Cryogenic defaunation of sediments in the field

Ecological experiments designed to examine the effects of macrofaunal biodiversity may require the defaunation of intertidal sediments; however, many current techniques result in physical disruption of the sediments. A method of fieldbased cryogenic defaunation, which has advantages over existing methodologies, was developed to provide macrofaunal defaunation of intertidal cohesive sediment with minimum physical disruption. A sediment core transport apparatus and polystyrene freezing chamber allow the use of liquid nitrogen for effective freezing of a whole core of sediment in the field. Freezing the whole core intact minimises physical disturbance to the sediment and retains the topography of the sediment surface and sediment grain distribution with minimal effect on sediment properties and the microphytobenthos.
This method is effective at removing up to 97% of infaunal macrofauna abundance from the sediment. Hediste diversicolor were found to be the most resistant species, with a 71% reduction in species abundance. Sediments
defaunated in this way can be replaced in situ or removed to the laboratory for experimentation. This method of cryogenic defaunation would also be suitable for the defaunation of other marine or terrestrial sediments.