Effects of wind-induced sediment resuspension on distribution and morphological traits of aquatic weeds in shallow lakes

Abstract

The spread of invasive aquatic plants (i.e., aquatic weeds) requires a broader knowledge of the factors determining their settlement at the lake scale, in order to improve management practices and biomonitoring. Among hydrodynamic pressures, wave action might influence submerged vegetation distribution in shallow lakes and potentially engender modifications of plant morphological traits. We here report a field survey conducted between 2014 and 2015 in French Atlantic Lakes to assess the spatial distribution and biomass production of two rooted aquatic weeds, Egeria densa Planch. and Lagarosiphon major (Ridl.) Moss, in relation to wind-induced sediment resuspension, water depth and sedimentary features. Moreover, we explored the relation between plant morphological traits and hydrodynamic disturbance under in situ conditions. At the lake scale, E. densa and L. major formed extensive monospecific stands, and occurred in the same areas only at low biomass. Both monospecific and mixed stands preferentially developed in shallow-sheltered or deep-exposed areas. Plant morphological traits showed different patterns in function of sediment resuspension according to the species and the lake. The influence of resuspension was however not systematic, with many cases where morphological traits were not affected at all. Maximum stem length appeared to be the most correlated trait towards sediment resuspension. Moreover, we found a significant correlation between the biomass and the sedimentary organic matter, indicating an interaction between the organic substrate preference of the plants and the effect of the canopy on fine particles sedimentation. On the whole, we highlighted the link between plant distribution, phenotypic plasticity and sediment resuspension, with calm-water zones favouring the settlement of dense vegetated stands. Our study could thus contribute to improve prediction models for identifying suitable areas for potential colonization by aquatic weeds. Further research is needed to better understand the role played by hydraulic forces in structuring the habitats in shallow lakes.

Prediction of macrophyte distribution: The role of natural versus anthropogenic physical disturbances

“…In this study, we focused on the whole macrophyte community (including common species, aquatic weeds and rare and endangered species) of two large, shallow lakes to define which physical factors influenced their distribution at the lakeshore scale. In a previous study (Bertrin et al., ) we demonstrated that wave‐induced sediment re‐suspension, together with depth, are crucial for structuring the distribution of submerged vegetation in the offshore zones of lakes. In focusing on lakeshores, we recognize here that wind effects (i.e., natural disturbances) and lake morphometry should play a major role in driving shoreline macrophyte distribution as well.…”

“…Wave‐induced sediment re‐suspension was calculated as described in Bertrin et al. () via the Wave Model (Rohweder et al., ). This model used the same fetch and wind data matrices as wave exposure measures, but it also included water depth in order to estimate the maximum orbital wave velocity.…”

“…Concomitantly, shore slope and light attenuation due to sediment re‐suspension are structuring factors for rooted macrophyte communities at intermediate depths (Chambers, ; Duarte & Kalff, ; Van Zuidam & Peeters, ). Until now, studies exploring the effects of physical forces on macrophytes have generally been based on mesocosm approaches (Doyle, ) or on field data, focusing exclusively on a specific group of plants (Bertrin et al., ; Lehmann, Castella, & Lachavanne, ; Strand & Weisner, ).…”

“…For instance, the increase of sedimentary organic matter is known to favour the substitution of isoetid communities by Juncus bulbosus in acidic freshwaters (Smolders, Lucassen, & Roelofs, ). Also, the creation of calm water areas with low wave‐induced sediment re‐suspension might favour the establishment of aquatic weeds (Bertrin et al., ). This is why it remains essential to define the habitat preferences of different plant communities at a given scale and ecological context.…”

Aquatic biomonitoring: Lessons from the past, challenges for the future

“…The available knowledge needs to be improved to better manage control and mitigation programs. For this purpose, Bertrin et al (2017) investigate the distribution patterns of alien species in the Aquitaine lakes, considering the influence of hydromorphology on plants morphological plasticity. All this information is fundamental to support effective actions.…”