James, Cassandra, Eaton, John W., and Hardwick, Keith (2006) Responses of three invasive aquatic macrophytes to nutrient enrichment do not explain their observed field displacements. Aquatic Botany, 84 (4). pp. 347-353.

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Abstract

In some eutrophic inland waters the invasive aquatic macrophyte Elodea canadensis has been displaced by the morphologically similar species Elodea nuttallii and subsequently E. nuttallii by Lagarosiphon major. We investigated whether differences in the responses of these species and their associated epiphytic floras to five nutrient loadings in the range 30–480 μg L−1 P and 0.21–3.36 mg L−1 N could explain their observed field displacements. The mean relative growth rate (RGR) of E. nuttallii (RGR 0.086 d−1) was significantly higher than that of either E. canadensis (RGR 0.066 d−1) or L. major (RGR 0.063 d−1). All three species exhibited a plastic morphological response to increasing nutrient loadings with mean root weights reduced at the highest nutrient loading compared with the lowest loading by 33, 75 and 56% for E. canandensis, E. nuttallii and L. major, respectively. Mean tissue nitrogen concentrations increased significantly with increasing nutrient loading, with concentrations in E. canadensis (1.83–2.10% dry wt.) significantly higher than either E. nuttallii (1.56–2.10% dry wt.) or L. major (1.50–1.90% dry wt.). Tissue phosphorus concentrations likewise increased with increasing nutrient loadings although this trend was not as pronounced. Epiphyte biomass per unit photosynthetic surface area (PSA) was significantly higher on E. canadensis than on either E. nuttallii or L. major, but did not increase significantly with increasing nutrient loadings. We suggest that differences in species responses to nutrient enrichment do not explain the species displacements observed in the field. E. nuttallii's higher RGR may, regardless of nutrient supply, enable this species to shade out neighbouring species and outpace the establishment of algae on its leaves.

Item ID:	85402
Item Type:	Article (Research - C1)
ISSN:	0304-3770
Copyright Information:	© 2006 Elsevier B.V. All rights reserved.
Date Deposited:	07 May 2025 23:06
FoR Codes:	31 BIOLOGICAL SCIENCES > 3103 Ecology > 310304 Freshwater ecology @ 50% 41 ENVIRONMENTAL SCIENCES > 4102 Ecological applications > 410202 Biosecurity science and invasive species ecology @ 50%
SEO Codes:	18 ENVIRONMENTAL MANAGEMENT > 1803 Fresh, ground and surface water systems and management > 180303 Fresh, ground and surface water biodiversity @ 50% 18 ENVIRONMENTAL MANAGEMENT > 1803 Fresh, ground and surface water systems and management > 180302 Control of pests, diseases and exotic species in fresh, ground and surface water @ 50%
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