MARS2014 Lecture Notes - Lecture 6: Microbial Loop, Coccolithophore, Holdfast
Friday, 2 March 2018
MARS2014 Week 2 Lecture 3
Primary Productivity Pt.3
-Examples of marine primary producers: seaweeds, plankton
-Seaweeds/multicellular marine algae only live in shallow waters, need to
photosynthesise, no roots or vascular system, all done by vascular uptake, have to
grow quickly and have a high surface to volume ratio
-3 classifications of seaweeds; red, green, and brown algae
-Stipe and holdfast attaches them to the surface (aren’t plants so no roots)
-Plankton do not swim/swim very weakly so drift with the current
-Diatoms have 2 orders: Centrales (radial symmetry, dominant in marine), and
Pennales (bilateral symmetry, dominant in freshwater/benthic)
-Diatoms sink due to “glass” (silica) structures, they are rigid, abundant and diverse
>10000 living species, important in photosynthesis and the food web
-Dinoflagellates are protists with 2 flagella, can swim due to flagella (not against
currents), don’t sink in water column, many are poisonous, bioluminescence
-Coccolithophorids- inhabit cold sea waters, produce calcium carbonate (calcite)
coating, filter UV light, when they die they sink and transfer all the calcium carbonate
(important in the carbon cycle), responding well to CO2 increase
-Bacteria- most abundant organism on the Earth, the microbial loop, water surface,
unicellular that can produce long filaments, photosynthetic, e.g. cyanobacteria
(produce stromatolites), prochlorophytes (can be more photosynthetic in the
euphoric zone)
-The microbial loop- forms the bottom of the food web, contribute to carbon cycle, use
dissolved nutrients which other organisms cannot do (carbon and nitrogen), 2-5 million
in a teaspoon of water
-Microphytobentic communities- form on shallow marine sediments and rocks,
support grazing communities, 12-20% of primary productivity
-Episammic- marine organisms attached to a substrate
-Epipelic- free living marine organisms
-Epiphytic- marine organisms attached to seagrasses and algae
-Light intensity- depends on wavelength, angle of incidence, turbidity, depth
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