Marine pelagic ecology BIO 4400

Phytoplankton and primaryproduction-1

Bente Edvardsen 2009ka

Literature (Pensum):

Chap. 13, 14 in Garrison

Chap. 5 in Skjoldal

p. 3-50 in Paasche (or Chap 2 in Kaiser et al.)

Aims of learning - marine botanyGive an understanding and knowledge on:• Ecological role of phytoplankton• Primary production, photosynthesis and growth• Effects of ecological factors: light, nutrients,

temperature, salinity • Distribution in time and space• Ecological strategies• Phytoplankton diversity

Content

• Phytoplankton size groups• Primary production• Light• Photosynthesis and effect of light• Nutrients (C, N, P and Si)

Phytoplankton (Planteplankton)

Most are microscopically small, drifting, single celled algae. They are small to float and to have an efficient nutrient uptake. Some live in colonies.

Photo: Jahn Throndsen (JT)

Size variation of phytoplankton

The size of phytoplankton:< 2 µm picoplankton2-20 µm nanoplankton20-200 µm microplankton200-2000 µm mesoplankton

Plankton and size-groups

(Sieburt 1978)

Microplankton (20-200 μm)

CeratiumDinophysis

Guinardia

dinoflagellates diatoms

JTJT

Nanoplankton (2-20 μm)

ChrysochromulinaEmiliania huxleyi

haptophytes

cryptophytes

Identification in electron microscopy often needed

JT

Picoplankton (0.2-2 μm)

Micromonas pusilla

Prokaryota Eukaryota

Prochlorococcus

Synechococcus

Phytoplankton as primary producers

Half of the Earth’s primary productivity is by marine microbes

Phytoplankton

bacteria

protists

zooplankton

From Paasche 2005

Nutrition in microalgae (trophy)

• autotrophy: use CO2 as carbon source and light as energy• auxotrophy: autotrophy, but need some

organic compounds e.g. vitamins• heterotrophy: use organic carbon as

carbon source • phagotrophy: nutrition from organic particles• osmotrophy: nutrition from dissolved organic

material (DOM)• mixotrophy: both autotrophy and

heterotrophy

Primary production - definition

Formation of organic matter through assimilation of inorganic elements through photosynthesis or chemosynthesis

Photosynthesis

light6CO2 + 6H2O + -> C6H12O6 + 6O2

Garrison, Fig 13.2

Chemosynthesis in chemolithotrophic bacteriae.g. in sediments

Garrison, Fig 13.4

Chemolithotrophic bacteria

Beggiatoa is a sulfur-oxidizing bacteria

Keiser et al. Fig 2.7

Primary production in the sea

• phytoplankton 90-96%• benthic algae 2-5%• chemolithotrophic bacteria 2-5%

• c. 50 . 109 tonnes C per year in the sea• c. 60 . 109 tonnes C per year on land

• biomass 1-2 . 109 tonnes in the sea• c. 800 109 tonnes on land

Primary production:Carbon assimilationper area (or volume) and per time unit

Absolute units:g C· m -2 · day-1 (or y-1)or g C· L-1 ·h-1

Specific units:

g C· C-1 · day-1Garrison, Fig 13.5

Effect of environmental factors on primary production

• Light reaction in the photosynthesis: light, CO2

• Dark reaction (production of sugar, then lipids and proteins): nutrients and temperature

Photosynthesis:

RUBISCO

RUBISCO= Ribulosebiphosphate carboxylase/oxygenase

Light reaction

dark reaction

Calvin - Bensoncycle

Radiation (stråling) – visible light

Energy E, E= h f or E=hc/ λwhere f is frequency h is Plancks constant, c is light speed and λ (lambda) is wavelength of irradiance

Units for irradiance (innstråling)

Paasche Fig. 1

Irradiance varieswith latitude and through the year

Paasche 2005, Fig. 2 og 3

Light in the sea

Spectral distribution in water

Skjoldal

JT03

Light attenuation in water

Attenuation(svekking) of

light in varioustypes of water

Paasche Fig. 6

Pure sea water

Coastal water

Irradiance(Innstråling)

Euphotic zone = the well lit zonewith enough lightfor growth

Approx. 1% lightdepth (the depth where 1% ofsurface light remains)

Garrison, Fig 13.15

PigmentsAlgae can utilise irradiance of wave

lengths 350-700 nm = PAR photosynthetically available radiation≈ visible light (400-700 nm)

PS I + II: chlorophyll a

Accessory pigments:chlorophyll b, c• carotenoids (carotenes , fucoxanthin

etc, xanthofylls)• Phycobiliproteins (phycoerythrin,

phycocyanin, allophycocyanin)

“Sunglass pigments”:• carotenoids (diatoxanthin,

diadinoxanthin, zeaxanthin)WE

Photo: Wenche Eikrem

Absorption spectrum for chlorofyll a

= the amount of absorbed light at various wave lenghts

Absorption spectrum for some accessorypigments

they fill inn some of the “optical window”

Absorptionspectra and

action spectra

= photosynthesis(O2 development) at various wavelengths)

dinoflagellate

diatom

Sea lattice

kelp

Photosynthsis as a function of irradiance(P/E curve)

P photosynthesis

R respiration

I (=E) irradiance

Ik saturation irradiance

Ic compensation irradiance

Pmax light saturated photosynthesis

N nett

B gross

P/E curve

PBmax: Light saturated photosynthesis per biomasse (measured

as chlorophyll a)

α shows how efficient P is

Photoacclimation

High light adapted

Low light adapted

Irradiance

Photosynthesis vs. light and depth

DC = compensation depth

photosynthesis=respiration

photoxidation

average DC ≈ lower limit for euphotic zone

Compensation and critical depth

Euphotic zone

Kaiser et al.

Effect of environmental factors on primary production

• Light reaction in the photosynthesis: light, CO2

• Dark reaction (production of sugar, then lipids and proteins): nutrients and temperature

Elemental composition of algal cells

99% of the living biomass is made up of C, H, O and N

Dissolved inorganic carbon in sea water

Carbon dioxide• At 35 PSU and pH 8.2, 90% of inorganic

carbon occurs as HCO3-

• This is converted within the cell to CO2

• The supply of inorganic C for photosynthesis is rarely limiting in marine systems