To manage protected areas effectively and give appropriate advice, it is important for Natural England to understand the water quality conditions that will lead to the favourable condition of protected features. This review collates the evidence on the impact of nitrogen and phosphorus compounds on the condition of typical saltmarsh species present in the UK marine environment.
Abiotic and biotic factors that could affect the impact of elevated nutrients on these species were also considered to understand how impacts of water quality may differ across protected areas. There was robust evidence that nutrients, particularly nitrogen, altered the Saltmarsh species composition of different marsh zones in the European context, with both ‘winner’ and ‘loser’ species. Sediment type, salinity, deposition/accretion, temperature and pH appeared to co-vary with nitrogen and differences in vegetation communities.
Relationships between salinity, phosphorus and vegetation was shown by multiple studies, including through residence time. This rapid evidence assessment suggests the context of a given saltmarsh will potentially influence its response to additional nutrients. The response may further depend on what nutrient forms are present in the marine and terrestrial environment, and the sources from where they derive.
The evidence uncovered suggests that the processes through which saltmarsh features could respond to nutrients can be complex.