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Establishing ecological assessment schemes is challenging when gradients are short and there are no sites with minimal anthropogenic alteration against which metrics can be calibrated. This is the situation for large rivers in Romania and this paper describes efforts to establish meaningful ecological status concepts. The intercalibration exercise, conducted as part of Water Framework Directive (WFD) implementation, has provided a metric ("phytobenthos Intercalibration Common Metric", pICM) which allows ecological status in different countries to be expressed on a common scale. The average boundary positions of countries who participated in this exercise provided a "common view" of status and, together with pICM, offer an "off-the-shelf" solution for countries unable to develop independent methods. However, even when expressed as pICM, Romanian phytobenthos data have a weak relationship with nutrients. Analysis of chemical data and comparison with similar data from elsewhere in Europe confirm that there are few sites with significantly elevated nutrient concentrations. Incorporation of the Romanian data into the larger dataset produced a stronger relationship from which the status of phytobenthos in very large rivers in Romania could be confirmed. This paper shows how the consensus that emerged from the WFD intercalibration exercise supports those countries unable to participate in the initial exercises. [ABSTRACT FROM AUTHOR]

The present paper aims to characterize the algal communities from Balta Mică a Brăilei Nature Park in terms of their species richness and their ability to reflect the water quality of the aquatic ecosystems they live in. Thirteen shallow floodplain lakes, both permanent and temporary, were considered for the present study, with 16 sampling occasions in 2012 and 2013. More than 300 algal taxa were identified, with the green algae (Chlorophyta) being the dominant phyla in almost all the sampling sites. The trophicity and the organic pollution reached high values in 2012, probably due to low water levels caused by drought. Spring floods from 2013 led to lower trophicity and saprobity levels in all sampled water pools. [ABSTRACT FROM AUTHOR]

• Phytobenthos in lowland lakes in Romania does not demonstrate a strong response to phosphorus. • Assemblage composition is, instead, determined by biochemical oxygen demand and conductivity. • A new metric to evaluate ecological status using phytobenthos in these lakes is described. • Expected values of this metric are derived from a quantile regression of the index against conductivity. • As conductivity is susceptible to climate change, 2010 values are used as benchmarks when calculating expected index values. In contrast to diatom assemblages in lakes in most other parts of Europe, those in lowland lakes in Romania appear to be determined primarily by biochemical oxygen demand (BOD) and conductivity rather than by nutrients. This has confounded the development of a Water Framework Directive-compatible phytobenthos assessment system for Romanian lakes and led, instead, to the development of a new metric, the Romanian Diatom Index (RDI), which captures these gradients. The primary anthropogenic stressor is assumed to be BOD whilst conductivity is a product of background geology and climate. The RDI is strongly correlated with BOD, and ecological quality ratios (EQRs) are computed by dividing the observed RDI by an expected value, determined from the 90th percentile of the relationship between RDI and conductivity. This equates to the "best available" RDI at any point on the conductivity gradient and, in the absence of true "reference sites", has been assumed to represent the boundary between high and good status. The boundary between good and moderate status has been set at the point where the sum of valves of taxa tolerant to elevated BOD exceeds the sum of valves of taxa that are sensitive to elevated BOD. The position of this boundary has been further validated by the use of a Threshold Indicator Species Analysis (TITAN). In view of the susceptibility of conductivity to climate warming, 2010 values of conductivity have been used to ensure a stable benchmark against which future changes can be measured. This study highlights the challenges involved in performing reliable ecological assessments in situations that are, by the standards of much of Europe, atypical. [ABSTRACT FROM AUTHOR]