In Situ Incubation and Filtration System for the Pelagic Ocean (InSIncFS)

Lead Research Organisation: University of Southampton
Department Name: Sch of Ocean and Earth Science


The Ocean is a key climate regulator: Has it not been its 'biological carbon pump' (BCP), atmospheric CO2 would have been at least twice as high as it is today. BCP operates with CO2 firstly absorbed and fixed into organic carbon in the surface ocean by photosynthetic phytoplankton, then a fraction of this carbon is transferred into the deep interior of the ocean where it is locked away (sequestered) for centuries. Hence, the efficiency of BCP relies on the productivity of surface phytoplankton, interactions with other microbes and organisms that might hamper the carbon delivery to the deep, and respiration -feeding on the fixed carbon as food and converted back to CO2- in the twilight ocean, the critical buffer zone between the sunlit surface and the deep ocean. Meanwhile, it is also this phytoplankton-derived fixed carbon that feeds the majority of diverse marine life, and forms the basis of many ecosystem services and food security that humans enjoy. Under current, rapid climate change, ocean warming and stratification limits the replenishment of nutrients in the surface ocean, while seawater becomes more acidic and loses oxygen. The latter especially can stimulate production of even stronger greenhouse gases like methane and nitrous oxide. Clearly, accurate understanding of all these biogeochemical processes, mediated mostly by small plankton and microbes, is critical to our ability to project future changes on our planet.

How marine biogeochemists and plankton ecologists have been assessing activity of these important processes to date are mostly based on incubation experiments conducted on shipboard: Briefly, samples of water and resident plankton are taken out from ocean depths, brought onto ship-deck and into various bottles, perhaps with additions of indicator compounds for tracing changes (e.g. rare isotopes 13C and 15N) or hypothesised substrates that might simulate activity (e.g. iron). They are placed in a lab incubator at similar temperature as found at in situ depths for a period of time to monitor changes in chemical/biological properties, possibly with screens to mimic light intensity in deeper water. However, atmospheric pressure is typically used in ex-situ incubations, even though the sample may have come from 100's-1000's m depth, so decompression to 1 bar from originally 10's to 100's bar! As one can imagine, the conditions experienced by the plankton/ microbes during such ex-situ incubations can be vastly different from their real habitats, and any activity measurements thus obtained most certainly differ from reality. Moreover, 'omics analyses, especially those of RNA, have recently become very useful in studying active metabolisms and pathways organisms use (e.g. Tara Oceans). However, plankton respond quickly to changes and RNA can be altered within seconds to minutes, so they have most likely changed during the journey between sampled water depths and the collection on ship-deck.

Despite these artefacts, shipboard incubations and RNA filtration are widely used - because there is no other practical option. It is unknown how much error and extent of misunderstanding such artefact-laden activity measurements and RNA profiles might have brought, and they are currently used in models.

The proposed In Situ Incubation and Filtration System (InSIncFS) for the pelagic ocean will provide, for the first time, a transformative platform for truly in situ activity assessments with integrated sensors, large array of possible parallel hypothesis-driven experiments, and in situ RNA-preservation. It will eliminate the artefacts of ex situ incubations, and correct for the inaccuracies of activities previously determined ex situ. No such system exists in the world. InSIncFS will enable us to truly answer questions on climate change that has not been possible before. It represents world-class innovation and paves the way toward NERC's ambition of Net Zero Oceanographic Capability on autonomous activity sensing.


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