Photo: Nathaniel Fletcher

Monica Moritsch mmoritsc@ucsc.edu

Raimondi-Carr Lab

Sea Star Wasting Syndrome and Intertidal Community Composition

• Symptoms – Twisted arms, deflated appearance – Tissue decay, lesions – Often death

Sea Star Wasting Syndrome

Photo: Kit Harma

• Unknown cause and mechanism of spread – Denso-virus involved? – Evolution of virulence? – Environmentally driven?

Photo: Melissa Miner

Sea Star Wasting Syndrome

• Unprecedented geographic extent – San Diego to Alaska

• Previous outbreaks on regional scale

• Affects over 20 species • Mass mortality in short

time period

Sea Star Wasting Syndrome

Photo: Leanne Foster

Photo: Jeff Adams

Severe population declines Pi

sast

er o

chra

ceus

size

(mm

)

piscoweb.org Fall

2013

• Not sure if it’s actually a disease – No causative

pathogen yet

Illustration: Perry Shirley

Disclaimer on Sea Star Wasting Syndrome

Big Question: How does the decline of a keystone predator influence community composition of invertebrates and algae?

Photo: Laura Anderson

Pisaster ochraceus, keystone predator • P. ochraceus, favor

mussels as prey

• Maintain Mytilus californianus lower limits

• Prevent competitive exclusion

From umd.edu, after Paine 1966

Pisaster ochraceus, keystone predator • P. ochraceus, favor

mussels as prey

• Maintain Mytilus californianus lower limits

• Prevent competitive exclusion

Will communities change without Pisaster?

• Strength of keystone predation varies – Length of absence – Physical factors – Sea star density

• Mussel recruitment

– Recruits expand mussel bed

Photo: Melissa Miner

Testing the Paine experiment

• Paine’s classic sea star removal experiment – 1970’s, WA

• Remove Pisaster → – huge Mytilus bed

expansion – Reduced diversity of

algae – Long-lasting changes

Photo: Melissa Miner

Testing the Paine experiment • Dawn Hart’s repetition

with a twist – 2000’s, Monterey Bay – Conditions are different!

• Remove Pisaster → – moderate Mytilus bed

expansion – Reduced diversity of

algae – Changes reversed in 3

years

Photo: Melissa Miner

Testing the Paine experiment • Sea star wasting event

– Natural experiment

• What community changes will we see? – More like Paine’s? – More like Hart’s?

• Ecology on the forefront

Photo: Melissa Miner

Methods: Site selection

• Gradient of pre-SSWS sea star abundance – No SSWS-free sites

• Repeat surveys every

spring in 2014, 2015, 2016 – Need people who

know ALGAE!

Methods: Intertidal surveys • Sea star size, health,

abundance – Timed search

• Mussel recruitment – Tuffys at lower limit

of mussel bed – 2 month intervals

Methods: Intertidal surveys

• Mussel bed lower limits – Distance from top of wall

• Mussel girth – Widest point of valves

• Species composition – All layers of sessile

invertebrates and algae – H’, J’, Bray-Curtis

similarity

16

Hypotheses

• IF keystone predation has major impact – Mussels extend lower – Mussels get bigger – Mussels increase

coverage, crowd out other species

• If keystone predation is unimportant, or weak recruitment – No major changes

Common Algae

Common Algae Patterns Intertidal zonation • High-low • Wet-dry • Sheltered-exposed

Substrate differences • Rugose-smooth • Shaded-sunned • Mussels-bare rock

Regional differences • Monterey-Santa Cruz • Upwelling patterns • Herbivore community

Field Assistants Needed! • Community

composition surveys – May 7-12 – Mornings and early

afternoons • Tuffy dissection (lab)

– Starting June 2015 • Beach visitor surveys

– July - Aug. weekends Monica Moritsch mmoritsc@ucsc.edu