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Just What Lives in the Ocean Anyway? Biological Oceanography
Intro - DID YOU KNOW?
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20% of the world’s protein supply comes from the ocean and since the world land-based
protein production is nearing its limit; people are turning to the oceans to supply food for a
growing population. Many under-utilized fish species are now being caught for food, increasing
pressure on ocean resources.
Promoting biodiversity or the variety and abundance of living organisms in any water system
ultimately improve the health of the oceans.
Oceans act as a vast highway for the billions of creatures that live there.
The shells of tiny diatoms (one-celled phytoplankton) are used in toothpaste, kitty litter, and
swimming pool filters.
When most people think about the ocean, they usually picture one of the larger water
animals. We all know what a whale (mammal) or a shark (fish) looks like. These are the top
carnivores, the top of the food pyramid, and the last in a chain of feeders that starts with the
abundant but very small plankton. Some whales are at the top of a short food chain that ends
with them because they filter plankton for food. Plankton supports all life in the oceans.
In order to begin a discussion of the study of biological oceanography, there are key
terms you need to understand that are specifically used to describe the workings of the ocean as
they relate to living systems.
Part 1: Get into a group of three to five people and pick up the Ocean Zones and
Characteristics Activity. Follow the instructions and have me check your selections before
continuing! 
The ocean has several “layers” or zones with specific properties, abiotic and biotic
influences, as well as types of marine life. Under the key headings, sort and match all of the
properties and characteristics for each. When you have had your work checked, prepare your
own working definitions and descriptions for each key heading, perhaps as a concept map or
other graphic organizer. Put the clues back in the envelope and return to me.
Part 2: Watch the video clip - http://www.youtube.com/watch?v=u2QRNzeirgU (9:40 min)
Then read the following information presented in “Open Ocean Biological Oceanography”
and respond to the questions on the sheet as indicated.
If you would like more information, “By the Sea” http://www.glf.dfo-mpo.gc.ca/sci-sci/byseaenmer/index.html has many pdf files and weblinks available.
Other useful resources –
http://www.dfo-mpo.gc.ca/canwaters-eauxcan/index_e.asp Canadian Water Network
http://www.ec.gc.ca/water/en/info/gloss/e_gloss.htm Environment Canada Water Glossary
http://www.fao.org/fi/glossary/default.asp Food, Agriculture Organization U.N. Glossary
http://inter01.dfo-mpo.gc.ca/waves2/index.html (library search engine)
http://www.glossarist.com/gsearch.asp (glossary search engine-general)
Open Ocean Biological Oceanography
What are the key issues regarding life in the open ocean? Although some issues are of
particular interest to scientists, most should be of interest to all people, as they ultimately affect
the health of our planet. Organisms that live in depths of the open ocean cannot survive out of
water for long periods. Fish are a main source of concern, since they are the organisms we eat
most often. Protein from the sea is important for feeding the world population. These protein
sources are spread over a wide area and constantly moving. Efficient fishing methods have
reduced their abundance, making them harder to find. Overall the open ocean is like a vast desert
in terms of productivity, so any shift in the balance of species present can be harmful to overall
ecosystem health.
 Plankton – The Tiny Ones
The productivity of the open ocean is fueled by the production of plankton. Organisms
that remain planktonic for their entire life cycle are called holoplankton. Plankton can be
generally separated into two groups, plants (phytoplankton) and animals (zooplankton).
Phytoplankton production depends on sunlight and nutrients. Areas of higher productivity are
associated with coastal areas with higher sunlight and nutrient levels. The phytoplankton group is
made up of two large families, the diatoms and the dinoflagellates.
Diatoms are the most abundant phytoplanktonic photosynthesizers (98%) compared to
the other group the dinoflagellates (2%). Diatoms come in a variety of shapes, but one feature
common to most is that they are microscopic and composed of two halves of silica-based shells
that fit together like a pill box. Dinoflagellates look like flying saucers with whiskers; these
appendages help them to stay near the top of the water column. Both of these species can be
responsible for poisonings associated with eating shellfish.
Zooplankton is the tiny animal plankton that eats phytoplankton. They are passive
swimmers and tend to move up in the presence of sunlight and to sink back down in the evening.
This adaptation allows them to feed or graze on a new section of phytoplankton each day as the
surface water moves carrying the phytoplankton with it. Part-time plankton (meroplankton) are
usually the larval stages of larger organisms such as clams, scallops, cod and herring. These
organisms spend the early stages of their life cycle feeding, growing and developing in the
topmost portion of the water column. Zooplankton is an important food source for smaller fishes
and large whales. For example baleen whales, such as the humpback, strain larger zooplankton,
known as krill, in quantities of up to thousands of kilograms in a single mouthful.
 Seaweed – Have You Eaten Any Lately
Marine plants of the open ocean are known as seaweed. Sargassum, or gulfweed, a
brown algae, is the most common floating species. It is estimated that over 7 million tonnes lie in
an area known as the Sargasso Sea off the coast of Bermuda. This sea covers an area  60 % the
size of Canada. The coastal shore contains the majority of seaweeds that survive by attaching to
the bottom. These seaweeds consist of red, brown and green algae. Besides contributing to
photosynthesis, they provide shelter, food, breeding and egg laying locations to many species
that co-exist with them. Certain extracts from seaweeds are used in many products you eat or use
every day.
 Mobile and Hard to Catch - Nektons
The swimming fishes and the organisms that live near the bottom tend to be larger but
less numerous in the open ocean. Many species tend to migrate with the seasons as they swim
long distances to breed and locate food. Many of these fish species are food items that people
have gathered over the centuries. Our local Atlantic salmon, probably the most famous
recreational fish species from this area, is famous for leaving and returning to birth rivers each
year. The larger swimming organisms, or pelagic fish, are very popular as food items. The most
important commercial fish was once cod, which are now fished on a limited basis, as the fishery
was closed for conservation and management purposes in 1994. Other recognizable fish we catch
and eat include tuna, halibut, sole, pollock, mackerel, herring and hake.
In the open ocean, the whale fishery has ended for most species and has been replaced by
whale watching enterprises. Humpback, fin, minke, blue and right whales are species that are
often seen in the Atlantic region. These are the baleen representatives that feed extensively on
copepods in our warmer waters in the summers. A right whale can, for example, consume 4 % of
its body mass every day. The tooth whales such as the orcas, sperm, porpoises and dolphins are
often found in the waters around the Atlantic coast but usually farther out to sea. Porpoises and
dolphins have a tendency to come closer to shore in search of food. Seals make up the last
grouping of larger swimming mammals in the Atlantic region. The four most common species
are the Grey, Harbour, Hooded and Harp seal.
 Seafloor Animals - Careful Where You Step
The deepest areas of the open ocean have a remarkable variety of unique organisms that
most of us will never see alive. Scientists use remote sensing devices to study, photograph and
collect these creatures from the bottom depths. Below 200 m there is no light (aphotic), so these
organisms live in complete darkness and use other primary energy sources besides light. Coastal
regions and surface waters, where more light is available (euphotic and dysphotic), contain much
higher densities of organisms. Organisms that are found on, in or close to the bottom are referred
to as benthic organisms or benthos. The majority of these are invertebrates or organisms that lack
an internal skeleton.
Molluscs have a wide variety of body shapes, from the crawling snails to the sessile,
filter feeding mussels to swimming octopuses. Some of these we can eat others we cannot. Some
molluscs you may have heard of include oysters, mussels, clams, scallops, snails, periwinkles,
dog whelks, limpets and squids. Crustaceans have external skeletons and include the everpopular lobster, snow crab and shrimp. Barnacles, isopods and amphipods are smaller but no less
important with regard to their role in the overall ecosystem. Echinoderms are benthic animals
with five-star symmetry. On the beach you can easily find sand dollars and starfish, while sea
urchins are abundant in certain locations farther out. Brittle stars and sea cucumbers are found in
even deeper water. In the sand and muddy bottoms, a variety of worms can be found. Other
invertebrates that are recognizable include sponges, sea anemones and leafy bryozoans.
 Coastal Biological Oceanography
All of the organisms mentioned above, and more, can be found at one time or another in
the coastal zones of the Atlantic region. One of the more interesting places to visit is exposed
tide pools during low tide. The coastal zone is a harsh environment, and the exposure to
desiccation, salinity changes, wave action, wind and ice are dominant forces that the living
organisms will encounter daily and seasonally. The special adaptations that organisms have
developed to survive in these conditions are unique. For example:
Marine plants have developed a holdfast system that allows them to attach to exposed,
solid surfaces like rock. The strength of this holdfast is evident when you consider they can resist
the ripping effect of strong waves and wind during intense storms. Mussels have attachment
structures called byssal threads that are equivalent to animal holdfasts. Other molluscs have
strong adductor muscles that close their shell halves to keep them from drying out (desiccation)
during exposure. Barnacles close their tops to achieve the same effect. Other organisms burrow
deep into the bottom substrate to avoid predators and weather.
Plankton reproduces in massive numbers to ensure perpetuation of the species; many fish
use the same survival strategy as eggs, larvae and adults are consumed by organisms higher up in
the food chain. The coastal zone is very rich in nutrients from land-based and shoreline sources.
This is one reason that “blooms” or exponential population explosions can occur more readily
near the shore.
Many species have poisonous appendages to deter predators. Unique camouflage has
always been a main method of reducing detection by predators. Examples of this are too
numerous to explore in detail, but one is fairly universal: most fish have white undersides
(ventral) and dark backsides (dorsal). This is because looking up, a predator sees light, and a
white underside blends in more effectively; similarly, looking down the dark colour of the
backside also blends in, making the fish harder to detect.
All kinds of birds frequent the coastal areas to feed. Gulls are by far the most commonly
observed species. Bird populations become smaller farther out to sea. Mudflats can be covered
with hundreds of thousands of individual semi-palmated sandpipers in the late summer as the
birds fatten up on Corophium for their long migration south. Many species of ducks stop to feed
in the coastal region both coming and going during their migrations. The coastal region of the
Atlantic is a vast and diverse set of ecosystems. This is reflected in the tremendous diversity of
living things that can be found there if you know where to look. 
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Questions:
Name: __________________________
1. The general term given to the tiny organisms at the base of all ocean food webs is:
________________________
2. How much of the world’s protein supply is from the oceans? ____________
3. What does “autotroph” mean?
4. The proper name for plant plankton is _________________________, while animal
plankton is called ____________________________.
5. Diurnal (daily) vertical migration, or DVM, is a phenomenon displayed by what group of
small organisms with limited swimming ability? Why do they do this?
6. Why do we refer to the larval stages of larger swimming fishes and crustaceans as
meroplankton?
7. Would you say that there are more floating or more attached (sessile) seaweeds on the
planet? Explain.
8. If there is no light for a primary energy source in the deep ocean, what do you suppose
some organisms use instead?
9. What structure do marine plants use to attach to the bottom substrate? _______________
10. Why do most fish in the ocean have a dark-coloured dorsal side (top of fish)?
11. Where in the Maritimes could you go to see thousands of the migratory semi-palmated
sandpipers feeding in the late summer? (For a bonus, do you know what they are eating?)
12. What is the difference between plankton and nekton?
13. List three key abiotic factors that characterize the neritic, pelagic and abyssal zone.
Determine in which zone the greatest biodiversity might be found. Why?