| Dept of Biology, Lewis and Clark College | Dr Kenneth Clifton |
|
Biology
141 Lecture Outline |
Planet earth is dominated by water; it covers 71% of the earth's surface (roughly
61% of the northern hemisphere and 80% of the southern hemisphere)
Most of it is "salt water"
Organisms that live in water face a unique set of ecological challenges
Marine (salt water) and aquatic (generally, fresh water) ecosystems are linked... once again we see the importance of the hydrological cycle.
Today: talk about the oceans
The scale of oceanic systems is vast!!
The average depth is 4,000 m.
More than 84% is deeper than 2,000 m
The deepest part of the ocean (Marianas Trench) is nearly 11 km (6.8 miles!) below the surface.
At 36,000 feet, it would hold Mt. Everest (29,000 ft) with nearly two miles of water above!
Sunlight does not penetrate deeper than 1,000 m under the best of conditions
In general, the ocean is a deep, dark cold place (most temperatures < 4 °C).
Still, life abounds in the sea.... to understand marine diversity, you must understand the ocean
Physical characteristics of marine environments
Salinity (average of 35 ppt)... there is a latitudinal pattern based on evaporation and precipitation
Depth (0 to > 10000 m.... the Marianas Trench is 11,030 m deep.... almost 7 miles!)
What does this mean in terms of pressure?
Temperature - from below freezing (-1.9 °C) to >40 °C)
As in lakes and ponds in freshwater systems, the physics of thermoclines influences how water tends to stratify in oceans
Wave energy (how is is acquired... how is it released?)
Currents
Large scale (hemispheric gyres)
Small scale (upwelling)
Deep water, "thermohaline circulation" (oxygen, nutrient and "heat" transported across latitudes)
Light
The transparancy of water is an important physical feature
Different wavelengths absorbed at different depths (red lost most rapidly)
The photic zone.... why is it important?
Water as a heat sink (it takes lots of energy to heat up water, but water holds heat relatively well)... think about this with a warming planet.
Oxygen is less concentrated in water than in air and is not distributed evenly in the water column (oxygen minimum layer at intermediate depths)
Other nutrients
Phosphate and Nitrate (increase with depth to about 1 km, then remain constant)
Primary producers
Marine algae (protists): browns, greens, and reds
Phytoplankton (e.g., diatoms, dinoflagellates)
Emphemeral benthic algae (diatoms and other simple algae)
turf algae
macroalgae (seaweeds and kelps)
sea grasses (true flowering plants)
Marine animal life reflects the process of evolution
Invertebrates:
Protozoans (e.g., foraminifera, radiolarians.... are they really animals? Some are autotrophic.)
Sponges
Cniderians
Worms
Molluscs
Arthropods
Echinoderms
Vertebrates (much less common)
Fishes
Reptiles
Birds
Mammals
Trophic relationships and biomass...
Why understanding the difference between standing crop and renewal rate is important!
Inverted trophic biomass pyramids can emerge if renewal by producers and harvest by consumers is very high
Remember the efficiency of energy transfer and how it differs between ectotherms and endotherms
Recall some important marine ecosystems (for review, see section 2.4 in your text for treatment of both freshwater and marine biomes)
Coral reefs
other tropical ecosystems include seagrass beds and mangroves
Temperate reefs (often rocky substrate rather than coral)
Rocky intertidal (the influence of the tides)
Open ocean (vast and somewhat empty, with concentrations of life that vary in space an time)
The deep ocean (cold, dark, and little food... a very slow pace to life)
