Region‐wide changes in marine ecosystem dynamics: state‐space models to distinguish trends from step changes

Spencer, Matthew; Mieszkowska, Nova; Robinson, Leonie A.; Simpson, Stephen D.; Burrows, Michael T.; Birchenough, Silvana N.R.; Capasso, E.; Cleall-Harding, Polly; Crummy, Julia; Duck, Callan; Eloire, Damien; Frost, Matthew; Hall, Ailsa J.; Hawkins, Stephen J.; Johns, David G.; Sims, David; Smyth, Tim; Frid, Chris

doi:10.1111/j.1365-2486.2011.02620.x

Cited by 17 publications

(8 citation statements)

References 62 publications

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“…Those changes often reflected apparent warm-to-cold or cold-to-warm regime shifts in physical oceanography (Anderson & Piatt 1999, Montevecchi 2007, Hatch 2013. The response of the biological community is often rapid and difficult to reverse, once environmental change reaches a tipping point (Overland et al 2010, Spencer et al 2012). In our case, the cold-towarm shift was clearly associated with a reduction in ice cover, as ice is an important habitat for Boreogadus (Crawford & Jorgenson 1993, Gradinger & Bluhm 2004.…”

Section: Discussionmentioning

confidence: 99%

Seabird diet changes in northern Hudson Bay, 1981-2013, reflect the availability of schooling prey

Gaston¹,

Elliott²

2014

Mar. Ecol. Prog. Ser.

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Ongoing climate change is altering Arctic marine ecosystems with major consequences for food-webs. Seabirds, by foraging over large marine areas but returning regularly to their breeding colonies, provide a good medium for tracking such changes. We studied the prey delivered to nestling thick-billed murres Uria lomvia at a colony in northern Hudson Bay, Canada, over the period 1981−2013. During that period, ice conditions in the region altered substantially, with earlier break-up and clearance. This change was not gradual but mainly occurred in the mid1990s. Breeding chronology also advanced, but not as fast as early summer ice clearance advanced. Ice conditions strongly affected diet, presumably reflecting the change in the timing of breeding relative to ice clearance. Of the dominant species in the diet, the proportion of Arctic cod Boreogadus saida decreased and the proportion of capelin Mallotus villosus increased over the 33 yr period, even after ice effects were taken into account, suggesting a progressive and cumulative effect of environmental change on the marine community. Those cumulative changes were manifested primarily in the diet representation of the most frequent taxa (cod and capelin), with variation in secondary diet components being driven by the availability of the dominant taxa. Diet diversity, representing an increase in the proportion of benthic fish (stichaeids, zoarcids, pholids and sculpins) and invertebrates (squid, amphipods and crustaceans), increased when ice cover was low, and hatching was late relative to ice break-up. Chick growth rates were low when the proportion of benthic fish was high. Hence, although it appears that growth rates are influenced by diet composition, it is more likely that they reflect the availability of the dominant schooling prey species, rather than any nutritional deficiency in benthic species.KEY WORDS: Ice cover · Climate change · Forage fish · Thick-billed murre · Uria lomvia Resale or republication not permitted without written consent of the publisher

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Section: Discussionmentioning

confidence: 99%

Seabird diet changes in northern Hudson Bay, 1981-2013, reflect the availability of schooling prey

Gaston¹,

Elliott²

2014

Mar. Ecol. Prog. Ser.

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“…b) and commercial catch (Fig. h) on biology PC1 and PC2, respectively, also suggest the importance of incremental ecosystem forcing on biological change in the region, which argues against an understanding of regional ecosystem dynamics based entirely on abrupt shifts between quasi‐steady states (Lees et al ., ; Spencer et al ., ; Litzow & Mueter, ).…”

Section: Discussionmentioning

confidence: 99%

“…6b) and commercial catch (Fig. 6h) on biology PC1 and PC2, respectively, also suggest the importance of incremental ecosystem forcing on biological change in the region, which argues against an understanding of regional ecosystem dynamics based entirely on abrupt shifts between quasi-steady states (Lees et al, 2006;Spencer et al, 2012;Litzow & Mueter, 2013). Understanding the operation of marine ecosystems at large spatial scales requires the use of observational data sets that provide weak inference (Platt, 1964), are open to competing interpretations (e.g., Frank et al, 2013;Greene, 2013), and often suggest statistical forcing-response relationships that quickly break down as further observational data are collected (Myers, 1998).…”

Section: Discussionmentioning

confidence: 99%

Reassessing regime shifts in the North Pacific: incremental climate change and commercial fishing are necessary for explaining decadal‐scale biological variability

Litzow

Mueter

Hobday

2013

Global Change Biology

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In areas of the North Pacific that are largely free of overfishing, climate regime shifts - abrupt changes in modes of low-frequency climate variability - are seen as the dominant drivers of decadal-scale ecological variability. We assessed the ability of leading modes of climate variability [Pacific Decadal Oscillation (PDO), North Pacific Gyre Oscillation (NPGO), Arctic Oscillation (AO), Pacific-North American Pattern (PNA), North Pacific Index (NPI), El Niño-Southern Oscillation (ENSO)] to explain decadal-scale (1965-2008) patterns of climatic and biological variability across two North Pacific ecosystems (Gulf of Alaska and Bering Sea). Our response variables were the first principle component (PC1) of four regional climate parameters [sea surface temperature (SST), sea level pressure (SLP), freshwater input, ice cover], and PCs 1-2 of 36 biological time series [production or abundance for populations of salmon (Oncorhynchus spp.), groundfish, herring (Clupea pallasii), shrimp, and jellyfish]. We found that the climate modes alone could not explain ecological variability in the study region. Both linear models (for climate PC1) and generalized additive models (for biology PC1-2) invoking only the climate modes produced residuals with significant temporal trends, indicating that the models failed to capture coherent patterns of ecological variability. However, when the residual climate trend and a time series of commercial fishery catches were used as additional candidate variables, resulting models of biology PC1-2 satisfied assumptions of independent residuals and out-performed models constructed from the climate modes alone in terms of predictive power. As measured by effect size and Akaike weights, the residual climate trend was the most important variable for explaining biology PC1 variability, and commercial catch the most important variable for biology PC2. Patterns of climate sensitivity and exploitation history for taxa strongly associated with biology PC1-2 suggest plausible mechanistic explanations for these modeling results. Our findings suggest that, even in the absence of overfishing and in areas strongly influenced by internal climate variability, climate regime shift effects can only be understood in the context of other ecosystem perturbations.

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“…The methodological approach here adopted has several inherent limits: revisiting instead of time series analysis cannot help individuating when exactly a phase shift has occurred (Spencer et al, 2012); using only semiquantitative data may blur the understanding of ecosystem shifts (Giakoumi, 2014); adopting time-based random paths rather than rigorous fixed quadrats or transects augments the possibility of haphazard effects . This notwithstanding, our results proved successful in illustrating ecological change and evaluating its magnitude.…”

Section: Discussionmentioning

confidence: 99%

Thirty years after - dramatic change in the coastal marine habitats of Kos Island (Greece), 1981-2013.

2014

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Results of recent fieldwork were compared with data collected in 1981, taken as a reference condition. Surveys were conducted with the same method (time-based visual census along random paths), in the same sites, by the same people. Semi-quantitative inventories of conspicuous species were analysed by univariate and multivariate techniques. Available information on the main potential stressors indicated that a regime shift has occurred in these 30+ years: sea surface temperature rose by1-2°C, human pressure grew impressively, and invasion by several alien species took place. Consistently, a phase shift occurred in the biological communities. Of the 120 conspicuous species found in total, only 51 were common to both surveys; 30 species ('losses') were found in 1981 but not again in 2013, 38 ('gains') were found exclusively in 2013, 16 ('winners') increased their abundance, 8 ('losers') got scarcer, and 28 underwent little or no change. Gains included 7 alien, 2 nitrophilic, and 7 thermophilic species. Multivariate analysis evidenced biotic homogenisation in 2013 and huge change in rocky reef habitats. The once flourishing algal forests have disappeared to leave space to sponges and wide areas of bare substratum. This has most probably been the result of overgrazing by alien herbivorous fishes (Siganus luridus and S. rivulatus), whose establishment and spread has been favoured by seawater warming; the synergic action of local human impacts was also evidenced.

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Region‐wide changes in marine ecosystem dynamics: state‐space models to distinguish trends from step changes

Cited by 17 publications

References 62 publications

Seabird diet changes in northern Hudson Bay, 1981-2013, reflect the availability of schooling prey

Seabird diet changes in northern Hudson Bay, 1981-2013, reflect the availability of schooling prey

Reassessing regime shifts in the North Pacific: incremental climate change and commercial fishing are necessary for explaining decadal‐scale biological variability

Thirty years after - dramatic change in the coastal marine habitats of Kos Island (Greece), 1981-2013.

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