Primary Production Global chlorophyll concentrations for Oct. 2000
Primary Productivity • Photosynthesis • Involves the use of light energy in the conversion of inorganic carbon into organic carbon. • Photosynthetic organisms include: terrestrial plants, seaweeds, phytoplankton, blue-green algae, and zooxanthellae.
Primary Productivity • Chemosynthesis • Involves the use of energy released by the catalysis of certain inorganic reaction to convert inorganic carbon into organic carbon. • Chemosynthetic organisms include: hydrothermal vent bacteria.
Table 1. Average net primary production and biomass of aquatic habitats. Data from R.H. Whittaker and G.E. Likens, Human Ecol. 1: 357-369 (1973).
Primary Production Limitations • light • nutrients Photic Zone Photosynthesis No Photosynthesis Aphotic Zone
Primary Productivity • Gross Primary Productivity (GP) • The rate of production of organic matter from inorganic materials by autotrophic organisms • Respiration (R) • The rate of consumption of organic matter (conversion to inorganic matter) by organisms. • Net Primary Productivity (NP) • The net rate of organic matter produced as a consequence of both GP and R.
Primary Productivity NP = GP + R Note that R is a negative value because it results in the reduction of organic matter.
Plankton Size Picoplankton (.2-2 µm) Nanoplankton (2 - 20 µm) Microplankton (20-200 µm) Macroplankton (200-2,000 µm) Megaplankton (> 2,000 µm) microplankton picoplankton nanplankton
zooplankton phytoplankton Photosynthesis: light + 6CO2 + 6H2O C6H12O6 + 6O2 decomposition Light & Dark Experiments Respiration: C6H12O6 + 6O2 6CO2 + 6H2O
buoy light bottle dark bottle respiration photosynthesis + respiration weight
LIGHT LEVELS have a major impact on productivity: • light intensity • - with depth • - penetration depends on water clarity • light quality • changes with depth • longer (e.g., red) more quickly • amount of light • - to little or too much light inhibit photosynthesis • primary production • - different primary producers peak production at • different light intensities • (algae >diatoms>dinoflagellates) • compensation depth • - depth at which rate of photosynthesis = rate of • respiration
VERTICAL MIXING also influence productivity: • critical depth • depth at which net photosynthesis per mixing cycle exceeds net respiration • determined by the time spent at different depths due to vertical mixing • Upwelling zones • Thermocline layer • Diurnal vertical migration • Langmuir vortices
NUTRIENTS often limit productivity: • inorganic nutrients • - nitrogenous compounds (NO3, NO2, NH3) • - phosphates (PO4) • trace elements may also be important (e.g., Fe, • Cu) • nitrate concentrations in rich seawater 1/10,000 • of rich soil • nutrients produced by: • - excretion • - surface runoff • - upwelling
Productivity varies TEMPORALLY and SPATIALLY: • generally highest over continental shelves; over the shelf itself it is highest just offshore • seasonality more pronounced at high latitudes • at mid latitudes, productivity peaks both spring and fall
Primary Production biomass zooplankton phytoplankton Winter Spring Summer Fall North Atlantic- temperate climate
Arctic zooplankton phytoplankton Winter Spring Summer Fall
Tropical zooplankton phytoplankton Winter Spring Summer Fall