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Plankton and Productivity

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Title: Plankton and Productivity


1
Plankton and Productivity
  • Phytoplankton
  • Diversity
  • Nutrients and light
  • Primary production
  • New production

2
Fig. 1. Examples of representative marine
eukaryotic phytoplankton
P. G. Falkowski et al., Science 305, 354 -360
(2004)
Published by AAAS
3
TrichoPicos
Trichodesmium tufts
N2-fixing cyanobacteria (Synechocystis) from
Station ALOHA (10 µm scale bar)
4
Diatom Diversity (4)
Top left Chaetoceros debilis spiny chain
diatom Bottom left Ditylum brightwelli Top
right Coscinodiscus granii NB Much of the
internal volume of the cell is filled by a
vacuole. Strands of cytoplasm can be seen
running through the vacuole.
Images from the Microscopy-UK Library
http//www.microscopy-uk.net/micropolitan/index.ht
ml
5
Emiliana huxleyi coccoliths
From the E. huxleyi site http//www.soes.soton.a
c.uk/staff/tt/eh//coccoliths.html
6
Emiliana huxleyi World
From the E. huxleyi site http//www.soes.soton.a
c.uk/staff/tt/eh/
7
Dinoflagellate Diversity (1)
Dinophysis Ceratium http//www.whoi.edu/science/
B/redtide/rtphotos/rtphotos.html
8
Dinoflagellate Diversity (3)
Citharistes sp. Arrow points to chamber
containing cyanobacteria.
Ornithocercus magnificus. Arrow points to girdle
list, which contains cyanobacteria. Inset shows
epifluorescence image with cyanobacteria
fluorescing orange-yellow.
Images from Carpenter 2002 Proc. Roy. Irish Acad.
120B 15-18.
9
Phytoplankton Growth
  • Specific growth rate
  • N(t) Noeµt
  • N biomass (cell number, PN, PC, etc.)
  • µ specific growth rate (t-1)
  • Note that µ really reflects the net growth rate
  • N(t) Noe(p-r)t
  • p specific production rate (t-1)
  • R specific respiration rate (t-1)

10
Marine N Limitation (Ryther Dunstan 1971)
Krebs, Fig. 25.08
11
Biolimiting Behavior NO3-
Data eWOCE Line A16. Figure prepared with ODV
12
North Atlantic Nutrient Ratios
Data eWOCE. Plot prepared with ODV
13
Redfield Ratio
  • The major nutrients occur in roughly constant
    ratios in deep water and in plankton.
  • Nutrients are removed from warm surface waters by
    plankton and released at depth by biological
    remineralization of organic matter.
  • The average ratio of nutrients is called the
    Redfield ratio after A.C. Redfield.
  • Biological activity drives the ocean to this
    state!

14
Nutrient Limitation N vs. P
  • The NP ratio of plankton is the same as the NP
    ratio of the deep ocean (Redfield ratio).
  • Since N P therefore enter the upper ocean in
    the same proportions as theyre required by
    phytoplankton, why does N appear to be limiting?
  • Food webs preferentially export N from the upper
    ocean.

15
Light in the Water Column
  • The deeper you go, the darker it gets

I(z) Ioe-kz
Mann Lazier Fig. 3.05b (left), Miller Fig. 3.3
(right)
16
P/I Relationship
Lalli Parsons Fig. 3.5
17
Stratification and Production
  • Size of circles reflects intensity of mixing.
    Note inhibition of mixing by the pycnocline (A
    C).
  • Light decreases exponentially and determines
    where phytoplankton become light-limited.
  • Below the euphotic depth, phytoplankton die.

MannLazier Fig.3.05
18
Production vs. Depth
Gulf of Alaska data for May (closed circles)
and September (open circles)
Miller, Fig. 3.9
19
Patterns in Primary Production
  • Above Typical annual cycles of primary
    production. Solid lines show phytoplankton
    biomass, blue lines show zooplankton biomass.
  • Left Schematic of relative abundance of light
    and nutrients at the sea surface as a function of
    latitude. Lines show relative seasonal change in
    primary production at three latitudes.

Lalli Parsons, Figs. 3.9 3.17
20
Riley-Sverdrup Bloom Model
  • Assumptions
  • Biomass uniformly distributed
  • P scales with I
  • R is constant
  • Compensation depth (Dc)
  • P R for individual phytoplankton.
  • Critical depth (Dcr)
  • Community between surface and Dcr in balance.
  • Blooms occur when Dcr gt Dmix.

Miller, Fig. 1.3
21
New vs. Regenerated Production
modified from http//www.up.ethz.ch/research/nitro
gen_cycle/index
22
Measurement of Primary Production
  • ?Biomass
  • Practical difficulties in separating
    phytoplankton from other components of the
    ecosystem.
  • Oxygen light-dark bottle method
  • The dark bottle measures community respiration.
  • The light bottle measures net community
    photosynthesis.
  • 14C Incorporation
  • The dark bottle provides ambiguous information.
  • The light bottle measures something near net
    production.
  • Long incubations may lead to recycling and
    equilibration.
  • Bottle effects may compromise all these
    approaches!

23
Distribution of Primary Production
  • Open ocean production dominates the budget
    despite the low areal rates.
  • Bottle effects may lead to underestimates in all
    environments, but especially in the open ocean.

24
Chl Distribution Atlantic
Composites Sep 97 - Aug 98
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