State of the Oceans
Portfolio Committee
13 February 2013
Reported parameters
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
RV Algoa
Wind Speed & Direction
Associated with warm and cold episodes.
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
Changes in wind strength and direction
- potential big storms
- amount of rainfall
• Changes in wind affect the Temperature
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
ST HELENA BAY STUDIES:
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).
Zooplankton
(Microscopic organisms)
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.
• 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.
African Penguin
Cape Cormorant
Bank Cormorant
Declines in population size:
- Prey (Sardine & Anchovy; Rock Lobster) has
shifted Southwards and Eastwards.
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.
Thank You