Seasonal dynamics of the macrophyte test species Myriophyllum spicatum over two years in experimental ditches for population modeling application in risk assessment

• Published in: Integrated environmental assessment and management 2022-09, Vol.18 (5), p.1375-1386
• Main Authors: Arts, Gertie H. P., Smeden, Jasper, Wolters, Marieke F., Belgers, J. Dick M., Matser, Arrienne M., Hommen, Udo, Bruns, Eric, Heine, Simon, Solga, Andreas, Taylor, Seamus
• Format: Article
• Language: English
• Subjects: Aquatic ecosystems; Aquatic plants; Baskets; Biomass; Ditches; Dry weight; Dynamics; Ecosystem management; Ecosystems; Environmental assessment; Environmental factors; Environmental Impact Assessment; Environmental management; Field experiment; Freshwater; Freshwater ecology; Freshwater ecosystems; Geographical distribution; Growth rate; Inland water environment; Integrated environmental assessment; Meteorological data; Model parameters; Model testing; Myriophyllum spicatum; Parameters; Pesticides; Population; Population dynamics; Risk assessment; Seasonal variations; Sediment; Shoots; Standing crop; Toxicology; Variability; Water temperature
• ISSN: 1551-3777; 1551-3793
• DOI: 10.1002/ieam.4553

Myriophyllum spicatum is a sediment‐rooted, aquatic macrophyte growing submerged, with a wide geographical distribution and high ecological relevance in freshwater ecosystems. It is used in testing and risk assessment for pesticides in water and sediment. Population models enable effects measured under laboratory conditions to be extrapolated to effects expected in the field with time‐variable environmental factors including exposure. These models are a promising tool in higher‐tier risk assessments. However, there is a lack of data on the seasonal dynamics of M. spicatum, which is needed to test model predictions of typical population dynamics in the field. To generate such data, a two‐year study was set up in outdoor experimental systems from May 2017 to May 2019. The growth of M. spicatum was monitored in 0.2025 m2 plant baskets installed in an experimental ditch. Parameters monitored included biomass (fresh weight [FW] and dry weight [DW]), shoot length, seasonal short‐term growth rates of shoots, relevant environmental parameters, and weather data. The results showed a clear seasonal pattern of biomass and shoot length and their variability. M. spicatum reached a maximum total shoot length (TSL) of 279 m m−2 and a maximum standing crop above‐ground DW of 262 g m−2. Periodical growth rates reached up to 0.072, 0.095, and 0.085 day−1 for total length, FW, and DW, respectively. Multivariate regression revealed that pH (as a surrogate for the availability of carbon species) and water temperature could explain a significant proportion of the variability in M. spicatum growth rates (p