Saltmarsh ecosystem services under multiple stress

Carl Van Colen

Joanne Wong, Steven Degraer, Laura Airoldi, Magda Vincx

Context-dependent effects of sediment deposition

& increased inundation

Email from Ewoud Monballiu • who am I? • who is involved? • which challenge(s) faced us? (stressors) • what was our assumption in order to tackle this challenge(s)? (research hypotheses) • what happened: interventions, processes, applications, discoveries, (un)expected barriers, pivotal moments or breakthrough moments? (results) • where we are now & what principles of working can be gleaned from this?

• my proposition is …

Outline

Coastal habitats and ecosystems are affected by multiple stressors

Who am I (and what do I study)?

Coastal benthic habitats are affected by multiple stressors •Broad scale phenomena

Mora et al. 2013 PloS Biology. Predicted changes by 2100 due to greenhouse gas emissions

•Local disturbances and environmental change

Multiple stressors interact and result in changes in the intrinsic dynamics of ecosystems that may predispose the system to critical shifts Disentangling local vs. broad-scale drivers of change & potential interaction effects

Methods

Study context-dependency in ecological interactions that determine BDEF relationships & support resilience

•Spatial and temporal context-dependency •Evolutionary adaptation

Coastal habitats: estuaries, coastal lagoons, salt marshes, continental shelf seas

Benthic communities: microbial communities benthic invertebrates (macrobenthos) nekton

Ultimate research goal... Moving from hindsight to a more predictive science that is able to assist in the implementation of ecosystem-based management

Who am I (and what do I study)?

Macrobenthos as a bio-indicator of environmental change

Well suited for long-term comparative investigations since many of the constituent species are

sessile or have low mobility relatively long-lived integrate effects of environmental change over time

Macrobenthos-mediated ecosystem services Production services: food provisioning (direct, e.g. shell

fish; indirect: provision of food/nutrients to higher trophic groups); raw materials (e.g. shells) Regulating services (removal of pollutants) Supporting services (nutrient cycling, biologically-mediated habitat)

Saltmarsh vegetation provide habitat & ecosystem services

provide erosion control, sediment accretion and carbon sequestration

Who is involved?

M. Alsebai Long-term variability and regime shifts in

benthic communities

S.Mestdagh Estuarine benthic-pelagic coupling

V. Lo Salt marsh biodiversity

and functioning: human pressures & Recovery pathways

J. Wong Management options

of cumulative stressors in salt

marshes

E. Ong Stressors & benthos

behavior

X. Fang Estuarine benthic

ecosystem functioning: Biogeochemical

modelling

Case study 1: Sediment-benthos relationships in the Zwin

coastal lagoon

2003: 95 samples + seasonal survey 12 stations (Tricolor study)

158 ha - Ramsar list - Natura 2000 – Dunes, salt marsh and creeks, tidal flats, salt pans, tidal pond. To be enlarged in the future (+120 ha).

Case study 1: Sediment-benthos relationships in the Zwin

coastal lagoon

2010: 60 samples (BEMONA and ZTAR project)

Case study 1: Sediment-benthos relationships in the Zwin

coastal lagoon

2013: 60 samples (ZTAR project)

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M. balthica

• Habitat preference: identification of critical thresholds modelling occurrence and biomass of benthos as a function of sediment

Van Colen C. et al. (2014) Sediment-benthos relationships as a tool to assist in conservation practices in a coastal lagoon subjected to sediment change. Biodiversity and conservation

- Highest probability of occurrence < 200 µm

- Biomass optima for Hediste and Scrobicularia < 150 µm

- Biomass optimum for Macoma @ 300 µm probability of occurrence < 200 µm

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SPATIO-TEMPORAL DYNAMICS IN BENTHIC COMMUNITIES AND SEDIMENT PROPERTIES 2003 – 2010

IN TWO CONTRASTING HABITATS

Van Colen C. et al. (2014) Sediment-benthos relationships as a tool to assist in conservation practices in a coastal lagoon subjected to sediment change. Biodiversity and conservation

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Temporal variability in sediment composition, (a) median grain size, (b) mud content, (c) organic matter content; and (d) biomass of macrobenthos in the inlet channel and intertidal habitat surrounding the tidal pond. The top of the stacked bar represents the total biomass and the biomass of the four most dominant species in terms of biomass are depicted in different colors (see inset). Error bars are 95 % confidence intervals (note that mud content = 0 in 2010)

Context-dependent

sedimentological change (spatial segregation)

- Coarsening of the inlet

channel - Finer sediment in the high

intertidal Benthos response to

sediment change

- Gradual infilling of the floodplain

Increased access for

ground predators Overall decrease in

sediment organic matter, macrobenthos biomass & thus food supply for shorebirds and nekton foraging in the intertidal creeks

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TEMPORAL DYNAMICS IN SHOREBIRD ABUNDANCES IN THE ZWIN COASTAL LAGOON

2003 - 2010

Temporal change in average winter (November-February) abundances of Calidris alpina (Dunlin), Pluvialis squatarola (Grey Plover), Recurvirostra avosetta (Avocet), and Tadorna tadorna (Shelduck) in the Zwin nature reserve between 2003 and 2011. Solid lines represent running average fits (n=2) through the average counts. Data are obtained from monthly density censuses of shorebirds performed during high tide for the complete nature reserve in November-February between November 2003 and February 2011. Survey counts for R. avosetta were occasionally missing for February 2006 and January 2007. Population densities significantly declined over time for T. tadorna (simple linear regression: F(1, 6) = 16.95; R² = 0.74; p = 0.006; Durbin-Watson test of serial correlation over time = D = 1.52, correlation = 0.10)

Shellduck feeding traces on microbial biofilm

Further actions: Monitoring nekton and benthos responses to restoration management in the Zwin coastal lagoon

Case study 2: Interactive effects of increased inundation and

nutrient loading on Spartina maritima in the NE Adriatic Sea

Deegan et al. (2012) Coastal eutrophication as a driver of salt marsh loss. Nature 490: Excess in nutrients cause saltmarsh deterioration

9 years of

Testing the joint effect of excess nutrients and increased inundation on Spartina

Experiment using field mesocosms

Stressors: excess nutrients & increased inundation

Other factor: soil type

Wong J. et al. (2015) Sediment-benthos relationships as a tool to assist in conservation practices in a coastal lagoon subjected to sediment change. Marine environmental research

8 scenarios of orthogonal combinations of two levels of:

1) Inundation → low (ambient) vs. high (+10 cm = 20% more inundation: i.e. 2020 scenario, Theseus 2009)

2) Nutrient → low (ambient) vs. high (Osmocote fertiliser NPK: 1.5 mg/L)

3) Soil type → low (~2%) vs. medium (~10%) organic

Study site: Vallona lagoon

Replication: n=8

Growth season July-September

Vallona Lagoon

- Dominant negative inundation effects on plant properties - Root growth worse when increased inundation is coupled with high nutrients Reduced vertical growth keep up with sea level rise Impact on erosion control?

Summary of the two case studies

• Sediment deposition and increased inundation affect saltmarsh ecosystem services

- habitat quality for e.g. shorebirds - plant biomass carbon sequestration & erosion control - benthos & salt marsh mediated effects on regulating and supporting services BUT • The magnitude and direction of stressor impact can be site-specific

depending on environmental conditions - hydrodynamics - nutrient loading

PROPOSITION

With current delays and limitations on the mitigation of global stressors, it is crucial to identify which factors can maintain ecosystem resilience at

local scales.

Investigating interactive effects of global and local stressors (or management actions, i.e.

removal/reduction of a local stressor) across gradients in space and time can therefore assist in

the implementation of conservation strategies.

"The single most important problem is our misguided focus on identifying the single most important problem!”

- Jared Diamond

Acknowledgments Thank you for your attention! MARBIOL and UNIBO colleagues Research funded by the Research Foundation Flanders (FWO) Mares doctoral programme, ANB Contact: carl.vancolen@ugent.be