IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth Lecture 7 Ocean Color and Phytoplankton Growth

This lecture includes the following topics: 1. Chlorophyll and photosynthesis 2. Vertical distribution of phytoplankton in the ocean 3. Estimation of phytoplankton biomass from satellite ocean color observations 4. Estimation of chlorophyll fluorescence from MODIS ocean color observations 5. Estimation of coccolithophores concentration and harmful algal blooms IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass 7. Global phytoplankton biomass and primary production

1. Chlorophyll and photosynthesis Green color of plants, including phytoplankton, is a result of plant pigments, primarily chlorophyll a. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

Chlorophyll absorbs light energy and stores it in the form of chemical agent ATP. This energy is used for the synthesis of organic matter. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 1. Chlorophyll and photosynthesis

The synthesis of organic matter by plants (primary production) is a basic source of food for all living organisms. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 1. Chlorophyll and photosynthesis

2. Vertical distribution of phytoplankton in the ocean Photosynthesis cannot proceed without light; so, in the deep layer phytoplankton growth is “light limited” Another requirement for photosynthesis is a sufficient concentration of nutrients (nitrates, phosphates, iron, etc.). In stratified water nutrients in the upper mixed layer are consumed by phytoplankton; so, phytoplankton growth there is “nutrient limited”. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

2. Vertical distribution of phytoplankton in the ocean The growth of phytoplankton occurs in the layer where both light and nutrient concentration are sufficient. With increase of the upwelling nutrient flux the conditions of phytoplankton growth become better and the maximum of its vertical distribution moves to more shallow layer. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

2. Vertical distribution of phytoplankton in the ocean The growth of phytoplankton occurs in the layer where both light and nutrient concentration are sufficient. With increase of the upwelling nutrient flux the conditions of phytoplankton growth become better and the maximum of its vertical distribution moves to more shallow layer. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

2. Vertical distribution of phytoplankton in the ocean The growth of phytoplankton occurs in the layer where both light and nutrient concentration are sufficient. With increase of the upwelling nutrient flux the conditions of phytoplankton growth become better and the maximum of its vertical distribution moves to more shallow layer. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

2. Vertical distribution of phytoplankton in the ocean When nutrient flux is very intensive and phytoplankton biomass is high, the maximum of vertical distribution of phytoplankton is located at the surface. The result is a direct correlation between total phytoplankton (or chlorophyll) concentration in water column (or within the euphotic layer) and in the thin surface layer. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

2. Vertical distribution of phytoplankton in the ocean Hence, both the surface chlorophyll concentration and the chlorophyll concentration above the penetration depth can be used as a measure of water productivity, i. e., phytoplankton biomass. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

2. Vertical distribution of phytoplankton in the ocean Vertical distribution of ecosystem characteristics at a typical station in the oligotrophic waters shows deep phytoplankton maximum and nutricline. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

2. Vertical distribution of phytoplankton in the ocean Vertical distribution of ecosystem characteristics at a typical station in the eutrophic boreal waters shows shallow phytoplankton maximum and nutricline. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

2. Vertical distribution of phytoplankton in the ocean What layer contributes to the color of ocean surface? D e p t h ( m ) Light Vertical attenuation of sun light (I) with depth (Z) can be described by exponential equation I z = I 0 *exp(-k*Z) Deeper from the surface - less light is reflected or scattered by phytoplankton cells and contributes to the color of ocean surface. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

2. Vertical distribution of phytoplankton in the ocean What layer contributes to the color of ocean surface? I z = I 0 *exp(-k*Z) Coefficient K is called “attenuation coefficient”; it is measured in 1/m. The value 1/K is called “attenuation length”, and the layer of this length is called “penetration depth” ( Z pd ). Another depth used in ocean optic is “euphotic depth” ( Z e ); it is defined as the depth where the downwelling PAR (Photosynthetically Active Radiation) is reduced to 1% of its value at the surface. These two values are related by empirical equation Z pd  Z e / 4.6 IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

2. Vertical distribution of phytoplankton in the ocean What layer contributes to the color of ocean surface? The C sat (averaged concentration "seen" by a remote sensor) is computed as follows: C sat is correlated with phytoplankton biomass in water column. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

3. Estimation of phytoplankton biomass from satellite ocean color observations Empirical models are based on direct correlations between normalized water-leaving radiation and chlorophyll concentration. Semi-analytic models are based on the Inherited Optical Properties (IOPs) of water column, i.e., absorption and backscattering of different water constituents (phytoplankton, suspended sediments, CDOM, etc.). It is assumed that chlorophyll concentration in phytoplankton is a constant. In practice, chlorophyll content varies within a wide range.

4. Estimation of chlorophyll fluorescence from MODIS ocean color observations. Recent studies of the College of Oceanic and Atmospheric Sciences at Oregon State University. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

4. Estimation of chlorophyll fluorescence from MODIS ocean color observations.  p +  f +  h = 1 Light energy not used for photosynthesis is lost as heat and fluorescence. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

4. Estimation of chlorophyll fluorescence from MODIS ocean color observations. Light emitted by chlorophyll Light absorption by algal pigments Light absorption by algal pigments IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

4. Estimation of chlorophyll fluorescence from MODIS ocean color observations. Regular method to calculate Chl fluorescence : use Fluorescence Line Height IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

4. Estimation of chlorophyll fluorescence from MODIS ocean color observations. Fluorescence can be used as another measure of chlorophyll, but only in chlorophyll-rich water, because the optical signal produced by chlorophyll absorption substantially exceeds the signal of fluorescence. ADVANTAGE: Absorption-based algorithms fail in waters where there are other materials that absorb and scatter and are not correlated with chlorophyll –Sediment –Dissolved organic matter Chlorophyll fluorescence is specific to chlorophyll LIMITATION: it also depends on physiology IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

4. Estimation of chlorophyll fluorescence from MODIS ocean color observations. MODIS successfully estimates FLH from space even in low chlorophyll case 1 waters IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

4. Estimation of chlorophyll fluorescence from MODIS ocean color observations. Φ P + Φ F + Φ h = 1 P – photosynthesis; F – fluorescence; H – heat. Φ h (heat) is assumed a constant; Estimation of chlorophyll concentration assumes Φ F  constant Estimation of primary production assumes a predictable relationship between Φ F and Φ P IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

4. Estimation of chlorophyll fluorescence from MODIS ocean color observations. Physiological parameters (APR and CFE) vary spatially. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

4. Estimation of chlorophyll fluorescence from MODIS ocean color observations. The patterns of variability of phytoplankton physiology estimated from fluorescence can be used in for evaluation of photosynthesis and primary production. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

5. Estimation of coccolithophores concentration and harmful algal blooms. Coccolithophores are small algae containing coccoliths – inorganic carbon structures. The blooms of coccolithophores result in very intensive water surface backscattering and hinder remote- sensed estimation of phytoplankton biomass. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

5. Estimation of coccolithophores concentration and harmful algal blooms. From typical to coccolithophores backscattering spectra we can now estimate the biomass of these algae. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

5. Estimation of coccolithophores concentration and harmful algal blooms. Optical measurements of MODIS enable estimation of not only chlorophyll a concentration, but also concentrations of pheopigments, which are produced by zooplankton during grazing. Decreased concentration of pheopigments indicates absence of grazing typical to harmful algal bloom. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

5. Estimation of coccolithophores concentration and harmful algal blooms. This image shows the area of harmful algal bloom near the Pacific coast of Central America. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

6. Seasonal cycles of phytoplankton biomass One of the main goals of remote-sensing observations is the study of seasonal cycles of phytoplankton biomass in different regions of the World Ocean. In many regions these cycles repeat every year including minor details. This pattern is a result of seasonal oscillations of physical environment. In high latitudes these oscillations are more pronounced, and the response of phytoplankton is more evident.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass Typical pattern of seasonal variations of phytoplankton in temperate latitudes is known since the beginning of 20th century. The main feature is a short-period (1-2 weeks) "vernal bloom" called in parallel with seasonal cycle of terrestrial plants. The cycle contains the period of exponential growth and then abrupt decrease resulting from grazing of phytoplankton by zooplankton.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass The hydrological conditions of start of the spring bloom of phytoplankton were described and explained by Harold Sverdrup in He attributed the beginning of spring bloom to the formation of seasonal thermocline, when the upper mixed layer is separated from deeper water column and phytoplankton Is retained in illuminated (euphotic) layer. The strengthening of seasonal thermocline in summer results in nutrient limitation of phytoplankton growth.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass Stratification within the euphotic layer is a primary factor controlling phytoplankton growth. We consider two main factors limiting phytoplankton growth: illumination and nutrients. Light limitation is crucial under low stratification (e. g., winter convection), because algae cells are dispersed by turbulent mixing within deep dark layers. Nutrient limitation is crucial under enhanced stratification (e. g., seasonal thermocline in summer), because nutrients do not penetrate into the euphotic (i. e., well illuminated) upper mixed layer. The hydrometeorological factors (heat flux, wind, freshwater load with precipitation and river discharge) either increase or decrease the stratification within the euphotic layer.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass Typical seasonal cycles of phytoplankton result from the combined effect of seasonal cycles of hydrometeorological factors influencing water stratification within the euphotic layer. The most illustrative is the phytoplankton seasonal cycle in mid-latitudes with two maxima in spring and autumn:

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass SeasonHydrometeorological factors StratificationPhytoplankton growth WinterMaximum wind mixing; Maximum cooling of upper layer Deep convection Winter minimum resulting from light limitation SpringWind mixing weakens; Heating of upper layer increases Formation of seasonal thermocline Spring bloom SummerMaximum heating of upper layer; Minimum wind mixing Maximum stratification Summer minimum resulting from nutrient limitation FallCooling of upper layer increases; Wind mixing increases Erosion of seasonal thermocline Autumn bloom

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass In high latitudes (cold and windy) winter minimum is more pronounced and summer minimum is less pronounced. In low latitudes (warm and less windy) winter minimum is less pronounced or absent and summer minimum is more pronounced. Deviations from typical seasonal pattern of hydrometeorological factors result in local peculiarities of phytoplankton cycle.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass Typical seasonal cycles of phytoplankton described by Alan Longharst are given below. He distinguishes eight types of cycle. The figures illustrate pigment concentration (Chl), primary production (P), mixed layer depth (Zm), and the period when the picnocline is illuminated (■ ■).

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass Typical seasonal cycles of phytoplankton described by Alan Longharst are given below. He distinguishes eight types of cycle. The figures illustrate pigment concentration (Chl), primary production (P), mixed layer depth (Zm), and the period when the picnocline is illuminated (■ ■).

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass Typical seasonal cycles of phytoplankton described by Alan Longharst are given below. He distinguishes eight types of cycle. The figures illustrate pigment concentration (Chl), primary production (P), mixed layer depth (Zm), and the period when the picnocline is illuminated (■ ■).

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass Typical seasonal cycles of phytoplankton described by Alan Longharst are given below. He distinguishes eight types of cycle. The figures illustrate pigment concentration (Chl), primary production (P), mixed layer depth (Zm), and the period when the picnocline is illuminated (■ ■).

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass Near Newfoundland two different water masses (cold Labrador Current and warm Gulf Stream) are separated by frontal zone.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass Four small regions were selected in the zones of influence of the Labrador Current, the Gulf Stream, and over shallow and deep parts of the Newfoundland Bank. Seasonal patterns were typical to Arctic, coastal, mid-latitude, and subtropical regions.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass Seasonal patterns were typical to Arctic, coastal, mid- latitude, and subtropical regions.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass In April 1999 unusual wind pattern (weak wind in northern part and strong wind in southern part) resulted in stronger bloom of phytoplankton. Weak wind in northern (light-limited) zone enhanced stratification; strong wind in southern (nutrient-limited) zone eroded thermocline; both favored phytoplankton growth.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These images show seasonal variations of plant pigment concentration in in the Ligurian Sea. January 1998, March 1998, and August 1998 Subtropical seasonal cycle with summer minimum and higher chlorophyll concentration during winter- spring is evident.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These images show seasonal variations of plant pigment concentration in in the Ligurian Sea. March 1999, April 1999, and May 1999 In 1999 typical to mid- latitudes spring bloom was observed.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass Significant correlation was revealed between air temperature contrast in autumn and the magnitude of spring bloom next spring (CZCS and SeaWiFS data).

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass Cold and windy autumn of 1998 preceded vigorous spring bloom in spring Explanation: 1. Deeper winter convection and enrichment of the upper layer with nutrients. 2. Cold winter and warm spring favors formation of seasonal thermocline.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These SeaWiFS monthly composite images averaged over and NCEP wind data illustrate seasonal variations of California upwelling. Stronger wind and increased phytoplankton biomass are observed in summer.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These SeaWiFS monthly composite images averaged over and NCEP wind data illustrate seasonal variations of California upwelling. Stronger wind and increased phytoplankton biomass are observed in summer.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These SeaWiFS monthly composite images averaged over and NCEP wind data illustrate seasonal variations of California upwelling. Stronger wind and increased phytoplankton biomass are observed in summer.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These SeaWiFS monthly composite images averaged over and NCEP wind data illustrate seasonal variations of California upwelling. Stronger wind and increased phytoplankton biomass are observed in summer.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These SeaWiFS monthly composite images averaged over and NCEP wind data illustrate seasonal variations of California upwelling. Stronger wind and increased phytoplankton biomass are observed in summer.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These SeaWiFS monthly composite images averaged over and NCEP wind data illustrate seasonal variations of California upwelling. Stronger wind and increased phytoplankton biomass are observed in summer.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These SeaWiFS monthly composite images averaged over and NCEP wind data illustrate seasonal variations of California upwelling. Stronger wind and increased phytoplankton biomass are observed in summer.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These SeaWiFS monthly composite images averaged over and NCEP wind data illustrate seasonal variations of California upwelling. Stronger wind and increased phytoplankton biomass are observed in summer.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These SeaWiFS monthly composite images averaged over and NCEP wind data illustrate seasonal variations of California upwelling. Stronger wind and increased phytoplankton biomass are observed in summer.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These SeaWiFS monthly composite images averaged over and NCEP wind data illustrate seasonal variations of California upwelling. Stronger wind and increased phytoplankton biomass are observed in summer.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These SeaWiFS monthly composite images averaged over and NCEP wind data illustrate seasonal variations of California upwelling. Stronger wind and increased phytoplankton biomass are observed in summer.

IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 6. Seasonal cycles of phytoplankton biomass These SeaWiFS monthly composite images averaged over and NCEP wind data illustrate seasonal variations of California upwelling. Stronger wind and increased phytoplankton biomass are observed in summer.

MODIS OCEAN NET PRIMARY PRODUCTION (ONPP) Authors: Behrenfeld & Falkowski Net Primary Production NPP = f (Chl a, PAR, SST) Integrated over the Euphotic zone (i.e., the depth of 1% of incident Photosynthatically Available Radiation - PAR) IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth 7. Global phytoplankton biomass and primary production

3. Estimation of phytoplankton biomass from satellite ocean color observations Chlorophyll a Input fields (measured by MODIS): IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

3. Estimation of phytoplankton biomass from satellite ocean color observations Photosynthetically Available Radiation Input fields (measured by MODIS): IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

3. Estimation of phytoplankton biomass from satellite ocean color observations Sea Surface Temperature Input fields (measured by MODIS): IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

3. Estimation of phytoplankton biomass from satellite ocean color observations H – day length (hours); PAR - Photosynthetically Available Radiation; Chl – Surface Chlorophyll a concentration; Z eu - Depth of euphotic zone (power function of Chl ); P b opt - Optimal Photosynthetic Yield (7-th order polynomial function of Sea Surface Temperature). Equation: IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth

3. Estimation of phytoplankton biomass from satellite ocean color observations Resulting NPP are estimated for 8-day intervals at global grid of 4.5- km resolution. IoE The Basics of Satellite Oceanography. 7. Ocean Color and Phytoplankton Growth