Verifying the usefulness of macrophytes as an indicator of the status of small waterbodies.
Small waterbodies are characterised by a high variability of physicochemical parameters. This has an impact on aquatic macrophytes, which are functional components of aquatic ecosystems that also exert a strong influence on other components of these ecosystems. Therefore, their importance in the classification of reservoirs is unquestionable. Unfortunately, the hydromacrophytes found in nutrient-rich small waterbodies in rural areas have a fairly wide ecological scale and are not suitable for a more accurate assessment of these reservoirs. In addition, indicators derived from the classification of lakes, such as phosphorus, nitrogen, chlorophyll-a, organic matter and trophic state indices, have turned out to be of little use in the assessment of small waterbodies. Only a canonical analysis taking into account both environmental variables and the occurring plant species allows satisfactory results to be obtained. Six small waterbodies located in the rural landscape of the Greater Poland Region were studied over three years. 115 plant taxa, 15 of which are hydromacrophytes, were found in the reservoirs and in their immediate vicinity. Three types of small waterbodies were identified in the CCA assessment: (i) those with high TOC, COD and ammonium nitrogen contents, dominated by pleustophytes, and in a saprotrophic state, (ii) those with high nutrient concentrations, dominated by phytoplankton, with a lack of macrophytes or with nymphaeids present, and in a hypereutrophic state, and (iii) those dominated by submerged macrophytes with low chlorophyll-a content, and in a eutrophic state. Thus, macrophytes turn out to be good indicators which support other variables in the classification of small waterbodies.