1. This app provides an overview of the Regional Seabed Monitoring Programme, an innovative approach to compliance monitoring adopted by the UK marine aggregate dredging sector.

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Introduction

The RSMP seeks to ensure the seabed remains suitable for recolonisation after dredging, thereby satisfying the ‘similar seabed’ condition imposed on all licences and improving sustainability.

The approach offers a number of benefits:

• Developers work collaboratively on environmental monitoring
• Clear scientific rationale to ensure seabed recovery after dredging
• More consistent and better quality data
• Improved statistical power, with individual sites providing replicates of a treatment effect
• Ability to differentiate between statistical and ecological significance
• Big data used to identify limits of acceptable change
• Outputs allow for effective decision making
• On-line tools for data analysis
• Regional reporting
• Results allow for adaptive management to ensure seabed health
• 50% lower costs (Mineral Products Association, 2014)

This storeyboard app tells the story of the RSMP, from initial concept through to reporting (read tabs from left to right), and is designed to provide all stakeholders with a useful point of reference.

2. The marine aggregate dredging industry produces sand and gravel from offshore extraction sites for use in construction, fill and coastal defence.

Location

• Extraction sites are located in seven dredging regions (see map opposite).

Dredging Process

• Material is extracted using trailer suction hopper dredgers.
• The dredging process involves a pipe being lowered to the seabed, and a powerful pump entrains water and sediment up into into the vessel hold.
• As the cargo is loaded, water overspills from special chutes located in the side of the vessel.
• Cargo composition (i.e. sand:gravel ratio) can be modified, where licence conditions allow, using a process called screening in which unwanted sediment fractions are returned to the seabed.
• Cargos are offloaded at dedicated wharf facilities, or used directly for beach recharge and fill projects.

Further Information

• Further information on the marine aggregates industry can be found on the BMAPA and The Crown Estate websites.

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3. The extraction process can have a number of environmental effects, although these are dependent on the local environment.

Research

• Potential direct and indirect effects of marine aggregate dredging are neatly presented in the figure below.
  
  
  

        Source: https://addyst.blogspot.co.uk/2015/01/marine-dredged-aggregates.html

• Dredge plumes may occur at the surface as a result of overspill or screening, or at the bed as a result of contact of the dredge pipe.
• Plumes are influenced by tides, and fine material may settle out beyond the confines of the licensed area.
• Dredging may also change the topography of the seabed, through creation of dredge furrows and depressions. These features may become less visible over time, depending on local environmental conditions.
• Where the draghead makes contact with the seabed this results in removal of sediments and associated animal communities.
• Understanding of the effects of marine aggregate dredging is underpinned by decades of research (see references opposite), most recently through the Aggregate Levy Sustainability Fund.
• Given that impacts of aggregate dredging on the benthos are now reasonably well understood, it makes sense to focus attention more towards recovery, given the obvious link to sustainability.

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4. It is accepted that dredging will lead to a loss of sediment and associated animal communities. The important question for sustainability is what happens to the site after cessation of dredging (i.e. recovery)?

What we know about recovery

• Understanding of seabed recovery has improved in recent decades (see relevant publications opposite).
  
  
• Studies show that fauna will recolonise dredge areas, but the nature of the recovery will depend on how much the physical habitat, especially the composition of sediments, has changed.
  
  
• Physical changes such as accumulated fine sands may naturally disperse under the influence of tidal currents, although this can delay the faunal recovery process (see example below from Waye-Barker et al. (2015).
  
  
  
  

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5. While persistent physical impacts can theoretically be addressed through active seabed restoration, measures are likley to be expensive and only partially successful.

Restoration Approaches

• Potential seabed restoration techniques (active and passive) were explored in a report commissioned by industry and avaialble here.
• Experimental trials include deposition of shell cultch (Collins & Mallinson, 2007) and gravel seeding (Cooper et al, 2007).
  
  
  
• Results from these studies show some success, but the work is challanging, expensive and arguably better termed ‘enhancement’ given the difficulty of replicating lost habitat.
• Situations in which restoration might be required arguably represent a failure of monitoring/management.
• To improve sustainability, the focus for monitoring must be to check on the status of the seabed to ensure that it can recover post dredging.

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6. To maximise the potential for biological recovery, developers are required through a licence condition to ‘leave the seabed in a ’similar condition’, but what does this mean?

What do we mean by 'similar'

• Deciding what constitutes a ‘similar’ seabed can be highly subjective.
• To address this issue, Cefas developed a new approach to identifying similar seabed based on the range of habitat conditions naturally found in association with faunal communities.

Here's how it works

• Grab sample data are used to establish the relationship between faunal assemblages (i.e. biota) and sediment particle size.

• Understanding is then used to determine whether conditions within the licensed area remain suitable for recolonisation by the original assemblage type (see Cooper, 2012).

• Approach tested at a regional scale using data from the East Channel (Cooper 2013).

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7. In 2013, a decision was taken to further develop this concept of ‘similar’ sediment and to role it out as part of a regional approach to monitoring - the RSMP.

Research & Development

• Work formed the basis of a PhD thesis, allowing for academic oversight (see Cooper, 2013).
• A major tasks involved collation of data from multiple sources, to improve understanding of the relationship between fauna and sediments.
• Collated data marked the start of the OneBenthic initiative, with data subsequently used to gain insights into many other areas.
  
  
  

        Fig. Faunal assemblages and associated sediment particle size (From Cooper & Barry, 2017).

• A major fieldwork campaign was undertaken in 2014/15, funded by the aggregates industry, to ensure good sample coverage with aggregate dredging areas and zones of potential secondary effect.

• Work was undertaken by Cefas, with support from the following organisations (funders in boxes):
  
  

  

• Extensive work undertaken by the Marine Management Organisation and the aggregates industry to work out the practicalities of implementation (see documents opposite).

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8. Here’s how it works:

Survey Array

• There are seven RSMP regions, although surveys in the Bristol Channel and North-West are undertaken on a site by site basis. Explore the survey arrays in the map opposite.

• An array of sampling stations is established across each site and surrounding area by Cefas. This will include approximately 20 stations within the licensed area/ Primary Impact Zone (PIZ) and the Secondary Impact Zone (SIZ) (i.e. 40 within zone of potential dredging effect). In addition, a small number of stations will be established in the area surrounding the site (CONTEXT area), and, if necessary, at a reference site.
  
  

  
  
  

• The SIZ footprint is determined by the developer at the Environmental Impact Assessment (EIA) stage, based on one of more of the following approaches: i) tidal excursion (from PIZ boundary), ii) modelling, and iii) field-based research. Spearman (2015) provides a useful synthesis and critique of the findings of fieldwork excursions out to licence areas to measure plume extents and seabed footprints. Investigations using a range of geophysical and water column optical backscatter techniques together with seawater sampling, seabed sediment sampling and seabed profile imagery were conducted over several years in separate peer-reviewed studies to define dredger overflow plume concentrations, their extents and any associated changes to seabed sediments that arose both spatially and over time. A diverse group of licence areas were studied: Area 106, 107 and 408 off the Humber, areas 430 and 222 off East Anglia, Area 473 East and an area off Dieppe in the eastern English Channel, area 122/1 (“Owers Bank”) and areas 122/3 and 351 east of the Isle of Wight. Spearman’s synthesis of these studies concludes that no impacts of dredging were identified more than 3 km from dredged seabed. Footprints of change in substrate generally extend just a few hundred metres from the point of dredging, unless there is extensive on-board screening of the sand fraction back to the seabed where there is little natural background sand transport, when footprints then may extend up to 2.6 km. The 4km secondary impact zones generally adopted for the RSMP thus err on the side of caution in terms of their extent and the degree of monitoring undertaken within them. Due to very high background suspended sediment concentrations in the Severn Estuary/Bristol Channel, SIZs here are limited to 500m.

• A request for a survey array must be made via the MMO, so that Cefas can recover costs for the work (approximately 1 day of time).

• Where possible, stations will be established at previously sampled sites, reducing the need for collection of new macrofaunal samples.

• Survey arrays are stored in the OneBenthic Survey Array Tool.
  
  

  
  
  

Surveys

• All sites are sampled for macrofauna and sediment particle size during an initial baseline survey, providing a record of the assemblages present with areas of potential dredging effect (PIZ/SIZ), and improving understanding of the relationship between macrofaunal assemblages and habitst (sediment particle size).

• The baseline benthic survey may be undertaken in isolation, or as part of a wider RSMP Monitoring survey. The choice will depend on: i) whether the site is in an area where RSMP surveys are undertaken regionally (Humber, Anglian, Thames, South Coast, East Channel), ii) the length of time until the next regional survey and whether this fits in with the developers timeframe for production of an EIA.

• Sites are then monitored once every 5 years. During these surveys, macrofaunal samples are only required from the context area. These samples fulfill two objectives: (i) to ascertain and ensure that an un-impacted faunal assemblages remain within the wider region (this is important as these assemblage will play an important role in the recolonisation after dredging has ceased), and (ii) over time, the acquired time-series data will show the capacity of the region to cope with the level of anthropogenic pressure, be it from aggregate dredging or other sources.

• During monitoring, stations within PIZ, SIZ and Reference are only sampled for sediment particle size. The logic behind this practice is that, if sedimentary conditions within the footprint of potential dredging effect remain within the regional range (i.e., the pre-defined limits of acceptable change have not been exceeded during dredging), then it should be possible for a return of the original faunal assemblage type after dredging has ceased. Reference sites provide a perspective on natural or non-dredging related change - this is important to aid interpretation of data from the PIZ/SIZ.

• All samples are collected and processed in accordance with a strict RSMP Protocols document which can be accessed using the OneBenthic Survey Array Tool (see ‘Protocols’ tab).

  

• Collected data are stored within the OneBenthic database, and a series of web apps are used for analysis of data (see following tabs).

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9. Following completion of the baseline survey, an RSMP Baseline Report must set out what faunal assemblages are present within development area and zone of influence.

Benthic Baseline

Issue

• Understanding what benthic macrofaunal assemblages are present within the footprint of potential dredging effect is key to the RSMP approach and will determine what level of changes in habitat (i.e. sediment particle size) can be tolerated.
• Following completion of the baseline RSMP survey, data and associated reports should be sent to Cefas for upload to OneBenthic.

Supporting Apps

• As part of the upload process, new macrofaunal data are matched to existing cluster groups (i.e. assemblage types) using the OneBenthic Faunal Cluster ID Tool. The methodology used in this app is set out in this publication.
• Once data have been uploaded then they will be visible in the OneBenthic Baseline Tool.

Reporting

Baseline results should be reported in a site-specific report, using the template (see right) as a guide.

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Reporting Template

10. Monitoring surveys are undertaken every 5 years, with sediment data used to check for i) evidence of Gross Sediment Change.

Gross Sediment Change

Issue

• Marine aggregate dredging has the potential to cause changes in seabed sediment composition as a result of the fallout of fine sediments, selective remove of particular sediment fractions or exposure of underlying material which is different in nature to that present before dredging.
• Such changes can have implications for faunal recovery and thus sustainability.
• Given the above, a primary goal of the RSMP is to establish whether there is any evidence of gross changes in sediment composition, both at the scale of the individual licence and the wider sub-region (if appropriate) and region.

Supporting App

• Analysis is undertaken using the OneBenthic Sediment Change Tool.
• This app looks for evidence of statistically significant changes in sediment composition. Samples are assigned to treatment groups based on available polygons, with data (Wenthworth size classes) assessed using line plots, non-metric MDS, ANOSIM and SIMPER.
• For a full explanation see the video below.
  
  

Reporting

Monitoring data are analysed at a variety of spatial scales and must therefore be reported regionally using the template (see right) as a guide (see sections 2.2.1, 3.2.1 and 4.1.1).

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Reporting Template

11. and ii) whether local sediment change is likely to be ecological significanct (M-test).

Ecological Significance of Sediment Change

Issue

• It is possible for changes in sediment composition to be statistically significant, but of little consequence for the fauna (i.e. not ecologically significant).
• A method for determining the ecological significance of changes in sediment composition at individual sampling stations was put forward in Cooper and Barry, 2017, and implimented in the OneBenthic M-test Tool.

Supporting App

• The app looks at the sediment composition of each monitoring sample and determines, using a Mahalanobis distance test (see Cooper and Barry, 2017), whether the composition of sediments remains suitable for recolonisation by the original assemblage type. Failed samples are flagged and the sediment fractions responsible for are highlighted, providing useful information for adaptive management.
• Note there are a variety of reasons why a sample may be flagged, including aggregate dredging, and it will be neccessary to determine the most likely cause using other sources of information (e.g. Electronic Monitoring system data showing the location and intensity of dredging).
• Data for use with the app can be obtained from OneBenthicAPI-5 (see API tab in the OneBenthic Portal). Save data as a .csv file following instructions provided on the API tab.
• For a full explanation see the video below.

Reporting

• Monitoring data are analysed at a variety of spatial scales and must therefore be reported regionally using the template (see right) as a guide (see sections 2.2.2, 3.2.2 and 4.1.2).

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Reporting Template

12. An assessment is also made regarding the status of faunal communities surrounding extraction sites, firstly by assessing the spatial distribution of assemblage types.

Faunal Assemblage Distribution

Issue

• Benthic faunal communities surrounding aggregate extraction sites serve an important role in the functioning of the wider ecosystem and are a source of adults and larvae for recolonisation of extraction sites after cessation of dredging.
• One means of checking on the health of these communities is to monitor for changes in assemblage distribution. For example, are the patterns seen in the baseline tool still evident?
• Note the tool below can also be used to assess faunal recovery of former dredging sites, following a suitable period for recovery, and where macrofaunal samples have been collected.

Supporting App

• Macrofaunal data from monitoring samples (CONTEXT area only) are matched to existing cluster groups using the approach set out in this paper and implimented in the OneBenthic Faunal Cluster ID Tool.
• Patterns should be compared with the baseline and previous monitoring campaigns.
• See the video below For a full explanation of how the tool works.

Reporting

• Monitoring data are analysed and reported at a regional scale using the template (see right) as a guide (see section 2.2.3, 3.2.3 and 4.1.3).

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Reporting Template

13. and secondly, how macrobenthic communities may have changed.

Change in Macrobenthic Communities

Issue

• Benthic faunal communities surrounding aggregate extraction sites serve an important role in the functioning of the wider ecosystem and are a source of adults and larvae for recolonisation of extraction sites after cessation of dredging.
• A further means of checking on the health of these communities is to compare data from baseline and monitoring surveys, using both univariate (i.e Analysis of Variance) and multivariate (nMDS ordination, ANOSIM and SIMPER) approaches.

Supporting App

• Analysis is undertaken using the OneBenthic Faunal Change Tool.
• This app looks for evidence of statistically significant changes in faunal composition. Samples are assigned to treatment groups based on available polygons, with data assessed using ANOVA, non-metric MDS, ANOSIM and SIMPER.
• For a full explanation see the video below.
  
  

Reporting

Monitoring data should be reported regionally using the template (see right) as a guide (see sections 2.2.1, 3.2.1 and 4.1.1).

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Reporting Template

14. Finally, results from monitoring are used, where necessary, to inform adaptive management decisions.

• Results of monitoring should be used to determine if any management steps are required. What steps are are approprite will depend on the strength of the evidence and the link to dredging, the capacity for natural recovery and the importance of the affected assemblage.

RSMP Guidance Notes

Guidance Notes

These guidance notes provide clear, shared instructions to help all parties—analysts, operators, regulators, and environmental managers—follow consistent sampling protocols and interpret RSMP results, ensuring a common understanding and approach across the programme.