Apr 1, 2013:
Properties of seawater that influence conditions experienced by biota
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High density fluid
Charged molecule (with high density = viscous)
Solubility: of ions; of gases – oxygen and carbon dioxide
High light extinction coefficient
High heat capacity
Intertidally, desiccation and wave force
Tides
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occur due to joint gravitational force of sun and moon.
The moon’s orbit around the earth is 25 days, therefore patterns in the tidal cycle recur at this
frequency. Tides progress each day by 24.8 hours.
Spring tides occur every 2 weeks because they are driven by alignment of sun and moon on
either the same or opposite sides of the earth. Neap tides occur when sun and moon do not
align.
slack
Amplitude
ebb
flood
Mean range includes all
highs and lows
Mean semidiurnal range
includes all higher highs
and lower lows
1 semidiurnal tidal cycle of 25 hr
Chart datum =Mean lower low water
calculated over many years
Apr 3, 2013 – Habitats
Intertidal (eulittoral) zones (Kozloff 1983)
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1: supralittoral fringe affected only by higher tides; upper portion wet only from spray or rain
(>7-9’ MLLW in Puget Sd)
2: Upper midlittoral zone (4-7’ MLLW in Puget Sd) = above mean tide level; rockweed on hard
substratum
3: Lower midlittoral zone (0-4’ MLLW in Puget Sound) = below mean tide level; mussels on hard
substratum
4: Infralittoral fringe below MLLW to the most extreme low tides; algae in particular
“frustratingly rich for a beginner”
Dethier habitat types:
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Marine = salinity 33
o Intertidal (rock, boulders, hardpan, cobble, mixed-coarse, gravel, sand, mixed-fine, mud,
organic, artificial, reef)
o Subtidal (bedrock and boulders, cobble, mixed coarse, gravel, mixed-fine, mud and
mixed-fine, organic, artificial, reef) = below extreme lower low water
Estuarine = salinities 0.5 to 30
o Intertidal (bedrock, hardpan, mixed-coarse, gravel, sand, mixed-fine, mixed-fine and
mud, mud, organic, artificial, reef)
o Subtidal (bedrock-boulder, cobble, mixed-coarse, sand, mixed-fines, mud, sand and
mud, organic, artificial, reef)
Environmental factors determining habitat type:
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Freshwater input: mid-estuary organisms do not necessarily need to tolerate moderate salinity,
but rather variable salinity. Why is this challenging? Are there estuarine-adapted species or not?
Water motion, wave action, morphodynamic state: Rapidly-moving water carries larger
particles; in slow-moving water, larger particles drop out because gravity exceeds resuspension.
p. 229 Boundary layers
Free stream
Logarithmic layer
Laminar sublayer (or Not if turbulent)
No slip conditions = water does not move
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Wetness/dryness, Emersion time: Paradigm is that upper limit of organisms is determined by
physiological tolerance to heat and desiccation, and lower limit is determined by species
interactions.
April 8, 2013 – Primary production
1. Basic photosynthesis and respiration relationships
6CO2 + 6H20 + energy <-> C6H12O6 + 6O2
2. Primary producers in the ocean
Bacteria
Some flagellates
Incl. coccolithophores
Incl. foraminifera
Dinoflag., Ciliates
Diatoms, Brown algae
Some amoebae
Animals
Fungi
Rhodophyta
Green algae+ land plants
3. Light in water (another habitat axis)
a. Extinction coefficient = exponential rate at which light energy declines with depth,
influenced by… organisms, DOM, bubbles, turbidity
b. Light quality = red wavelengths are absorbed, whereas blue wavelengths penetrate
(exception – CDOM from rivers reflects red light)
4. Photosynthesis dynamics –
a. CHECK p. 65-66 for variable names; Michaelis-Menten equation for gross
photosyntehsis: 𝑉 =
𝑉𝑚𝑎𝑥×[𝑆]
[𝑆]+𝐾𝑚
1
𝐾𝑚
1
1
and as inverses 𝑉 = 𝑉𝑚𝑎𝑥 × 𝑆 + 𝑉𝑚𝑎𝑥.
b. Plants respire, therefore negative net photosynthesis in low light or darkness
c. PS rates plateau with high inputs (of light or CO2), likely as RUBISCO saturates
5. Definitions of productivity terms
a. Instantaneous individual-level variables:
i. Compensation point is light level at which net photosynthesis = 0
b. Integrated (day-night) individual-level variables:
i. Compensation depth is the bottom of the (eu)photic zone, where carbon
assimilation by phytoplankton equals respiratory losses (instantaneously)
ii. Critical depth is where integrated daily photosynthetic carbon assimilation
equals integrated daily respiratory carbon losses. (This depth increases from
March to May in Box 2.5 as daylength increases C assimilation)
iii. If mixing depth > critical depth, phytoplankton blooms are unlikely
c. Whole-ecosystem variables:
i.
ii.
iii.
iv.
v.
Photosynthesis = P (gross production)
Algal respiration = Ra
Whole community respiration = Rc
Net photosynthesis = NPP = P-Ra
Net community production or Net ecosystem production = P-Rc (net
autotrophic if PS dominates, and net heterotrophic if respiration dominates)
What’s different about primary production in the ocean: diversity of organisms phylogenetically; light
variability that generates niches.
April 10, 2013 – energy flow and nutrient cycles
1. General principles:
a. Inefficient energy transfer across trophic levels –
i.
Growth yield (efficiency) – growth per food intake ranges 10-30%
ii.
Trophic yield (efficiency) – production at trophic level relative to next lower trophic level
ranges 5-20%
iii.
Inefficient energy transfer results in remineralized carbon and nutrients available to
primary producers
iv.
Inefficient energy transfer limits biomass of large-bodied organisms
b. Top-down control – biomass limited by consumption or disease (particularly viral mortality in
marine microorganisms?).
i.
Trophic cascades = special case of indirect effects; top-down control extends for at least
two sequential trophic interactions.
c. Bottom-up control –
i.
of abundance or biomass (Liebig’s law of the minimum);
ii.
of population growth or metabolic rate (Blackman limitation)
2. Marine-specific concepts:
a. Nitrogen cycling – f-ratio is the ratio of new to total (new and recycled) nitrogen taken up during
primary production.
i.
Recycled nitrogen = ammonium, nitrite, urea, amino acids
ii.
New nitrogen = nitrate; can derive from atmosphere (precipitation, dry deposition),
rivers (?), upwelling, or N-fixation.
iii.
F-ratio typically 0.3-0.5 but as low as 0.1 in deep or low-upwelling areas
iv.
Inverse of f-ratio tells how many times N moves through biotic compartment per year
b. Carbon – distribution of respiration and CO2 by depth
Epipelagic in light
Mesopelagic 150-1000m bulk of respiration
Bathypelagic 1000-4000m
c. Microbial loop – Fig. 3.12
G
PS
C
G
G
C
R
G
C
G
R
R
G
G
DOM
POM
Abyssopelagic 4000-6000m
Hadal 6000-10000m
C
C
R
R
R
All compartments have arrows recycling to DOM and POM
d. Distribution of metabolism by body size is dominated by smallest organisms in ocean: i)
combined biomass is highest in smallest-sized organisms; ii) specific metabolic activity – surface
to volume ratio is highest, which determines rates of processes; iii) yield<100%