Data from: The dynamics of Kelp Forests in the Northeast Pacific Ocean and the relationship with environmental drivers

1.The dynamics of foundation species in ecosystems are key to the fate of
many species. Kelp forests are foundation species in temperate ocean
ecosystems and contribute to carbon storage, macronutrient dynamics,
primary production, and biodiversity of myriad associated species.
Downward trends in their abundance globally have been of concern. 2.We
analyzed 26 years of aerial censuses (1989-2015) of 2 canopy kelp species
in Washington State (USA) waters. We compared these modern censuses with
censuses in 1911 and 1912 to determine the persistence of kelp cover over
the past century. Using Auto-regressive Integrated Moving Average (ARIMA)
models, we compared kelp dynamics with likely environmental drivers,
including local environmental variables and ocean indices for this region.
3.Kelp remains at historic levels in many areas, though some eastern
populations in proximity to greater human populations are the exception to
this pattern. Over the last 26 years, kelp abundance showed high spatial
autocorrelation in western areas of Straits of Juan de Fuca, with more
variable populations in the annual species and eastward toward Puget
Sound. Both species covaried positively in their abundance throughout most
of the study area, suggesting environmental factors rather than
competition, drove their dynamics. The population dynamics of these kelp
species showed that the abundance one year previous was an important
predictor, and cyclic dynamics were not indicated using Auto-regressive
Integrated Moving Average (ARIMA) models. Kelp abundance correlated
inversely with the Pacific Decadal Oscillation and the Oceanic Nino Index,
and positively with the North Pacific Gyre Oscillation, indicating that
large-scale processes associated with colder seawater temperatures were
associated with greater relative abundance of kelp. 4.Synthesis. Kelp beds
in the northern California Current Large Marine Ecosystem have mostly
remained persistent over the past century and over many km, but some areas
may have decreased in abundance. The sensitivity of these populations to
indices of ocean climate, our demonstration that a historic 93-year SST
record (Race Rocks, Canada) showed a 0.72°C increase, and the
classification of some areas as high variability-low abundance, suggest
that the viability of these foundational species remain a concern into the
future.