Crayfish and carp among the invasive species pushing lakes towards
ecosystem collapse

Date:
October 6, 2021
Source:
University of Cambridge
Summary:
Certain invasive, non-native species can disrupt lakes to the point
of rapid ecosystem collapse, contaminating water for drinking,
aquaculture and recreation, a new study has found.



FULL STORY ========================================================================== Certain invasive, non-native species can disrupt lakes to the point of
rapid ecosystem collapse, contaminating water for drinking, aquaculture
and recreation, a new study has found.


========================================================================== Human activity and climate change are causing invasive non-native species
to spread rapidly across the globe. Researchers have found that certain invasive species can push lake ecosystems beyond a critical 'tipping
point', causing a sudden shift from healthy to degraded conditions that
is difficult to reverse.

Invasive fish such as Asian silver carp Hypophthalmichthys molitrix, and crustaceans such as American signal crayfish Pacifastacus leniusculus,
were found to significantly reduce the abundance of other important
organisms in lakes and degrade water quality. The findings, published
today in the journal Global Change Biology,also provide guidance on the
best ways to manage waterbodies.

Shallow lakes naturally exist in one of two alternative stable states:
either healthy -- with clear water with an abundance of vegetation,
or degraded - - with cloudy water dominated by algae. When a lake is
in the latter state, algae use up all the nutrients in the water and
block sunlight, preventing the growth of aquatic vegetation that would
aid ecosystem recovery.

Deteriorated, algae-dominated freshwater ecosystems also threaten the
health and water security of human populations. Blooms of cyanobacteria,
known as 'blue-green algae' can produce toxins that contaminate food
webs and poison water supplies.

"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 Dr Sam
Reynolds in the University of Cambridge's Department of Zoology, first
author of the report.

However, although invasive species are recognised as a significant
threat to global biodiversity, their impacts on ecosystem services may
not be uniformly negative. Invasive molluscs, including the zebra mussel Dreissena polymorpha, were found to engineer the opposite biological and environmental response: they delay ecosystem collapse and potentially
aid the recovery of degraded lake ecosystems.

"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,
senior author of the report.

He 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." The researchers focused on shallow
lake ecosystems, but say that their framework could be applied to other critical ecosystems that experience catastrophic tipping points --
such as coral reefs, kelp forests and desert shrublands.

========================================================================== Story Source: Materials provided by University_of_Cambridge. The original
text of this story is licensed under a Creative_Commons_License. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Reynolds, S. A. & Aldridge, D. C. Global impacts of invasive
species on
the tipping points of shallow lakes. Global Change Biology,
October 2021 DOI: 10.1111/gcb.15893 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211006203601.htm

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