6 June 2011ACE workshop 1 Ocean Productivity: Concepts and Measurements John Marra Brooklyn College, CUNY

6 June 2011ACE workshop 2 The Major Goal of Biological Oceanography: “…determination of time-varying plankton productivity in the world ocean…” -Barber and Hilting (2002)

6 June 2011ACE workshop 3 Productivity Autotrophs, heterotrophs New production Export Production Concepts

6 June 2011ACE workshop 4 Rate of photosynthesisGross primary production, GPP GPP - autotrophic respiration Net primary production, NPP NPP - heterotrophic respiration Net community production, NCP Export Production, EP, the amount of NCP exported (sinking, mixing, ZP vertical migration) to depth Productivity Defined Process Ecological Term New Production, NP, the fraction of NPP supported by ‘new’ nutrients, and available for export

6 June 2011ACE workshop 5 Photosynthesis Carbon dioxide WaterSugarsOxygen + + The Photosynthetic Quotient, or PQ is the amount of oxygen evolved relative to the carbon fixed into organic matter

6 June 2011ACE workshop 6 Synthesis of Energy from Light

6 June 2011ACE workshop 7 Productivity Measurements Two choices: –Fluxes from in situ dynamics –Fluxes occurring in bottles Each has advantages and disadvantages

6 June 2011ACE workshop 8 The kind of ‘container’ Very physically dynamic in situ volumeVery non-dynamic volume

6 June 2011ACE workshop 9 Oxygen CO 2 + H 2 O -> CH 2 O + O 2 The change in oxygen content in a defined quantity of water is the most straightforward measure of Net Community Production. The problems: 1.All too frequently, the change is negative (NCP <0) over 12 or 24 h; 2. Requires an accurate air-sea exchange

6 June 2011ACE workshop Oxygen CO 2 + H 2 18 O -> CH 2 O + 18 O 2 A good estimate of Gross Primary Production, but may be influenced by the Mehler reaction, or other oxygen consuming reactions within the phytoplankton cell.

6 June 2011ACE workshop 11 Carbon CO 2 + H 2 O -> CH 2 O + O 2 It’s carbon! (no worries about value of the the photosynthetic quotient), but… Precision is too low for most open ocean work

6 June 2011ACE workshop Carbon Basis of virtually all satellite algorithms for productivity Incubation from dawn-dusk very close to Net Primary Production Characteristics invite methodological abuse and carelessness –Easy –Extremely Sensitive –Always gives a ‘positive’ answer 14 CO 2 + H 2 O -> 14 CH 2 O + O 2

6 June 2011ACE workshop 13 “…the results of the 14 C method fall somewhere between the net phytoplankton production and total photosynthesis, but exact evaluation of the meaning of the experiments will require an extensive experimental programme” G. A. Riley (ca. 1954)

6 June 2011ACE workshop 14 Productivity has known limits 1. Growth rate as a function of temperature (Eppley,1972) 2. The maximum rate of photo- synthesis normalized to chlorophyll-a, P b max, will be ≤ 25 (Falkowski, 1981) 3. The quantum yield. 8 quanta of light are required to evolve 1 mol O 2, thus, the quantum yield will be < 0.1 (in practice) (e.g., Bannister and Weidemann, 1983)

6 June 2011ACE workshop 15 Biomass: Changes in POC Good for estimating particle production Doesn’t measure DOC production There are many more optically-based measurements of production in development

6 June 2011ACE workshop 16 Comparing Fluxes: In Situ and in Containers

6 June 2011ACE workshop 17 The JGOFS North Atlantic Bloom Experiment, Spring 1989 Over 13 days (mixed layer): Production = 970 mmols C m -2 Total increase in POC = 520 mmols C m -2 Trap flux = 507 mmols C m -2 (234 Th estimates are about half the trap flux.) m

6 June 2011ACE workshop 18 N interacts with C in the concept of New Production NO 3 N2N2 The amount of production fueled by NO 3 or N 2 and called the f-ratio Best for temperate, and high-latitude areas subject to seasonal mixing, and supply of NO 3 from depth A good way to evaluate the quantity of production exported to depth

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6 June 2011ACE workshop 20 Export Production in Time ‘bottom up’ regulation ‘top down’ regulation grazing

6 June 2011ACE workshop 21 Export Flux to Depth

6 June 2011ACE workshop 22 The role of Iron Boyd et al., 2007

6 June 2011ACE workshop 23 Next steps: What we don’t know Production and dynamics of dissolved organic matter (DOM) Respiration and its components The depth of the Euphotic Zone Production in large, permeable, diffusive containers in terms of small, impermeable ones, and vice versa

6 June 2011ACE workshop 24 DOM Mixing/advection hydrolysis/ diagenesis Riverine inputs solubilization, grazing, exudation, lysis, Net Primary Production EXCHANGE OPEN OCEANCOASTAL OCEAN DOM solubilization, grazing, exudation, lysis, adapted from Moore 1999 CO 2 DIC SEDIMENTS Dissolved Organic Matter DOM long term C reservoir Mixing/Advection DIC Surface Deep Net Primary Production CDOM

6 June 2011ACE workshop 25 Phytoplankton Primary Production DOM CO 2 Bacterial remineralization extracellular release, grazing, lysis, solubilization inorganic compounds CO 2 Bacterial remineralization Advection Lateral transport bioavailability Estimated that 50% of primary production routed through dissolved fraction Not typically measured in measurements of productivity –O 2 evolution/CO 2 consumption will include it, – 14 C uptake may not –Won’t be measured in particle production methods Ultimately comes from photosynthesis (like everything else) Utilization of labile DOC will be as rapid as photosynthetic production Export to deeper waters & sediments through aggregate and particulate sinking

6 June 2011ACE workshop 26 AUTOTROPH BACTERIAL RESPIRATION DISSOLVED ORGANIC MATTER EUPHOTIC DEPTH

6 June 2011ACE workshop 27 Global Ocean Productivity Through the ‘Ages’

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6 June 2011ACE workshop 29 Cast of Characters

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