Coastal systems are among the most studied, most vulnerable, and economically most important ecosystems on Earth; nevertheless, little attention has been paid, so far, to the consequences of human activities on the shallow sea-floor of these environments. Here, we present a quantitative assessment of the effects of human actions on the floor of the tidal channels from the Venice Lagoon using 2500 kilometres of full coverage multibeam bathymetric mapping. Such extended dataset provides unprecedented evidence of pervasive human impacts, which extend far beyond the well known shrinking of salt marshes and artificial modifications of inlet geometries. Direct and indirect human imprints include dredging marks and fast-growing scours around anthropogenic structures built to protect the historical city of Venice from flooding. In addition, we document multiple effects of ship traffic (propeller-wash erosion, keel ploughing) and diffuse littering on the sea-floor. Particularly relevant, in view of the ongoing interventions on the lagoon morphology, is the evidence of the rapid morphological changes affecting the sea-floor and threatening the stability of anthropogenic structures.
Human Impacts on the Environment
Sustainable development of the ocean is a central policy objective in Europe through the Blue Growth Strategy and globally through parties to the Convention on Biological Diversity. Achieving sustainable exploitation of deep sea resources is challenged due to the huge uncertainty around the many risks posed by human activities on these remote ecosystems and the goods and services they provide. We used a Delphi approach, an iterative expert-based survey process, to assess risks to ecosystem services in the North Atlantic Ocean from climate change (water temperature and ocean acidification), the blue economy (fishing, pollution, oil and gas activities, deep seabed mining, maritime and coastal tourism and blue biotechnology), and their cumulative effects. Ecosystem services from the deep sea, identified through the Millennium Ecosystem Assessment framework, were presented in an expert survey to assess the impacts of human drivers on these services. The results from this initial survey were analyzed and then presented in a second survey. The final results, based on 55 expert responses, indicated that pollution and temperature change each pose a high risk to more than 28% of deep-sea ecosystem services, whilst ocean acidification, and fisheries both pose a high risk to more than 19% of the deep-sea ecosystem services. Services considered to be most at risk of being impacted by anthropogenic activities were biodiversity and habitat as supporting services, biodiversity as a cultural service, and fish and shellfish as provisioning services. Tourism and blue biotechnology were not seen to cause serious risk to any of the ecosystem services. The negative impacts from temperature change, ocean acidification, fishing, pollution, and oil and gas activities were deemed to be largely more probable than their positive impacts. These results expand our knowledge of how a broad set of deep-sea ecosystem services are impacted by human activities. Furthermore, the study provides input in relation to future priorities regarding research in the Atlantic deep sea.
Vulnerable Marine Ecosystems (VMEs) are characterized by prominent biological features susceptible to anthropogenic disturbances. Following international guidelines, the identification and protection of VMEs require a detailed documentation regarding both the community structure and the fishing footprintin the area. This combined information is lacking for the majority of the Mediterranean mesophotic rocky reefs that, similarly to deep-seabottoms, are known to host valuable animal forests.
A deep coralligenous site exploited by artisanal fishermen in the NW Mediterranean Sea is here used as a model to assess the vulnerability of animal forests at mesophotic depths and evaluate the sustainability of artisanal fishing practices, particularly lobster trammel net. The Remotely Operated Vehicle (ROV) footage is used to document the biodiversity and health status of the megabenthic communities, while discard data are employed to quantify the entanglement risk, discard rates of fragile species and threats to sea floor integrity.
A multidisciplinary approach is proposed for the assessment of the vulnerability criteria of an EU Special Area of Conservation, leading to specific managementmeasures, including the delineation of fishing restrictions.
Shoreline discharge representing approximately 80% of sewage generated by Sydney (Australia) was replaced with three deepwater ocean outfalls between 1990 and 1991. Beachwatch bacterial monitoring data collected between 1989 and 2016 were analysed to assess the impact of commissioning on bathing water quality along 32 km of coastline. Bacterial contamination was reduced by 26–99% during the first 32 months post-commissioning and in the longer post-commissioning period, 1993 to 2016, bathing water quality improved for 31 beaches. Relatively stable bathing water quality was observed for five other beaches after the 2001 upgrade of another shoreline wastewater treatment plant. Bacterial contamination of bathing water in this 24-year post-commissioning period was most influenced by rainfall in the 24-h to 9 am on the day of sampling. Bacterial contamination from surfacing shore-blown wastewater plumes was not evident, whereas stormwater-delivered bacterial contamination was apparent and varied between beaches.
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 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.