Human activities and climate change are accelerating the spread of invasive non-native species across the globe. Certain invasive species have been discovered to push lake ecosystems above a critical ‘tipping point,’ resulting in an abrupt transition from healthy to irreversible degraded conditions.

Invasive fish such as the Asian silver carp Hypophthalmichthys molitrix and crustaceans such as the American signal crayfish Pacifastacus leniusculus were shown to drastically affect the abundance of other critical organisms in lakes and affect water quality.

Additionally, the findings, which were published in the journal Global Change Biology, provide recommendations on the optimal management strategies for waterbodies.

Shallow lakes naturally exist in two stable states: healthy – with clear water and abundant flora – or ruined – with hazy water dominated by algae. When a lake reaches the latter condition, algae consume all available nutrients and block sunlight, inhibiting the formation of aquatic vegetation that is necessary for ecosystem recovery.

Degraded, algae-dominated freshwater ecosystems can pose a threat to human health and water security. Cyanobacteria blooms, sometimes known as ‘blue-green algae,’ can create toxins that pollute food webs and contaminate drinking water.

“Algal blooms represent one of the most significant threats to the security of the Earth’s surface freshwaters. Simply undoing the circumstances that triggered a tipping point will not restore the ecosystem — the road to recovery is slow and steep,” said the first author of the study Dr Sam Reynolds from the University of Cambridge’s Department of Zoology.

While invasive species are widely recognized as a serious danger to world biodiversity, their effects on ecosystem services are not always negative. Invasive molluscs, such as the zebra mussel Dreissena polymorpha, have been discovered to design the opposite biological and environmental response: they delay ecosystem collapse and may even help restore degraded lake environments.

“Managers of drinking water reservoirs, for example, may be able to avoid the cost of dealing with blooms of harmful algae, by removing invasive crayfish but allowing established non-native zebra mussels to remain and act as biological filters,” said Professor David Aldridge, sr. author of the paper.

He further added: “Early detection and rapid response plans should always be our first line of attack. But in situations where invaders have already established and can no longer be eradicated, it may be appropriate to embrace their positive effects.”

Although the researchers concentrated on shallow lake ecosystems, they believe their approach may be applied to other key ecosystems that face catastrophic tipping points, such as coral reefs, kelp forests, and desert shrublands.

Source: DOI: 10.1111/gcb.15893

Image Credit: Getty

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