Marine Ecosystems and Climate

Marine Ecosystems

  • Three broad marine environments:
    • Intertidal zone: close to the shore.
    • Benthic zone: on the floor of the oceans.
    • Pelagic zone: open sea and ocean away from the shore.

Intertidal Zone

  • Area between high and low tides.
  • Can be sandy, rocky, or shingle.
  • Large changes in temperature, oxygen, and salinity.
    • Temperature rises dramatically when the tide is out in sunlight.
    • Oxygen levels increase markedly.
    • Salinity levels can fall with freshwater runoff.
  • Adapted organisms:
    • Mussels, crabs, small fish, barnacles.
    • Invertebrates and bivalves retreat into shells.
    • Anemones retract tentacles.
    • Plants include algae or seaweeds.
  • Adaptation to rapid environmental changes is critical due to two tides per day.

Benthic Zone

  • Seafloor from the intertidal to the bottom of deep ocean trenches.
  • Substrate often mud or fine sediments.
  • Populations of burrowing organisms and shellfish bivalves.
  • Three broad zones:
    • Abyssal zone: 4000 to 6000 meters deep.
    • Bathyal zone: 200 to 4000 meters.

Benthic Ecosystems

  • Three important types just below the intertidal:
    • Seagrass beds
    • Kelp forests
    • Coral reefs
Seagrass Beds
  • Up to 10 meters deep.
  • Seagrass is a higher plant, a seed plant adapted to underwater pollination and seed germination.
  • Ecosystem engineers that modify the environment for other organisms.
  • Provide shelter and food to invertebrates.
  • Found mainly in temperate and tropical waters.
Kelp Forests
  • Brown algae that produce fronds up to 60 meters long.
  • Found on rocky shores.
  • Very productive and dynamic environments.
  • Diversity rivals coral reefs.
  • Found in temperate and Arctic waters.
Coral Reefs
  • Most diverse marine environments.
  • Need continuously warm conditions.
  • Maximum temperature threshold after which corals bleach.
  • Mainly in shallow tropical waters.

Pelagic Environment

  • Open ocean water.
  • Two provinces:
    • Neritic province: near the shore, overlying the continental shelf to around 200 meters deep.
    • Oceanic province: the vast majority of the ocean.
  • Organisms are floaters or swimmers: fish, phytoplankton, zooplankton.
  • In the oceanic province, organisms depend on marine snow.
    • Marine snow: organisms dying in the top layers of the ocean (plankton, small fish, large fish, whales) that drift down and provide food.
  • Organisms adapted for filter feeding, scavenging, and predation on detritus collectors.

Factors Defining World Climate

  • Two key factors:
    • Differential heating of the planet by sunlight and radiant energy.
    • Global atmospheric circulation of air and moisture: interaction of the atmosphere with the oceans and mountains.

Differential Heating

  • Earth's surface illuminated unevenly due to tilt and spherical shape.
  • Sunlight strikes the Earth directly near the equator.
  • Stronger illumination in equatorial regions.
  • Incoming light spread over a wider area in polar regions.
  • Lower intensity of sunlight in polar regions. Hotter at the equator, cooler at the poles.

Seasonal Variation in Radiation

  • Earth's tilt relative to the sun is around 23.5 degrees.
    • June solstice: Northern Hemisphere tilted towards the sun, long days, short nights, higher temperatures.
    • December solstice: Southern Hemisphere tilted towards the sun, long days, short nights.
    • March and September equinoxes: day and night are balanced, equator faces directly towards the sun.
      Orbit around the sun and Earth's tilt shape seasons and solar radiation.

Influence on Wind Patterns

  • Uneven solar radiation influences wind patterns.
  • Heat falling predominantly in polar regions creates columns of air that rise near the equator.
  • Warm air absorbs moisture and releases it as it ascends.
  • Air dries and descends between 23 and 30 degrees latitude.
  • Arid zones where dry descending air spreads out: desert regions (Sahara, Namibia).
  • Movement near the equator drives formation of rotating air currents.

Air Currents and Precipitation

  • Uneven heating drives cells of air currents.
  • Moist air leads to precipitation.
  • Warm, wetter conditions move from tropics to poles.
  • Wet tropical rainforests near the equator due to ascending moisture.
  • Deserts around the Tropic of Capricorn and Cancer due to descending dry air.

Global Wind Patterns

  • Circulating cells of air drive prevailing wind directions.
  • Trade winds: closer to the equator (below 30 degrees), go from east to west.
  • Westerlies: between 30 and 60 degrees north and south, go from west to east.
  • Coriolis effect: deflection of circulating air due to Earth's rotation.

Atmosphere and Ocean Currents

  • Interaction shapes ocean biomes and climate on nearby landmasses.
  • Cold surface currents caused by global wind patterns and Earth's rotation.
  • Warm air in the Gulf Stream warms Europe.
  • Cold currents off the west coast of South America and Africa lead to dry conditions and deserts.

Topography

  • Moisture from the ocean rises over land, cools, and releases rainfall.
  • Leeward side of mountains can have a rain shadow.

Climate and Biome Distribution

  • Climate defines terrestrial biome boundaries.
  • Close matching of climate and biome distribution.
  • Tundra and taiga to the north, tropical regions near the equator, deserts and savannas on either side, and temperate regions in between.

Aquatic Biomes

  • Classifying aquatic biomes:
    • Light is an important determinant.
      • Photic zone: photosynthesis is possible.
      • Aphotic zone: no photosynthesis.
    • Temperature is important.
    • Productivity is important.
      • Oligotrophic: low productivity, deep water, clear.
      • Eutrophic: shallow, nutrient-rich, murky.
      • Trophic: intermediate level of nutrient availability and productivity.

Zoning

  • Freshwater lake:
    • Littoral zone: close to the shore
    • Limnetic zone: open area of the lake away from the shore
    • Profundal zone: a further zone (only in very deep lakes).
  • Ocean:
    • Intertidal at the edge.
    • Pelagic zone: Neritic and oceanic zones.
    • Benthic zone: stretching from the intertidal across the floor of the ocean.
    • Shaping the life at different points in the ocean.
      • Varying conditions form strata.
        • Photic zone: corals, zooplankton, and phytoplankton.
        • Aphotic zone: a range of species related to species in the photic zone.

Marshlands and Estuaries

Marshlands

  • Freshwater environments covered by shallow water.
  • Waterlogged soils and anaerobic conditions.
  • Water-tolerant plants.
  • Slow the flow of moisture and provide flood protection.
  • Absorb and buffer flow rates.
  • Capacity to absorb pollutants.
  • Carbon storage due to limited decomposition.

Estuaries

  • Region where freshwater and saltwater mix.
  • Variable environment: temperature, salinity, light penetration.
  • Highly productive due to nutrients.
  • Tidal action ensures neat fit for main, well-mixed and available water plants.
  • Support biodiversity.
  • Prevent floods during storms (mangrove swamps).
  • Photosynthetic complex of plants.