Seaweed structure shapes trophic interactions: A case study using a mid-trophic level fish species

O'Brien, Brandon S.; Mello, Kristen; Litterer, Amber; Dijkstra, Jennifer A.

doi:10.1016/j.jembe.2018.05.003

Cited by 34 publications

(22 citation statements)

References 62 publications

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“…For instance, kelp forests dominated by the warm‐temperate species will still exhibit high rates of carbon capture, as plant primary production—and therefore carbon assimilation—was higher than that of the cool‐water kelp. Both species are also morphologically similar and form canopies of similar heights and plant densities (Smale et al., ; Supporting Information Table ) and, as such, kelp forests dominated by the range‐expanding species are likely to continue to provide habitat for fish, invertebrate, and algal species (O'Brien, Mello, Litterer, & Dijkstra, ; Teagle, Moore, Jenkins, & Smale, ). That said, recent work has shown that the epibiotic assemblages associated with kelp stipes, which are typically dominated by red seaweeds and sessile invertebrates, are less diverse in the warm‐temperate species (Teagle & Smale, ).…”

Section: Discussionmentioning

confidence: 99%

Can ecosystem functioning be maintained despite climate‐driven shifts in species composition? Insights from novel marine forests

2018

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Climate change is driving a redistribution of species and the reconfiguration of ecological communities at a global scale. Persistent warming in many regions has caused species to extend their geographical ranges into new habitats, with thermally tolerant species often becoming competitively dominant over species with colder affinities. Although these climate‐driven changes in species abundance and diversity are well documented, their ecosystem‐level implications are poorly understood, and resolving whether reconfigured communities can maintain fundamental ecosystem functions represents a pressing challenge in an increasingly warmer world. Here, we investigated how climate‐driven substitutions of foundation species influence processes associated with the cycling of organic matter (biomass production, detritus flow, herbivory, decomposition) by comparing two habitat‐forming kelp species with contrasting thermal affinities. We examined the wider ecosystem consequences of such shifts for the observed (and predicted) emergence of novel marine forest communities in the NE Atlantic, which are expected to become more dominated by range‐expanding, warm‐temperate kelp species. Warm‐temperate kelps both accumulated and released 80% more biomass than the cold‐temperate species despite being taxonomically closely related and morphologically similar. Furthermore, the warm‐temperate species accumulated biomass and released detritus year‐round, whereas the cold‐temperate species did so during short, discrete periods. The warm‐temperate kelps supported higher densities of invertebrate grazers and were a preferred food source. Finally, their detritus decomposed 6.5 times faster, despite supporting comparable numbers of detritivores. Overall, our results indicate an important shift in organic matter circulation along large sections of NE Atlantic coastline following the climate‐driven expansion of a warm‐affinity kelp, with novel forests supplying large amounts of temporally continuous—yet highly labile—organic matter. Synthesis. Collectively, our results show that, like species invasions, climate‐driven range expansions and consequent shifts in the identity of dominant species can modify a wide range of important ecosystem processes. However, alterations in overall ecosystem functioning may be relatively limited where foundation species share similar ecological and functional traits.

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Section: Discussionmentioning

confidence: 99%

Can ecosystem functioning be maintained despite climate‐driven shifts in species composition? Insights from novel marine forests

2018

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“…A core function of habitat-forming species is the creation of physically complex living space and shelter on reefs for a variety of flora and fauna. Where tropicalisation causes shifts in benthic composition (e.g., by shifting from kelp to turf algae as the dominant taxa), refuges will be modified, which may lead to mortality of some species (O'Brien, Mello, Litterer, & Dijkstra, 2018) or even declines of whole trophic groups that rely on specific refuges (Rogers, Blanchard, Newman, Dryden, & Mumby, 2018).…”

Section: Provision Of Habitat and Nursery Functions And Implicationmentioning

confidence: 99%

Tropicalisation of temperate reefs: Implications for ecosystem functions and management actions

et al. 2019

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Temperate reefs from around the world are becoming tropicalised, as warm‐water species shift their distribution towards the poles in response to warming. This is already causing profound shifts in dominant foundation species and associated ecological communities as canopy seaweeds such as kelp are replaced by tropical species. Here, we argue that the cascading consequences of tropicalisation for the ecosystem properties and functions of warming temperate reefs depend largely on the taxa that end up dominating the seafloor. We put forward three potential tropicalisation trajectories, that differ in whether seaweeds, turf or corals become dominant. We highlight potential gains to certain ecosystem functions for some tropicalisation endpoints. For example, local benthic fish productivity may increase in some tropicalised reefs as a higher proportion of primary production is directly consumed, but this will be at the expense of other functions such as carbon export. We argue that understanding these changes in flows of energy and materials is essential to formulate new conservation strategies and management approaches that minimise risks as well as capture potential opportunities. Regardless of which trajectory is followed, tropicalised systems represent largely novel ecosystem configurations. This poses major challenges to traditional conservation and environmental management approaches, which typically focus on maintaining or returning species to particular locations. We outline management practices that may either mitigate predicted structural and functional changes or make the most of potential new opportunities in tropicalised reefs. These include marine protected areas to increase resilience and connectivity, the development of new fisheries that target range‐expanding invaders, and assisted evolution and migration strategies to facilitate the dominance of large habitat formers like corals or seaweeds. We highlight important ecological and ethical challenges associated with developing novel approaches to manage tropicalised reefs, which may need to become increasingly interventionist. As technological innovations continue to emerge, having clear goals and considering the ethics surrounding interventions among the broader community are essential steps to successfully develop novel management approaches. A plain language summary is available for this article.

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“…In our region, the dominant kelps, Saccharina latissima, Laminaria digitata, and Agarum clathratum, have long flat blades that provide a canopy over the seafloor. Previous studies demonstrate that the large blades of kelp are used as shelter for the dominant residential fish, cunner (Vasquez et al 2014, O'Brien et al 2018. Shelter is critical to the survival of this species as it goes into torpor after dark and below temperatures of 5°C (Haugaard andIrving 1943, Dew 1976).…”

Section: Discussionmentioning

confidence: 99%

“…Pollock are mostly pelagic, but they sometimes feed on benthic prey and, thus, may be indirectly affected by changes in the seascape, particularly if these changes result in less shelter for their prey. If prey for pollock and other pelagic predators becomes more easily accessible due to a loss of kelp canopy (O'Brien et al 2018), it may be a temporary boon to those predators.…”

Section: Discussionmentioning

confidence: 99%

Temperature, phenology, and turf macroalgae drive seascape change: Connections to mid‐trophic level species

et al. 2019

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2019. Temperature, phenology, and turf macroalgae drive seascape change: Connections to mid-trophic level species.Abstract. Landscape patterns created by the structure and form of foundational species shape ecological processes of community assembly and trophic interactions. In recent years, major shifts in foundation species have occurred in multiple ecosystems. In temperate marine systems, many kelp beds have shifted to turf macroalgae habitats with unknown consequences on seascape patterns or changes in the ecological processes that maintain communities. We investigated the effect of turf macroalgae on seascape patterns in three habitats dominated by kelp and turf macroalgae and those that have mixed species composition. We also examined decadal elevations in temperature with known growth and reproductive phenology of kelp and turf macroalgae to provide a mechanistic understanding of the factors that will continue to shape these seascapes. Our results indicate that turf macroalgae produce a more heterogeneous habitat with greater primary free space than those that are mixed or dominated by kelp. Further, we examined the relationship between seascape patterns and richness and abundance of fishes in each habitat. Results showed that patch size was positively related to the abundance of fish in habitat types, suggesting that turf-induced heterogeneity may lead to fewer observed fishes, specifically the mid-trophic level species, cunner, in these habitats. Overall, our results suggest that persistence of this habitat is facilitated by increasing temperature that shorten the phenology of kelps and favor growth and reproduction of turf macroalgae that make them poised to take advantage of free space, regardless of season.

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Seaweed structure shapes trophic interactions: A case study using a mid-trophic level fish species

Cited by 34 publications

References 62 publications

Can ecosystem functioning be maintained despite climate‐driven shifts in species composition? Insights from novel marine forests

Can ecosystem functioning be maintained despite climate‐driven shifts in species composition? Insights from novel marine forests

Tropicalisation of temperate reefs: Implications for ecosystem functions and management actions

Temperature, phenology, and turf macroalgae drive seascape change: Connections to mid‐trophic level species

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