Responses of lake macrophyte beds dominated by Eurasian watermilfoil (Myriophyllum spicatum) to best management practices in agricultural sub-watersheds: Declines in biomass but not species dominance

Phosphorus fractionation in soil and sediments along a continuum from agricultural fields to nearshore lake sediments: Potential ecological impacts

“…Considering the Al-P phase to be relatively stable chemically (Rydin, 2000), the reduction in both Al-P concentration and percent of TP between field soil and lake sediments suggests a physical process by which fine silt and clay eroding from the watershed soils is sorted, remained in suspension (Walling et al, 2001;, and is likely deposited in deeper portions of the lake. However, the influence of a large macrophyte bed just north of the stream outlet (Bosch et al, 2009b) is to seasonally act to trap fine silt and clay particles (Li et al, 2007). If reduced growth of the macrophyte beds continued (Bosch et al, 2009b), the ability of the beds to trap P-rich fine particles will be reduced as well and reinforces the decline in growth of macrophytes.…”

“…However, the influence of a large macrophyte bed just north of the stream outlet (Bosch et al, 2009b) is to seasonally act to trap fine silt and clay particles (Li et al, 2007). If reduced growth of the macrophyte beds continued (Bosch et al, 2009b), the ability of the beds to trap P-rich fine particles will be reduced as well and reinforces the decline in growth of macrophytes.…”

“…This suggests that while Fe-P may be solubilized from the sediment, its contribution alone to the water column is not sufficient to support metaphyton growth. Despite reductions in phosphorus from the watershed within 2 years of establishing BMPs Makarewicz et al, 2009), macrophyte biomass responded with a reduction in biomass but at a much slower rate than metaphyton (Bosch et al, 2009b). This lag in response to reductions in limiting nutrients from the watershed may be related to the Fe-bound P fraction contributing P to rooted macrophyte growth, delaying a response to the implemented BMPs.…”

“…This lag in response to reductions in limiting nutrients from the watershed may be related to the Fe-bound P fraction contributing P to rooted macrophyte growth, delaying a response to the implemented BMPs. Significant reductions in macrophyte growth during the last year of the study (Bosch et al, 2009b) may be the result of the decreased suspended sediment input from Graywood Gully to the lake . Li et al (2007) indicated that the macrophyte beds will sufficiently decrease water velocities enough to allow fine sediment deposition.…”

Winter application of manure on an agricultural watershed and its impact on downstream nutrient fluxes

“…A comprehensive management plan should have a contingency for unforeseen circumstances, such as weather events, which may include short-to mid-term storage capabilities for manure (Edwards et al 1997) so that the farmer can avoid any deviations from the BMP. Lastly, BMP-induced reductions of seasonal P and N losses from various Conesus Lake sub-watersheds ) have led to significant reductions in metaphyton and macrophyte populations in the nearshore zone (Bosch et al 2009a(Bosch et al , 2009b and to a reduction in fecal indicators in streams coincident with the cessation of manure application ).…”