Russell Lecture 1 - Oceanography 1 PDF

Oceanography 1 (Physical environment and productivity)  Lecture overview Temperature Properties of water, heat, zonation Chemical properties Salinity CO2, pH, ocean acidification Oxygen Productivity limiting factors OCEANOGRAPHY Study of physical properties...

Oceanography 1 (Physical environment and productivity)  Lecture overview Temperature Properties of water, heat, zonation Chemical properties Salinity CO2, pH, ocean acidification Oxygen Productivity limiting factors OCEANOGRAPHY Study of physical properties of the ocean physical environment, chemical environment, waves, tides, currents, etc. Strongly linked to biology & meteorology  Environment is a major driver of patterns (e.g. Polar bears can’t live in the desert) temperature predators chemistry Physical Biological competitors light intensity Environment BOTH Environment mutualisms nutrients disease currents etc. OCEANOGRAPHY Temperature Temperature and heat are not the same thing! Temperature is the response of a substance to the application of heat i.e., what you usually measure Water resists changing temperature when you apply heat – it is very stable Water has a high heat capacity (it takes a lot of heat to increase temperature) Thermal inertia Temperature stability Water has a high specific heat → buffers temperature fluctuations Daily: 31OC – 28OC (air) Stable environment for 62OC – 28OC (rock) chemical reactions Season: 36OC – -2OC (air) Daily: 26OC – 27OC Season: 30OC – 17OC Land Sea Temperature Chemical properties Water is a powerful solvent Known as the universal solvent Seawater contains many dissolved solids and gases. Total concentration of dissolved solids = salinity Typical salinity ~35 ppt (~3.5% dissolved substances) Warmer water can contain MORE dissolved solids = higher salinity Salinity  Water is strange – different heat-density relationship Ocean Estuaries Pure water  These properties cause stratification Surface zone (mixed layer) Warm, less dense Pycnocline (rapid temperature and density change) Deep zone Cold, dense http://marinebio.org/oceans/temperature/ Chemical properties Warmer water contains LESS dissolved gases Carbon Dioxide (CO2) pH, ocean acidification Source of carbon for autotrophs Oxygen (O2) Essential for life!  Oxygen & Carbon Dioxide Not at the equilibrium predicted by chemistry Why relatively high? Why so low? Why the sudden decrease? Why the increase?  Photosynthesis (productivity) O2 minimum zone typically 200 – 1000 m Respiration + less productivity Less respiration + colder Carbon Dioxide Oceans act as a carbon sink 60 x more CO2 in ocean than atmosphere More dissolves in colder water Not at maximum predicted by chemistry – used by photosynthetic organisms BUT, increasing with human activities CO2 moves quickly from atmosphere to ocean but slow ocean to atmosphere Thus, ocean absorbs CO2  Equilibrium Doney (2006) Sci. Amer.  pH range of seawater is ~7.5 – 8.5 But reducing with ocean acidification (means change) Oxygen Oxygen essential to nearly all life on earth Includes marine life! A gas – more dissolved in colder waters Oxygen can be a challenge for marine organisms O2 carrying capacity ~ 21% in air, < 1% in water Diffusion rate ~ 10,000 x greater in air CO2 O2 CO2 O2 O2 CO2 O2 CO2 Solutions Gas exchange structures pump water across respiratory surfaces live in high water velocity Primary productivity Oxygen produced in the ocean equivalent to terrestrial production BUT, 300 x less photosynthetic biomass in the ocean – how is this possible? Efficiency of the marine primary producers Mostly phytoplankton Autotrophs – capture light energy and convert it to organic matter  Primary productivity Major limiting factors: 1. Light 2. Nutrients http://www.smithsonianmag.com/science-nature/vanishing-marine-algae-can-be-monitored- from-a-boat-with-your-smartphone-2785190/?no-ist  1. Light extinction Much faster in water → restrict distribution of some taxa to ~ upper 50 m (corals, benthic algae) Red light absorbed quickest Garrison (2010) Oceanography: An invitation to marine science. 2. Nutrients Hard to measure nutrient concentrations in the ocean Any nutrients rapidly taken up by photosynthetic organisms! Use chlorophyll-a concentration as a proxy for nutrients 2. Nutrients http://www.nasa.gov/centers/goddard/news/topstory/chlorophyll_prt.htm 2. Nutrients Many of the most productive zones are in areas of upwelling Where nutrient rich water is upwelled from deep ocean to surface (next lecture)  Upwelling brings lots of nutrients → rapid phytoplankton blooms  Base of pelagic food chains Humans reliant on these food chains! (and therefore, the productivity of phytoplankton) Summary Physical and chemical properties drive the biology conditions vary by region, season, depth and, increasingly, human activities. Primary productivity in the ocean is essential to human existence