The diatoms are perhaps the most well-known and beautiful of all the phytoplankton. They typically inhabit cold, nutrient-rich water, but, in fact, they are found just about everywhere. Benthic forms (cells that live attached to the bottom) are common in rivers, lakes, and even the seashore. Their characteristic yellow-brown color is caused by fucoxanthin, an accessory pigment. Accessory pigments assist chlorophyll in catching radiant energy by having absorption bands at different wavelengths than chlorophyll. In this way, changes in the spectral distribution of light can be compensated by making more accessory pigments. This ability of diatoms and other phytoplankton to change the amount and type of pigments in response to changes in the intensity and spectral distribution of light is called photoadaptation.
Through photosynthesis, phytoplankton consume carbon dioxide on a scale equivalent to forests and other land plants. Some of this carbon is carried to the deep ocean when phytoplankton die, and some is transferred to different layers of the ocean as phytoplankton are eaten by other creatures, which themselves reproduce, generate waste, and die.
are the most common type of phytoplankton.
The carbon-14 technique is the most widely used method for determining primary productivity today. Moreover, the method of hanging bottles from a line (attached to a buoy) is preferred over other means (such as incubating bottles on deck under screens that simulate the amount of sunlight). This method of placing bottles on a line is known as in situ productivity measurements. In situ methods are preferred because they duplicate most closely the underwater light field experienced by phytoplankton. Both the intensity of light, which varies with depth and can be affected by clouds or waves, and the spectral distribution of light, which may be affected by other particles or phytoplankton suspended in the ocean, are reproduced using in situ methods.
25/02/2014 · Zooplankton vs Phytoplankton
For these reasons, oceanographers at the University of Southern California set out to find a non-intrusive method for measuring the photosynthetic rate of phytoplankton. Nonintrusive methods rely on measuring ocean properties as they exist, not by subjecting the ocean to any perturbations. These passive measurements work much like the tricorders on Star Trek. By pointing your instrument at a particular spot, you can determine certain properties of that spot, such as whether "signs of life" are present. Along those lines, you might say that the USC oceanographers were attempting to develop oceanic tricorders!
Marine Phytoplankton Benefits, A Nutrient Dense …
However, the C-14 method is not without its problems. In the real ocean, phytoplankton do not live in a bottle. Potential artifacts are introduced as phytoplankton are collected, poured into a bottle, and thrown overboard on a line. Contamination of the sample, container effects (i.e. the presence of a surface on which bacteria may proliferate), rapid decline of sensitive organisms (such as small gelatinous zooplankton) and other potential problems throw into question whether the bottle incubation method gives a realistic number for phytoplankton production. In addition, the bottle method fails to duplicate mixing within the water column, a process that could have considerable effect on the chemical and light environments phytoplankton experience throughout the day.
Marine Phytoplankton's Powerful Micronutrients
In this method, samples of seawater are typically collected before dawn, carefully placed in clean polycarbonate bottles, inoculated with radioactive "carbon dioxide" (actually, C-14 bicarbonate is added), and suspended at different depths in the euphotic zone of the water column. After a period of time, typically one day (sun-up to sun-down) but sometimes as short as 2 hours, the bottles are collected, the phytoplankton are filtered onto glass fiber filters, and the filters are placed in a liquid that emits a photon of light for every radioactive decay. Using a scintillation counter, an instrument that measures these flashes of light, oceanographers can determine how much carbon was "fixed" into the cells of phytoplankton during photosynthesis.