Paradigm lost, or is top-down forcing no longer significant in the Antarctic marine ecosystem?

By D. Ainley, G. Ballard, Steve Ackley, L. Blight, J. Eastman, S. Emslie, A. Lescroël, S. Olmastroni, S. E. Townsend, C. Tynan and 2 more. Antarctic Science, 2007

110 citations recorded by the source corpus.

Abstract Investigations in recent years of the ecological structure and processes of the Southern Ocean have almost exclusively taken a bottom-up, forcing-by-physical-processes approach relating various species' population trends to climate change. Just 20 years ago, however, researchers focused on a broader set of hypotheses, in part formed around a paradigm positing interspecific interactions as central to structuring the ecosystem (forcing by biotic processes, top-down), and particularly on a “krill surplus” caused by the removal from the system of more than a million baleen whales. Since then, this latter idea has disappeared from favour with little debate. Moreover, it recently has been shown that concurrent with whaling there was a massive depletion of finfish in the Southern Ocean, a finding also ignored in deference to climate-related explanations of ecosystem change. We present two examples from the literature, one involving gelatinous organisms and the other involving penguins, in which climate has been used to explain species' population trends but which could better be explained by including species interactions in the modelling. We conclude by questioning the almost complete shift in paradigms that has occurred and discuss whether it is leading Southern Ocean marine ecological science in an instructive direction.

Subfields: Ecology, Global and Planetary Change, Oceanography

View Paper: https://www.semanticscholar.org/paper/dafc862d9739b40a0a136232092d9d12b37f0eff

How researchers see this paper

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In Ecology

1. P. Trathan
2. D. Ainley
3. R. Pitman
4. J. Durban
5. G. Ballard
6. J. Forcada
7. Y. Ropert‐Coudert
8. S. Hill

In Global and Planetary Change

1. P. Trathan
2. G. Ballard
3. J. Forcada
4. D. Ainley
5. S. Jenouvrier
6. S. Nicol
7. S. Hill
8. J. Durban

In Oceanography

1. J. Durban
2. J. Llopiz
3. C. Choy
4. W. Smith
5. R. Olson
6. J. Forcada
7. E. Hazen
8. P. Ryan

Citations in the corpus

• Cascading top-down effects of changing oceanic predator abundances. (2009, background): “An alternative hypothesis, articulated by some ecologists, is that we have lacked examples of top-down control only because oceanic ecosystems are ‘broken’ ( sensu Ainley et al . 2007 ), with predator losses largely preceding ecological data collection (Dayton et al . 1995; Steneck & Sala 2005; Ain”
• The Importance of Krill Predation in the Southern Ocean (2016, background): “It was recognised that such substantial changes in the marine ecosystem would have resulted in a major ecosystem response across a variety of trophic levels (Sladen 1964, Laws 1977, Ainley et al. 2007).”
• Effects of climate change and fisheries bycatch on Southern Ocean seabirds : a review (2012, unknown): “…of bottom-up or top-down processes on the effect of fish and whale harvesting on Southern Ocean top predators such as seabirds are highly debated (Ainley et al. 2007, Nicol et al. 2007, Ainley & Blight 2008, Barbraud & Cotté 2008, Ainley et al. 2010b), it is at present difficult to quantify the…”
• Trophic cascades in the western Ross Sea, Antarctica: revisited (2015, background): “The effects on penguins of changing cetacean populations in de - cades past have been investigated (Ainley et al. 2007), as has the alteration in penguin foraging behavior in the presence of killer whales Orcinus orca and leo - pard seals Hydrurga leptonyx (Ainley & Ballard 2012; see also Ainley et…”
• Observed and predicted effects of climate on Australian seabirds (2011, background): “However, this ‘bottom-up’ approach may be too simplistic when predicting flow-on effects to seabirds (Hunt et al. 2002; Ainley et al. 2007; Frank et al. 2007; Cury et al. 2008).”
• Cooperative hunting behavior, prey selectivity and prey handling by pack ice killer whales (Orcinus orca), type B, in Antarctic Peninsula waters (2012, background): “…down (and perhaps endangering) prey populations (Guinet et al. 1992; Estes et al. 1998; 1 Springer et al. 2003, 2008; Branch and Williams 2006; Ainley et al. 2007; Bolt et al. 2009; Estes et al. 2009), to being the primary impetus for the breeding migrations of large whales (Corkeron and…”
• Spatial ecology and conservation of seabirds facing global climate change: a review (2009, unknown): “But 'it cannot all be climate' (Ainley et al. 2007), and a vision of bottom-up controlled marine food webs might be all too simplistic.”
• The trophodynamics of marine top predators: Current knowledge, recent advances and challenges (2015, background): “top down processes in structuring marine food webs is gaining increasing attention (Ainley et al., 2007; Cury et al., 2000; Nicol et al., 2007; Polovina and Woodworth-Jefcoats, 2013; Worm and Myers, 2003).”
• Penguin responses to climate change in the Southern Ocean (2009, background): “Disentangling such complexity is an important challenge (Fraser & Patterson, 1997; Patterson et al., 2003; Smetacek & Nicol, 2005; Ainley et al., 2007; Nicol et al., 2007; Trathan et al., 2008b), but an important first step is the identification of climate drivers of ecosystem change, and the…”
• Happy Feet in a Hostile World? The Future of Penguins Depends on Proactive Management of Current and Expected Threats (2019, background): “For example, the commercial removal of top predators in many systems has allowed other taxa to increase in abundance (e.g., Ballance et al., 2006; Ainley et al., 2007, Ainley and Blight, 2009; Trivelpiece et al., 2011; Trathan et al., 2012).”