Marine and Aquatic Ecosystems

By Darlene Graham,2014-06-19 07:28
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Marine and Aquatic Ecosystems

Marine and Aquatic Ecosystems

    Differences between aquatic/marine and terrestrial systems ; One hundred times more inhabitable space

    ; More stable temperature regime

    ; No water shortage, but light or nutrients may be limiting ; Primary producers are mostly microscopic and have quick turnover ; Most aquatic grazers are ectotherms and have low metabolic costs = large relative population sizes

Marine and aquatic ecosystems

    ; Aquatic/marine ecosystems are influenced by local characteristics of climate, soil, water chemistry and water depth and also by adjacent terrestrial ecosystems

    ; Aquatic/marine systems are very productive

    ; There is less oxygen in water than in air

     Colder water can hold more oxygen

     Oxygen depletion can be an issues in warm areas

Aquatic habitats

    ; Life depends on oxygen availability

     Oxygen per liter is only 5% of that in the atmosphere

    ; Oxygen added by photosynthesis and aeration from the atmosphere ; Oxygen is removed by animal and detritivores respiration, and through decaying organic matter


    ; In both marine and aquatic systems, habitat is set up into zones ; Both have a photic zone (where light penetrates) and an aphotic zone (too deep for light to penetrate)

     Depth of penetration varies with water clarity

Marine ecosystems

    ; Saltwater ecosystems cover vastly more total area and contain much greater volume of water than all freshwater bodies combined

Ocean productivity

    ; Open ocean is not productive

    ; Upwelling and coastal areas are productive

Marine ecosystems

    ; Vertical stratification is an important aspect of many aquatic ecosystems

     Organisms tend to form distinctive vertical sub-communities

    ; Neritic Coastal shallow waters over continental shelves

    ; Benthic - Bottom sub-community

     Low oxygen levels

    ; Pelagic - Water column

Neritic zone

    ; Coral Reefs - Accumulated calcareous skeletons of colonial organisms (coral)

     Depth limited by light penetration

     Among most endangered communities

Georges Banks

Intertidal region

    ; Part of the neritic zone that is exposed due to tides ; Also called littoral zone

    ; Rocky intertidal zones are well-studied


    ; Mangrove trees grow in salt water

     Occur along calm, shallow, tropical coastline

Other coastal habitats

    ; Barrier Islands - Low, narrow, sandy islands that form offshore from a coastline

     Protect inland shores from surf

     Prized for human development

    ; Loss of vegetation triggers erosion


    ; Estuaries - Bays or semi-enclosed bodies of brackish water that form where rivers enter the ocean

    ; Important for fish and shellfish reproduction

Pelagic zone

    ; Consists mostly of plankton

     Small animals, algae, bacteria, etc.

     Photosynthetic plankton account for 40% of all photosynthesis on earth

     Photosynthetic plankton live in top 100 m of ocean where light penetrates ; Nekton are larger organisms


Benthic zone

    ; Benthic zone in coastal areas

    ; Benthic zone in open ocean is a stressful environment

     Rely on food scraps from world above

     Seasonless, 2-5?C, pressure of 400-500 atms

     Some are chemoautotrophic hydrothermal vents with sulfur oxidizing


Freshwater habitats

    ; Strongly connected to terrestrial systems

    ; Large amount of material enters water from surrounding land ; Small water bodies are ponds (shallow enough for rooted vegetation throughout), larger water bodies are lakes but line between them is not


Freshwater ecosystems

    ; Lakes

     Non-flowing water

     Freshwater lakes have distinct vertical zones separated by temperature ; Rivers

     Flowing water


    ; Lakes have three zones that depend on depth and distance from shore

     Littoral zone

     Limnetic zone

     Profundal zone

Lake stratification

    ; Lakes form layers in summer due to temperature differences and lack of circulation

     Water is most dense at 4?C and least dense at 0?C

    ; These two zones are called the epilimnion (warmer surface water) and the hypolimnion (colder deep water)

    ; The thermocline, an abrupt change in temperature, separates these two layers

; Nutrients accumulate in hypolimnion

    ; Thermal stratification tends to cut off the oxygen supply to bottom waters leading to anoxia in oxygen depleted waters


    ; Turnover mixes these two stagnant layers

Lake productivity

    ; Lakes can be classified based on their levels of productivity

     Eutrophic lots of nutrients and organic matter

     Oligotrophic nutrients and organic matter are scarce

Plant nutrients and cultural eutrophication

    ; Eutrophication - Process of increasing nutrient levels and biological productivity

     Some amount of eutrophication is normal

    ; Cultural eutrophication - Increase in biological productivity and ecosystem succession caused by human activities




    ; Land surface is saturated or covered with water at least part of the year

     Swamps, bogs, marshes, etc.

    ; One of most productive ecosystems on earth

    ; Trap and filter water - “nature’s kidney’s”

    ; Provide flood control


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