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










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


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




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)






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)




        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


                                    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


                                    Pinnipeds feeding on pollock in Alaska


        Affects prey of target species


                                    Krill near Antarctica


Fishing can impact non-target species


                                    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



                                    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



                        In terrestrial environments, we vastly increase the amount of food

                                    that is produced by farming

                        Some types of aquaculture have tremendous potential for producing


                                                – even though we get only 2% of our calories from

                                                            the sea, we get 12% of our protein





                                                – 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



            Other types of aquaculture require 4 to 8 times more protein than they provide


                                    Salmon farming


            Aquaculture can also have many damaging effects



                        compete with native populations

                        introduction of invasive species