BIOMONITORING SITE QUALITY IN STRESSED AQUATIC ECOSYSTEMS USINGVALLISNERIA AMERICANA

Abstract

Leaf‐to‐root surface area ratios in Vallisneria americana have been shown to provide a simple and inexpensive relative measure of sublethal effects of organochlorine contamination. The present study was conducted to determine whether this index of surface area could be used as an effective biomonitor of overall site quality in stressed aquatic ecosystems. The leaf‐to‐root surface area ratio was determined for samples of V. americana collected from 225 microsites within 12 Areas of Concern (environmentally contaminated areas designated by the International Joint Commission) throughout the Laurentian Great Lakes of Ontario. Statistical analyses indicate that 77% of the variation in the surface area index could be attributed to differences among microsites, with only 23% of variation occurring among plants within a microsite. A multiple regression equation was developed for predicting the leaf‐to‐root surface area ratio from several measures of microsite quality. Significant parameters affecting the surface area ratio included plant density, light intensity, and an index of sediment contamination. In contrast, measures of water contamination did not show any correlation with leaf‐to‐root surface area ratio. These observations support the hypothesis that V. americana accumulates contaminants primarily from the sediments and that the leaf‐to‐root surface area ratio can be used to construct contours of point source impact zones in Areas of Concern. The regression model developed here provides a simple, inexpensive means for monitoring overall site quality throughout the Great Lakes.

Aquatic Vegetation, an Understudied Depot for PFAS

“…While the main route of contaminant uptake in AV is via the roots, foliar uptake may be important for species such as V. americana , which has tall blades, extending in some locations to the water surface . Also, particle-bound contaminants in water currents may be trapped by dense leaf canopies and deposited onto the sediment, facilitating uptake by both roots and leaves. , V. americana is a salt-tolerant species, but was only collected in Wakulla Springs, a freshwater system; thus, in addition to species-specific characteristics and proximity to PFAS source sites, the effect of fresh-water, water parameters (e.g., pH, total suspended solids, dissolved organic matter), seasonality, and water flow in this water body compared to others cannot be ruled out as contributors to the increased PFAS uptake in this species.…”

“…Phytofiltration and biotransformation of PFAS may depend on the edaphic conditions in which the AV resides. For example, microbial diversity within plants, which is often more prevalent in an aerobic environment, may enhance the uptake of PFAS by some AV species through direct bacterial sorption by the microorganisms present within the plant tissue. ,− Additionally, the amount of water transpired during growth, which can be influenced by climatic conditions such as humidity, has been hypothesized to contribute to the uptake of different PFAS among varying terrestrial crops. , The emergent wetland species, S. califonicus is a marsh species that is often present with submerged roots and exposed stems. Compared to the other, fully submerged AV species, S. califonicus are emergent sedges that inhabit both an aerobic and anaerobic environment, thus possibly inhabiting a more diverse microbial community.…”

Carbon and nitrogen partitioning in the freshwater submerged macrophyte Vallisneria gigantea in response to ultraviolet-B irradiance

“…To date, little or no data on the influence of UV-B radiation on submerged freshwater macrophytes have however been collected. The genus Vallisneria (Hydrocharitaceae) is a rooted, submerged, freshwater macrophyte, which has been used as a water-quality indicator in freshwater systems (Melzer 1999;Potter and Doust 2001). Investigators have demonstrated that aquatic macrophytes play a major role in nutrient cycling of many freshwater systems (Ozimek et al 1990;Wigand et al 1997;Morris et al 2003;Huss and Wehr 2004).…”