. 2021 Jan 12;67(5):901–919. doi: 10.1007/s00267-020-01404-3

Table 9.

Number of references (ref) per coding theme across newspaper articles (art) on quagga mussel

	Reference frequency	Content of references
Governmental action	26 ref. 20 art.	– Experiments using the mussel to filter water bodies. E.g., Brabantse delta water authority doing tests in a pond in Breda, and Amstel, Gooi and Vecht water authority constructing a “quagga filter” in the Sloterplas – Ministry of Economic Affairs stimulating experiments with the mussel to filter water – Monitoring of the distribution of the mussel, and research into the damage it can do, e.g., to sluices – EU regulation and plans regarding invasive alien species, among which the quagga mussel – 2017 International Maritime Organization Ballast Water Management Convention making treatment of ships’ ballast water obligatory
Governmental inertia	9 ref. 9 art.	– Water authorities have not responded to the appearance of the mussel for 5 years – Water authorities are struggling with the ambivalence about the impacts of the mussel
Community action	8 ref. 8 art.	– A dive center sinks Christmas trees to the bottom of the Reeuwijkse Plassen so quagga mussels will attach to them and improve visibility – Monitoring the presence of mussels in Amsterdam harbor or the province of Zeeland – Lectures and exhibitions on invasive alien species, among which the mussel
Community inertia	2 ref. 2 art.	– Arguing that the mussel is spreading too fast to contain
Negative impacts	31 ref. 27 art.	– Filtering activity reduces presence of plankton, negatively affecting other species – Reduction of fish means fewer sightings for divers – Clearer water increases plant growth because of more light infiltration – Adhering to surfaces such as electricity plant discharge pipes, boats, and docks – Outcompeting native mussel species, which has repercussions for native fish
Positive impacts	54 ref. 47 art.	– Filtering results in clearer water, which increases light availability – More available light boosts the growth of water plants and algae, which attracts birds and fish – Filtering is generally assumed to reduce the occurrence of cyanobacteria, benefiting swimming conditions for humans
Ambiguous impacts	13 ref. 9 art.	– The filtering capacity results in clear water, but also decreases the presence of plankton, which benefits some species but harms others – Does the mussel indeed decrease the presence of the cyanobacteria? – What will the long-term effects be?

Reference frequency

Content of references

Governmental action

26 ref.

20 art.

– Experiments using the mussel to filter water bodies. E.g., Brabantse delta water authority doing tests in a pond in Breda, and Amstel, Gooi and Vecht water authority constructing a “quagga filter” in the Sloterplas

– Ministry of Economic Affairs stimulating experiments with the mussel to filter water

– Monitoring of the distribution of the mussel, and research into the damage it can do, e.g., to sluices

– EU regulation and plans regarding invasive alien species, among which the quagga mussel

– 2017 International Maritime Organization Ballast Water Management Convention making treatment of ships’ ballast water obligatory

Governmental inertia

9 ref.

9 art.

– Water authorities have not responded to the appearance of the mussel for 5 years

– Water authorities are struggling with the ambivalence about the impacts of the mussel

Community action

8 ref.

8 art.

– A dive center sinks Christmas trees to the bottom of the Reeuwijkse Plassen so quagga mussels will attach to them and improve visibility

– Monitoring the presence of mussels in Amsterdam harbor or the province of Zeeland

– Lectures and exhibitions on invasive alien species, among which the mussel

Community inertia

2 ref.

2 art.

– Arguing that the mussel is spreading too fast to contain

Negative impacts

31 ref.

27 art.

– Filtering activity reduces presence of plankton, negatively affecting other species

– Reduction of fish means fewer sightings for divers

– Clearer water increases plant growth because of more light infiltration

– Adhering to surfaces such as electricity plant discharge pipes, boats, and docks

– Outcompeting native mussel species, which has repercussions for native fish

Positive impacts

54 ref.

47 art.

– Filtering results in clearer water, which increases light availability

– More available light boosts the growth of water plants and algae, which attracts birds and fish

– Filtering is generally assumed to reduce the occurrence of cyanobacteria, benefiting swimming conditions for humans

Ambiguous impacts

13 ref.

9 art.

– The filtering capacity results in clear water, but also decreases the presence of plankton, which benefits some species but harms others

– Does the mussel indeed decrease the presence of the cyanobacteria?

– What will the long-term effects be?