- Sensitivity of the Relationship Between Antarctic Ice Shelves and Iron Supply to Projected Changes in the Atmospheric Forcing JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2023; 128 (2)
- Linking multiple stressor science to policy opportunities through network modeling MARINE POLICY 2022; 146
- Wildfire aerosol deposition likely amplified a summertime Arctic phytoplankton bloom COMMUNICATIONS EARTH & ENVIRONMENT 2022; 3 (1)
- North-South Differences in Under-Ice Primary Production in the Chukchi Sea From 1988 to 2018 JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2022; 127 (7)
- Springtime phytoplankton responses to light and iron availability along the western Antarctic Peninsula LIMNOLOGY AND OCEANOGRAPHY 2022
- The distribution of Fe across the shelf of the Western Antarctic Peninsula at the start of the phytoplankton growing season MARINE CHEMISTRY 2022; 238
Increases in Arctic sea ice algal habitat, 1985-2018
Elementa: Science of the Anthropocene
2022; 10 (1)
View details for DOI 10.1525/elementa.2022.00008
- Warming of the Indian Ocean and its impact on temporal and spatial dynamics of primary production PROGRESS IN OCEANOGRAPHY 2021; 198
UCYN-A/haptophyte symbioses dominate N2 fixation in the Southern California Current System.
2021; 1 (1): 42
The availability of fixed nitrogen (N) is an important factor limiting biological productivity in the oceans. In coastal waters, high dissolved inorganic N concentrations were historically thought to inhibit dinitrogen (N2) fixation, however, recent N2 fixation measurements and the presence of the N2-fixing UCYN-A/haptophyte symbiosis in nearshore waters challenge this paradigm. We characterized the contribution of UCYN-A symbioses to nearshore N2 fixation in the Southern California Current System (SCCS) by measuring bulk community and single-cell N2 fixation rates, as well as diazotroph community composition and abundance. UCYN-A1 and UCYN-A2 symbioses dominated diazotroph communities throughout the region during upwelling and oceanic seasons. Bulk N2 fixation was detected in most surface samples, with rates up to 23.0 ± 3.8 nmol N l-1 d-1, and was often detected at the deep chlorophyll maximum in the presence of nitrate (>1 µM). UCYN-A2 symbiosis N2 fixation rates were higher (151.1 ± 112.7 fmol N cell-1 d-1) than the UCYN-A1 symbiosis (6.6 ± 8.8 fmol N cell-1 d-1). N2 fixation by the UCYN-A1 symbiosis accounted for a majority of the measured bulk rates at two offshore stations, while the UCYN-A2 symbiosis was an important contributor in three nearshore stations. This report of active UCYN-A symbioses and broad mesoscale distribution patterns establishes UCYN-A symbioses as the dominant diazotrophs in the SCCS, where heterocyst-forming and unicellular cyanobacteria are less prevalent, and provides evidence that the two dominant UCYN-A sublineages are separate ecotypes.
View details for DOI 10.1038/s43705-021-00039-7
View details for PubMedID 36740625
View details for PubMedCentralID PMC9723760
Massive Southern Ocean phytoplankton bloom fed by iron of possible hydrothermal origin.
2021; 12 (1): 1211
Primary production in the Southern Ocean (SO) is limited by iron availability. Hydrothermal vents have been identified as a potentially important source of iron to SO surface waters. Here we identify a recurring phytoplankton bloom in the high-nutrient, low-chlorophyll waters of the Antarctic Circumpolar Current in the Pacific sector of the SO, that we argue is fed by iron of hydrothermal origin. In January 2014 the bloom covered an area of ~266,000 km2 with depth-integrated chlorophyll a>300mgm-2, primary production rates >1gC m-2 d-1, and a mean CO2 flux of -0.38gC m-2 d-1. The elevated iron supporting this bloom is likely of hydrothermal origin based on the recurrent position of the bloom relative to two active hydrothermal vent fields along the Australian Antarctic Ridge and the association of the elevated iron with a distinct water mass characteristic of a nonbuoyant hydrothermal vent plume.
View details for DOI 10.1038/s41467-021-21339-5
View details for PubMedID 33619262
Response of Lower Sacramento River phytoplankton to high-ammonium wastewater effluent
Elementa: Science of the Anthropocene
View details for DOI 10.1525/elementa.2021.040
- Dissolved Trace Metals in the Ross Sea FRONTIERS IN MARINE SCIENCE 2020; 7
- Comparison of Cloud-Filling Algorithms for Marine Satellite Data REMOTE SENSING 2020; 12 (20)
- Summer High-Wind Events and Phytoplankton Productivity in the Arctic Ocean JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2020; 125 (9)
- Environmental drivers of under-ice phytoplankton bloom dynamics in the Arctic Ocean ELEMENTA-SCIENCE OF THE ANTHROPOCENE 2020; 8
- Iron from melting glaciers fuels the phytoplankton blooms in Amundsen Sea (Southern Ocean): iron biogeochemistry (vol 71, pg 16, 2012) DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2020; 177
Unusual marine cyanobacteria/haptophyte symbiosis relies on N2 fixation even in N-rich environments.
The ISME journal
The microbial fixation of N2 is the largest source of biologically available nitrogen (N) to the oceans. However, it is the most energetically expensive N-acquisition process and is believed inhibited when less energetically expensive forms, like dissolved inorganic N (DIN), are available. Curiously, the cosmopolitan N2-fixing UCYN-A/haptophyte symbiosis grows in DIN-replete waters, but the sensitivity of their N2 fixation to DIN is unknown. We used stable isotope incubations, catalyzed reporter deposition fluorescence in-situ hybridization (CARD-FISH), and nanoscale secondary ion mass spectrometry (nanoSIMS), to investigate the N source used by the haptophyte host and sensitivity of UCYN-A N2 fixation in DIN-replete waters. We demonstrate that under our experimental conditions, the haptophyte hosts of two UCYN-A sublineages do not assimilate nitrate (NO3-) and meet little of their N demands via ammonium (NH4+) uptake. Instead the UCYN-A/haptophyte symbiosis relies on UCYN-A N2 fixation to supply large portions of the haptophyte's N requirements, even under DIN-replete conditions. Furthermore, UCYN-A N2 fixation rates, and haptophyte host carbon fixation rates, were at times stimulated by NO3- additions in N-limited waters suggesting a link between the activities of the bulk phytoplankton assemblage and the UCYN-A/haptophyte symbiosis. The results suggest N2 fixation may be an evolutionarily viable strategy for diazotroph-eukaryote symbioses, even in N-rich coastal or high latitude waters.
View details for DOI 10.1038/s41396-020-0691-6
View details for PubMedID 32523086
- Climate effects on temporal and spatial dynamics of phytoplankton and zooplankton in the Barents Sea PROGRESS IN OCEANOGRAPHY 2020; 185
- Analysis of Iron Sources in Antarctic Continental Shelf Waters JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2020; 125 (5)
Synergistic interactions among growing stressors increase risk to an Arctic ecosystem.
2020; 11 (1): 6255
Oceans provide critical ecosystem services, but are subject to a growing number of external pressures, including overfishing, pollution, habitat destruction, and climate change. Current models typically treat stressors on species and ecosystems independently, though in reality, stressors often interact in ways that are not well understood. Here, we use a network interaction model (OSIRIS) to explicitly study stressor interactions in the Chukchi Sea (Arctic Ocean) due to its extensive climate-driven loss of sea ice and accelerated growth of other stressors, including shipping and oil exploration. The model includes numerous trophic levels ranging from phytoplankton to polar bears. We find that climate-related stressors have a larger impact on animal populations than do acute stressors like increased shipping and subsistence harvesting. In particular, organisms with a strong temperature-growth rate relationship show the greatest changes in biomass as interaction strength increased, but also exhibit the greatest variability. Neglecting interactions between stressors vastly underestimates the risk of population crashes. Our results indicate that models must account for stressor interactions to enable responsible management and decision-making.
View details for DOI 10.1038/s41467-020-19899-z
View details for PubMedID 33288746
Changes in phytoplankton concentration now drive increased Arctic Ocean primary production.
Science (New York, N.Y.)
2020; 369 (6500): 198–202
Historically, sea ice loss in the Arctic Ocean has promoted increased phytoplankton primary production because of the greater open water area and a longer growing season. However, debate remains about whether primary production will continue to rise should sea ice decline further. Using an ocean color algorithm parameterized for the Arctic Ocean, we show that primary production increased by 57% between 1998 and 2018. Surprisingly, whereas increases were due to widespread sea ice loss during the first decade, the subsequent rise in primary production was driven primarily by increased phytoplankton biomass, which was likely sustained by an influx of new nutrients. This suggests a future Arctic Ocean that can support higher trophic-level production and additional carbon export.
View details for DOI 10.1126/science.aay8380
View details for PubMedID 32647002
- Light Is the Primary Driver of Early Season Phytoplankton Production Along the Western Antarctic Peninsula JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2019
- The organic complexation of iron in the Ross sea MARINE CHEMISTRY 2019; 215
- Effects of iron and light availability on phytoplankton photosynthetic properties in the Ross Sea MARINE ECOLOGY PROGRESS SERIES 2019; 621: 33–50
- Publisher Correction: Ecological control of nitrite in the upper ocean. Nature communications 2019; 10 (1): 4618
- Photoacclimation of Arctic Ocean phytoplankton to shifting light and nutrient limitation LIMNOLOGY AND OCEANOGRAPHY 2019; 64 (1): 284–301
- Nitrogen Limitation of the Summer Phytoplankton and Heterotrophic Prokaryote Communities in the Chukchi Sea FRONTIERS IN MARINE SCIENCE 2018; 5
- Drivers of Ice Algal Bloom Variability Between 1980 and 2015 in the Chukchi Sea JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2018; 123 (10): 7037–52
- Ice algal communities in the Chukchi and Beaufort Seas in spring and early summer: Composition, distribution, and coupling with phytoplankton assemblages LIMNOLOGY AND OCEANOGRAPHY 2018; 63 (3): 1109–33
- Exploring the Potential Impact of Greenland Meltwater on Stratification, Photosynthetically Active Radiation, and Primary Production in the Labrador Sea JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2018; 123 (4): 2570–91
Ecological control of nitrite in the upper ocean
2018; 9: 1206
Microorganisms oxidize organic nitrogen to nitrate in a series of steps. Nitrite, an intermediate product, accumulates at the base of the sunlit layer in the subtropical ocean, forming a primary nitrite maximum, but can accumulate throughout the sunlit layer at higher latitudes. We model nitrifying chemoautotrophs in a marine ecosystem and demonstrate that microbial community interactions can explain the nitrite distributions. Our theoretical framework proposes that nitrite can accumulate to a higher concentration than ammonium because of differences in underlying redox chemistry and cell size between ammonia- and nitrite-oxidizing chemoautotrophs. Using ocean circulation models, we demonstrate that nitrifying microorganisms are excluded in the sunlit layer when phytoplankton are nitrogen-limited, but thrive at depth when phytoplankton become light-limited, resulting in nitrite accumulation there. However, nitrifying microorganisms may coexist in the sunlit layer when phytoplankton are iron- or light-limited (often in higher latitudes). These results improve understanding of the controls on nitrification, and provide a framework for representing chemoautotrophs and their biogeochemical effects in ocean models.
View details for PubMedID 29572474
- Under-Ice Phytoplankton Blooms Inhibited by Spring Convective Mixing in Refreezing Leads JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2018; 123 (1): 90–109
- Early Spring Phytoplankton Dynamics in the Western Antarctic Peninsula JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2017; 122 (12): 9350–69
- Differential effects of nitrate, ammonium, and urea as N sources for microbial communities in the North Pacific Ocean LIMNOLOGY AND OCEANOGRAPHY 2017; 62 (6): 2550–74
- Late Spring Nitrate Distributions Beneath the Ice-Covered Northeastern Chukchi Shelf JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES 2017; 122 (9): 2409–17
- Melting glaciers stimulate large summer phytoplankton blooms in southwest Greenland waters GEOPHYSICAL RESEARCH LETTERS 2017; 44 (12): 6278–85
- Regional chlorophyll a algorithms in the Arctic Ocean and their effect on satellite-derived primary production estimates DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2016; 130: 14-27
- Mass balance estimates of carbon export in different water masses of the Chukchi Sea shelf DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2016; 130: 88-99
- Spatial analysis of trends in primary production and relationship with large-scale climate variability in the Ross Sea, Antarctica (1997-2013) JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2016; 121 (1): 368-386
- Sources of iron in the Ross Sea Polynya in early summer MARINE CHEMISTRY 2015; 177: 447-459
- Iron supply and demand in an Antarctic shelf ecosystem GEOPHYSICAL RESEARCH LETTERS 2015; 42 (19): 8088-8097
- Impacts of low phytoplankton NO3- :PO43- utilization ratios over the Chukchi Shelf, Arctic Ocean DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2015; 118: 105-121
- Environmental controls of marine productivity hot spots around Antarctica JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2015; 120 (8): 5545-5565
- The influence of winter water on phytoplankton blooms in the Chukchi Sea DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2015; 118: 53-72
- Continued increases in Arctic Ocean primary production PROGRESS IN OCEANOGRAPHY 2015; 136: 60-70
- Characterizing the subsurface chlorophyll a maximum in the Chukchi Sea and Canada Basin DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2015; 118: 88-104
- Phytoplankton blooms beneath the sea ice in the Chukchi sea DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2014; 105: 1-16
- Evidence of under-ice phytoplankton blooms in the Chukchi Sea from 1998 to 2012 DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2014; 105: 105-117
- Response of marine bacterioplankton to a massive under-ice phytoplankton bloom in the Chukchi Sea (Western Arctic Ocean) DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2014; 105: 74-84
- Productivity in the Barents Sea - Response to Recent Climate Variability PLOS ONE 2014; 9 (5)
Productivity in the barents sea--response to recent climate variability.
2014; 9 (5)
The temporal and spatial dynamics of primary and secondary biomass/production in the Barents Sea since the late 1990s are examined using remote sensing data, observations and a coupled physical-biological model. Field observations of mesozooplankton biomass, and chlorophyll a data from transects (different seasons) and large-scale surveys (autumn) were used for validation of the remote sensing products and modeling results. The validation showed that satellite data are well suited to study temporal and spatial dynamics of chlorophyll a in the Barents Sea and that the model is an essential tool for secondary production estimates. Temperature, open water area, chlorophyll a, and zooplankton biomass show large interannual variations in the Barents Sea. The climatic variability is strongest in the northern and eastern parts. The moderate increase in net primary production evident in this study is likely an ecosystem response to changes in climate during the same period. Increased open water area and duration of open water season, which are related to elevated temperatures, appear to be the key drivers of the changes in annual net primary production that has occurred in the northern and eastern areas of this ecosystem. The temporal and spatial variability in zooplankton biomass appears to be controlled largely by predation pressure. In the southeastern Barents Sea, statistically significant linkages were observed between chlorophyll a and zooplankton biomass, as well as between net primary production and fish biomass, indicating bottom-up trophic interactions in this region.
View details for DOI 10.1371/journal.pone.0095273
View details for PubMedID 24788513
View details for PubMedCentralID PMC4006807
- Light and nutrient control of photosynthesis in natural phytoplankton populations from the Chukchi and Beaufort seas, Arctic Ocean LIMNOLOGY AND OCEANOGRAPHY 2013; 58 (6): 2185-2205
- Long-term trends of upwelling and impacts on primary productivity in the Alaskan Beaufort Sea DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS 2013; 79: 106-121
- Insignificant buffering capacity of Antarctic shelf carbonates GLOBAL BIOGEOCHEMICAL CYCLES 2013; 27 (1): 11-20
- Photoacclimation and non-photochemical quenching under in situ irradiance in natural phytoplankton assemblages from the Amundsen Sea, Antarctica MARINE ECOLOGY PROGRESS SERIES 2013; 475: 15-?
- Patterns and controlling factors of species diversity in the Arctic Ocean JOURNAL OF BIOGEOGRAPHY 2012; 39 (11): 2081-2088
- Annual changes in sea ice and phytoplankton in polynyas of the Amundsen Sea, Antarctica DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2012; 71-76: 5-15
- Phytoplankton biomass and pigment responses to Fe amendments in the Pine Island and Amundsen polynyas DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2012; 71-76: 61-76
- Iron from melting glaciers fuels the phytoplankton blooms in Amundsen Sea (Southern Ocean): Iron biogeochemistry DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2012; 71-76: 16-31
- Iron from melting glaciers fuels phytoplankton blooms in the Amundsen Sea (Southern Ocean): Phytoplankton characteristics and productivity DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2012; 71-76: 32-48
- Key role of organic complexation of iron in sustaining phytoplankton blooms in the Pine Island and Amundsen Polynyas (Southern Ocean) DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2012; 71-76: 49-60
ASPIRE The Amundsen Sea Polynya International Research Expedition
2012; 25 (3): 40-53
View details for Web of Science ID 000308774600009
Massive Phytoplankton Blooms Under Arctic Sea Ice
2012; 336 (6087): 1408-1408
Phytoplankton blooms over Arctic Ocean continental shelves are thought to be restricted to waters free of sea ice. Here, we document a massive phytoplankton bloom beneath fully consolidated pack ice far from the ice edge in the Chukchi Sea, where light transmission has increased in recent decades because of thinning ice cover and proliferation of melt ponds. The bloom was characterized by high diatom biomass and rates of growth and primary production. Evidence suggests that under-ice phytoplankton blooms may be more widespread over nutrient-rich Arctic continental shelves and that satellite-based estimates of annual primary production in these waters may be underestimated by up to 10-fold.
View details for DOI 10.1126/science.1215065
View details for Web of Science ID 000305211700035
View details for PubMedID 22678359
- Mapping phytoplankton iron utilization: Insights into Southern Ocean supply mechanisms JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2012; 117
- THE EFFECT OF IRON LIMITATION ON THE PHOTOPHYSIOLOGY OF PHAEOCYSTIS ANTARCTICA (PRYMNESIOPHYCEAE) AND FRAGILARIOPSIS CYLINDRUS (BACILLARIOPHYCEAE) UNDER DYNAMIC IRRADIANCE JOURNAL OF PHYCOLOGY 2012; 48 (1): 45-59
THE EFFECT OF IRON LIMITATION ON THE PHOTOPHYSIOLOGY OF PHAEOCYSTIS ANTARCTICA (PRYMNESIOPHYCEAE) AND FRAGILARIOPSIS CYLINDRUS (BACILLARIOPHYCEAE) UNDER DYNAMIC IRRADIANCE(1).
Journal of phycology
2012; 48 (1): 45-59
The effects of iron limitation on photoacclimation to dynamic irradiance were studied in Phaeocystis antarctica G. Karst. and Fragilariopsis cylindrus (Grunow) W. Krieg. in terms of growth rate, photosynthetic parameters, pigment composition, and fluorescence characteristics. Under dynamic light conditions mimicking vertical mixing below the euphotic zone, P. antarctica displayed higher growth rates than F. cylindrus both under iron (Fe)-replete and Fe-limiting conditions. Both species showed xanthophyll de-epoxidation that was accompanied by low levels of nonphotochemical quenching (NPQ) during the irradiance maximum of the light cycle. The potential for NPQ at light levels corresponding to full sunlight was substantial in both species and increased under Fe limitation in F. cylindrus. Although the decline in Fv /Fm under Fe limitation was similar in both species, the accompanying decrease in the maximum rate of photosynthesis and growth rate was much stronger in F. cylindrus. Analysis of the electron transport rates through PSII and on to carbon (C) fixation revealed a large potential for photoprotective cyclic electron transport (CET) in F. cylindrus, particularly under Fe limitation. Probably, CET aided the photoprotection in F. cylindrus, but it also reduced photosynthetic efficiency at higher light intensities. P. antarctica, on the other hand, was able to efficiently use electrons flowing through PSII for C fixation at all light levels, particularly under Fe limitation. Thus, Fe limitation enhanced the photophysiological differences between P. antarctica and diatoms, supporting field observations where P. antarctica is found to dominate deeply mixed water columns, whereas diatoms dominate shallower mixed layers.
View details for DOI 10.1111/j.1529-8817.2011.01098.x
View details for PubMedID 27009649
- Primary productivity in the Arctic Ocean: Impacts of complex optical properties and subsurface chlorophyll maxima on large-scale estimates JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2011; 116
- Secular trends in Arctic Ocean net primary production JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2011; 116
- A reassessment of primary production and environmental change in the Bering Sea JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2011; 116
- Responses of psbA, hli and ptox genes to changes in irradiance in marine Synechococcus and Prochlorococcus AQUATIC MICROBIAL ECOLOGY 2011; 65 (1): 1-14
- Influence of atmospheric nutrients on primary productivity in a coastal upwelling region GLOBAL BIOGEOCHEMICAL CYCLES 2010; 24
- PHOTOPHYSIOLOGY IN TWO SOUTHERN OCEAN PHYTOPLANKTON TAXA: PHOTOSYNTHESIS OF PHAEOCYSTIS ANTARCTICA (PRYMNESIOPHYCEAE) AND FRAGILARIOPSIS CYLINDRUS (BACILLARIOPHYCEAE) UNDER SIMULATED MIXED-LAYER IRRADIANCE JOURNAL OF PHYCOLOGY 2010; 46 (6): 1114-1127
- STRATEGIES AND RATES OF PHOTOACCLIMATION IN TWO MAJOR SOUTHERN OCEAN PHYTOPLANKTON TAXA: PHAEOCYSTIS ANTARCTICA (HAPTOPHYTA) AND FRAGILARIOPSIS CYLINDRUS (BACILLARIOPHYCEAE) JOURNAL OF PHYCOLOGY 2010; 46 (6): 1138-1151
Photophysiology in Two Major Southern Ocean Phytoplankton Taxa: Photosynthesis and Growth of Phaeocystis antarctica and Fragilariopsis cylindrus under Different Irradiance Levels
Annual Meeting of the Society-for-Integrative-and-Comparative-Biology
OXFORD UNIV PRESS INC. 2010: 950–66
The Ross Sea, Antarctica, supports two distinct populations of phytoplankton, one that grows well in sea ice and blooms in the shallow mixed layers of the Western marginal ice zone and the other that can be found in sea ice but thrives in the deeply mixed layers of the Ross Sea. Dominated by diatoms (e.g. Fragilariopsis cylindrus) and the prymnesiophyte Phaeocystis antarctica, respectively, the processes leading to the development of these different phytoplankton assemblages are not well known. The goal of this article was to gain a better understanding of the photophysiological characteristics that allow each taxon to dominate its specific habitat. Cultures of F. cylindrus and P. antarctica were each grown semi-continuously at four different constant irradiances (5, 25, 65, and 125 µmol quanta/m2/s). Fragilariopsis cylindrus produced far less photosynthetic pigment per cell than did P. antarctica but much more photoprotective pigment. Fragilariopsis cylindrus also exhibited substantially lower rates of photosynthesis and growth but also was far less susceptible to photoinhibition of cell growth. Excess photosynthetic capacity, a measure of the ability of phytoplankton to exploit variable light environments, was significantly higher in both strains of P. antarctica than in F. cylindrus. The combination of these characteristics suggests that F. cylindrus has a competitive advantage under conditions where mixed layers are shallow and light levels are relatively constant and high. In contrast, P. antarctica should dominate waters where mixed layers are deep and light levels are variable. These results are consistent with distributions of phytoplankton in the Ross Sea and suggest that light is the primary factor determining composition of phytoplankton communities.
View details for DOI 10.1093/icb/icq021
View details for Web of Science ID 000284430400005
View details for PubMedID 21558252
- Air-sea flux of CO2 in the Arctic Ocean, 1998-2003 JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES 2010; 115
Contrasting spring and summer phytoplankton dynamics in the nearshore Southern California Bight
LIMNOLOGY AND OCEANOGRAPHY
2010; 55 (1): 264-278
View details for Web of Science ID 000272759900015
Photophysiology in two major Southern Ocean phytoplankton taxa: Photoprotection in Phaeocystis antarctica and Fragilariopsis cylindrus
LIMNOLOGY AND OCEANOGRAPHY
2009; 54 (4): 1176-1196
View details for Web of Science ID 000268325100014
- Coastal Southern Ocean: A strong anthropogenic CO2 sink GEOPHYSICAL RESEARCH LETTERS 2008; 35 (21)
- Impact of a shrinking Arctic ice cover on marine primary production GEOPHYSICAL RESEARCH LETTERS 2008; 35 (19)
- Primary production in the Arctic Ocean, 1998-2006 JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2008; 113 (C8)
- Primary production in the Southern Ocean, 1997-2006 JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2008; 113 (C8)
Alternative photosynthetic electron flow to oxygen in marine Synechococcus
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
2008; 1777 (3): 269-276
Cyanobacteria dominate the world's oceans where iron is often barely detectable. One manifestation of low iron adaptation in the oligotrophic marine environment is a decrease in levels of iron-rich photosynthetic components, including the reaction center of photosystem I and the cytochrome b6f complex [R.F. Strzepek and P.J. Harrison, Photosynthetic architecture differs in coastal and oceanic diatoms, Nature 431 (2004) 689-692.]. These thylakoid membrane components have well characterised roles in linear and cyclic photosynthetic electron transport and their low abundance creates potential impediments to photosynthetic function. Here we show that the marine cyanobacterium Synechococcus WH8102 exhibits significant alternative electron flow to O2, a potential adaptation to the low iron environment in oligotrophic oceans. This alternative electron flow appears to extract electrons from the intersystem electron transport chain, prior to photosystem I. Inhibitor studies demonstrate that a propyl gallate-sensitive oxidase mediates this flow of electrons to oxygen, which in turn alleviates excessive photosystem II excitation pressure that can often occur even at relatively low irradiance. These findings are also discussed in the context of satisfying the energetic requirements of the cell when photosystem I abundance is low.
View details for DOI 10.1016/j.bbabio.2008.01.002
View details for Web of Science ID 000254674600004
View details for PubMedID 18241667
- Interannual variation in air-sea CO2 flux in the Ross Sea, Antarctica: A model analysis JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2007; 112 (C3)
- Increased exposure of Southern Ocean phytoplankton to ultraviolet radiation GEOPHYSICAL RESEARCH LETTERS 2004; 31 (9)
- Annual cycles of sea ice and phytoplankton in Cape Bathurst polynya, southeastern Beaufort Sea, Canadian Arctic GEOPHYSICAL RESEARCH LETTERS 2004; 31 (8)
- Annual changes in sea-ice, chlorophyll a, and primary production in the Ross Sea, Antarctica DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 2004; 51 (1-3): 117-138
- Phytoplankton dynamics within 37 Antarctic coastal polynya systems JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2003; 108 (C8)
- Impact of iceberg C-19 on Ross Sea primary production GEOPHYSICAL RESEARCH LETTERS 2003; 30 (16)
- Impact of a deep ozone hole on Southern Ocean primary production JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2003; 108 (C5)
- A comparison between excess barium and barite as indicators of carbon export PALEOCEANOGRAPHY 2003; 18 (1)
- Ecological impact of a large Antarctic iceberg GEOPHYSICAL RESEARCH LETTERS 2002; 29 (7)