Location and physical characteristics
Figure 1: East Shetland Shelf Offshore Marine Region. The thicker white line delineates the extent of the East Shetland Shelf OMR. For a map of all SMRs and OMRs, see Figure 5 here
| Sea area (km2): | 33,713 |
| Deepest point (m): | 175 |
| Shallowest point (m) | 58 |
| Average depth (m) | 128 |
| Tides (m) | 1.0 – 1.6 |
| Salinity | 34.05 – 35.31 |
| Sea surface temperature (°C) | 7.2 – 14.3 |
The East Shetland Shelf OMR is located in the northern North Sea, to the east of Shetland, having a boundary with the Shetland Isles SMR (Figure 1). The average water depth is 128 m. Due to the characteristics of the tides in the North Sea, the East Shetland OMR has a relatively small tidal range. The residual southward flow is into the North Sea via the East Shetland Atlantic Inflow (see Circulation Assessment). In summer, deeper regions of the East Shetland OMR stratify (see Stratification Assessment) as heat input into surface layers is not mixed fully through the water column, and a surface warm layer is separated from the deeper (relatively cooler) water. Where there is a transition from the stratified to mixed water column, frontal jets occur at these density fronts. In autumn and winter conditions, the prevailing wind direction can lead to a large swell.
The area comprises a combination of stony and bedrock reef, coarse and sandy sediments. There is also a series of crater-like depressions or pockmarks of the seafloor, some qualifying as the Annex I habitat ‘Submarine structures made by leaking gases’. Large blocks, pavements slabs and smaller fragments of methane-derived authigenic carbonate (MDAC) have been deposited through the process of precipitation during the anaerobic oxidation of methane (AOM) by a specialised community of microbial organisms. The AOM activity at the sulphate-methane interface beneath the seabed results in the presence of poisonous hydrogen sulphide in the sediments.
Productive
The Productive Assessment was undertaken on a sectoral basis with a focus on 2014 - 2018. For fishing, oil and gas and subsea cables, there were changes over the period 2014 – 2018 (Figure 2).
The East Shetland Shelf OMR contributes significantly to the Oil and Gas industry, being one of three OMRs producing between 20 and 26 million tonnes of oil equivalents in 2018 (see Oil and Gas Assessment). There are also significant demersal fish landings from the International Council for the Exploration of the Sea (ICES) statistical rectangles from within the East Shetland Shelf OMR. Some delivered over 2,000 tonnes of demersal fish in 2018, while others resulted in landings of between 1,000 and 2,000 tonnes (see Fisheries Assessment). There is also a draft plan option from 2019 for a windfarm within the East Shetland Shelf OMR.
Figure 2: Changes that have taken place in the East Shetland Shelf OMR by Sector. Although the period 2014 – 2018 inclusive has been used where possible, there are some entries when a slightly different time period has been used.
Pressures from human activities
As part of SMA 2020, an assessment of the main pressures from human activities in each of the SMRs and OMRs was undertaken through a MASTS-led workshop. The process and outcomes are presented in detail in the Pressure from Activities section. Five main pressures identified for the East Shetland Shelf OMR ordered as per the MASTS-led Pressure Assessment Workshop were:
| Priority [1] | Pressure (FeAST classification) [2] | Main healthy and biologically diverse components affected [3] | Main contributing FeAST activity /activities to pressure [4] | Associated productive assessments [5] |
|---|---|---|---|---|
| 1 | Surface abrasion |
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| 2 | Sub-surface abrasion/penetration |
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| 3 | Removal of target species (including lethal) |
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| 4 | Removal of non-target species (including lethal) |
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| 5 | Litter |
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Clean and safe
The assessments cover hazardous substances and marine litter which have the potential to impact on habitats and species as well as being a consequence of human activity. Although sources of litter or contaminants may be local, there are cases when the source is some distance from the impacted area. The main findings for the East Shetland Shelf OMR are:
Hazardous substances
Hazardous substances (polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and heavy metals (Hg, Cd and Pb)) assessments in sediment and biota (fish and shellfish) were undertaken at the scale of the five Scottish biogeographic regions: Atlantic North-West Approaches, Irish Sea (Clyde and Solway), Minches and Western Scotland, Scottish Continental Shelf and Northern North Sea. East Shetland OMR is in the Northern North Sea biogeographic region. Contaminant concentrations in the Northern North Sea biogeographic region were generally above background levels but below concentrations where adverse effects could occur. In addition, concentrations in sediment and biota were stable or declining for all hazardous substances measured. There is one sediment site in East Shetland Shelf, OMR this site was typical of the Northern North Sea, biogeographic region with no major concerns.
A number of biological effects were also measured and assessments undertaken at the scale of the four Scottish biogeographic regions. The contaminant specific biological effects (PAH bile metabolites and 7- ethoxyresorufin O-deethylase (EROD) activity) in the Northern North Sea biogeographic region were consistent with the hazardous substances and showed a limited exposure to contaminants. The Northern North Sea biogeographic region showed an increase in fish disease in some years but this could not be linked to exposure to contaminants. There were no fish sites assessed for biological effects in the East Shetland Shelf OMR.
Marine litter
Due to the lack of assessment criteria for marine litter and microplastic, status assessments were not possible. However, litter and microplastics are present in all sampled OMRs, including the East Shetland Shelf OMR. East Shetland Shelf OMR has a relatively low concentration of microplastics in surface water (< 5,000 microplastics per km2 of sea surface), at 8 of the 10 sites sampled.
Seafloor litter was assessed at the scale of the biogeographic regions; East Shetland Shelf OMR is included in the Northern North Sea biogeographic region. The evidence indicates that there is no consistent trend in seafloor litter.
Healthy and biologically diverse
This section summarises the information from the Marine Protected Areas (MPAs) and intertidal and continental shelf habitats assessments from SMA2020. It also provides information from the relevant case studies relating to Priority Marine Features (PMFs), with a focus on habitats. Further work is required to enable assessment at a SMR/OMR scale for most species; this will be included in Scotland’s next marine assessment.
At a SMR/OMR scale for MPAs the focus is on the number of new MPAs, MPAs with new spatial management measures, and MPAs in which spatial management measures are in discussion, as well as recognising monitoring that has been undertaken between 2012-2018. For the marine habitats, the focus is on interpreting the relevant intertidal and continental shelf habitat assessments – biogenic habitats, predicted extent of physical disturbance to the seafloor (BH3) and intertidal seagrass beds. For PMFs, a summary is provided of the changes in our understanding of the habitats of most relevance to the East Shetland Shelf OMR, including changes in distribution and extent.
Marine Protected Areas
At a regional scale for MPAs the focus is on the number of new MPAs, MPAs with new spatial management measures, and MPAs in which spatial management measures are in discussion, as well as recognising monitoring that has been undertaken between 2012-2018.
Progress in developing the Scottish MPA network
There are 2 MPAs in the East Shetland Shelf OMR that contribute to the Scottish MPA network (Table 1). Some of these MPAs overlap completely or partially in terms of their spatial coverage and/or the features (habitats, species, etc.) they were set up to help conserve. They are counted as separate MPAs because they have been established under different legislation which influences the way in which they are managed. Also note that there are MPAs that straddle the boundaries between different SMRs/OMRs or in some cases overlap each other. Where this is the case, these MPAs have been counted as contributing to the MPA network in all of the SMRs/OMRs in which they are present. This means that the total number of MPAs in Scotland cannot be calculated through combining the SMR/OMR totals. Please see the Marine Protected Area assessment which contains statistics for the Scottish MPA network as a whole.
Table 1. Numbers of types of MPAs in the East Shetland Shelf OMR that contribute to the Scottish MPA network, including the number of new MPAs introduced since 2012.
|
Type of MPA |
Abbr. |
Total no. of MPAs
|
No. of new MPAs 2012-2018 |
|
Special Area of Conservation |
SAC |
2 |
1 |
Progress in Managing MPAs
The progress in implementing management measures for MPAs is summarised in Table 2. This includes information on where spatial management measures are in place and where they are under discussion. It also includes information on the number of MPAs that have been monitored by statutory bodies.
Table 2. Summary of progress in managing Marine Protected Areas in the East Shetland Shelf OMR .
|
Type of MPA |
No. of MPAs with spatial measures in place pre-2012 |
No. of MPAs with new spatial measures in place 2012-2018 |
No. of MPAs with spatial measures under discussion 2012-2018 |
No. of MPAs monitored by statutory bodies 2012-2018 |
No. of MPAs monitored by citizen scientists 2012-2018 |
|
Special Area of Conservation |
0 |
0 |
2 |
1 |
0 |
For both sites (Braemar Pockmarks SAC and Pobie Bank Reef SAC), progress is ongoing for these sites with fisheries management options being developed.
Progress in Monitoring MPAs
Information on the evidence base used to characterise the offshore MPAs in the East Shetland Shelf OMR and any subsequent monitoring is given in the Site Information Centre web page ( https://jncc.gov.uk/our-work/offshore-mpas/ ) for the following MPAs:
- Braemar Pockmarks SAC,
- Pobie Bank Reef SAC.
For links to the MPA Surveys and monitoring reports for Pobie Bank Reef SAC, see MPA Monitoring Survey Reports | JNCC - Adviser to Government on Nature Conservation
Priority Marine Features
The assessments focus on individual/ grouped habitats and species with a number of case studies reflecting more detailed research and monitoring as outlined in ‘What is assessed’. A key component of an OMR is the number and type of Priority Marine Features (PMFs) present in the region and the associated protected areas. In addition, there is concern about invasive non-native species and the impact that they are having in any particular region. With respect to these three aspects, the principal findings of SMA 2020 that are most relevant to the East Shetland Shelf OMR are summarised below.
Number of Priority Marine Features and birds (non-PMF) recorded
The East Shetland Shelf OMR is the location for a range of as detailed in Table 3.
Table 3: Details of PMFs, seabirds, and wintering waterbirds found in the East Shetland OMR
|
PMFs – grouped habitats and species |
No. of species/habitats recorded |
|
Intertidal and continental shelf habitats |
6 |
|
Fish |
24 |
|
Mammals (regularly occurring) |
6 |
|
Shellfish & other invertebrates |
2 |
|
Seabirds (non-PMF) - breeding |
0 |
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Seaducks, grebes & divers (non-PMF) – non-breeding |
0 |
- There are 38 PMFs recorded in this OMR, including a range of fish, marine mammals and rocky and sedimentary habitats.
- The stony and bedrock reef provides a habitat for encrusting and filter-feeding species, including the bryozoan Omalosecosa ramulosa, which is otherwise rare in the inshore sites of this regional sea, and with the shallowest areas of the bedrock and boulders also supporting encrusting coralline algae. Some rare, more northerly species also occur on in the OMR, such as the sponge Phakellia rugosa, the Twohorn sculpin (Icelus bicornis) and the serpulid worm Ditrupa areatina, which forms dense aggregations in some areas of Pobie Bank Reef.
- The sulphide-rich sediments in the pockmarks in this region hosts organisms with chemosynthetic symbionts and sulphide-oxidising bacterial mats.
- The methane-derived authigenic carbonate structures provide a habitat for marine fauna usually associated with rocky reef in an otherwise predominately sedimentary habitat. Larger blocks of carbonate can also provide shelter for fish species such as the wolf-fish (Anarhichas lupus).
Climate change
There is good evidence that climate change is driving changes in the physical, chemical and biological conditions of the marine environment but the current evidence base limits the ability to draw conclusions at the scale of the individual marine regions, including East Shetland Shelf OMR. This is a combination of the lack of comprehensive spatial coverage of key monitoring programmes, the relatively short time series, and the complex linkages of climate change impacts in the marine environment.
Increasing concentrations of atmospheric greenhouse gases have caused more energy to be trapped within the Earth’s atmosphere, land and ocean. Approximately 90% of this excess energy has been absorbed by the ocean, resulting in warming ocean temperatures (see Temperature assessment and Climate change Sea temperature assessment).
The increasing concentration of carbon dioxide, one of these greenhouse gases, has the additional consequence of driving a reduction in the pH of the ocean, a process known as ocean acidification (see Ocean acidification assessment and Climate change Ocean acidification assessment).
Mean sea level is rising due to increased contributions of freshwater from melting of land-based ice (glaciers and the polar ice sheets) and due to thermal expansion of water (see Sea level and tides assessment and Climate change Sea level assessment).
The warming temperatures also result in lower oxygen concentrations due to fact that warm water holds less oxygen and changes in stratification further influence oxygen concentrations (see Dissolved oxygen assessment and Climate change Dissolved oxygen assessment). Together with increased metabolic rates in organisms resulting in increased respiration, oxygen depletion has a severe impact on marine organisms due to the impact on metabolic processes.
These changes in the physical environment are also having an impact on marine life, such as changes to their metabolism, changes in seasonality and the timing of events in natural cycles, and changes in their distribution. These changes have consequences for the growth, survival and abundance of species, including those of commercial importance or critical to conservation objectives.
At present, most of these impacts are assessed at scales greater than marine regions. The Community Temperature Index combines species temperature affinity and their abundances. This index has the potential to inform how communities change due to climate change. An example of changes in the Community Temperature Index from bottom-living fishes can be found in the Fish section within Biological Impacts of Climate Change, where more information on other impacts in marine food webs can be found (such as seabirds and marine mammals) on large regional scales in Scottish waters.
Sea surface temperature in the East Shetland Shelf OMR has increased since 1870 by 0.05 °C per decade on average. The rate of increase has not been constant, and in the last 30 years (1988-2017), there was no statistically significant trend observed.
Summary
The East Shetland Shelf OMR has seen a 13% increase in the value of the fisheries catch over the five years from 2014-2018. Combined hydrocarbons production increased by 49% (i.e. 6.6 million tonnes oil equivalent) over the five years 2014-2018. Subsea cables length increased by 16% over the five years 2015-2019.
The five main pressures affecting the OMR are Surface abrasion, Sub-surface abrasion/penetration, Removal of target species, Removal of non-target species, Litter. Other pressures identified are Hydrocarbon and PAH contamination, Introduction or spread of non-indigenous species, Physical change, Physical removal, Reduction in availability or quality of prey, Litter, Siltation rate changes, Synthetic compound contamination, Transition elements & organo-metal contamination and Underwater noise.
Contaminant (i.e. PAHs, PCBs, PBDEs and heavy metals) concentrations were generally above background but below concentrations where adverse effects could occur. There is a relatively low concentration of microplastics in surface water and no consistent trend in seafloor litter density.
One new MPA was designated between 2012-2018, and no new spatial management measures were put in place. Spatial fisheries management measures are under discussion for two MPAs. One MPA was monitored by statutory bodies during the period 2012-2018.
In the last 30 years there is no statistically significant trend in sea temperature change.