Transcript Chapter 10
…in the Ocean… • Biological Productivity • We know what the ocean zones are and who lives there…but HOW do they live there together? • TROPHIC STRUCTURE: – Flow of energy or matter through an ecosystem, a “feeding” or trophic system – Primary, Secondary etc. PRODUCERS AND CONSUMERS – Food web/chain/pyramid Ecosystems • An ecosystem is the totality of the environment encompassing all parts: – – – – Chemical Physical Geological Biological • Ecosystems function by the exchange of matter and energy. • Plants use chlorophyll in photosynthesis: – to convert inorganic material into organic compounds – to store energy for growth and reproduction • Plants are autotrophs and the primary producers in most ecosystems. • All other organisms are heterotrophs, the consumers and decomposers in ecosystems. • Herbivores eat plants and carnivores eat animals; omnivores eat both. • Material is constantly recycled in the ecosystem. – Energy gradually dissipates as heat and is lost. Ecosystem Model 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. A food chain is the succession of organisms within an ecosystem based upon trophic dynamics. Who is eaten by whom. Fnft: Simple Food Chain A food web consists of interconnected and interdependent food chains Fnft: Food Web • An energy pyramid represents 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. Fnft: Energy Pyramid 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 the reproductive rate decreases The number of organisms decreases the total biomass decreases • The two major food chains in the ocean are: – the grazing food chain – the detritus food chain (non-living wastes form the base of the food chain) • Only about 10-20% of energy is transferred between trophic levels. • This produces a rapid decline in biomass at each successive trophic level. Energy Transfer Between Trophic Levels Fnft: Energy Transfer Between Tropic Levels • As the primary producers, plants require for photosynthesis : – – – – Sunlight Nutrients Water Carbon dioxide • The formula for photosynthesis is: 6CO2 + 6H2O + solar energy C6H12O6 (sugar) + 6 O2 Sun Producers Photosynthesizers: Green plants and algae, and specialized bacteria To space Consumers Respirers: Animals and decomposers and plants at night • Sunlight and nutrients are the limiting factors in marine ecosystems. • Phytoplankton blooms are the rapid expansion of a phytoplankton population because sunlight and nutrients are abundant. • Factors that limit plant growth and reduce primary production include: – Major Factors: • solar radiation • nutrients – Secondary Factors: • • • • Upwelling Turbulence grazing intensity turbidity • Only 0.1 to 0.2% of solar radiation is used for photosynthesis, and its energy stored in organic compounds. • Primary production is the total amount of carbon (C) converted into organic material per square meter of sea surface per year (gC/m2/yr) • 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. • This generates a strong thermocline that: – restricts upwelling of nutrients – results in lower productivity • High productivity locally occurs in: – areas of coastal upwelling – tropical waters between the gyres – coral reefs • In temperate regions productivity is distinctly seasonal. • Polar waters are nutrient-rich all year. • Productivity is only high in the summer when light is abundant. Variations in Primary Productivity North Atlantic Tropics Spring Diatom Bloom in the North Atlantic • Primary productivity varies from 25 to 1250 gC/m2/yr in the marine environment. • It is highest in estuaries and lowest in the open ocean. • In the open ocean primary productivity distribution resembles a “bull’s eye” pattern. – The lowest productivity is in the center – The highest is 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. – It is almost devoid of biological activity. • Continental shelves display moderate productivity between 50 and 200 gC/m2/yr. • This is because: – nutrients wash in from the land – 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. Global Variations in Primary and Secondary Production Fnft: Primary Productivity Upwelling in the South Pacific Figure 10-14 Upwelling Coastal Upwelling …so that’s only 1 side of the equation… What about the CONSUMERS? 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: C6H12O6 (sugar) + 6O2 6CO2 + 6H2O + Energy • The recovered energy is used for: – Movement – Reproduction – Growth • The food consumed by most organisms is proportional to their body size (exceptions occur). – Smaller animals eat smaller food – Larger animals eat larger food • The basic feeding strategies of animals are: – – – – – Grazing Predation Scavenging Filter feeding (suspension feeding) Deposit feeding/Detritovores • Population size is dependent upon food supply and grazing pressure. • Definitions: – Grazing – scrap algae/food off of coral/rocks/hard surface. Ex. parrotfish – Predation – one animal (typically larger/stronger) “preying” on another (typically weaker/smaller). Ex. Shark, barracuda – Scavenging – feeding on other dead animals and other food sources, not “picky.” Ex. Crab, lobster – Filter feeding (suspension feeding) – creating a feeding “current,” or to “filter” food particles out of the water column through various methods. Ex. Whale shark, barnacle, shrimp – Deposit feeding – eating organic matter from the bottom. These are commonly “tube builders” or “burrowers.” Many eat detritus (nonliving & organic waste, e.g. DOM, fecal pellets, dead animals/plants etc.) and are called Detritovores. Ex. Sea cucumber Predator Feeding Strategies Filter Feeder – Feather Duster Worm; Shrimp, (Ancient) Fish Barracuda Scavenger Crab Grazing Feeding Strategies Filter Feeder Parrotfish (on coral) Deposit Feeder Sea Cucumber Prey-Predator Relationships Fnft: Prey-Predator Relationships • And finally, the “other” consumer… • Bacteria are decomposers. • They break down organic material and release nutrients for recycling. Fnft: Nutrient Cycling Now let’s break it down… • …the “basics” • Food Webs and Trophic structures are different in different parts of the world (i.e. each HABITAT has its’ own unique balanced feeding structure) • Each section is a (larger) part of the whole Fnft: Simplified paths of the flow of oxygen and carbon in an idealized marine ecosystem Fnft: Biogeochemical cycle of nitrogen or phosphorus Fnft: Energy flow in a marine ecosystem Fnft: Major biotic components of a marine ecosystem Adapted from W. D. Russell-Hunter. Aquatic Productivity. Macmillan, 1970 Fnft: Food pyramid that leads to an adult herring Herring during different stages of development (growth) Figure 15.24 Figure 10.13 antarctic food chain antarctic food web Figure 10.14 Benthic food web Epipelagic Food web Figure 15.25 • Epipelagic food web Remember • EACH habitat will have its own food web/trophic structure based on: - location (and water chemistry) - organismal make-up - other abiotic “influences” (including proximity to land/pollution sources) WATCH FOR THESE AS WE STUDY EACH HABITAT IN THE COURSE!