Biological Productivity in the Ocean Part I

Overview Productivity is related to photosynthesis, which is affected by sunlight and nutrients. Productivity is globally and seasonally variable. Feeding relationships are represented by food chains and food webs. Oceans are being overfished.

Primary Productivity Primary productivity = storage of energy in organic matter that comes from a non-organic source like the sun (not from other plants or animals) Photosynthesis uses solar radiation. Chemosynthesis uses chemical reactions. 99.9% of the ocean’s biomass relies directly or indirectly on photosynthesis for food.

Energy to Food: Photosynthesis

Cyanobacteria

Cyanobacteria Diatoms

Cyanobacteria Dinoflagellates Diatoms

Seagrass Dinoflagellates Diatoms

Seagrass Dinoflagellates Kelp

Seagrass Mangroves Kelp

Photosynthesis vs. Respiration Photosynthesis: Creates food & releases O2, daylight only Respiration: Burns food, releases CO2, day and night

Measurement of Primary Productivity Directly – capture plankton in plankton nets Measure radioactive carbon in seawater Monitor ocean color with satellites Green pigment chlorophyll SeaWiFS

Ocean Chlorophyll – SeaWiFS Satellite

Factors Affecting Primary Productivity Nutrient availability Nitrate, phosphorous, iron, silica Most from river runoff Productivity high along continental margins Redfield ratio – C:N:P proportions usually 106:16:1 for most phytoplankton

Factors Affecting Primary Productivity Solar radiation Uppermost surface seawater and shallow seafloor Compensation depth – net photosynthesis becomes zero (O2 produced = CO2 produced) Euphotic zone—from surface to about 100 meters (330 feet)

Light Transmission in Ocean Water Blue wavelengths penetrate deepest Longer wavelengths (red, orange) absorbed first

Transmission of Light in Seawater

Color in the Ocean Color of ocean ranges from deep blue to yellow- green Factors Turbidity from runoff Photosynthetic pigments (chlorophyll) Eutrophic (high CHL) Oligotrophic (low CHL) Secchi Disk – measures water transparency

Upwelling and Nutrient Supply Cooler, deeper seawater is nutrient-rich. Areas of coastal upwelling are sites of high productivity.

Types of Photosynthetic Marine Organisms Anthophyta Seed-bearing plants Macroscopic (large) algae Microscopic (tiny) algae Photosynthetic bacteria

Anthophyta Only in shallow coastal waters Primarily grasses and mangroves Eelgrass

Surfgrass

Young Mangroves

Young Lemon Shark in mangrove roots

Upside-down Jelly in Mangrove roots

Anthophyta Mangrove seed pods

Mangrove Swamps in Florida Keys

Macroscopic Algae “Seaweeds” Brown algae Green algae Red algae

Macroscopic Algae Southern Sea Palm Elk Kelp

Giant Kelp

Giant Kelp Attach to rocks with holdfasts Unlike roots • Do not absorb nutrients • Do not take in water • Sole function is to hold plant in place

Giant Kelp & Urchin Predators

Microscopic Algae Produce food for 99% of marine animals Most are planktonic (“free-floating”) Diatoms – tests (shells) made of silica Coccolithophores – plates of calcium carbonate Dinoflagellates – tail-like flagella

Microscopic Algae Diatoms silica-shelled organisms dominant in colder water diatomaceous ooze

Microscopic Algae Coccolithophores carbonate-shelled organisms dominant in warmer waters

Microscopic Algae Coccolithophores carbonate-shelled organisms dominant in warmer waters

Microscopic Algae Dinoflagellates Two whip-like flagella for propulsion

Microscopic Algae Dinoflagellates “Red tides” Toxic algal blooms Phosphorescence But most not harmful Lingulodinium polyedrum

Microscopic Algae Dinoflagellates Lingulodinium polyedrum, San Diego County

Microscopic Algae Dinoflagellates Zooanthellae photosynthesize inside corals and provide nutrients: Symbiotic relationship

Photosynthetic Bacteria Cyanobacteria Extremely small May be responsible for half of total photosynthetic biomass in oceans Very important: bring new nitrogen into marine ecosystems

Photosynthetic Bacteria