Oontong-Java Plateau

ABSTRACTNitrogen-fixing (N2) cyanobacteria provide bioavailable nitrogen to vast ocean regions but are in turn limited by iron (Fe) and/or phosphorus (P), which may force them to employ alternative nitrogen acquisition strategies. The adaptive responses of nitrogen fixers to global-change drivers under nutrient-limited conditions could profoundly alter the current ocean nitrogen and carbon cycles. Here, we show that the globally important N2fixerTrichodesmiumfundamentally shifts nitrogen metabolism toward organic-nitrogen scavenging following long-term high-CO2adaptation under iron and/or phosphorus (co)limitation. Global shifts in transcripts and proteins under high-CO2/Fe-limited and/or P-limited conditions include decreases in the N2-fixing nitrogenase enzyme, coupled with major increases in enzymes that oxidize trimethylamine (TMA). TMA is an abundant, biogeochemically important organic nitrogen compound that supports rapidTrichodesmiumgrowth while inhibiting N2fixation. In a future high-CO2ocean, this whole-cell energetic reallocation toward organic nitrogen scavenging and away from N2fixation may reduce new-nitrogen inputs byTrichodesmiumwhile simultaneously depleting the scarce fixed-nitrogen supplies of nitrogen-limited open-ocean ecosystems.IMPORTANCETrichodesmiumis among the most biogeochemically significant microorganisms in the ocean, since it supplies up to 50% of the new nitrogen supporting open-ocean food webs. We usedTrichodesmiumcultures adapted to high-CO2conditions for 7 years, followed by additional exposure to iron and/or phosphorus (co)limitation. We show that “future ocean” conditions of high CO2and concurrent nutrient limitation(s) fundamentally shift nitrogen metabolism away from nitrogen fixation and instead toward upregulation of organic nitrogen-scavenging pathways. We show that the responses ofTrichodesmiumto projected future ocean conditions include decreases in the nitrogen-fixing nitrogenase enzymes coupled with major increases in enzymes that oxidize the abundant organic nitrogen source trimethylamine (TMA). Such a shift toward organic nitrogen uptake and away from nitrogen fixation may substantially reduce new-nitrogen inputs byTrichodesmiumto the rest of the microbial community in the future high-CO2ocean, with potential global implications for ocean carbon and nitrogen cycling.

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OIL SPILL CLEANUP IN SEVERE WEATHER AND OPEN OCEAN CONDITIONS

International Oil Spill Conference Proceedings ◽

10.7901/2169-3358-1993-1-787 ◽

1993 ◽

Vol 1993 (1) ◽

pp. 787-788

Author(s):

Tadeusz Kowalski

Keyword(s):

Oil Spill ◽

Open Ocean ◽

Severe Weather ◽

Ocean Conditions ◽

Oil Spill Cleanup

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A DETAILED INVESTIGATION OF THALLIUM ISOTOPES UNDER LOW-OXYGEN OPEN OCEAN CONDITIONS

10.1130/abs/2020se-344870 ◽

2020 ◽

Author(s):

Sean M. Newby ◽

◽

Siqi Li ◽

Adam Karl ◽

Silke Severmann ◽

...

Keyword(s):

Open Ocean ◽

Low Oxygen ◽

Ocean Conditions

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Manual dexterity task performance efficiency in the open ocean underwater environment

PsycEXTRA Dataset ◽

10.1037/e573962012-022 ◽

1982 ◽

Author(s):

P. A. Hancock ◽

E. K. Milner

Keyword(s):

Task Performance ◽

Manual Dexterity ◽

Open Ocean ◽

Underwater Environment

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Drivers of diversity gradients of a highly mobile marine assemblage in a mesoscale seascape

Marine Ecology Progress Series ◽

10.3354/meps13264 ◽

2020 ◽

Vol 638 ◽

pp. 149-164

Author(s):

GM Svendsen ◽

M Ocampo Reinaldo ◽

MA Romero ◽

G Williams ◽

A Magurran ◽

...

Keyword(s):

Environmental Gradients ◽

Regression Tree ◽

Demersal Fish ◽

Open Ocean ◽

Shared Resources ◽

Thermal Front ◽

Boosted Regression Tree ◽

Diversity Gradients ◽

Α Diversity ◽

Bottom Depth

With the unprecedented rate of biodiversity change in the world today, understanding how diversity gradients are maintained at mesoscales is a key challenge. Drawing on information provided by 3 comprehensive fishery surveys (conducted in different years but in the same season and with the same sampling design), we used boosted regression tree (BRT) models in order to relate spatial patterns of α-diversity in a demersal fish assemblage to environmental variables in the San Matias Gulf (Patagonia, Argentina). We found that, over a 4 yr period, persistent diversity gradients of species richness and probability of an interspecific encounter (PIE) were shaped by 3 main environmental gradients: bottom depth, connectivity with the open ocean, and proximity to a thermal front. The 2 main patterns we observed were: a monotonic increase in PIE with proximity to fronts, which had a stronger effect at greater depths; and an increase in PIE when closer to the open ocean (a ‘bay effect’ pattern). The originality of this work resides on the identification of high-resolution gradients in local, demersal assemblages driven by static and dynamic environmental gradients in a mesoscale seascape. The maintenance of environmental gradients, specifically those associated with shared resources and connectivity with an open system, may be key to understanding community stability.

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