IMS 17 - Primary Productivity

Primary Productivity

Definition

·         Carbon amount fixed by organism through organic matter synthesis using energy from solar radiation and chemical reactions

2 types

·         Solar radiation / photosynthesis

·         Chemical reaction / chemosynthesis

Gross Primary Production (GPP)

·         Total organic matter produced by photosynthesis & respiration / time

Respiration

·         Process by organism using organic matter as energy source

Net Primary Production = GPP – Respiration

Photosynthetic Marine Organism

·         Macroalgae seaweed & Microalgae phytoplankton

·         Chlorophyta, Phaeophyta, Rhodophyta

Nutrient Availability

·         Affects life distribution

·         Phytoplankton: nitrate, phosphorus, silica, iron (aid photosynthesis)

Nutrient Source

·         Runoff, erosion (major source)

·         Max life concentration @ continental margin

·         Photosynthesis restricted to uppermost surface

·         Compensation depth (net photosynthesis 0)

·         Compensation depth @ open ocean = 100 m

·         Compensation depth @ coast = 20 m (suspended inorganic matter / microscopic organism)

·         Nutrient importance > Solar

Ocean Colour

·         Turbidity from runoff

·         High photosynthetic pigment, high biological production

·         Coast & upwelling area productive, yellow-green colour coz microscopic algae & suspended particle

·         Open ocean lack productivity, clear indigo colour

·         Eutrophic @ high latitude & upwelling area

·         Oligotrophic @ low productivity open ocean

Regional Productivity

·         Unit = grams of carbon fixed / square meter / time

·         Avr primary productivity ~50 g C/m²/yr

·         Range 20 – 300 g C/m²/yr

·         Thermocline prevent vertical mixing

Polar Ocean Productivity

·         Press & density little change with depth, isothermal, x barrier preventing vertical mixing

·         Summer; ice melting form thin low saline layer, plankton stay sunlit, x sink

Tropical Ocean Productivity

·         Permanent thermocline; prevent mixing; low productivity

·         High productivity @ equatorial & coastal upwelling

·         Coral reef adapted to low nutrient condition with symbiotic algae

Temperature Ocean Productivity

·         Winter

o   Isothermal, thermocline absent

·         Spring

o   Deeper euphotic zone; spring bloom occurs; solar energy & nutrient high

o   Seasonal thermocline trap microalgae; late spring thermocline gone

·         Summer

o   Surface water warm; storng thermocline; nutrients deplete

·         Autumn

o   Surface water cool; thermocline gone; nutrient replenished

Fall bloom occur (less dramatic & short-lived than spring bloom coz of winter near)