Notes for Chapter 15:
Stability and Change in Marine Communities

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Case History: The Biotic Hole in the Sea

         Featured organisms:
           Chambered nautilus (Nautilus)
                 More Links: 1 - 2 - 3 - 4 - 5 - 6
             Extinct nautiloid relatives

Visit the source of this image
                 More Links: 1 - 2 - 3 - 4 - 5 - 6

             Extinct ammonites (somewhat more distant relatives)
                 More Links: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9

             Links to cephalopod extinction patterns:
                 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8

        After surviving a half a billion years, the few remaining
        species of Nautilus may be in peril. They are being
        commercially fished in some places with new technologies
        and by some reports in alarming numbers. Why?  For sale as
        pretty shells in department stores and shell shops. This fishing
        pressure could threaten the continued existence of a true
        living fossil, and only living shelled relative of octopuses,
        squids, and cuttlefishes. If you are interested in this topic,
        read this.

RQ 15.1: Earlier in the Earth's history, ammonites were a
        conspicuous and widespread group of predators, which
        went completely extinct over 65 Mya. While their
        chambered relative, Nautilus, persists today as a
        relatively rare group of less than 10 species, it did make
        it past the extinction event that doomed the ammonites.
        According to Dr. Peter Ward, how might the contrasting
        modes of reproduction in nautiloids and ammonites
        permitted the survival of nautiloids but not the ammonites?

I. The Dynamics of Communities

    a) Ecological Succession
        terms: succession, pioneer species, climax community,
            climax species

    b) Succession-like Processes in Marine Communities

RQ 15.2: In the boulder-strewn California intertidal site studied
        by Dr. Wayne Sousa (UCSB), different boulders could
        be dominated by any one of three different algal species.
        Describe the pattern of succession Sousa observed, and
        then explain what likely maintained the observed
        patchwork instead of dominance by a single species.

    c) The Species That Play a Part in Succession
        terms: r-selected species, K-selected species, logistic equation

RQ 15.3: Briefly describe the contrasting traits associated with
        either "r-selected" or "K-selected" species.

    d) Disturbance + Species Properties = Community Composition

RQ 15.4: Give an example of how the frequency of disturbance
        can influence community structure, and a separate example
        of how the properties of organisms can influence community

II. The Dynamics of Populations

    a) Interactions Among Organisms
        terms: predation, competition, cooperation, symbiosis
            (including commensalism, mutualism, parasitism),
            host and parasite or pathogen

RQ 15.5: Characterize three separate types of species interactions,
        and three types of symbiosis, using examples for each.

    b) How Interactions Among Organisms Change the Sizes of
        terms: endemic, territoriality (interference competition)

    c) Interactions Between Organisms and the Abiotic Environment

    d) The Balance Between Forces of Mortality and Natality
        terms: density-dependent vs. density-independent mortality

III. Case Histories

    a) The Crown-of-Thorns Sea Star

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         Featured organisms:
         Crown-of-thorns sea star (Acanthaster planci)
             More Links: 1 - 2 - 3 - 4 - 5 - 6

RQ 15.6: Contrast the following two hypotheses for explaining
        1960s outbreaks of numerous crown-of-thorns sea stars, which
        devastated large portions of the coral reefs they grazed on:
        1) Dr. Robert Endean's "snail predator" hypothesis; 2) Dr.
        Charles Birkelund's episodic larval recruitment hypothesis.
        Which hypothesis is best supported, and by what evidence?
        How have these results been extended to apply to what
        controls marine populations more generally?

    b) Marine Fishes
        terms (used in fisheries literature): population, stock,
            recruits, recruitment

RQ 15.7: Briefly describe the life history of herrings in the
        Gulf of Maine. What is the general consensus view
        for what might control the number of juvenile fish
        to recruit into the population stock? Why do haddock
        populations seem to have bad recruitment years when
        herring have good years, and vice versa?

    c) The Effects of El Niño
        terms: ENSO (= El Niño/Southern Oscillation), La Niña

        1) The trade winds weaken, the surface warms up, the
            animals starve.

        2) The giant El Niño of 1982-83 was the worst of our century
            [that is, until the even more severe one in 1997-98].

            More El Niño Links: 1 - 2 - 3 - 4 - 5 - 6

RQ 15.8: What causes El Niño and what are its consequences
        for the Pacific coast of North America?

        3) El Niño moves north - effects on the U.S. Pacific coast,

        4) ENSO episodes adjust population sizes - rarely for
            short-lived organisms, frequently for long-lived species.

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This page created 4/29/01 © D.J. Eernisse, Last Modified 5/24/01