Benthic Indicators of Coastal Marine Ecosystems Health

• Paolo Magni
• IMC – International Marine Centre, Loc. Sa Mardini, 09072 Torregrande-Oristano, Italy.
  Email: p.magni@imc-it.org
• The Regional Workshop on Marine Sciences & Natural Resources 25-26 May 2004.

Abstract

Many coastal marine ecosystems are subjected to environmental stress and degradation from pollution. Especially in shallow water, benthos dynamics are tightly related with processes occurring in the overlying water column. Integrated measurements of physical, chemical and biological components of the benthos may thus represent important tools in the assessment and implementation of existing observing systems.

Several research programmes have addressed this problem and produced relevant data sets for specific areas, often including consistent sets of environmental and biological variables. The value of existing data sets can be highly increased by combining them into a common data set to determine large scale relationships and assess relevant indicators of ecosystems health. Important attributes of such an indicator are: (1) reliability in their ability to detect stress; and (2) ease of use and broad applicability in different parts of the world. A specific programme addressing this task has been initiated by the Intergovernmental Oceanographic Commission (IOC) of UNESCO with the formation of the Study Group on Benthic Indicators http://www.ioc.unesco.org/benthicindicators

In a first study, macroinfaunal and total organic carbon (TOC) data from 7 regions around the world were merged into a common data set. They were examined to look for consistent patterns of association and identify TOC critical points for evaluating risks of impaired macrofaunal benthic communities. Species diversity was selected as the primary response parameter. Results suggested that risks of reduced benthic diversity from organic loading and associated stressors in sediments should be relatively low at TOC concentrations < about 8 mg g-1, high at concentrations > about 36 mg g-1, and intermediate at concentrations in-between. These findings will be discussed in relation to the ability to identify threshold values in selected environmental and biological variables that could serve as indicators, or "warning signals," of related adverse environmental conditions leading to stress in the benthos.

Through this initiative, it is aimed to bring awareness to the use of biological benthic tools as an aid for monitoring the coastal marine ecosystem and an important path in capacity building, quality control and assessment processes. Within this context, a strong collaboration among countries in the entire Mediterranean basin is needed to increase efforts and resource availability.