Remote Sensing Assessment of Kelp Forest Productivity
Richard
C
Zimmerman, Old Dominion University, rzimmerm@odu.edu
(Presenting)
Heidi
M
Dierssen, University of Connecticut, heidi.dierssen@uconn.edu
W
Paul
Bissett, Florida Environmental Research Institute, pbissett@flenvironmental.org
Victoria
J
Hill, Old Dominion University, vhill@odu.edu
The role of coastal ecosystems in global carbon budgets has been long recognized, but their complex spatial and temporal textures have challenged our ability to quantify their roles in the global carbon cycle. Recent advances in airborne imaging spectroscopy now provide the spatial and spectral resolution necessary to quantify the abundance of marine macrophytes at spatial scales necessary to develop an accurate estimate of system-level productivity. Giant kelp forests that dominate subtidal rocky habitats throughout the temperate eastern Pacific are characterized by floating surface canopies that generates strong reflectance signals in the NIR that are amenable to NDVI based determination of standing biomass and net productivity. Our analysis revealed the highly productive areas along the central California coast are capable of supporting more than 100 dry tons of kelp biomass per linear km of coastline, and d daily productivity exceeding 1 metric ton per km per day. Kelp forests along the Santa Barbara Coast in the less productive waters of the Southern California bight supported about half the standing biomass and less than 1/3 of the daily productivity observed along central California. These differences may reflect spatial and temporal differences in ocean forcing and the seasonality of nutrient availability between these biogeographic provinces. Unfortunately, the high spatial resolution used in our analysis is available only from airborne sensors that are unable to provide routine temporal coverage. Reducing the spatial resolution of the quantified scenes to those available routinely from satellite-based sensors caused the retrieved estimates of biomass and productivity to be overestimated in a stepwise fashion, with critical steps occurring at resolution levels of 10 m2 (30% bias) and 40 m2 (250% bias) which probably represent critical dimensions in the scaling of kelp forest patch size.
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