Chapter 15

Salinity Chemical weathering on land creates chemicals picked up by freshwater and delivered to the ocean Mainly sodium chloride Chemicals produced by the Earth as it cooled Chlorine, bromine, sulfur, boron Reducing Salinity Precipitation, runoff, melting icebergs, sea ice melting Increasing Salinity Evaporation and formation of sea ice

Ocean Temperatures more sun = higher water temp Higher latitude means colder water Deeper water is colder Thermocline is the ocean zone where the temperature drops Below thermocline temp stays constant just above freezing

Ocean Density Mass/volume Ocean water is more dense than fresh water so ocean water sinks below fresh water Salinity goes up and density goes up Temperature goes up and density goes down Temperature matters more than salinity Pycnocline Layer of the ocean where there is a rapid change in density – makes it harder for water to mix

Ocean Layering Mixed zone Surface zone – waves, currents, and tides cause mixing Warmed by the sun Transition zone Big temperature drop – includes thermocline Deep zone No sunlight makes it this deep Temperature is just above freezing

Marine Life Most life is in the zones where light penetrates Plankton Drift with the ocean current Phytoplankton – do photosynthesis Zooplankton – eat phytoplankton Nekton Animals that can swim or move without the current Fish, mammals, marine reptiles, squid Benthos Live on the ocean floor

Marine Life Zones Availability of sunlight Photic zone – where light penetrates Amount of plankton, suspended particles, organic particles Euphoric zone – photosynthesis can happen Aphotic zone – lack of light Distance from shore Intertidal zone – land and ocean overlap (between high and low tides) Neritic zone – in photic zone as shore slopes down (continental shelf) Oceanic zone – open ocean Water depth Pelagic zone – open ocean Benthic zone – sea floor Abyssal zone – very deep sea floor

Hydrothermal Vents Found along oceanic ridges Water enters the ocean floor through cracks Super heated water escapes back out the vents When the hot water hits the ocean it cools and minerals precipitate out Chemicals from the vents serve as food for interesting creatures

Primary Productivity Photosynthesis or chemosythesis Make organic compounds from inorganic compounds Requires inorganic chemicals such as nitrogen, iron, phosphorus, carbon Polar regions photosynthesis in summer as well as melting so less dense water keeps the phytoplankton closer to the light Tropical regions Plenty of light year round but thermocline prevents water mixing so nutrients stay deep

Primary Productivity cont… Temperate region Winter – lots of nutrients but very little sunlight Spring – More light and water starts to warm so a thermocline develops trapping phytoplankton near the surface and they use up most of the nutrients Summer – even more sunlight so water gets even warmer and the thermocline gets larger keeping out the nutrients from lower down Fall – less sunlight so temperature drops which allows nutrients to rise again

Oceanic Feeding Producers Algae, plants, bacteria, phytoplankton Greatest biomass in the ocean Herbivores Zooplankton Carnivores Trophic levels Transfer of energy from producers to consumers and finally decomposers Food chain Food Web