Ch. 13 - Communities and Ecology of the Offshore Oceans
How is the North Atlantic Ocean portrayed as the "standard" cold-temperate ocean?
Contrast the compensation depth with the critical depth.
Describe seasonal patterns for a typical phytoplankter in the North Atlantic Ocean.
Light Comp. Depth Stirring Depth
Winter
Spring
Summer
Fall
What role does the thermocline have? What is it? When does it form?
Contrast the Sargasso Sea to the North Atlantic Ocean.
Contrast the North Polar Sea to the North Atlantic Ocean.
Contrast the North Polar Sea to the South Polar Ocean.
Where and why does upwelling occur?
How is net primary productivity (NPP) defined?
Contrast eutrophic and oligotrophic ocean communities. Where are they? Contrast them with the "apple index."
Where is the mesopelagic community? What are its typical organisms? How do they get their food?
Suggest alternative (not necessarily mutually exclusive) hypotheses that might account for vertical migration of mesopelagic animals.
What affect does vertical migration have on overall oceanic productivity?
Where is the bathypelagic community?What are its typical organisms? How do they get their food?
Describe some feeding and reproductive adaptations to life in this environment.
What is typical ocean bottom? What organisms are there? About how dense are they?
Where do hydrothermal vent communities occur? How do they contrast with typical ocean bottom communities?
Describe the energy flow of a hydrothermal vent community.What are some feeding adaptations of hydrothermal vent communities?
Chapter 14 – Ecology of Shallow Marine Environments
Review Questions
Compare the following habitats with respect to 1) physical characteristics; 2) typical communities; 3) amount of productivity; 4) source of productivity; 5) relative degree of disturbance; 6) long-term fluctuations
Rocky intertidal
Kelp Forests
Cobble beaches
Sandy beaches
Muddy beaches
Salt marshes
Mangrove forests
Sea grass communities
Estuaries
Coral reefs
Review Questions for Chapter 14
Give two reasons why shallow water depths are more likely to be productive than deeper water depths (see Fig. 14.1).
Why doesn’t wind tend to directly cause upwelling of nutrients?
Why does disturbance increase species diversity? What is the stability-time hypothesis?
How did Connell distinguish between predation and competition alternative explanations for why some barnacles were most common in sub-optimal habitats?
Give an example of a community characterized by alternative stable states.
Contrast northern and southern hemisphere rocky subtidal kelp forests.
Why are sea otters considered keystone species?
Contrast sediment habitats: cobbles, sand, and mud.
What are some typical characteristics of interstitial fauna?
Why does the interstitial fauna produce more biomass each year than the macrofauna, even though the macrofauna typically outweighs the interstitial fauna?
Biol. 317 - Lecture notes –
Chapter 16 (Long-term change) and 17 (Oil pollution)
Long-term change
New
species take up residence
OR Resident
species disappear completely
Mechanisms:
1. Dispersal (drift, migrate, or be carried across
oceanic barriers)
2. Evolutionary
change (new species arise by splitting of old species)
3. Long-term
shift in environmental conditions (e.g., ice ages, cooling/warming)
Dispersal
Pre-human:
Rare events
unusally
broad larval dispersal (e.g., El
Niño changed normal current patterns)
rafting
(as “benthic” juveniles or adults)
climatic
changes
continental
drift (opening of formerly isolated ocean basins)
Human-aided
Ship
transport (often in ballast, e.g., zebra mussel)
Incidental
to transport of commercial species (e.g., oysters)
Other
human transport
Why don’t species always
survive when transported?
unsuitable
physical/chemical conditions
inferior
competitive abilities
susceptable
to predation
Are there generalities about those
invasive species that do survive?
They
come from a community with more species
They
are generalists, not highly specialized
The
species invades without its normal predators/parasites/competitors
There
is an empty “niche”
Physical/chemical
conditions are similar
Examples of non-native species on
West Coast
Pacific
oyster (Crassostrea gigas) –
introduced from Japan
-
grow more rapidly than indigenous species
-
superior competitors
-
but most places is unable to reproduce (with exceptions)
American
lobsters – introduced from Atlantic coast
-
no lobsters present in Canadian West Coast, niche appears vacant
-
reproduction appeared normal
-
did not survive for unknown reasons
A more successful example is
described: Neries diversicolor invading
Caspian Sea
-
became very common without apparent impact on native species
Impact on indigenous species is
hard to predict
-
Sargassum muticum and Ocenebra japonica are examples of invasive
species
on West Coast
-
Some more damaging than others
Species tend to increase through
time over evolutionary time
-
See Fig. 16.4 (Figure based on recently deceased paleontologist, Jack Sepkoski)
-
Whole communities suffered dramatic extinction events, generally due to
extrinsic
factors, not due to being “out-competed”
-
Early communities lacked deep burrowers, etc.
Read about impact of Ice Ages up to
p. 388!
Ch. 17 – Additions of
Materials to the Oceans
Additional review questions:
What are the sources of pollution
entering oceans?
shipwrecks,
dumping, airborne
What are PAHs and why do they tend
to become concentrated in marine sediments?
How does “oil” differ
depending on the variety?
What is the behavior of spilled
oil?
What are treatments for dealing
with oil spills?
Why is there a question about
whether or not to spray dispersants on oil spills?
Lecture notes – Chapter 18
(Harvesting the sea)
Fishing adds a predator
Affects
target species
–
largest individuals are taken first
–
average size of individuals decreases
Examples:
Canadian
West Coast ling cod
Peruvean
anchovies
South
African pilchards
–
not necessarily damaging until size decreases to
size
of reproductive maturity
Affects
predators of target species
Example:
Pinnipeds
feeding on pollock in Alaska
Affects
prey of target species
Example:
Krill
near Antarctica
Fishing can impact non-target
species
Examples:
Pacific
squid drift nets and incidental catch
1989
season:
500
turtles
4,000
northern fur seals
14,000
albatrosses
24,000
dolphins
186,000
dark shearwaters
228,000
skipjack tunas
1,163,000
blue sharks
1,377,000
albacores
31,748,000
pomfrets
Pacific
yellowfin tuna fishery in 1960s
200,000
to 500,000 dolphins
Ghost
fishing (abandoned gear or nets)
Overfishing – fishing harder
than needed
It
is probable that we could catch more fish with less effort in most fisheries
Maximum
sustained yield (MSY)
maximum
tonnage of organisms that could be taken from a harvested
population
each year without eventually destroying the population
measured
in metric tons (tonnes)
Catch
per unit effort (CPUE)
tonnage
of the catch divided by the amount of effort invested in
obtaining
it
–
CPUE goes up quickly in unexploited population
–
increases until MSY level is reached
–
then CPUE goes down
–
best if intermediate-size individuals are selectively taken
–
this leaves the fewer, larger, individuals for reproduction
Examples:
plaice
prior to WWII
Global
fisheries –
Are
we close to the MSY for all the oceans?
–
United Nations estimates by Food and Agriculture Organization (FAO)
–
these do not include “artisanal” catch (taken by individuals for
their own
food
or for trading)
–
artisanal catch is estimated to add another 28%
John
Ryther (WHOI) has estimated the productivity of all oceans (Fig. 18-9)
–
his estimate of 242 million tonnes is approx. 3X 1987 harvest levels
–
estimates for MSY for all oceans varies from 60 to 100 million tonnes
–
United Nations assessment from 1987 reports that only 25 of the
280
stocks of fishes worldwide are presently “underexploited”
or
“moderately exploited”
Krill
is the most significant stock that is presently underutilized
–
these are near Antarctica (as unaccessible as they can get, making
their
havest costly)
–
they taste/appear like cooked maggots
–
market for “fish meal” is uncertain
–
present high levels are likely a reflection of removal of baleen whales
–
exploiting these stocks would likely affect the many mammals and
birds
that depend on them
Aquaculture
In
terrestrial environments, we vastly increase the amount of food
that
is produced by farming
Some
types of aquaculture have tremendous potential for producing
protein
–
even though we get only 2% of our calories from
the
sea, we get 12% of our protein
Examples:
Shellfish
Nori
–
both take advantage of tides to bring food/nutrients to
farmed
organisms
–
both produce much more protein per unit area than
comparable
farms on land
Salmon
rearing to fry stage is similar in that it takes advantage of the ocean’s
nutrients/food
Other
types of aquaculture require 4 to 8 times more protein than they provide
Example:
Salmon
farming
Aquaculture
can also have many damaging effects
disease
compete
with native populations
introduction
of invasive species