Tees Rivers Trust – Revitalising our Estuaries

On Tuesday 15th April the second of CASaV’s bi-monthly talks on “Revitalising our Estuaries: Tales from the River Tees” was be given by Henry Short and Judy Power from the Tees Rivers Trust.

Many of the UK’s estuaries have experienced high levels of pollution and habitat loss over the last 100 years leading to localised extinctions of many species. The River Tees is no exception with 90% or intertidal habitat lost to land reclamation, and the river being declared ecologically dead in the 1970s. The Tees used to be home to both Oysters and seagrass, but populations of both have dropped drastically around the UK in the last 50 years and have become extinct in the Tees.

The team at the Tees Rivers Trust are working to bring them back. This talk explored the biology of these species, the reasons for their decline, methods and challenge behind restoration and the benefits that these species can provide. 

If you missed the talk you can watch a recording below, see the presentation slide here and read a summary below:

1. Summary (generated by Google NotebookLM):

This outline details the main themes and important ideas presented by Judy Power (Project Manager: Coastal & Estuary) and Henry Short (Senior Project Delivery Officer: Oysters and Seagrass) from the Tees Rivers Trust during the presentation on their work revitalising the River Tees estuary. The presentation outlines the Trust’s catchment-wide approach, the historical context of the estuary’s degradation, current restoration projects focusing on intertidal habitat, native oysters, and seagrass, and future aspirations for a healthier and more biodiverse ecosystem.

2. Main Themes and Important Ideas:

2.1 Catchment-Wide Approach:

• The Tees Rivers Trust adopts a holistic “catchment-wide approach,” recognising the interconnectedness of the river system from its source in the Pennines to the estuary. Judy Power stated: “The river is one living beast. It goes from one end to the other. What happens at one end affects the other end.”
• Upstream pressures, including historical metal mining, industrial milling (weirs), development, agriculture (sediment runoff, unnatural river bends), and invasive species, significantly impact the water quality and biodiversity of the entire system, ultimately affecting the estuary.
• Sediment loading from the River Leven into the Tees, exacerbated by heavy rainfall and various land management practices, is a key concern. The Trust is working on measures to reduce this, such as planting native trees and promoting better land management.
• Man-made obstructions like weirs impede fish passage and alter natural flow regimes, highlighting the need for interventions beyond just the estuary itself.

2.2 The Tees Estuary: A Site of Contrast and Challenge:

• Despite significant industrial modification and land reclamation over the past century, the Tees estuary remains a “spectacular place” and is internationally designated for its importance to bird species and invertebrates.
• Judy Power emphasised that “not many people realise how significant the Tees Estuary is though for global species.”
• The estuary suffers from habitat loss, contamination (though improved since the 1970s), and negative public perception, leading to political challenges balancing economic development with ecological needs (“politics of economy versus ecology”).

2.3 Intertidal Habitat Restoration – website:

• Starting in 2018, the Trust began creating intertidal mudflat habitat as a first step towards restoration.
• The rationale is to provide “service stations” for wading birds along the straightened, man-made river edges, offering feeding and resting grounds.
• These small patches of mudflat also help to absorb the impact of shipping and reduce bank erosion.
• Early efforts were labour-intensive, involving manual placement of rock rolls and brash bundles, and faced challenges such as antisocial behaviour, equipment theft, and costly marine licensing (£9,000 spent on licenses alone).
• Despite these difficulties, the created mudflats accreted sediment quickly, demonstrating the potential for habitat creation.
• The Trust is continuing this work with new trial sites, including the introduction of islands.

2.4 Native Oyster Restoration – website:

• Henry Short is leading efforts to reintroduce the native European flat oyster, which was historically abundant in the Tees but has declined by 90% due to overfishing, reduced water quality, and invasive species (Pacific oyster).
• Oysters are “filter feeders,” with a single oyster capable of filtering 200 litres of water per day, offering significant benefits for water quality (reducing particulates, nitrates, and metal pollutants).
• Their gregarious nature leads to the formation of 3D reefs, providing shelter and nursery grounds for various marine species and helping to protect the coast from erosion.
• The Trust has established an oyster nursery in Hartlepool dock, housing over a thousand oysters in cages. These oysters have shown high survival rates (>95%) and have produced an estimated 100 million larvae over three years. The cages also attract diverse wildlife, including the endangered European eel.
• Seabed restoration is planned to provide hard substrate (e.g., shell) for the oyster larvae to settle on, addressing the lack of natural hard surfaces in the Tees Bay.
• A land-based larval settlement tank was built to increase the success rate of oyster spat (juvenile oysters) attaching to substrate before being deployed in the estuary. While initial results were encouraging (2,000 spats produced), the Trust is working to improve these numbers.

2.5 Seagrass Restoration – website:

• Seagrass, the only marine flowering plant, historically formed extensive meadows in the Tees estuary but has been largely lost due to land reclamation and poor water quality (“wasting disease”).
• Seagrass meadows provide significant benefits, including carbon sequestration, high biodiversity (30 times more than bare sand), nursery grounds for fish, and coastal protection by reducing wave action.
• Initial seagrass planting trials in 2023 using seed bags were unsuccessful due to dynamic sand movement.
• A new approach, the “Tees Restoration Initiative (TERI),” involves a land-based nursery to grow strong seagrass plants in controlled conditions (light, salinity, temperature) and trial different sediment mixtures.
• Encouragingly, seagrass grown in pure sediment from the intended planting site showed the best growth, suggesting the Tees is suitable for seagrass.
• The Trust is now focusing on growing mature seagrass “turfs” with established root systems for more resilient transplantation.

2.6 Future Projects and Wider Ecosystem Considerations:

• The Trust is looking to expand its restoration efforts to include other important species like mussels and kelp, and potentially more intertidal habitat.
• The lack of suitable seagrass habitat due to port development highlights the need for a catchment-based approach to reduce stresses and potentially create new habitat.
• Unexpectedly, blue mussels are thriving in the Tees, growing prolifically in the Trust’s water intake tanks. The Trust is investigating the health of these mussels and their potential for translocation to areas where mussel populations are declining, leading to the establishment of the UK Muscle Network.
• “Fish hotels” (3D structures placed in the water) are being trialled to provide refuge and habitat complexity for fish in the straightened river channels.
• Judy Power highlighted the importance of collaboration and local knowledge, stating, “We can’t do this on our own. You know, it’s not up to us to come and put something in and then just walk away. We’ve got to work with people to make sure they help us look after it.”

2.7 Challenges and Lessons Learned:

• Accessibility to work sites, antisocial behaviour, and the complexities and costs of marine licensing are significant hurdles.
• Working within tidal windows (around four hours) limits the time available for on-site work.
• The importance of engaging with local communities, including fishermen and bait diggers, is crucial for the success and longevity of restoration projects. Their local knowledge is invaluable.
• Baseline data on the historical ecology of the estuary is often lacking, making it difficult to fully assess the impact of restoration efforts.
• Securing long-term funding for staffing and research remains a constant challenge, as nature operates on longer timescales than typical funding cycles.

2.8 Specific Species Notes:

• Pacific Oysters: While considered an invasive species in some areas (e.g., south of the UK), they currently do not breed in the colder waters of the northeast. However, there is concern about their potential impact if water temperatures rise.
• Eels: Despite being tolerant of pollution, European eel populations are struggling, and much remains unknown about their life cycle and migration patterns in the Tees. The Trust has started a tagging program to gather more data.
• Salmon: Historically present, salmon are now found occasionally in the upper Tees, facing challenges with barriers like the Tees Barrage Fish Pass (not originally designed for salmon). Trout are more commonly found further upstream in the Leven.
• Blue Mussels: Their unexpected abundance in the Tees may be linked to a shift in the ecosystem following a recent mass crustacean die-off, reducing predation pressure – plans.
• Kelp: While present in the area, its current extent is debated. Kelp is considered another potential species for future restoration due to its carbon sequestration potential and habitat provision.

3. Conclusion:

The presentation by Judy Power and Henry Short provided a comprehensive overview of the ambitious and multifaceted efforts of the Tees Rivers Trust to revitalise the degraded River Tees estuary. Their work, grounded in a catchment-wide perspective, addresses a range of historical and contemporary pressures. While facing numerous challenges, the Trust has demonstrated promising early successes in intertidal habitat creation and native oyster restoration. Ongoing research and adaptive management, particularly with seagrass, are crucial for long-term success. The Trust’s commitment to collaboration with local communities and a forward-looking approach, considering future ecological changes, are essential for creating a more resilient and biodiverse Tees estuary.

Get Involved

The Tees Rivers Trust would love to hear from you, if you would like to volunteer to help with oyster monitoring or seagrass work, get in touch with Ciara Finn at Tees Rivers Trust by email (ciara@teesriverstrust.org) with the group. Ciara Finn is Tees Rivers Trust’s engagement officer and organises volunteer events.