Habitat Characteristics ofEurytemora lacustris(Poppe, 1887) (Copepoda, Calanoida): The Role of Lake Depth, Temperature,Oxygen Concentration and Light Intensity

Abstract

Field observations, laboratory experiments and a literature survey were conducted to evaluate the habitat characteristics of Eurytemora lacustris (POPPE 1887), a freshwater calanoid copepod species. Combined effects of temperature and oxygen concentration in the deep water of thermally stratifying lakes seem to be the ultimate factors governing the occurrence of the species throughout its home-territory. E. lacustris is largely restricted to relatively deep lakes (>30 m) providing a hypolimnetic refuge characterised by low temperatures (<~10°C) and oxygenated water during summer. Therefore, although the species is spread over much of Europe it was only found in a small number of lakes. Long-term records in different lakes revealed E. lacustris to be perennial with relatively high biomasses occurring from May to September. During thermal stratification on average 87% of the nauplii and 72% of the copepodite biomass was found in hypolimnetic waters colder than 10°C. Diurnal vertical migration was observed for the copepodid stages, but the migration amplitude clearly decreased from May to September. The migration amplitude was significantly related to light intensity. According to its special habitat requirements, E. lacustris might be considered a glacial relict sensitive to temperature increase and oxygen depletion. IntroductionThe distribution of a given species within its home-territory largely depends on the species' ecological requirements and the extent to which these needs are satisfied by a certain biotope. As a result of the co-evolution between environment and biota, plants, animals and micro-organisms are restricted to particular geographical regions and habitats (ILLIES, 1971). Some species might be abundant in many places while others are rare and characterised by a scattered distribution (ILLIES, 1978). With respect to lakes, chemical and physical features of the habitat such as temperature, oxygen concentration and solar radiation are as important as biological factors like food supply and predation (THIENEMANN, 1928;LINDEMAN, 1942; STRAŠKRABA, 1980;ZARET, 1980). Eurytemora lacustris (POPPE, 1887), a calanoid freshwater copepod, can be found in lakes throughout an area reaching from the Boreal highlands of northern Norway south to the Black Sea and from the Central European lowlands to the eastern parts of the Caspian reInternat. Rev. Hydrobiol. 90

The aquatic glacial relict fauna of Norway – an update of distribution and conservation status

“…Besides the traditional relict species assemblage, we also report records of the two copepod species Eurytemora lacustris and Cyclops lacustris. Based on broad distributional correlations in freshwaters of other regions, E. lacustris ( Figure 1B) has indeed also previously been suggested as one of the relict taxa (Särkkä et al 1990, Kasprzak et al 2005, Maier et al 2011. Nevertheless, since it is occasionally found above the postglacial marine limit, it is not considered a true glacial relict species in Sweden (Kinsten 2012).…”

“…While the glacial relict concept is somewhat vague anyway, we also report on the new information on C. lacustris in this account, along with the similarly distributed E. lacustris (cf. Kasprzak et al 2005, Maier et al 2011. Further taxa that have been related to or mentioned together with the glacial relicts, but are not listed here, include the fish Osmerus eperlanus (smelt), present in all the large lakes in the Halden River watershed as well as in many other lakes with the relict crustaceans (cf.…”

Occurrence and Interannual Abundance Variation of Glacial Relict Calanoids Limnocalanus macrurus and Eurytemora lacustris in Lithuanian Lakes

“…Sars, 1863 is considered to be a 'classical' glacial relict species, which requires cold, highly-oxygenated waters. The same environmental conditions are also needed for another calanoid Eurytemora lacustris (Poope, 1887), which used to be attributed to glacial relicts, too (Grigelis et al 1981;Kasprzak et al 2005). These species were first recorded in Lithuanian lakes in the early 1950s (Kiselytė 1961), and their distribution was summarized in accordance with the records reported before 1980 (Grigelis & Arbačiauskas 1996, 1997.…”

“…The current observations also imply that habitatspecific interannual variation in L. macrurus population density may be generally greater than that of another calanoid E. lacustris. With respect to oxygen demand, L. macrurus (critical oxygen concentration is about 3 mg L -1 , Suschenya et al 1986) is probably more sensitive to the deterioration of oxygen conditions in comparison to E. lacustris (critical oxygen concentration is about 1 mg L -1 , Kasprzak et al 2005). In addition, these species vary in reproduction characteristics.…”

“…Extinction of E. lacustris was observed in Großer Plöner See, Germany (Plambeck 2001, cit. from Kasprzak et al 2005). The shrinkage of the distribution range of other glacial relict crustaceans, Monoporeia affinis (Lindstrom, 1855), Mysis relicta Loven, 1862 and Pallaseopsis quadrispinosa (G. O. Sars, 1867) in particular, has been documented in lakes of Poland and Germany (Žmudzinski 1990, 1995Köhn & Waterstraat 1990).…”