Giant Kelp Canopy Cover and Biomass from High Resolution Multispectral Imagery for the Santa Barbara Channel Kyle C Cavanaugh, David A Siegel, Brian P Kinlan, Dan C Reed

Macrocystis pyrifera High economic and ecologic importance –“ecosystem engineer” Kelp abundance highly dynamic –Growth rates up to 0.5 m/day –Avg. frond life: 3-5 months –Ave. plant life: 2-3 years

Macrocystis growth and mortality Growth and mortality regulated by water temp, nutrients, depth, bottom type, predation, wave action Nice model system for studying the role of disturbance in regulating ecosystems Kelp biomass data from Kelco visual estimates; Fish observations from Brooks et al 2002

Previous SB Channel surveys Aerial visual canopy biomass estimates by ISP Alginates (monthly from ; entire coast) CDFG 2m resolution aerial surveys using NIR imagery (annual from 2002-present; entire coast) LTER SCUBA transects (monthly for 3 SBC kelp beds from 2002-present) Scale issues…

Research goals 1.Expand spatial and temporal resolution of kelp canopy cover and biomass datasets using high resolution satellite imagery 2.Use this data to model kelp population dynamics in relation to patch size, connectivity, and biophysical forcing

Research Area

Remote Sensing of Macrocystis Surface canopy of giant kelp exhibits typical vegetation spectral signature (red-edge) –Low red reflectance –high near infrared (NIR) reflectance Canopy biomass well correlated to entire forest biomass (r 2 = 0.92)

SPOT Imagery Well suited to differentiate kelp –Spectral bands in the green, red, NIR, SWIR –10 m resolution

SPOT Imagery Datasets 1.Canopy Cover 2.Biomass

Methods: Canopy Cover Principal components analysis calculated for kelp habitat (0-60 m depths) PC band 1 PC band 2 False color SPOT image (8/15/2006) Positive contribution from all 3 bands Glint, sediment loads, atmosphere variations, etc. High NIR, low green and red reflectance Kelp

Methods: Canopy Cover Classification Minimum kelp threshold value selected from 99.9 th %-tile value of offshore (35-60 m) pixels

Validation: Canopy Cover Cover measurements compared with high resolution 2004 CDFG aerial kelp survey SPOT: Oct 29, 2004 CDFG: Sept-Nov 2004 r 2 = 0.98 p < 1*10 -7

Biomass Data More useful for understanding and modeling ecosystem interactions –Turnover rates, export, NPP, etc. Difficult to measure directly –Time and effort intensive

SBC-LTER SCUBA Measurements of Frond Density and Biomass Monthly SCUBA measurements of frond density and biomass made at Arroyo Quemado (AQUE), Arroyo Burro (ABUR), and Mohawk (MOHK) kelp beds. Limited spatial scale

Seasonal kelp biomass changes along 3 LTER transects Maximums in late 2002 Wave driven seasonality apparent

Methods: Biomass Normalized Difference Vegetation Index (NDVI) (NIR-RED) (NIR+RED) Calculated for areas of kelp cover NDVI Transform

Validation: Biomass r 2 = 0.71 p < 1*10 -7 y = 14.33x r 2 = 0.54 p < 1*10 -7

Seasonal kelp biomass changes at Mohawk

Comparison of SPOT vs. Kelco Biomass Data r 2 = 0.73 p < 1*10 -7

Population Dynamics Modeling Persistence, extinction, and biomass changes of kelp patches as a function of size, connectivity, and biophysical factors –High spatial resolution kelp maps will allow us to include effects of sea temperature, nutrients, wave energy, substrate, light attenuation, spore production and dispersal

Data Requirements Kelp Ecological ProcessForcing FactorMethod of AssessmentSpatial ScaleTemporal Scale Kelp cover and biomass change -multispectral imagery (SPOT from ; Landsat/IKONOS/QB before and after) <30 mseasonally Extinctionswell wave stressbuoy data/ CDIP models100 mhourly-daily Spore dispersalcurrentsHF radar. Bottom mounted ADCP observations ~ 100 mhourly-daily Colonizationsubstratesidescan mapped substrate~ 100 mannual-decadal Colonizationbathymetryhi-res gridded bathymetry~ 100 mdecadal Productivitybackground light limitation MODIS incident PAR & Kd490 imagery mdaily Productivitynutrient limitationMODIS/AVHRR SST/nutrient relationships mdaily