Section 3 Where does energy for life come from? Autotrophs- can fix inorganic molecules into organic substances. They can be: 1. Photosynthetic: use light energy to synthesize glucose from carbon dioxide and water Can only take place in photic zone so 90% of marine life is found here. 2. Chemosynthetic: synthesis of organic compounds by bacteria (or other living organisms) using energy derived from reactions with inorganic chemicals ex. Hydrogen Sulfide (H2S) Hydrothermal vents In 1977 Hydrothermal Vents were discovered. Prior to this, scientists thought that the only way energy could reach the bottom of the ocean would be when organisms died and sunk to bottom. Transfer of nrg Heterotrophs (consumers) obtain nrg by feeding off autotrophs or other consumers Primary Productivity- how much nrg is “fixed” into carbohydrates (organic matter) Remember from Bio: Carbohydrates are sugar molecules made of C,H,O in a ratio of 1:2:1 Most productive marine ecosystems are: 1. Estuaries 2. Swamps 3. Marshes Overall…. Oceans are the most productive ecosystems because it covers such a high proportion of Earths surface. Photosynthesis in the water Photosynthesis in marine ecosystems is carried out by: 1. Phytoplankton: microscopic photosynthetic organisms that live in the photic zone. -algae (single cell Kingdom: Protista) 2. Macroalgae ex. Seagrass and kelp
glucose Phyto and Zoo Plankton Greek Phyto = plant- autotrophs Algae Zoo = animal- heterotrophs Planktos = drifter; wanderer Cnidarians – jellyfish Crustaceans - krill Chlorophyll
Green pigment found in algae and plants that allows them to absorb energy from light Greek Chloros – green Phyllon – leaf http://earthobservatory.nasa.gov/GlobalMaps/view.ph p?d1=MY1DMM_CHLORA What affects the rate of photosynthesis?
1. Temperature: does not affect marine plants as much bc ocean temp is much more stable Remember: Water has a high heat capacity. 2. Carbon Dioxide: does not fluctuate much - always respirating organisms and CO2 getting dissolved in water through wave mixing. 3. Nutrients: plants need minerals and ions to grow. A lack of nutrients could affect their rate of growth. (more nutrient fun in ch.4) 4. Light: as light intensity decreases the rate of photo decreases. How light behaves in water Light: area of ocean that takes in sunlight is only 200m deep- (that’s really thin compared to the entire ocean depth.) Water can both scatter and absorb sunlight… waves= more reflected light bc waves act as a lens and focuses it. light travels more slowly in water this causes refraction (bending) particles (ex. Salt) can scatter light more too.
As absorption increase…temp increases As temp increases…kinetic energy of the particles in the water increase. This causes the warmer water to be more buoyant And LESS DENSE A WARM WATER LAYER WILL FLOAT ON TOP OF THE COLDER WATER!!! Thermoclines & Pycnoclines Thermocline= the transition between the warm and cold water temperatures in the ocean. Pycnocline= the transition between low and high density of the ocean water. There is very little mixing between the two because you would need a very strong energy source (like wind) to cause the warm water to mix with the cold water. But this is helpful because it allows phyto to stay on top of the water column!!!!
Why are there diff. thermoclines? Why do we need the thermocline? Without the density gradient there would be much more mixing and phytoplankton would sink. If they sink= not in photic zone=no photosynthesis=low/no productivity=no food BUT……. Generally the deeper waters have more nutrients The thermocline prevents nutrient rich waters from mixing with the surface layer= low productivity
Light Amount? Nutrient Amount?
Surface water High Low
Deep water Low/none High Deep Chlorophyll Maximum
• There is a point near the thermocline where productivity is highest. • There is enough light for photo. & enough nutrients for growth DEEP CHLOROPHYLL MAXIMUM this is where the concentration of chlorophyll is the highest. Self assessment questions? 1. State the two ways in which new biomass is produced in the ocean?
1. Explain why ocean productivity is limited to the first 200m in depth Chemosynthesis Captures the chemical energy of dissolved minerals to turn carbon dioxide into organic molecules. Several different bacterial species fix H2S into carbohydrates Beggiatoa- looooooong and thick bacteria that form orange “mats” (fix sulfur compounds.) Thiothrix- looooong bacteria that can fix sulfur compounds into carbs Some bacteria use other minerals to create different carbs. Hydrothermal Vents Riftia Symbiotic relationship with chemosynthetic bacteria Bacteria provide nutrients TO Riftia
The species that live here are extremophiles- organisms that are able to survive extreme temperatures, pressure, salinity and pH. Respiration and Photosynthesis Respiration is the process Producers need to use some of their in which ALL LIVING biomass created to do respiration for themselves- so 100% of the biomass THINGS release the synthesized CANNOT go to the chemical energy stored in consumer. organic molecules Gross Primary Production (GPP) (carbohydrates). This nrg Amount of light or chemical nrg can carry out all metabolic fixed by producers in a given time rxns for the organism. for a given area. (total biomass (Also produces heat which is lost created) to the environment) Net Primary Production (NPP) Amount of nrg left over for new biomass after Respiration (R) has 1. Where does this take place been taken into account. (This is within the cell? what consumers will get!) 2. What is the formula? NPP=GPP - R Comparison: Chemo vs Photo Chemo vs. Photo
• Use CO2 Chemo • Use H2O Photo • by products vary • Need nrg • produce glucose depending on source • green plants/algae • chemical being • Produce photic zone used (sulfur) • O2 is a by- sugars • done by product mutualistic • Sugars are bacteria used for • hydrothermal metabolism/ vents respiration Process Chemosynthesis Photosynthesis ------Feature
Energy Source
Products
Type of Organism
Main location in ocean