chapter 3 phytoplankton most primary production in the sea is accomplished by...

Chapter 3

Phytoplankton Phytoplankton

Most primary production in the sea is accomplished by phytoplankton–unicellular, photosynthetic organisms. Hence, marine primary producers are fundamentally different from terrestrial producers.

Phytoplankton Groups

•Most common phytoplankton are from 3 divisions in two kingdoms,– Monera – and Protista.


•Cyanobacteria– Cyanobacteria have been producing oxygen

in the sea for more than three billion years. Today they are everywhere, from intertidal rocks and estuaries to coral reefs and the open sea. Species capable of nitrogen fixation commonly form symbiotic associations with a variety of marine organisms.


•Fig. 3.3 A transmission electron micrograph of a marine cyanobacterium, Synechoccus. (Courtesy of C. Osilin)


•Chrysophyta– Division Chrysophyta is represented in the sea

by nanoplanktonic coccolithophores and silicoflagellates and diatoms that can be macroscopic.


•Fig. 3.6 SEM of three coccolithophore cells, each showing clearly their dense coverings of coccoliths. (Courtesy of F. Reid)

Chrysophyta


•Chrysophyta– Diatoms, often the most important members of

cold-water phytoplankton communities, occur in a large variety of shapes, sizes, and locations.


•Fig. 3.9. An SEM view of Thalassiosira, a coastal diatom, clearly showing the epitheca, hypotheca, and a connecting girdle of cell wall material. (Courtesy of G. Fryxell)

Chrysophyta


•Fig. 3.13 Several common types of temperate-water planktonic diatoms. (Courtesy of F. Reid & K. Lang.)

Chrysophyta


•Dinophyta– Dinophytes dominate warm-water

phytoplankton communities and are unique in their abilities to create light via bioluminescence and powerful toxins that become deadly via the phenomenon of biological magnification.


•Fig. 3.16 SEMs of some common marine dinophytes (Courtesy of E. Venrick & F. Reid)

Dinophyta


•Other Phytoplankton– With improving technology, our understanding of and

nano-, pico-, and ultraplanktonic species is increasing each year.

– These include additional classes of Chrysophyta and members of the division Chlorophyta

Adaptations for a Planktonic Existence

•Phytoplankton confront a persistent dilemma in that they must remain in the photic zone, yet nutrients occur in much greater concentrations near the seafloor. Most of their adaptations are responses to their need to linger near the surface while accumulating nutrients that are in extremely short supply.


•Size– An extremely small cell diameter provides most

phytoplankton with a relatively high surface area-to-volume ratio. This attribute increases frictional resistance to sinking and enables efficient uptake of very dilute nutrients.


•Size


•Size

Fig. 3.17 With increasing size (a, b) the ratio of surface area to volume decreases, unless the larger structure (c) remains subdivided.


•Sinking

Fig. 3.18 Sinking patterns of the elongate diatom, Rhizosolenia (top), and the spiral chain-forming diatom, Asterionella (bottom)


•Adjustments to Unfavorable Environmental Conditions

Fig. 3.19 Inactive resistant stages of two species of Chaetoceros.

Primary Production in the Sea

•Measurement of Primary Production– Estimation of gross and net primary production is

necessary for understanding production potentials of and the quantity of organics available to marine communities.

– Such estimates have been made for nearly 100 years, starting with light-and-dark-bottle techniques and culminating with modern remote sensing via satellites.


•Measurement of Primary Production

Fig. 3.20 The results of a hypothetical light- and dark-bottle experiment.


•Fig. 3.22 This phytoplankton bloom along the California coast, was imaged by SeaWiFS on 10-11 August, 2003 for true color (left) and for chlorophyll a concentrations.


•Factors that Affect Primary Production

– Grazing. Small herbivorous grazers routinely occur at such high concentrations that phytoplankton communities may be destroyed over a period of just a few weeks.


•Fig. 3.24 Generalized population changes of a prey species and its predator, oscillating between unlimited (solid) and limited (dashed) phases of population growth.

Factors that Affect Primary Production

Grazing.


•Fig. 1.21 Fate of sunlight as it enters sea water. The violet and red ends of the visible spectrum are absorbed first.

Factors that Affect Primary Production

Light in Water.



– Light in water. Light is necessary for all photosynthetic organisms, yet it occurs at sufficient intensity only in the relatively shallow photic zone. Consequently, accessory photosynthetic pigments (such as fucoxanthin) are more important in marine producers than terrestrial plants.

Primary Production in the Sea•Factors that Affect Primary Production

Fig. 3.29 Patterns of light absorption for three photosynthetic pigments: phycoerythrin, fucoxanthin, and chlorophyll a. (Adapted from Saffo, 1987.)

Light in Water.

Primary Production in the Sea•Factors that Affect Primary Production

Fig. 3.32 Distribution of dissolved silicate, nitrate, and phosphate in the Atlantic and Pacific oceans. (Adapted from Sverdrup, Johnson, and Fleming 1942.)

Nutrient Distribution.



– Nutrient Regeneration. Marine producers rely on a number of mechanisms of nutrient regeneration, such as turbulent mixing, convective mixing, and upwelling.

Primary Production in the SeaNutrient regeneration

Fig. 3.35 Seasonal growth and decline of thermoclines in tropical (top), temperate (center), and polar (bottom) ocean waters.

Primary Production in the Sea•Factors that Affect Primary Production– Nutrient Regeneration.

Fig. 3.36 Coastal upwelling in the Northern Hemisphere.

chapter 3 phytoplankton most primary production in the sea is accomplished by...

Documents

common phytoplankton

osilin slide

reid chrysophyta slide

fryxell chrysophyta

reid dinophyta slide

division chlorophyta

water planktonic diatoms

increasing size