Data from: The jellification of north temperate lakes

Calcium (Ca) concentrations are decreasing in softwater lakes across
eastern North America and western Europe. Using long-term contemporary and
palaeo-environmental field data, we show that this is precipitating a
dramatic change in Canadian lakes: the replacement of previously dominant
pelagic herbivores (Ca-rich Daphnia species) by Holopedium glacialis, a
jelly-clad, Ca-poor competitor. In some lakes, this transformation is
being facilitated by increases in macro-invertebrate predation, both from
native (Chaoborus spp.) and introduced (Bythotrephes longimanus)
zooplanktivores, to which Holopedium, with its jelly coat, is relatively
invulnerable. Greater representation by Holopedium within cladoceran
zooplankton communities will reduce nutrient transfer through food webs,
given their lower phosphorus content relative to daphniids, and greater
absolute abundances may pose long-term problems to water users. The
dominance of jelly-clad zooplankton will likely persist while lakewater Ca
levels remain low.