Erosion, phosphorus and phytoplankton response in rivers of South-Eastern Norway

Abstract

The development of P fractions and phytoplankton was studied in three rivers with varying concentrations of seston.Less than 1% of the yearly TP transport may take place during periods with high algal biomass. The observation of a high growth rate of phytoplankton in the rivers coinciding with high concentrations of RP, low content of seston and high TP:Chl a ratio, indicate that the growth was often not P-limiting. During short periods with high phytoplankton biomass the ratio TP:Chl a may be low, indicating that a high fraction of TP was available.The content of P in soil samples and in samples with high seston content was about 0.1% of dry weight, and the algal availability of P often varied between 25 and 75% of TP for both types of samples.Decreasing biomass or low growth rates were observed at secchi depths less than 0.5 m and seston concentrations less than about 25 mg dry weight 1 -'. High flow rate also depressed the development of the total phytoplankton biomass. The assimilation of available P is incomplete under such conditions, i.e. under conditions of light limitation and high dilution rate.The availability of P for phytoplankton in rivers with different length, light conditions and stream velocity is discussed.

Phosphorus transfer from agricultural areas and its impact on the eutrophication of lakes—two long-term integrated studies from Norway

“…Furthermore, not only the dissolved P contributes to eutrophication, since when the stream water enters a lake, the particulate P (PP) in the SS of the stream water begins to re-equilibrate with the standing water's dissolved P (Correll, 1998). Hence, much of the PP inputs become available to the phytoplankton and bacteria (Krogstad and Løvstad, 1989;Ekholm, 1994;Reynolds and Davies, 2001). Haraldsen et al (1995) described the regional differences in P loss processes and concluded that erosion and related losses of PP were the most important process of P loss on arable land in south-eastern Norway, while losses of dissolved P related to manure application and point sources were more important in the south-western part of the country where livestock density is generally high.…”

Eutrophication mitigation in rivers: 30 years of trends in spatial and seasonal patterns of biogeochemistry of the Loire River (1980–2012)

“…Surface water quality is also affected by variations in hydro-climatic conditions (Durance and Ormerod, 2010) and nutrient availability is not the only limiting factor of phytoplanktonic growth in rivers: successful phytoplankton species in rivers are selected based on their ability to survive high-frequency irradiance fluctuations and the important determinants are turbidity (or its impact upon underwater light) and water residence time (Istvánovics and Honti, 2012;Krogstad and Lovstad, 1989;Reynolds and Descy, 1996;Reynolds et al, 1994). In Europe, both climatic models and observations have shown a general rise in air and water temperature since the 1970s (Moatar and Gailhard, 2006;Whitehead et al, 2009;Bustillo et al, 2013), and models predict lower water discharge and rising temperatures during summer, potentially intensifying the risk of eutrophication (Arheimer et al, 2005;Barlocher et al, 2008;Lecerf et al, 2007;Whitehead et al, 2009) as shallow rivers are particularly susceptible (Istvánovics et al, 2014).…”

Meteorological influences on algal bloom potential in a nutrient‐rich blackwater river

“…, 2004). The influence of factors like residence time on phytoplankton dynamics can be particularly pronounced in lotic ecosystems because of large shifts in flow rates related to changes in rainfall in the catchment (Jones, 1984; Soballe & Kimmel, 1987; Reynolds, 1988; Krogstad & Lovstad, 1989; Pace, Findlay & Lints, 1992). While Basu & Pick (1996) highlight the importance of nutrient availability in defining phytoplankton biomass potential in rivers, the achievement of that potential can be strongly influenced by other considerations, such as water residence time, light availability and grazing loses.…”

“…Several researchers have stressed the importance of water residence time in defining the relationships between nutrient status and phytoplankton standing crops in rivers (Vannote et al. , 1980; Jones, 1984; Soballe & Kimmel, 1987; Reynolds, 1988; Krogstad & Lovstad, 1989; Pace et al. , 1992).…”