MOVING ON UP:
THE ROLE OF BLACK MANGROVES IN INTRODUCING AND MEDIATING
BASAL CARBON SOURCES IN ESTUARINE FOOD WEBS
Melissa M. Baustian1 Christina Powell2, Brandeus Davis2, Mike Polito3
1The
Water Institute of the Gulf, Baton Rouge, LA
of Oceanography and Coastal Sciences, Louisiana State University
3School of the Coast and Environment, Louisiana State University
2Department
GERS 2016 meeting
BLACK MANGROVES
EXPANDING INTO LOUISIANA’S
SALT MARSHES
a)
Temperature increases
Spread of black
mangroves are projected
to increase from
-Climate change:
• winter warming
• drought conditions
Figures modified from Osland et al.
(2013).
b)
Potential
salt marsh
conversion
BLACK MANGROVES PLANTING AS
A COASTAL RESTORATION TOOL
A method of trapping
sediments to reduce
coastal erosion
Example:
ConocoPhillips &
Tierra Resources
Planting of black
mangroves
saplings. Image ©
ConocoPhillips
and Tierra
Resources.
http://tierraresourcesll
c.com/coastalprotectionprojects/mangroveplantings-pilotproject/
BESIDES ALTERING HABITAT
STRUCTURE…
• Mangroves will introduce a
novel basal carbon source
• Consumers will be exposed
to a new carbon source
besides the typical estuarine
carbon sources of:
– Salt marsh grass detritus
– Phytoplankton
– Microphytobenthos
Boesch & Turner 1984, Peterson &
Howarth 1987, Deegan & Garritt 1997,
Galván et al. 2008
4
RESEARCH QUESTIONS
• Q1: Does the abundance and biomass of basal
carbon sources and consumers, including important
juvenile nekton, differ in marsh and mangrove
habitats?
• Q2: Will climate driven expansion of black
mangroves into salt marshes lead to shifts in
the basal carbon sources supporting important
juvenile marsh species?
HYPOTHESIS
Carbon from mangroves will increase the diversity of basal carbon
sources used by consumers and allow novel trophic interactions and
higher diversity in mixed systems.
ALTERNATIVE HYPOTHESIS
New basal carbon source leads to a dominance of refractory carbon,
which is less likely to be assimilated into the food web
– other basal carbon sources such as microphytobenthos or
phytoplankton may be of importance
7
METHODS: STUDY SITES
• Two sites:
• Grand Isle, LA
• Bay Champagne, near Port
Fourchon, LA
• Three habitat blocks per site
• Mangrove
• Salt marsh
• Mixed
• Sampling schedule:
• May 2016 (GI and BC)
• August 2016 (BC)
• October 2016 (BC)
• February 2017 (BC)
Grand Isle (GI)
Bay Champagne (BC)
Gulf of Mexico
METHODS: SAMPLING
• Sampling whole food web with a
focus on juvenile nekton
• Replicate suction sampling and
modified fyke nets along
marsh/mangrove edges
• Quadrat sampling at low tide for
vegetation and benthos
METHODS: DATA ANALYSIS
• Compare abundance, biomass &
community composition of nekton
across habitat types
• Bulk & compound specific stable
isotope analysis
• Identify food web structure
• Track carbon sources fueling the
food webs of valuable nekton
species
Caudill 2005
BASAL CARBON SOURCES
A. Salt marsh grass
B. Mangrove trees
C. Phytoplankton
D. Microphytobenthos
E. Epiphytic algae
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PRELIMINARY RESULTS
Grass Shrimp and Periwinkle Snails
12
CONCLUSIONS FROM OTHER
MANGROVE STUDIES
• Mangrove carbon contributed little to the mangrove and mudflat
food webs in Tanzania (Kruitwagen et al. 2010)
• Microphytobenthos and plankton largely sustained fishes in the
region while mangroves, where present were of minor importance
in Persian Gulf (Shahraki et al. 2014)
• Food web structure was clarified when literature isotopic values of
microphytobenthos and coralline algae were added, suggesting
their importance in Panama food webs (Viana et al. 2015)
• High fisheries productivity of mangroves globally appears to be
energetically supported largely by food sources from adjacent
habitats (Igulu et al. 2013)
13
NEXT STEPS
• Final sampling in winter/early
spring 2017
• Analyze the composition,
biomass and isotopic signatures
of the basal carbon sources and
juvenile consumers
• C. Powell will resent results at
CERF 2017, Providence, RI
• Characterizing these major basal
carbon sources are needed to
fully understand food web
dynamics in estuarine
ecosystems, especially those
undergoing transition.
14
ACKNOWLEDGEMENTS
• Funding:
– Louisiana Sea Grant
• Field Assistance:
– Leland Moss, Mario Hernandez, Jessica
Johnson, Collin Ortals, Kelly Darnell, Zack
Darnell, Whitney Scheffel, Gary Peterson,
Tyler Mauney
• Laboratory Assistance:
– Shannon Matzke, Phoebe Hemmerling,
Andrea Jerabek, Tyler Mauney
• Land Owners:
–
–
–
–
Wisner Family Foundation
LLE/Conoco Phillips
Grand Isle Independent Levee District
The Nature Conservancy
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THANK YOU
Melissa M. Baustian
[email protected]
@TheH2OInstitute
301 NORTH MAIN STREET, SUITE 2000
BATON ROUGE, LA 70825
(225) 448-2813
WWW.THEWATERINSTITUTE.ORG