measured and graphed the turbidity of the algae cultures. They enjoyed using laboratory tools and seeing if the results matched their hypotheses. Some even left thinking that “algae are cool,” which means mission accomplished!
Marine microbes exhibit seasonal cycles in community composition, yet the key drivers of these patterns and microbial population fidelity to specific environmental conditions remain to be determined. To begin addressing these questions, we characterized microbial dynamics weekly for 3 years at a temperate, coastal site with dramatic environmental seasonality. This high-resolution time series reveals that changes in microbial community composition are not continuous; over the duration of the time series, the community instead resolves into distinct summer and winter profiles with rapid spring and fall transitions between these states. Here, we show that these community shifts involve switching between closely related strains that exhibit either summer or winter preferences. Moreover, taxa repeat this process annually in both this and another temperate coastal time series, suggesting that this phenomenon may be widespread in marine ecosystems. To address potential biogeochemical impacts of these community changes, PICRUSt-based metagenomes predict seasonality in transporters, photosynthetic proteins, peptidases and carbohydrate metabolic pathways in spite of closely related summer- and winter-associated taxa. Thus, even small temperature shifts, such as those predicted by climate change models, could affect both the structure and function of marine ecosystems.
Prof. Claudia Benitez-Nelson of the University of South Carolina visited the Duke Marine Lab and gave a stirring seminar on harmful algal blooms off of California. Claudia’s talk, “Neurotoxins and the Environment. Understanding the Production, Cycling and Fate of Domoic Acid Along the California Coast” was a fantastic mixture of oceanography and environmental monitoring, all in the context of environmental change and management. Can’t wait to have her come back and hear more about her exciting research!
The microbe team welcomed two new students, Elsa (Jia Li) and Norah (Xue Rui), two visiting undergraduates to the group. They are joining the lab for 5 months to complete their undergraduate honors dissertations at Tianjin University, China. Both are working on the molecular diversity of microbes, in the context of environmental variability. Elsa is focusing on the cyanobacteria of the North Pacific, while Norah is working with cyanobacterial communities from the PICO project. Welcome!
The Pivers Island Coastal Observatory (PICO) closed 2016 by reaching a major milestone – the 750th time point! Started in mid-2010 as an undergraduate independent student project focusing on ocean acidification, the coastal time-series has matured into a long term coastal sentinel, observing seasonal, yearly and interannual changes in the physics, chemistry and biology of the coastal marine environment with weekly sampling. Additional offshore longitudinal sampling (PICO-LOVE) provides spatial context. Data is available through BCO-DMO. Congratulations team PICO!
Climate, energy, and food security are three of the greatest challenges society faces this century. Solutions for mitigating the effects of climate change often conflict with solutions for ensuring society’s future energy and food requirements. For example, BioEnergy with Carbon Capture and Storage (BECCS) has been proposed as an important method for achieving negative CO2 emissions later this century while simultaneously producing renewable energy on a global scale. However, BECCS has many negative environmental consequences for land, nutrient, and water use as well as biodiversity and food production. In contrast, large-scale industrial cultivation of marine microalgae can provide society with a more environmentally favorable approach for meeting the climate goals agreed to at the 2015 Paris Climate Conference, producing the liquid hydrocarbon fuels required by the global transportation sector, and supplying much of the protein necessary to feed a global population approaching 10 billion people.
Greene, C.H., M.E. Huntley, I. Archibald, L.N. Gerber, D.L. Sills, J. Granados, J.W. Tester, C.M. Beal, M.J. Walsh, R.R. Bidigare, S.L. Brown, W.P. Cochlan, Z.I. Johnson, X.G. Lei, S.C. Machesky, D.G. Redalje, R.E. Richardson, V. Kiron, and V. Corless. 2016. Marine microalgae: Climate, energy, and food security from the sea. Oceanography 29(4), https://doi.org/10.5670/oceanog.2016.91.
Approximately 100 sixth graders from Morehead City visited the Marine Laboratory to learn about marine science and experience a college campus. Six learning stations covered different aspects of marine science from fisheries to marine mammals to remote sensing. The Sarah Loftus, Courtney Swink and Bailey Slagle of the Marine Microbe Group described the importance of algae (phytoplankton) for natural ecosystems as well as the current research in the group to develop algae as a sustainable source of food and fuel. Students made media, started cultures and even tasted some algae cookies. Yum!
The goals of ensuring energy, water, food, and climate security can often conflict. Microalgae (algae) are being pursued as a feedstock for both food and fuels—primarily due to algae’s high areal yield and ability to grow on non-arable land, thus avoiding common bioenergy-food tradeoffs. However, algal cultivation requires significant energy inputs that may limit potential emission reductions. We examine the tradeoffs associated with producing fuel and food from algae at the energy–food–water–climate nexus. We use the GCAM integrated assessment model to demonstrate that algal food production can promote reductions in land-use change emissions through the offset of conventional agriculture. However, fuel production, either via co-production of algal food and fuel or complete biomass conversion to fuel, is necessary to ensure long-term emission reductions, due to the high energy costs of cultivation. Cultivation of salt–water algae for food products may lead to substantial freshwater savings; but, nutrients for algae cultivation will need to be sourced from waste streams to ensure sustainability. By reducing the land demand of food production, while simultaneously enhancing food and energy security, algae can further enable the development of terrestrial bioenergy technologies including those utilizing carbon capture and storage. Our results demonstrate that large-scale algae research and commercialization efforts should focus on developing both food and energy products to achieve environmental goals.
PhD student Sarah Loftus attended the 10th annual Algae Biomass Summit in Phoenix, AZ. The summit brings together individuals from academia, industry, and government who research, lobby for, and capitalize on the products and services provided by algae, notably biofuels, food, carbon capture, wastewater treatment, and more. Sarah won first place in the Young Researcher Poster Competition, Biology Division, for her poster titled “Meta-analysis reveals influential and non-influential factors affecting algae growth in recycled cultivation water.”
Victoire Blanc-Garin visited the Johnson Lab from France for 6 weeks. While in Beaufort, her research focused on comparing the variability of outdoor cultures with those in constant conditions indoors. She showed that outdoor environmental conditions can be at times extreme, but generally the algae strains examined were able to grow as well and sometimes better outdoors. We wish her the best back in Paris and hope to work with her again in the future.
ZIJ presented at ISME16 in Montreal on the temperature regulation of Prochlorococcus photosynthesis and growth under the title, “The effect of temperature on gene expression and carbon uptake/release in diverse strains of Prochlorococcus” Its a good time to be a Microbial Ecology!
Abstract: The ecological success of the marine cyanobacteria Prochlorococcus is driven in part by its genomic diversity and the concentrations of the two dominant high light clades in the ocean have been shown to niche partition along latitudinal temperature gradients. Nevertheless, little is known about how temperature affects carbon uptake and its fate for these genetically distinct, yet closely related cyanobacteria. Here we present results from temperature acclimation experiments and show that while temperature has an expected (and differential) effect on the major clades of Prochlorococcus, the temperature response curves of carbon uptake and growth rate are uncoupled. Further, there are substantial differences among the clades in how temperature affects the partitioning of this carbon to particulate (i.e. retained) or dissolved (i.e. dissolved organic carbon release) fates. Physiology and transcript data show even more dramatic uncoupling of carbon uptake/fate growth rate (biomass accumulation or division) and regulation with different responses between the two clades. These results highlight the importance of temperature in poising the fundamental processes of Prochlorococcus photosynthesis and growth, and that the physiological and regulatory responses are different between the major genetic clades. These results also demonstrate that future climate scenarios with increased temperature may significantly alter the distribution, biogeochemical rates and role of Prochlorococcus and its clades in broader marine microbial communities through changes in cell division and carbon fate.
Alyse Larkin successfully defended her PhD titled, “Ecological Controls on Prochlorococcus sp. Diversity, Composition, and Activity at High Taxonomic Resolution” She will continue working on marine microbial ecology at UC Irvine working as a postdoc. Congratulations!
On Saturday, the Johnson Lab welcomed hundreds of people into the laboratory as part of the Duke Marine Lab’s annual Open House event. The Open House is an opportunity for the public to tour DUML facilities, learn about ongoing research, and view some of that research in action. Upstairs in the Pilkey Laboratory, the Johnson Lab spoke to community members about both PICO and algae biofuel projects. Research technician Sara Blinebry showed her video of the weekly PICO sampling process. She explained that these samples help us understand changes in coastal ocean acidity and seasonal changes in the marine microbial community. PhD student Courtney Swink displayed cultures of green algae and diatoms, and talked about the Johnson Lab’s role in studying algae cultivation for biofuels and co-products. PhD student Sarah Loftus then gave visitors a closer look at these cultures under the microscope and answered questions about microalgae.
Experts in the field of algal biology shared their recent successes with participants at the DOE Algal Biology Toolbox to further the community’s understanding of the current state of the art. These presentations ensure that a range of expertise is represented at the event. ZIJ presented pilot results from MAGIC- the Marine Algae Industrialization Consortium specifically focusing on LCA/TEA, cultivation strategies and initial co-product trials.
The National Ocean Science Bowl Finals were held in Morehead City, NC with many local marine scientists and marine laboratories facilitating the event. (ZIJ served as a science judge for some of the competition.) The finals had the theme,“Our Changing Ocean: Science for Strong Coastal Communities.” The National Ocean Sciences Bowl is an education competition that tests students’ knowledge of ocean-related topics, which include cross-disciplines of biology, chemistry, policy, physics, and geology. The NOSB is an interdisciplinary ocean science education program of the Consortium for Ocean Leadership based in Washington, D.C.