EVSC20004 Lecture Notes - Lecture 1: Beaufort Scale, Cambrian Explosion, Tidal Bore
18 May 2018
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LECTURE 1: INTRODUCTION
Overarching Themes
• Importance of Scale: the period of distance over which a variable is
relatively unchanged
o Ecological scales: spatial scale and temporal scale - animals
o Physical scales: spatial and temporal - deep circulation,
coastal fronts
o Biophysical scales: more complex - also spatial and
temporal, oceanic processes and organisms - strong coupling
o Physical environment driving biological processes
o Others: environmental gradients, species distributions,
adaptations, disturbance, competition
• Water on Earth: 97.5% saltwater, 2.5% freshwater
o 3/4 of earth covered in water
Evolution of Life
• 4,200mya - oceans formed
• 3,600mya - first known life - cyanobacteria in stromatolites
▪ Abundant in the Precambrian
• Living examples in Shark Bay, WA - high salinity, few grazers
• 2,500mya - oxygen levels start to rise in atmosphere
• 8000mya - water cycle reaches steady state
• 570mya - Cambrian explosion - life forms
• 430mya - first land plants
• 420mya - first land animals
Seawater: Physical properties & processes
• Heat capacity: ability of planet to regulate heat - ruled by the oceans (major role in temp
regulation for planet overall)
• Temperature: SST varies globally, and varies dramatically with depth, thermocline - layer in
which temperature changes rapidly
• Salinity: ions give water salinity - mainly sodium and chloride, also many others, 35 parts per
thousand of salt to water in ocean water - varies spatially and with depth - deeper waters
saltier
• Density: driven by temperature and salinity, denser seawater lower down
• Light: higher wavelengths unable to penetrate as far through the water column as lower
wavelengths - red can't travel very far, blue travels the furthest - differential penetration -
affects how organisms photosynthesise
• Physical drivers in combination: all interact with one another to create habitats and
ecosystems
o Vertical variation in light and nutrients affect phytoplankton distribution
o Upwelling - when there's a weak pycnocline, more nutrients available
• Flow: Beaufort scale - wind and tides
o Tidal bore: can generate waves
o Storm-generated waves: winds can generate waves
o Biological effects: wave exposure, distribution and swimming performance of fish
(research) - shallow water gets less wave action, waves affect species distribution
• Dissolved Oxygen: concentration influenced by physical properties and biological processes
• As temp rises, solubility of oxygen in water decreases, also dependent on depth
• Dependent on biological processes - animals photosynthesising
Themes
• Scale
• Physical Environment driving
Biological Processes
• Environmental Gradients
• Species Distributions
• Adaptations
• Disturbance
• Competition
