Year: 2025
Type: article
Abstract: Carbon flux to the deep sea can be dictated by surface ocean phytoplankton community composition, but translating surface ocean observations into quantitative predictions of carbon export requires additional consideration of the underlying ecosystem drivers. Here, we used genetic tracers of phytoplankton detected in surface seawater and within sinking particles collected in the mesopelagic ocean to identify mechanistic links between surface communities and carbon export in the North Pacific and North Atlantic Oceans. Phytoplankton 18S rRNA gene sequences were sampled over a 1-month period in surface seawater and within bulk-collected and individually isolated sinking particles using mesopelagic sediment traps (100-500 m). Nearly all phytoplankton amplicon sequence variants exported from the surface were packaged in large (>300 μm) particles. Individually, each of these particles contained only a few distinct phytoplankton amplicon sequence variants, but collectively, large particles transported about half of the surface taxonomic diversity into the mesopelagic. The relative sequence abundances of the surface community detected within particles were quantitatively related to measured carbon fluxes: a linear model based on the relative sequence abundance of just two pigment-based phytoplankton taxa, diatoms and photosynthetic Hacrobia, was predictive of carbon flux magnitude. These two taxa were also enriched in the ecologically distinct particle classes that had the greatest influence on carbon export magnitude. As global, hyperspectral ocean color satellites begin to quantify these taxonomic groups in the surface ocean, the relationship of these taxa to carbon fluxes demonstrated here may help in developing more accurate algorithms to estimate global carbon export in the ocean.
Source: The ISME Journal
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,153
Awards: SINKING PARTICULATE ORGANIC MATTER IS A MAJOR ROUTE OF CARBON EXPORT FROM THE SUNLIT SURFACE OCEAN TO THE OCEAN'S INTERIOR. BOTH SINGLECELLED MICROBES AND ZOOPLANKTON PLAY A ROLE IN SETTING THE FATE OF PARTICLES IN SUBSURFACE MESOPELAGIC WATERS. MICROBES EXPLOIT THE RAIN OF CARBON-RICH MATERIAL AS A SUBSTRATE FOR GROWTH OFTEN ATTACHING TO SINKING PARTICLES PARTIALLY DISSOLVING THEM AND RESPIRING THE CARBON AS CO2. ALTHOUGH WE KNOW THAT PARTICLE FLUX IS MARKEDLY ATTENUATED WITH DEPTH PREDICTING THE MICROBIAL CONTRIBUTION TO THIS LOSS TERM USING SURFACE MEASUREMENTS IS CURRENTLY NOT POSSIBLE. THE GOAL OF THIS PROPOSAL IS TO DEVELOP A MECHANISTIC LINK BETWEEN MICROBIAL ATTENUATION OF SINKING PARTICLE FLUX AND SURFACE OCEAN PROPERTIES WITH THE FOLLOWING OBJECTIVES: MEASURE IN SITU THE MAGNITUDE OF MICROBIAL RESPIRATION AS A SINK FOR CARBON THROUGHOUT THE UPPER MESOPELAGIC DURING THE TWO EXPORTS FIELD CAMPAIGNS REFINE THE EXISTING CONCEPTUAL MODEL OF THE RELATIONSHIP BETWEEN SURFACE ECOSYSTEMS SUBSURFACE BIOGEOCHEMICAL CHARACTERISTICS MICROBIAL RESPIRATION AND TRANSFER EFFICIENCY OF CARBON THROUGH THE MESOPELAGIC DEVELOP A PREDICTIVE SUBSURFACE PARTICLE REMINERALIZATION MODEL THAT CAN BE INCORPORATED INTO EXPORTS DATA PRODUCTS TO ACCOMPLISH THESE OBJECTIVES WE WILL DEPLOY REPLICATED SETS OF PARTICLE CAPTURE DEVICES EQUIPPED WITH OXYGEN OPTODE-BASED RESPIRATION CHAMBERS THROUGHOUT THE MESOPELAGIC DURING THE EXPORTS FIELD CAMPAIGNS. THESE SYSTEMS KNOWN AS RESPIRE TRAPS ALLOW FOR THE IN SITU CAPTURE OF SINKING PARTICLES AND SUBSEQUENT TRACKING OF OXYGEN CONSUMPTION. WE WILL COMPARE RESPIRATION RATES TO SUBSURFACE ECOSYSTEM AND BIOGEOCHEMICAL CHARACTERISTICS INCLUDING PARTICLE SINKING RATES GEOCHEMICAL CHARACTERIZATION OF PARTICLES AND MICROBIAL COMMUNITY STRUCTURE. WE WILL FURTHER COMPARE OUR RESULTS TO REMOTELY-SENSED PROPERTIES SUCH AS NET PRIMARY PRODUCTION PHYTOPLANKTON COMMUNITY COMPOSITION AND PARTICLE SIZE SPECTRA TO DETERMINE THE MECHANISTIC BASIS FOR THE RELATIONSHIP BETWEEN SURFACE OCEAN PROPERTIES AND SUBSURFACE ACTIVITY. THIS RESEARCH WILL DETERMINE THE IMPORTANCE OF MICROBIAL PROCESSES RELATIVE TO OTHER POTENTIAL SINKS SUCH AS ZOOPLANKTON PARTICLE CONSUMPTION. THE STATED GOAL OF THE EXPORTS PROGRAM IS TO CREATE A PREDICTIVE UNDERSTANDING OF BOTH THE EXPORT OF ORGANIC CARBON FROM THE UPPER OCEAN AND ITS FATE IN THE UNDERLYING 'TWILIGHT ZONE.' HERE BY QUANTIFYING POTENTIALLY THE MOST INFLUENTIAL TRANSFORMATION PATHWAY FOR POC IN THE SUBSURFACE (MICROBIAL RESPIRATION AND HENCE REMINERALIZATION) AND COMPARING IT TO OBSERVATIONS OF THE SURFACE PHYTOPLANKTON COMMUNITY (BOTH REMOTELY-SENSED AND SHIPBOARD OBSERVATIONS) WE WILL DETERMINE WHICH SURFACE ECOLOGICAL AND BIOGEOCHEMICAL PROPERTIES ENABLE THE MOST RELIABLE PREDICTION OF MICROBIAL ATTENUATION OF PARTICLE FLUX. THIS PROPOSAL RESPONDS TO SECTION 3.1 EXPORT PROCESSES IN THE OCEAN FROM REMOTE SENSING (EXPORTS) RESEARCH FIELD INVESTIGATIONS OF THE 2106 NASA ROSES CALL FOR PROPOSALS A.3 OCEAN BIOLOGY AND BIOGEOCHEMISTRY (NNH16ZDA001N-OBB)., G8535509796, PREDATION BY MICROZOOPLANKTON (MZ) IS THE SINGLE LARGEST LOSS FACTOR OF MARINE PRIMARY PRODUCTION (PP) AND ALTERS THE ABUNDANCE AND SIZE SPECTRUM OF PARTICLES IN THE WATER COLUMN. MZ CONSUME LIVING CELLS AND SINKING AGGREGATES AND SERVE AS PREY TO VERTICALLY MIGRATING METAZOANS. OUR HYPOTHESES ARE 1) MZ PREDATION OF PP IMPACTS RATES OF EXPORT PRODUCTION THROUGH ALL 5 PATHWAYS PREDICTABLY AND 2) HIGH RATES OF PREDATION YIELD LOW CARBON EXPORT RATES. WE PROPOSE TO QUANTIFY PREDATION EFFECTS ON PP PARTICLE ABUNDANCE AND SIZE DISTRIBUTION AS A FUNCTION OF CO-OCCURRING ENVIRONMENTAL AND BIOLOGICAL CONDITIONS (I.E. ECOSYSTEM/CARBON CYCLING STATES (ECC)) TO GAIN A MECHANISTIC AND PREDICTIVE UNDERSTANDING OF THE CARBON FLOW IN THE EUPHOTIC ZONE AND BELOW. WE WILL PROVIDE ESSENTIAL DATA DESCRIBED IN THE IMPLEMENTATION PLAN AND ADDRESS ELEMENTS OF SCIENCE QUESTIONS 1&2. WE WILL IDENTIFY LINKAGES AMONG PREDATOR MEDIATED CARBON FLOWS ENVIRONMENTAL DRIVERS AND EXPORT PRODUCTION WHICH ARE CRUCIAL FOR DEVELOPING A) THE DIAGNOSTIC AND PROGNOSTIC RELATIONSHIPS NECESSARY TO ADDRESS SQ3 AND B) THE PREDICTIVE MODELING FRAMEWORK TO ACHIEVE KEY GOALS OF THE EXPORTS MISSION.
OpenAlex ID: W4410610909