I. Ecological Principles
A. Energy flows, nutrients cycle
B. Ecosystem components
1. trophic levels
(food levels)
a. first trophic level -- autotrophs -- primary producers
--
1. photosynthetic autotrophs
2. chemoautotrophs
b. heterotrophs -- consumers
(1) herbivores -- primary consumers
(2) carnivores
(3) omnivores -- consume more than one trophic level
(4) decomposers
2. food chain
3. food web
4. 80-95% lost at each
transfer;
on average only ~10% is passed to the next trophic level
5. trophic pyramid
6. standing crop
– amount of living material (biomass) present at any given time
C. Biotic structure of ecosystems
1. niche -- role
of an organism in a community
a. fundamental niche -- potential distribution of a species in
terms
of all possible variables (food, space, breeding sites…)
b. realized niche -- actual distribution of the species
2. habitat
3. species richness
-- number of species
4. species diversity
-- both the richness (#) and the distribution of the total number of
individuals
among the species (evenness)
5. community change over
time -- ecological succession
a. facilitation model -- each community modifies the
environment,
making it suitable for the next community until you get
a 'climax' community (Clements 1936)
b. inhibition model -- whichever species gets to a site first
holds
it against later settlers; succession not orderly and predictable
(Egler
1954)
c. tolerance model -- early colonizing species are not
necessary
and any species can start succession; community change occurs
as more tolerant or competitively superior species prevail. (Connell
and
Slater 1977)
D. Ecological control and regulation
1. energy
2. environment -- abiotic
physiological restrictions; temperature, nutrients, salinity
Leibig's
law of the minimum -- the growth of organisms will be limited by a
single factor that is present in the
lowest concentration relative to (in proportion to) the
requirement
of the organism
3. interactions among
organisms
a. competition -- organisms using a resource in short-supply
(1) intraspecific
(2) interspecific
(3) competitive exclusion principle
b.
predation -- (grazer -- animal feeding on plants or
sessile
animals)
keystone predators
c. parasitism / disease
II. Division of the Marine Environment --
Major subdivisions of the world ocean (vertical
and horizontal)
pelagic -- live in
the open sea away from the bottom
horizontal divisions
neritic
oceanic
vertical divisions
epipelagic / euphotic (photic)
mesopelagic / disphotic -- pelagic with enough light form vision
but not enough for photosynthesis (700-1000 m)
aphotic -- dark
bathypelagic -- 10 degrees to 4 degrees C
abyssalpelagic -- directly over abyssal plain
hadalpelagic -- open water of the deep trenches
benthic --
organisms
and zones of the sea bottom
intertidal
/ littoral
sublittoral
/ shelf
bathyl
abyssal
hadal
estuaries -- where rivers meet the ocean
III. Comparison of Terrestrial and Marine Ecosystems
A. Physical and chemical differences
1. Seawater is 830X denser
than air
2. Seawater is 60 X more
viscous than air
3. Gravity has much less
influence on aquatic organisms
4. Seawater absorbs light
5. speed of sound is 4X
faster
in water than in air and wavelengths are longer
6. Seawater is 1016
X less resistant to the transmission of electrical current than air –
water
is more conductive than air
7. With greater depth, water
pressure increases much more rapidly than in air (due to greater
density)
8. Water contains
concentrations
of dissolved organic materials (DOM) that are high enough to be a
significant
energy
source for some organisms (e.g., corals)
9. Air almost always has
21% oxygen; oxygen concentration is much less in water, and is highly
variable
B. Biodiversity differences
1. More diversity at the
phylum level for animals (34 known phyla); 14 endemic phyla in the
ocean
(only 1 on land)
2. Less diversity at the
species level
3. Similar latitudinal
gradients
in biodiversity -- increase in species diversity as move from polar to
the tropics
4. Marine patterns:
a. Indo-Pacific marine system has the highest diversity
b. More diversity in benthos than in water column
5. Less diversity of primary
producers in the ocean at species level, more diversity of predators
C. Life history differences
1. Different dispersal of
gametes --
a. marine autotrophs and animals often shed both male and female
gametes
into the water and have external fertilization
b. terrestrial plants often shed male gametes (pollen), but not
female gametes
2. No marine counterparts
to terrestrial pollinators (animals that transfer male gametes)
D. Structural and functional differences
1. Main photosynthesizers:
a. Terrestrial -- Large, long-lived flowering plants
b. Marine -- Microscopic, short lived phytoplankton
(photosynthesizers);
exception of kelp
2. Grazers
a. Terrestrial –
(1) often do not remove substantial amounts of the biomass
(2) ability to digest plants is limited and requires bacterial gut
flora
(3) some very large herbivores (cow, deer, antelope)
b. Marine grazers (copepods, clams, barnacles)
(1) consume the entire plant;
(2) often are small / microscopic;
(3) often longer-lived than the autotrophs
3. In terrestrial systems
the plants are the most conspicuous, while in marine systems the animal
component is often the most conspicuous.
4. Body size patterns in
food chains
a. Body size is often positively correlated with trophic position in
marine
systems
b. In terrestrial systems autotrophs are commonly larger than animals,
and carnivores may be smaller than herbivores
5. Longer food chains in
ocean -- 5 links versus 3 on average