Environmental quality assessment in estuarine ecosystems: use of biometric measurements and fecundity of the ragworm Nereis diversicolor (Polychaeta, Nereididae).

The ability to cope with environmental stress may be expensive in terms of energy and this cost of tolerance is suspected to have negative counterparts such as reduced growth and fecundity. To date, condition indices based on biometric measurements are currently used in bivalves or fish but do not exist in endobenthic worms, despite their interest as bioindicators for the sedimentary compartment in which the major part of pollutants is stored in aquatic environments. In the present work, several biometric variables (jaw and total body length, number of segments, the length of the first three segments L3, wet or dry weight) were measured in the ragworm Nereis diversicolor originating from clean (Authie) and polluted (Seine) estuaries (France) to study size-weight relationships. The production of oocytes by females (which represent 80-90% of the population) was quantified in the same specimens. In females from the polluted site, the condition was shown to be altered and, in parallel, the production of oocytes was lower than in females from the comparatively clean site. From an operational point of view, we recommend the use of the length L3 and the wet weight. Because fecundity is mainly dependent on size and weight in N. diversicolor, biometric measurements would be useful tools for assessing the biological quality of estuarine sediments.

Biomonitoring in a clean and a multi-contaminated estuary based on biomarkers and chemical analyses in the endobenthic worm Nereis diversicolor.

Relationships between biochemical and physiological biomarkers (acetylcholinesterase [AChE], catalase, and glutathione S-transferase [GST] activities, thiobarbituric acid reactive substances, glycogen, lipids and proteins) and accumulated concentrations of contaminants (polychlorinated biphenyls [PCBs], polycyclic aromatic hydrocarbons and metals) were examined in the keystone species Nereis diversicolor. The chemical analyses of worms and sediments allowed the designation of the Seine estuary and the Authie estuary as a polluted and relatively clean site respectively. Worms from the Seine estuary exhibited higher GST and lower AChE activities. Generally, larger worms had higher concentrations of energy reserves. Principal component analyses clearly highlighted intersite differences: in the first plan, GST activities and chemical concentrations were inversely related to concentrations of energy reserves; in the second one, PCB concentrations and AChE activity were inversely related. Depleted levels of energy reserves could be a consequence of combating toxicants and might predict effects at higher levels of biological organization. The use of GST and AChE activities and energy reserve concentrations as biomarkers is validated in the field in this keystone species.

From biomarkers to population responses in Nereis diversicolor: assessment of stress in estuarine ecosystems.

Suborganismal responses to toxicants can be sensitive tools to assess marine pollution, but their ecological significance is a matter of debate. Among these biomarkers, those linked to reproduction are most probably related to populational effects. To test this hypothesis, Nereis diversicolor were collected in the multipolluted Seine estuary and the comparatively clean Authie estuary (France). Energy reserves were higher in Authie worms, suggesting a better physiological status. The number of oocytes per female was higher for the polychaetes from the Authie, but it was related to the size of animals, which was higher at this site. Densities of worms were depleted in the Seine compared to those in Authie. Demographic structure of the Seine population was also altered. The concomitant changes in energy reserves, egg production, and population structure and density suggest that the effects on biomarkers and at the population level are related.