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1 Sounding the Deep

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  1. 1 Sounding the Deep Notes for Marine Biology: Function, Biodiversity, Ecology By Jeffrey S. Levinton ©Jeffrey S. Levinton 2001

  2. Marine Biology • Main elements are functional biology and ecology • Functional biology is the study of organismal function, such as reproduction, locomotion, feeding, and cellular and biochemical processes relating to digestion, respiration, and other aspects of metabolism

  3. Marine Biology2 • Ecology - the study of the interaction of organism with their physical and biological environments, and how these interactions determine the distribution and abundance of the organisms

  4. Historical Background • Early biologists were “natural philosophers” who made wide-ranging observations of the marine world as well as fishing folk who often ranged widely on the ocean • Aristotle (384-327 B.C.) and his contemporaries made many observations of behavior and form of shore organisms

  5. Historical Background2 • Linnaeus (1707-1778) who developed means of naming species (e.g. Homo sapiens), described many marine species

  6. Historical Background3 • Georges Cuvier (1769-1832) developed a larger-scale scheme to classify the animals into four major body plans: Articulata, Radiata, Vertebrata, and Mollusca. Others at this time in the late 18th century also developed beginning theories of evolution (Lamark) and major divisions to classify organisms.

  7. Historical Background 4 • Late 18th century - many trans-oceanic voyages resulted in important marine biological discoveries (e.g., British voyage of captain Cook across Pacific, voyage of French captain Nicolas Thomas Baudin, which brought back many specimens.)

  8. Historical Background 5 • 19th Century - beginning of modernization of scientific approach to marine biology. Previously all work was descriptive, now hypotheses emerged

  9. Historical Background 6 • Edward Forbes (1815-1854) - English biologist sampled Mediterranean and proposed the Azoic Hypothesis, that there was no marine life in depths deeper than 300 fathoms (1800 feet). First testable hypothesis • Azoic hypothesis falsified by work of Norwegian Michael Sars who described 19 species living deeper than 300 fathoms.

  10. Historical Background 7 • Charles Darwin (1809-1881), more famous for theory of evolution, also proposed other major marine hypothesis at this time - hypothesis of coral reef growth as a balance between upward coral reef growth and sinking of the sea floor

  11. Historical Background 8 • Darwin’s Coral Reef Hypothesis: • Test of hypothesis: you should be able to drill through coral down to a great depth before hitting the non-coral rock below. • Hypothesis tested in 1950s - hole drilled in Enewetak Atoll in Pacific and went through hundreds of meters of coral before encountering volcanic rock. Sinking not true on all reefs, however.

  12. Historical Background 9 • Late 19th century - beginnings of fisheries research in Europe • W. B. Carpenter and C. Wyville Thomson led the steam-powered Lightning that explored waters of northern British Isles

  13. Historical Background 10 • Thomson and J. Murray led the 5-year voyage of the Challenger, circumnavigated the globe, major contributions to oceanic exploration, collection of new species, most important voyage of 19th century for marine science

  14. The H. M. S. Challenger anchored at a remote equatorial Atlantic island.

  15. Historical Background 11 • Late 19th century - early 20th century: Founding of a number of important marine laboratories, including coastal labs and open-ocean labs, such as the Scripps Inst of Oceanography and Woods Hole Oceanographic Inst.

  16. Historical Background 12 • 20th century involved more sophisticated ship expeditions, use of new technology including submarines, SCUBA diving, satellite navigation systems, sophisticated ship-deployed samples, underwater video, etc.

  17. New technology from the 20th century. Left: The Alvin, a deep diving submersible, capable of exploring the deep sea bottom. Right:The Jason, a remote operating vehicle, which was used to find the Titanic in the open deep Atlantic.

  18. Observations, Hypotheses, Experiments • Marine biology, like all science depends upon a scheme of observation and inference of the natural world known as the scientific method • Induction - accumulation of a number of observations, leading to a general conclusion • Deduction - more powerful method of scientific inference, involving some premises, whose logical connection leads to a testable prediction, or hypothesis

  19. Observations, Hypotheses, Experiments2 • Hypothesis is testable - e.g., Increasing temperature increases the rate of oxygen consumption of crabs. • An untestable statement - Mermaids can never be observed, but they exist. • An inappropriate hypothesis, because the premise is wrong - Predators cannot eat prey, and they therefore have no effect on marine populations.

  20. Observations, Hypotheses, Experiments3 • Observations can be connected by means of correlation, the association of some phenomena with others - e.g., Larger body sized animals are found in colder water • Correlation is not causality. Body size might not be due to cold. Perhaps colder water is also deeper, and it is pressure that is the important factor

  21. Observations, Hypotheses, Experiments4 • Experimentation is more effective than establishment of correlations • Instead of looking for correlations, design an experiment that varies a hypothetically important factor; experiments can also be done in the field to manipulate factors such as predation.

  22. Hypotheses • Need to pose a null hypothesis, which can be tested • If null hypothesis is falsified, then you can proceed with further testing • Example: null hypothesis might be: Temperature has no effect on crab metabolic rate. Experiment could vary temperature, and result might be that metabolic rate increases with increasing temperature. Result: Null hypothesis is falsified.

  23. Null Hypothesis and Field Experiment • Null hypothesis: There is no effect on barnacle prey of placing a cage on the lower shore, which excludes predators This is an experiment aimed at understanding if predation is more intense on the lower shore, where we believe predators are more common (than on the upper shore)

  24. HIGH Uncaged Fully caged Top-only cage Side-only cage Uncaged Fully caged Top-only cage Side-only cage LOW Caging experiment, showing fully caged experimental condition with three types of controls Place on upper shore and lower shore

  25. Habitats and Life Habits of Marine Organisms

  26. Life Habits • Plankton • Neuston, Pleuston • Nekton • Benthos • Infaunal versus epifaunal (epibenthic) • Semi-infaunal • Boring

  27. Neuston Nekton Epifaunal Boring Benthos Plankton Semi-infaunal Infaunal

  28. Habitats • Intertidal • Subtidal • Continental shelf or Neritic - waters and bottoms on the continental shelf • Oceanic or Pelagic - waters and bottoms seaward of the shelf • Epipelagic zone - upper 150 m of water depth • Mesopelagic zone - 150 m - 2000 m depth • Bathypelagic zone - 2000 m - 4000 m depth • Abyssopelagic zone - 4000 m - 6000 m depth • Hadal - trench environments

  29. High tide Intertidal Low tide Neritic Oceanic(pelagic) 150m Mesopelagic Benthic 2000m Bathy- pelagic 4000m Abysso- pelagic Hadal

  30. The End