MEPS 733:1-26 (2024) - DOI: https://doi.org/10.3354/meps14548
Local and regional variation in kelp loss and stability across coastal British Columbia
Samuel Starko1,2,3,*, Brian Timmer1,3, Luba Reshitnyk4, Matthew Csordas1,3, Jennifer McHenry1, Sarah Schroeder5, Margot Hessing-Lewis4, Maycira Costa5, Amanda Zielinksi6, Rob Zielinksi6, Sarah Cook7, Rob Underhill8, Leanna Boyer8,9, Christopher Fretwell8, Jennifer Yakimishyn10, William A. Heath11, Christine Gruman12, Dipti Hingmire13, Julia K. Baum1,3,#, Christopher J. Neufeld3,14,#
#These authors contributed equally to this work as co-senior authors
ABSTRACT: Kelp forests are among the most abundant coastal marine habitats but are vulnerable to climate change. The Northeast Pacific has experienced recent large-scale changes in kelp abundance and distribution, but little is known about changes north of the British Columbia (BC)-Washington border. Here, we assessed whether and how floating canopy kelp (Macrocystis pyrifera, Nereocystis luetkeana) distributions have changed in recent decades along the extensive coast of BC. We assembled and analysed available kelp distributional data, comparing snapshots of kelp linear extent from 1.5-3 decades ago (1994-2007) to recently collected data (2017-2021) across 11 different subregions spanning the province. We then leveraged timeseries, where available (n = 7 data sets), to contextualise patterns of change. In aggregate, the data suggest that kelp forests have declined considerably in some parts of the province, but with variable patterns of change across BC. In the warmest areas (southern BC), kelp persistence was negatively correlated with mean summer sea surface temperatures, which at times exceeded known thermal tolerances. In contrast, in northern subregions, top-down control by sea urchins and otters appeared to modulate kelp dynamics, with declines occurring in 2 subregions despite cool ocean temperatures. Timeseries data suggest that many declines occurred around the 2014-2016 marine heatwave, an event associated with sustained warming and altered trophic dynamics. Our results suggest that the extent of BC’s kelp forests has declined in some places in recent decades, but that regional and local-scale factors influence their responses to environmental change.
KEY WORDS: Climate change · Extirpation · Kelp forest · Marine heatwaves · Sea star wasting disease · Trophic cascade · Macrocystis · Nereocystis
Full text in pdf format  Supplementary material | Cite this article as: Starko S, Timmer B, Reshitnyk L, Csordas M and others (2024) Local and regional variation in kelp loss and stability across coastal British Columbia. Mar Ecol Prog Ser 733:1-26. https://doi.org/10.3354/meps14548
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