Small plastic particles are considered environmental pollutants and are highly concentrated in marine sediments. However, knowledge about plastic abundance within coral reef habitat and beach ...sediments surrounding remote inhabited coral islands is scarce. In this study, microplastic accumulation was investigated on a small inhabited coral island located in the Maldives. Sediments from 22 sampling sites across fore reef, reef flat, and beach environments were analysed for plastic particles <5 mm. Density separation and microscope enumeration revealed a total of 1244 individual microplastic pieces, in filamentous (49%) and fragmented (51%) forms, found across all sampling sites. High concentrations were recorded at all sites, however, there was no significant relationship between microplastic concentration or size across regions (inner atoll and outer atoll) or environments (fore reef, reef flat, and beach). Furthermore, concentrations of microplastic fragment and filament forms, total concentration, and the microplastic community, showed little correlation with sediment particle size. Our findings show microplastics are ubiquitous in marine sediments around a remote coral island, at sizes ingestible by marine organisms, raising concerns about potential effects of microplastic ingestion by coral reef species.
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•Microplastic are ubiquitous around a populated coral island within the Maldives.•Microplastics occur at high concentrations in coastal seafloor sediments.•High potential to negatively impact the health of the ecosystem, marine organisms, and local island communities.
Across many temperate coastlines worldwide, kelp habitat has degraded to be replaced by alternative reef‐states with consequences to ecosystem functioning. Identifying both causes of decline and ...mechanisms of resilience of remnant kelp habitat is critical for managing and restoring these ecosystems.
We use a combination of aerial imagery and field experiments to reveal dynamics of kelp habitat fragmentation during phase‐shift from kelp Ecklonia radiata to overgrazed sea urchin barrens Heliocidaris erythrogramma in Port Phillip bay (Australia).
Analysis of aerial images spanning 6 years (2009–2014) revealed fragmentation of kelp patches to result in increase in perimeter‐to‐area ratio during phase‐shift.
Sea urchin foraging behaviour also changed from the edge to interior of kelp patches, with destructive grazing at the patch edge. Multiple modes of grazing were observed, with greatest rates of kelp bed decline occurring when urchins simultaneously grazed from the ‘outside‐in’ and ‘inside‐out’ of kelp patches. Overgrazing also triggered establishment of invasive kelp Undaria pinnatifida and proliferation of turf algae. Overgrazing reinforced native kelp decline, with overgrazing exacerbated by reduced provision of drift‐kelp.
Synthesis and applications. Perimeter–area ratio of kelp patches can predict phase‐shift, with patch extinction occurring when ratios exceeded a critical ratio of ~0.7. Monitoring dynamics of this critical ratio using aerial imagery provides a novel and cost‐effective indicator of kelp ecosystem resilience for preventing further losses. Targeted culling/harvesting of overgrazing sea urchins along patch edges will enhance native kelp survival and decrease perimeter‐to‐area ratio of remnant kelp patches; reducing risk of phase‐shift to sediment‐trapping turfs and invasive kelp, dually promoting recovery of kelp ecosystems.
Perimeter–area ratio of kelp patches can predict phase‐shift, with patch extinction occurring when ratios exceeded a critical ratio of ~0.7. Monitoring dynamics of this critical ratio using aerial imagery provides a novel and cost‐effective indicator of kelp ecosystem resilience for preventing further losses. Targeted culling/harvesting of overgrazing sea urchins along patch edges will enhance native kelp survival and decrease perimeter‐to‐area ratio of remnant kelp patches, reducing risk of phase‐shift to sediment‐trapping turfs and invasive kelp, dually promoting recovery of kelp ecosystems.
•Stakeholder support is a “missing layer” in restoration suitability models (SMs)•Participatory mapping of support for restoration can address this omission.•SMs found 44–93% of Sydney harbour ...biophysically suitable for native oyster reefs.•Including conflicting uses and stakeholder support cut suitability to 11% then 7%•Failure to consider stakeholder support risks restoration project failure.
Stakeholder support is critical to the success of ecological restoration projects, and consultation with multiple user groups is increasingly a requirement of permitting agencies. Despite this, participatory mapping remains a “missing layer” in spatial planning of restoration projects. We used site selection for oyster reef restoration in Sydney Harbour as a case study to assess how GIS-based habitat suitability modelling might be adapted to consider not only biophysical data and conflicting estuarine use, but also stakeholder support and engagement. Specifically, we compared the outcomes of suitability modelling that; (1) considered only biophysical parameters that influence habitat suitability for native oyster species; (2) included conflicting estuarine uses to negate social conflict, and habitat connectivity to promote ecological synergies; and (3) incorporated stakeholder perspectives through the integration of participatory mapping. Models that only applied biophysical parameters indicated 43–93% (depending on native oyster species) of Sydney Harbour would be more than moderately suitable for native oyster reef restoration. When conflicting estuarine uses and habitat connectivity were included, this value fell to 11% across native oysters. The inclusion of stakeholder perspectives further reduced suitability to 7%. Our study showed that selecting sites for ecological restoration based solely on biophysical suitability for the target species potentially overestimates the area suitable for restoration and therefore increases the probability of project failure, particularly in sites where stakeholders are not as supportive as anticipated. This study demonstrates how traditional habitat suitability modelling can be enhanced through the inclusion of additional data on human activities and stakeholder support. Importantly, it provides a template by which stakeholders can be engaged early in the restoration project planning process and inspire local communities to play a more active role in restoration activities.
There is increasing interest in mitigating the loss of kelp forests through restoration, but this has received scant attention relative to other coastal habitats. We evaluate current knowledge ...centered on key restoration principles to provide guidelines for best practice in kelp restoration. The cause and scale of degradation is fundamental in determining if kelp can be restored and the methods required to promote reestablishment. Removal of stressors may be adequate to achieve restoration goals where degradation is not too widespread or acute. Extensive losses of kelp forests will often require active reseeding of areas because of the low dispersal ability of many kelp species. Restoration efforts have generally taken a trial-and-error approach at experimental scales to develop techniques for establishing individuals. Furthermore, studies that inform cost–benefit analysis and the appropriate spatial scales for restoration of sustainable kelp forests are urgently needed for prioritizing and scaling up restoration efforts globally.
An important, yet overlooked form of anthropogenic pollution is sensory pollution, and one of the most pervasive forms of sensory pollution is artificial light at night (ALAN). Despite the growing ...use of ALAN across the globe, limited research has examined the impacts of ALAN on coral reef fish. This study aims to further our understanding of the behavioural impacts of light pollution on fish by exposing the humbug damselfish (Dascyllus aruanus) to ALAN (∼15–25 lux, white LED light) over a period of 14 days, in situ. We assessed nocturnal activity, and diurnal shelter use and emergence time following a simulated threat in natural (control) and ALAN conditions. D. aruanus colonies exposed to ALAN were active at night and were lacking cryptic colouration observed in control fish, however this altered nocturnal activity did not appear to impact the diurnal behaviours we measured. Our findings provide critical insight into the impact of ALAN exposure to nocturnal behaviour of a diurnal fish and highlight the potential for increased risk of nocturnal predation under ALAN. Further studies with a longer ALAN exposure time will help illuminate the extent of behavioural changes and implications caused by ALAN in shallow coral reef systems.
Over 85% of the world’s oyster reefs have been lost in the past two centuries, triggering a global effort to restore shellfish reef ecosystems and the ecosystem services they provide. While there has ...been considerable success in reestablishing oyster reefs, many challenges remain. These include: high incidence of failed restoration, high cost of restoration per unit area, and increasing stress from climate change, which now imperils many restored reefs. In order to leverage our past successes and progress the field, we must increase restoration efficiencies that not only reduce cost per unit area, but also increase the resilience of restored ecosystems. To address this need, we review the literature associated with the structure and function of oyster reef ecosystems to identify key positive species interactions (i.e. those species interactions where at least one partner benefits and no partners are harmed) that, if systematically incorporated into restoration planning, have the potential to greatly increase restoration outcomes and success. We classified positive inter- and intraspecific feedbacks between oysters and organisms associated with oyster ecosystems into the following seven functional categories: 1) physical reef creation, 2) positive density dependence, 3) refugia from physical stress, 4) refugia from biological stress, 5) biodiversity enhancement, 6) improvement of settlement, and 7) long-distance facilitation. We discuss each category of interaction positive feedback and how restoration practitioners can use knowledge of such processes to alter management and enhance restoration success. We propose that systematic incorporation of positive species interactions that generate these feedbacks into restoration practice may enhance ecological services provided by restored reefs and increase restoration success.
Nutrient input from estuarine producers underpins coastal fisheries production and knowing which producers are the most responsible for fish diet helps effectively protect and restore coastal ...ecosystems. Focussing on the Richmond River in Australia as a case study, we sampled the main estuarine producers and estimated their proportional contributions of nutritional input to seven commercially important fisheries species using Bayesian isotope mixing models. We valued the dietary input of estuarine producers to the commercial fisheries by combining dietary contribution estimates with total annual catch data from commercial fishers. A conservative estimate is that estuarine producers in the Richmond River Estuary contribute at least 82 725 kg (78%) of the total annual catch of the seven commercially important fish with an estimated annual value of $AU 450 117. Sea mullet and Mud crab contributed 95% of the total catch, and 93% of the total value assigned to estuarine producers. The two highest valued estuarine producers were tidal marsh (
Juncus kraussii
) $AU 82 432 and seagrass (
Zostera capricorni
) $AU 65 423. This study demonstrates the substantial role of estuarine producers to commercial fisheries production and the fisheries economy more broadly. With large areas of estuarine producers under threat globally from land clearing for agriculture, aquaculture and urbanisation, the results presented here provide evidence to support the value of coastal habitats and benefits of their preservation and restoration.
Graphic abstract
Marine kelp forests cover 1/3 of our world's coastlines, are heralded as a nature-based solution to address socio-environmental issues, connect hundreds of millions of people with the ocean, and ...support a rich web of biodiversity throughout our oceans. But they are increasingly threatened with some areas reporting over 90% declines in kelp forest cover in living memory. Despite their importance and the threats they face, kelp forests are entirely absent from the international conservation dialogue. No international laws, policies, or targets focus on kelp forests and very few countries consider them in their national policy. The Kelp Forest Challenge addresses that gap. Together with 252 kelp experts, professionals, and citizens from 25 countries, the Kelp Forest Challenge was developed as a grassroots vision of what the world can achieve for kelp forest conservation. It is a global call to restore 1 million and protect 3 million hectares of kelp forests by 2040. This is a monumental challenge, that will require coordination across multiple levels of society and the mobilization of immense resources. Pledges may therefore include area for protection or restoration, enabling pledges which assist in conservation (funding, equipment, professional expertise, capacity building), or awareness-based pledges which increase awareness or education about kelp forests. Correspondingly, participants may be from government, scientific institutions, private sector, NGOs, community groups, or individuals. This challenge is the beginning of a 17-year mission to save our kelp forests and anyone and any organisation is invited to participate.
Cover, both from physical structure or association with social groups, can reduce predation risk and increase foraging, leading to enhanced growth and survival, and is therefore a critical aspect of ...the niche for many organisms. However, the need for cover, or the need for a specific type of cover, may change as an individual grows in size, leading to niche shifts throughout development to meet these changing needs. In this study, we examine ontogenetic shifts in cover use by wild populations of a temperate reef fish, the southern hulafish, Trachinops caudimaculatus, a small, abundant planktivorous social aggregator found on temperate reefs in southern Australia. Through repeated in situ surveys, we found clear evidence of ontogenetic shifts in both microhabitat use and aggregation patterns by T. caudimaculatus juveniles in the first three months on the reef. The microhabitat associations of juvenile T. caudimaculatus became more similar to those of adult conspecifics over the study period, and over the same time frame, juveniles increasingly aggregated with adult shoals. Our findings also suggest that trade‐offs between structural and social cover are context‐dependent, with juveniles relying on structural cover longer when adult conspecific density (and thus intra‐specific competition) and/or habitat complexity (and thus the availability of shelter) is high. These findings provide rare and important observations into the complex interplay of social aggregations, habitat use, and ontogeny in wild fish populations.
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