Tsinghua University, SIGS
Chapter 13
Asso. Prof. Yuelu JIANG
Chapter 13 Outline：Pelagic Communities
13.1Zones in the Ocean
Classification of the Marine Environment
Classification of the Benthic Zones
13.2Marine Communities
Competition in Marine Communities
13.3Plankton: Drifters in the Ocean
Plankton Classification
Types of Phytoplankton
Phytoplankton Productivity Varies With Local Conditions
Types of Zooplankton
13.4Nekton
Squids and Nautiluses
Shrimps and Their Relatives
Fishes and Cartilaginous Fishes
Unique Adaptations of Fishes
Sea Turtle and Marine Crocodiles
Marine Birds
Marine Mammals
1307 Ocean Building
Introduction to Oceanography
jiang.yuelu@sz.tsinghua.edu.cn
Pelagic Communities
P1 of 4
Tsinghua University, SIGS
Chapter 13
Asso. Prof. Yuelu JIANG
Key Concepts 13：Pelagic Communities
• A community is composed of the many populations of organisms that interact at a
particular location.
• Physical and biological factors in the environment determine the location and
composition of a community.
• Plankton – drifting organisms – is a category not based on a phylogenetic
(evolutionary) relationship but rather on a shared lifestyle.
• Plankton productivity depends largely on light and nutrient availability.
• Animals that swim are called nekton. The variety of nektonic animals is astonishing,
ranging from tiny crustaceans to the largest whales.
•
Chapter 13 Summary：Pelagic Communities
Definitions of a community and a population, and about the organization of marine
communities. The organisms of the pelagic world drift or swim in the ocean. (Animals
and plants are associated with the bottom are known as benthic organisms.) Pelagic
(suspended) communities are covered in this chapter; benthic (bottom) communities are
discussed in the next.
The organisms that drift in the ocean are known collectively as plankton. The
plant-like organisms that comprise phytoplankton are responsible for most of the ocean's
primary productivity. Phytoplankton -- and zooplankton, the small drifting or weaklyswimming animals that consume them -- are usually the first links in oceanic food webs.
Plankton are most common along the coasts, in the upper sunlit layers of the temperate
zone, in areas of equatorial upwelling, and in the southern subpolar ocean. Marine
scientists have been inspired by the beauty and variety of plankton since first observing
them under the microscope in the nineteenth century.
Actively swimming animals comprise the nekton. Nektonic organisms include
invertebrates (such as the squid, nautiluses, and shrimps), and vertebrates (such as fishes,
reptiles, birds, and mammals). Each organism has a continuously evolving suite of
adaptations that has brought it through the rigors of food finding, predator avoidance, salt
balance, and temperature regulation -- all of the challenges of the marine environment -time and time again.
Introduction to Oceanography
Pelagic Communities
P2 of 4
Tsinghua University, SIGS
Chapter 13
Asso. Prof. Yuelu JIANG
Glossary Chapter 13：Pelagic Communities
abyssal zone – A layer of the pelagic zone covering depths between 4,000 and 6,000 meters (13,123–19685
feet) that never receives sunlight.
accessory pigments – One of a class of pigments (such as fucoxanthin, phycobilin, and xanthophyll) that are
present in various photosynthetic plants and that assist in the absorption of light and the transfer of its energy
to chlorophyll; also called masking pigment.
bathyal zone – Covers seabed on the slopes and down to great depths, where the abyssal zone begins.
benthic – Of, in, or near the sea floor.
brackish – Mixed salt water and freshwater.
cephalopod – A group of marine predators containing squids, nautiluses, and octopuses.
Cnidaria – A category in which invertebrates, such as sea anemones and jellies, belong.
community – Composed of many populations of organisms that interact at a particular location.
copepods – tiny shrimplike animals that compose about 70% of the larger crustacean zooplankters
coral reef – A linear mass of calcium carbonate (aragonite and calcite) assembled from coral organisms, algae,
molluscs, worms, and so on. Coral may contribute less than half of the reef material.
corals – Any of more than 6,000 species of small cnidarians, many of which are capable of generating hard
calcareous (aragonite, CaCO3) skeletons.
diatom – The most productive single-celled alga that has a cell wall composed of silica.
dinoflagellate – Single-celled autotroph with two flagella, occurring in large numbers in marine plankton. Some
produce toxins that can accumulate in shellfish and other filter feeders.
echolocation – The search for prey by reflected sound used by marine animals, such as toothed whales.
estuary – A body of water partially surrounded by land where freshwater from a river mixes with ocean water,
creating an area of remarkable biological productivity.
flagella – Whip-like projection used drive organisms forward or to adjust orientation and vertical positions to
make the best photosynthetic use of available light.
gill membrane – A respiratory organ of fish arranged in thin filaments and plates that diffuses concentrations of
free oxygen dissolved in water into the animal.
habitat – An organism’s “address” within its community, its physical location, which has a degree of
environmental uniformity.
hadal zone – The deepest seabed of all, the trench walls and the floors.
holoplankton – Zooplankton that spend their whole lives in the plankton community.
intertidal zone – The marine zone between the highest high-tide point on a shoreline and the lowest low-tide
point. The intertidal zone is sometimes subdivided into four separate habitats by height above tidal datum,
typically numbered 1 to 4, land to sea.
invertebrate – Animals without backbones, such as squid and nautiluses.
kelps – Large brown seaweed that forms underwater “forests” that support large population of animals.
keystone species – Organisms that play a significant ecological role in the structure and function of an
ecosystem.
krill – Euphausia superba, a thumb-size crustacean common in Antarctic waters.
littoral zone – The band of coast alternately covered and uncovered by tidal action; the intertidal zone.
macroplankton – Animal plankters larger than 1 to 2 centimeters (1⁄2 to 1 inch). An example is the jellyfish.
Mammalia – The class of mammals.
meroplankton – The planktonic phase of the life cycle of organisms that spend only part of their life drifting in
the plankton.
microbial loop – A trophic (feeding) pathway in which heterotrophic bacteria manufacture and consume
dissolved organic carbon.
mollusc – An animal phylum containing bivalves, snails, squid, and octopuses.
nanoplankton – Small plankton between 0.02 and 0.002 millimeter in size.
nekton – Drifting organisms.
neritic zone – The zone of open water nearshore, over the continental shelf.
niche – Description of an organism’s functional role in a habitat; its “job.”
Introduction to Oceanography
Pelagic Communities
P3 of 4
Tsinghua University, SIGS
Chapter 13
Asso. Prof. Yuelu JIANG
Glossary Chapter 13：Pelagic Communities
oceanic zone – The zone of open water away from shore, past the continental shelf.
Osteichthyes – The class of fish with bony skeletons.
pelagic – Of the open ocean; refers to the water above the deep-ocean basins, sediments of oceanic origin, or
organisms of the open ocean.
pelagic zone – The realm of open water. See also benthic zone.
phytoplankton – Plantlike, usually single-celled members of the plankton community.
picoplankton – Extremely small members of the plankton community, typically 0.2 to 2 micrometers (4–40
millionths of an inch) across.
plankton – Drifting or weakly swimming organisms suspended in water. Their horizontal position is to a large
extent dependent on the mass flow of water rather than on their own swimming efforts.
plankton net – Conical net of fine nylon or Dacron fabric used to collect plankton.
population – A group of individuals of the same species occupying the same area.
salt gland – Specialized tissue responsible for concentration and excretion of excess salt from blood and other
body fluids.
schooling – Tendency of small fish of a single species, size, and age to mass in groups. The school moves as a
unit, which confuses predators and reduces the effort spent searching for mates.
Sirenia – The order of mammals that includes manatees, dugongs, and the extinct sea cows.
sublittoral zone – The ocean floor near shore. The inner sublittoral extends from the littoral (intertidal) zone to
the depth at which wind waves have no influence; the outer sublittoral extends to the edge of the continental
shelf.
Teleostei – The osteichthyan order that contains the cod, tuna, halibut, perch, and other species of bony fish.
valve – In diatoms, each half of the protective silica-rich outer portion of the cell. The complete outer covering
is called the frustule.
vertebrate – A chordate with a segmented backbone.
zone – Division or province of the ocean with homogeneous characteristics.
zooplankton – Animal members of the plankton community.
Introduction to Oceanography
Pelagic Communities
P4 of 4