Transcript Chapter 10 Biological Productivity in the Ocean
Chapter 10
Biological Productivity in the Ocean
©2003 Jones and Bartlett Publishers
10-1 Food Webs and Trophic Dynamics
An ecosystem is the totality of the environment encompassing all chemical, physical, geological and biological parts.
• Ecosystems function by the exchange of matter and
energy.
• Material is constantly recycled in the ecosystem, but
energy gradually dissipates as heat and is lost.
– Energy flows downhill, materials cycle! • All ecosystems are composed of: – Autotrophs (producers) – Heterotrophs (consumers)
10-1 Autotrophs
• Autotrophs use an abiotic source of energy to convert inorganic
material into organic compounds for growth and reproduction.
• Autotrophs produce food, and are known as “primary producers”. • Inorganic vs. organic material.
– Inorganic = CO products).
2 , NH 3 , NO 3 2 , PO 4 3 , etc – Organic = living, or derived from living tissue (proteins, lipids, carbohydrates, nucleic acids, or containing C-C bonds (petroleum • Plants are autotrophs and the primary producers in most ecosystems.
– Energy source is the Sun.
• Chemosynthetic bacteria are autotrophs and primary producers in deep vent communities – Energy source is inorganic sulfur molecules, NOT SUN!
Examples of Marine Autotrophs
phytoplankton Seaweeds Salt marsh Mangroves Eel grass Chemosynthetic bacteria
10-1 Food Webs and Trophic Dynamics
• All other organisms are heterotrophs, the
consumers and decomposers in ecosystems.
• Heterotrophs derive their energy from
organic matter (animals, plants, detritus, dissolved organic matter)
• Herbivores eat plants and carnivores eat
animals.
Examples of Marine Heterotrophs
fish krill crab whale Heterotrophic bacteria dinoflagellate copepod Tube worms
10-1 Food Webs and Trophic Dynamics
The word “trophic” refers to nutrition.
• Trophic dynamics is the study of the
nutritional interconnections among organisms within an ecosystem.
• Trophic level is the position of an organism
within the trophic structure of an ecosystem.
– Autotrophs form the first trophic level. – Herbivores are the second trophic level. – Carnivores occupy the third and higher trophic
levels.
– Decomposers form the terminal level.
10-1 Food Webs and Trophic Dynamics
• A food chain is the
succession of organisms within an ecosystem based upon trophic dynamics. (Who is eaten by whom.)
10-1 Food Webs and Trophic Dynamics
• A food web consists of interconnected
and interdependent food chains- more realistic.
Food Web
10-1 Food Webs and Trophic Dynamics
• An energy pyramid is the graphic representation of
a food chain in terms of the energy contained at each trophic level.
• The size of each level in an energy pyramid is controlled by the size of the level immediately below.
Energy Pyramid
Energy
Ecosystem Model: Definition
• A tentative, explanatory, generalization
about how ecosystem functions (i.e., a hypothesis).
• Structure of model arises from
observations.
• Tentativeness requires that models be
verified by experimentation or further observations.
Ecosystem Model: Generic
Ecosystem Model
• Ecosystem models show: – Trophic pathways (carbon flows) – Ecological efficiency – Resilience to species loss – Biological magnification – Biogeochemical pathways (flows of other
elements, Ca, Si, N, P, etc.).
Increased cell division causes bloom
10-1 Phytoplankton blooms and cell division
10-1 Food Webs and Trophic Dynamics
As the primary producers, plants require sunlight, nutrients, water and carbon dioxide for photosynthesis.
• Photosynthesis occurs within organelles called
chloroplasts, or within lamellae of prokaryotes.
• The formula for photosynthesis is:
Sunlight + 6 CO 2 + 6 H 2 O
C 6 H 12 O 6 (sugar) + 6 O 2 .
10-1 Food Webs and Trophic Dynamics
lamellae Diatom: Eukaryote Blue-green algae: Prokaryote
10-1 Photosynthesis
10-1 Respiration
Animals must consume pre-existing organic material to survive.
• Animals break down the organic
compounds into their inorganic components to obtain the stored energy.
• The chemical formula for respiration is:
C 6 H 12 O 6 (sugar) + 6 O 2
6 CO 2 + 6 H 2 O + Energy.
10-1 Food Webs and Trophic Dynamics
Photosynthesis
Sunlight + 6 CO 2 + 6 H 2 O
C 6 H 12 O 6 (sugar) + 6 O 2 .
Respiration
C 6 H 12 O 6 (sugar) + 6 O 2
6 CO 2 + 6 H 2 O + Energy.
* Respiration is similar to the combustion of gasoline in your automobile. It produces energy, carbon dioxide and water.
10-1 Food Webs and Trophic Dynamics
• The energy recovered during respiration is
used for movement, reproduction and growth.
– Respiration occurs in organelles called
mitochondria
– Animals and plants respire
10-1 Food Webs and Trophic Dynamics
• The food consumed by most organisms is
proportional to their body size.
• Smaller animals eat smaller food and larger animals eat larger food, although exceptions occur.
10-1 Food Webs and Trophic Dynamics
Heterotrophic dinoflagellates feeding on photosynthetic dinoflagellate
Blue whale (~30 m)
10-1 Food Webs and Trophic Dynamics
Krill (~0.01 m)
10-1 Food Webs and Trophic Dynamics
• The basic feeding styles of animals are: – Grazing
feed on plants
– Predation – Scavenging
actively pursue and capture food feed on dead stuff (detritus)
– filter feeding
filter plankton or detritus from water
– deposit feeding filter food from sediment
Cow grazing on grass
10-1 Food Webs and Trophic Dynamics
Dinoflagellate grazing on another dinoflagellate …or any zooplankton on phytoplankton, sea urchin on algae, snail on seaweed, etc.
10-1 Food Webs and Trophic Dynamics
Filter-feeder predator scavenger
10-1 Food Webs and Trophic Dynamics
Deposit feeder (polychaete worm)
10-1 Food Webs and Trophic Dynamics
•Population size is dependent upon food supply
and grazing pressure.
10-1 Food Webs and Trophic Dynamics
Bacteria are the decomposers; they break down organic material and release nutrients for recycling.
Nutrient Cycling
10-1 Food Webs and Trophic Dynamics
• Few bacteria are capable of completely
degrading organic material into its inorganic components. Most operate in succession with other bacteria to decompose material in a series of stages.
• Bacteria also serve as food for other
organisms either directly or indirectly.
10-1 Food Webs and Trophic Dynamics
• Bacteria can be divided into those that are
aerobic or anaerobic.
– Aerobic: (“with air”)- uses oxygen in air. – Anaerobic: (“without air”), in sediments. Use
oxygen contained within molecules, such as sulfate
SO 4 2 2O 2 + S 2 Hydrogen sulfide, H 2 S, then forms. “Rotten egg” smell
10-1 Food Webs and Trophic Dynamics
• Bacteria can also be divided into those that are
autotrophic or heterotrophic.
– Autotrophic: obtains food by photosynthesis • Blue-green algae (Prochlorococcus sp. – most abundant organism on Earth?).
– …or chemosynthesis - from inorganic compounds. • Volcanic vent bacteria – Heterotrophic: obtains food by eating other
organic matter.
• E. coli, etc.
Photosynthetic vs. Chemosynthetic Food Chain
Volcanic vent communities at Hydrothermal vent sites
Black smoker at hydrothermal vent
Volcanic vent communities at Hydrothermal vent sites
Volcanic vent communities at Hydrothermal vent sites
Chemosynthetic bacteria live inside worms and produce organic matter
Red Riftia tube worms thrive near a sea vent.
Are volcanic vent communities at Hydrothermal vents good analogs for life on other planets?
Below the icy surface of Galileo’s moon Europa, heat from tectonic forces may allow liquid water to exist. Do chemosynthetic bacteria exist here as well?
Food Chains and Energy Transfer
Food chains transfer energy from one trophic level to another.
• Biomass is the quantity of living matter per
unit area or per volume of water.
• With each higher trophic level, the size of
organisms generally increases, but their reproductive rate, number and the total biomass decrease.
Food Chains and Energy Transfer Large body size, low biomass, slow growth.
Small body size, high biomass, fast growth.
Food Chains and Energy Transfer
• The two major food chains in the ocean are
the grazing food chain and the Detritus food chain (non-living wastes form the base of the food chain).
Grazing Food Chain Phytoplankton Zooplankton Nekton Detritus Deposit Feeder Nekton Detrital Food Chain •Only about 10-20% of energy is transferred between
trophic levels and this produces a rapid decline in biomass at each successive trophic level.
Food Chains and Energy Transfer
•Only about 10-20% of
energy is transferred between trophic levels and this produces a rapid decline in biomass at each successive trophic level.
•Energy lost as kinetic
motion and maintenance respiration.
•Energy lost building non-
nutritional tissue (bones, chitin exoskeleton, diatom frustules, etc.)
0.1
1 10 100 Energy
Food Chains and Energy Transfer
Food Chains and Energy Transfer
0.1
0.1
10 8 g algae 10 7 g krill 10 6 g small fish 0.1
0.1
10 4 g small human 10 5 g large fish
Why not make trophic chain shorter?
10 4 g small human 0.1
10 5 g algae 0.1
0.1
10 5 g krill 10 5 g small fish
General Marine Productivity
Primary production is the total amount of carbon (C) in grams converted into organic material per square meter of sea surface per year (gm C/m
2
/yr).
• Factors that limit plant growth and reduce
primary production include solar radiation and nutrients as major factors and upwelling, turbulence, grazing intensity and turbidity as secondary factors.
• Only 0.1 to 0.2% of the solar radiation is
employed for photosynthesis and its energy stored in organic compounds.
10-2 General Marine Productivity
• Macronutrients and micronutrients are
chemicals needed for survival, growth and reproduction in large and small quantities, respectively.
• Upwelling and turbulence return nutrients
to the surface.
• Overgrazing of autotrophs depletes the
population and leads to a decline in productivity.
• Turbidity reduces the depth of light
penetration and restricts productivity even if nutrients are abundant.
Wave and Tide Turbulence
10-2 General Marine Productivity
Productivity varies greatly in different parts of the ocean in response to the availability of nutrients and sunlight.
• In the tropics and subtropics sunlight is
abundant, but it generates a strong thermocline that restricts upwelling of nutrients and results in lower productivity.
• High productivity locally occurs in areas of coastal upwelling, in the tropical waters between the gyres, and in coral reefs.
10-2 General Marine Productivity
• In temperate regions productivity is
distinctly seasonal.
• Polar waters are nutrient-rich all year but
productivity is only high in the summer when light is abundant.
Variations in Primary Productivity
10-3 Global Patterns of Productivity
Primary productivity varies from 25 to 1250 gm C/m
2
/yr in the marine environment and is highest in estuaries and lowest in the open ocean.
• In the open ocean primary productivity
distribution resembles a “bull’s eye“ pattern with lowest productivity in the center and highest at the edge of the basin.
• Water in the center of the ocean is a clear blue because it is an area of downwelling, above a strong thermocline and is almost devoid of biological activity.
10-3 Global Patterns of Productivity
• Continental shelves display moderate
productivity between 50 and 200 gm C/m 2 /yr because nutrients wash in from the land, and tide- and wave- generated turbulence recycle nutrients from the bottom water.
• Polar areas have high productivity because
there is no pycnocline to inhibit mixing.
• Equatorial waters have high productivity
because of upwelling.
• Centers of circulation gyres, which occupy
most of the open ocean, are biological deserts.
The Sargasso Sea and Vertical Profiles
10-3 Global Patterns of Productivity
It is possible to estimate plant and fish productivity in the ocean.
• The size of the plankton biomass is a good indicator
of the biomass of the remainder of the food web.
• Annual primary production (APP) is equal to
primary production rate (PPR) times the area for which the rate is applicable.
APP = PPR x Area (to which applicable )
• Transfer efficiency (TE) is a measure of the amount
of carbon that is passed between trophic levels and is used for growth.
• Transfer efficiency varies from 10 to 20% in most food chains.
10-3 Global Patterns of Productivity
• Potential production (PP) at any trophic
level is equal to the annual primary production (APP) times the transfer efficiency (TE) for each step in the food chain to the trophic level of the organism under consideration.
PP = APP x TE (for each step)
• Although rate of productivity is very low
for the open ocean compared to areas of upwelling, the open ocean has the greatest biomass productivity because of its enormous size.
10-3 Global Patterns of Productivity
• In the open ocean the food chains are
longer and energy transfer is low, so fish populations are small.
• Most fish production is equally divided between areas of upwelling and coastal waters.
• Calculations suggest that the annual fish
production is about 240 million tons/yr.
10-3 Global Patterns of Productivity
• Overfishing is removing fish from the ocean faster
than they are replaced by reproduction and this will eventually lead to the collapse of the fish population if not regulated.
Haddock Catch in North Sea
10-4 Biological Productivity of Upwelling Water
Upwelling of deep, nutrient-rich water supports large populations of phytoplankton and fish.
• The waters off the coast of Peru normally is an area
of upwelling, supporting one of the world’s largest fisheries.
• Every three to seven years warm surface waters in
the Pacific displace the cold, nutrient-rich water on Peru’s shelf in a phenomenon called El Nino.
• El Nino results in a major change in fauna on the
shelf and a great reduction in fishes.
• This can lead to mass starvation of organisms dependent upon the fish as their major food source.
The Ocean Sciences: Volcanic Vent Communities
• Volcanic vent communities have been
discovered along sea-floor spreading ridges.
• The base of the food webs in these vent
communities consists of chemosynthesizing bacteria, which obtain energy to manufacture food by oxidizing hydrogen sulfide gas.
• Seawater heated by magma leaches metal
from the basalts and these get precipitated as sulfide and sulfate minerals that form chimneys on the sea floor.
Plumbing in a Black Smoker
The Ocean Sciences: What Causes El Ni ño?
• When the trade winds are strong, cold,
nutrient-rich water upwells offshore Peru, supporting high primary productivity and large populations of anchovy.
• When air-pressure patterns change, the
trade winds weaken and even reverse direction, dragging warm, nutrient-poor water to Peru and initiating an El Niño event.
10-1 Photosynthesis
10-1 Photosynthesis
10-1 Photosynthesis