Assessing stress resilience of seafloor communities using functional traits

Marine invertebrates living on and within seabed sediments (macrofauna) are influenced by physical, biological and chemical processes occurring in the environment. Such processes result in the establishment of distinctive patterns of macrofauna distribution and diversity, on local and regional scales. Within species assemblages, the macrofauna exhibit a variety of characteristics, or traits, which determine their role within seafloor communities and habitats. Examples of so called functional traits are longevity, body size and reproductive strategy. Functional traits can also provide an indication of tolerance of macrofauna to stress and disturbances.

Washing a sediment sample

In order to closely examine macrofauna assemblages in the marine environment, sampling techniques such as grabs and boxcorers are routinely utilised to acquire sediment samples for laboratory analysis. This equipment is deployed from research vessels and lowered to the seabed. The weight of the equipment allows it to penetrate the sediment and upon recovery the grab closes, securing the sample inside. Samples are preserved for subsequent analysis of numerous biotic and abiotic parameters including particle size analysis and macrofauna, to allow researchers to characterise the seabed sediments. Alongside traditional sampling techniques, sediment profile imaging technology can also be used. This is a very efficient method, which takes cross-sectional images of the top 20 cm of the seabed, with minimal disturbance to the sediment. The resultant images allow a rapid assessment of sediment properties including grain size, redox depths, macrofauna burrows and tubes, which provides a valuable tool for seabed characterisation.

Collecting specimen

The aim of sub-project 3 will be to examine the functional traits of macrofauna assemblages, in relation to resilience and recoverability. It will examine the role of interacting hydrological, physical, chemical and biological factors in shaping the distribution, structure and functioning of the macrofauna on broad and fine scales. Functional traits analysis will be used to examine possible relationships between the biology, ecologically significant abiotic characteristics and man-made influences on the seafloor species assemblages. This subproject will be conducted in close cooperation with sub-project 1 and sub-project 2 and will verify if the species expected based on acoustic and visual means are indeed present.

Historic datasets will be examined as part of the survey planning process and will also be incorporated into the analysis, to provide a comprehensive study of the macrofauna communities in representative parts of the Dutch sector of the North Sea.