Growth and Anchorage of Myriophyllum spicatum L. in Relation to Water Depth and the Content of Organic Matter in Sediment

A large body of evidence suggests that the physical and chemical characteristics of the sediment in lakes that have undergone eutrophication have been significantly altered. However, the effects of alterations in sediments on submersed macrophytes remain unknown. In this study, we present the results of an outdoor experiment that examined how the growth and anchorage of the widespread submersed macrophyte Myriophyllum spicatum L. responded to the enrichment of organic matter in the sediments and whether water depth affects these responses. We found that low levels of enrichment with organic matter (≤7%) enhanced the growth of M. spicatum. In contrast, high levels of enrichment with organic matter (from 12 to 18%) slightly inhibited its growth. Although the anchorage force of M. spicatum slightly decreased with an increase in the content of organic matter in the sediment, it was much higher than the hydraulic drag force on plants at a relatively high current velocity, indicating that the plants were unlikely to be uprooted in these sediments. The water depth did not alter the responses of growth and anchorage of M. spicatum to enrichment with organic matter. Our results suggest that M. spicatum could be a potential species to restore eutrophic lakes, since it can grow well and anchor stably in sediments with relatively high organic matter and manage low light stress.

Watercraft Decontamination Practices to Reduce the Viability of Aquatic Invasive Species Implicated in Overland Transport.

Recreational boating activities enable aquatic invasive species (AIS) dispersal among disconnected lakes, as invertebrates and plants caught on or contained within watercraft and equipment used in invaded waterbodies can survive overland transport. Resource management agencies worldwide recommend decontaminating watercraft and equipment using high water pressure, rinsing with hot water, or air-drying for up to seven days to inhibit this mode of secondary spread. There is a lack of studies on the efficacy of these methods under realistic conditions and considering feasibility for recreational boaters. Hence, we conducted experiments addressing this knowledge gap using AIS present in Ontario, namely zebra mussels (Dreissena polymorpha), banded mystery snails (Viviparus georgianus), spiny waterfleas (Bythotrephes cederstroemi), Eurasian watermilfoil (Myriophyllum spicatum), Carolina fanwort (Cabomba caroliniana), and European frogbit (Hydrocharis morsus-ranae). Washing at high pressures of 900-1200 psi removed the most biological material (90%) from surfaces. Brief (<10s) exposure to water at ≥60°C caused nearly 100% mortality among all species tested, except snails. Acclimation to temperatures from 15°C to 30°C before hot water exposure had little effect on the minimum temperature required for no survival. Air-drying durations producing complete mortality were ≥60h for zebra mussels and spiny waterfleas, and ≥6 days among plants, whereas survival remained high among snails after a week of air-drying. Hot water exposure followed by air-drying was more effective than either method separately against all species tested, reducing either the minimum water temperature or air-drying duration necessary. These findings can inform best management strategies against AIS spread.

Comparison of generic and proprietary aquatic herbicides for control of invasive vegetation; part 3 : submersed plants

Herbicide selection is key to efficiently managing nuisance vegetation in our nation’s waterways. After selecting the active ingredient, there still remains multiple proprietary and generic products to choose from. Recent small-scale research has been conducted to compare the efficacy of these herbicides against floating and emergent species. Therefore, a series of mesocosm and growth chamber trials were conducted to evaluate subsurface applications of the following herbicides against submersed plants: diquat versus coontail (Ceratophyllum demersum L.), hydrilla (Hydrilla verticillata L.f. Royle), southern naiad (Najas guadalupensis (Sprengel) Magnus), and Eurasian watermilfoil (Myriophyllum spicatum L.); flumioxazin versus coontail, hydrilla, and Eurasian watermilfoil; and triclopyr against Eurasian watermilfoil. All active ingredients were applied at concentrations commonly used to manage these species in public waters. Visually, all herbicides within a particular active ingredient performed similarly with regard to the onset and severity of injury symptoms throughout the trials. All trials, except diquat versus Eurasian watermilfoil, resulted in no differences in efficacy among the 14 proprietary and generic herbicides tested, and all herbicides provided 43%–100% control, regardless of active ingredient and trial. Under mesocosm and growth chamber conditions, the majority of the generic and proprietary herbicides evaluated against submersed plants provided similar control.

Efficacy of florpyrauxifen-benzyl for eurasian watermilfoil control and nontarget Illinois pondweed, elodea, and coontail response

This research evaluated low concentrations and short exposure times of the recently registered aquatic herbicide florpyrauxifen-benzyl (4-amino-3-chloro-6-(4-chloro-2-fluoro-3-methoxyphenyl)-5-fluoro-pyridine-2-benzyl ester) on the target plant Eurasian watermilfoil (Myriophyllum spicatum L., hereafter referred to as EWM) as well as selectivity towards the nontarget submersed species Illinois pondweed (Potamogeton illinoensis Morong), elodea (Elodea canadensis Michx.), and coontail (Ceratophyllum demersum L.)

Community Structure and Function of Epiphytic Bacteria Associated With Myriophyllum spicatum in Baiyangdian Lake, China

Epiphytic bacteria on the surfaces of submerged macrophytes play important roles in the growth of the host plant, nutrient cycling, and the conversion of pollutants in aquatic systems. A knowledge of the epiphytic bacterial community structure could help us to understand these roles. In this study, the abundance, diversity, and functions of the epiphytic bacterial community of Myriophyllum spicatum collected from Baiyangdian Lake in June, August, and October 2019 were studied using quantitative PCR (qPCR), high-throughput sequencing, and the prediction of functions. An analysis using qPCR showed that the epiphytic bacteria were the most abundant in October and the least abundant in August. High-throughput sequencing revealed that Proteobacteria, Gammaproteobacteria, and Aeromonas were the dominant phylum, class, and genus in all the samples. The common analyses of operational taxonomic units (OTUs), NMDS, and LDA showed that the epiphytic bacterial communities were clustered together based on the seasons. The results of a canonical correlation analysis (CCA) showed that the key water quality index that affected the changes of epiphytic bacterial community of M. spicatum was the total phosphorus (TP). The changes in abundance of Gammaproteobacteria negatively correlated with the TP. Predictive results from FAPROTAX showed that the predominant biogeochemical cycle functions of the epiphytic bacterial community were chemoheterotrophy, nitrate reduction, and fermentation. These results suggest that the epiphytic bacterial community of M. spicatum from Baiyangdian Lake varies substantially with the seasons and environmental conditions.

Responses of morphological and physiological traits to herbivory by snails of three invasive and native submerged plants

Aims The submerged plant species Carolina fanwort (Cabomba caroliniana) has become a dominant invasive aquatic plant in the Lake Taihu Basin (LTB) in China. Introduced species may escape their original specialist enemies and encounter fewer enemies in their new environment. They were assumed to have suffered less herbivory than native species as they are relatively unpalatable (the enemy release hypothesis (ERH)). The objective of this study was to compare the responses of C. caroliniana with those of co-occurring native species to herbivory from native herbivores. Methods We conducted a mesocosm experiment to record the responses of C. caroliniana and two commonly co-occurring native submerged plant counterparts, water thyme (Hydrilla verticillata) and Eurasian watermilfoil (Myriophyllum spicatum), to herbivory by two native generalist gastropod snails, Radix swinhoei and Sinotaia quadrata. Plant morphological traits (total biomass, shoot/root (S/R) biomass ratio and relative growth rate (RGR)) and physiological traits (leaf total nonstructural carbohydrate (TNC), lignin, and cellulose) were recorded. Important Findings The snail S. quadrata rarely influenced the plant traits of the three submerged plants. With the increasing numbers of R. swinhoei treatments, most of the plant traits of H. verticillata and M. spicatum changed, while those of C. caroliniana showed a relatively stable fluctuation. This result indicates that C. caroliniana is more resistant to herbivory by the snail R. swinhoei, which is consistent with the ERH hypothesis. This finding indicates that herbivorous snail species contributes to the invasion of C. caroliniana, which potentially alters the species composition of submerged plants in the plant community.