Bottom-up drivers of species interactions on the Oregon Coast

Jonathan Robinson and Bruce MengeOregon State University – PISCO

WSN 2014 Talk

The ocean is changing

Ruggiero et al. 2010

Increasing wave height

Increases in upwelling along the Oregon coast

Huyer et al. 2010

Feely et al. 2009

Increasing ocean acidification

What are the likely consequences for coastal ecosystems?

Long-Term Research in Environmental Biology (LTREB) Project

• Question: How will intertidal community dynamics and structure change with changing climate?

• (Very General) PredictionsChanges could:– Alter ecological subsidies– Alter species interactions – Affect diversity, zonation, abundance– BUT – Directions of change difficult to predict mussels could decrease increased macrophytes sea stars or whelks could decrease increased abundance of prey altered zonation

• Cape Foulweather • Narrower shelf• Offshore currents• Less retentive

• Cape Perpetua• Wider shelf• Mixed currents• More retentive

• Cape Blanco• Narrow shelf• Offshore currents • Stronger upwelling• Less retentive

Today’s focus: Central interaction in most

temperate rocky intertidal communities

Predator – Barnacle – Mussel interaction web

Photo by E. Sanford

Oregon coastal intertidal meta-ecosystem

Oregon capes oceanographic differences generate differences in ecological subsidies

CF CP CB

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phytoplankton

barnacle recruitment

mussel recruitment

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Research Questions

• Effect of predation?• Effects of spatial interactions (competition,

facilitation)?• How do interactions vary with oceanography?

Hypotheses, all varying with oceanographic conditions:• H1: Predation is strong

• H2: Mussels outcompete barnacles

• H3: Barnacles facilitate mussel colonization

Methods• 5 Treatments

+P+B+M -meshCape Foulweather

Cape Perpetua

Cape Blanco

CA

Oregon

WA

+P+B+M +mesh

-P+B+M +mesh

-P+B-M +mesh

-P-B+M +mesh

Methods

Cape Foulweather

Cape Perpetua

Cape Blanco

CA

Oregon

WA

• 5 Replicates• Cleared in spring• Photographed once/twice a

month • Percent cover of species

analyzed• ~1500 pictures analyzed• Results from 2011 & 2012• RMANOVA– Linear Constraints (post hoc)

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p=0.02

• Yes: except for CF 2011, p = 0.02 or more• CP different from CF, CB; consistent with difference in larval retention, food

2012

H1: Predation effect? Varies with oceanography?

+Pred

-Pred

+Pred

-Pred

CF CP CB

All capes:Prey cover in –P > +P

%barnacles%mussels% ephem. algae% perenn. algae

p=0.0005

p=<0.0001p=<0.0001

p=0.004

p=<0.0001

2011

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H2: Competition effect?• Yes but context-dependent

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ns p=0.002 ns

ns p=0.1 ns

CP: If mussels removed during colonization, barnacles persist

CF, CB: Mussel removal had no effect on barnacles

%barnacles%mussels% ephem. algae% perenn. algae

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H3: Facilitation effect?

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No.

ns p=0.07 ns

ns p=0.053 ns

CP: Trend towards lowerabundance of mussels without barnacles, but NS

CF, CB: No difference

%barnacles%mussels% ephem. algae% perenn. algae

Discussion• Predation important everywhere• Competition only occurred at CP sites• Facilitation not observed, WHY?• Field observations suggest that facilitation depends on recruitment rates– When recruitment is low

• Abundances too low for interactions to occur (short-term)

– When recruitment is high• Variable result: other experiments, saw facilitation• In this experiment, mussel recruitment overwhelming, so

even rugose rock surfaces acceptable

LTREB Goals• Study designed to test change through (longer)

time (10 yrs)– So these results are preliminary with respect to

temporal changes• Key result of ACE – Interaction strength and abundance of interactors

is driven by subsidy rates along the capes

Acknowledgements A Huge Thanks To:• The OSU PISCO Lab

FRAsJerod Sapp, Angela Johnson, Shawn Gerrity, Megan Poole, Lindy Hunter Tully Rohrer, Becky Focht, Kim Page-Albins

SRAsSteven Cook, Emma Fraser, Peter McBride, Megan Urton, Marissa Duncan, Dani Smull, Kersten Schnurle, Kamala Earl, Alexander Carsh, Lacey Schrock-Purkey

GradsAllie Barner, Liz Cerny-Chipman, Chenchen Shen, Sarah Close, Jenna Sulliven, Jessie Reimer

UndergradsSilke Bachhuber, Kaitlyn Boze

Photos by: Thomas Robinson

Funding provided by:

A special thanks to Christina Robinson

Questions?

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CCLME (California Current Large Marine Ecosystem)

• Unique large scale study area

• Good place to study rocky intertidal– Why?

• Highly productive• Diverse, highly

dynamic biological communities

• Species interactions (facilitation, competition, and predation)