SBC Kelp Forests on Local to Regional SBC Kelp Forests on Local to Regional ScalesScales

SBC Kelp Forests on Local to Regional SBC Kelp Forests on Local to Regional ScalesScales

Kyle Cavanaugh, Dan Reed, Filipe Alberto, Kyle Cavanaugh, Dan Reed, Filipe Alberto, Brian Kinlan, Pete Raimondi, Brian Gaylord, Brian Kinlan, Pete Raimondi, Brian Gaylord,

Libe Washburn, Ali Whitmer, Dave SiegelLibe Washburn, Ali Whitmer, Dave Siegel

Kyle Cavanaugh, Dan Reed, Filipe Alberto, Kyle Cavanaugh, Dan Reed, Filipe Alberto, Brian Kinlan, Pete Raimondi, Brian Gaylord, Brian Kinlan, Pete Raimondi, Brian Gaylord,

Libe Washburn, Ali Whitmer, Dave SiegelLibe Washburn, Ali Whitmer, Dave Siegel

Giant Kelp Characteristics

• Plant life spans: 2 to 3 years

• Frond life spans: about 4 months

• Frond growth can be 0.5 m/day

• Leads to highly dynamic population dynamics

What Controls Giant Kelp Biomass?

NUTRIENTS & TEMPERATURE: ocean processes affecting growth rates & spore production

PHYSICAL DISTURBANCE: waves & currents removing fronds and/or holdfasts, changes in benthic type (rock to sand)

GRAZING: urchins on plants, filter feeders on spores, etc.

SENESCENCE: natural loss of fronds due to age

HUMANS: harvesting, pollution, etc.

Data on > 150 species collected in permanent plots at 20 sites in the Santa Barbara Channel.

Site based measurements of kelp forest structure and dynamics are key component

of SBC LTER long term data

• Surveys provide important information about demographic processes

• Surveys do NOT provide a regional view of kelp forest dynamics

• Need to combine field & satellite observations to understand local to regional scale dynamics

Sampling Forests from Fixed Surveys

SPOT 5 analysis by Cavanaugh et al. MEPS [2010]

MOHK

AQUE

• 30 m resolution multispectral imagery

• Available from 1984-present with a 16 day repeat cycle– Cloud free image every ~6 weeks– Imagery are now free

LANDSAT 5 Imagery

Santa Barbara

Cavanaugh et al. MEPS, in review.

LANDSAT 5 Spectral Analysis• Atmospheric correction (fixed target method)

• Model each pixel as a linear combination of water & kelp endmembers (following Dennison & Roberts, 2003)

• Single kelp & multiple water endmembers (used to account for variable sediment, glint, phytoplankton, etc.)

02/23/200507/04/200610/02/2004

Examples of Spectral Unmixing

clear/quiescent glint plumes

Strong relationship between kelp fraction and diver measured canopy biomass

Biomass from LANDSAT

LANDSAT Kelp Fraction

Tra

nsec

t B

iom

ass

(kg/

m2 )

r2 = 0.62p < 0.001

Spatial Giant Kelp Patterns

Regionl Scale Giant Kelp Dynamics over the SB region

• Regional mean: ~40,000 metric tons of kelp canopy

• Low in winter, high in summer/fall

• Annual cycle superimposed on a 11-13 year cycle

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

Bio

mas

s (k

g)

0

0.5

1.0

1.5

2.0x 108

El N

ino

El N

ino

Physical Data

Santa BarbaraHarvest buoy

Pt. Arguello buoy

• Significant wave height from Harvest buoy (1987-2009)

• Sea Surface Temperature (SST) from Pt. Arguello buoy (1984-2009)

SST is a good proxy for nutrients

Seasonal Forcing

log

(gro

wth

)

Seasonal Forcing• Wave induced mortality is direct and immediate• Effect of SST/nutrients is delayed and complicated

by other factors

Winter Loss Spring/Summer Recovery

r2 = 0.50p < 0.01

r2 = 0.30p = 0.01

Max Wave Height (m) Mean SST (°C)

20

40

60

80

100

Per

cen

t L

oss

16

17

18

19

3 4 5 6 7 8 12 13 14 15 16

Interannual ForcingNPGO PDO ENSO

Mean SST Max Wave Height

1 32 40 5-1-3 -2-4-5Lag (years)

1 32 40 5-1-3 -2-4-5 1 32 40 5-1-3 -2-4-5

1 32 40 5-1-3 -2-4-5 1 32 40 5-1-3 -2-4-5

Cor

rela

tion

w/

kelp

Kelp population controls

biomassrecruitment

wave height

nutrients

wave height

nutrientsbiomass

-

- ++

-

+

-1-24-36-48 0

time (months)

NPGO+

+

Santa Barbara

Pt. Conception

Subregional Variability

• Bin kelp into 1 km coastline segments

• K-means clustering

mean biomass (kg/m2)

Mean kelp cover biomass (kg/m2)

Cluster Analysis

winter

summer

Correlation with physical variables

winter swells

summer swells

Hs

periods > 12 sec

Which 1 km time series are more similar to each other? (assumes 4 clusters)

Long Period Swell

Kelp Forests as a Metapopulation

• Metapopulation: collection of small, discrete

populations (patches) connected via dispersal

• Patches undergo transitions as they are

colonized, grow/shrink & become extinct

• Key metrics include isolation, persistence,

connectivity, etc.

• Appropriate for kelp due to patchy nature and

responses to disturbance

Disturbance and recovery of giant kelp on reefs in southern California occurs routinely

Reed et al. 2006. Marine Metapopulations. Academic Press

0 1 2 3 4 5 60

10

20

30

40

50

Average Extinction Duration (Years)

Rel

ativ

e fr

eque

ncy

(%)

El Niño

N = 69 reefs

Pacific Decadal Oscillation warmPDO cool

Fra

ctio

n of

pat

ches

occ

upie

d

Kilometer-scale dispersal by giant kelp occurs routinely

1. Empirical measurements: Field observations of young microscopic and macroscopic stages showed substantial recruitment several km from the nearest source population

Reed et al. 1988. Ecological Monographs, Reed et al. 2004. Journal of Phycology, Reed et al. 2006. Marine Metapopulations. Academic Press

2. Theoretical estimates from physical transport models: Predictions from models that incorporate advection from currents, turbulence from waves and biological properties of spores suggest that ~ 30% of all spores disperse a minimum of 1 km when subjected to moderate flow velocities and wave heights

Gaylord et al. 2002. Ecology, Gaylord et al. 2006. Ecological Monographs, Reed et al. 2006. Marine

Metapopulations. Academic Press

3. Theoretical estimates based on modeling population genetics using microsatellite markers:Isolation by distance models showed an average dispersal of 0.6 – 3 km depending on the measured current velocity distribution

Alberto et al. 2008. Conservation Genetics, Alberto et al. 2010. Ecology, Alberto et al. in rev. Mol. Ecol.

Kilometer–scale dispersal is sufficient for population connectivity in southern California

0 2 4 6 8 10 12 140

10

20

30

40

50

60

70

Nearest-neighbor distance (km)

Rel

ativ

e fr

eque

ncy

(%)

Most discrete patches of giant kelp are within a couple kilometers of other discrete patches

N = 69 reefs

Reed et al. 2006. Marine Metapopulations. Academic Press

5 kmGiant kelp

Genetic distance

Distance+Continuity

Geographic distance (km)

Habitat continuity

Alberto et al. Ecology [2010]

SBC Kelp Genetics

• Microsatellite markers

show IBD strong signals

• Genetic differences are

also f(habitat continuity)

• Ocean connectivity is

also important (Alberto et al.

in rev. Mol Ecol)

Work underway to expand Landsat 5 analyses throughout CA Coast

Santa Barbara

San Diego

Monterey

Los AngelesSanta Barbara

What’s next…• Complete metapopulation assessment & compare

differences across the CA coast

• Evaluate importance of kelp forest patch age on

genetics, biodiversity, etc.

• Compare regional kelp biomass changes to beach

wrack & harvest observations

• Develop spatial metapopulation model for SBC

kelp forests & assess impacts of future climates

• Others??

Thank You!!