Photo: Nathaniel Fletcher
Monica Moritsch [email protected]
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
• 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 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 [email protected]