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Lecture 12

BIOC63Fall2013 Lecture 12.docx

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Biological Sciences
Karen Williams

BIOC63Fall2013 Lecture 12 Notes: Threats to Biodiversity – Oceans Calcifying organisms: hard corals  Coral reefs are like the rainforests of oceans  1% of sea surface area 25% of marine biodiversity  food basis for diverse coral reef community  they also provide habitat for a number of marine organisms  skeleton made of calcite (CaCO3) Corals  symbiosys between polyp (animal) and zooxanthellae (algae)  polyp provides protection and space for algae to reside in and provides nutrients for algae to grow   algae is on the top (so it can get sun because it is photosynthetic)  algae because is photosynthesizing provides oxygen and some sugars to the polyp Coccolithophores  marine food base : phytoplankton  50% of phytoplankton are diatoms  20% coccolithophors  have shells made up of calcite  30% others  they are tiny but you can photograph from space because they are in big groups (milky blueish white in picture)  Mollusks  shells made up or aragonite (still CaCO3, but different molecular structure) Man-made acidification of oceans   smaller graph at the top right  carbon dioxide concentration in atmosphere increases in the shape of a hockey stick towards the 2000s 1   bigger graph at the bottom  pH used to be stable at around 8.1-8.2, after the 1800s decreased, to now about 8  predicted to be 7.8 in 2100  correlate  increase in CO2 concentration in the atmosphere, pH also decreased Calcifying organisms and acidification  do not need to know the chemical formulas and etc.   carbon dioxide pulled into ocean, where it combines with water and from bicarbonate  but gives a H+  the carbonate ion from calcite can then combine with the H+ because it has a higher affinity, making HCO3-  so even though we are increased carbon dioxide in the atmosphere, the amount of CO3-2 in the ocean is becoming less, so we have less and less hard corals Future ocean acidity   red line = optimal conditions  above red line = calcification  can build hard corals  underneath red line = no coral building, and the corals that are there will start to dissolute Coral reefs and global warming  there is a bleached coral = dead  sea temperature increases  stress polyps  expelling of symbiotic algae (kind of like sweating out the algae) without the algae, the polyp dies  this occurs if the temperature is greater than 30 degrees for a few days T-dependent past bleaching events 2   22 and 41% bleached in North America   El Nino events  everything gets really hot  The problem now is that the time between these spikes is less and less  trouble for calcifying organisms  They are not just more often but they are also worse (more frequent and more severe) T and coral calcification   Rate of calcification decreasing  Extension decreasing (how far does the coral extends, location wise)  Density decreasing   Temperature of the sea surface in the N and S region is slowing going up (Great barrier reef picture) - effects of acidification and effect of global warming = double whammy Climate change : double whammy 3   A  B : decreasing concentration of carbonate ion that is available for calcifying organisms and also increasing the Temperature, atmospheric CO2 increases  This would result in
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