The Outsized Role of Salps in Carbon Export in the Subarctic Northeast Pacific Ocean
Year: 2022
Type: article
Abstract: Periodic blooms of salps (pelagic tunicates) can result in high export of organic matter, leading to an “outsized” role in the ocean's biological carbon pump (BCP). However, due to their episodic and patchy nature, salp blooms often go undetected and are rarely included in measurements or models of the BCP. We quantified salp‐mediated export processes in the northeast subarctic Pacific Ocean in summer of 2018 during a bloom ofSalpa aspera. Salps migrated from 300 to 750 m during the day into the upper 100 m at night. Salp fecal pellet production comprised up to 82% of the particulate organic carbon (POC) produced as fecal pellets by the entire epipelagic zooplankton community. Rapid sinking velocities of salp pellets (400–1,200 m d−1) and low microbial respiration rates on pellets (<1% of pellet C respired day−1) led to high salp pellet POC export from the euphotic zone‐up to 48% of total sinking POC across the 100 m depth horizon. Salp active transport of carbon by diel vertical migration and carbon export from sinking salp carcasses was usually <10% of the total sinking POC flux. Salp‐mediated export markedly increased BCP efficiency, increasing by 1.5‐fold the proportion of net primary production exported as POC across the base of the euphotic zone and by 2.6‐fold the proportion of this POC flux persisting 100 m below the euphotic zone. Salps have unique and important effects on ocean biogeochemistry and, especially in low flux settings, can dramatically increase BCP efficiency and thus carbon sequestration.
Source: Global Biogeochemical Cycles
DOI: 10.1029/2022gb007523
Institutions: William & Mary, Virginia Institute of Marine Science, Bigelow Laboratory for Ocean Sciences, Bermuda Institute of Ocean Sciences, Monterey Bay Aquarium Research Institute, Memorial University of Newfoundland, University of Maine, University of Rhode Island, University of Alaska Fairbanks, Fisheries and Oceans Canada, University of California, Santa Barbara
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,600
Awards: THE MAGNITUDE OF PARTICULATE CARBON EXPORT FROM THE UPPER OCEAN AND EFFICIENCY OF ITS TRANSFER INTO THE INTERIOR REMAINS ONE OF THE LEAST PREDICTABLE PROCESSES INFLUENCING THE GLOBAL CARBON CYCLE. THE OVERARCHING GOAL OF THE EXPORTS PROGRAM IS TO DEVELOP MECHANISTIC MODELS PREDICTING THE STRENGTH AND EFFICIENCY OF THIS EXPORTED CARBON. A CENTRAL REQUIREMENT ONE MIGHT ARGUE THE CENTRAL REQUIREMENT OF THE AMBITIOUS SET OF FIELD MEASUREMENTS NECESSARY TO DEVELOP SATELLITE-DRIVEN MODELS IS ACCURATE MEASUREMENT OF SINKING PARTICLE FLUXES AND THEIR BIOLOGICAL AND CHEMICAL COMPOSITIONS. THESE MEASUREMENTS MUST BE EMBEDDED IN A BROADER SUITE OF PHYSICAL BIOLOGICAL AND OPTICAL OBSERVATIONS SO A SECOND REQUIREMENT IS THAT THE TEAM QUANTIFYING PARTICLE FLUX COOPERATES AND WORKS CLOSELY WITH THE BROADER EXPORTS SCIENCE TEAM. HERE WE PROPOSE A HYPOTHESIS-DRIVEN STUDY OF PARTICLE FLUXES THAT BOTH ADVANCES OUR UNDERSTANDING OF THE OCEAN BIOLOGICAL CARBON PUMP AND MEETS THE BROADER PROGRAM GOALS ABOVE. THE BROAD HYPOTHESIS OF THE EXPORTS PROGRAM IS THAT THE STRENGTH AND EFFICIENCY OF THE BIOLOGICAL CARBON PUMP CAN BE PREDICTED FROM SATELLITE OCEAN COLOR OBSERVATIONS. IMPLICIT IN THIS HYPOTHESIS ARE A NUMBER OF ASSUMPTIONS WHICH MUST BE TESTED. THE SPECIFIC HYPOTHESES WE WILL ADDRESS ARE 1) THAT THE BIOLOGICAL ORIGIN OF THE PARTICLES SINKING OUT OF THE EUPHOTIC ZONE EXERTS SIGNIFICANT CONTROL ON BOTH THE MAGNITUDE OF THE SINKING CARBON FLUX AND ITS RATE OF ATTENUATION WITH DEPTH; AND 2) THAT TEMPORAL VARIABILITY IN THE MAGNITUDE AND ATTENUATION OF SINKING PARTICLE FLUX IS CAUSED BY BIOLOGICAL PROCESSES., PARTICLE SIZE HAS FUNDAMENTAL CONTROL ON THE DISTRIBUTION AND DYNAMICS OF PARTICULATE CARBON IN THE UPPER OCEAN. STOKES LAW STATES THAT PARTICLES WITH LARGER EFFECTIVE DIAMETERS (D) WILL SINK FASTER THAN SMALLER ONES DETERMINING WHETHER PARTICLES ARE EFFECTIVELY SUSPENDED WITHIN THE WATER COLUMN (D<~100 M) OR ARE SINKING (D>~500 M). NET PRIMARY PRODUCTION (NPP) ENTERS PELAGIC ECOSYSTEMS AS SUSPENDED PARTICLES AND THESE PARTICLES (ALONG WITH CDOM) CONTROL THE OCEAN S OPTICAL PROPERTIES. FURTHER SINKING PARTICLES UNDERGO MANY BIOTIC AND ABIOTIC TRANSFORMATIONS IN THEIR SIZE COMPOSITION AND SINKING VELOCITY AS THEY TRANSIT FROM THE SURFACE OCEAN REGULATING CARBON EXPORT AND REMINERALIZATION PROFILES. THIS POINTS TO THE IMPORTANCE OF UNDERSTANDING THE PARTICLE SIZE DISTRIBUTION (PSD) IN PREDICTING THE FATE OF NPP THE CENTRAL GOAL OF EXPORTS. WE PROPOSE TO ANSWER FOUR SCIENCE QUESTIONS TO DEVELOP A PREDICTIVE UNDERSTANDING OF THE PSD FOR BOTH SUSPENDED AND SINKING PARTICLES. 1. HOW DO THE ABUNDANCE COMPOSITION AND PRODUCTIVITY OF PARTICLE SOURCE MATERIALS REGULATE THE PSD FOR SMALLER OPTICALLY RELEVANT PARTICLE SIZES? 2. HOW DO SOURCE PARTICLE CHARACTERISTICS AS WELL AS BIOTIC / ABIOTIC INTERACTIONS ON SINKING PARTICLES REGULATE THE PSD FOR LARGER CARBON EXPORT RELEVANT PARTICLE SIZES? 3. CAN THE COMBINED SIZE DISTRIBUTION FOR SUSPENDED AND SINKING PARTICLES BE MODELED USING OPTICAL DATA AND IN PARTICULAR FROM SATELLITE OCEAN COLOR OBSERVATIONS? 4. HOW DO ENERGY AND CARBON DERIVED FROM PHYTOPLANKTON NPP CASCADE THROUGH THE PARTICLE SIZE SPECTRUM? THESE FOUR SCIENCE QUESTIONS ADDRESS ASPECTS OF MANY OF THE EXPORTS SCIENCE QUESTIONS (SQ) AND ANSWERS SQ1C AND SQ1D DIRECTLY. WE PROPOSE AN INTEGRATED RESEARCH PROGRAM OF IN SITU OPTICAL AND IMAGERY OBSERVATION (SIEGEL NELSON MCDONNELL) AT-SEA CHARACTERIZATION AND EXPERIMENTATION ON COLLECTED AGGREGATES (PASSOW) AND NUMERICAL MODELING (BURD SIEGEL). ADVANCES IN NEARFORWARD ANGLE LIGHT SCATTER (LISST) AND IN SITU IMAGING (UVP) ENABLE HIGH-RESOLUTION PROFILES OF THE PSD FOR BOTH SUSPENDED AND SINKING PARTICULATES. INHERENT OPTICAL AND OCEANOGRAPHIC PROPERTIES WILL BE MONITORED SIMULTANEOUSLY TO CHARACTERIZE SUSPENDED PARTICLE COMPOSITION AND OCEANIC CONTEXT. WE WILL COLLECT SINKING AGGREGATES USING THE MARINE SNOW CATCHER TO CHARACTERIZE THEIR ECOLOGICAL AND BIOGEOCHEMICAL COMPOSITION PHYSICAL PROPERTIES AS WELL AS THEIR DECOMPOSITION RATES ALL OF WHICH ARE NEEDED FOR MODELING. THE ASSEMBLED DATA SET WILL BE THE BASIS OF MECHANISTIC NUMERICAL MODELS THAT TRANSFORM THE COMBINED PSD AS A FUNCTION OF DEPTH AND ECOSYSTEM / CARBON CYCLING STATE. WE WILL TEST RELATIONSHIPS AMONG SOURCE MATERIALS (PHYTOPLANKTON ZOOPLANKTON FECES ETC.) AND BIOTIC (ZOOPLANKTON GRAZING ETC.) AND ABIOTIC (TURBULENCE DENSITY GRADIENTS ETC.) DISRUPTERS OF AGGREGATE DISTRIBUTIONS. DATA AVAILABLE FROM OTHER EXPORTS INVESTIGATIONS (PARTICLE EXPORT&COMPOSITION PHYTOPLANKTON ABUNDANCE&COMPOSITION NPP ETC.) WILL BE INCORPORATED AS NEEDED. FOR EXAMPLE WE WILL ASSESS THE SINKING VELOCITY SIZE SPECTRUM USING COLLECTED TRAP SAMPLES AND OUR PSD MEASUREMENTS AS WELL AS SPATIOTEMPORAL VALIDATED FIELDS OF PARTICLE EXPORT FLUXES AND PSD TRANSFORMATIONS FROM INVERSE MODELING. THESE DATA PRODUCTS AND MODELS WILL BE DISTRIBUTED TO THE EXPORTS SCIENCE TEAM AND BEYOND. OUR PROPOSAL RESPONDS PRIMARILY TO SECTION 3.1.2.2 (COLLECTION&ANALYSIS OF FIELD DATA) OF THE 2016 ROSES A3 SOLICITATION BUT ALSO CONTRIBUTES TO SECTIONS 3.1.2.1 (DEVELOPMENT OF RS DATA PRODUCTS) AND 3.1.2.3 (DEVELOPMENT OF MODELS). LAST THE LEAD-PI (SIEGEL) IS APPLYING TO BE THE EXPORTS SCIENCE LEAD., THIS PROPOSAL RESPONDS TO THE AMENDMENT A.3. OBB CALL FOR THE EXPORTS FIELD CAMPAIGN. USING SATELLITE REMOTE SENSING DATA TO PREDICT EXPORT AND FATE OF NET PRIMARY PRODUCTION (NPP) IN A GIVEN REGION AND TIME REQUIRES AN UNDERSTANDING OF THE DRIVERS AND CHARACTERISTICS OF PLANKTON COMMUNITY STRUCTURE. THE EXPORTS SCIENCE PLAN CHARACTERIZES 5 PATHWAYS FOR THE EXPORT OF NPP FROM THE SURFACE OCEAN INTO THE INTERIOR TWO OF WHICH ARE MEDIATED BY MESOZOOPLANKTON: PRODUCTION AND SINKING OF FECAL PELLETS AND ACTIVE TRANSPORT BY VERTICAL MIGRATION. WE PROPOSE TO ADDRESS EXPORTS SCIENCE QUESTIONS SQT (TA AND TB) AND SQ2 (2A B D) BY CONDUCTING FIELD-BASED PROCESS STUDIES OF MESOZOOPLANKTON-MEDIATED EXPORT IN THE NE PACIFIC AND N ATLANTIC OCEANS. THE GUIDING HYPOTHESIS IS THAT CHANGES IN PHYTOPLANKTON COMMUNITY STRUCTURE AND NPP AFFECT ZOOPLANKTON ABUNDANCE BIOMASS SIZE AND TAXONOMIC STRUCTURE ALL OF WHICH CONTROLS AND SCALES TO EXPORT IN A QUANTIFIABLE AND PREDICTABLE WAY. SATELLITE OBSERVABLES AND DATA PRODUCTS INCLUDING EUPHOTIC ZONE PHYTOPLANKTON BIOMASS AND FUNCTIONAL TYPE PARTICLE SIZE SPECTRUM LIGHT ATTENUATION AND TEMPERATURE WILL BE USED TO PREDICT ZOOPLANKTON COMMUNITY STRUCTURE AND IN TURN ZOOPLANKTON-MEDIATED EXPORT SIGNIFICANTLY ADVANCING OUR ABILITY TO PREDICT EXPORT AND FATE OF NPP., G8535509796
OpenAlex ID: W4313397282