Introduction to Marine Ecology – Basic Review

I. Ecological Principles
    A. Energy flows, nutrients cycle
    B. Ecosystem components
        1. trophic levels (food levels)
            a. first trophic level -- autotrophs -- primary producers  --

                1. photosynthetic autotrophs
                2. chemoautotrophs
            b. heterotrophs -- consumers
                (1) herbivores -- primary consumers

                (2) carnivores

                (3) omnivores -- consume more than one trophic level
                (4) decomposers

        2. food chain
 
        3. food web

        4. 80-95% lost at each transfer; on average only ~10% is passed to the next trophic level
        5. trophic pyramid
        6. standing crop – amount of living material (biomass) present at any given time
    C. Biotic structure of ecosystems
        1. niche -- role of an organism in a community
            a. fundamental niche -- potential distribution of a species in terms of all possible variables (food, space, breeding sites…)
            b. realized niche -- actual distribution of the species
        2. habitat
        3. species richness -- number of species
        4. species diversity -- both the richness (#) and the distribution of the total number of individuals among the species (evenness)
        5. community change over time -- ecological succession
            a. facilitation model -- each community modifies the environment, making it suitable for the next community until you get
                a 'climax' community (Clements 1936)
            b. inhibition model -- whichever species gets to a site first holds it against later settlers; succession not orderly and predictable (Egler 1954)
            c. tolerance model -- early colonizing species are not necessary and any species can start succession; community change occurs
                as more tolerant or competitively superior species prevail. (Connell and Slater 1977)

    D. Ecological control and regulation
        1. energy
        2. environment -- abiotic physiological restrictions; temperature, nutrients, salinity
           Leibig's law of the minimum -- the growth of organisms will be limited by a single factor that is present in the
                lowest concentration relative to (in proportion to) the requirement of the organism

        3. interactions among organisms
            a. competition -- organisms using a resource in short-supply
                (1) intraspecific
                (2) interspecific
                (3) competitive exclusion principle

            b. predation -- (grazer -- animal feeding on plants or sessile animals)
               keystone predators
            c. parasitism / disease

II. Division of the Marine Environment --
    Major subdivisions of the world ocean (vertical and horizontal)
        pelagic -- live in the open sea away from the bottom
            horizontal divisions
               neritic
               oceanic
            vertical divisions
               epipelagic / euphotic (photic)

               mesopelagic / disphotic -- pelagic with enough light form vision but not enough for photosynthesis (700-1000 m)
               aphotic -- dark
                   bathypelagic -- 10 degrees to 4 degrees C

                   abyssalpelagic -- directly over abyssal plain

                   hadalpelagic -- open water of the deep trenches

        benthic -- organisms and zones of the sea bottom
           intertidal / littoral
           sublittoral / shelf 
           bathyl
           abyssal
           hadal
    estuaries -- where rivers meet the ocean

III. Comparison of Terrestrial and Marine Ecosystems
    A. Physical and chemical differences
        1. Seawater is 830X denser than air
        2. Seawater is 60 X more viscous than air
          
        3. Gravity has much less influence on aquatic organisms
           
        4. Seawater absorbs light
      

        5. speed of sound is 4X faster in water than in air and wavelengths are longer

        6. Seawater is 1016 X less resistant to the transmission of electrical current than air – water is more conductive than air
       
        7. With greater depth, water pressure increases much more rapidly than in air (due to greater density)
        8. Water contains concentrations of dissolved organic materials (DOM) that are high enough to be a significant energy
            source for some organisms (e.g., corals)
        9. Air almost always has 21% oxygen; oxygen concentration is much less in water, and is highly variable
    B. Biodiversity differences
        1. More diversity at the phylum level for animals (34 known phyla); 14 endemic phyla in the ocean (only 1 on land)
        2. Less diversity at the species level
        3. Similar latitudinal gradients in biodiversity -- increase in species diversity as move from polar to the tropics
        4. Marine patterns:
            a. Indo-Pacific marine system has the highest diversity
 
            b. More diversity in benthos than in water column
        5. Less diversity of primary producers in the ocean at species level, more diversity of predators

    C. Life history differences
        1. Different dispersal of gametes --
            a. marine autotrophs and animals often shed both male and female gametes into the water and have external fertilization
            b. terrestrial plants often shed male gametes (pollen), but not female gametes
        2. No marine counterparts to terrestrial pollinators (animals that transfer male gametes)
    D. Structural and functional differences
        1. Main photosynthesizers:
            a. Terrestrial -- Large, long-lived flowering plants
            b. Marine -- Microscopic, short lived phytoplankton (photosynthesizers); exception of kelp
        2. Grazers
            a. Terrestrial –
                (1) often do not remove substantial amounts of the biomass
                (2) ability to digest plants is limited and requires bacterial gut flora
                (3) some very large herbivores (cow, deer, antelope)
            b. Marine grazers (copepods, clams, barnacles)
                (1) consume the entire plant;
                (2) often are small / microscopic;
                (3) often longer-lived than the autotrophs
        3. In terrestrial systems the plants are the most conspicuous, while in marine systems the animal component is often the most conspicuous.
        4. Body size patterns in food chains
            a. Body size is often positively correlated with trophic position in marine systems
            b. In terrestrial systems autotrophs are commonly larger than animals, and carnivores may be smaller than herbivores
        5. Longer food chains in ocean -- 5 links versus 3 on average
 

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