Climate change and human disturbance threatens coral reefs across the Pacific, yet there is little consensus on what characterizes a “healthy” reef. Benthic cover, particularly low coral cover and high macroalgae cover, are often used as an indicator of reef degradation, despite uncertainty about the typical algal community compositions associated with either near-pristine or damaged reefs. In this study, we examine differences in coral and algal community compositions and their response to human disturbance and past heat stress, by analysing 25 sites along a gradient of human disturbance in Majuro and Arno Atolls of the Republic of the Marshall Islands. Our results show that total macroalgae cover indicators of reef degradation may mask the influence of local human disturbance, with different taxa responding to disturbance differently. Identifying macroalgae to a lower taxonomic level (e.g. the genus level) is critical for a more accurate measure of Pacific coral reef health.
Human Impacts on the Environment
Human population density within 100 km of the sea is approximately three times higher than the global average. People in this zone are concentrated in coastal cities that are hubs for transport and trade – which transform the marine environment. Here, we review the impacts of three interacting drivers of marine urbanization (resource exploitation, pollution pathways and ocean sprawl) and discuss key characteristics that are symptomatic of urban marine ecosystems. Current evidence suggests these systems comprise spatially heterogeneous mosaics with respect to artificial structures, pollutants and community composition, while also undergoing biotic homogenization over time. Urban marine ecosystem dynamics are often influenced by several commonly observed patterns and processes, including the loss of foundation species, changes in biodiversity and productivity, and the establishment of novel assemblages, ruderal species and synanthropes. Further, we discuss potential urban acclimatization and adaptation among marine taxa, interactive effects of climate change and marine urbanization, and ecological engineering strategies for enhancing urban marine ecosystems. By assimilating research findings across disparate disciplines, we aim to build the groundwork for urban marine ecology – a nascent field; we also discuss research challenges and future directions for this new field as it advances and matures. Ultimately, all sides of coastal city design: architecture, urban planning, and civil and municipal engineering, will need to prioritize the marine environment if negative effects of urbanization are to be minimized. In particular, planning strategies that account for the interactive effects of urban drivers and accommodate complex system dynamics could enhance the ecological and human functions of future urban marine ecosystems.
Ocean resources have been exploited at unprecedented rates, leading to marine biodiversity loss, food web changes, and other alterations of ocean ecosystem functions and structures. The capture of wild fish for human consumption and fishmeal are the primary drivers. Microalgae oil has long been investigated for biofuel production. Its co-product, defatted microalgal biomass, has potential to replace fishmeal from wild fish catch and thus mitigate ocean resource depletion.
This study develops a new indicator for assessing consequential impacts on ocean resources in life cycle assessment. The indicator is based on primary production required, a concept previously used in ecological assessments and life cycle assessments to evaluate ecological impacts of fisheries and aquaculture. We estimate the primary production required for fishmeal production from the ocean (166 kg carbon/kg fishmeal), and the potential of defatted microalgae biomass displacing fishmeal. Results show that defatted microalgae biomass can lead to highly variable, but potentially significant, reductions in ocean resource demand. The variability is a function of the potential for replacement, which depends on the cultured fish species considered. As an example of this significance, based on available data for estimating the potential for defatted microalgal biomass to displace fishmeal for cultured tilapia, salmon, shrimp, carp, flounder, yellowtail and cod, by 2020 net primary production demand from the ocean could be reduced by approximately one billion tons of carbon.
Scientists, industry and regulators are seeking to understand the influence of oil and gas infrastructure in our oceans to mitigate its impacts and maximise environmental benefits. This project equipped a standard work-class ROV with a light-weight stereo-video camera system to collect high definition imagery of fish and habitats formed by marine growth associated with Woodside Energy's Goodwyn Alpha Platform jacket (GWA) 138 km offshore of Dampier, north-west Australia. ROV video surveys were rapidly performed by industry on four faces of the GWA jacket, from the surface to the seabed at 130 m, yielding 1 h and 14 min of imagery. The stereo-video cameras continued to film during standard ROV operations collecting a further 150 h of HD imagery, used to build a comprehensive fish species list. A total of 8676 individual fish from at least 57 species and 20 families, with an estimated combined mass of 8719 kg, were recorded from the vertical transects of four faces of the jacket. An additional 43 fish species from 21 families were recorded via rapid assessment of a subset of the additional, standard ROV operations imagery. The jacket was characterised by abundant Caranx sexfasciatus (bigeye trevally), Pseudanthias spp. (basslets), Heniochus diphreutes(schooling bannerfish), Labridae sp. (wrasse) and Acanthurus spp. (surgeonfish). Several fish important to the demersal scalefish fishery in the region were observed, including: Lutjanus argentimaculatus (mangrove jack), Lutjanus erythropterus(crimson snapper), Lutjanus malabaricus (saddletail snapper), Lutjanus russellii(Moses' snapper). Eleven broad marine growth types were observed with encrusting/enveloping species (brown algae, filamentous mat, coralline algae, calcite) and hard corals (Tubastrea sp.) present in the greatest coverage. Both marine growth and fish assemblages changed markedly with depth. The addition of a lightweight stereo-video system to an industrial ROV and the allocation of short amounts of time for rapid vertical surveys provided important information on the ecology of an oil and gas platform jacket. Future industrial ROV campaigns should consider utilising this approach to gather scientific information that may have value in the context of decommissioning comparative assessments and, more generally, improves our understanding of the impact of oil and gas infrastructure in our oceans.
Detecting the effects of introduced artificial structures on the marine environment relies upon research and monitoring programs that can provide baseline data and the necessary statistical power to detect biological and/or ecological change over relevant spatial and temporal scales. Here we report on, and assess the use of, Baited Remote Underwater Video (BRUV) systems as a technique to monitor diversity, abundance and assemblage composition data to evaluate the effects of marine renewable energy infrastructure on mobile epi-benthic species. The results from our five-year study at a wave energy development facility demonstrate how annual natural variation (time) and survey design (spatial scale and power) are important factors in the ability to robustly detect change in common ecological metrics of benthic and bentho-pelagic ecosystems of the northeast Atlantic. BRUV systems demonstrate their capacity for use in temperate, high energy marine environments, but also how weather, logistical and technical issues require increased sampling effort to ensure statistical power to detect relevant change is achieved. These factors require consideration within environmental impact assessments if such survey methods are to identify and contribute towards the management of potential positive or negative effects on benthic systems.
The resilience and recovery dynamics of deep-sea habitats impacted by bottom trawling are poorly known. This paper reports on a fishing impact recovery comparison based on four towed camera surveys over a 15-year period (2001–2015) on a group of small seamounts on the Chatham Rise, east of New Zealand, on which pre-disturbance benthic communities are dominated by thicket-forming scleractinian corals. The six seamounts studied encompass a range of trawl histories, including one with high and persistent levels of trawling throughout the survey period, two with intermittent and intermediate levels of trawling, two which were low/untrawled, and one, ‘Morgue’, which was closed to trawling in 2001, having been heavily trawled up to that point. Still photographs from all surveys were analyzed for the identification and abundance of all visible benthic fauna with effort made to ensure consistency of data among surveys. Because increases in image resolution and quality over time resulted in a persistent trend of increasing abundances, analyses were concentrated on comparisons among seamounts within surveys and how these relationships changed with time. The abundance, species richness, and diversity of benthic communities were higher on low/untrawled seamounts than on those that had been trawled. Multivariate community structure showed similar patterns at each survey point, the low/untrawled seamounts being strongly dissimilar to the persistently trawled seamount, with the others ranged between these extremes, broadly in accordance with their cumulative trawl histories. Community structure on the persistently trawled seamount was less variable than on the other seamounts throughout the study period, possibly because of regular ‘re-setting’ of the community by disturbance from trawling. Although there was some variability in results between whole seamount and summit sector analyses, in general communities on Morgue remained similar to those on the persistently trawled seamount, showing little indication of steps toward recovery to its pre-disturbance state following its closure. These results indicate low resilience of benthic communities on the seamounts to the effects of bottom trawling.
The Juan Fernández Ridge (JFRE) is a vulnerable marine ecosystem (VME) located off the coast of central Chile formed by the Juan Fernández Archipelago and a group of seamounts. This ecosystem has unique biological and oceanographic features, characterized by: small geographical units, high degree of endemism with a high degree of connectivity within the system. Two fleets have historically operated in this system: a long term coastal artisanal fishery associated with the Islands, focused mainly on lobster, and a mainland based industrial demersal finfish fishery operating on the seamounts which is currently considered overexploited. The management of these fisheries has been based on a classical single-species approach to determine output controls (industrial fleet) and a mixed management system with formal and informal components (artisanal fleet). There has been growing interest in increasing the exploitation of fisheries, and modernization of the fishing fleet already operating in the JFRE. Under this scenario of increased levels of fishing exploitation and the high level of interrelation of species it might be necessary to understand the impact of these fisheries from a holistic perspective based on a ecosystem-based modeling approach. To address these challenges we developed an Atlantis end-to-end model was configured for this ecosystem. The implemented model has a high degree of skill in representing the observed trends and fluctuations of the JFRE. The model shows that the industrial fishing has a localized impact and the artisanal fisheries have a relatively low impact on the ecosystem, mainly via the lobster fishery. The model indicates that the depletion of large sized lobster has leads to an increase in the population of sea urchins. Although this increase is not sufficient, as yet, to cause substantial flow-on effects to other groups, caution is advised in case extra pressure leads the ecosystem towards a regime shift.
Reef sharks are vulnerable predators experiencing severe population declines mainly due to overexploitation. However, beyond direct exploitation, human activities can produce indirect or sub-lethal effects such as behavioral alterations. Such alterations are well known for terrestrial fauna but poorly documented for marine species. Using an extensive sampling of 367 stereo baited underwater videos systems, we show modifications in grey reef shark (Carcharhinus amblyrhynchos) occurrence and feeding behavior along a marked gradient of isolation from humans across the New Caledonian archipelago (South-Western Pacific). The probability of occurrence decreased by 68.9% between wilderness areas (more than 25 hours travel time from the capital city) and impacted areas while the few individuals occurring in impacted areas exhibited cautious behavior. We also show that only large no-entry reserves (above 150 km²) can protect the behavior of grey reef sharks found in the wilderness. Influencing the fitness, human linked behavioral alterations should be taken into account for management strategies to ensure the persistence of populations.
Coastal cities continue to experience rapid urbanisation and population growth worldwide, linked to the diverse economic and social benefits flowing from proximity to the sea. Growing concern over human impacts upon coastal waters and global strategic goals for healthier cities requires that coastal cities develop innovative ways to inspire and empower communities to embrace and cherish city seascapes. Coastal city communities have much to gain from a healthier relationship with the sea. This paper proposes a collaborative community-led marine park concept that celebrates a city's connection to the marine environment, enhances sustainable economic prosperity and enables communities to participate in activities that deepen understanding, value, care and enjoyment of the city seascape. A city marine park (CMP) is not a marine protected area because it does not have biodiversity and heritage protection or ecosystem governance as a primary goal and does not aim to restrict human activities. A CMP enables city communities to collaborate towards a shared vision of elevated status and value for the city seascape. A CMP considers socio-economic and geographical context, including land-sea connectivity, and is integrated within a coastal city's strategic urban planning. This paper highlights core themes of a CMP and the diverse and wide-ranging benefits from coordinated activities that better connect the city community with its seascape. If co-created by the coastal city community and civic leaders, a CMP will form an enduring spatial nexus for progress toward healthy cities addressing multiple interlinked global sustainable development goals.
Determining what abiotic and biotic factors affect the diversity and abundance of species through time and space is a basic goal of ecology and an integral step in predicting current and future distributions. Given the pervasive effect of humans worldwide, including anthropogenic factors when quantifying community dynamics is needed to understand discrete and emergent effects of humans on marine ecosystems, especially systems with economically important species. However, there are limited studies that combine a large-scale ecological survey with multiple natural and anthropogenic factors to determine the drivers of community dynamics of temperate reef systems. We combined data from a 24-year fish survey on temperate reefs along the Southeast United States coast with information on recreational and commercial fisheries landings, surface and bottom temperature, habitat characteristics, and climate indices to determine what factors may alter the community structure of fishes within this large marine ecosystem. We found that both abundance and richness of temperate reef fishes declined from 1990 to 2013. Climate indices and local temperature explained the greatest variation, and recreational fishing explained slightly more variation compared to commercial fishing in the temperate reef fish community over a multi-decadal scale. When including habitat characteristics in a 3 year analysis, depth, and local temperature explained the greatest variation in fish assemblage, while the influence of habitat was comparatively minimal. Finally, the interaction between predictor variables and fish traits indicated that bigger and longer-lived fishes were positively correlated with depth and winter temperature. Our findings suggest that lesser-studied anthropogenic impacts, such as recreational fishing, may influence communities throughout large ecosystems as much as other well-studied impacts such as climate change and commercial fishing. In addition, climate indices should be considered when assessing changes, natural or anthropogenic, to fish communities.