Effects of climate and eutrophication on the diversity of hard bottom communities on the Skagerrak coast 1990-2010

Norderhaug, Kjell Magnus; Gundersen, Hege; Pedersen, A.; Moy, Frithjof E.; Green, Norman Whitaker; Walday, Mats; Gitmark, Janne Kim; Ledang, Anna Birgitta; Bjerkeng, Birger; Hjermann, Dag Øystein; Trannum, Hilde Cecilie

doi:10.3354/meps11306

Cited by 21 publications

(16 citation statements)

References 45 publications

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“…The potential for this decline is considered more likely for species with slow postdisturbance recovery rates [e.g., corals (38)], those species that display little seasonal variability in abundance [e.g., mangroves (39)], or those species experiencing stressors of sufficiently widespread and high magnitude [e.g., fishes (1)]. However, for many taxa, globally coherent signals of change are unlikely when the identity and magnitude of drivers vary widely on local and regional scales (4,17,40), where species and ecotypes within taxonomic groups respond variably to change, or where abiotic and biotic contexts vary widely across geographic locations (41). The global average decline detected by our analysis was modest compared with the large interregional variability in the trajectories of change exhibited by kelps across their range.…”

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.

578

524

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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.

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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.

578

524

View full text Add to dashboard Cite

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“…Gametogenesis in L. digitata gametophytes was readily induced between 5°C and 15°C, with very high to maximum sporophyte recruitment under simulated conditions of long photoperiods and enriched nutrient conditions, a situation that is probably only present along the Norwegian coastline in summer (Wassmann and Aadnesen 1984) or when coastal eutrophication is encountered (Norderhaug et al 2015). The optimum temperature range for gametogenesis of L. digitata reported here is similar to previous studies with Helgoland material that reported high fertility between 5°C and 12°C, and slightly reduced fertility at 17°C (tom Table 3 Müller et al 2008).…”

Section: Discussionmentioning

confidence: 99%

Interactions of daylength, temperature and nutrients affect thresholds for life stage transitions in the kelp Laminaria digitata (Phaeophyceae)

et al. 2017

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Kelp beds worldwide are under pressure from ongoing climate and environmental change. Along European coastlines increases in seawater temperature and changes in nutrient conditions occur where upwelling events are disrupted and also along eutrophicated coasts. In addition, seaweed responses to change may interact with seasonal daylength cycles. We performed a factorial experiment to examine the combined effects of seawater temperatures, nutrient regimes and photoperiod (long and short days) in order to better understand how latitudinal or seasonal differences in daylengths affect the sensitivity of transient microscopic kelp stages of Laminaria digitata from the North Sea to warming and eutrophication. While the optimal temperature range for vegetative gametophyte growth was 10°C-18°C under long summer photoperiod conditions, gametogenesis was induced at lower temperatures between 5°C and 15°C, with maximum sporophyte development under long photoperiods and enriched nutrient regimes, which represent local late spring conditions. Although gametogenesis was fastest at 10°C-15°C, sporophyte recruitment was highest at 5°C. As these particular early life cycle processes in L. digitata have different temperature optima, this may drive the seasonal cycle of recruitment in the field. Increasing summer temperatures due to global warming will increase gametophyte size due to enhanced vegetative growth and inhibition of gametogenesis. This will probably lead to delayed but enhanced recruitment of new sporophytes under cooler autumn to spring conditions over a wide geographical scale, preventing the formation of juvenile sporophytes under stressful summer conditions and possibly changing annual recruitment patterns.

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“…Over the past decades, the impacts of major anthropogenic pressures on coastal and benthic marine biodiversity have been studied intensely. Here, especially field assessments investigated the negative effects arising from bottom trawling (Jennings and Kaiser 1998;Kaiser et al 2006;Tillin et al 2006;Worm et al 2006;Olsgard et al 2008), coastal nutrient loading (Rosenberg and Nilsson 2005;Quijon et al 2008), and climate change (Norderhaug et al 2015). However, since many of these drivers act on the ecosystems simultaneously and over long periods of time Halpern et al 2008), it is difficult to infer cumulative impacts from such assessments (Moksnes et al 2008;Robinson and Frid 2008).…”

Section: Introductionmentioning

confidence: 99%

Marine long-term biodiversity assessment suggests loss of rare species in the Skagerrak and Kattegat region

et al. 2017

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Studies of cumulative and long-term effects of human activities in the ocean are essential for developing realistic conservation targets. Here, we report the results of a recent national marine biodiversity inventory along the Swedish West coast between 2004 and 2009. The expedition revisited many historical localities that have been sampled with the same methods in the early twentieth century. We generated comparable datasets from our own investigation and the historical data to compare species richness, abundance, and geographic distribution of diversity. Our analysis indicates that the benthic ecosystems in the region have lost a large part of its original species richness over the last seven decades. We find evidence that especially rare species have disappeared. This process has caused a more homogenized community structure in the region and diminished historical biodiversity hotspots. We argue that the contemporary lack of rare species in the benthic ecosystems of the Kattegat and Skagerrak offers less opportunity to respond to environmental perturbations in the future and suggest improving the poor representation of rare species in the region. The study shows the value of biodiversity inventories as well as natural history collections in investigations of accumulated effects of anthropogenic activities and for re-establishing species-rich, productive, and resilient ecosystems.

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Effects of climate and eutrophication on the diversity of hard bottom communities on the Skagerrak coast 1990-2010

Cited by 21 publications

References 45 publications

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

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

Interactions of daylength, temperature and nutrients affect thresholds for life stage transitions in the kelp Laminaria digitata (Phaeophyceae)

Marine long-term biodiversity assessment suggests loss of rare species in the Skagerrak and Kattegat region

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