![Page 1: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/1.jpg)
Productivity and the Coral Symbiosis II
![Page 2: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/2.jpg)
![Page 3: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/3.jpg)
![Page 4: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/4.jpg)
![Page 5: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/5.jpg)
![Page 6: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/6.jpg)
• Polyp can survive extended periods with no external food source
• Tight internal N-cycling and algal PS
• Polyp lays down extensive lipid reserves to be drawn on in times of starvation
• High light and high food availability– ejection of pellets containing viable algal cells
• Control of algal cell number ?
• Algae divide within host polyp
![Page 7: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/7.jpg)
• Analyze algal cell
– C,H,O from PS– N,P,S, from host (normally limiting)
• Symbiosis controlled by host
• Polyp controls permeability of algal membrane
• “signal molecules”
![Page 8: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/8.jpg)
• Freshly isolated zooxanthellae
• Incubate in light with 14CO2
• Release very little organic C into medium
• Add some polyp extract - releases lots of organic carbon into medium
• Other cnidarian extracts work
![Page 9: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/9.jpg)
• Alga donates most of it’s fixed C to polyp– used for resp, growth, etc.
• Polyp respires– releases CO2 to alga
• Polyp excretes N waste - NH3
– used by alga
• Polyp also releases PO4-, SO4
-, NO3- to alga
– 1000x more conc. than in seawater– Algae grow faster - helps polyp
![Page 10: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/10.jpg)
FOOD
CHOProtein
AAs Sugars Fatty acids
Alga
Polyp
NH3 CO2 O2
O2
CO2NH3
AAs
Protein
AAs Sugars
CHO
Lipid
ATPNADPH
Fatty acids
Growth & metabolism
Growth & metabolism
glycerol
H2O H2O
LIGHT
PO4- PO4
-
SO4- SO4
-
ATP
![Page 11: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/11.jpg)
• Alga stores CHO – starch• Broken down at night
• Polyp stores lipid – fat bodies• Energy reserve
• Algal PS: 90% fixed C to coral host
• Used for metabolic functions• Growth, reproduction &• Calcium deposition
![Page 12: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/12.jpg)
Calcification - growth of the reef
![Page 13: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/13.jpg)
• In ocean, mostly find 3 forms of CaC03
• Calcite– Mostly of mineral origin
• Aragonite– Fibrous, crystalline form, mostly from corals
• Magnesian calcite– Smaller crystals, mostly plant origin
![Page 14: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/14.jpg)
Calcification
Calcite
Aragonite
Magnesian calcite (Mg carbonate)
![Page 15: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/15.jpg)
• Examples:
organism CaCO3
Molluscs calcite & aragonite
Corals just aragonite
Some green algae just aragonite
Red algae magnesian calcite
Sponges aragonite (with silica)
Some bryozoans all 3
![Page 16: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/16.jpg)
Corals
• remove Ca++ & CO3-- from seawater
• Combines them to CaCO3
• transports them to base of polyp
– Calcicoblastic epidermis
• minute crystals secreted from base of polyp
• Energy expensive– Energy from metabolism of algal PS products
![Page 17: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/17.jpg)
Calcification
![Page 18: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/18.jpg)
CO2 and seawater
• What forms of C are available to the coral ?
• Organic and inorganic forms
• DIC - dissolved inorganic carbon– CO2 (aq)
– HCO3-
– CO3--
![Page 19: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/19.jpg)
• DIC comes from:
– Weathering– dissolution of oceanic rock– Run-off from land– Animal respiration– Atmosphere– etc.
![Page 20: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/20.jpg)
• DIC in ocean constant over long periods
• Can change suddenly on local scale– E.g. environmental change, pollution
• Average seawater DIC = 1800-2300 mol/Kg
• Average seawater pH = 8.0 - 8.2
• pH affects nature of DIC
![Page 21: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/21.jpg)
Carbon and Seawater
• normal seawater - more HCO3- than CO3
--
• when atmospheric CO2 dissolves in water
– only 1% stays as CO2
– rest dissociates to give HCO3- and CO3
--
![Page 22: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/22.jpg)
H2O + CO2 (aq) H2CO3 HCO3- + H+ (1)
HCO3- CO3
-- + H+ (2)
equilibrium will depend heavily on [H+] = pH
relative amounts of different ions will depend on pH
![Page 23: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/23.jpg)
![Page 24: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/24.jpg)
dissolved carbonate removed by corals to make aragonite
Ca++ + CO3--
CaCO3 (3)
pulls equilibrium (2) over, more HCO3- dissociates to CO3
--
HCO3- CO3
-- + H+ (2)
removes HCO3-, pulls equilibrium in eq (1) to the right
H2O + CO2 (aq) H2CO3 HCO3- + H+ (1)
more CO2 reacts with water to replace HCO3-, thus more CO2 has to
dissolve in the seawater
![Page 25: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/25.jpg)
Can re-write this carbon relationship:
2 HCO3- CO2 + CO3
-- + H2O
• used to be thought that
– symbiotic zooxanthellae remove CO2 for PS
– pulls equation to right
– makes more CO3-- available for CaCO3 production by polyp
• No
![Page 26: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/26.jpg)
• demonstrated by experiments with DCMU – stops PS electron transport, not CO2 uptake
• removed stimulatory effect of light on polyp CaCO3 deposition
• therefore, CO2 removal was not playing a role
• also, in deep water stony corals– if more food provided, more CaCO3 was deposited
– more energy available for carbonate uptake & CaCO3 deposition
![Page 27: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/27.jpg)
• Now clear that algae provide ATP (via CHO) to
allow polyp to secrete the CaCO3 and its
organic fibrous matrix
• Calcification occurs 14 times faster in open than
in shaded corals
• Cloudy days: calcification rate is 50% of rate on
sunny days
![Page 28: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/28.jpg)
• Now clear that algae provide ATP (via CHO) to
allow polyp to secrete the CaCO3 and its
organic fibrous matrix
• Calcification occurs 14 times faster in open than
in shaded corals
• Cloudy days: calcification rate is 50% of rate on
sunny days
• There is a background, non-algal-dependent rate
![Page 29: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/29.jpg)
Environmental Effects of Calcification
• When atmospheric [CO2] increases, what happens to calcification rate ?
– goes down
– more CO2 should help calcification ?
– No
![Page 30: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/30.jpg)
• Add CO2 to water– quickly converted to carbonic acid
– dissociates to bicarbonate:
H2O + CO2 (aq) H2CO3 HCO3- + H+ (1)
HCO3- CO3
-- + H+ (2)
• Looks useful - OK if polyp in control, removing CO3--
• BUT, if CO2 increases, pushes eq (1) far to right
• [H+] increases, carbonate converted to bicarbonate
![Page 31: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/31.jpg)
• So, as more CO2 dissolves,
• more protons are released
• acidifies the water
• the carbonate combines with the protons
• produces bicarbonate
• decreases carbonate concentration
![Page 32: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/32.jpg)
![Page 33: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/33.jpg)
• Also, increase in [CO2]
– leads to a less stable reef structure– the dissolving of calcium carbonate
H2O + CO2 + CaCO3 2HCO3- + Ca++
• addition of CO2 pushes equilibrium to right
– increases the dissolution of CaCO3
![Page 34: Productivity and the Coral Symbiosis II. Polyp can survive extended periods with no external food source Tight internal N-cycling and algal PS](https://reader036.vdocument.in/reader036/viewer/2022062305/56649d7e5503460f94a614ed/html5/thumbnails/34.jpg)
• anything we do to increase atmospheric [CO2] leads to various deleterious effects on the reef:
• Increases solubility of CaCO3
• Decreases [CO3--] decreasing calcification
• Increases temperature, leads to increased
bleaching
• Increases UV - DNA, PS pigments etc.