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From the Indian Ocean to the Caribbean:
Definingseagrasshabitats
toassesssystem
processes
www.ian.umces.edu
Tim Carruthers
R.P
. van
Dam
G. K
endr
ick
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Outline• A curious history – of an ugly duckling
• Developing a process based comparative framework for seagrasses
• Example 1: Indian Ocean - SW Australia
• Example 2: Caribbean – Yucatan
• Example 3: Caribbean – Panama
• Current Applications
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Seagrasses evolved in a very different marine environment from today
Hydrocharitaceae
Cymodoceacea
Zosteraceae
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Seagrasses evolved in a very different marine environment from today
Hydrocharitaceae
Cymodoceacea
Zosteraceae
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Seagrasses evolved in a very different marine environment from today
Hydrocharitaceae
Cymodoceacea
Zosteraceae
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Seagrasses are abundant in tropical and temperate regions
Halophila: Bocas del Toro, Panama
Thalassia: Kuna Yala, Panama
Ruppia: Morro Bay, USA
Zostera: Ria Formosa, Portugal
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Seagrasses are valuable and threatened compared to other major marine habitats
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Research effort on seagrasses increasing, but lagging behind other coastal habitats.
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Within widely accessed media, reports of seagrass are lacking
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Bottom line: less seagrass research doneAND it isn’t broadly publicized
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Some possible reasons….• Seagrasses are largely invisible
(shallow, subtidal)• Fauna in seagrass are often small and cryptic
(unlike coral reefs)• Charismatic megafauna are increasingly rare
and elusive (Dugongs, Manatees, Turtles)• BUT ALSO…
it may be helpful to define seagrass habitats to reflect seagrass form, processes and functions
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Framework one: Genera based• Benefits:
Large step forward from ‘seagrass’or ‘SAV’Good for documenting, referencing
• Limitations:Difficult to draw process based generalitiesBetween species differences can be vast(Zostera leaves can vary from <5cm to 3+m between sp)
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Framework two: Geographic based• Benefits:
Good for documenting and referencingReflects reality of researchReflects interest of funding bodies
• Limitations:Difficult to draw process based generalitiesSeagrass ≠ seagrass !Different lineages between species
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Framework three: Process based• Initial assessments using three examples of a
process based approach to synthesizing seagrasshabitats
• Example 1: Indian Ocean - SW Australia
• Example 2: Caribbean – Yucatan
• Example 3: Caribbean – Panama
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Example one: Southwest Australia
• 18 (of 60) species• 1240 km of seagrass
(Cambridge MD toJacksonville FL)
• Quite Possible the largest area of continuous seagrassin the world
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SW Australia in context of other systems
• Key features of south west Australia and seagrass response• High water motion results in robust seagrass
• SW west coast 1.5(-7)• SW south coast 2.2(-10)• SW estuaries <0.5• NE Australia <2.0• Florida bay <0.5• Caribbean <1.0• Chesapeake <1.5
Waveheight Tide
Maxdepthlimit
PorewaterNH4
+Nutrient
limitation
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SW Australia in context of other systems
• Key features of south west Australia and seagrass response• High water motion results in robust seagrass• Small tides results in subtidal seagrass
• SW west coast 1.5(-7) 0.8-1.0• SW south coast 2.2(-10) 0.8-1.0• SW estuaries <0.5 <0.1• NE Australia <2.0 4-6• Florida bay <0.5 0.2-0.6• Caribbean <1.0 <1.0• Chesapeake <1.5 1.0
Waveheight Tide
Maxdepthlimit
PorewaterNH4
+Nutrient
limitation
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SW Australia in context of other systems
• Key features of south west Australia and seagrass response• High water motion results in robust seagrass• Small tides results in subtidal seagrass• Clear water results in extensive depth range
• SW west coast 1.5(-7) 0.8-1.0 44• SW south coast 2.2(-10) 0.8-1.0 48• SW estuaries <0.5 <0.1 3• NE Australia <2.0 4-6 58• Florida bay <0.5 0.2-0.6 27• Caribbean <1.0 <1.0 40• Chesapeake <1.5 1.0 3
Waveheight Tide
Maxdepthlimit
PorewaterNH4
+Nutrient
limitation
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SW Australia in context of other systems
• Key features of south west Australia and seagrass response• High water motion results in robust seagrass• Small tides results in subtidal seagrass• Clear water results in extensive depth range • Low nutrients results in efficient recycling
• SW west coast 1.5(-7) 0.8-1.0 44 12 not limited• SW south coast 2.2(-10) 0.8-1.0 48 5 balanced NP• SW estuaries <0.5 <0.1 3 13 not limited• NE Australia <2.0 4-6 58 22 N limited• Florida bay <0.5 0.2-0.6 27 79 P inshore N offshore• Caribbean <1.0 <1.0 40 20 P limited• Chesapeake <1.5 1.0 3 200 not limited
Waveheight Tide
Maxdepthlimit
PorewaterNH4
+Nutrient
limitation
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Southwest estuarine seagrass habitats
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Southwest estuarine seagrass habitats
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Tannin rich
Dempster Estuary
Oyster Harbour
Ruppia megacarpa Agricultural inputs Dawesville cut
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West coast seagrass habitats
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West coast seagrass habitats
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Shoalwater Bay Success Bank
Pocillopora and Posidonia Seagrass beach wrack Canal development Anchor scarring
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South coast seagrass habitats
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South coast seagrass habitats
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Exposed beachGranite headland
Ascidian Seal Rock groyne Fish farm
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sheltered meadows exposed meadows
Features:Dense meadows increase carbon limitation
tight nutrient recycling (36% N)
Low genetic variability
Abundant infauna
Features:Posidonia coriaceae thick vertical rhizomes
Over decades – 50% of area will switch between seagrass and bare sand
Nutrients pumped from sediments
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A ecophysiological framework
Carruthers, Cambridge, Dennison, Kendrick and Walker
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An ecophysiological framework
Carruthers, Cambridge, Dennison, Kendrick and Walker
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Example two: Yucatan Mexico
• Low elevation, flat karstic limestone• Low rainfall (0.8-1.2m)• No surface runoff• Caves and underground rivers
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Chicxulub crater, the KT boundary and the ‘ring of cenotes’
Sink hole
Submarine spring
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Northern estuarine lagoon
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Southern reef lagoon
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Southern reef lagoon
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Low rainfall estuarine and reef lagoons
Estuarine lagoon Back reef lagoon
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Example three: Bocas del Toro Panama
•3m annual rainfall•Steep watershed, high erosion•Shallow seagrass depth range (3m)•Diverse habitat (coral/mangrove)
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Watershed inputs
Timber production
Riverbank erosion Banana plantationsSlumping and hillslope erosion
Sewage inputs
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First level classification, high vs. low rainfall
High rainfall Low rainfall
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Within high rainfall sites:Sediment: carbonate vs. silicate
carbonate silicate
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Sediment: carbonate vs. silicate
carbonate silicate
high % CaCO3low % CaCO3
% CaCO3
18 ± 3
90 ± 2
77 ± 8
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Example of these habitats from Bocas del Toro (high rainfall)
Carbonate
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Example of these habitats from Bocas del Toro (high rainfall)
Carbonate
Silicate
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Second level classification, sediment type
Carbonate Silicate
High rainfall Low rainfall
‘Fluvial’
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High rainfall, highly carbonate sediment:Sediment: high and low water content
high water content
low water content
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Sediment: high and low water content
high water content
low water content
high water content
low water content
water content
21 ± 2
24 ± 1
58 ± 7
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A potential habitat classification for Thalassia meadows in the Caribbean…
Carbonate Silicate
Low water content High water content
High rainfall Low rainfall
‘Fluvial’
‘Coral’ ‘Mangrove’
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Thalassia testudinum– Caribbean, Gulf of Mexico, to Bermuda
T. hemprichii T. testudinum
Waycott and Barnes, Mar Biol (2001) 139:1021-1028
• Vegetative dispersal over 2700 km• Potential gene flow over entire area
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Variation in T. testudinum (in the Caribbean)
CARICOMP 8th ICRS 1 (1997) 647-650 (Caribbean Marine Coastal Productivity Program)
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Thalassia habitat type is reflected in seagrass measures
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Habitat classification for Thalassiameadows fits variation in tissue nutrients
Carbonate Silicate
Low water content High water content
High rainfall Low rainfall
‘Coral’ ‘Mangrove’
%N 2.6 ± 0.1
%P 0.27 ± 0.02
%N 2.5 ± 0.1
%P 0.26 ± 0.01
‘Fluvial’
%N 2.5 ± 0.1
%P 0.26 ± 0.01%N 2.3 ± 0.1
%P 0.22 ± 0.01
Global medians (Duarte, 1990)
%N 1.8 %P 0.2
%N 1.8 ± 0.14
%P 0.13 ± 0.01
‘Lagoonal’
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Current applications: SAVtrends
• Assessing long term patterns and processes in SAV abundance in Chesapeake Bay
• HPL (Mike K, Court S, Evamaria K), VIMS, MDDNR, CBP, IAN
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Current applications: NCEAS• Global trajectories of seagrasses: Establishing a quantitative basis for
seagrass conservation and restoration • Development of extensive global database of seagrass gains/losses• International team
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Conclusions• Seagrass has a curious history but is the
‘ugly duckling’ of coastal habitats
• Developing a more process based comparative framework for seagrasses may help this dilemma
• SW Australia: provides a framework for environmental relationships to seagrass with global application
• Yucatan: feeds into understanding of point sources
• Bocas del Toro: provides an initial habitat framework which shows promise for expanding to a Caribbean wide synthesis of Thalassia testudinum
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Sources and Acknowledgments–Robert J. Orth, Tim J.B. Carruthers, William C. Dennison, Carlos M. Duarte, James W. Fourqurean, Kenneth L. Heck, Jr., A. Randall Hughes, Gary A. Kendrick, W. Judson Kenworthy, Suzanne Olyarnik, Fred T. Short, Michelle Waycott, Susan L. WilliamsA Contemporary Crisis for Seagrass Ecosystems. Bioscience (in press)
–Carruthers, T.J.B., Cambridge, M.L., Kendrick, G.A., Dennison, W.C., Walker, D.I.A conceptual framework for the diverse and extensive seagrasses of southwest Australia. Journal of Experimental and Marine Biology and Ecology (in prep)
–Carruthers, T.J.B., Barnes, P.A.G., Jacome, G.E. and Fourqurean, J.W. 2005.Lagoon scale processes in a coastally influenced Caribbean system: implications for the seagrass Thalassia testudinum. Caribbean Journal of Science 41(3), 441-455.
–Carruthers, T.J.B., van Tussenbroek, B.I. and Dennison, W.C. 2005. Influence of submarine springs and wastewater on nutrient dynamics of Caribbean seagrass meadows. Estuarine Coastal and Shelf Science 64, 191-199.
Oct 2006
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