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The concentration of chlorophyll A is used as an index of phytoplankton biomass. In the ocean, phytoplankton all contain the chlorophyll pigment, which has a greenish color. Phytoplankton are microscopic organisms that live in watery environments and changes in the amount of phytoplankton indicate the change in productivity of the ocean.
Chlorophyll-a concentration is sometimes used to measure water clarity, especially when suspended sediments and colored dissolved organic matter concentrations are low. Chlorophyll-a concentration is a proxy for phytoplankton biomass, which is one way to quantify how turbid the water is due to biological primary production.
Relationships between Trophic State Index, chlorophyll, phosphorus, Secchi depth, and trophic class (after Carlson 1996) [4] Trophic State Index Chlorophyll (μg/L) Phosphorus (μg/L) Secchi depth (m) Trophic Class < 30—40 0—2.6 0—12 > 8—4 Oligotrophic or hipotrophic 40—50 2.6—7.3 12—24 4—2 Mesotrophic 50—70 7.3—56 24—96
Low-nutrient, low-chlorophyll (LNLC) regions are aquatic zones that are low in nutrients (such as nitrogen, phosphorus, or iron) and consequently have low rate of primary production, as indicated by low chlorophyll concentrations. These regions can be described as oligotrophic, and about 75% of the world's oceans encompass LNLC regions.
The most widely used piece of information from ocean color remote sensing is satellite-derived chlorophyll-a concentration. Researchers calculate satellite-derived chlorophyll-a concentration from space based on the central premise that the more phytoplankton is in the water, the greener it is. [46]
Typical examples include the Leaf Area Index, biomass, chlorophyll concentration in leaves, plant productivity, fractional vegetation cover, accumulated rainfall, etc. Such relations are often derived by correlating space-derived NDVI values with ground-measured values of these variables.
Also, the chlorophyll concentration can be estimated by measuring the light transmittance through the plant leaves [29]. The assessment of leaf chlorophyll content using optical sensors such as Dualex and SPAD allows researchers to perform real-time and non-destructive measurements [30] [31]. Research shows that these methods have a positive ...
A false color SeaWiFS image shows a high concentration of phytoplankton chlorophyll in the Brazil Current Confluence region east of Argentina. Warm colors indicate high chlorophyll levels, and cooler colors indicate lower chlorophyll. SeaWiFS data are freely accessible from a variety of websites, most of which are government run.