Salinity Tolerance of Diatoms From Thalassic Hypersaline Environments

Abstract

Thirty‐four benthic diatom strains were isolated from thalassic hypersaline marine environments and their salinity tolerance characterized in growth experiments conducted at salinities ranging from 0.5% to 17.5% (weight of total salts per volume, g·100 mL−1). The results were compared with the patterns of diatom species distribution and abundance in hypersaline evaporation ponds and tidal channels of Guerrero Negro, Baja California Sur, Mexico. The isolated strains were representative of the diatom assemblages present in the saltern ponds but were less so of natural assemblages in tidal channels. In general, we found a clear decreasing trend of diatom diversity in the field and in the isolated strains with increasing salinity. With some exceptions, the upper limit of salinity tolerance in cultivated strains corresponded to their distribution in field samples. However, the relative abundance of species in the field was not correlated with growth rates achieved in culture for the same salinities. Most cultured strains exhibited extreme euryhalinity growing well from brackish to hypersaline conditions, but the particulars of salt tolerance were quite diverse among strains. The most halotolerant taxa, two Amphora species, Amphora cf. subacutiuscula Schoeman, Nitzschia fusiformis Grunow, and Entomoneis sp., grew well in salinities ranging from 0.5% to 15%. Three strains of Pleurosigma strigosum W. Smith that were unable to grow in salinities less than 5% total salts represent the only true halophilic diatoms ever reported. The fact that many strains displayed a remarkable halotolerance, with optimal or near‐optimal growth rates at salinities as high as three times that of seawater, implies that diatoms from hypersaline environments are evolutionarily highly adapted to such environments.

Morphometric study of Navicula morphospecies (Bacillariophyta) with respect to diatom life cycle.

“…The modern morphometric techniques appeared to be sensitive tool for distinguishing subtle morphological differences between morphotypes of diatom strains traditionally assigned to a single species (rhode et al 2001, PaPPas & stoerMer Table 1. (Weisse et al 2007) and salinity (claVero et al 2000, fiNlay et al 2006, a few such studies were done in diatoms (schultZ 1971(schultZ , schMid 1976(schultZ , cox 1994 …”

Diversity and Distribution in Hypersaline Microbial Mats of Bacteria Related to Chloroflexus spp

“…Similarly, salinity was previously found to govern the distribution of cyanobacteria and diatoms in the same saltern system (4,24). However, it must be cautioned that rRNA genes are more conserved in structure and function than most protein encoding genes, and, consequently, identical 16S rRNA gene sequences may conceal several physiologically and ecologically different microbial populations (e.g., see reference 28).…”

The place of diatoms in the biofuels industry

“…This does not preclude freshwater diatoms from being developed for biofuels production, but considering the issue of water supply, saline-tolerant species may be the most appropriate for development. Diatoms isolated from thalassic hypersaline marine environments include both centric and pennate species that grow well at salinities ranging from 0.5 to 15%, and three strains of Pleurosigma strigosum cannot grow in salinities less than 5% total salts, representing truly halophilic diatoms [79]. Different strains of P. tricornutum were shown to have near-linear growth rates (divisions per day) in salinities ranging from 5 to 70 psu [80].…”