Diatom communities in thermo-mineral springs of Galicia (NW Spain)

Abstract

The species composition of diatom assemblages was studied in five unpolluted thermo-mineral springs in Galicia (NW Spain). Three are considered hot and two cold, and some contain hydrogen sulphide. A total of 68 taxa (24 genera) have been recorded. The Shannon-Wiener diversity index (H′) ranged between 0.63 and 2.01. The nMDS ordination showed that diatom assemblage composition was influenced mostly by conductivity, temperature and hydrogen sulphide concentration. Diatom assemblages found in the Galician springs differed from those in springs of other geographical locations with similar physical and chemical characteristics. The most species-rich genera were Nitzschia and Achnanthidium with 10 and 8 species, respectively. Achnanthidium exiguum and Achnanthidium saprophilum had the widest distribution. Denticula thermalis and Achnanthidium caledonicum were found in environments with relatively low mineralization and low temperature, whereas Rhopalodia gibberula, Rhopalodia operculata and Fragilaria crotonensis were found in mineral-rich springs with high temperatures. Achnanthidium exiguum, A. saprophilum, Achnanthes coarctata, Achnanthes exigua var. elliptica, Mayamaea atomus, Eunotia implicata, Gomphonema minusculum, Gomphonema minutum and Cosmioneis pusilla were present in the spring with high H 2 S content.

Diatoms in Kamchatka’s Hot Spring Soils

“…The abundance of Nitzschia hantzschiana, Halamphora normanii, and Gomphonema sp. found in our study confirms existing data regarding the distribution these taxa in thermo-mineral springs [15,17,54].…”

“…In the samples we obtained from the Upper Paratunka and Dachnie springs, this diatom was found at pH 3.2-9.4 and temperature 30.0-69.5 • C. In a previous study of diatoms from hydrothermal springs on Kunashir Island, P. borealis was identified in Stolbchaty Cape springs and in Alekhin Bay springs at pH 4-5, 50-55 • C [54]. This taxon has also been found in the sulfidic Cuntis hot springs in Galicia (NW Spain), which are characterized by deep hydrothermal flows and temperatures of 48-54 • C [15].…”

“…Navicula species related to N. cincta are rare in springs, but many new species from this group have been described [58]. Navicula is a benthic-epiphytic, alkaliphilous species with cosmopolitan distribution [46], and is also common in thermo-mineral springs [15,17]. Navicula cincta prefers mostly eutrophic, electrolyte-rich waters and periodically wet habitats [58], and it is widely distributed in soils [40], so the discovery of this species in soils near hot springs was expected.…”

“…Only limited groups of organisms can survive in such harsh environments, and diatoms are one of these groups. Some researchers have investigated the biodiversity of diatom algae in hot springs [13][14][15][16][17]. Achnanthidium exiguum (Grunow) Czarnecki and Achnanthidium saprophilum (H.Kobayashi & Mayama) Round & Bukhtiyarova are the most distributed species in diatom communities in the thermo-mineral springs of Galicia, NW Spain [15].…”

“…Some researchers have investigated the biodiversity of diatom algae in hot springs [13][14][15][16][17]. Achnanthidium exiguum (Grunow) Czarnecki and Achnanthidium saprophilum (H.Kobayashi & Mayama) Round & Bukhtiyarova are the most distributed species in diatom communities in the thermo-mineral springs of Galicia, NW Spain [15]. Diatomella balfouriana Greville, Achnanthidium exiguum, and Anomoeoneis sphaerophora Pfitzer are the dominant species in hot springs in northern Thailand [17].…”