Primary production

1. Primary production • Is the production of organic matter by plants which utilize the sun’s energy to make sugar. • Primary producers in the coastal ocean include seaweeds (e.g. kelp beds), seagrasses, and microscopic algae called phytoplankton. Shown as a slide background is a repeating image of the seagrass, Zostera marina, collected in Elkhorn Slough, California in 2000.

2. Photosynthesis • Photosynthesis is the process by which primary producers change light energy into sugar. 106CO2 + 122H2O + 16NO3- + PO43- + 19H+ SUNLIGHT (CH2O)106(NH3)16H3PO4 + 138O2

3. Role of nutrients in photosynthesis • During photosynthesis, cells require nitrate 106CO2 + 122H2O + 16NO3- + PO43- + 19H+ and phosphate as well as other micronutrients such as silicate (Si) and iron (Fe)

4. Factors affecting Primary Production • Because primary production involves photosynthesis, it depends on: Light Nutrients and Temperature All of which are variable in the world’s oceans. Q: Where do you think the greatest annual primary production is?

5. A: The most productive parts of the ocean tend to be in coastal areas(because of high nutrient concentrations) and on the equator, where thereare relatively high temperatures and lots of light. Image source: Earth Observation Research and Application Center

6. Nutrient sources and cycling • Natural sources of nutrients to coastal waters include: 1. weathering of rocks (phosphate and silicate) with nutrients being delivered by rivers or ground water or both 2. rainfall (wet deposition) 3. atmospheric deposition (e.g. Saharan dust) 4. upwelling (where deep ocean water is brought to the surface (e.g. California)

7. Why do we care about furthernutrient inputs to coastal waters? • Under natural conditions, coastal areas receive more nutrients than the open ocean • However, additional nutrient input has the potential to enhance primary production, leading to excess algal blooms The accelerated human-induced input of nutrientsinto water is known as EUTROPHICATION. Q: What are some anthropogenic nutrient sources?

8. Sources of anthropogenic nutrients A: Land runoff from farms and residential areas contains nutrientsfrom fertilizers and animal wastes. Sewage treatment plants are another potential source of nutrients. As are animal production facilities (e.g. hog and chicken farms). With proper management, all of these potential sources could becontrolled to have minimal input to rivers, estuaries and coastalwaters.

9. Pigments used in Photosynthesis • In order for cells to photosynthesize, they need to be able to absorb light. • They do this using pigments, like chlorophyll-a. • Chlorophyll-a is the major photosynthetic pigment in land plants as well as in ocean primary producers.

10. Chlorophyll-a is therefore an indicator of phytoplankton biomass Enclosed in circles are chloroplasts, the organellesinside cells thatcontain chlorophyll

11. Nutrient profiles in the ocean • Nutrients are not vertically homogeneous in the ocean • Profiles arise from biological uptake in surface waters, sinking of biological particulate matter and bacterial remineralization in the water column as the organic matter is respired. • Respiration is the breakdown (or oxidation) of organic matter

12. Respiration is the exact opposite process to Photosynthesis and results in Nutrient Regeneration • Oxygen is required for respiration 106CO2 + 122H2O +16NO3-+PO43-+ 19H+ (CH2O)106(NH3)16H3PO4 +138O2 And as a result, nitrate and phosphate are produced

13. Examples of nutrient profiles Q: If nutrients are depleted in the surface waters, where are the phytoplankton?

14. A. In the surface waters!