Idea Transcript
10/25/17
PLANKTON, PRIMARY PRODUCTIVITY, AND BIOGEOCHEMISTRY
EPSS 15 Fall 2017 LAB #7
• Pelagic zone = area of water that is not near the bottom, or shore, of a body of water
Green – 550 nm
Blue– 490 nm
Yellow – 590 nm
0
• The base of the food chain (phytoplankton) depends upon sunlight
Red – 720 nm
• Sunlight is critical to the distribution of oceanic life
Ultraviolet – 380 nm
SUNLIGHT & OCEAN ZONATION
Light Euphotic Zone
100
200 Twilight Dysphotic Zone
300
400
• Benthic zone = area associated directly with the seafloor Dark Aphotic Zone
500
600
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Photic Zone – depth is variable.
Green – 550 nm
Blue– 490 nm
Yellow – 590 nm
0
Red – 720 nm
• Sunlight is critical to the distribution of oceanic life
Ultraviolet – 380 nm
SUNLIGHT & OCEAN ZONATION
Light Euphotic Zone
100
Euphotic – region from surface to critical layer where photosynthesis dominates
200 Twilight Dysphotic Zone
300
Dysphotic – photosynthesis no longer dominant
400
Dark Aphotic Zone
500
600
THREE TROPHIC GROUPS ( trophic describes how an organism obtains energy) 1.
Producers – Autotrophs: make complex organic Diatoms - Producer compounds from simple inorganic molecules, commonly by photosynthesis (i.e. CO2, or sulfide, methane etc.) – Ex: phytoplankton, bacteria, tube worms 2. Consumers – Heterotrophs: feed on autotrophs or other heterotrophic organisms for energy and Copepod - Consumer carbon compounds – Ex: copepods, mammals, zooplankton 3. Decomposers – Saprotrophs: consume wastes or dead organisms, return nutrients to the ocean ecosystem – Ex: bacteria, worms, bacterioplankton Bacterioplankton- Decomposer
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PLANKTON • Plankton means drifter, these plants and animals are the base of the ocean food chain • These are organisms that cannot swim against currents. They depend on ocean circulation to move • Two types: phytoplankton and zooplankton • Smallest are cyanobacteria at less than 1µm, • Largest are macroplankton like jellies and snails.
PHYTOPLANKTON
Exercise 1
Tiny Plants – Coccoid cyanobacteria: 0.22µm, half of the photosynthetic biomass in the ocean – Diatoms: 20-200µm, SiO2, 45% of ocean s primary production, can be toxic to sea birds in high levels – Dinoflagellates: 0.1-2mm, protozoa, half phytoplankton, half zooplankton, 2 flagella for motion, red chlorophyll, red tide algal blooms – Coccolithophores: 2-20µm, covered in 30+ CaCO3 plates called coccoliths
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ZOOPLANKTON
Exercise 1
Tiny Animals – Copepods: 1-2mm, small crustaceans, transparent, often feed during the night – Krill: 1-15cm, shrimp-like crustaceans, move in swarms – Radiolarians: 0.1-0.2mm SiO2 amoeboid protozoans, spherical and conic skeletons and often spines – Foraminiferans: 0.1-1.5mm CaCO3 amoeboid protozoans with chambered shells
PRIMARY PRODUCTIVITY • Photosynthesis is the process by which organisms use chlorophyll to absorb energy from sunlight and convert CO2 and H2O into glucose. • Primary productivity = amount of photosynthetic production – Units of primary production: gcarbon/year
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PRIMARY PRODUCTIVITY • Photosynthesis is the process by which organisms use chlorophyll to absorb energy from sunlight and convert CO2 and H2O into glucose. • Primary productivity = amount of photosynthetic production – Units of primary production: gcarbon/year
Phytoplankton growth limited by availability of sunlight and nutrients Photosynthesis: 6 H2O + 6 CO2 + sunlight C6H12O6 + 6 O2 Nutrients are needed for the reaction to be processed
C6H12O6 + 6 O2
Respiration: 6 H2O + 6 CO2 + energy
Nutrients are needed for the reaction to be processed
PRIMARY PRODUCTIVITY • Photosynthesis is the process by which organisms use chlorophyll to absorb energy from sunlight and convert CO2 and H2O into glucose. • Primary productivity = amount of photosynthetic production – Units of primary production: gcarbon/year
Phytoplankton growth limited by availability of sunlight and nutrients Photosynthesis: 6 H2O + 6 CO2 + sunlight C6H12O6 + 6 O2 The total amount of photosynthetic production is the Gross Primary Product (GPP). From surface to depth where GPP=0 is the photic zone
C6H12O6 + 6 O2
Respiration (R): 6 H2O + 6 CO2 + energy
The net primary production (NPP) is the difference between the GPP and R. The region from the surface to the critical layer (NPP=0) is the euphotic zone.
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NUTRIENTS • Some nutrients required by marine organisms are limited in supply – Readily available: Na+, K+, Mg2+, Ca2+, H2O, CO2 – Limiting nutrients: • Nitrogen: nitrates --> NO3• Phosphorus: phosphate --> PO43• Silica: SiO32- or H4SiO4(aq)
• Redfield ratio: 106 C to 16 N to 1 P – Average molar ratio of three major elements taken up by marine plankton
• Micronutrients: only small amounts needed for life – iron (Fe2+), copper (Cu2+), selenium (Se2+)
BIOLOGICAL PUMP • The biological pump exports products from photosynthesis (organic carbon) to the deep ocean – Zooplankton feed on phytoplankton, nutrients transferred through fecal pellets in a process called egestion Some materials are oxidized or decomposed when they sink The process of respiration consumes oxygen to convert organic carbon to CO2
Respiration: C6H12O6 + 6 O2 6 H2O + 6 CO2 + energy Regulation of CO2 content of atmosphere and O2 + nutrient content of deep sea
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OCEAN CIRCULATION • Wind-driven and density-driven circulation transport nutrients
– O2 depleted with age of deep water, nutrients accumulate
• Upwelling currents replenish nutrients in surface waters – e.g. California current, Humboldt current
• Interiors of Subtropical Gyres are the least productive regions of the oceans because of thermohaline stratification
AGING DEEP WATER • How do we know deep water ages? – Radiocarbon measurements of Δ14C‰: younger waters have a higher fraction of radioactive carbon than older waters. As water ages, 14C decays, and CO2 accumulates – North Atlantic and Southern Ocean bottom waters are younger than Pacific bottom waters
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End
THIS IS EXACTLY WHAT IT LOOKS LIKE…
Susumu Honjo, Woods Hole Oceanographic Institution, 1997
Size of a comma (,)
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