Chapter 8 Key Concepts

Diatoms are single-celled phytoplankton that usually have a silica shell and often dominate the phytoplankton, especially at high latitudes.
Dinoflagellates usually have two flagella, are somewhat mobile, and have an organic skeleton. They are dominant members of the phytoplankton later in the summer in midlatitudes and may always be dominant in lower-latitude phytoplankton.
Coccolithophores secrete a skeleton consisting of calcium carbonate plates and are sporadically dominant in phytoplankton throughout the world.
Copepods, important worldwide members of the microplankton, include dominant consumers of phytoplankton and also species that are predators on smaller zooplankton.
Krill are members of the crustacean order Euphausiacea, are larger than copepods, and are important grazers in surface waters of upwelling systems throughout the world.
Scyphozoa are the true jellyfish, and siphonophores are colonial animals with polyps specialized for different functions (e.g., feeding and reproduction). Both groups are abundant in the world ocean and feed on food ranging from phytoplankton to smaller animal prey, including both invertebrates and fishes. A colonial hydrozoan, Velella, is sometimes found on the sea surface in great numbers.
Comb jellies are gelatinous and usually feed by means of ciliated rows and sometimes tentacles that capture zooplankton such as copepods.
Protists are common in the plankton and usually feed on smaller prey such as bacteria, or they may be photosynthetic. They are an important link between microorganisms and larger animals in the oceanic food web.
Microorganismal planktonic diversity cannot be assayed by use of visual techniques alone.
Polymerase chain reaction can be used to develop probes to sample and enumerate major plankton groups.
Immunofluorescence is a useful immunological technique to probe for phytoplankton species.
Next-generation sequencing allows a complete survey of the microbial community with a water sample.