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The Plymouth Student Scientist

Document Type

Biological and Marine Sciences Article

Abstract

Freshwater ecosystems cover only three percent of the Earth’s surface yet support approximately ten percent of global biodiversity. These systems play a crucial role in maintaining native biodiversity across spatial and temporal scales but are increasingly threatened by anthropogenic stressors, including habitat modification, pollution, and biological invasions. The introduction of non-native macrophytes can fundamentally alter community structure by modifying habitat complexity, resource availability, and competitive interactions. This study assesses the impact of the invasive macrophyte Crassula helmsii on macroinvertebrate assemblages at small spatial scales within partially invaded ponds in Dartmoor National Park, southwest England. Three ponds with varying degrees of invasion were selected, macroinvertebrate samples were collected along with percentage macrophyte coverage. Whilst overall macroinvertebrate species richness did not differ significantly between areas dominated by Crassula helmsii and those containing only native macrophytes, multivariate analyses revealed that differences in assemblage structure were driven by a subset of taxa, notably the invasive gastropod, Physella acuta, and Hydroporus diving beetles. PERMANOVA analysis indicated subtle shifts in community composition, suggesting that the degree of Crassula helmsii invasion influences macroinvertebrate distribution patterns at small spatial scales. The displacement of native macrophytes by Crassula helmsii may have long-term implications for ecosystem functioning, with potential cascading effects on higher trophic levels. Given the challenges associated with Crassula helmsii management and eradication, further research is needed to assess its ecological role across multiple spatial and temporal scales, particularly in relation to habitat structure and ecosystem resilience in lentic freshwater systems.

Publication Date

2025-12

Publication Title

The Plymouth Student Scientist

Volume

18

Issue

2

ISSN

1754-2383

Deposit Date

2025-12

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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