Dynamics of emergent macrophytes for 50 years in the coastal Lake Engure, Latvia
Coastal Lake Engure is a Ramsar site — a wetland of great importance due to its biological diversity and unique properties, especially its coverage of macrophytes, shallowness and size. This study assesses the dynamics of emergent macrophytes in the lake based on analysis of historical aerial photographs and digital orthophoto maps. The area of emergent macrophytes was shown to have increased by 781 ha (15 ha/year) in the period 1956 to 2007. The expansion rate differed during this period. Expansion was much faster (31 ha/year) from 1956 to 1972, but declined to 6 ha/year from 1972 to 1994 and increased again to 11 ha/year from 1994 to 2007. The greatest rates of expansion of emergent macrophytes from 1956 to 1972 can be partly explained by ceased grazing and hay harvesting activities. As the area covered by emergent macrophytes changes seasonally, only remote sensing materials acquired during the same season should be compared. The open water territory in 2007 was only 22.9 km2, compared to 30.7 km2 in 1956. Emergent vegetation has been mostly limited to areas where the depth does not exceed 0.5 m. Expansion of emergent vegetation was found to differ in various parts of the lake. The main factors affecting the rates of its development were wave disturbances, hydrological regime and ceased agricultural activities in the lake.
The non-selective, post-emergence herbicides based on glyphosate [N-(phosphonomethyl) glycine] are one of the most widely used pesticides in agriculture, urban areas and forestry. Although there has been documentation on the physical, chemical and toxicological properties of glyphosate, the aquatic toxicity of such formulations still requires assessment and evaluation. In the present study, we describe deliberate use of glyphosate-based herbicide in a bathing area of Lake Lednica (Wielkopolska, Poland) by unknown perpetrators in April, 2011. Glyphosate was detected using gas chromatography mass spectrometry (GC-MS) in the water samples collected from the bathing area at a mean concentration of 0.09 mg dm-3. Aboveground parts of emerged macrophytes (Phragmites australis and Typha latifolia) covering the investigated area were completely withered. Studies of benthic macroinvertebrates revealed no significant differences in taxa number between event (13 taxa) and control (14 taxa) sites although differences in abundance of particular taxa were observed. Significantly lower numbers of Chironomidae (by 41%), Oligochaeta (by 43%), Vivipariae (by 75%), Hirudinae (by 75%), Asellus aquaticus (by 77%), Gammarus pulex (by 38%) and Dreissena polymorpha (by 42%) were found at the glyphosate-treated site. Furthermore, compared to the control, chironomids (Chironomidae) exposed to glyphosate were represented by specimens smaller in length while A. aquaticus only showed large adults. The ranges of glyphosate concentration in the tissues of sampled macroinvertebrates and Phragmites australis organs were 7.3-10.2 μg kg-1 and 16.2-24.7 μg kg-1, respectively. Our study indicates that glyphosate-based herbicides may have adverse effects on aquatic organisms including macroinvertebrates, thus their use in (or nearby) surface waters should be subject to strict limitation.
.E., Zbierska J., Choiński A., 2009, Ocena stanu ekologicznego jezior w odniesieniu do Ramowej Dyrektywy Wodnej (Assessment of the ecological status of lakes according to Water Framework Directive), Zesz. Probl. Post. Nauk Roln. 540: 55-67 (in Polish). Ławniczak A.E., 2010a, The role of emergentmacrophytes in nutrient cycling in Lake Niepruszewskie (western Poland), Oceanol. Hydrobiol. Stud. 39(2): 75-83. Ławniczak A.E., 2010b, Overgrowing of two polymictic lakes in Central-Western Poland, Limnol. Rev. 10(3-4): 147-156. Ławniczak A.E., Zbierska J., Choiński A., Szczepaniak W
Ciliates on the Macrophytes in Industrially Heated Lakes (Kujawy Lakeland, Poland)
The ciliate assemblage on the macrophytes was examined in 2005 during the vegetation period in the Konińskie Lakes which are heating by post-cooling waters from thermal electric plants. As a result of changed temperature regimen the alien thermophilic macrophyte Vallisneria spiralis is becoming increasingly common in the littoral zone. A total of 150 ciliate taxa belonging to 27 orders were found. Greater ciliate species diversity was found on architecturally complex, submerged forms such as Ceratophyllum demersum and Myriophyllum spicatum. By contrast the ciliate compositions on emergent macrophytes with simple architecture in their submerged parts, such as Typha, Sparganium, or Acorus, were less species rich. Despite the simple architecture of Vallisneria leaves, the ciliate diversity on them was high. The results show that replacement of native macrophytes by the alien form V. spiralis in heated lakes did not impoverish the ciliate diversity.
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