from the indian ocean to the caribbeanfrom the indian ocean to the caribbean: defining seagrass...

From the Indian Ocean to the Caribbean:

Definingseagrasshabitats

toassesssystem

processes

www.ian.umces.edu

Tim Carruthers

R.P

. van

Dam

G. K

endr

ick

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

Seagrasses evolved in a very different marine environment from today

Hydrocharitaceae

Cymodoceacea

Zosteraceae

Seagrasses evolved in a very different marine environment from today

Hydrocharitaceae

Cymodoceacea

Zosteraceae

Seagrasses evolved in a very different marine environment from today

Hydrocharitaceae

Cymodoceacea

Zosteraceae

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

Seagrasses are valuable and threatened compared to other major marine habitats

Research effort on seagrasses increasing, but lagging behind other coastal habitats.

Within widely accessed media, reports of seagrass are lacking

Bottom line: less seagrass research doneAND it isn’t broadly publicized

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

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)

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

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

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

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

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

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

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

Southwest estuarine seagrass habitats

Southwest estuarine seagrass habitats

Tannin rich

Dempster Estuary

Oyster Harbour

Ruppia megacarpa Agricultural inputs Dawesville cut

West coast seagrass habitats

West coast seagrass habitats

Shoalwater Bay Success Bank

Pocillopora and Posidonia Seagrass beach wrack Canal development Anchor scarring

South coast seagrass habitats

South coast seagrass habitats

Exposed beachGranite headland

Ascidian Seal Rock groyne Fish farm

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

A ecophysiological framework

Carruthers, Cambridge, Dennison, Kendrick and Walker

An ecophysiological framework

Carruthers, Cambridge, Dennison, Kendrick and Walker

Example two: Yucatan Mexico

• Low elevation, flat karstic limestone• Low rainfall (0.8-1.2m)• No surface runoff• Caves and underground rivers

Chicxulub crater, the KT boundary and the ‘ring of cenotes’

Sink hole

Submarine spring

Northern estuarine lagoon

Southern reef lagoon

Southern reef lagoon

Low rainfall estuarine and reef lagoons

Estuarine lagoon Back reef lagoon

Example three: Bocas del Toro Panama

•3m annual rainfall•Steep watershed, high erosion•Shallow seagrass depth range (3m)•Diverse habitat (coral/mangrove)

Watershed inputs

Timber production

Riverbank erosion Banana plantationsSlumping and hillslope erosion

Sewage inputs

First level classification, high vs. low rainfall

High rainfall Low rainfall

Within high rainfall sites:Sediment: carbonate vs. silicate

carbonate silicate

Sediment: carbonate vs. silicate

carbonate silicate

high % CaCO3low % CaCO3

% CaCO3

18 ± 3

90 ± 2

77 ± 8

Example of these habitats from Bocas del Toro (high rainfall)

Carbonate

Example of these habitats from Bocas del Toro (high rainfall)

Carbonate

Silicate

Second level classification, sediment type

Carbonate Silicate

High rainfall Low rainfall

‘Fluvial’

High rainfall, highly carbonate sediment:Sediment: high and low water content

high water content

low water content

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

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’

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

Variation in T. testudinum (in the Caribbean)

CARICOMP 8th ICRS 1 (1997) 647-650 (Caribbean Marine Coastal Productivity Program)

Thalassia habitat type is reflected in seagrass measures

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’

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

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

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

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