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Project: Comparison of US and European Benthic Indices

Background and Objectives

Benthic infauna are commonly used as an indicator of overall ecological condition in the marine environment. Interpreting impacts to benthic infaunal assemblages is challenging due to the complexity of biological communities; hundreds of species and thousands of individuals may be found within one square meter of sediment. Benthic indices synthesize this complexity into an overall site score that can be used for monitoring and reporting. However, benthic indices have only been developed for a subset of regional marine habitats in California, mainly due to a paucity of benthic data available for the other habitats. Furthermore, few studies have calibrated indices from different habitats to ensure that similar index scores are indicative of similar levels of impact across multiple habitats. SCCWRP has developed partnerships with European researchers who use different benthic indices from those used in the United States and are working to unify benthic index assessment scales across Europe, as part of the European Union Water Framework Directive.

The goal of this project was to evaluate the performance of a less data-intensive European benthic index in California marine habitats, and evaluate the feasibility of intercalibrating benthic indices from multiple habitats in southern California, the east coast of the US, and Europe.


This project was initiated in 2008 and completed in 2010.


SCCWRP hosted researchers from Europe to collaborate on studies comparing European sediment quality assessment approaches to the approaches developed by SCCWRP for California’s sediment quality objectives. The project had two main tasks:

1) Evaluate the potential for extending the European AZTI Marine Biological Index (AMBI) application out of its initial regional range: The AMBI is promising because its adaptation to a new environment is easier. Unlike the California indices, the AMBI does not require a large set of data to recalibrate for each new habitat/region in which it is applied, relying instead on a universal classification of the population ecology of benthic species. The AMBI was developed initially for the Basque Country, Spain, but is already in use in other geographical areas such as Europe, Asia and South America. The main goal is to compare the performance of the AMBI and the Benthic Response Index (BRI) used in southern California estuaries and bays to assess the fragilities and procedures necessary to adapt the AMBI for new geographic conditions. Once the process is determined for applying the AMBI accurately in a data rich habitat, researchers will use the same process to assess data-poor habitats that cannot be assessed at present.

2) Quantify the level of agreement among some of the world’s leading experts in benthic assessment for data from four different geographies: Data was used from the east and west coasts of the US, as well as the Atlantic and Mediterranean coasts of Europe. This exercise illuminates the potential, and the procedures necessary, for unifying benthic assessment scales across different parts of the world. This task was based on a “best professional judgment” approach, which was successful in a previous study in California.


Site rankings were highly correlated among experts, regardless of whether they were assessing samples from their home region. Also, there was good agreement on condition category, though agreement was better for samples at extremes of the disturbance gradient. The absence of regional bias suggested that expert judgment is a viable means for establishing a uniform scale to calibrate indices consistently across geographic regions.


This project was conducted in collaboration with AZTI Tecnalia (Dr. Angel Borja) and the Universidade de Coimbra (Heliana Texiera).


Unifying benthic assessment scales across habitat boundaries - January 2010 presentation to SCCWRP member agencies detailing the approach and results of a "best professional judgment" comparison.
For more information on Comparison of European and US Benthic Indices, contact Steve Weisberg at (714) 755-3203.
This page was last updated on: 6/30/2014