Can macrophyte harvesting from eutrophic water close the loop on nutrient loss from agricultural land?

Abstract

Eutrophication is a major water pollution issue and can lead to excessive growth of aquatic plant biomass (APB). However, the assimilation of nutrients into APB provides a significant target for their recovery and reuse, and harvesting problematic APB in impacted freshwater bodies offers a complementary approach to aquatic restoration, which could potentially deliver multiple wider ecosystem benefits. This critical review provides an assessment of opportunities and risks linked to nutrient recovery from agriculturally impacted water-bodies through the harvesting of APB for recycling and reuse as fertilisers and soil amendments. By evaluating the economic, social, environmental and health-related dimensions of this resource recovery from 'waste' process we propose a research agenda for closing the loop on nutrient transfer from land to water. We identify that environmental benefits are rarely, if ever, prioritised as essential criteria for the exploitation of resources from waste and yet this is key for addressing the current imbalance that sees environmental managers routinely undervaluing the wider environmental benefits that may accrue beyond resource recovery. The approach we advocate for the recycling of 'waste' APB nutrients is to couple the remediation of eutrophic waters with the sustainable production of feed and fertiliser, whilst providing multiple downstream benefits and minimising environmental trade-offs. This integrated 'ecosystem services approach' has the potential to holistically close the loop on agricultural nutrient loss, and thus sustainably recover finite resources such as phosphorus from waste.

Potential effects of mechanically removing macrophytes on the phytoplankton community of a subtropical reservoir

“…In contrast, macrophytes should be carefully disposed of to avoid contaminating adjacent water bodies with plant propagules or nutrients (Quilliam et al 2015), as well as to minimize the impact on the indigenous fauna associated with the macrophytes (Booms 1999;Greer et al 2012;James 2013). Depending upon the method used, the area of removal activity, and its intensity, the associated environmental changes can extend over the entire reservoir.…”

A Retrospective Environmental Assessment of the Natural Heritage of Dal Lake for Prospective Implication Scenarios

“…The vascular aquatic plants possess higher productivity (C:N and C:P ratios) with organic polymer body capacitating their slowed decomposition that improves nutrient and C capture potential and as a result net autotrophy [110]. The concurrence of peak bioaccumulation and biomass production empowers the concept of high yield harvesting [111]. The harvesting of macrophyte biomass suitably during peak growth phase is perfect to avoid nutrient and metal remobilization from belowground vegetative parts or during senescence leaching on ultimate OM mineralization [112].…”

Classifying nuisance submerged vegetation depending on ecosystem services

“…Furthermore, submerged macrophytes themselves often show a patchy distribution in aquatic ecosystems and activities could thus be allocated towards the sites with fewer plants. If the underlying causes of nuisance submerged macrophyte growth cannot be removed, harvesting nuisance aquatic plants may be a suitable management method to temporarily alleviate local problems (Quilliam et al 2015;Finlay and Vogt 2016;Hussner et al 2017). An additional advantage of this method is that it removes nutrients that are incorporated in the plant biomass from the ecosystem, which can be used for a wide variety of useful applications, for example as agricultural fertiliser or food for cattle (Edwards 1980;Quilliam et al 2015).…”