Developmental exposure of zebrafish to saxitoxin causes altered expression of genes associated with axonal growth.

Saxitoxin (STX) is a potent neurotoxin naturally produced by dinoflagellates and cyanobacteria. STX inhibits voltage-gated sodium channels (VGSCs), affecting the propagation of action potentials. Consumption of seafood contaminated with STX is responsible for paralytic shellfish poisoning (PSP).

Novel isolates expand the physiological diversity of and illuminate its macroevolution.

is a diverse picocyanobacterial genus and the most abundant phototroph on Earth. Its photosynthetic diversity divides it into high-light (HL)- or low-light (LL)-adapted groups representing broad phylogenetic grades-each composed of several monophyletic clades. Here, we physiologically characterize four new strains isolated from below the deep chlorophyll maximum in the North Pacific Ocean.

Antarctic pelagic ecosystems on a warming planet.

High-latitude pelagic marine ecosystems are vulnerable to climate change because of the intertwining of sea/continental ice dynamics, physics, biogeochemistry, and food-web structure. Data from the West Antarctic Peninsula allow us to assess how ice influences marine food webs by modulating solar inputs to the ocean, inhibiting wind mixing, altering the freshwater balance and ocean stability, and providing a physical substrate for organisms. State changes are linked to an increase in storm forcing and changing distribution of ocean heat.

Microbial dietary preference and interactions affect the export of lipids to the deep ocean.

Lipids comprise a significant fraction of sinking organic matter in the ocean and play a crucial role in the carbon cycle. Despite this, our understanding of the processes that control lipid degradation is limited. We combined nanolipidomics and imaging to study the bacterial degradation of diverse algal lipid droplets and found that bacteria isolated from marine particles exhibited distinct dietary preferences, ranging from selective to promiscuous degraders.

Viral Infection Leads to a Unique Suite of Allelopathic Chemical Signals in Three Diatom Host-Virus Pairs.

Ecophysiological stress and the grazing of diatoms are known to elicit the production of chemical defense compounds called oxylipins, which are toxic to a wide range of marine organisms. Here we show that (1) the viral infection and lysis of diatoms resulted in oxylipin production; (2) the suite of compounds produced depended on the diatom host and the infecting virus; and (3) the virus-mediated oxylipidome was distinct, in both magnitude and diversity, from oxylipins produced due to stress associated with the growth phase. We used high-resolution accurate-mass mass spectrometry to observe changes in the dissolved lipidome of diatom cells infected with viruses over 3 to 4 days, compared to diatom cells in exponential, stationary, and decline phases of growth.

RotoBOD─Quantifying Oxygen Consumption by Suspended Particles and Organisms.

Sinking or floating is the natural state of planktonic organisms and particles in the ocean. Simulating these conditions is critical when making measurements, such as respirometry, because they allow the natural exchange of substrates and products between sinking particles and water flowing around them and prevent organisms that are accustomed to motion from changing their metabolism. We developed a rotating incubator, the RotoBOD (named after its capability to rotate and determine biological oxygen demand, BOD), that uniquely enables automated oxygen measurements in small volumes while keeping the samples in their natural state of suspension.

Growth and mortality of aerobic anoxygenic phototrophs in the North Pacific Subtropical Gyre.

Aerobic anoxygenic phototrophic (AAP) bacteria harvest light energy using bacteriochlorophyll-containing reaction centers to supplement their mostly heterotrophic metabolism. While their abundance and growth have been intensively studied in coastal environments, much less is known about their activity in oligotrophic open ocean regions. Therefore, we combined sampling in the North Pacific Subtropical Gyre, north of O'ahu island, Hawaii, with two manipulation experiments.

Global ocean lipidomes show a universal relationship between temperature and lipid unsaturation.

Global-scale surveys of plankton communities using "omics" techniques have revolutionized our understanding of the ocean. Lipidomics has demonstrated the potential to add further essential insights on ocean ecosystem function but has yet to be applied on a global scale. We analyzed 930 lipid samples across the global ocean using a uniform high-resolution accurate-mass mass spectrometry analytical workflow, revealing previously unknown characteristics of ocean planktonic lipidomes.

Complex marine microbial communities partition metabolism of scarce resources over the diel cycle.

Complex assemblages of microbes in the surface ocean are responsible for approximately half of global carbon fixation. The persistence of high taxonomic diversity despite competition for a small suite of relatively homogeneously distributed nutrients, that is, 'the paradox of the plankton', represents a long-standing challenge for ecological theory. Here we find evidence consistent with temporal niche partitioning of nitrogen assimilation processes over a diel cycle in the North Pacific Subtropical Gyre.

Seasonal mixed layer depth shapes phytoplankton physiology, viral production, and accumulation in the North Atlantic.

Seasonal shifts in phytoplankton accumulation and loss largely follow changes in mixed layer depth, but the impact of mixed layer depth on cell physiology remains unexplored. Here, we investigate the physiological state of phytoplankton populations associated with distinct bloom phases and mixing regimes in the North Atlantic. Stratification and deep mixing alter community physiology and viral production, effectively shaping accumulation rates.

Prochlorococcus extracellular vesicles: molecular composition and adsorption to diverse microbes.

Extracellular vesicles are small (~50-200 nm diameter) membrane-bound structures released by cells from all domains of life. While vesicles are abundant in the oceans, their functions, both for cells themselves and the emergent ecosystem, remain a mystery. To better characterize these particles - a prerequisite for determining function - we analysed the lipid, protein, and metabolite content of vesicles produced by the marine cyanobacterium Prochlorococcus.

Using High-Sensitivity Lipidomics To Assess Microscale Heterogeneity in Oceanic Sinking Particles and Single Phytoplankton Cells.

Sinking particulate organic matter (POM) is a primary component of the ocean's biological carbon pump that is responsible for carbon export from the surface to the deep sea. Lipids derived from plankton comprise a significant fraction of sinking POM. Our understanding of planktonic lipid biosynthesis and the subsequent degradation of lipids in sinking POM is based on the analysis of bulk samples that combine many millions of plankton cells or dozens of sinking particles, which averages out natural heterogeneity.

Production of Two Highly Abundant 2-Methyl-Branched Fatty Acids by Blooms of the Globally Significant Marine Cyanobacteria .

The bloom-forming cyanobacteria contribute up to 30% to the total fixed nitrogen in the global oceans and thereby drive substantial productivity. On an expedition in the Gulf of Mexico, we observed and sampled surface slicks, some of which included dense blooms of . These bloom samples contained abundant and atypical free fatty acids, identified here as 2-methyldecanoic acid and 2-methyldodecanoic acid.

Arsenolipids in Plankton from High- and Low-Nutrient Oceanic Waters Along a Transect in the North Atlantic.

Although the natural occurrence of arsenic-containing lipids (arsenolipids) in marine organisms is now well established, the possible role of these unusual compounds in organisms and in the cycling of arsenic in marine systems remains largely unexplored. We report the finding of arsenolipids in 61 plankton samples collected from surface marine waters of high- and low-nutrient content along a transect spanning the Gulf Stream in the North Atlantic Ocean. Using high-performance liquid chromatography (HPLC) coupled to both elemental and molecular mass spectrometry, we show that all 61 plankton samples contained six identifiable arsenolipids, namely, three arsenosugar phospholipids (AsPL958, 10-13%; AsPL978, 13-25%; and AsPL1006, 7-10% of total arsenolipids), two arsenic-containing hydrocarbons (AsHC332, 4-10% and AsHC360, 1-2%), and a methoxy-sugar arsenolipid that contained phytol (AsSugPhytol, 1-3%).

Microbial production and consumption of hydrocarbons in the global ocean.

Seeps, spills and other oil pollution introduce hydrocarbons into the ocean. Marine cyanobacteria also produce hydrocarbons from fatty acids, but little is known about the size and turnover of this cyanobacterial hydrocarbon cycle. We report that cyanobacteria in an oligotrophic gyre mainly produce n-pentadecane and that microbial hydrocarbon production exhibits stratification and diel cycling in the sunlit surface ocean.

Coordinated transformation of the gut microbiome and lipidome of bowhead whales provides novel insights into digestion.

Whale digestion plays an integral role in many ocean ecosystems. By digesting enormous quantities of lipid-rich prey, whales support their energy intensive lifestyle, but also excrete nutrients important to ocean biogeochemical cycles. Nevertheless, whale digestion is poorly understood.

Biochemical diversity of glycosphingolipid biosynthesis as a driver of Coccolithovirus competitive ecology.

Coccolithoviruses (EhVs) are large, double-stranded DNA-containing viruses that infect the single-celled, marine coccolithophore Emiliania huxleyi. Given the cosmopolitan nature and global importance of E. huxleyi as a bloom-forming, calcifying, photoautotroph, E.

Nitric oxide production and antioxidant function during viral infection of the coccolithophore Emiliania huxleyi.

Emiliania huxleyi is a globally important marine phytoplankton that is routinely infected by viruses. Understanding the controls on the growth and demise of E. huxleyi blooms is essential for predicting the biogeochemical fate of their organic carbon and nutrients.

Daily changes in phytoplankton lipidomes reveal mechanisms of energy storage in the open ocean.

Sunlight is the dominant control on phytoplankton biosynthetic activity, and darkness deprives them of their primary external energy source. Changes in the biochemical composition of phytoplankton communities over diel light cycles and attendant consequences for carbon and energy flux in environments remain poorly elucidated. Here we use lipidomic data from the North Pacific subtropical gyre to show that biosynthesis of energy-rich triacylglycerols (TAGs) by eukaryotic nanophytoplankton during the day and their subsequent consumption at night drives a large and previously uncharacterized daily carbon cycle.

Diverse diazotrophs are present on sinking particles in the North Pacific Subtropical Gyre.

Sinking particles transport carbon and nutrients from the surface ocean into the deep sea and are considered hot spots for bacterial diversity and activity. In the oligotrophic oceans, nitrogen (N)-fixing organisms (diazotrophs) are an important source of new N but the extent to which these organisms are present and exported on sinking particles is not well known. Sinking particles were collected every 6 h over a 2-day period using net traps deployed at 150 m in the North Pacific Subtropical Gyre.

The mutual interplay between calcification and coccolithovirus infection.

Two prominent characteristics of marine coccolithophores are their secretion of coccoliths and their susceptibility to infection by coccolithoviruses (EhVs), both of which display variation among cells in culture and in natural populations. We examined the impact of calcification on infection by challenging a variety of Emiliania huxleyi strains at different calcification states with EhVs of different virulence. Reduced cellular calcification was associated with increased infection and EhV production, even though calcified cells and associated coccoliths had significantly higher adsorption coefficients than non-calcified (naked) cells.