Week 5

• New Zealand context


  • Significant coastal area with a 15,000 to 18,000 km long coastline
  • EEZ zone of 200 nautical miles, which only NZ can operate within
  • Population is predominantly coastal, 75% of pop lives within 10km of coastline
  • Important part of our identity and is viewed as a taonga (highly prized and protected)
  • Significant in terms of income- fisheries, tourism and resource exploitation
• Marine trophic levels


  Primary producers (phytoplankton, seaweed) then herbivorous consumers, carnivorous consumers and top carnivores
• Food webs


  Complex and interlinked
• New Zealand marine ecosystems

  • Very diverse, 80% of indigenous biodiversity is found in the sea, 7 new species are discovered every week
  • Situated on an active plate boundary, thus impacted by geothermal activity and current systems
  • Significant number of seabirds- 25% of the world's seabirds migrate to breed e.g titi (mutton-bird)
  • 60 distinct marine ecosystems due to unique geography
• Physical factors determining marine ecosystems

  • Depth
  • Temperature
  • Salinity
  • Substrate
  • Water movement (currents and wave action)
• Biological factors determining marine ecosystems

  • Degree of primary production
  • Key organisms
• Benthic (seafloor) ecosystems


  • Salt marsh
  • Mangroves
  • Rocky reefs
  • Beaches
  • Deep sea abyssal plains + trenches
• Benthic ecosystems


  Highly susceptible to the implications of eutrophication/other forms of nutrient depletion and sediment deposition
• Pelagic (water column) ecosystems

  • Sunlight photic zone
  • Dark ocean interior
• Cold vents


  Hydrogen sulphide, methane and hydrocarbon seeps
• Hot hydrothermal vents


  • Fissure in the earth's crust that release got geothermally heated water
  • Found in volcanically active areas like tectonic plate boundaries
• Ecosystem services provided by marine ecosystems

  • Climate regulation
  • Sediment capture and stabilization
  • Carbon capture and sequestration
  • Pollutant capture and sequestration
  • Cycling and storage of nutrients
  • Oxygen production
  • Provision of habitat materials
  • Provision of food (wild and aquaculture)
  • Gas and mineral deposits
  • Biodiversity
  • Recreation
  • Spiritual and cultural values
• Seabirds have been threatened by extinction


  Protection for them was introduced in the 1950s
• Fish stocks have been depleted, and in some cases collapsed


  e.g tuna, snapper, john dory
• 28% of marine mammal species are threatened


  By fishing equipment, ship strikes, pollution and degradation
• Under Marine Mammal Protection Act 1978 they are protected
• Impacts from early Māori

  • Harvested seabirds for food and feathers, some customary harvest continues with titi today
  • Fur seals and sea lions were eliminated
• Impacts from settlers


  • Viewed seabirds as pests, rapid declines in whales, seals and shellfish
• Commercial fisheries


  Established in 1850s, worth 1.4 billion per year
• Aquaculture


  Controlled cultivation of aquatic organisms, began in 1960s and is expanding
• Mineral, oil and gas extraction

  Deep sea mining is becoming key for minerals and oil as we have exhausted what is accessible on land
• New Zealand has extremely diverse marine ecosystems, which provide a range of ecosystem services. However, many resources are being exploited and depleted such as sea birds, fish and resources such as gas, oil and minerals.
• Human impacts on coastal environments

  • Harvesting, direct removal of species
  • Land-based sources of pollution
  • Ocean acidification and warming
  • Sedimentation
  • Introduction of marine pests
  • Run-off, 90% of wastewater treatment is discharged into coastal waters
• Plastic


  Lightweight and strong, thus slow degradation and lots of energy is required for their production
• 1. 12 million tons of plastic enter the ocean each year, 1kg of plastic for every 3kg of fish
• Macroplastics


  Large, visible debris, often mistaken for food and wildlife becomes entangled
• Microplastics


  • Small (less than 5mm) primary are plastic pellets
  • Secondary are formed from breakdown of larger plastic items e.g. wind, wave action, sunlight, friction
• Adverse effects of plastics

  • They are ingested by organisms which then starve, as it feels like they are full
  • Filter and benthic feeders are particularly susceptible
• Plastics are the greatest threat to the marine environment
• Ocean acidification and warming

  • Caused by increased greenhouse gas emissions (CO2, methane, nitrous oxide)
  • 49% of emissions are from GHG emissions, and oceans are absorbing CO2, causing it to become more acidic
• Impacts of ocean acidification and warming

  • Reduces growth and survival rates of species, possibly resulting in a shift towards more invasive species
  • Particularly impacts organisms with calcium carbonate shells, as it dissolves them
• Resources exploited from the ocean

  • Phosphorus
  • Sand
  • Gravel
• Impacts of resource exploitation

  • Significantly disturbs and destroys marine habitats
  • Results in sediment plumes which smother organisms and reduce food availability
• Oil spills


  Oil can spread easily and is toxic to fish and invertebrates, smothering habitats and coating birds and marine mammals
• Oil spill example


  • MV Rena disaster- Oct 2011 Rena struck reef off Tauranga, 400 tonnes of oil leaked from the ship, 2000 seabird deaths, devastating impacts
• Impacts of invasive species and pests


  • They compete with or prey on indigenous species
  • Modify habitats
  • Alter ecosystem processes
  • Affect aquaculture
• Coastal environments are facing cumulative stresses, the most impactful being ocean acidification and warming
• As resources on land are depleted, there is a move towards exploitation of the oceans resources through deep-sea mining