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Marine Ecology Progress Series

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MEPS 543:141-152 (2016)  -  DOI:

Large-scale degradation of a kelp ecosystem in an ocean warming hotspot

Karen Filbee-Dexter1,*, Colette J. Feehan1,2, Robert E. Scheibling1

1Department of Biology, Dalhousie University, Halifax, NS, B3H4R2, Canada
2Present address: Friday Harbor Laboratories, University of Washington, Friday Harbor, WA 98250, USA
*Corresponding author:

ABSTRACT: Understanding the impacts of climate change on biological systems requires observational data over multi-decadal time spans and broad spatial scales. Extensive research at an ocean warming hotspot off Nova Scotia, Canada, enabled us to evaluate the impact of 3 decades of observed temperature rise on a coastal marine ecosystem. Here, we document changes in the kelp community from sites monitored since 1949, 1968 and 1984, and from coastal surveys in 1982, 2000, 2007 and 2014. We show that mean kelp biomass has declined by 85-99% over the past 4-6 decades, and a catastrophic phase shift has occurred from luxuriant kelp beds to rocky reefs dominated by opportunistic turf-forming and invasive algae. This shift likely represents a persistent change, driven by multiple biotic and abiotic interactions, with positive feedback mechanisms (e.g. sediment accumulation) that stabilize the invasive/turf-algal state. This study is the first to show multi-decadal declines in kelp related to warming temperatures in the Northwest Atlantic. The large-scale degradation of an important coastal ecosystem within a warming hotspot presents a troubling example of the instability of marine systems in a rapidly changing ocean environment.

KEY WORDS: Kelp beds · Turf algae · Invasive seaweeds · Climate change · Phase shift · Rocky reefs · Seawater temperature

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Cite this article as: Filbee-Dexter K, Feehan CJ, Scheibling RE (2016) Large-scale degradation of a kelp ecosystem in an ocean warming hotspot. Mar Ecol Prog Ser 543:141-152.

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