Tropical reefs have been subjected to a range of anthropogenic pressures such as global climate change, overfishing and eutrophication that have raised questions about the prominence of macroalgae on ...tropical reefs, whether they pose a threat to biodiversity, and how they may influence the function of tropical marine ecosystems.
We synthesise current understanding of the structure and function of tropical macroalgal reefs and how they may support various ecosystem goods and services. We then forecast how key stressors may alter the role of macroalgal reefs in tropical seascapes of the Anthropocene.
High levels of primary productivity from tropical canopy macroalgae, which rivals that of other key producers (e.g., corals and turf algae), can be widely dispersed across tropical seascapes to provide a boost of secondary productivity in a range of biomes that include coral reefs, and support periodic harvests of macroalgal biomass for industrial and agricultural uses. Complex macroalgal reefs that comprise a mixture of canopy and understorey taxa can also provide key habitats for a diverse community of epifauna, as well as juvenile and adult fishes that are the basis for important tropical fisheries.
Key macroalgal taxa (e.g., Sargassum) that form complex macroalgal reefs are likely to be sensitive to future climate change. Increases in maximum sea temperature, in particular, could depress biomass production and/or drive phenological shifts in canopy formation that will affect their capacity to support tropical marine ecosystems.
Macroalgal reefs can support a suite of tropical marine ecosystem functions when embedded within an interconnected mosaic of habitat types. Habitat connectivity is, therefore, essential if we are to maintain tropical marine biodiversity alongside key ecosystem goods and services. Consequently, complex macroalgal reefs should be treated as a key ecological asset in strategies for the conservation and management of diverse tropical seascapes.
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Marine coastal environments are often socially complex public areas that need equitable spatial planning approaches. Understanding the extent of extractive and non-extractive uses and the social ...dynamics that may be driving patterns of use is essential if the spatial plan is to support the social resilience of a marine area. In this study, a combination of fuzzy-set multi-criteria GIS modelling and negative tie social network analysis were used to explore social uses and conflicts based on sketch-mapping interviews with five key stakeholder groups (ecotourism, Aboriginal Traditional Owners, commercial and recreational fishing, and water sports) within a Marine Protected Area (MPA). Most of the areas within the MPA were regularly used by the stakeholders, with non-extractive and extractive stakeholders occupying similar spatial extents, with each stakeholder group having a different pattern of use. However, stakeholder groups had different levels of perceived priority to access these areas and support of the current spatial management plan, especially within the ecotourism and Aboriginal Traditional Owner groups. The investigation of social conflicts in shaping patterns of use revealed that most stakeholder conflicts do not necessarily occur in areas of overlaps, but generally in areas of high biodiversity and easy access through marine infrastructure. Ecotourism groups had the most perceived conflicts over marine space, which shaped their use towards certain no-take zones that protected high biodiversity and would also provide protection from other conflicting stakeholder uses (e.g., boating, fishing). Overall, the method outlined in this paper presents a way for marine spatial management to consider not only the extent and diversity of social uses in a marine environment but also the spatial-social dynamics that may determine the success of the spatial plan in supporting long-term social resilience.
•Marine coastal environments are socially complex and often extensively used.•Spatial conflicts are explored using GIS fuzzy models and social network analysis.•Non-extractive and extractive stakeholders have similar spatial extents and demands.•Social dynamics and conflicts can shape the spatial patterns of uses.•These methods are a way to support social resilience in marine spatial planning.
The ability to sustain high swimming speeds is believed to be an important factor affecting resource acquisition in fishes. While we have gained insights into how fin morphology and motion influences ...swimming performance in coral reef fishes, the role of other traits, such as body shape, remains poorly understood. We explore the ability of two mechanistic models of the causal relationship between body fineness ratio and endurance swimming-performance to predict maximum prolonged-swimming speed (Umax ) among 84 fish species from the Great Barrier Reef, Australia. A drag model, based on semi-empirical data on the drag of rigid, submerged bodies of revolution, was applied to species that employ pectoral-fin propulsion with a rigid body at U max. An alternative model, based on the results of computer simulations of optimal shape in self-propelled undulating bodies, was applied to the species that swim by body-caudal-fin propulsion at Umax . For pectoral-fin swimmers, Umax increased with fineness, and the rate of increase decreased with fineness, as predicted by the drag model. While the mechanistic and statistical models of the relationship between fineness and Umax were very similar, the mechanistic (and statistical) model explained only a small fraction of the variance in Umax . For body-caudal-fin swimmers, we found a non-linear relationship between fineness and Umax , which was largely negative over most of the range of fineness. This pattern fails to support either predictions from the computational models or standard functional interpretations of body shape variation in fishes. Our results suggest that the widespread hypothesis that a more optimal fineness increases endurance-swimming performance via reduced drag should be limited to fishes that swim with rigid bodies.
Translating scientific evidence into practical actions is a primary goal of scientists working to inform evidence‐based policy and decision‐making, but how can authors best facilitate new ...conservation interventions following publication of their research?
This case study used two articles in Aquatic Conservation: Marine and Freshwater Ecosystems (AQC) to examine the mechanisms and barriers to translating published aquatic science into social, ecological and policy interventions for the conservation of threatened Murray crayfish (Euastacus armatus).
These articles revealed how steep declines in Murray crayfish abundance arose from the loss of in‐stream and riparian habitats preferred by crayfish, and demonstrated the social reasons for conserving Murray crayfish to protect the wellbeing of a diversity of people (e.g. Traditional Owners, landholders, ecotourism operators).
Following publication of these articles in AQC the authors used multi‐modal communication (e.g. written briefs, personal discussions, seminars, magazine articles, media broadcasts) to translate their findings to stakeholders and the general public.
Analysis of relevant documents (e.g. management plans, public information leaflets) and stakeholder interviews uncovered a range of interventions arising from the two AQC articles. Social interventions (e.g. new public signage, ecotourism briefings) were the quickest to occur after publication (1–2 years). Although some changes in management were apparent (e.g. revised Murray crayfish action plans, monitoring programmes), systemic barriers (e.g. policy/funding timeframes) have prevented some ecological and policy interventions from being realized.
Diverse communication strategies can help rapidly translate published science into new conservation actions by giving stakeholders the right evidence in the right way to inform their particular practice. Open‐access summaries that explain findings within readily shareable media (e.g. graphical/video s) can be particularly effective in raising early awareness. Some types of intervention, however, may require a long‐term perspective and assistance from boundary‐spanning knowledge brokers with an aptitude for evidence‐based policy development.
Co‐management has been advocated as an effective tool to achieve natural resource conservation worldwide. Yet, the potential of co‐management arrangements can fail to be realized when there is ...insufficient local engagement.
In this perspective paper, we argue that co‐management schemes focusing on culturally important species (CIS) can help overcome this issue by engaging local people's interest.
To develop this theory, we explore published data on the outcomes of two management schemes, both encompassing multiple independent initiatives, to discuss CIS‐management effects and benefits.
We also show a compilation of CIS examples throughout the world and discuss the potential of CIS‐management to reach a global audience.
Based on these data, we argue that CIS‐management can be an effective tool to reconcile the often intractable goals of biodiversity conservation and human welfare.
Translated
O manejo colaborativo (comanejo) tem sido considerado uma ferramenta eficiente para promover a conservação dos recursos naturais em distintas regiões do planeta. No entanto, o potencial dos arranjos de comanejo tende a falhar quando não existe engajamento local suficiente.
Neste artigo, argumentamos que as iniciativas de comanejo com foco em Espécies Culturalmente Importantes (CIS) podem representar uma alternativa para este problema por promover um maior interesse de povos locais nas iniciativas.
Para desenvolver esta ideia, apresentamos e discutimos os efeitos do comanejo de CIS a partir de dados de literatura provenientes de dois esquemas de manejo presentes na Amazônia, ambos com múltiplas iniciativas independentes.
Trazemos, ainda, uma compilação de exemplos de CIS ao redor de todo o mundo e discutimos o potencial do comanejo de CIS de atingir uma audiência global.
Com base nas informações apresentadas no artigo, defendemos que o comanejo de CIS pode ser uma ferramenta efetiva para conciliar a conservação da biodiversidade com o bem‐estar humano.
A free Plain Language Summary can be found within the Supporting Information of this article.
A free Plain Language Summary can be found within the Supporting Information of this article.
Determining the relative influence of biotic and abiotic processes in structuring communities at local to large spatial scales is best understood using a biogeographic comparative‐experimental ...approach. Using this approach, previous work suggests that intertidal community dynamics (top‐down and bottom‐up effects) vary unimodally along an upwelling‐based productivity gradient, termed the Intermittent Upwelling Hypothesis (IUH). Evidence consistent with the IUH comes from the sessile invertebrate/predator (SIP) subweb in certain rocky intertidal communities, but whether this pattern extends to macrophyte/herbivore (MH) subwebs is unknown. Here we ask: Are MH subwebs also structured as predicted by the IUH? What is the relative importance of herbivory and predation in structuring these communities? Under what conditions do ecological subsidies like nutrients or propagule production drive community dynamics? And are omnivorous interactions important? We hypothesize that MH subwebs are driven by a new construct, the Grazing‐Weakening Hypothesis (GWH), which states that MH interactions weaken monotonically with increasing nutrients, with strong (weak) herbivory and low (high) macrophyte productivity at low (high) nutrients. We explored local‐to‐large spatial scale dynamics of both subwebs using a biogeographic comparative‐experimental factorial field experiment testing joint and separate effects of herbivores and predators between two continents. Experiments at 10 sites ranging from persistent upwelling to persistent downwelling regimes ran for 26–29 months in Oregon and California, and New Zealand (NZ) South Island. For the MH subweb, results were consistent with the GWH: herbivory declined and macrophytes increased with increasing nutrients. As expected, results for the SIP subweb were consistent with the IUH: predator effect size was unimodally related to upwelling. Overall, herbivory explained more variation in community structure than did predation, especially in NZ. Omnivory was weak, sessile invertebrates outcompeted macrophytes, and ocean‐driven subsidies provided the basic template driving ecosystem dynamics. We propose a unified meta‐ecosystem dynamics model combining MH and SIP results: with increased upwelling, sessile invertebrates and underlying dynamics vary unimodally (as in the IUH), while herbivory decreases and macrophytes generally increase. While this model was based on research in temperate ecosystems varying in upwelling regime, its wider applicability remains to be tested.
Keystone species can provide a focal point for designing conservation and management strategies that protect a diversity of social–ecological values in aquatic ecosystems; however, to avoid bias ...towards a subset of values associated with a single activity, such as fishing, stakeholder consultations must cover a spectrum of social perspectives.
Using the Murray crayfish (Euastacus armatus) as a model, this study explored how Aboriginal Traditional Owners, landowners, tourism businesses, scientific researchers, non‐governmental organizations, and government agencies valued this threatened freshwater species across south‐east Australia.
Qualitative methods revealed that E. armatus is a culturally significant species, targeted for fishing, but is also valued for a range of non‐extractive reasons that support social–ecological linkages between people and freshwater ecosystems.
Perceived as an iconic species by most stakeholders, there was general support for E. armatus to be used as a flagship for conserving a spectrum of social–ecological values (e.g. Aboriginal Traditional Owner totem species), attached to their local freshwater ecosystems. Although stakeholders were conflicted over whether fishing should continue, four themes emerged on how to develop more equitable and effective conservation and management strategies: increased public education, co‐management with non‐government stakeholders, federal government co‐ordination, and spatial protection of critical areas.
The protection of aquatic species in ways that support their full range of cultural, economic, and ecological values will require more bottom‐up (i.e. stakeholder‐led) approaches to conservation and management design. Broader stakeholder engagement and co‐management should reduce perceptions that local stakeholders are isolated from management processes, while increasing the capacity and confidence of managers to implement strategies that bolster both the social and ecological resilience of aquatic ecosystems.
Environmental drivers of seaweed biomass were investigated at Ningaloo, Western Australia, a coral reef ecosystem with negligible anthropogenic influences on seaweeds from fishing, farming, or ...eutrophication. Periodic surveys of benthic macroalgae occupying seaweed-dominated beds within the lagoon at two locations (Coral Bay, Tantabiddi) were made during winter, spring, and late summer over a 26 month period. Canopy-forming Sargassum spp. biomass fluctuated over a seasonal growth–decay cycle, with highest values in the warm summer months (up to 1013 g fresh weight 0.25 m−2 at Coral Bay) and lowest values in winter (down to 155 g fresh weight 0.25 m−2 at Tantabiddi). Conversely, prominent understory seaweed genera Dictyopteris and Lobophora reached peak biomass in winter, when the Sargassum spp. canopy was lowest. Sargassum spp. biomass variation could be attributed largely to time (52%), location (21%), and site (26%), with low variation within individual seaweed beds (1%). Statistical analysis of the influence of five environmental variables (temperature, light, wind-driven upwelling, rainfall, significant wave height) indicated that location and sea temperature (1 month antecedent to biomass) provided the best explanation for Sargassum spp. biomass fluctuations. While sea temperature is a key driver of seaweed temporal dynamics, heterogeneity at the kilometer scale suggests that spatial context is also important. Given the important role of seaweeds in many ecosystem processes, this strong biophysical coupling between Sargassum spp. biomass and sea temperature suggests that thermal climate change will significantly affect coral reef productivity and biodiversity.
An ecological release from competition or predation is a frequent adaptive explanation for the colonization of novel environments, but empirical data are limited. On the island of Rarotonga, several ...blenny fish species appear to be in the process of colonizing land. Anecdotal observations have implied that aquatic predation is an important factor in prompting such amphibious fish behavior. We provide evidence supporting this hypothesis by demonstrating that amphibious blennies shift their abundance up and down the shoreline to remain above predatory fishes that periodically move into intertidal areas during high tide. A predation experiment using blenny mimics confirmed a high risk of aquatic predation for blennies, significantly higher than predation experienced on land. These data suggest that predation has played an active role in promoting terrestrial activity in amphibious blennies and provide a rare example of how ecological release from predation could drive the colonization of a novel environment.
Canopy‐forming macroalgae can construct extensive meadow habitats in tropical seascapes occupied by fishes that span a diversity of taxa, life‐history stages and ecological roles. Our synthesis ...assessed whether these tropical macroalgal habitats have unique fish assemblages, provide fish nurseries and support local fisheries. We also applied a meta‐analysis of independent surveys across 23 tropical reef locations in 11 countries to examine how macroalgal canopy condition is related to the abundance of macroalgal‐associated fishes. Over 627 fish species were documented in tropical macroalgal meadows, with 218 of these taxa exhibiting higher local abundance within this habitat (cf. nearby coral reef) during at least one life‐history stage. Major overlap (40%–43%) in local fish species richness among macroalgal and seagrass or coral reef habitats suggest macroalgal meadows may provide an important habitat refuge. Moreover, the prominence of juvenile fishes suggests macroalgal meadows facilitate the triphasic life cycle of many fishes occupying diverse tropical seascapes. Correlations between macroalgal canopy structure and juvenile abundance suggests macroalgal habitat condition can influence levels of replenishment in tropical fish populations, including the majority of macroalgal‐associated fishes that are targeted by commercial, subsistence or recreational fisheries. While many macroalgal‐associated fishery species are of minor commercial value, their local importance for food and livelihood security can be substantial (e.g. up to 60% of landings in Kenyan reef fisheries). Given that macroalgal canopy condition can vary substantially with sea temperature, there is a high likelihood that climate change will impact macroalgal‐associated fish and fisheries.
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