Changes in N and P limitation induced by water level fluctuations in Nature Park Kopački Rit (Croatia): nutrient enrichment bioassay

Abstract

The importance of nutrients as limiting factors might vary in environments with different limnological characteristics. In this article we evaluate the effect of frequency and duration of flooding on nutrient limitation in a riparian floodplain. Variations in N and P limitations were studied in the period of low (2003) and high (2004) water level in two different floodplain habitat types in the Nature Park Kopački Rit (Croatia), a floodplain area of the Danube River. In 2003 and 2004, the limnological characteristics of floodplain lake (Lake Sakadaš) and the channel (Stara Drava) differed due to their hydrological regimes. Potential for nutrient limitation was determined by DIN:TP and TN:TP ratios, while the actual nutrient limitation was assessed by nutrient enrichment bioassay. A change from non-limited to N-limited conditions in the channel, and consistent actual N limitation in the lake was determined by the nutrient enrichment experiment. Of the two ratios, DIN:TP matched better with the bioassay data. Phosphorus limitation was only occasionally evident. Changes in trophic conditions from hypereutrophy to eutrophy (between low and high water levels) reflected the importance of the hydrologic regime as a factor which can modify the trophic state of Lake Sakadaš. Compared with 2003, the increase of total nitrogen concentrations in 2004 calls attention to the importance of nitrogen inputs from the Danube to the system with excessive phosphorus concentrations.

Assessing nutrient limitation in a subtropical reservoir

“…Nutrient enrichment bioassay experiments from 30 small upland lakes in Great Britain showed a high frequency of N limitation or co-limitation at high N:P ratios (Maberly et al 2002). Similar results were reported from floodplain habitats in Croatia (Perŝić et al 2009) and a river impoundment in the United States (Bukaveckas and Crain 2002). Colimitation of N+P was also evident in nutrient enrichment bioassay experiments from Lake Tanganyika, Africa (De Wever et al 2008).…”

Abundance and Biomass Responses of Microbial Food Web Components to Hydrology and Environmental Gradients within a Floodplain of the River Danube

“…6e, f; Table 1), and a new community is then able to develop during the suceeding isolation phase. In addition to hydrology, autotrophic microbes were significantly and positively related to chemical variables loaded on the second principal component, which were similar to those reported earlier [41,46]. Hydrology and chemical variables explain just over 35 % of variability in the NPhP abundance and more than 67 % of variability in the Chl a concentration.…”

Spatiotemporal Variability in the Water Quality of Poyang Lake and Its Associated Responses to Hydrological Conditions

“…Such difference may be attributed to the river-like characteristics of the lake with relatively high velocity and amounts of suspended solid, which have substantially decreased the underwater light conditions [24]. Similar results were reported in the floodplain area of the Danube, which experiences flooding and a short water residence time [32].…”

“…The lake phase has a higher phytoplankton biomass, which is mainly attributed to the significantly higher temperature, elevated underwater light conditions, and extended water residence time [45]. An increase in phytoplankton biomass during flooding was also reported in other floodplains and shallow lakes [32,46]. However, the Chl-a concentration does not show the trend of the other nutrient indices, which further indicates that the Chl-a variations cannot be explained by the nutrients in Poyang Lake [38].…”