Open Ocean Communities, Part 2

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Open Ocean Communities,Part 2

• Lecture 5
• Marine Biology

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Schedule for Today

• Non-binding Practice Quiz - next week
• Readings for next week - on the website
• (http//www.bchs.uh.edu/coralreef)
• The Great Climate Flip-flop
• Greening the Ocean
• Dis-crediting Ocean Fertilization
• Review and finish Open Ocean Communities

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Review of Last Lecture
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Food Chain
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Trophic Pyramids

• Highest levels of productivity are upwelling
  regions in the temperate zone at near-shore sites

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Biological aspects in the marine environments
that are in contrast to terrestrial systems

• External fertilization.
• Environment dominated by single-celled organisms
• Longevity patterns opposite
• - animals long-lived, plants shorter-lived.
• Longer food chains, more complicated, higher
  efficiency
• Neritic waters vs. Oceanic waters
• - neritic extends to continental shelf
• -influenced by coastal processes.

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Life in the Plankton

• Adaptation to planktonic life
• Transparency
• - high water content, no complex sensory organs
• - feeding, respiration and swimming all
  simultaneous
• 2. Life history adapted for high reproductive
  output in response
• to patchy and unpredictable food supply
• - high growth rates - 10 of body length per
  hour and
• exponential through life
• - short generation times
• 3. High fecundity sexual and asexual reproduction

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Life in the Plankton, cont.
4. Direct development (with exception of tadpole
stages in a few) 5. Viviparity and maternal
nutrition - live bearers 6. Large size - avoid
predation - colonial lifestyles 7. Generalist
feeding - takes advantage of all available
foods 8. High filtering efficiency - exploits
patchy planktonic lifestyle
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Copepod Development
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Plankton Size Classes
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Planktonic Biomassby Season and Location
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Larval Settlement

• Various factors of the environment to which
  larvae respond in selecting a suitable site for
  settling.

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Grazing on Phytoplankton
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Primary Productivity (PP)
  Definition the rate of formation of organic
compounds from inorganic materials   - It is
approximately equal to photosynthesis   Gross PP
total carbon fixed Net PP Production -
Respiration   - Currency gC/m2/yr, integrated
over all depths  
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Primary Productivity, cont.
Important terms compensation depth - point
where photosynthesis respiration compensation
intensity - light level at the compensation depth
D, usually approximately equal to 1 surface
irradiance
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Measurements of Productivity
How can productivity be measured? 1) Light-dark
bottle technique   light bottle photosynthesis
respiration dark bottle respiration
only   currency O2 level   difference between
the two equals photosynthesis, - this value
minus original level of O2 equals net
production or new production
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Measurements of Productivity, cont.
2) C14 labeling method H14C03 (labeled
bicarbonate)   Carbon uptake during
photosynthesis 14C particles on filter x the
available inorganic carbon x 1.05 (factor to
account for differential uptake of
12C   problem tends to underestimate
productivity
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Measurements of Productivity, cont.
3) direct measurement using satellite
imaging   measures intensity of reflected light
wavelengths emitted at 630 and 663 nm
(chlorophyll a and c)  
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Factors Affecting Primary Productivity
  1) Light - major factor 2) Nutrients and
trace elements - 2nd major factor 3)
Hydrography
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Nutrients and Productivity
-important for formation of proteins for
biochemical pathways to function   Nitrate
NO3- Nitrite NO2- Ammonium PO4 Phosphate
PO4--   Minerals Si to form SiO2 (test in
diatoms and silicaflagellates)
Fe and other trace minerals
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Light and Productivity

• Light for production is measured in PAR
  (photosynthetically active
• radiation) from 400-700nm wavelength
• Most important for photosynthesis 630 and
  663nm, corresponding
• to peaks in chla and chlc
• - Red end of spectrum differentially absorbed
• UV end is scattered
• Extent of absorption can be measured as
  downwelling
• (or extinction) coefficient

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Irradiance and Productivity, cont.
Defined as Iz Ioe -kz(exponent)  
kextinction coefficient, pure water k0.035
(PAR wavelengths averaged) the smaller number,
the clearer the water   z
depth , I intensity of light
(watts/m2) Io intensity of light
just below surface Iz intensity
of light at depth z
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Compensation Depth

• Compensation depth as a function of increasing
  number of phytoplankton
• ranging from no plants to large number of
  plants.

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Phytoplankton Irradiance Curves
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Phytoplankton Photodynamics

• - Algae are adapted to lower light levels
  relative to surface
•  
• reasons - mixing
• - avoidance of UV (migrate to depth less than
  surface)
• - photo-inhibition at highest light levels
• - Algal chlorophyll levels adapted to optimum
  light levels.
• - Highest production usually at 33 surface
  values
• As plankton multiply, light levels will decrease
• compensation depth will become shallower through
  time during the development of an
  algal bloom

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Mixing of Plankton
Turbulence - mixing driven by surface
winds   Critical depth (respirationphotosynthesis
) is deeper than compensation depth -
Circulation needed deliver nutrients, but also
moves passive algal cells into zones of low
light. Production can be shut down if there is
deep circulation.  
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Vertical Mixing of Plankton
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Vertical Movement of Plankton
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Production versus Depth and Irradiance
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Euphotic Zone Variation
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Global Net Primary Production
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Primary Production in the Biosphere
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Variations in Oceanic Primary Productivity
Geographic variation in productivity tropic lt
temperate ltpolar less seasonal to strongly
seasonal   Tropics less seasonal,
dependent on delivery of nutrients
more than light levels - thermal
stratification outside areas of upwelling
- very low production
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Photosynthesis and Chla biomass in different
oceans
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Seasonal Phytoplankton Succession
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Next Week
Ocean Nekton