Measurements and Distributions of Biomass

Matthew Church OCN 621 Spring 2010 Food web structure is a key determinant on carbon fluxes:

1) Cell size and geometry influence sinking rate 2) Zooplankton repackage material and vertically migrate 3) Small cells support longer food webs = more carbon

recycled to CO2 Zooplankton repackage plankton into rapidly sinking fecal material

Sedimentation of diatom‐rich salp fecal pellets > 1 mm long, 350 µm wide, 10 µg C per pellet‐‐‐these things sink FAST... Direct aggregation and pulsed export is also important

Flux of labile phytodetritus to the deep North Atlantic Important things to know about ocean ecosystems

• Population size and biomass (biogenic carbon): provides information on energy available to support the food web

• Growth, production, metabolism: turnover of material through the food web and insight into physiology.

• Controls on growth and population size

“Microsystems”

In every liter of seawater there are all the organisms for a complete, functional ecosystem. These organisms form the fabric of life in the sea - the other organisms are embroidery on this fabric. In a “typical” liter of seawater… •Fish None • Zooplankton 10 • Diatoms 1,000 • Dinoflagellates 10,000 • Nanoflagellates 1,000,000 • Cyanobacteria 100,000,000 • Prokaryotes 1,000,000,000 • Viruses 10,000,000,000 High abundance does not necessarily equate to high biomass. Size is important.

1011 1010 Viruses 109 Bacteria 108 Cyanobacteria 107 106 Protists 105 104 103 102 101 Phytoplankton 100

Abudance (number per liter)Abudance -1 10 Zooplankton 10-2 0.01 0.1 1 10 100 1000 Size (µm) Why are pelagic organisms so small?

Consider a spherical cell: SA = 3.1 µm2 SA= 4πr2 r = 0.50 µm V = 0.52 µm3 SA : V = 15.7 V= 4/3 πr3

SA = 12.6 µm2 r = 1.0 V = 4.2 µm3 SA : V = 3.0

The smaller the cell, the larger the SA:V Greater SA:V increases their ability to absorb nutrients from a dilute solution. This may allow smaller cells to out compete larger cells for limiting nutrients. • “Typical” concentrations of inorganic nutrients in the open sea: – Subtropical North Pacific: • Nitrate+nitrite 1-10 nM (0.001-0.01 µM) • Phosphate 10-40 nM (0.01-0.04 µM) • “Typical” concentrations of inorganic nutrients in soils: • Nitrate+Nitrite 5-100 µM • Phosphate 5-30 µM Why do we care about biomass?

• Information on biologically stored energy • Quantify the amount of carbon held in marine biota (carbon budgeting purposes) • Identify how much “material” is available to at each step of the food chain. Primary producers

Primary consumers (herbivores)

Secondary consumers (carnivores)

Tertiary consumers Biomass (mg C L-1) The way biomass is distributed among trophic levels in the food web provides clues to the efficiency of energy transfer through the ecosystem .

Note: this is a static depiction-it does not provide information on how fast biomass turns over within each trophic level. The elemental composition of a typical bacterium Substrate Element % dry Cellular Components Source

C 55 DOC, CO2 Main constituent of cellular material Constituent of cell material and cell

O 20 O2, DOM, CO2 water; O2 primary electron acceptor in aerobic respiration NH , NO -, NO -, Constituent of amino acids, nucleic N 10 3 3 2 DON, N2 acids, nucleotides, and coenzymes Main constituent of organic compounds H 8 DOM, H 2 and cell water Constituent of nucleic acids, P 3 PO 3-, DOP 4 nucleotides, phospholipids, LPS Constituent of cysteine, methionine, S1SO, H S, HS, DOM 4 2 glutathione, several coenzymes Main cellular inorganic cation and K 1 Potassium salts cofactor for certain enzymes Inorganic cellular cation, cofactor for Mg 0.5 Magnesium salts certain enzymatic reactions Inorganic cellular cation, cofactor for Ca 0.5 Calcium salts certain enzymes Component of cytochromes and Fe- Iron salts, Fe 0.002 proteins; cofactor for many DOM enzymes The Struggle for Composition

2 10 •Plankton are 101 Mg S 100 Ca K relatively enriched in 10-1 C P, N, C, Fe compared 10-2 to the surface 10-3 seawater. 10-4 10-5 •Energy must be 10-6 P N expended to acquire 10-7 10-8 and maintain 10-9 intracellular % surface ocean % surface Fe 10-10 concentrations of 10-11 these elements. 10-3 10-2 10-1 100 101 102 % cell composition How do we measure plankton biomass?

• Count and measure individuals and calculate carbon • Weigh (either dry or wet) cells and calculate biomass • Estimate living carbon using some biomolecule proxy (DNA, ATP, chlorophyll) Particulate carbon

• Technique: combust (oxidize) organic material

and measure resulting CO2. • Need to concentrate cells: typically glass filters (usually ~0.7 µm pore size) or tangential flow (Fukuda et al. 1998) • Measurements include living cells and detritus. Zooplankton • Small zooplankton are usually enumerated by microscopy and converted to cell carbon • Larger zooplankton can be weighed for approximation of carbon.

Primary consumers (herbivores)

Secondary consumers (carnivores) Phytoplankton carbon

• Phytoplankton carbon determinations are most often derived from measurements of chlorophyll; this requires a conversion factor. • Phytoplankton carbon can also be estimated based on cell size and abundances (microscopy and/or flow cytometry).

Primary producers Light harvesting photosynthetic pigments

• Chlorophylls • Carotenoids • Biliproteins

• Recently discovered photoreceptor proteins (Proteorhodopsin and Bacteriorhodopsin) serve as proton pumps, but do not appear to harvest energy for oxygenic photosynthesis. Chlorophylls

• Cyclic tetrapyrole with a magnesium atom chelated in Chlorophyll c lacks the phytol the center of group the ring Phytol • All oxygen evolving photosynthetic plankton contain Chlorophyll a (peak absorption 450 and 660 nm)

• Chl a, b, and c all absorb strongly in the red (between 440-450 nm) and blue wavelengths (~645-660 nm). The presence of Chl b and c increases the absorption between 450-650 nm. Carotenoids The double bonds absorb strongly in the short wavelength region of the visible spectrum • Isoprenoid compounds (lipids)- not water soluble.

• Almost all chlorophyll and carotenoids occur as complexed proteins. Carotenoids

• Photosynthetic carotenoids participate in photosynthetic electron transport . • Non-photosynthetic carotenoids appear to protect photosynthetic reaction centers from oxidation via free radical scavenging Phycobiliproteins

• Water soluble pigments that capture light energy and pass the energy to chlorophyll.

• Found in Rhodophytes (red ), Cryptophytes, and Cyanobacteria – Red: phycoerythrin (red algae, often in cyanobacteria); phycoerythrocyanin – Blue: phycocyanins, allophycocyanins

• Occur as aggregates, termed phycobilisomes, composed of 3 or more phycobiliproteins Phytoplankton

• Phytoplankton include single cells or organized colonies; the vast majority are very small (<10 µm): – Picoplankton: 0.2-2.0 µm – Nanoplankton: 2.0-20 µm – Microplankton: 20-200 µm

The picoplanktonic photosynthetic cyanobacteria comprise a substantial component of plankton biomass and production in low nutrient systems. Major divisions and classes of photosynthetic plankton in the ocean • Prokaryotes – Cyanobacteria

• Eukaryotes: – Chlorophyta (green algae); include the following classes: 1 µm • Chlorophyceae Micromonas • Prasinophceae • Euglenophyceae

– Chromophyta (brown algae); include the following classes: • Chrysophyceae Pelagomonas • • Prymnesiophyceae • Bacillariophyceae (diatoms) • Dinophyceae (dinoflagellates) • Cryptophyceae (crytophytes) • Phaeophyceae (phaeophytes)

– Rhodophyta (red algae)-mostly macrophytes Marine cyanobacteria

Prochlorococcus • Cyanobacteria: major groups of cyanobacteria in the oceans include: Prochlorococcus, Synechococcus, Trichodesmium, Crocosphaera, Synechococcus Richelia

– Wide range of morphologies: unicellular, filamentous, colonial

– Some species fix N2

Richelia Trichodesmium Many images from: http://www.sb-roscoff.fr/Phyto/gallery/main.php?g2_itemId=19 Chlorophyta (green algae)

• Chlorophytes • Prasinophytes – Contain Chl b – Contain Chl b Nannochloris – Uncommon in – Predominately open ocean; unicellular mostly – Relatively freshwater. common, but not – Can be single abundant in cells or colonies, ocean coccoid or – Can be single flagellated cells or colonies, coccoid, biflagellated, or quadri-flagellated

Prasinophyceae Chromophyta (brown algae)

• Pelagophytes • Chrysophytes • Cryptophytes – Contain Chl c – Contain Chl c – Contain Chl c – Very common in – Relatively rare in – Contain open ocean. open ocean carotenoid – Coccoid or – Mostly bi- alloxanthin monoflagellated flagellated – Contain (flagella of phycoerythrin or unequal length) phycocyanin – Flagellated unicells

Pelagomonas

Dictyocha Rhodomonas salina

Images from: http://planktonnet.sb-roscoff.fr/index.php#search Chromophyta (brown algae)-Cont.

• Prymnesiophytes • Bacillariophytes • Dinophytes – Mainly – Ubiquitous – Possess the biflagellates – All contain Chl c and carotenoid peridinin – Very common carotenoid – Widely distributed in open fucoxanthin (estuaries, open ocean – Rigid silica- ocean)

–2-5 µm impregnated cell SkeltonmacsuD: 10/6OwrGyAdi – Mostly unicellular – Some wall and autotrophic, species form – Many form colonies but colorless heterotrophs can CaCO3 plates – 2 prominent cell (coccoliths) also be abundant morphologies: centric 3 votes4.N/A and pennate – 2 flagella – Many are bioluminescent and some case toxic red tides blooms

Emiliana huxleyi Coscinodiscus Rhizosolenia Rhodophyta (Red Algae)

• Rhodophytes – In addition to Chl a, also contain phycoerythrin, phycocyanin, allophycocyanin – Most marine Porphyridium representatives are macrophytes Rhodella Carotenoids and biliproteins extend the spectral region able to support plankton growth; thus light forms an important environmental control on microorganism evolution. Carbon to Chlorophyll Conversions • Chlorophyll concentrations can vary depending on physiological and environmental history of the cells NAB Arabian Sea

Eq-Pac HOT

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Depth (m) How much 150 detritus?

200 0 1000 2000 3000 4000 0 5 10 15 20 25 0 500 1000 1500 2000 Chlorophyll a (ng L -1) Particulate Carbon (µmol L -1) C: Chl (mg : mg) ATP as an indicator of biomass

• All living cells contain ATP • ATP degrades rapidly after cell death • ATP:C ratio appears well conserved • ATP:C ~250:1 (mg : mg) • Non-discriminate, includes all living material Euphotic zone typically ~30-75% of particulate material contains ATP. Determining Biomass by Microscopy

• Filter seawater onto polycarbonate filter or concentrate cells by settling (large phytoplankton) • Stain cells • Visualize cells by light and/or fluorescence microscopy • Count cells and measure cell sizes • Use conversion factors to calculate carbon Application of flow cytometry to abundance/cell sizing “Typical” bacterial cell densities in aquatic ecosystems

Habitat Cell density (cells ml-1) Estuaries >5 x 106

Coastal (near shore) 1-5 x 106

Open Ocean 0.5-1 x 106

Deep Sea <0.01 x 106 Planktonic biomass generally declines with increasing depth-why?

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200

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600 Depth (m) 800 Phytoplankton Bacteria Total Biomass 1000

0246810 Biomass (µg C L -1) Important exceptions to the logarithmic decline in biomass with depth Clearly distinguishable ocean habitats with elevated “plant” biomass in regions where nutrients are elevated In the ocean gyres, chlorophyll concentrations are low in the surface water, greater at depth (80-150 m). In contrast, most of the production (=synthesis of biomass) occurs in the well- lit upper ocean. Spatial discontinuities at various scales (basin, mesoscale, microscale) in ocean habitats play important roles in controlling plankton growth and distributions.

Yoder, 1994 45oN

25oN

5oS

Buck et al. (1996) Bacterial and phytoplankton biomass in the upper ocean in various ecosystems

Location Bacterial Biomass Phytoplankton Bact:Phyto (mg C m-2) Biomass (mg C m-2) Sargasso Sea 659 573 1.2

North Atlantic 500 4500 0.11

Subarctic North 571 447 1.2 Pacific Station ALOHA 750 447 1.7

Arabian Sea 724 1248 0.58

Average 641 1443 0.96 Stand dev. 105 1740 0.62 CV (%) 16% 120% 64% Bacterial biomass constitutes a large pool of living carbon in marine ecosystems. Note greater variation between ecosystems in phytoplankton biomass relative to bacterial biomass. Bacterial biomass calculated assuming 10 fg C cell‐1; phytoplankton biomass calculated assuming C:Chl of 50:1. Plankton biomass relationships

• Biomass pyramids in large areas of the open ocean appear inverted, with secondary producers comprising a major fraction of ecosystem biomass.

Gasol et al. (1997) Plankton biomass relationships

• Over wide range of aquatic ecosystems, bacterial biomass appears correlated with phytoplankton biomass.

• Bacterial biomass is generally less variable than phytoplankton biomass across large gradients in productivity.

• With increasing oligotrophy, bacterial biomass becomes a proportionality larger fraction of total plankton biomass. An inverted food web in low productivity ecosystems?

Primary producers

Primary consumers (Bacteria)

Secondary consumers (microzooplankton)

Tertiary consumers (mesozooplankton)

How is this biomass pyramid sustained? Rapid turnover of phytoplankton biomass.