Download 1 Sounding the Deep - Department of Ecology and Evolution

1 Sounding the Deep
Notes for Marine Biology:
Function, Biodiversity, Ecology
By Jeffrey S. Levinton
©Jeffrey S. Levinton 2001
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
Marine Biology 2
• 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
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
Historical Background 2
• Linnaeus (1707-1778) who developed
means of naming species (e.g. Homo
sapiens), described many marine species
Historical Background 3
• Georges Cuvier (1769-1832) developed a largerscale 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.
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.)
Historical Background 5
• 19th Century - beginning of
modernization of scientific approach to
marine biology. Previously all work was
descriptive, now hypotheses emerged
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.
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
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.
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
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
The H. M. S. Challenger anchored at a remote equatorial Atlantic
island.
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.
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.
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.
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
Observations, Hypotheses, Experiments 2
• 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.
Observations, Hypotheses, Experiments 3
• 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
Observations, Hypotheses, Experiments 4
• 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.
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.
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)
HIGH
Uncaged
Fully caged
Top-only cage
Side-only cage
LOW Uncaged
Fully caged
Top-only cage
Side-only cage
Caging experiment, showing fully caged experimental condition
with three types of controls
Place on upper shore and lower shore
Habitats and Life Habits of
Marine Organisms
Life Habits
•
•
•
•
•
•
•
Plankton
Neuston, Pleuston
Nekton
Benthos
Infaunal versus epifaunal (epibenthic)
Semi-infaunal
Boring
Neuston
Boring
Nekton
Epifaunal
Plankton
Semi-infaunal
Infaunal
Benthos
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
High tide
Intertidal
Low tide
Neritic
Oceanic(pelagic)
150m
Mesopelagic
Benthic
Bathypelagic
2000m
4000m
Abysso
pelagic
Hadal
The End