plank_id - Marine Plankton Identification Key P...

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Phytoplankton: The phytoplankton are mainly unicellular plants known as algae. They are found dispersed throughout the photic zone of the oceans and account for the major share of primary productivity in the marine environment. The most important phytoplankton that are presently recognized are those 2-20 μ m in size, which are classified as nannoplankton . The major nannoplankton size groups in the oceans are the diatoms and the dinoflagellates, both unicellular forms of phytoplankton. These organisms may or may not be visible with light microscopy. Please use the enclosed black and white photographs to assist in identifications. Diatoms (class Bacillariophyceae) 1. occur as single cells or in chains or other loose aggregates 2. cell sizes can range 15 μ m - 1000 μ m, although most diatom sizes range from 50 to 500 μ m 3. presence of a porous, rigid cell wall (frustule) made mostly of silica and consisting of two closely fitting halves (epitheca and hypotheca) 4. presence of many small chloroplasts 5. occur in varied shapes: circular, triangular, and modified square shapes are known as centric diatoms (shaped like pillboxes), whereas the elongated ones (bilateral symmetry) are termed pennate diatoms 6. may possess spines or other projections that increase their surface area 7. some common representatives of centric diatoms: Coscinodiscus , Chaetoceros (chain), Thalassiosira (chain), Pseudoeunotia (chain), Asteromphalus, Arachnoidiscus , Navicula (chain), and Triceratium. Some common pennate diatoms are Pleurosigma , Stauroneis , Gyrosigma, Rhizosolenia , Thalassiothrix (chain), Thalassionema (chain), and Nitzchia Dinoflagellates (class Dinophyceae) 1. occur as single cells, rarely in chains or other aggregates 2. cell sizes range from 25 to 1000 μ m, generally smaller than diatoms 3. presence of a porous cell wall made mostly of cellulose. In some armored forms, the cell wall consists of many articulating cellulose plates arranged irregularly over the cell surface 4. most possess several small chloroplasts usually located near the cell ends (a few species are not photosynthetic) 5. typical forms have a body surface with two grooves, each having a flagellum 6. may possess spines, horns or other projections 7. some common unarmored (“naked”) representatives: Gymnodinium , Cystidinium , and Glenodinium . Some common armored species are
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plank_id - Marine Plankton Identification Key P...

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