8 research outputs found
Habitat configurations shape the trophic and energetic dynamics of reef fishes in a tropicalâtemperate transition zone: implications under a warming future
Understanding the extent to which speciesâ traits mediate patterns of community assembly is key to predict the effect of natural and anthropogenic disturbances on ecosystem functioning. Here, we apply a trait-based community assembly framework to understand how four different habitat configurations (kelp forests, Sargassum spp. beds, hard corals, and turfs) shape the trophic and energetic dynamics of reef fish assemblages in a tropicalâtemperate transition zone. Specifically, we tested (i) the degree of trait divergence and convergence in each habitat, (ii) which traits explained variation in speciesâ abundances, and (iii) differences in standing biomass (kg haâ1), secondary productivity (kg haâ1 dayâ1) and turnover (% dayâ1). Fish assemblages in coral and kelp habitats displayed greater evidence of trait convergence, while turf and Sargassum spp. habitats displayed a higher degree of trait divergence, a pattern that was mostly driven by traits related to resource use and thermal affinity. This filtering effect had an imprint on the trophic and energetic dynamics of reef fishes, with turf habitats supporting higher fish biomass and productivity. However, these gains were strongly dependent on trophic guild, with herbivores/detritivores disproportionately contributing to among-habitat differences. Despite these perceived overall gains, turnover was decoupled for fishes that act as conduit of energy to higher trophic levels (i.e. microinvertivores), with coral habitats displaying higher rates of fish biomass replenishment than turf despite their lower productivity. This has important implications for biodiversity conservation and fisheries management, questioning the long-term sustainability of ecological processes and fisheries yields in increasingly altered marine habitats.publishedVersio
Habitat configurations shape the trophic and energetic dynamics of reef fishes in a tropicalâtemperate transition zone:implications under a warming future
Understanding the extent to which speciesâ traits mediate patterns of community assembly is key to predict the effect of natural and anthropogenic disturbances on ecosystem functioning. Here, we apply a trait-based community assembly framework to understand how four different habitat configurations (kelp forests, Sargassum spp. beds, hard corals, and turfs) shape the trophic and energetic dynamics of reef fish assemblages in a tropicalâtemperate transition zone. Specifically, we tested (i) the degree of trait divergence and convergence in each habitat, (ii) which traits explained variation in speciesâ abundances, and (iii) differences in standing biomass (kg ha(â1)), secondary productivity (kg ha(â1)Â day(â1)) and turnover (% day(â1)). Fish assemblages in coral and kelp habitats displayed greater evidence of trait convergence, while turf and Sargassum spp. habitats displayed a higher degree of trait divergence, a pattern that was mostly driven by traits related to resource use and thermal affinity. This filtering effect had an imprint on the trophic and energetic dynamics of reef fishes, with turf habitats supporting higher fish biomass and productivity. However, these gains were strongly dependent on trophic guild, with herbivores/detritivores disproportionately contributing to among-habitat differences. Despite these perceived overall gains, turnover was decoupled for fishes that act as conduit of energy to higher trophic levels (i.e. microinvertivores), with coral habitats displaying higher rates of fish biomass replenishment than turf despite their lower productivity. This has important implications for biodiversity conservation and fisheries management, questioning the long-term sustainability of ecological processes and fisheries yields in increasingly altered marine habitats. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00442-022-05278-6
Intergrading reef communities across discrete seaweed habitats in a temperateâtropical transition zone:Lessons for species reshuffling in a warming ocean
Temperate reefs are increasingly affected by the direct and indirect effects of climate change. At many of their warm range edges, coolâwater kelps are decreasing, while seaweeds with warmâwater affinities are increasing. These habitatâforming species provide different ecological functions, and shifts to warmâaffinity seaweeds are expected to modify the structure of associated communities. Predicting the nature of such shifts at the ecosystem level is, however, challenging, as they often occur gradually over large geographical areas. Here, we take advantage of a climatic transition zone, where coolâaffinity (kelp) and warmâaffinity (Sargassum) seaweed forests occur adjacently under similar environmental conditions, to test whether these seaweed habitats support different associated seaweed, invertebrate, coral, and fish assemblages. We found clear differences in associated seaweed assemblages between habitats characterized by kelp and Sargassum abundance, with kelp having higher biomass and seaweed diversity and more coolâaffinity species than Sargassum habitats. The multivariate invertebrate and fish assemblages were not different between habitats, despite a higher diversity of fish species in the Sargassum habitat. No pattern in temperature affinity of the invertebrate or fish assemblages in each habitat was found, and few fish species were exclusive to one habitat or the other. These findings suggest that, as ocean warming continues to replace kelps with Sargassum, the abundance and diversity of associated seaweeds could decrease, whereas fish could increase. Nevertheless, the more tropicalized seaweed habitats may provide a degree of functional redundancy to associated fauna in temperate seaweed habitats
Environmental stress drives herbivory rates and species selection in subtidal seagrass communities
Grazing is a fundamental ecological process structuring seagrass
ecosystems, yet the environmental drivers influencing grazing are poorly
understood. Whilst the stress gradient hypothesis (SGH) is commonly used to
predict competitive species interactions under environmental stress, it is
possible to adapt the mechanistic model behind the concept to include predictions
for herbivory. In subtidal marine systems, however, this modified SGH has
seldom been tested.<br><br><div>We deployed forage-choice assays using the five most common seagrass species
of Shark Bay (<i>Amphibolis antarctica,
Posidonia australis, Halodule uninervis, Cymodocea angustata </i>and<i> Halophila ovalis</i>), to determine whether
herbivory pressure and feeding choice changed across a salinity-stress gradient
from normal oceanic salinities (~38â°) to hyper-saline conditions (>50â°). <br><br></div><div>Biomass of seagrass tissue removed from forage-choice assays decreased as environmental
stress increased, showing salinity is a key environmental driver of grazing.
The salinity stress threshold was identified as the marine environment
approached hyper-saline conditions at around 41â°. Here, herbivory pressure decreased
to negligible levels, meaning seagrass community structure was influenced by other
ecosystem processes. With salinity-stress such a predominant feature within
this area it is therefore likely to be a major contributor. Herbivores
preferred the smaller tropical/sub-tropical seagrass species compared to the
larger temperate species that dominate seagrass cover in Shark Bay. This
preference was upheld across the entire salinity-stress gradient and was
correlated with enriched seagrass nitrogen and phosphorous concentrations. <br><br></div><div>Our work supports the modified SGH and presents the first example of this
novel hypothesis predicting herbivory interactions along a salinity-stress
gradient within the marine environment. By demonstrating the fundamental
relationship between trophic interactions and environmental conditions we
underscore the importance of including a suite of abiotic and biotic processes
when studying seagrass dynamics.<br><i><br></i></div><div>Synthesis: The complexity of
interactions within and between biotic and abiotic components of marine systems
plays an uncommonly recognised role in determining the structure and dynamics
of subtidal seagrass environments. We show that the relative importance of
trophic interactions can be a function of environmental conditions, and advance
our understanding of the effectiveness of field approaches in developing
predictive frameworks to determine potential mechanisms of impact on marine
communities.</div
Intergrading reef communities across discrete seaweed habitats in a temperateâtropical transition zone: Lessons for species reshuffling in a warming ocean
Temperate reefs are increasingly affected by the direct and indirect effects of climate change. At many of their warm range edges, cool-water kelps are decreasing, while seaweeds with warm-water affinities are increasing. These habitat-forming species provide different ecological functions, and shifts to warm-affinity seaweeds are expected to modify the structure of associated communities. Predicting the nature of such shifts at the ecosystem level is, however, challenging, as they often occur gradually over large geographical areas. Here, we take advantage of a climatic transition zone, where cool-affinity (kelp) and warm-affinity (Sargassum) seaweed forests occur adjacently under similar environmental conditions, to test whether these seaweed habitats support different associated seaweed, invertebrate, coral, and fish assemblages. We found clear differences in associated seaweed assemblages between habitats characterized by kelp and Sargassum abundance, with kelp having higher biomass and seaweed diversity and more cool-affinity species than Sargassum habitats. The multivariate invertebrate and fish assemblages were not different between habitats, despite a higher diversity of fish species in the Sargassum habitat. No pattern in temperature affinity of the invertebrate or fish assemblages in each habitat was found, and few fish species were exclusive to one habitat or the other. These findings suggest that, as ocean warming continues to replace kelps with Sargassum, the abundance and diversity of associated seaweeds could decrease, whereas fish could increase. Nevertheless, the more tropicalized seaweed habitats may provide a degree of functional redundancy to associated fauna in temperate seaweed habitats
Chapter 6 Biology and Ecology of the Globally Significant Kelp Ecklonia radiata
Ecklonia radiata is one of the most widespread kelps globally, dominating temperate reefs throughout
much of Australasia and southeastern Africa. Throughout much of its range, it is the only laminarian
kelp and hence plays a key role in facilitating biodiversity and driving food webs, and it underpins
immense ecological and socioeconomic values. This review synthesises the growing literature on
E. radiata from its phylogeny and distribution through to its biology, ecology and recent changes. It provides an assessment of the state of knowledge and identifies gaps in our understanding of this
important species. Despite being tolerant of a wide range of abiotic conditions, recent environmental
change has caused direct and indirect loss of E. radiata forests, with extensive areas transitioning to
turf and urchin barrens. Ongoing climate change may require application of multifaceted and novel
strategies to increase its resistance and resilience to future conditions. By integrating variation across
space, time and environmental change, this review provides a description of the current status and
possible future trajectories of E. radiata forests
Chapter 6 Biology and Ecology of the Globally Significant Kelp Ecklonia radiata
Ecklonia radiata is one of the most widespread kelps globally, dominating temperate reefs throughout
much of Australasia and southeastern Africa. Throughout much of its range, it is the only laminarian
kelp and hence plays a key role in facilitating biodiversity and driving food webs, and it underpins
immense ecological and socioeconomic values. This review synthesises the growing literature on
E. radiata from its phylogeny and distribution through to its biology, ecology and recent changes. It provides an assessment of the state of knowledge and identifies gaps in our understanding of this
important species. Despite being tolerant of a wide range of abiotic conditions, recent environmental
change has caused direct and indirect loss of E. radiata forests, with extensive areas transitioning to
turf and urchin barrens. Ongoing climate change may require application of multifaceted and novel
strategies to increase its resistance and resilience to future conditions. By integrating variation across
space, time and environmental change, this review provides a description of the current status and
possible future trajectories of E. radiata forests