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Genetic diversity as a basic indicator of biological diversity is extremely important for the characterization of species, for the development of conservation strategies and as an independent measure of environmental conditions. Despite the importance of Batrachium species as an indicator of the sustainability of riverine ecosystems, studies on the genetic variation of Batrachium populations are rather scarce. Therefore, it is crucial to study Batrachium species diversity and population structures to understand the status of Batrachium species and populations and provide measures for evaluating the future risk of diversity loss. Sixteen Batrachium populations were analyzed using morphological characters and molecular markers (inter simple sequence repeats [ISSRs] and trnH-psbA sequences). The study revealed agreement between these types of data in distinguishing separate groups of species found in Lithuanian rivers. Our study revealed a clonal structure and a low level of genetic diversity in most of the studied Batrachium populations. The low degree of genetic diversity, high level of genetic differentiation and low level of gene flow between populations of riverine Batrachium species in Lithuania indicated that a conservation strategy should be adopted. Long-term observations should be carried out, and the condition of Batrachium species and the impact of anthropogenic activities should be evaluated. Finally, we recommend that certain anthropogenic activities should be regulated by legislation in particular river stretches.

In this study, we focused on relatively inexpensive and commonly used fishermen class sonar in order to test its ability to detect stands of charophytes and other groups of submerged angiosperms in the shallow and turbid waters of the Curonian Lagoon. Based on the length of macrophytes, height thresholds (20 and 30 cm) were established in order to distinguish charophytes from submerged angiosperms in obtained echograms. The echograms were visually analysed by two experts. We successfully discriminated 3 echofeatures (bare bottom, stands of charophytes and submerged angiosperms), whereas angiosperms from different morphology groups could not be distinguished. Below 1 m depth, the stands of charophytes and submerged angiosperms were clearly distinguished, thus their maximum colonization depth could be delineated. The accuracy of the discrimination could be reduced by free-drifting mats of filamentous algae, resulting in the overestimation of charophytes. Our approach can be useful for the mapping of monospecific stands of submerged vegetation and could be an important additional tool for macrophyte monitoring and water quality assessment in shallow and turbid waterbodies.