The biological indicators of toxic substances

The impact of harmful substances on the nature of the Baltic Sea can be monitored with so-called biological and marine management indicators. Bioindicators are species of organisms that reflect the levels and effects of contaminants in their environment.

Baltic tellins (Limecola balthica).

Good bioindicators can be found from the seabed

Many stationary species of benthic fauna can be used to measure the concentrations of seabed contaminants and their impact on the food chain. Midge larvae (Chironomidae) are one of the most widely used bioindicators in seabed surveys.

Some species of chironomid midges are quite tolerant of loading from wastewater. The morphological deformities caused by harmful substances can be measured from the larvae of these midge species. Such deformities are used to assess the health status of the midge populations, as well as the toxicity of the bottom sediments.

Compared to healthy midge larvae, deformed specimens can, among other things, grow more slowly. They may also fail to mature more often than healthy larvae.

Biomarkers are studied in organisms to monitor environmental changes

Biomarkers are properties that reflect a change in the biological state of an organism. These can include changes in, e.g. molecules, cells, organisms, proteins, and hormones.

The use of bivalve molluscs as bioindicators has been extensively studied in Finnish coastal areas. Variations have been measured in the biomarkers of both Baltic tellins (Limecola balthica) and blue mussels (Mytilus trossulus) collected from the wild, as well as from blue mussels grown in cages in target areas. The biomarker changes have often been associated with the concentrations of harmful substances measured from their soft tissues.

Biomarkers have also been measured in fish

In Finland, biomarkers have also been measured in fish from different marine areas. In this way, the impact levels of harmful substances from different areas can be compared. In the Gulf of Finland, for example, remarkably high micronucleus densities have been found in the blood cells of herring, which is attributed to a genotoxin, i.e. a physical or chemical factor that causes genetic damage, such as mutations. Similarly, in the Gulf of Finland, salmon have been found to have a higher biomarker response to contaminants compared to individuals from the Bothnian Sea. Moreover, higher levels of toxins, such as dioxins and PCBs, have also been measured in salmon in the Gulf of Finland.

Addressing the effects of harmful substances at an early stage is difficult

The effects of toxic substances at different levels of the Finnish marine ecosystem are poorly known. This is because the systematic monitoring of the effects of harmful substances has been inadequate.

The lack of “early-warning alarms”, such as biomarkers, makes it difficult to quickly detect changes happening in the marine environment due to harmful substances. The consequent impacts of these hazardous materials may then become serious before sufficient research data about them are available to initiate effective protection and containment measures.