Taxonomic Classification In the ocean hardly represented ...oceanography.asu.edu/Oc_Nov21_pos.pdf · Classification of marine organisms according to habitat and mobility Marine organisms

Taxonomic ClassificationTaxonomic Classificationof Organismsof Organisms

• 3 domains of life:–Archaea–Bacteria–Eukarya

Figure 13-1

In the oceanIn the oceanhardly represented.hardly represented.

Only in coastalOnly in coastalocean, mangroves ocean, mangroves and swamps and swamps (eelgrass, (eelgrass, surfgrasssurfgrass), ), and salt marshes.and salt marshes.

Classification of marine organisms according to habitat

and mobilityMarine organisms can be classified into

one of three groups based on habitat and mobility:

1. Plankton (floaters)• Phytoplankton (drifting algae)• Zooplankton (drifting phagotrophic protists and

animals)• Bacterioplankton, Archaea (marine prokaryotes

either free floating or attached)

2. Nekton (swimmers)3. Benthos (bottom dwellers)

Metabolic Classification

• Depending on Carbon source used: heterotrophic vs autotrophic

• Depending on the Energy source:Chemosynthesis, Photosynthesis, Respiration, Fermentation

See Handout!

Classification according to size

Picoplankton (see last handout) is the group with the smallest cells, measuring anywhere from 0.2 – 2 µm (1 µm = 10-3 mm or 10-6 m).

Nanoplankton measures from 2-20 µm.

Microplankton measures from 20-200 µm (= 0.2 mm)

Mesoplankton measures from 200-2000 µm (= 2 mm)

Macroplankton is larger than 2 mm –20 mm (= 2 cm)

Megaplankton is larger than 2 cm

Classification according to developmental stages

• E.g., squid experience benthic, planktonic, and nektonic stages

• Squid are considered meroplankton(opposite = holoplankton)

Classification of marine organisms according to habitat

and mobilityMarine organisms can be classified into

one of three groups based on habitat and mobility:

1. Plankton (floaters)• Phytoplankton (drifting algae)• Zooplankton (drifting phagotrophic protists and

animals)• Bacterioplankton, Archaea (marine prokaryotes

either free floating or attached)

2. Nekton (swimmers)3. Benthos (bottom dwellers)

Phytoplankton(examples)

– Diatoms (Phylum Chrysophyta, Class Bacillariophyceae)

• silica test resembles a pillbox– Coccolithophorids (Phylum Chrysophyta, Class

Prymnesiophyceae)• calcite plates form a spherical test

– Dinoflagellates (Phylum Pyrrhophyta)• Produce a test made of cellulose• Posses a whip-like flagella• Bioluminescence (biological production of light by

organisms)• Exist in great abundance, creating red tides (harmful

algae blooms)

Diatoms and dinoflagellates

15-4

Diatom life cycle Coccolithophorids: The most abundant eukaryotes on Earth

A vast bloom of Trichodesmium visible fromspace - Photo NASA.

Tufts of Trichodesmium

Cyanobacteria

Trichodesmium floats on the surface of tropical/subtropical oceans and is one of the most important nitrogen fixers in the ocean.

Very small phytoplankton(picoplankton and nanoplankton) are the most important group of phytoplankton in the open ocean.

They can only be visualized by high magnification in the microscope.

The glow of these cells (Synechococcus)comes from the fluorescence of theirphotosynthetic pigments(epifluorescence microscopy).

Single celled cyanobacteria

Classification of marine organisms according to habitat

and mobilityMarine organisms can be classified into

one of three groups based on habitat and mobility:

1. Plankton (floaters)• Phytoplankton (drifting algae)• Zooplankton (drifting phagotrophic protists and

animals)• Bacterioplankton, Archaea (marine prokaryotes

either free floating or attached)

2. Nekton (swimmers)3. Benthos (bottom dwellers)

© Springer-Verlag 2002

Natural diets of vertically migrating zooplankton in theSargasso Sea

A. Schnetzer1, 2, and D. K. Steinberg1, 3

Ciliates:Phagotrophic protists that feed on bacteria, and other pico- and nanoplankton

heterotrophic dinoflagellate: Noctiluca Radiolaria and Foraminifera

Some microzooplankton (phagotrophic protists) Meso-zooplankton: Copepods

• Copepods are planktoniccrustacea.

• They filter phytoplankton out of the water

• They have a hard exoskeleton and a segmented body with jointed legs

Figure 15-5

Macro-zooplankton : Krill (Euphausiids)

• Krill are related to copepods but are larger in size

• Abundant in Antarctic waters, where they are a favorite food of the largest whales

Figure 15-6

Megaplankton : Salps(planktonic tunicates) Megaplankton : Cnidarians

• Cnidarians are soft-bodied organisms including:– Hydrozoans:

Siphonophores(Portuguese man-of war)

– Scyphozoans (jellyfish)

Figure 15-7

With the advent of diving missions, researchers such as Bruce Robison are uncovering the secret watery world of jellies — some, for instance, dine on jelly themselves.

Back home: some crustaceans, such as this amphipod, settle down and raise their young atop a jelly.

Depth charge: Shinkai 6500 gives researchers a rare glimpse of the deep ocean's delicate jellies.

Jelly fishJelly fish((ScyphozoaScyphozoa))

Nature Nature 426426, 12 , 12 -- 14 ( 2003)14 ( 2003)

Classification of marine organisms according to habitat

and mobilityMarine organisms can be classified into

one of three groups based on habitat and mobility:

1. Plankton (floaters)• Phytoplankton (drifting algae)• Zooplankton (drifting phagotrophic protists and

animals)• Bacterioplankton, Archaea (marine prokaryotes

either free floating or attached)

2. Nekton (swimmers)3. Benthos (bottom dwellers)

© Springer-Verlag 2002

Natural diets of vertically migrating zooplankton in theSargasso Sea

A. Schnetzer1, 2, and D. K. Steinberg1, 3

Bacteria that float in the ocean (single cells, in aggregates, detritus).Most are very small (avg. 0.5 µm) and are heterotrophic (respire dissolved organic substances).

Bacterioplankton:

Marine Viruses!“Femptoplankton”, are not Bacteria but infect Bacteria

Very small <0.2 µm

107 viruses/ml of sea water

Major cause of mortality for bacteria and phytoplankton

Extremely important for global biogeochemical cyclesNature 437, 15 Sept 2005