Transcript Massive Porites sp. corals as indicators of historical

Massive Porites sp. corals as indicators of
historical changes in river runoff:
A case study for Antongil Bay
(Masoala National Park, NE Madagascar)
J. Zinke1, C. Grove2, G. J. Brummer2
1Vrije
Universiteit Amsterdam, The Netherlands
2Royal
NIOZ, The Netherlands
in cooperation with WCS Madagascar
Ecological Response of Reefs: global &
local impacts
GLOBAL
Climate Change
• Global Warming (coral
bleaching)
• Increased pCO2 (ocean
acidification)
• Sea Level Rise
LOCAL IMPACTS
• CORAL PREDATORS – Crown of Thorns (COTS)
• FISHING/TRAWLING – Reef ecology
• RIVER RUNOFF - Sediments, Nutrients, Freshwater input
HERBIVORES
Fish, Invertebrates
CORALS
Adults
Juveniles
ALGAE
CROWN OF
THORNS
competition
Algal Reef
for space
reproduction
Healthy Reef
Study area: NE Madagascar, Antongil Bay, St. Marie, Ifaty
• Main climatic variables in the region: Rainfall and SST
Rainfall (cyclonic) impacts on:
1) Freshwater runoff and sedimentation of river systems
2) Ocean chemistry and physical conditions
3) Nutrient and pollutant export rates
Sea surface temperature patterns affect rainfall variability
• Climate change impacts on reefal ecosystem:
1) Multiple stress factors: SST, salinity, sediments, pollutants,
nutrients
• Impact on livelihoods:
1) large-scale flooding of villages
2) Erosion of agricultural land, loss of fertile soil
3) Sewage export impacts on fisheries
Objectives Madagascar
Recontruction of surface ocean chemistry, temperature and
salinity related to global and local factors:
To provide baseline of natural variability against which
anthropogenic impacts can be assessed
Learn about spatial and temporal changes in climate
Study sedimentation, pollutant and nutrient export and how
it relates to climate variability
Quantify the impacts of climatic and environmental changes
on coastal ecosystems
Our monitoring tool:
Massive corals Porites sp.
Life span: up to 400 years
Geochemical proxies in corals:
-Sr/Ca for SST
-Oxygen isotopes for salinity
-Combination Sr/Ca and d18O for hydrology
- Ba/Ca, Y, Mn for river runoff
-Cu, Zn etc. for biological activity
- Luminescence for runoff
- Density and Calcification for status of coral health
Zinke et al., 2004
y and Reunion corals record link to Pacific Decadal Oscillation (18-25 ye
Ba/Ca as a proxy for sediment river discharge
Ba is highly abundant
in river sediment load
Ba is released when river
water flows into seawater
(salinity, pH gradient)
Freshwater plumes into
the coastal ocean are
correlated with higher
Ba/Ca ratios in corals
Floods after drought years
contain more Ba than in
normal years
McCulloch et al., 2003, Nature 421
Increase in temperature and sedimentation over 20th century:
Antongil Bay
Seasonal timing of runoff
Ba/Ca: late summer/winter max
Mn: summer max
Luminescence banding
related to river runoff:
Quantification of runoff
intensity in single years
XRF-scanning luminesecence (Royal NIOZ Netherlands): subweekly resolut
Calcification rate and density decrease over the 20th century:
Ocean Acidification?
MAS1 coral, Masoala Park
Gaps in monitoring and research:
• monitoring natural variability of sedimentation, nutrient
and pollutant export to provide natural levels
• combine environmental monitoring with ecosystem
studies (reef monitoring)
• monitor SST and salinity to evaluate choice of MPA’s
• climatological monitoring land and ocean (isotopes in
precipitation, isotopes in groundwater/seawater)
• combine terrestrial (tree rings, stalagmites, lakes) and
marine studies (corals, bivalves) to investigate land-ocean
interaction (gradients)
• hydrological modelling of climate and land-use impacts