A global horizon scan of issues impacting marine and coastal biodiversity conservation

The biodiversity of marine and coastal habitats is experiencing unprecedented change. While there are well-known drivers of these changes, such as overexploitation, climate change and pollution, there are also relatively unknown emerging issues that are poorly understood or recognized that have potentially positive or negative impacts on marine and coastal ecosystems. In this inaugural Marine and Coastal Horizon Scan, we brought together 30 scientists, policymakers and practitioners with transdisciplinary expertise in marine and coastal systems to identify new issues that are likely to have a significant impact on the functioning and conservation of marine and coastal biodiversity over the next 5–10 years. Based on a modified Delphi voting process, the final 15 issues presented were distilled from a list of 75 submitted by participants at the start of the process. These issues are grouped into three categories: ecosystem impacts, for example the impact of wildfires and the effect of poleward migration on equatorial biodiversity; resource exploitation, including an increase in the trade of fish swim bladders and increased exploitation of marine collagens; and new technologies, such as soft robotics and new biodegradable products. Our early identification of these issues and their potential impacts on marine and coastal biodiversity will support scientists, conservationists, resource managers and policymakers to address the challenges facing marine ecosystems

Predators and distance between habitat patches modify gap crossing behaviour of juvenile Atlantic cod (Gadus morhua, L. 1758)

When habitat refugia is fragmented and limited, movement of potential prey animals between patches of protective habitat may be driven by biotic factors including foraging opportunities, risk of predation mortality, as well as density effects. However, few studies have examined these factors in marine landscapes. We examined gap crossing behaviour of juvenile Atlantic cod, Gadus morhua L. 1758, a species with high mortality throughout its juvenile stage. We examined the effect of inter-patch distance, fish length, group size, and the presence of a predator on gap crossing behaviour by juvenile cod in a 12 × 3 m experimental arena. Habitat patches consisting of artificial eelgrass were positioned within the arena with inter-patch distances of 3.0 m and 7.5 m. We observed a 37% reduction in frequency of gap crossing movements at larger distances compared to small ones. At the greater inter-patch distance, fish delayed departing a patch, depending on average group size. Juvenile fish released into a patch with a nearby predator moved across gaps 75% less frequently than fish originating in a predator-free patch. We also found that the presence of a predator delayed fish departure from a patch, again depending on group size. Our study demonstrates a suite of complex behavioural mechanisms that juvenile cod may exhibit to reduce predation risk as they navigate a landscape of fragmented habitat patches

Biodiversity links above and below the marine sediment-water interface that may influence community stability

Linkages across the sediment-water interface (SWI) between biodiversity and community stability appear to exist but are very poorly studied. Processes by which changes in biodiversity could affect stability on the other side of the SWI include carbon transfer during feeding, decomposition of organic matter, nutrient recycling, organism recruitment and structural stabilisation of sediments. The importance of these processes will clearly vary among habitats. Direct disturbance to communities on one side of the SWI, such as created by overfishing, habitat destruction, and species invasions, has the potential to impact communities on the other side of the SWI through the many functional links. Hypotheses are proposed to suggest further areas of research to fill the large gaps in our knowledge concerning the nature and intensity of such linkages. The linkage between benthic and pelagic diversity is likely to be tighter where there is a close energetic connection between the domains, such as polar and shallow coastal waters, and where communities are dominated by selective detritivores. The quantity of carbon reserves in the sediment and the predominant mode of larval development of sediment communities probably influence the stability of below SWI communities in the face of changes in above SWI diversity. The organisms, including hyperbenthos, that are found at the SWI may be of crucial importance to the linkage and stability of above and below SWI communities. [KEYWORDS: benthos, biodiversity, fish, links, pelagic, plankton, sediment-water interface, stability]