The other 93%: trophic cascades, stressors and managing coastlines in non-marine protected areas

Abstract

This paper reviews interactions involving stands of macroalgae on rocky reefs, and presents new data on changing sea surface temperatures (SSTs), as a contribution to the celebration of the fiftieth anniversary of the Leigh Marine Laboratory (LML) of the University of Auckland. The focus is on trophic interactions involving predators, sea urchins and large brown algae, particularly trophic cascades. Of the 369 publications arising from work at LML, 40 have been on key aspects of these trophic interactions. Quantitative investigations of the structure of kelp bed communities and mechanistic studies involving manipulative field-based experiments, essentially a bottom-up perspective based on habitats and key species, dominated the research through the 1980s. From the mid-1990s onwards, the focus was more on marine reserves and a hierarchical, top-down perspective of community structure, with a particular focus on the role of predatory fish, and marine reserves as a tool of management. I discuss these models of community structure of kelp beds within the wider context of the New Zealand nearshore zone, the varying biogeographic regimes around the coastline, diffuse stressors and the changing nearshore climate. I show there appears to have been a significant warming trend in SST in northeast and northwest New Zealand over the past 30 years. I conclude that a trophic effects model is unlikely to apply to much of the coastline of New Zealand, and that a model involving multiple effects, including bottom-up forces, environmental and climatic influences, species' demographics, and catchment-derived sedimentation is more appropriate for kelp communities over most of the country. New management models are needed to safeguard marine resources and the services they provide.

Regional differences in kelp forest interaction chains are influenced by both diffuse and localized stressors

“…In New Zealand, the majority of marine reserves are relatively small and are focused on protecting the local dynamics of coastal reef communities (Thrush et al. , Schiel ). As many reef‐associated fishes and large rock lobsters have limited home ranges, they typically respond well to spatial management (Barrett ), as evidenced by widespread increases in abundance and size structure of otherwise exploited species within New Zealand's marine reserves (Willis and Anderson , Pande and Gardner , Jack and Wing , Costello ).…”

“…, Shears and Babcock , ). However, this relationship has not been as extensively studied in southern New Zealand, primarily because of a scarcity of marine reserves, with the exception of studies in Stewart Island and Fiordland, where there is a network of marine reserves (Schiel , Wing and Jack , Wing et al. ).…”

“…The magnitude of the effects of fishing on trophic interaction chains may be influenced by various abiotic and biotic factors including predator diversity, system productivity, and the amount and distribution of fishing pressure on the community (Finke andDenno 2004, Salomon et al 2010). In addition to the indirect effects of fishing and broad-scale removal of predatory species, kelp communities are increasingly being affected by a range of diffuse stressors including disease, proliferation of introduced species, nutrient pollution, increasing sea surface temperatures, modified subtidal light environments, and smothering linked to coastal sedimentation (Allison et al 1998, Sala et al 1998, Airoldi 2003, Schiel 2013. Understanding how fishing affects kelp communities is critical to maintaining diversity and productivity of temperate reef ecosystems, particularly in the context of the intensifying array of diffuse anthropogenic stressors.…”

Overthrowing a regime shift: displacement of sea urchins by abalone in a kelp forest ecosystem

“…An important component of this comparison is that the site is contained within a National Park with a pristine forested catchment. The result is therefore an effective control for external influences from land-based sedimentation and nutrient pollution, which are dominant drivers on survival, growth and recruitment of macroalgae and kelp forest grazers including abalone and sea urchins at many mainland sites in New Zealand that have heavily modified catchments (Schiel 2013). In this context the no-take marine reserve provided the basis for an ecological experiment that was sufficiently large (.1 km) to encompass effective v www.esajournals.org population sizes of the abalone H. iris (Stephens et al 2006) and sufficiently long-term (.10 years) to capture important changes in population trajectories of both E. chloroticus and H. iris (e.g., Wing 2009).…”

Commemorating 50 years of marine science at the Leigh Marine Laboratory

“…Third, there is a considerable debt owed in conceptual terms to visiting scientists such as Joe Connell (University of California, Santa Barbara) and Tony Underwood (University of Sydney), as pointed out by Schiel (2013). Joe Connell's ideas on stability and variation in natural communities (e.g.…”