Oceanography: Primary Production

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Primary production forms the base of marine food webs so understanding the variability of primary production in the ocean allows for a better understanding of the variability of all marine organisms. This allows us to study what?
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Ecosystem Function
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This is a major goal of biological oceanography is to understand how life in the ocean affects global elemental cycles. What is this called?
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Biogeochemistry
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Why is the global carbon cycle a topic?
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it is closely related to our global warming problem
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process that consumes carbon dioxide gas to form the particulate carbon of algae
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Photosynthesis
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This process produced Carbon Dioxide
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Respiration
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The difference between Photosynthesis and Respiration is what?
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what sinks to the ocean floor
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Small organisms that drift with the ocean currents
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Plankton
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Small cells (often single cells, but sometimes chains or colonies of many cells) that contain chlorophyll and drift with ocean currents
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Phytoplankton
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uses water and carbon dioxide (gas) and the energy of sun light to form glucose and oxygen.
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Photosynthesis
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the magnitude of primary production depends on these two things
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sunlight and essential plant nutrients
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the difference between the amount of CO2 consumed by photosynthesis and the amount of CO2 produced by respiration.
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Net Primary Production (NPP)
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the Net Gain or Net Loss of carbon within the cell
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Net Primary Production (NPP)
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Phytoplankton that require Silica
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Diatoms
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Phytoplankton that are motile so they are able to avoid sinking in calm waters
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Flagellates
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Phytoplankton that is able to grow at very low nutrient concentrations
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Photosythetic Bacteria
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At low light levels, phytoplankton are
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light limited
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At optimal light levels, phytoplankton are
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light saturated
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At very high light levels, phytoplankton are
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photoinhibted
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The depth at which the ambient light intensity is equal to the compensation light intensity is called the
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compensation depth
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What happens below the compensation light level?
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phytoplankton cells do not have sufficient light to photosynthesize fast enough to meet their basal metabolic needs and so cell respiration exceeds photosynthesis and this then leads to negative values of net primary production
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Primary Production makes…
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Oxygen
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Consumes Carbon Dioxide Gas and forms particulate organic carbon that can sink into the deep ocean
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Primary Production
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Why can smaller cells grow better at lower nutrient concentrations?
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Nutrient transportation is related to surface area and smaller cells have a larger surface area to volume ratio than larger cells
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The 4 Phytoplankton Nutrients of Interest to Oceanographers
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Nitrogen Phosphorous Silica (for diatoms) Iron
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The the main mechanism for getting deep nutrients into the surface (sunlit) layer of the ocean is
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mixing across the thermocline/pcynocline
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acts to hold phytoplankton near the sunlit surface ocean
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thermocline
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a significant barrier to upward mixing of nutrient rich deep water. The stronger the thermal stratification the strong the inhibition of nutrient mixing
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thermocline
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The Southern Ocean is important because
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It is the number one Iron Limited Region
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Three Spatial Patterns Due to Physical Biological Interactions
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Subtropical Gyre Regions Equatorial Pacific and Atlantic Regions Coastal Regions
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Subtropical Gyres exhibit….and…..
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Low Primary Production (on a per meter square basis) and Very Little Seasonal Variation
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brings nutrients to the surface year-round.
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Tidal mixings
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seasonally superimposes additional nutrients
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Coastal Upwelling
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The average light level that phytoplankton experience over the course of a day becomes dimmer as mixing depth increases because…
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cells spend an increasing proportion of the day below the compensation depth in the dark
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When cells mix below to the Critical Depth
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they have spent too much of the day below the compensation depth losing carbon
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Large Seasonal Increase in Primary Production Occurs in the North Atlantic Due To:
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1. Deep Winter Mixing. 2. Strong Springtime Stratification
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What percent of Ocean NPP is Global NPP
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46%
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How much Carbon does the ocean produce per year?
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50 Gt of Carbon per year
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The Open Ocean (Trade Winds, Westerly Wind and Polar regions) contributes how much of the total NPP of the ocean and why? why is this surprising?
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71% because of the vast area that these take up. This is surprising because they have relatively low intensities of Primary Production

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