MNF-geow-B103 - Biologie für die Geowissenschaften (060627)

Prozesse mariner Primärproduktion

Prof. Dr. Anja Engel

GEOMAR

Marine Primary Producers Photoautotrophic organisms

Average net primary production and biomass of aquatic habitats. Data from R.H. Whittaker and G.E. Likens, Human Ecol. 1: 357-369 (1973).

Habitat Net primary Production

(g C/m2/yr)

Coral Reefs 2000

Kelp Bed 1900

Estuaries 1800

Seagrass Beds 1000

Mangrove Swamp 500

Lakes & streams 500

Continental Shelf 360

Upwelling 250

Open ocean 50

Planet of the Oceans 70% Earth surface

Topics of this lecture

• Light in the ocean

• Light limitation

• Nutrient distribution

• Limiting nutrients in the ocean

• Cellular release of primary production

• Fate and export of primary production

• Incoming Solar radiation (1360 watts m-2) is given by distance between sun and earth (1.5 x 108 km)

• > 50% is scattered and adsorbed in the atmosphere (clouds, aerosols, water vapor, CO2, O3, dust), 4% reflected from water surface

• Radiation depends on latitude; Typical values around Kiel Winter: 200 cal cm-2 d-1

Summer: 950 cal cm-2 d-1

Light and Primary Production

Zooplankton

The electromagnetic spectrum and light penetration in clear seawater

Visible light ~ photosynthetically available radiation PAR=300-720 nm

MNF-bioc-101, WS 2016/2017

Light attenuation in natural seawater

Id(z) = Id(0) e-kz

k: Attenuation coefficient (wavelenght specific) k= kw+kphy+kpa+kDOM

Kw: Attenuation coefficient of water Kphy: Attenuation coefficient of phytoplankton Kpa: Attenuation coefficient of other particles KDOM: Attenuation coefficient of DOM

10

SeaWiFS observes

El Niño / La Niña transition

January 1998

July 1998

chlorophyll-a concentration

NASA Ocean Biology Processing Group

Goddard Space Flight Center, Greenbelt, Maryland, USA

SeaDAS Training Material

CDOM is a major component and changes the underwater light climate

Terrestial CDOM (Gelbstoffe, humic acids)

Figure 6.18 Left: Attenuation of daylight in the ocean in % per meter as a function of wavelength. I: extremely pure ocean water; II: turbid tropical-subtropical water; III: mid-latitude water; 1-9: coastal waters of increasing turbidity. Incidence angle is 90° for the first three cases, 45° for the other cases. Right: Percentage of 465nm light reaching indicated depths for the same types of water. From Jerlov (1976)

Water types after Jerlov (1976)

Light Zones in the Ocean

Euphotic Zone: sufficient light for net growth of primary producers (<100m) Photic Zone: sufficient light to support protosynthesis (<200m). Disphotic Zone: insufficient light for primary production but sufficient light for animal response (<1000m) Aphotic Zone: no light of biological significance from the surface

DC = compensation depth:

Gross Primary Production = Respiration

in phytoplankton cells

DCR = critical depth:

Gross Primary Production ~ Loss

(Respiration, sinking, grazing) in the whole

plankton population

DM < DCR P > R

DM > DCR P < R

Assumption:

no limitation by nutrients

DC

DCR

DM

Gran (1931): Thermal stratification leads to onset of spring bloom (‘Gran effect‘)

Cummings (2001)

Development of a seasonal thermocline:

Mär

z

Apr

il

Mai

Juni Juli

Aug

.

Tief

e (m

)

Temperatur (°C) Temperatur (°C)

Tiefe (m)

Aug

.

Sept

.

Okt

ober

Janu

ar

November

Dezember

Mär

z

Apr

il

Mai

Juni Juli

Aug

.

Tief

e (m

)

Temperatur (°C) Temperatur (°C)

Tiefe (m)

Aug

.

Sept

.

Okt

ober

Janu

ar

November

Dezember

Example: Boknis Eck

Timing of spring bloom at Boknis Eck

But: short term-stratification can result in phytoplankton growth also in winter! other losses, e.g. grazing, can reduce PP during stratification does not apply for deepening of MLD (intrusion of nutrients)

Mixed Layer depth

J J J F M A S O N D M A

Phytoplanktonbiomasse

Nährstoffe Zooplanktonbiomasse

Durchmischungstiefe

PLANKTON Jahresgang - Plankton

Sverdrup-Model (1953)

Data: Ocean Weathership M (Norway)

Onset of phytoplankton bloom depends on thermal stratification

Photosynthetic production

nCO2 +2nH2Olight¾ ®¾¾ n CH2O( )+nO2 +nH2O

1. Capturing light energy and transferring it to chemical forms

2. Changing chemical forms into suitable metabolic forms (ATP and NADPH)

3. Fixing CO2 using ATP and NADPH

Physiological constraints of photosynthetic production

1. Light reaction

Converts light energy into chemical energy

Delivers reduction equivalents (NADPH/H+) and energy (ATP) for CO2 fixing

H2O splitting produces O2

2. Dark reaction (Calvin Benson Cycle)

Fixiation of CO2 by Rubisco

Reduction of the fixation product (3-Phosphoglycerat)

Regeneration of CO2-aceptor (Ribulose-1.5.bisphophat)

Phytoplankton pigments

• Chlorophyll-a (or its substitutes bacteriochlorophyll-a or divinyl-chlorophyll-a) is located in the reaction centers

• Three main types of accessory pigments: chlorophylls, carotenoids and biliproteins are located in the subantennae and light harvesting complexes (LHC)

or Light Harvesting Complexes (LHC)

In vivo whole cell absorption

Pure pigment in organic solvent

Antenna or Light-Harvesting Complexes (LHCs) and reaction centers (RC)

Photosynthesis rates (P) change with irradiance (I)

• P vs I curves are used to determine if cell growth is light limited or saturated

• Variability of P vs. I curves is affected by cell physiology

• P vs. I curves are used for modellling marine phytoplankton productivity

Physiological constrains of photosynthetic production

Photosynthesis vs. Irradiance ( P vs. I) curve

Light Intensity (mmol cm-2 d-1)

Net

Ph

oto

syn

thes

is R

ate

(mm

ol C

L-1

d-1

)

Initial slope, or quantum yield

Pmax

0

Iopt: Light at Pmax

inhibition

net production

respiration Ic: light at compensation point

Light limited Light saturation Photoinhibition

P vs. I curves differ between phyoplankton species, and depend on the physiology of the cell

Photoacclimation takes place at timescales of sec-days Mainy involved are changes in accessory pigment concentration & composition, changes in enzyme activity photoacclimation attempts to maintain a constant photosynthetic efficiency under a variety of light intensities

Photoacclimation: phenotypic response to variation in light

Photoadaptation: genetic change in response to light variance (mutation, species selection)

Species differ with respect to pigment type, biogeochemistry and/or enzymes assemblages/ activities at identical light conditions

The Story –

• 1870: Scientists discover that phytoplankton, not carbon

from land, supports marine food chain. Quantifying ocean

production and yields requires phytoplankton photosynthesis.

• 1890: Work begins on identifying limiting factors, keying

on phosphorous, trace metals and light.

• 1919 – 1944: First estimates of global ocean production

range from 22 to 126 billion tons of carbon. Field

measurements are largely based on oxygen, are sparsely

located, and have large uncertainties.

• 1952: Steemann-Nielsen introduces 14C method for

measuring photosynthesis in natural populations

• 1957: Ryther & Yentch adopt chlorophyll as index of

phytoplankton biomass and introduce chlorophyll-based

productivity modeling approach

• 1952 – 1989: Global ocean production estimated from 14C

ship data at 20 to 56 billion metric tons of carbon. Accuracy

limited by space and time coverage of measurements

1880

1890

1900

1910

1920

1930

1940

1950

1960

1970

1980

1990

2000

Phytoplankton

base of marine

food web

1952:Accurate measure of

phytoplankton photosynthesis

1978: NASA launches first

ocean color satellite to

measure global chlorophyll

1997: NASA launches SeaWiFS

1957: Chlorophyll-based

modeling introduced

First, crude ocean

production estimates

based on scant oxygen

data

1990 – 2003: Chlorophyll-based satellite algorithms give

ocean production estimates ranging from 44 to 65 billion

tons

From presentation of Michael Behrenfeld

(Oregon State University)

Primary Productivity: Definitions

• Gross Primary Productivity (GPP) – Rate of production of organic matter from inorganic

materials by autotrophic organisms

• Respiration (R) – Rate of consumption of organic matter (conversion to

inorganic matter) by organisms.

• Net Primary Productivity (NPP) – Net rate of organic matter produced (GPP – R).

Primary production is defined as the uptake of inorganic carbon : Primary production = mg or mmol carbon / m3 / day

A vertical profile of production measurements can be integrated to: Primary production = mg carbon or mmol / m2 / day

Net community production (NCP)

• NCP takes the total respiration of a plankton community into account

Primary Production Measurement

1. In vitro measurements (incubations)

O2; 14C, 13C

2. In situ measurements

DO2, DDIC, 18O

Light & Dark Incubation

Primary Production Measurement

1. In vitro measurements (incubations)

– O2; 14C, 13C,

Advantages 14C: high precision, dissolved and particulate PP, determines C directly Disadvantages 14C: radiotracer!, no clear separation between net and gross PP

Advantages O2: net PP, gross PP and respiration determined Disadvantages O2 : poor precision at low rates, O2:C conversion

dark bottle light bottle

Gross production (GP) to Net production (NP) depending on duration of incubation

Adsorption of tracer (control)

weight

14C- Primary Production Measurement

dark bottle light bottle

Gross production (GP) – R = Net production (NP)

Respiration (R)

weight

O2- Primary Production Measurement

According to Longhurst et al. (1995)

www.marineregions.org (figure by Nathalie De Hauware)

g C m-2 yr -1

NPP 45-50 Gt C yr-1 (Longhurst et al., 1995)

Estimating Marine Primary Production from Space

net P

P (g

C m

-2 yr -1)

Chlorophyll a

Surface distribution, annual mean

Surface Ocean Deep Ocean

Phosphate Phosphate

Nitrate Nitrate

Nutrients

• Nutrients: essential elements needed for cell

maintenance and growth (N, P, Si, etc.)

• Nutrients: biolimiting elements (down to ‘zero’

concentration at surface)

• Nutrients: in ocean water about 10,000 x less than on

land (“ocean desert”)

• 6 Nutrient elements comprise >95% of biomass

(C H O N S P)

Proteins

Carbohydrates

Nucleic Acids

C:N~3

C:N>100

C:N:P~10:4:1

Nucleotides (ATP) C:N:P ~4:2:1

Lipids C:N>>100

Phoshporlipids C:P~39:1

‘Hard Parts‘ = Biogenic minerals

Biogenic Calcium Carbonate

Calcite, Aragonite

(CaCO3)

Coccolithophores Foraminifera Pteropods Corals

Calcite Aragonite

Satelite images: Nasa; SEM pictures: G. Langer, S. Koch, AWI

Coccolithophores (E. huxleyi) in the Bay of Biscay

Bloom initiation Post-Bloom ‚white water‘

Calcareous ooze: Calcifying Plankton formed soft sediment

‘Hard Parts‘ = Biogenic minerals

Diatoms Radiolaria

Biogenic Silica (Bsi) ‘Opal‘

(SiO2•nH2O)

Sponges

DSi :

SiO2(OH)22-

SiO(OH)3-

Si(OH)4

SiO2•nH2O

BSi:

Siliceous ooze: Silicifying Plankton formed hard sediments

Micronutrients (Trace Elements)

e.g.,

Cu, Zn, Ni, Co, Fe, Mo, Mn

Generally, these are required to act as cofactors in enzymes

(Ferredoxin, Nitrogenase [Fe], Flavodoxin [Mn], Carbonic

Anhydrase [Zn])

Nitrogenase: needed for N2-fixation

Redfield, Ketchum and Richards (1963) showed strong and profound

relationships between dissolved elements that were consistent with the

growth and decomposition of phytoplankton:

C:N:P ~ 106:16:1 - Termed the ‘Redfield Ratio’

The Redfield Ratio

‘‘‘fixed‘‘‘ relationship between elements in nutrient and biomass

Diatom bloom

Biological partitioning of elements during

the growth of phytoplankton cells

Reciprocal Interaction between

dissolved inorganic elements

and

particulate organic elements

Engel et al. 2002

DOP

DON

• Nutrient stress: Physiological response of

the cell to nutrient deficiency

• Nutrient deficiency: lack of one element

versus another; related to stoichiometry

ratios

Chl a Concentration Surface Ocean

Nitrate Concentration Surface Ocean

High Nutrient Low Chlorophyll – Areas HNLC- Areas

Figure: P. Boyd

Martin & Fitzwater, 1988, Nature

Evidence of Fe-limitation in phytoplankton

"Give me a half a tanker of iron and I'll give you the next ice

age,“ John Martin (1993)

N- and Fe are the dominant proximate limiting nutrients

in the ocean

N2 Fixing Organisms in the Ocean

1. Marine Cyanobacteria

Mainly diazotrophic,

colony-forming pelagic bacteria with positive buoyance

2. Endosymbiontic bacteria in diatoms (Richelia spp.)

3. Unicellular cyanobacteria

The major pathways of the marine N-cycle

Trichodesmium spp., responsible For 25-50% of global marine N2-fixation

‘Puff‘

‘Tuft‘

Photo courtesy of Pernilla Lundgren and Birgitta Bergman, Stockholm University

Baltic Sea Cyanobacteria

Cyanobacteria bloom

Picture: ioc.unesco.org/gpsbulletin/GPS1&2/Vol2ar1.jpgA

Baltic Sea Cyanobacteria

www.io-warnemuende.de/research/images/cyanophyceae/aphafloz.jpgBaltic

Heterocyst = N2-fixing cell, contains Nitrogenase, PS I Produces neurotoxins:

Anatoxin, Saxitoxin

www.io-warnemuende.de/research/images/cyanophyceae/noduspu.jpg

Heterocyst = N2-fixing cell, contains Nitrogenase, PS I

produces hepatoxin Nodularin

Growth kinetics

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 100 200 300 400 500

Light-Limited Growth

Gro

wth

rate

(d

-1)

Irradiance (µmol m-2 s-1)

0.0

0.2

0.4

0.6

0.8

1.0

0 2 4 6 8 10

Gro

wth

Ra

te (

d -1)

Scaled Nutrient Concentration

Nutrient-Limited Growth

- Sensitive region where growth rate directly responds to increase - Saturating region where growth rate does not change

Effects of Nutrient Concentration: Michaelis-Menten Kinetics

V = Vmax ×S

K s + S

0.0

0.2

0.4

0.6

0.8

1.0

0 2 4 6 8 10

Gro

wth

Ra

te (

d -1)

Scaled Nutrient Concentration

Nutrient-Limited Growth

V max

Ks

Growth kinetics are difficult to determine when

Ks is very low

Ks < 0.1 µg L-1

Because nutrient uptake equals nutrient content in cell it

is easier to measure the Cell Quota

from Droop, in McCarthy, 1981

Algal growth could be described as a function of internal stores of a limiting nutrient.

Nutrient-uptake

kinetics and

Species selection

It was demonstrated that phytoplankton isolated from oceanic

environments had lower Ks values than phytoplankton from coastal

seas (MacIsaac and Dugdale, 1969)

0.0

0.5

1.0

1.5

2.0

2.5

0 2 4 6 8 10 12

Nutrient Uptake

Specifi

c R

ate

of U

pta

ke (d

-1)

Nutrient Concentration (µM)

I

II

Vmax

= 2.25 d-1

Ks = 2.0 µM

Vmax

= 1.5 d-1

Ks = 0.5 µM

Typical ks Values Area Ks (ug/L)

Nitrate Ks (ug/L) Ammonia

Reference

Tropical Pacific, oligotrophic

0.01-0.21 0.1-0.6 MacIsaac & Dugdale (1969)

Tropical Pacific, eutrophic

0.98

Subarctic Pacific, eutrophic

4.21 1.3

Oceanic diatoms 0.1-0.7 0.1-0.4 Eppley et al. 1969

Coastal diatoms 0.4-5.1 0.5-9.3

Littoral flagellates

0.1-10.3 0.1-5.7