Differences in pressures impacting the Nordic seas

Direct evidence of the negative impacts of anthropogenic pressures on marine ecosystems has accumulated over decades of research in the Nordic marine areas. Evidence of the pressure impacts on marine species populations, seabed and plankton communities is strong. The pressures can be divided according to their:

These three factors cause very different end-results in the marine environment. For instance, the very severe impact from dredging on the benthic flora and fauna is limited to a relatively small area outside the activity and hence its overall significance in a regional scale is not high. In contrast, discharges of nutrients and hazardous substances to the marine environment do not cause acute impacts but their spatial extent is very wide, and the pressure remains in the system for a long time. These two pressures are assessed as the main problems in the Baltic Sea.

HELCOM (2023) HELCOM Thematic assessment of spatial distribution of pressures and impacts 2016–2021. Baltic Sea Environment Proceedings No. 189.

The pressure duration is a significant factor from a management point of view; pressures that disappear from the system quickly, e.g. underwater noise from human activities, will not pose long-term impacts that are complicated to mitigate in future.

The most severe impacts can be expected from pressures that spread wide and last long in the environment. Substance flows – nutrients, organic matter, hazardous substances or microlitter – from the catchment area have the potential to be widespread and longlasting if the receiving sea area is limited by depth or water exchange such as the Baltic Sea or any fjords or bays of similar geography.

The greatest pressures in the Baltic Sea marine environment are inputs of nutrient and organic matter causing eutrophication and hazardous substances¹⁶. These are also recognized as the main pressures that prevents the good ecological status under the EU Water Framework Directive (WFD) in the Baltic Sea coastal waters.

Laamanen et al. (2021) Impacts on seabed: Approaches for assessment as step towards successful measures. HELCOM ACTION report. Available at: https://helcom.fi/helcom-at-work/projects/action/

As the management advice to input of nutrients and hazardous substances is well known in the Baltic Sea, this report does not focus on these. In addition to the HELCOM nutrient reduction targets, other quantitative evidence exists of the adverse effects of eutrophication-related pressures (e.g. oxygen, turbidity, suspended solids).

Virtanen et al. (2018). Task 4.2.1 Definition of adversely affected habitats. HELCOM SPICE. Available from https://helcom.fi/helcom-at-work/projects/spice/

Severe impacts caused by anthropogenic pressures are also called acute impacts.

Goodsir et al. (2015) A spatially resolved pressure-based approach to evaluate combined effects of human activities and management in marine ecosystems. ICES Journal of Marine Science72: 2245–2256.

Table 1 provides a summary of human activities causing severe impacts. The summary is from a review covering 446 impact estimates from130 published studies.

Korpinen et al. (2018) Estimating physical disturbance on seabed – Baltic Sea Environment Proceedings No. 164.

Most of the activities listed in Table 1 are spatially limited, but some of the activities are both acute/severe and widely spread. These are towed fishing gears (trawls, seines and longlines) and maritime traffic.

Table 1. Human activities causing severe and acute impacts on marine ecosystem. Modified from Korpinen et al. 2018 (Estimating physical disturbance on seabed – Baltic Sea Environment Proceedings No. 164).