No photo of David Morritt

David Morritt


  • TW20 0EX

Personal profile

Research interests

Overview of current research

My original work examined how invertebrate groups are adapted to stressful habitats and how they respond to environmental stresses, both natural e.g., salinity, temperature and xenobiotic e.g., pesticides, heavy metal pollutants. Other studies addressed activity patterns and adaptations to desiccation / thermal stress in highshore tropical and temperate molluscs and thermal tolerance and evolution in crustaceans associated with hot springs. My interests in aquatic pollutants have included studies on endocrine disruption in marine (bivalve molluscs) and freshwater (gammarid amphipods) invertebrates and fish; the lethal and sub-lethal effects of pesticides on freshwater midge larvae and use of probabilistic risk assessment and extrapolation between freshwater and marine toxicity data sets.

Current research interests include collaboration with Dr Paul Clark at the Natural History Museum, London on the biology of invasive (Chinese mitten crab, Eriocheir sinensis) and threatened (European eel, Anguilla anguilla) species in the River Thames and reservoirs in SE England.

Chinese mitten crabs are one of top 100 invasive species in the world and are now well-established in the Thames and certain other river catchments where they can cause damage to river banks, damage fishing gear and have an impact on native species and fisheries. Adult mitten crabs spend a number of years in the freshwater reaches of rivers but have to return to sea to breed and for females to release the larvae. Once the early developmental stages have settled out of the plankton the juvenile crabs then migrate from the estuary back up the river. Our work on mitten crabs includes monitoring of the autumn seaward migration of adult crabs at Walton-on-Thames (Thames Water) and a public recording scheme to record the distribution of Chinese mitten crabs across England and Wales (see for further details). 

A project combining both species in a fyke net study in the inner Thames estuary compared different fyke net designs. The aim of the project was to identify a fyke net design that can potentially maximise the catch of invasive Chinese mitten crabs whilst minimising the bycatch of other fish, especially undersized European eels. This study was funded by the Marine Management Organisation and the Environment Agency.

One of the unexpected outcomes of this study was the large amounts of plastic litter recovered from the fyke nets set to fish on the river bed. Publication of these results and subsequent media coverage and outreach events led to this becoming a new focus of research collaboration with Dr Paul Clark (NHM). Not only have we documented macroplastics in the Thames but we have increasing evidence of the presence of microplastic fibres and fragments in the guts of fish and other biota, especially crabs, in the Thames food web. In addition we have described very high levels of microplastics in the water column of the Thames (in collaboration with ZSL) and the impacts of plastic-containing wet wipes on the foreshore biota of the Thames. Another study made a comparison with fish species in the Clyde Sea. Other current studies are focussing on  the impacts of microplastics on sedimentary shore organsims in the Clyde Sea and the potential impacts of micro- and macroplastics on reef manta rays in the Brtish Indian Ocean Territory. Data from published papers have been used to support the Port of London's Cleaner Thames campaign, Hubbub's For Fish's Sake campaign, have been presented at a All Party Parliamentary Group on Marine Litter and cited in a report on bottled water to the London Assembly Environment Committee. More recently we have contributed to ZSL's The State of the Thames 2021 report and provided input to a breifing note in support of recent Bill put forward by Fleur Anderson MP proposing a ban on the production of plastic-containing wet wipes. We also contribute to the Thames Estaury Partnership Litter Forum and Marine Litter Action Network.


Expertise related to UN Sustainable Development Goals

In 2015, UN member states agreed to 17 global Sustainable Development Goals (SDGs) to end poverty, protect the planet and ensure prosperity for all. This person’s work contributes towards the following SDG(s):

  • SDG 3 - Good Health and Well-being
  • SDG 6 - Clean Water and Sanitation
  • SDG 7 - Affordable and Clean Energy
  • SDG 11 - Sustainable Cities and Communities
  • SDG 13 - Climate Action
  • SDG 14 - Life Below Water
  • SDG 15 - Life on Land

Collaborations and top research areas from the last five years

Recent external collaboration on country/territory level. Dive into details by clicking on the dots or