Download physical features of the marine environment

Marine Biology, April 2 & 4, 2007
Introduction; Abiotic factors
I.
II.
Course overview
Physical features of marine ecosystems
A.
The water itself is an essential ingredient
1.
Origin of water on earth

Hypothesis: Water originated from collision with icy meteorites during
the formation and early history of the earth

Our search for life on other planets concomitant with our search
for water...
2.
Polarity of water
3.
Hydrogen bonds due to polarity [Fig. 3.1] cause water to have the following
properties:

cohesion/surface tension

high heat capacity [Fig. 3.3] What does this mean?

Liquid at a wide range of temperatures

High latent heat of melting

High latent heat of evaporation:
4.
Water density and its importance [Fig. 3.3]

Maximum density of fresh water is 4°C

Ice floats!

What if ice didn’t float?
5.
Universal solvent [Fig. 3.5]
6.
The presence/absence of water can be critical for intertidal organisms.
B.
Specific properties and contents of water matter, and can vary among marine
habitats.
1.
Salinity: total concentration of dissolved ions (ppt or psu)

What is the source of dissolved ions [Fig. 3.6]

What is the salinity range of ocean water?

List of solutes contributing to salinity [Table 3.1]

Many of these ions have major physiological roles. (Examples…)

Estuaries have a wide range of salinities

How does this impact organisms?
2.
Temperature

Range of 28-212°F (-2-100°C)

Location of highest ocean temperatures? Lowest ocean
temperatures?

Intertidal organisms subject to a wider swing.

Why are coral reefs only in tropical regions?

Global surface temperature distribution [Fig. 3.10]
3.
“Typical” vertical profile of salinity, temperature, and density [Fig. 3.22]

Salinity varies with depth

NOTE: Usually salinity is lower at the surface than at depth.
Why?

Colder water is more dense and sinks below warmer water

Region of rapid temperature change is the thermocline

Region of rapid density change (based on both temperature and salinity)
is the pycnocline
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4.
5.
6.
7.
8.
9.
Nutrients (esp. nitrogenous, phosphorous, silicaceous and iron cpds)

Key roles in growth of marine producers

Distribution of marine primary production mirrors nutrient
distribution [Fig. 15.26]

Kelp forests possible only where there are ample nutrients

Brought up by a process called upwelling…
Dissolved gases

What are the major gases?

What factors determine the concentrations of oxygen and carbon
dioxide?

Example: Vertical profile of oxygen with depth [Fig. 16.18]

Be able to explain this vertical profile!

Some marine organisms tolerant of low oxygen levels

The ocean stores more than 50X the carbon dioxide found in the
atmosphere.
pH

Directly, a function of [H+]

Indirectly, a function of dissolved elements/molecules (seawater has pH
of 7.6-8.6, while freshwater has a lower pH and is thus more acidic)

Addition of acidic compounds lowers pH

Addition of carbon dioxide can lower pH

Respiration: lowers pH

Photosynthesis: raises pH

Generally stable in ocean waters. Why?

Can be a problem in closed aquaria. Why?
Light [Fig. 3.11]

primary energy source (although some marine organisms in
hydrothermal vents can obtain energy chemically)

Greatly affects primary producer’s growth, diversity, distribution

Rapid loss of light with depth

Different wavelengths of light are absorbed differently
(a)
red is reflected/refracted near the surface
(b)
violet, orange and yellow make it a bit deeper (to ~20
meters)
(c)
blue (and to some extent, green) penetrate the deepest,
given the ocean its color when you look down
Pressure [Fig. 3.14]

air spaces can be squeezed

enzymes operate differently

hard structures can be crushed
Ocean currents

Wind driven; influenced by Coriolis effect caused by Earth’s rotation

Successive layers affected differently by wind vs. Coriolis effect
(read about if not familiar!)

Ekman layer deflected 90º clockwise in N hemisphere, 90º
counterclockwise in S hemisphere [Fig. 3.19]

Major ocean surface currents, or gyres [Fig. 3.20]

Impact of major currents on ocean temperature [Fig. 3.21]
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10.
11.
12.
13.
III.
IV.
Upwelling [Figure from Nybakken text, see also Fig. 15.30]

Brings cold, nutrient rich water to the surface

Occurs where surface currents are parallel to shore (in the correct
direction), and also in equatorial region

Surface water is “replaced” by cold, nutrient rich water from
depth; ideal for primary producers!

Key is a steady strong wind and a deep reservoir of cold,
nutrient rich water.

Global upwelling regions [Fig. 15.31]
Great ocean conveyer

Time scale: 4000 year turnover

Key: salty, cold water sinks near Greenland & Antarctica; brings oxygen
to depths

Why is the water in the regions of high salinity as well as cold?
Waves

Caused by wind; become higher and shorter close to shore

Shallow organisms most affected

How do particles move within waves?
Substrate

Mud, rock, sand, etc…

Different survival strategies in different substrates

Example: shape of mole crabs vs. shore crabs.
Tides
A.
What causes tides? Why are there usually two low two high tides each day?
1.
Role of moon vs. sun’s gravitational force.

Which has the greatest effect on tides and why?
2.
Role of centrifugal force (caused by the rotation of the earth and moon
around a mutual center of gravity)

Location of the mutual center of gravity

Resultant centrifugal force

Where is it greatest and why?
3.
Role of the earth’s rotation.

As your position on earth relative to the moon changes, so does the
tide.
B.
Why are there some times in the month when the tides are really high and
really low, and other times when they are moderate?
1.
This is based on the relative positions of the sun and moon (see Fig. 3.33)

Spring tides: Moon and sun aligned (new or full moon)

Neap tides: Moon and sun at right angles (half moon)
C.
Why are the two low tides and two high tides not of equal height?
1.
Earth is tilted, so that "the bulge" is not experienced equally
Tidal zones
A.
Upper intertidal (splash zone): Organisms splashed with water a maximum of
once per day. Rarely submerged.
1.
Examples: littorine snails (periwinkles), some barnacles and limpets, Ligia
B.
Middle intertidal (higher part): Organisms usually wet once each day,
occasionally twice each day. (Some schemes will call this the high intertidal)
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1.
V.
VI.
Common organisms are desiccation-resistant algae. Many barnacles,
limpets and the predatory snails, Nucella spp. (feed on barnacles)
C.
Middle intertidal (lower part): Organisms almost always wet 2x/day, exposed
2x/day. So, wet at high tides, dry at low tides.
1.
Mussels often dominant; many other common intertidal species.
D.
Lower intertidal: Organisms exposed only during the low, low water (1x/day or
less)
1.
The sea grass, Phyllospadix.
2.
Nudibranchs, Pycnopodia helianthoides, many worms, sponges.
Physical factors influencing the distribution of organisms
A.
Extent of tidal exposure (i.e. the zones previously described)
B.
Amount of wave action:
1.
Example: Yaquina Head

Areas with less wave action more algae-covered. Why?
C.
Exposure to direct sunlight
1.
Determines how much drying out (desiccation) will occur
2.
Crevices and overhangs vs. direct sun: how is “zonation” affected?
D.
Temperature
1.
Geographic differences (California vs. Oregon)
2.
Cracks, crevices and overhangs are cooler
E.
Specific characteristics of the substrate:
1.
Rough vs. smooth surfaces (which is usually “preferred”?)
F.
Other characteristics of water which we discussed last time also play a role.
1.
Example 1: Nutrients
2.
Example 2: High-salinity pools in splash zone (due to evaporation)
Adaptations for surviving the changing tides: Why can some organisms survive the
harsh environment of the intertidal? Primarily, they have evolved mechanisms for
conserving water, or keeping tissues from drying out.
*Only those best adapted can live in the highest zones.
A.
Trapping water within
1.
Why important?
2.
Mechanisms

Mucopolysaccharides: mucousy substance which keeps cells
from drying out. Often present in marine algae.

Physical barriers (may also offer protection from predation)

Trap doors that keep animal completely enclosed
(a)
Operculum of snails
(b)
Tergal and scutal plates of barnacles

Closing up (anemones, mussels).

Clamping down: limpets, chitons and others
(a)
Some are “homing” species that fit a specific
crevice
B.
Microhabitat refuges
1.
Isolated pools persisting in high intertidal.
2.
Northern exposures more shaded.
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C.
3.
crevices
4.
under rocks
5.
Beneath algae. Cooler and wetter than on bare and exposed rocks.
6.
Some species move up and down with the tides
Physiological adaptations
1.
Reduction of metabolic rate: less gas exchange means less water loss
2.
Changes in photosynthetic ability. One high intertidal species of algae,
Fucus (common...) photosynthesizes at its highest rates when it is 20%
desiccated.

May involve a switch in ability to use carbon dioxide from
atmosphere vs. water.
3.
Contrast, low intertidal algal species photosynthesized best when fully
submerged.

May involve a switch in ability to use carbon dioxide from atmosphere
vs. water
Study questions
(Disclaimer: You are responsible for all material presented in lecture. Note that lecture
information goes beyond what is written in the PowerPoints. Your own notes as well as the
text will be useful in helping you answer these questions.) Also, be able to answer questions
imbedded in the outline!
1. What is the best accepted theory about how water originated on earth?
2. Sketch the structure of a water molecule. Then, show the polarity of the water molecule as well as
hydrogen bonding between several water molecules.
3. Which important physical attributes of water are related to its polarity and ability to form hydrogen
bonds? Discuss these physical attributes as they relate to water’s ability to support the existence of
life on earth.
4. Discuss the role of hydrogen bonds as they relate to the temperature of water. Be sure you
understand the consequences of high heat capacity.
5. How does the relationship of temperature and density of water differ from most other substances?
Think especially about solid vs. liquid water. Explain why is this relationship is important to aquatic
life in some places.
6. Other than the water itself, what physical aspects of water matter to marine organisms? Be specific
and provide examples of the role(s) of each particular factor to marine organisms. Note that we will
delve into this question in various ways throughout the course, but you should be able to give some
basic examples.
7. Where are the sources of dissolved ions in seawater? Which are the major ions found in seawater
(top two?) Also, name several ions found in seawater and provide examples of their physiological
roles.
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8. What is pH? How does photosynthesis affect pH? How does respiration affect pH? Why are pH
changes often a problem in closed systems (such as marine aquaria) but not in the open ocean.
9. What are some of the key inorganic nutrients found in the ocean?
10. How does the range of temperatures in the ocean compare to that on land? Where are the highest
ocean temperatures found? Where are the highest/lowest sea surface temperatures, and how do
ocean currents affect the distribution of temperature?
11. Describe how temperature and salinity affect the density and vertical profile of water.
12. Provide two major roles of light in marine ecosystems.
13. What is meant by “attenuation” of light? Which wavelengths of light pass through water best?
Least?
14. How does pressure change with depth? What effects might pressure have on organisms?
15. What is substrate? Provide examples of different substrates in the marine environment.
16. Is oxygen concentration similar in all ocean habitats? What key factors affect the concentration of
oxygen in different ecosystems?
17. Sketch/describe the basic vertical profile of oxygen in the ocean, and explain why you see the
particular distribution that you do. Be as specific as possible (i.e. why are surface waters relatively
high in oxygen, what causes the oxygen minimum zone, etc…?)
18. How does the concentration of carbon dioxide in the ocean compare to that in the atmosphere?
19. What, basically, causes ocean currents?
20. Why does the surface water move in a different direction than the wind? Why do different layers of
the Ekman spiral move in different directions? What is the net direction of movement of the entire
Ekman layer compared to wind direction in the Northern hemisphere? In the Southern hemisphere?
21. In which direction do the major ocean gyres circulate in the Northern hemisphere? In the Southern
hemisphere? Be sure you know where the warm currents vs. the cold currents are based on the
circulation patterns. (Learn the pattern rather than simply memorizing individual currents!)
22. What is the “Great Ocean Conveyer” and how long does water take to cycle through it? In which
two locations does dense, cold, and oxygen-rich surface water sink to form the “bottom water”, and
how does the surface water become so salty, cold and oxygen-rich in these locations?
23. Describe the process of upwelling with words and diagrams, being sure to include all causal factors.
What changes in the water does upwelling cause? What impact does this have on the marine
community and why? Be sure you understand which direction the wind needs to move in each
hemisphere in order to get an offshore movement of the Ekman layer!
24. What causes waves? Which organisms (i.e. location) are most affected by waves? How do particles
move within waves?
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25. What causes tides? Use diagrams and words in your explanation.
26. Sketch a mixed, semi-diurnal tidal cycle. Why are there two low tides and two high tides each day in
most coastal regions? Why are the two lows and two highs not of equal height? Use diagrams and
words in your explanation.
27. Explain why there are spring tides and neap tides; in other words, why do the high-highs and lowlows (and high-lows and low-highs) differ in height at different times of the month? Use diagrams
and words in your explanation.
28. Why does the time of the high tides and low tides shift from day to day? What is the approximate
amount of time of this shift, and in which direction (earlier or later)?
29. On your sketch of the mixed, semi-diurnal tidal cycle, show the different tidal zones, and understand
the level of exposure each receives. Also, be able to name representative organisms in these zones.
(NOTE: Your knowledge of what is found where will increase throughout the quarter.)
30. List several physical factors which influence zonation of intertidal organisms, and briefly explain
why each is important. Illustrate your answer with a specific example.
31. List some general ways that intertidal organisms are adapted to deal with desiccation, and then give
specific examples. NOTE: As we study specific intertidal organisms during lecture, you will learn
how each one deals with desiccation.
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