Habitat shifts of Mysis relicta (Decapoda, Mysidacea) in the lakes Breiter and Schmaler Luzin (NE Germany)

Abstract

Between spring 2001 and autumn 2004, the habitat use, vertical migration, and density of Mysis relicta in the lakes "Breiter Luzin" and "Schmaler Luzin" in northeastern Germany were investigated by horizontal net hauls, epibenthic sledge hauls, and SCUBA diving. On 3-4 July 2001 we estimated a density of 466.03 ind./m 2 in the water column of lake "Breiter Luzin", but in April of 2002 population density was only 5.26 ind./m 2 . In October 2004 the observed densities increased with depth, starting at the lower sublittoral down to the upper profundal on about 1000 ind./m 2 . Downward from 22 m, densities fluctuated around this value up to 30 m depth. During daytime, mysids were never observed above 9 m. Below this limit all suitable parts of both lakes were occupied. We found no evidence for a preference of different sediment types as mud or sand. During daytime mysids showed a strong affinity for the lake bottom, and adults tend to live in deeper areas than juveniles. At night this distribution seems to be inverted. In July 2001 the proportion of adults (especially females) was highest in the metalimnion and the upper hypolimnion, whereas the proportion of juveniles increased with depth.

Does the Ice Age legacy end in Central Europe? The shrinking distributions of glacial relict crustaceans in Lithuania

“…The amphipod M. affinis was originally found in only two locations in Lithuania and is now considered extinct in German and Polish waters (Köhn & Waterstraat, 1990; Żmudziński, 1995). The trends of declining glacial relict population status in Lithuania are consistent with observations from other countries, and are especially pronounced at the southern distribution limits, where lake eutrophication and increasing temperatures are the primary drivers (Ireland and BritainPenk, 2011; Griffiths et al, 2015; Germany –Scharf & Koschel, 2004; Rumpf et al, 2005). In some cases, and specifically in Northern Germany, strong water management and lake restoration efforts improved deep‐water oxygen conditions and populations of glacial relicts have recovered (Scharf & Koschel, 2004; Rumpf et al, 2005).…”

“…The trends of declining glacial relict population status in Lithuania are consistent with observations from other countries, and are especially pronounced at the southern distribution limits, where lake eutrophication and increasing temperatures are the primary drivers (Ireland and BritainPenk, 2011; Griffiths et al, 2015; Germany –Scharf & Koschel, 2004; Rumpf et al, 2005). In some cases, and specifically in Northern Germany, strong water management and lake restoration efforts improved deep‐water oxygen conditions and populations of glacial relicts have recovered (Scharf & Koschel, 2004; Rumpf et al, 2005). Yet, the increasing surface and deep‐water temperatures and rapid changes in water mixing and water budgets driven by global heating (Shatwell, Thiery & Kirillin, 2019; Woolway et al, 2020) are likely to be putting further pressure on glacial relict populations.…”