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Aquatic macroinvertebrate survey and identification, Congresbury Yeo

Client: Team Van Oord
Location: Congresbury Yeo, Somerset

The brief

Our aquatic team were required to survey several ditch sites to assess the range of aquatic invertebrates in them. This was part of our client’s on-going flood defence works.

What Thomson Ecology did for the client

  • Ditches which had been proposed to be infilled were investigated by our aquatic specialists to identify if any rare or scarce species were inhabiting them. Our team surveyed the ditches using a standardised 1mm mesh pond net, and following best practice protocol
  • Several water quality parameters were analysed in the field
  • Aquatic macroinvertebrate identifications were completed either in the field or back in the laboratory
  • Aquatic invertebrates were identified to family level
  • Biotic indices scores were assessed and the Biological Monitoring Working Party (BMWP) biotic index was used to calculate scores for key family groups of aquatic invertebrates present based on their sensitivity to pollution

The outcome

  • Water quality scores for the sites were classed as ‘Moderate’ or ‘Poor’
  • No aquatic invertebrates were recorded as being rare or scarce
  • Works at Congresbury Yeo were able to continue as no mitigation measures were required

Baseline Marine Ecological Assessment

Client: Milford Haven Port Authority
Location: Wales

The brief

Milford Haven Port Authority are proposing to develop port facilities at Milford Haven. Thomson Unicomarine were awarded a contract to undertake baseline ecological assessments of this area. These will be used as a baseline for future monitoring to assess potential impacts on the marine environment.

“We are impressed by Thomson Unicomarine’s in-depth technical knowledge in this area and their enthusiasm to do a good job for us”.
Dave Levell, Environment Manager at Milford Haven Port Authority

What Thomson Ecology did for the client

  • We undertook intertidal and subtidal surveys to assess the conservation value and sensitivity of the area.
  • This new data will place the information within the context of existing marine and maritime data.
  • Our team of highly experienced marine biologists conducted benthos, invertebrate, fish and habitat surveys.
  • This included boat and shore based grab sampling and underwater video surveys.
  • The samples were analysed in our laboratories for biological and particle size analysis.
  • Thomson Unicomarine completed two interpretative reports for intertidal and subtidal biology, respectively.

The outcome

The surveys and reports were completed on time and on budget and were well received. The development proposal is in progress and Thomson Unicomarine continues to take an active involvement.

Decommissioning project, Camelot

Location: North Sea

The brief

The Camelot CA gas platform in the North Sea was decommissioned in 2011. Thomson Unicomarine was commissioned to undertake surveys in 2012 and 2014 to monitor the recovery of the seabed. This was to ensure the site was safe and the marine environment was recovering from any impacts to comply with OSPAR decision 98/3 and the Energy Act 2008.

What Thomson Ecology did for the client

  • We conducted benthic fauna surveys and took samples for PSA and chemical analysis in 2012 and 2014, and we commissioned hydrographic surveys of the well and surveys sites.
  • Photo and video surveys were also carried out to determine if Sabellaria reefs were present in the area.
  • The benthic fauna collected were processed and identified by our in-house marine taxonomy team. The PSA samples were also processed in house.
  • We carried out advanced statistical analysis on the results, comparing results from 2012 and 2014 surveys to determine whether there had been any change in the benthic communities.

The outcome

We determined that there had been no significant change in species composition in the area, and that chemical contamination was not at levels of concern. Our report was signed off by DECC and the decommissioning of the platform was successfully completed.

Dredging consents

Client: Llanelli Sand Dredging Ltd
Location: Wales and South West

The brief

Llanelli Sand Dredging Limited needed to renew their licence for dredging at Nobel Banks on the Bristol Channel, South Wales.

As part of the renewal of consents process, ecological surveys were required at regular intervals to monitor the impact of dredging on marine life.

What Thomson Ecology did for the client

  • We conducted biodiversity monitoring surveys over the course of several years;
  • Fish and benthos surveys were carried out through deployment of grabs and trawls from a survey vessel;
  • Reports were produced that compared biological and habitat data and presented statistical analyses;

Recommendations and outcomes

The surveys and report were completed within a strict timescale and on budget.

No significant changes to the biological communities present at the site were detected.

As a result, Llanelli Sand Dredging Limited has successfully achieved the appropriate licences and consents to continue their dredging operation.

Ecological reports for pontoon extensions

Client: Beckett Rankine
Location: River Thames, London

The brief

Two piers in central London required extensions to enable increased capacity of the river taxi service operated by London River Services. Beckett Rankine commissioned Thomson Unicomarine to assess the impact of these two works on marine ecology in order to comply with marine licence requirements.

What Thomson Unicomarine did for the client

  • We assessed the impact of the piling and placement of new pontoons on the sensitive marine ecology receptors which included fish and marine mammals which are protected under the Bern Convention and the Habitats Directive.
  • We also assessed the impact of these works on the Thames Estuary recommended Marine Conservation Zone, which lists habitats and species for protection.
  • We produced two separate ecological reports for the two different locations.
  • Mitigation measures to minimise the impact of the works on migratory fish were suggested. These included implementing a soft start procedure during piling activities.
  • These reports provide information to support the marine licence application as well as ensuring the projects are compliant with the Water Framework Directive (WFD).

The outcome

Due to the small-scale nature of the works, the impact of these works on marine ecology in the Thames was assessed to be of minor to no adverse significance. It was also concluded that the works would not have an adverse effect on the Thames Middle waterbody. The reports produced supported the client’s application for a marine licence.

Image: Berit Watkin

Environmental Impact Assessment, Port of Harwich

Client: Harwich Haven Authority
Location: Essex

The brief

Harwich Haven Authority is responsible for the maintenance of the Port of Harwich. This includes routine operations such as dredging the navigation channel, disposal of residue and foreshore recharge to mitigate against erosion, as well as potential new developments, most notably at Bathside Bay.

Ecological surveys are required for all these processes, as they have the potential to impact on the marine environment. To date, Thomson Unicomarine, Thomson Ecology’s marine division, has written more than 70 reports for HHA, detailing different aspects of the marine biology of the area and likely impacts of different operations. We also gave expert witness evidence at the public enquiry for Bathside Bay.

What Thomson Ecology did for the client

  • We have monitored changes in the marine ecology of the area through regular fish and benthos surveys, including detailed biotope mapping, boat and shore based sampling of fish and benthos and in situ records.
  • Reports have detailed likely reasons for any changes to benthos, through comparison of maps and statistical analyses.
  • We have recorded and published on the arrival of newly recorded non-native species such as the Oriental shrimp (Palaemon macrodactylus) and Japanese skeleton shrimp (Caprella mutica).
  • We have also recorded changes in the abundance of different fish species over time.

The outcome

All surveys and reports were completed on time and budget and, in later years, results have been presented at annual Regulators Group meetings by our staff. Recorded changes to the biological communities were considered to be due to factors outside the control of HHA and essential port maintenance has continued.

The proposed expansion at Bathside Bay was approved after the public enquiry and agreement to ecological monitoring and mitigation measures. Since then development has been postponed for reasons outside ecology.

Our work within the Stour and Orwell estuaries on behalf of the Authority is still ongoing.

Fish identifications and dissections

Client: Environment Agency
Location: South West England

The brief

Thomson Unicomarine’s fisheries experts were required to identify grey mullet fish species in order to verify data for a national fish-monitoring programme.

What Thomson Ecology did for the client

  • Dissections of each individual grey mullet specimen were completed under the microscope
  • Pyloric caeca, once located inside each fish specimen, were analysed
  • Photographs of internal organ positions were also taken
  • Recommendations and outcomes

    Each grey mullet specimen was identified to species level. Specimens were carefully maintained and returned to the client along with a report on species identification and pyloric caeca details. We provided value for money by producing teaching aids to the client so that their staff would be able to do the work themselves going forward.

    ‘Correct identification is of paramount importance to our work at the Environment Agency; we need to be absolutely certain of the species’ ID as it influences WFD estuary fish classification scores. Thomson Unicomarine gave a quick turnaround on the project and provided us with the identifications, dissected specimens and material that we can use as teaching aids….’

    Rob Hillman, Senior Environmental Monitoring Officer, Environment Agency.

Fisheries management, Hampstead Heath

Client: BAM Nuttall Ltd
Location: Hampstead Heath, London

The brief

The Hampstead Heath Ponds project was implemented by the City of London to protect Hampstead Heath and the surrounding North London area from dam collapse in the event of extreme rainfall. BAM Nuttall, the appointed engineer for the safety works on two chains of ponds on the Model Boating Pond, commissioned Thomson Ecology to undertake a fish translocation exercise. This was part of major works to replace water control structures.

What Thomson Ecology did for the client

We completed a watching brief of the pond drain-down. We obtained an FR2 consent from the Environment Agency, and managed a staged fish rescue operation using seine nets and electric fishing.

Over 1,400 fish were caught and relocated safely to the main body of the lake.

We carried out the humane removal of the population of non-native invasive red swamp crayfish (Procambarus clarkia), and translocated hundreds of native swan mussels (Anodonta cygnea).

The outcome

Our client was able to continue with the silt removal works with no delays.

Harwich Annual Monitoring Programme

Annual benthic data analysis from 2008 to 2015

Client: Harwich Haven Authority

Location: Stour and Orwell estuaries

The brief An extensive programme of sampling has taken place in the Stour and Orwell estuaries since 1997 for Harwich Haven Authority to monitor macrobenthic communities and biotopes. This forms part of the compensation, mitigation and monitoring agreement under the 1998-2000 Capital Dredge Licence to investigate any impacts dredging may have on the benthic environment.

What Thomson Unicomarine did for the client

  • Thomson Unicomarine has undertaken all surveys carried out since 1997 (1997, 2003, 2008-2015). We have analysed all samples taken, identified the benthic organisms present and have carried out particle size analysis (PSA) on the sediment samples.
  • Every year we have produced a report to summarise the findings of that year’s survey, and every 4 years we have produced a report that detects and analyses any trends in community and biotope changes over the previous four years.
  • In the most recent report, univariate statistics were calculated using the data from 1997 to 2015 and multivariate statistics were calculated for 2012 to 2015.
  • Each year Thomson presents the findings of the reports to Harwich Haven and the members of their Environmental Steering Group.

The outcome

Results showed that over the years there had been a change in biotopes throughout both estuaries. Intertidal biotopes are more stable than subtidal biotopes.

Results also indicated that there had been no significant change in species composition between the years.

These reports allow Harwich Haven Authority to monitor effectively the health of the ecosystems within the Stour and Orwell estuaries and therefore respond quickly to any significant changes. This work also allows conservation groups to monitor the presence of prey items for birds present in the adjacent Special Protected Areas (SPAs).

Invasive species, Harwich Haven

Client: Harwich Haven Authority
Location: Stour Estuary, Essex and Orwell Estuary, Suffolk

The brief

In anticipation of the Ballast Water Management Convention becoming ratified in 2017, Harwich Haven Authority commissioned Thomson Unicomarine’s marine consultancy team to investigate and describe the invasive species present within their harbour boundary.

What Thomson Ecology did for the client

  • We analysed data collected by Thomson Unicomarine from the Stour and Orwell estuaries over the past 5 years.
  • We recorded the invasive species identified, where they were found, and looked at any trends in species composition and abundance over the years.
  • We researched the invasive species identified in order to describe their impact on the marine environment, particularly the impact on native species and port and harbour activities.
  • We reported our findings to Harwich Haven Authority with recommendations on the management of these species with regard to the Ballast Water Management Convention.

The outcome

The report was completed on time and to budget and was well received. We were able to advise Harwich on what steps they would need to take next to prepare for any requirements imposed by the Ballast Water Management Convention. This would include the management of ballast waters to reduce the probability of the introduction of marine invasive species. This work has been reported on in industry magazines.

NMBAQC scheme management

Client: Environment Agency/NMBAQC committee

Location: UK and Europe

The brief

We are members of the Biological Effects Quality Assurance in Monitoring Programmes (BEQUALM) / North East Marine Biological Analytical Quality Control (NMBAQC) Scheme and have implemented the Scheme’s Benthic Invertebrate, Particle Size Analysis and Fish Components since its inception in 1994. As part of this we audit 57 laboratories and fish monitoring teams from the UK and Europe that take part in the Scheme, including all major national laboratories and consultancies that value quality control.

What Thomson Ecology did for the client

For the past 19 years, Thomson Ecology have been appointed auditors for the North East Marine Biological Analytical Quality Control (NMBAQC) scheme for the following three core components:

  • benthic invertebrate
  • fish
  • particle size


The NMBAQC scheme, the only one of its kind, sets the standard for assessment of marine biological data contributing to UK national and European monitoring programmes and is intended to develop and promote best practice in relation to sampling and analysis procedures.

As part of the BEQUALM (Biological Effects Quality Assurance Monitoring programme), the NMBAQC scheme is open to participants across the European Union and has recently been expanded to include laboratories operating in all OSPAR regions.

As we are responsible for the implementation of three of the Scheme’s core components, all of our auditing work is under scrutiny by the participating laboratories and the steering committee. There are also additional procedures in place for the auditing of samples analysed by Thomson Ecology and we follow additional quality control by means of external audits.

Water Framework Directive (WFD) assessments

Location: London

The brief

The Water Framework Directive (WFD) came into force in 2000 and requires all navigational dredging and/or disposal activities located within water bodies to undergo a WFD assessment. Thomson Unicomarine were commissioned to undertake a WFD assessment for a proposed maintenance water injection dredging campaign in the Thames Estuary.

What Thomson Ecology did for the client

  • We completed a WFD assessment in line with the Environment Agency’s (EA) ‘Clearing the Waters’ guidelines.
  • We used publicly available data and chemical analysis from recent sediment sampling to assess the impacts of using water injection dredging to maintain the berth depth on the water body.
  • The report was submitted to the Marine Management Organisation to support the marine licence application.

Recommendations and outcomes

Thomson Unicomarine concluded that using water injection dredging for this maintenance dredge campaign was unlikely to have a significant adverse impact on the water body or the WFD objectives. The report was well received by the EA which has used it to illustrate what it would like to see included in all WFD assessments from now on.

White-clawed crayfish survey, Leeds

Location: River Aire, Leeds

The brief

The brief As part of on-going monitoring for the Leeds Flood Alleviation Scheme (FAS), surveys were required to ensure construction works were compliant with environmental planning conditions. We were asked to provide technical expertise by surveying a section of the River Aire for white-clawed crayfish.

White-clawed crayfish are protected in the UK. This species is listed under the European Union’s (EU) Habitat and Species Directive and is listed under Schedule 5 of the Wildlife and Countryside Act (1981). It is also classified as Endangered in the IUCN Red List of Endangered Species.

What Thomson Ecology did for the client

  • We surveyed sections of the River Aire and the adjacent canal by deploying and baiting crayfish traps throughout the watercourses. Fish that were caught in the traps were identified and returned to the water.
  • Our results showed that no white-clawed crayfish were present throughout the site. This confirmed previous data records for the site.

The outcome

We were satisfied that our client’s works could continue on site without delay.