Marine Life

Plankton – drift with ocean currents (zooplankton, phytoplankton) Nekton – animals that move independently of currents (swim) Benthos – organisms on or in sea floor Classification

Life Zones Availability of Sunlight Photic zone – where sunlight penetrates Varies with water clarity, atmospheric conditions, time of day, latitude, & season. Euphotic zone – where light is strong enough for photosynthesis (up to 100m) Aphotic zone - dark

Life Zones Distance from shore Intertidal – between high and low tides (harsh) Neritic Zone – from low tide mark across continental shelf. (high nutrients, biomass) Oceanic Zone – beyond Neritic Zone – deep, low nutrients Life Zones

Life Zones Water Depth Pelagic Zone – surface to moderate depth, has zooplankton, phytoplankton, & nekton. Benthic Zone – sea floor – crabs, sea stars, burrowing worms. Abyssal Zone – deep ocean floor, abyssal plains, trenches – nutrient poor

Life Zones Hydrothermal Vents – sea water seeps into cracks along midocean ridge, gets ejected hot & saturated with minerals. Heat provides energy for chemosynthesis, minerals provide building blocks.

Productivity Primary Productivity – using light energy (photosynthesis) or chemical energy (chemosynthesis) to make organic compounds from inorganic. Photosyntheis influenced, limited by availability of nutrients & sunlight.

Productivity in Polar Oceans Temp. & density vary little, plenty of mixing between surface & deeper, nutrient-rich water. Limited by solar radiation Phytoplankton peaks in May, stays near surface (melting ice) Zooplankton peaks in June Productivity in Polar Oceans

Productivity in Tropical Oceans Limited by lack of nutrients. Permanent thermocline, no mixing, so cold, nutrient-rich water locked deep, away from phytoplankton. Productivity in Tropical Oceans

Productivity in Temperate Oceans Determined by shifting nutrient supply & sunlight throughout seasons. Winter – low, because solar energy is limited. Days short, sun angle low. Plenty of nutrients, but little growth.

Productivity in Temperate Oceans Spring – fair. More sun & nutrients, but seasonal thermocline traps algae in euphotic zone. Algae bloom uses up nutrients, productivity stops.

Productivity in Temperate Oceans Summer – low High sun angle, much solar radiation, surface warms, strong thermocline prevents mixing.

Productivity in Temperate Oceans Fall – fair Sunlight decreases, thermocline breaks down, mixing begins. Algae bloom, not as much as in spring.

Estuaries Where freshwater rivers empty into ocean. Lower salinity, shallow warm water, nutrient rich. HIGH productivity.

Salinity Total amt. solids dissolved in water Comes from earth’s interior (volcanic) & weathering of rocks. Sea water about 3.5% salinity

Processes Affecting Salinity Usually pretty constant. Variations come from processes that affect water content (add or remove water).

Salinity Salt concentration determines what can live in it. Brine – highest conc., fewest species Brackish – mixture of fresh & saltwater

Ocean Temperatures Surface temperature most affected by amount of solar radiation received. Solar radiation mostly a function of latitude.

Temperature & Depth Thermocline – layer between 300 & 1000 m where temperature decreases rapidly. Below 1000 m, remains constant just above freezing High latitude – cold at surface, no thermocline

Ocean Density Affected by salinity and temperature Saltier = denser Colder = denser Temperature has greater affect on density because it varies more. Pycnocline – layer between 300 & 1000 m where density increases rapidly. No pycnocline at high latitudes.

Ocean Layering Deterimined by density Shallow surface mixed zone – to @ 300 m, mixed by waves, tides, currents, uniform temp., 2% Transition zone – includes thermocline & pycnocline, temp drops, 18% Deep zone – temp constant (low), density constant (high),80%