What are mangroves?

1
Nutrient cycling in mangrove ecosystems
John Cheeseman, Dept of Plant Biology
Sweet is the swamp with its secrets Emily
Dickinson
2
(No Transcript)
3
Mangrove describes a lifestyle, not a taxonomic
unit.
4
Mangroves (the ecosystems) are incredibly diverse.
5
Mangroves (the ecosystems) are incredibly
diverse. In Curaçao, mangroves grow straight out
of (and into) fossil coral, and interspersed with
cacti.
6
Mangroves are highly productive ecosystems.

• Hinchinbrook Channel, Queensland
• Mangroves account for gt50 of C input to
  Hinchinbrook Channel
• gt40 of this goes to benthic respiration and
  burial sinks
• The overall coastal ecosystem at Hinchinbrook is
  net autotrophic.
• 65 of total org-C input is available for export
  to the nearshore zone.
• 82K tonnes org-C/year to GBR lagoon
• Alongi et al. 1998

7
or not.

• West Australian arid coast
• Virtually no freshwater input
• Tree nutrients are stored in living roots and
  leaves
• Vast bulk of nutrients is in the pool of dead
  fine-roots amounting to 35-90 of total living
  tree biomass .. biggest store for Ca, S, Cl, Na,
  Si, Fe, Mn, Zn, B, Mo, Cu
• N limitation suggested because NPP and total N
  are positively correlated.
• Overall, there is less N in the trees than in
  other forests.
• Alongi et al. 2003

8

• West Australian arid coast
• S-reduction accounted for 50-100 of total
  mineralization rates.
• No methanogenesis
• Oxic respiration is a minor decomposition
  pathway. gt50 of O2 is consumed in oxidation of
  reduced metabolites.
• N and P regeneration rates are low to
  immeasurable.
• Organic matter decomposition is very slow.
• Alongi et al. 2000

9

• Southern Thailand
• Net ammoniafication, nitrification and nitrogen
  fixation in surface sediments accounted for lt10
  of canopy N demand
• Away from rivers, N demand met from
  root-associated N fixation and/or mineralization
  throughout rooted soil mass.
• Large N inputs from upstream ag/industry, sewage
  and shrimp ponds 70-90 of the N supplied to the
  forest floor is shunted through ammonium pool to
  trees rapid growth.
• Alongi et al. 2002

10

• Belize Twin Cays
• No mineral soil 10 m of mangrove peat.
• 10 m core covered more than 8600 years
• Revealed climate change (either hurricanes or sea
  level fluctuation).
• Recognizable leaf and pollen fragments to the
  bottom of the core.
• Wooller et al. 2004

11

• Belize Twin Cays
• Seasonal variability wet and dry season
• Microbial mats are a key feature
• Salinity, organic C, Eh of porewater vary with
  season (wet and dry)
• Always - reduced metabolites accumulate at depth.
  
• C-mineralization coupled to sulfate reduction
  but both nitrous oxides and methane are also
  present.
• Lee et al. 2008

12
(No Transcript)
13
(No Transcript)
14
Mangrove adaptations reflect their extreme
environment.
15
Mangroves are influenced by all the organisms
that live in them.
16
Man o War Cay roosting site for Frigate Birds
and Brown Boobies
17
Microbial Mat Community at 3 sites on Twin Cays
Rosalynn Lee and Mandy Joye, Univ. of Georgia
18
A problem worthy of study
The dwarf zone is P-limited i.e.
P-fertilization leads to rapid and dramatic
increases in tree growth.
P-fertilized dwarf trees
Dwarf zone
19
Stimulation of branch elongation and leaf
production is visible within a few months of
P-fertilization.
Controls Short (4 mm) nodes no internodes
P- fertilized (9 mos) gt 10 cm internodes
Cheeseman and Lovelock, 2004
20
As leaf P increases, light saturated
photosynthesis also increases (in dwarf zone
leaves).
Fringe zone
Dwarf zone
Lovelock et al. 2006
21
Effect of P-fertilization on some water use
parameters in dwarf trees
No. Leaves Total leaf area (cm2) LA/stem area LA/stem circumference Stomatal conductance (mmol m-2s-1)
Control 25 785 1000 250 0.06
P-fertilized 165 4320 1180 630 0.14
Ratio gt6 gt5 1.2 2.5 2.5
At any time, a branch on a P-fertilized tree
would transpire gt12x more water than a control.
The P-response requires re-plumbing the
hydraulics.
22
Stable Isotopes, N-cycling, and responses to
P-fertilization
All aerial photos and isotope studies, courtesy
of Marilyn Fogel, Matt Wooller co, Carnegie
Institute of Washington
23
Applications of Stable Isotopes in Biology

• Pathway of Carbon Fixation
• Detect Biogenic Methane
• Nitrogen Fixation
• Paleoclimate- Rainfall, Mean Annual Temperature
• Detection of Sulfur Reduction and Oxidation
• Determination of Food Web Relationships
• Biogeochemical Cycles

24
C and N Isotopes in Food Webs reflect that fact
that ALL physical, chemical and biological
processes discriminate against the heavier
isotope.
More 13C
More 15N
25
d13C
Dwarf and fringe zone d15N differ. Dwarf zone
values are inordinately low.
d15N
Wooller and Fogel, 2001
26
Red mangrove d15Nleaf varies spatially throughout
the islands
d15N
Wooller, Smallwood, Jacobson and Fogel, 2001
27
The range in d15N in red mangrove leaves is
especially large?
d13C
28
N Isotopes are also heterogeneous in a single
plant and its soil.

d15N-17

d15N0
d15N-17
N2
d15N -15
d15N -10
d15N -4
d15N1 to -1
29
d15N
30
ISOTOPIC CHEMICAL EQUILIBRIUM

d15N-17

d15N0
N2
d15N-19
NH3
d15N 0
NH4
d15N1 to -1
31
This is the end of the presentation on the
P-fertilization problem what follows is some
information on isotope transfers in mangrove food
webs, and slides for the discussion of mangrove
restoration and shrimp farm damage mediation.
32
(No Transcript)
33
Mathematical Network Modeling the holy grail
TWIN CAYS FOOD WEB
U. Sharler, 2000
34
(No Transcript)
35
d13C
36
(No Transcript)
37
(No Transcript)
38
(No Transcript)
39
(No Transcript)
40
(No Transcript)