Estimating scale-dependency in disturbance impacts: El Ni�os and giant kelp forests in the northeast Pacific

Edwards, Matthew S.

doi:10.1007/s00442-003-1452-8

Cited by 140 publications

(205 citation statements)

References 39 publications

Supporting

Mentioning

184

Contrasting

Unclassified

Order By: Relevance

“…Anomalous ocean conditions characterized by high temperature, low salinity, low nutrients and large waves were reported in 1997 and 1998 for the entire west coast of North America, including the Santa Barbara area (Allan & Komar 2002, Chavez et al 2002a). These conditions have been linked to observed large declines in phytoplankton and macroalgal biomass and overall ocean productivity during that period (Chavez et al 2002b, Shipe et al 2002, Edwards 2004, and likely had similar adverse effects on the maturation of fruits and the survival of seedlings in surfgrass. We do not know which specific environmental factors led to the reproductive failures that we observed in surfgrass during the 1997-1998 El Niño.…”

Section: Discussionmentioning

confidence: 94%

Patterns and sources of variation in flowering, seed supply and seedling recruitment in surfgrass Phyllospadix torreyi

Reed

Holbrook²,

Blanchette³

et al. 2009

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

Knowledge of patterns and sources of variation in adult reproduction and juvenile recruitment is essential for understanding the dynamics of populations and their capacity to recover from disturbances. In-depth knowledge of this kind is lacking for many species of seagrass. Here we examined the degree to which temporal and spatial variation in seedling density in the surfgrass Phyllospadix torreyi was explained by the local production and deposition of seeds. We did this by measuring floral density, seed production, seed supply and seedling recruitment at 5 sites near Santa Barbara, California, USA, over a 4 yr period. We found that the local density of dehisced female spadices explained nearly 41% of the variation in the number of seeds caught in seed traps. Large seed crops were common in the absence of nearby males and noticeable numbers of seeds were periodically caught in traps when female flowers were locally rare or absent, suggesting that pollen and seed dispersal occasionally occurred over distances greater than the scale of our study sites (i.e. > 50 m). Overall, the summer densities of female spadices at a site explained > 60% of the variation in the density of seedlings that recruited to the site the following winter. Deviations from positive associations among surfgrass flowers, seeds and seedlings appeared to reflect interannual variability in environmental conditions. Most notable was the coincidence of universally low fruit production and seedling recruitment during the 1997-1998 El Niño event. Seedling density varied independently of rates of seed deposition when all years were examined, but was highly dependent on rates of seed supply when the seedling data from the 1998 El Niño winter were omitted from the analysis. Collectively, our observations demonstrated significant coupling between adult reproduction and local recruitment in surfgrass that was interrupted by adverse growing conditions associated with the 1997-1998 El Niño.

show abstract

Section: Discussionmentioning

confidence: 94%

Patterns and sources of variation in flowering, seed supply and seedling recruitment in surfgrass Phyllospadix torreyi

Reed

Holbrook²,

Blanchette³

et al. 2009

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

show abstract

“…Many kelp forest ecosystems are naturally highly variable on both seasonal and interannual time scales, and over small spatial scales (42)(43)(44), reflecting a high reactivity to environmental drivers and variation in their capacity to resist (45) and recover from both small-and large-scale disturbances (46,47). This wide temporal variation contrasts with other marine foundation species such as seagrasses (48,49) and corals (50), which tend to hold space for many years and take decades to recover from disturbance.…”

Section: Discussionmentioning

confidence: 99%

Global patterns of kelp forest change over the past half-century

Krumhansl

Okamoto

Rassweiler

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

581

524

View full text Add to dashboard Cite

Kelp forests (Order Laminariales) form key biogenic habitats in coastal regions of temperate and Arctic seas worldwide, providing ecosystem services valued in the range of billions of dollars annually. Although local evidence suggests that kelp forests are increasingly threatened by a variety of stressors, no comprehensive global analysis of change in kelp abundances currently exists.Here, we build and analyze a global database of kelp time series spanning the past half-century to assess regional and global trends in kelp abundances. We detected a high degree of geographic variation in trends, with regional variability in the direction and magnitude of change far exceeding a small global average decline (instantaneous rate of change = −0.018 y −1 ). Our analysis identified declines in 38% of ecoregions for which there are data (−0.015 to −0.18 y −1 ), increases in 27% of ecoregions (0.015 to 0.11 y −1 ), and no detectable change in 35% of ecoregions. These spatially variable trajectories reflected regional differences in the drivers of change, uncertainty in some regions owing to poor spatial and temporal data coverage, and the dynamic nature of kelp populations. We conclude that although global drivers could be affecting kelp forests at multiple scales, local stressors and regional variation in the effects of these drivers dominate kelp dynamics, in contrast to many other marine and terrestrial foundation species. A ssessing ecosystem change on a global scale has been instrumental in highlighting the magnitude of human impacts on natural ecosystems. For example, awareness of global declines in fish populations (1), coral reefs (2), and tropical rainforests (3) has substantially increased public interest and subsequent political motivation for environmental conservation. In some cases, global assessments have highlighted complex patterns of change (4, 5), which often reflect variable trajectories among regions (4). SignificanceKelp forests support diverse and productive ecological communities throughout temperate and arctic regions worldwide, providing numerous ecosystem services to humans. Literature suggests that kelp forests are increasingly threatened by a variety of human impacts, including climate change, overfishing, and direct harvest. We provide the first globally comprehensive analysis of kelp forest change over the past 50 y, identifying a high degree of variation in the magnitude and direction of change across the geographic range of kelps. These results suggest region-specific responses to global change, with local drivers playing an important role in driving patterns of kelp abundance. Increased monitoring aimed at understanding regional kelp forest dynamics is likely to prove most effective for the adaptive management of these important ecosystems.

show abstract

“…Pearse & Hines 1979, Kastendiek 1982, Santelices & Ojeda 1984, Edwards 1998, but this approach has not been widely applied. Classification of response groups may be particularly useful for grouping understory algae in subtidal kelp forests where, due to the synergistic effects of a floating surface canopy and a stipitate understory canopy, light regimes are highly variable in space and time (Reed & Foster 1984, Edwards 2004, the present study).…”

Section: Introductionmentioning

confidence: 99%

Effects of shade from multiple kelp canopies on an understory algal assemblage

Clark¹,

Edwards²,

Foster³

2004

Mar. Ecol. Prog. Ser.

115

View full text Add to dashboard Cite

We examined the effects of shade from multiple kelp canopy layers (surface Macrocystis pyrifera canopy, understory Pterygophora californica canopy), both individually and in combination, on an understory algal assemblage in a central Californian kelp forest. The removal of both kelp canopies resulted in a dense recruitment of the understory brown alga Desmarestia ligulata that formed a third canopy layer, which significantly decreased bottom light and the abundance of understory red algae. We subsequently created an additional canopy treatment by removing this third canopy layer. In general, the understory red algae fluctuated seasonally with winter swell intensity, changes in kelp canopy cover, and grazing; and although species richness increased significantly with increased bottom light, red algal bottom cover did not respond significantly to the canopy clearings until 2 yr after the canopies were initially cleared. Red algal cover within the Pterygophora canopy treatment was similar to that in the control treatment. In the absence of Pterygophora, the Macrocystis canopy treatment and 'no canopy' treatment were found to have greater red algal cover and species richness. Individual understory species were rare, which resulted in small effects sizes and thus low statistical power. However, when grouped post hoc, according to how they responded to the canopy clearings (i.e. response groups), we were able to detect canopy treatment effects as much as 1 yr earlier. This method identified that some understory red algae adapted to areas of canopy removal (light-adapted), and others adapted to a variety of light regimes (shade-tolerant). We were able to classify the light-adapted algae into 2 subgroups: the high-light species and the intermediate-light species. Although this method of grouping was done post hoc, our results indicate that it may provide the clearest assessment of how understory algae respond to shading from kelp canopies.KEY WORDS: Canopy shading · Community structure · Kelp forest · Light-adapted · Macrocystis · Pterygophora · Red algae · Shade-tolerantResale or republication not permitted without written consent of the publisher

show abstract

Estimating scale-dependency in disturbance impacts: El Ni�os and giant kelp forests in the northeast Pacific

Cited by 140 publications

References 39 publications

Patterns and sources of variation in flowering, seed supply and seedling recruitment in surfgrass Phyllospadix torreyi

Patterns and sources of variation in flowering, seed supply and seedling recruitment in surfgrass Phyllospadix torreyi

Global patterns of kelp forest change over the past half-century

Effects of shade from multiple kelp canopies on an understory algal assemblage

Contact Info

Product

Resources

About