Transcript marine ecology 2011--final lecture 7

Communities and Ecosystems
Summary
1)
2)
3)
4)
5)
6)
Communities have emergent properties
Two contrasting views of communities are the
superorganism and individualistic models
Two types of succession: primary and secondary.
Individual stages in a successional sequence are
seres, with final sere the climax
Many changes are seen in the types of organisms that
occur in various successional stages (e.g., r-selected
early on and K-selected near the climax)
Three succesional models are: facilitaiton, tolerance
and inhibition
The intermediate disturbance hypothesis predicts the
greatest species diversity when disturbances are
intermediate in size and intensity, and at intermediate
times between them.
Communities and Ecoystems
Summary
7) Top-down and bottom-up are two contrasting types of
controls of community structure
8) Species-area relationships show that for every 10 x
increase in area there is a doubling of species number
9) Four different explanations have been proposed to
explain species-area relationships
10) Island Biogegraphic Theory posits that a dynamic
equilibrium exists between extinction and immigration
11) The area and distance effects are major tenets of Island
Biogeography
12) Both ecological and evolutionary factors have been
proposed to explain the latitudinal species diversity
gradient
Communities and Ecosystems
Summary
13) Island biogeography has been used to make
recommendations for implementing conservation policy
14) Food chains are simple abstractions of food webs
15) Net production efficiency = (production / assimilation
16) Ecological efficiency is the energy available to trophic
level N + 1, divided by the energy consumed by trophic
level N
17) Only about 10% of the energy consumed by one
trophic level is available for the next
18) Pyramids of biomass can be inverted in marine
systems, but energy pyramids cannot
19) Humans have large effects on biogeochemical cycles
of C, N and P
Review Questions
Plankton Communities
Plankton are free floating and weak
swimmers whose position is determined
by water movements- phytoplankton and
zooplankton
Nekton are strong swimmers who are able
to determine the position regardless of the
water’s movements
Size Classification of Plankton
• Femtoplantkon - < 0.2 μm
• Picoplankton - 0.2 to 2 μm
• Nanoplankton - 2 to 20 μm
• Microplankton - 20 to 200 μm
• Macroplankton - 200 to 2000 μm
• Megaplankton - > 2000 μm
Size Classification of Plankton
• Femtoplankton – mostly viruses
• Picoplankton
phototrophic bacteria and cyanobacteria
prochlorophytes
heterotrophic bacteria
chemoautotrophic bacteria
eukaryotic picoflagellates
• Nanoplankton
heterotrophic nanoflagellates (HNANs)
small prokaryotic and eukaryotic phytoplankton
• Microplankton
prokaryotic and eukaryotic phytoplankton
heterotrophic flagellates and ciliates
most small zooplankton and larvae
Note: the size relationship between bacteria and a ciliate is like krill is
to a whale!
Plankton separated
into categories
based on their size.
Phytoplankton
Community Composition
Come in all shapes and sizes (morphology and size limitations)
single cells, chains, filaments
some are mixotrophic (both photo and heterotrophic)
Major Groups
Non-Motile
Motile (flagella)
Cyanobacteria
Diatoms
Chlorophytes Prasinophytes
Prymnesiophytes
Cryptophytes
Dinoflagellates
Euglenophytes
Chrysophytes (coccolithophorids
and silicoflagellates)
Phytoplankton
Diatoms have heavy silicified (pectin and amorphous silica)
frustules
• Are heavy than water, sink rapidly
• Usually the most abundant group (>80% of biomass) in
estuarine and near-coastal waters
From Sverdrup et al. 2004
Phytoplankton
Diatoms
Chaetoceros socialis
From Phytopia
Ditylum brightwellii
Chaetoceros debilis
Thalassionema sp.
Phytoplankton
Dinoflagellates
Have 2 flagella
Many species are mixotrophic
Most harmful algal species are dinoflagellates
From Sverdrup et al. 2004
Phytoplankton
Dinoflagellates
Protoperidinim divergens
Dinophysis sp.
From Phytopia
Harmful Algal Blooms
Brown Tide Blooms
Pfiesteria piscicida
Paralytic Shellfish Poisoning
Neurotoxic Shellfish Poisoning
Pseudonitszia
Amnesic Shellfish Poisoning
Phytoplankton
Microflagellates
Prasinophyceae
Chlorophyceae
Haptophyta
Chrysophyceae
Cryptophyceae
From Miller 2004
Phytoplankton
Picoplankton
• Are some of the smallest primary producers (0.2 – 2 µm dia.)
• Were not discovered until the early 1980’s
• Important contributors to oceanic primary production
• Are usually most abundant at the chlorophyll max in the open ocean
• Major groups are…
Cyanobacteria (Synechococcus)
Prochlorophytes (Prochlorococcus)
http://plantbio.berkeley.edu/~volkman/courses/MCB116Slides/Lec1Slide19.jpg
Picoplankton
DAPI DNA stain
Epifluorescent
Microscope
Under UV light
Particles contain DNA
DAPI DNA stain
Epifluorescent Microscope
Under blue light
Red cells are
Prochlorococcus
Yellow cells are
Synechococcus
Big yellow cell is a
dinoflagellate
Prochlorophytes
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
Very recently discovered,
prochlorophytes are extremely small
photosynthetic organisms that are the
most abundant plants (by cell #) on earth.
These tend to live in deeper waters near
the base of the sunlit layer.
Prochlorophytes
Chl a + b
b-carotene
Xanthophylls
Cryptophytes
Chl a + c
a-carotene
Phycobilins
Phytoplankton
• In most estuaries, Nanoplankton have the highest biomass and
primary production
• In oligotrophic habitats, Picoplankton have the highest biomass
and primary production
• Occasional blooms of Microplankton occur under nutrient enriched
conditions
Benthic Microalgae (microphytobenthos)
• Production: up to 2kg C m-2 yr-1
• Very high biomass: 0.1(?) kg C m-2
• Turnover (P/B): ~20(?)
In shallow waters benthic algae can be
suspended in the water column
and become part of the plankton
Coastal Phytoplankton
• Production: up to 0.5 kg C m-2 yr-1
• Low biomass: 0.02 kg C m-2
• HIGH Turnover (P/B): ~25
Cell densities up to 104-106 l-1 (Blooms)
Dinoflagellates: Naked and Armored
Chl a + c
b-carotene
xanthophylls (peridinin)
Shelf-Oceanic Phytoplankton
• Production: up to 0.1 kg C m-2 yr-1
• Very low biomass: 0.003 kg C m-2
• VERY HIGH Turnover (P/B): ~40
Cell densities up to 101-103 l-1 (Blooms)
Chl a
b-carotene
Phycobilins (phycocyanin)
Heterocyst
‘Blue-green algae
Trichodesmium
N2 fixation
23 Feb 1997
~50% Production trapped on the continental shelf
Abundances
General trends:
Phytoplankton most abundant near
coasts, decreasing with distance
Where seasonal effects are important
(higher attitudes), highest abundances
in springtime
Trends with distance
Species composition varies with
distance from land. Near-shore
waters dominated by diatoms.
Offshore waters have much higher
percentages of dinoflagellates and
coccolithophorids.
Note: This picture can change with
season and conditions.
Coccolithophores
CaCO3
The other~50% spread over vast ocean