Hazardous Substances Thematic Assessment

The impact on ecosystem services from current levels of hazardous substances in the OSPAR Maritime Area

There is evidence that current levels of hazardous substances impact the reproduction of sea mammals to a smaller or larger degree, and several European sea mammal populations may become extinct. This affects several ecosystem services. At the more local scale, several fish populations are too contaminated for human consumption.  

Environmental impacts:

The pressures from human activities collectively contribute to the presence of hazardous substances in sediments and biota and lead to measurable , either when measured directly as a or through contaminant concentration levels in biological tissues and comparison with an Environmental Quality Standard (EQS) value where no effects on or are expected:

• Hormonal and behavioural changes due to hormonal/ chemical imbalance: In marine mammals, PCBs show toxic effects such as immunosuppression, endocrine disruption, reproductive impairment and reduced lifespan.  
• Reduced species fitness is a general trait of poisoning, as the body of the marine organism tries to counter the toxic effect of the contaminant, thereby reducing the energy available for ordinary functions like feeding, growth and reproduction. Examples are PAH in fish, which have a metabolic system that transforms the PAHs to a less toxic form that can be more readily excreted (PAH, PCB and dioxins are known to be detoxified by fish via the EROD system (7-ethoxyresorufin O-deethylase activity). Other biological and physical factors like species, sex, reproductive status, season and environmental temperature can also affect the EROD system. In shellfish, the glutathione sulfhydryl transferase (GST) enzyme is activated by PCBs to reduce toxicity by removing chlorine. In fish blood, detoxification of lead increases the production of ALA-D (δ-aminolevulinic acid dehydratase).
• Reduced breeding success: The effects of organotins on female marine snails, measured as imposex, impede breeding success as the ovaries become increasingly blocked; for the most sensitive species the end-point is sterility. In live breeding Eelpouts, fry in the womb have been seen to have a higher fraction of malformation with higher doses of a wide range of contaminants.
• Mortality is observed for many contaminants at high concentrations. Acute toxicity in water is expressed as LD50, where 50% of the most sensitive species dies from exposure to the contaminant. Biota EQS values are set on the basis of sub-lethal effects (EC10 or NOEC), with an additional assessment factor to take into account that a limited set of species has been tested. Acute toxicity usually occurs at much higher concentration levels than the EQS thresholds and is thought to be relatively uncommon.

The environmental impacts from hazardous substances also exert pressure on ecosystem services (ES), with important implications for human welfare, by impacting negatively on economic sectors such as recreation, tourism, fisheries and aquaculture and inflicting economic losses on individuals, enterprises and communities.

Impact on ecosystem services through decline or extinction of marine populations

The most obvious instance of hazardous substances causing the extinction of marine organisms is the effect of This has led to the extinction of dog whelk in large parts of the Southern North Sea. Although has decreased greatly, this species has still not recovered in many areas, and this affects the entire ecosystem (e.g., bird populations). Another example is the effect of PCBs on marine mammals. Again, pollution by this class of contaminants has decreased greatly in sediments and in the lower trophic levels of the food web, but is stable or increasing in many . As a result, the killer whale populations of the Canary Islands, Greenland, the Strait of Gibraltar, and the United Kingdom are at high risk of collapse over the coming 100 years (Desforges et al., 2018). In both cases, a significant component of the ecosystem is lost, affecting the regulation and maintenance of marine food webs negatively. For most marine populations, for example most fish stocks, there is no hard evidence that hazardous substances contribute to population decline. However, in most of the OSPAR area, are known to be high enough to have . Also, little is known about the mixture effects (simultaneous exposure to a multitude of hazardous substances) and population fitness effects  arising from sub-lethal doses of contaminants,  i.e., the behavioural effects of pharmaceuticals (Orive et al., 2022). 

Impact on harvesting for commercial or leisure purposes

In many localised areas (fjords, bays, and estuaries) the concentrations of toxins (especially mercury and PCBs) in fish and seafood are too high for human consumption, and it is illegal to sell locally caught fish. This impacts local businesses. In other cases, selling local fish is allowed but the food authorities advise part of the population (e.g., pregnant women) not to eat local seafood. This may also affect commercial fishing, as well as have a negative impact on cultural services: the existence of official advice against eating local fish may lead to a feeling of loss of natural heritage because the ecosystem no longer appears pristine and clean.
Other possible, but uncertain, impacts on ecosystem services:

• Water quality regulation: Lethal and/or sub-lethal effects related to hazardous substances can impair to varying degrees the ability of marine ecosystem components to provide water quality regulation, for example through the death of components such as reefs, and the death of or adverse effects on invertebrate organisms such as mussels, given their contribution to water filtration.
• Sediment quality regulation: Lethal and/or sub-lethal effects related to hazardous substances can impair to varying degrees the ability of marine ecosystem components to provide sediment quality regulation, for example through the death of components such as reefs, and the death of or adverse effects on invertebrate organisms such as mussels, given their contribution to water filtration.
• Nursery population and habitat maintenance: Hazardous substances exert  mainly negative impacts on the provision of this service by affecting species of biodiversity importance, such as corals, biogenic reefs, sand eels, and those of commercial importance, such as lobster, crab, cod and mackerel, leading to changes in the assemblages of such species (e.g., more short-lived species).
• Coastal protection: Considering the contribution of biotic elements such as coral reefs, microphytobenthos, kelp forests and infauna to processes such as erosion control, and thus to coastal protection, their degradation and possible death as a result of exposure to or ingestion of hazardous substances potentially compromise the provision of this ecosystem service.
• Global climate regulation: Marine ecosystems help to regulate the chemical composition of the atmosphere and the ocean, affecting the local and global climate through the accumulation and retention of carbon dioxide and other GHGs (e.g., methane, nitrous oxide).