Pressures

What else might hinder kelp’s recovery?

Though kelp was once abundant in Sussex, several factors have changed since the 1980s which may prevent it coming back. These include poor water quality, increased sedimentation, changing water temperature and storm events.  ​ 

The SKRP is assessing the potential sources and impacts of other non-fishing pressures to understand which factors pose the most significant threat and which can be managed to improve conditions for natural kelp recovery.  

​Sediment

Sediment has been highlighted by many Sussex stakeholders as an issue of concern - not only for kelp recovery - but for local shellfish populations. Because of this it has been the SKRP’s initial focus.

Sedimentation is a natural process arising from land run off, erosion and wave scour, but human activity whether on land – such as farming and urban development – or in the sea – such as trawling and dredging, have increased the levels of sedimentation and nutrient loading into coastal environments over recent decades.​

Sediment has consistently been linked to the disappearance of kelp forests in many areas around the world.

Increased levels of sediment can be harmful to the growth and reproduction of kelp by:

• Smothering or physical scouring of rocky substrate - so kelp can’t attach itself to the seafloor

• Increasing turbidity (making the water cloudy) which reduces the levels of light in the water column that kelp need to grow.​ 

Various activities have been initiated by the SKRP to understand the sources and impacts of sediment.

Sediment research

The University of Sussex are assessing the impact of Suspended Particulate Matter (SPM) on kelp.

Research will assess the source (land run-off, erosion, rivers, outflows, storms); composition (organic, inorganic and toxic elements); and impacts of SPM on kelp by:

• Sampling fresh and marine water interfaces and nearshore coastal environments

• Assessing the impact of SPM on kelp growth using controlled experiments in aquaria

• Evaluating sources, contaminant transfers, impacts, and destination of SPM to underpin our understanding of changes to water clarity and the photic zone within Sussex Bay and its implications for kelp ecosystem recovery.

Sediment surveys

A wealth of information is held by local people, many of whom have been in, on or near the sea every day for many years. These include divers, skippers, rowers, sea swimmers, beach walkers, kite surfers as well as commercial and recreational fishers who have been canvassed about their observations on change in the type and level of sediment seen in Sussex over the years.

Sediment workshops and reports

Workshops hosted by SKRP partners have convened government agencies, universities, community groups, fishing societies and more to review the sources and impacts of sediment in Sussex.

Reports from these workshops along with desk based studies have summarised previous studies on sediment transport, sources and sinks in Sussex waters; recent trends in sediment levels; potential future trends linked with climate change, coastal development and marine activities; and the regulatory and policy framework relating to management of sediment inputs.

This initial assessment will inform development of a collaborative, cross-sector sediment monitoring and adaptive response plan.