Standardising the assessment of Functional Integrity in benthic ecosystems

• We develop a cost-effective assessment of Functional Integrity of marine habitats.
• The approach is based on video surveys of epibenthos and biogenic habitat features.
• We estimate functional diversity, spatial heterogeneity and habitat complexity.
• The approach was tested in two locations of New Zealand with different survey strategy.
• It proved effective as a first step to assess ecological integrity of marine systems.

Ecological integrity is an overarching concept that integrates multiple properties of ecosystems, including structure, function and resilience to external change. We explore the links between ecological integrity and structural surrogates for ecosystem functioning to develop a cost-effective assessment of Functional Integrity for marine habitats based on biological traits, abundance and heterogeneity, focused on the visible components of the seafloor, i.e., epibenthic flora and fauna and seabed biogenic habitat features. The assessment was based on diversity and redundancy of functional traits of the identified benthic components, supplemented by estimates of spatial heterogeneity (habitat transitions) and vertical habitat complexity. This approach was developed using video data collected in different years with different sampling strategies in two locations: Kawau Bay in North Island of New Zealand, and Port Pegasus in Stewart Island, off South Island of New Zealand; this last location was a priori expected to be nearly—pristine. Despite variability in sampling techniques and environmental settings, the approach proved effective and evidenced higher measures of Functional Integrity in the Port Pegasus location. This study introduces a first step to measure ecological integrity by successfully converting video data to surrogates of Functional Integrity, in a way expected to be habitat independent.