Cladocera from the Sediment of High Arctic Lake in Svalbard (Norway)

The High Arctic Region’s freshwater ecosystems serve as hot spots to study the impact of extreme warming conditions on the biota. The cladoceran remains have been recovered from the surface sediments of a non-marine water body near Ny-Alesund, Svalbard, Norway. The cladoceran (crustaceans) belongs to the Chydorus sphaericus group Frey, 1980 and Daphnia pulex Leydig, 1860. The ecology of the species suggests that they lived in a well-developed ecosystem with Water Quality Class 3. This study has implications for understanding the response of the present-day biota experiencing the changing climate conditions and using these remains for assessing palaeoenvironmental conditions.

Linking changes in sedimentary Cladocera assemblages to limnological variables in 67 Sudbury (Ontario, Canada) lakes reflecting various degrees of metal smelter impacts

Despite extensive records of chemical recovery, relatively little is known about recovery of aquatic biota in Sudbury (Ontario, Canada). Cladocera (Branchiopoda) are key components of lake food webs and understanding spatial patterns in their assemblages may emphasize ecosystem recovery challenges. Paleolimnological techniques complement and provide long-term context to modern monitoring. Cladoceran remains from the surface sediments of 67 lakes across a gradient of smelter impacts were examined to determine which measured limnological factors mostly influenced assemblage composition. Lakes were divided into four categories by acidification histories and location: Acidified (pH <6) Urban, Acidified Non-urban, Acidified Killarney, and Reference (pH >6) lakes. Specific conductance, nutrients, alkalinity, and lake depth significantly structured assemblages. Most assemblages were dominated by generalist taxa. Relative abundances of Alona taxa varied strongly along alkalinity and pH gradients. Lakes with high metal concentrations were generally less diverse and dominated by generalist taxa, although metals often co-occurred with other stressors. Recovery targets could be affected by these chemical factors. These data provide useful information for future environmental inferences from cladocerans in metal smelting regions.

Reconstruction of flood events in an oxbow lake (Marótzugi-Holt-Tisza, NE Hungary) by using subfossil cladocerans remains and sediments

<p>Oxbow lakes are important components of the floodplain systems of lowland rivers. During flood events, oxbows are connected with the main river channel, and behave as lotic systems, while during inter-flood periods, these lakes can be considered as lentic ecosystems. Rivers are generally poor in planktonic organisms and their sediments contain scarce biological remains in comparison to lentic water ecosystems. However, due to their alternating running and standing water regime, sedimentary biological remains of oxbow lakes can be used as proxies for tracking changes of past hydrological regimes. In this study we investigated how cladoceran communities respond to flood events, and whether flood events can be recognized by community analysis of cladoceran remains. A sediment core from Marótzugi-Holt-Tisza oxbow lake was analyzed for identification of past flood events based on changes in the subfossil Cladocera community. Floods were defined based on the proportion of fine sand (50 µm grain size) in the oxbow sediments. If the fine sand portion was &lt;3%, the water regime of the oxbow was considered as lentic, otherwise it was lotic. Both organic and pigment contents were significantly higher in the core sections deposited during lentic stages. Thirty-four Cladocera species were determined in this core, all common to littoral habitats of eutrophic shallow lakes in Hungary. One planktonic (<em>Bosmina longirostris</em>) and four chydorid species (<em>Alona rectangula</em>, <em>Acroperus harpae</em>, <em>Alonella nana</em> and <em>Chydorus sphaericus</em>) were dominant throughout the core and contributed &gt;90% of total remains. Discriminant analysis on cladoceran data confirmed that lotic and lentic hydrological stages were characterized by different Cladocera species associations. <em>Bosmina longirostris, Chydorus sphaericus, Alona rectangula, Acroperus harpae, Leydigia leydigi, A. quadrangularis </em>and<em> A. nana</em> were mainly responsible for the differences between lotic and lentic species assemblages. Our results revealed that Cladocera remains can be used to track changes in the hydrological regime of oxbow lakes. </p><p> </p>

Cladocera biodiversity in La Tembladera Lake (Ecuador): a palaeolimnological approach

Cladocera (Crustacea: Branchiopoda) biodiversity was examined in sediment assemblages in La Tembladera Lake, on the southern coast of Ecuador. We found remains from 14 Cladocera taxa belonging to three families: Sididae, Daphnidae and Chydoridae. One taxon is planktonic (Ceriodaphniaspp.) and 13 taxa are littoral (Sarsilatonaserricauda,Chydorussp.,Dunheveniasp.,Leberissp.,Alonasp.,Magnospina dentifera,Kurziasp.,Acroperus tupinamba,Camptocercussp.,Oxyurella longicaudis,Leydigiopsissp.,Euryalonasp. andNotoalonacf.sculpta). Descriptions and pictures of the remains were included in this article to help palaeolimnologists identify tropical cladoceran remains in the sediment. These results enlarge the crustacean biodiversity data for dry tropical forests in South America and help to constrain our understanding of their geographical distribution. Further studies should focus on capturing living cladocerans to make identifications at the species level and to help interpret the sedimentary signal using ecological data.