Data for "Trait-specific groups of aquatic macrophytes respond differently to eutrophication of unshaded lowland streams"

Description

This dataset contains information on 30 streams located on the North Island in Aotearoa New Zealand. The dataset comprises quantification of plant communities in the streams as well as physicochemical parameters acquired in-situ and from national databases. Please read the abstract from the accompanying paper below: Understanding eutrophication effects on stream macrophytes is key to meaningful environmental management and governance. However, the response of macrophyte communities to eutrophication is complex and often the effect of eutrophication is obscured by habitat variability. In this study we quantified macrophyte community composition and abundance along a eutrophication gradient in 30 lowland streams. We selected slow flowing, medium sized streams with minimal shading, to focus on examining water quality effects. We measured the internal nutrient status of the plants and the bioavailable nutrient fraction of the sediment and used a national database of modelled stream descriptors to obtain information about land use and other water quality variables. We statistically examined relationships between macrophyte community composition and abundance and nutrient, underwater light, carbon availability and disturbance along the eutrophication gradient. We found that macrophytes with different growth strategies were related to different aspects of eutrophication. An increased abundance of submerged species was associated with elevated water column phosphorus (P) and alkalinity, while increased abundance of emergent species was associated with high sediment P, nitrate (N) and low disturbance. We did not find a relationship between nutrient inputs and nutrient content of the macrophytes but did find that sediment P correlated with P inputs to streams. We also observed that non-native taxa dominated eutrophic streams. Our results indicate that 1) non-native species are common in unshaded lowland streams with low water clarity and high nutrient and bicarbonate availability; 2) emergent species are associated with high nitrogen availability and suspended sediment and 3) submerged species prevail where phosphorus and bicarbonate availability is high. Our findings improve understanding of how stream macrophyte communities respond to changes in water quality related to eutrophication and anthropogenic changes in catchments and will contribute to an informed management of macrophytes in streams. For method details please see the paper.

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