No more lake balls (Aegagropila linnaei Kützing, Cladophorophyceae, Chlorophyta) in The Netherlands?

Abstract

Aegagropila linnaei, a freshwater green macroalga, had been abundant in several locations in The Netherlands before the 1960s. Both the 'lake ball' form of this alga and dense unattached mats floating over the sediment have been described from these locations. After 1967, this species has not been recorded anymore from The Netherlands. In 2007, several historical collection sites were surveyed for extant populations of A. linnaei. All habitats have changed drastically during the last 50 years and were affected severely by eutrophication. Populations of A. linnaei seem to have become extinct in all but one location (Boven Wijde, province Overijssel), where we found very small amounts of attached filaments. The attached form had not been reported previously from The Netherlands. Environmental conditions do not seem suitable anymore to maintain extensive unattached growth forms including the enigmatic lake balls, and the species must be regarded as threatened in The Netherlands and we propose to include A. linnaei in a national red list. The decline of populations elsewhere is reviewed and discussed in this paper. In addition to morphological identification of the attached filaments, partial sequences of the nuclear large subunit rDNA were generated and compared with different growth forms and habitats from several other locations outside The Netherlands. The sequences confirm the identity of the Dutch material and indicate very little divergence both between populations in different locations and between different growth forms.

Biogeography of Aegagropila linnaei (Cladophorophyceae, Chlorophyta): a widespread freshwater alga with low effective dispersal potential shows a glacial imprint in its distribution

“…Detailed knowledge of the distribution of a species is important both for evolutionary studies and with respect to conservation. Several studies have reported declining or extinct populations of A. linnaei in connection with eutrophication (Pankow, 1985;Wakana et al, 2001Wakana et al, , 2005Wakana et al, , 2006Einarsson et al, 2004;Boedeker & Immers, 2009;Boedeker et al, 2010). In this study, a comprehensive overview of the distribution of A. linnaei is given, based on herbarium specimens, available literature data and recent field observations.…”

“…, 2001, 2005, 2006; Einarsson et al. , 2004; Boedeker & Immers, 2009; Boedeker et al , 2010). In this study, a comprehensive overview of the distribution of A. linnaei is given, based on herbarium specimens, available literature data and recent field observations.…”

Ecological and Morphological Profile of Floating Spherical Cladophora socialis Aggregations in Central Thailand

“…An extremely rare freshwater alga, Aegagropila linnaei , is known for its beautiful spherical filamentous aggregations [ 4 ]. It has become popular in the souvenir and aquarium trades, and is depicted on postage stamps from Japan and Iceland [ 1 , 5 ]. This alga is an endangered or protected species in Japan, Iceland, United Kingdom, Germany, Sweden, and Russia, because of declining populations, and is included in national red lists and other conservation strategies [ 5 , 6 ].…”

“…It has become popular in the souvenir and aquarium trades, and is depicted on postage stamps from Japan and Iceland [ 1 , 5 ]. This alga is an endangered or protected species in Japan, Iceland, United Kingdom, Germany, Sweden, and Russia, because of declining populations, and is included in national red lists and other conservation strategies [ 5 , 6 ]. Scientifically, however, the mechanism for forming spherical aggregations has been researched and discussed.…”

“…Scientifically, however, the mechanism for forming spherical aggregations has been researched and discussed. It is generally assumed that the ball shape is a result of both mechanical factors, such as wave-induced rolling motion, and morphological features leading to entanglement of the filament [ 1 , 5 ].…”