Paul Maxwell, AMSA 2013. Managing Seagrass Resilience: feedbacks and scales

Managing for seagrass

resilience: feedbacks and

scales

Paul Maxwell

Kate O’Brien, Angus Ferguson, James Udy, Gary Kendrick, Peter Scanes, Kieryn Kilminster, Michelle Waycott, Bill Dennison, Len

McKenzie, Matt Adams, Jimena Samper-Villarreal, Kathryn McMahon, Mitch Lyons, Vanessa Lucieer, Lynda Radke

AMSA Conference, 10th July 2013

Ecosystems are complex

Sudden shifts occur in many ecosystems




Coral Reefs (Hughes et al 2010, TREE)





Rangelands (Walker et al 1981, Ecology)

Coral Reefs (Hughes et al 2010, TREE)

Seagrass collapse – Dutch Wadden Sea

Source: de Jonge et al 1993

1920’s 1950’s 1972 1988

Biomass (gCm-2)

Area (km2)

Seagrass collapsed in 1930’s

200

0

100

50

150


Seagrass collapse – Multiple stressors, multiple scales



Wasting disease – Cellular scale (ultimate source of collapse)




Change in tidal regime over course of three centuries (de Jonge et al 1993)

“Afsluitdijk”





100

120

140

160

180

200

1860 1880 1900 1920 1940 1960 1980

Tid

al ra

ng

e (

cm

)“Afsluitdijk”





100

120

140

160

180

200

1860 1880 1900 1920 1940 1960 1980

Tid

al ra

ng

e (

cm

)

Coupled with decadal increases in sedimentation (de Jonge et al 1993)

“Afsluitdijk”

0

50

100

150

200

1965 1970 1975 1980 1985 1990

TS

S (

mg

/l)

Site 1

Site 2


No recovery


No recovery

No significant recovery despite:

• 120 million Euros spent in past 20 years

• Eelgrass recovered in much of the North Atlantic range


No recovery

No significant recovery despite:

• 120 million Euros spent in past 20 years

• Eelgrass recovered in much of the North Atlantic range

Why haven’t things improved?


Feedback processes control resistance and recovery


Alternate RegimeRegime 1


Seagrass

response

Impact below threshold



Seagrass

response

Feedback

Processes




Seagrass

response

Feedback

Processes




Seagrass

response

Threshold

Feedback

Processes

Impact above thresholdImpact below threshold



Seagrass

response

Threshold

Feedback

ProcessesFeedback

Processes




Seagrass

response

Threshold

Feedback

ProcessesFeedback

Processes




Trajectories between states are complicated

Seagrass present

Seagrass absent

Loss

trajectory

Stressor increasingAMSA Conference, 10th July 2013


Seagrass present

Seagrass absent

Loss

trajectory

Stressor increasingAMSA Conference, 10th July 2013


Seagrass present

Seagrass absent

Loss

trajectory

Stressor increasing

Changed

hydrologyIncreased

sedimentation

Wasting

disease



Seagrass present

Seagrass absent

Loss

trajectory

Recovery

trajectory

Stressor increasing

Changed

hydrologyIncreased

sedimentation

Wasting

disease



Seagrass present

Seagrass absent

Loss

trajectory

Recovery

trajectory

Stressor increasing

Changed

hydrologyIncreased

sedimentation

Wasting

disease

Sediment resuspension

Change current speed


Stressors, pressures and feedbacks affecting light

Stressors and pressures Seagrass responses(McMahon et al 2013)

Feedback processes(strategies for resistance and recovery)



Cloud shading

Sediment

resuspension

Water clarity

Water depth

Self-shading

Sediment

runoff

Climatic

fluctuations

Planetary and

solar

fluctuations

Stressors and pressures

Local

disturbance

(boat anchors)

Dredging

Point source

nutrients

Algal blooms

Floods

Trawling

Catchment

clearing

Atmospheric

light

attenuation

(e.g. smog)

Seagrass responses(McMahon et al 2013)




Cloud shading

Sediment

resuspension

Water clarity

Water depth

Self-shading

Sediment

runoff

Climatic

fluctuations

Planetary and

solar

fluctuations


Local

disturbance

(boat anchors)

Dredging

Point source

nutrients

Algal blooms

Floods

Trawling

Catchment

clearing

Atmospheric

light

attenuation

(e.g. smog)


ETRmax

Shoot C:N

Rhizome

carbohydrates

Shoot

production

Root

extension

Shoot density

Chlorophyll

contentLeaf extension

Leaf area

Above ground

biomass Below ground

biomass

Percent cover

Meadow area


Regional

seagrass

extent



Cloud shading

Sediment

resuspension

Water clarity

Water depth

Self-shading

Sediment

runoff

Climatic

fluctuations

Planetary and

solar

fluctuations


Local

disturbance

(boat anchors)

Dredging

Point source

nutrients

Algal blooms

Floods

Trawling

Catchment

clearing

Atmospheric

light

attenuation

(e.g. smog)


ETRmax

Shoot C:N

Rhizome

carbohydrates

Shoot

production

Root

extension

Shoot density

Chlorophyll


Leaf area

Above ground


biomass

Percent cover

Meadow area


Algal grazing

rates

Regional

seagrass

extent

Seagrass

grazing rates

Genetic

variability

Trapping of

sediments

Nutrient

filtration

Reduced

water velocity

Sediment

stabilisation

Seagrass

succession

Flowering

intensity


Outcome 1: Scale provides order

ETRmax

Shoot C:N

Rhizome

carbohydrates

Shoot

production

Root

extension

Shoot density

Chlorophyll


Leaf area

Above ground


biomass

Percent cover

Flowering

intensity

Meadow area

Regional

seagrass

extent

se

co

nd

10000

km

1 mm

10 m

10 cm

1km


100 km

min

ute

hour

day

mo

nth

we

ek

ye

ar

ce

ntu

ry

mill

en

niu

m



ETRmax

Shoot C:N

Rhizome

carbohydrates

Shoot

production

Root

extension

Shoot density

Chlorophyll


Leaf area

Above ground

biomass

Below ground

biomass

Percent cover

Flowering

intensity

Meadow area

Regional

seagrass

extent

se

co

nd

10000

km

1 mm

10 m

10 cm

1km


100 km

min

ute

hour

day

mo

nth

we

ek

ye

ar

ce

ntu

ry

mill

en

niu

m



ETRmax

Shoot C:N

Rhizome

carbohydrates

Shoot

production

Root

extensionShoot density

Chlorophyll

content

Leaf extension

Leaf area

Above ground

biomass

Below ground

biomass

Percent cover

Flowering

intensity

Meadow area

Regional

seagrass

extent

se

co

nd

10000

km

1 mm

10 m

10 cm

1km


100 km

min

ute

hour

day

mo

nth

we

ek

ye

ar

ce

ntu

ry

mill

en

niu

m



ETRmax

Shoot C:N

Rhizome

carbohydrates

Shoot

production

Root


Chlorophyll

content

Leaf extension

Leaf area

Above ground

biomass

Below ground

biomass

Percent cover

Flowering

intensity

Meadow area

Regional

seagrass

extent

se

co

nd

10000

km

1 mm

10 m

10 cm

1km


100 km

min

ute

hour

day

mo

nth

we

ek

ye

ar

ce

ntu

ry

mill

en

niu

m

Physiological

scale



ETRmax

Shoot C:N

Rhizome

carbohydrates

Shoot

production

Root


Chlorophyll

content

Leaf extension

Leaf area

Above ground

biomass

Below ground

biomass

Percent cover

Flowering

intensity

Meadow area

Regional

seagrass

extent

se

co

nd

10000

km

1 mm

10 m

10 cm

1km


100 km

min

ute

hour

day

mo

nth

we

ek

ye

ar

ce

ntu

ry

mill

en

niu

m

Physiological

scale

Morphological

scale



ETRmax

Shoot C:N

Rhizome

carbohydrates

Shoot

production

Root


Chlorophyll

content

Leaf extension

Leaf area

Above ground

biomass

Below ground

biomass

Percent cover

Flowering

intensity

Meadow area

Regional

seagrass

extent

se

co

nd

10000

km

1 mm

10 m

10 cm

1km


100 km

min

ute

hour

day

mo

nth

we

ek

ye

ar

ce

ntu

ry

mill

en

niu

m

Physiological

scale

Morphological

scale

Landscape

scale


se

co

nd

10000

km

1 mm

10 m

10 cm

1km

100 km

min

ute

hour

day

mo

nth

we

ek

ye

ar

ce

ntu

ryPhysiological

scale

Morphological

scale

Landscape

scale

mill

en

niu

m

First outcome:

Managing and monitoring seagrass

ecosystems, need to understand

scale of stressor and response



Outcome 2: Species specific modes of resistance and recovery

Speed of recovery(event recurrence time/species recovery time)

Re

sis

tan

ce to d

istu

rba

nce

( su

rviv

al tim

e/e

ve

nt d

ura

tio

n)



OPPORTUNISTIC SPECIESPERSISTENT SPECIES

EPHEMERAL SPECIESNO SEAGRASS


Re

sis

tan

ce to d

istu

rba

nce

( su

rviv

al tim

e/e

ve

nt d

ura

tio

n)






Re

sis

tan

ce to d

istu

rba

nce

( su

rviv

al tim

e/e

ve

nt d

ura

tio

n)

P. australis (east)

Enhalus acoroides

P. sinuosa

Thalassia spp.






Re

sis

tan

ce to d

istu

rba

nce

( su

rviv

al tim

e/e

ve

nt d

ura

tio

n)

P. australis (east)

Enhalus acoroides

P. sinuosa

Thalassia spp.

Syringodium spp.

H. spinuosa

Halodule spp.

Ruppia spp.

H. ovalis

H. decipiens






Re

sis

tan

ce to d

istu

rba

nce

( su

rviv

al tim

e/e

ve

nt d

ura

tio

n)

P. australis (east)

Enhalus acoroides

P. sinuosa Thalassodendron spp.

Thalassia spp.

P. corriacea

P. australis (west)

Cymodocea spp.

Zostera spp.

Amphibolis spp.

Syringodium spp.

H. spinuosa

Halodule spp.

Ruppia spp.

H. ovalis

H. decipiens






Re

sis

tan

ce to d

istu

rba

nce

( su

rviv

al tim

e/e

ve

nt d

ura

tio

n)

P. australis (east)

Enhalus acoroides

P. sinuosa Thalassodendron spp.

Thalassia spp.

P. corriacea

P. australis (west)

Cymodocea spp.

Zostera spp.

Amphibolis spp.

Syringodium spp.

H. spinuosa

Halodule spp.

Ruppia spp.

H. ovalis

H. decipiens


Outcome 3: Thresholds of feedback processes

Time

Seagra

ss r

esponse

DISTURBANCE(S

ho

ot d

en

sity,

bio

ma

ss)



Time

Seagra

ss r

esponse

DISTURBANCE(S

ho

ot d

en

sity,

bio

ma

ss)



Time

Seagra

ss r

esponse

DISTURBANCE

Threshold for

feedback efficiency

(Sh

oo

t d

en

sity,

bio

ma

ss)



Time

Seagra

ss r

esponse

DISTURBANCE

Recovery from

disturbance

Threshold for

feedback efficiency

(Sh

oo

t d

en

sity,

bio

ma

ss)


Time

DISTURBANCE

Poorer

conditions

Better

conditionsSeagra

ss r

esponse

(Sh

oo

t d

en

sity,

bio

ma

ss)



Time

DISTURBANCE

Seagra

ss r

esponse

(Sh

oo

t d

en

sity,

bio

ma

ss)

- sedimentation

- tidal regime

(wasting disease)

Poorer

conditions

Better

conditions



Time

DISTURBANCE

Seagra

ss r

esponse

(Sh

oo

t d

en

sity,

bio

ma

ss)

- sedimentation

- tidal regime

(wasting disease)

Poorer

conditions

Better

conditions



Time

DISTURBANCE

Change of state

possible

Seagra

ss r

esponse

(Sh

oo

t d

en

sity,

bio

ma

ss)

- sedimentation

- tidal regime

(wasting disease)

Poorer

conditions

Better

conditions



Time

DISTURBANCE

Change of state

possible

Manage to keep seagrass units at each scale above threshold

Seagra

ss r

esponse

(Sh

oo

t d

en

sity,

bio

ma

ss)

- sedimentation

- tidal regime

(wasting disease)

Poorer

conditions

Better

conditions


Implications for management

Physiological

scale

Morphological

scale

Landscape

scale

MANAGEMENT PRIORITIES

MONITORING STRATEGIESAMSA Conference, 10th July 2013


Physiological

scale

Morphological

scale

Landscape

scale

Facilitate seagrass

recovery


MONITORING STRATEGIES

- reduce plant stress

- maximise seed dispersal

- improve conditions to

maximise photo efficiency



Physiological

scale

Morphological

scale

Landscape

scale

Facilitate seagrass

recovery







Investigatory

monitoring

- physiological indicators of stress

- reproductive output

- physiological feedback processes


Physiological

scale

Morphological

scale

Landscape

scale

Facilitate seagrass

recovery







Investigatory

monitoring




Manage environmental

conditions

- regional management of

water quality

- catchment management

- reduce sedimentation

- reduce nutrient loading


Physiological

scale

Morphological

scale

Landscape

scale

Facilitate seagrass

recovery







Investigatory

monitoring





conditions


water quality




Seasonal or annual

monitoring

- mapping meadow change

- patch dynamics

- species distribution

- seagrass biomass

- morphological feedback

processes


Physiological

scale

Morphological

scale

Landscape

scale

Facilitate seagrass

recovery







Investigatory

monitoring





conditions


water quality




Seasonal or annual

monitoring


- patch dynamics


- seagrass biomass


processes

Manage ecosystem

integrity

- habitat protection (MPA’s)

- habitat and species

connectivity


Physiological

scale

Morphological

scale

Landscape

scale

Facilitate seagrass

recovery







Investigatory

monitoring





conditions


water quality




Seasonal or annual

monitoring


- patch dynamics


- seagrass biomass


processes

Manage ecosystem

integrity

- habitat protection (MPA’s)

- habitat and species

connectivity

Periodic monitoring

- broad scale and long term

assessments

- remote sensing

- ecosystem models

- landscape feedback

processes

Thank you


Technology

Paul Maxwell, AMSA 2013. Managing Seagrass Resilience: feedbacks and scales