state of the oceans portfolio committee 13 february 2013
TRANSCRIPT
Reported parameters
RV Algoa 1. OCEAN PHYSICS – Warm and cold episodes
– Temperature
– Ocean Currents
2. ATMOSPHERIC MEASUREMENTS– Wind speed, direction
– Air pressure
3. OCEAN CHEMISTRY– Oxygen
– Heavy Metal Pollution
– Nutrients
4. OCEAN BIOLOGY– Plankton
– Biodiversity
– Protected species (birds, whales, sharks, etc)
Annual Cycles and Long-term trends
Weaker summer southeasterly winds – warm episodes - hence less upwelling.
Stronger summer southeasterly winds – cold episodes- Hence more upwelling.
• Warm & Cold episodes approx every 3-4 yrs
Wind Speed & DirectionAssociated with warm and cold episodes.
Sea Surface Temperature (SST) - satellite data – over large scale - changes in SST indicates intensity of upwelling. - varies from season to season. - changes in the SST
• SST above average: Summer 2009/10 (except January 2010)
Cold summer SST – strong easterly winds – intense upwelling
Upwelling:-cold bottom water pushed to surface.-West Coast – cold nutrient rich water to surface.-Stimulates the food chain
• Changes in wind affect the Temperature
Nutrients
Nitrates: most important - phytoplankton.Silicates: 2nd most important.
• Moving offshore – nutrient content decreases with warmer water.• Nitrates and Phosphates: - steady increase since 1978 and declining since 1990’s.
If nutrients decrease - overall reduction in phytoplankton. - overall reduction in zooplankton. - eventually reduction in fish.
What we do not understand is what causes the changes in the nutrient content.
Oxygen
Low Oxygen concentration at bottom.Low Oxygen nearer to the shore.
2006-2008:: low concentrations extended 140-170 km offshore. - coincided with cool SSTs, relatively high upwelling and high chlorophyll concentrations (lots of phytoplankton). - decay(rotting) of phytoplankton consumes Oxygen lead to low Oxygen conditions - Rock Lobster walkout. (Lobster breathe Oxygen. Under low Oxygen conditions they suffocate and die in tonnes).
1951 – 2010:•Long-term, 100-fold increase in zooplankton abundance, but decrease since mid-1990s.
•Change in composition of species.
•Shift from large-species to small-species dominance: Know from other areas – associated with ocean warming.
•Geographic shift in species such as sardine & anchovy to South-East – factories stranded on West Coast.
Zooplankton(Microscopic organisms)
• Pollution monitoring
- Lead, Cadmium, Zink, Copper, Iron, Manganese, Mercury.
- Important elements for pollution status.
- Use mussels as an indicator species in that it grows in one place and it filters sea water around it.
Data collected – needs analysis and interpretation.
Seabirds
- indicators of marine ecosystem health.
Declines in population size:
-Prey (Sardine & Anchovy; Rock Lobster) has shifted Southwards and Eastwards.
African Penguin Cape CormorantBank Cormorant
In Summary:
• Increase in wind speed and direction (southeaster) – more intense upwelling – more nutrients – more phytoplankton / zooplankton and fish.
• Increase in intensity of winds – increase in storminess.
• Decline in Seabirds as a result of decrease in food availability – associated with environmental change.