Assessment of the sensitivity of these biotope complexes to naturally occurring events is complicated due to the many important and measurable physical and biological features. This chapter attempts to identify the responses of the biological and physical features to natural events and the sensitivity of these features to such incidents. Vulnerable biotopes and species are identified with regard to their stability, recoverability and the frequency of the natural influences.

The long term stability of benthic communities is relatively poorly understood. The community dynamics of intertidal sand and mudflats are reasonably well known and barring severe changes to the sedimentary regime by wave action or other impacts they may appear more stable than subtidal environments. The long term dynamics of subtidal areas are much less understood due to the increased complexity of the environment, the large number of species involved and the difficulty in sampling the habitats. However subtidal areas including sandbanks undergo periods of stability followed by periods of instability which may extend over several years. This may be linked to winter temperature variation and biological interaction as well as changes in the physical regime or influx of organic matter.

Subtidal mobile sandbanks are not subject to periodic exposure to the air and subsequent drying out as in intertidal areas but many parameters (summarised in the table below) which influence intertidal sand banks do affect subtidal sand banks. The natural influences affecting subtidal mobile sand banks vary depending on their location. Sand banks occurring in estuarine or semi-estuarine conditions e.g. the Solway Firth may be subject to some fluctuation in salinity and temperature. Fully marine sandbanks generally will be less affected by these parameters.

Important natural parameters which influence the habitat features.

Impacts of climatic conditions

Impacts of freshwater runoff and salinity changes

The influence of ecological relationships

Impacts of sea level rise

References