Limnological Characteristics and Rotifer Community Composition of Northern Mexico Chihuahuan Desert Springs.

Desert springs are critical for wildlife and human subsistence, but poorly studied. The springs in the northern Chihuahuan Desert region of Mexico are no exception. While groundwater overexploitation and other anthropogenic activities have endangered these waters, little is known about their water quality or biodiversity. We monitored five springs on a monthly basis for one year, and two others sporadically, to determine their physicochemical characteristics and to study rotifer community composition as an assessment of biodiversity. Seasonal variation in temperature, dissolved oxygen (DO), and conductivity was observed in the five springs. DO was occasionally below the criterion for aquatic life (<4mg/L) in some springs. Ca2+ (468-775.2 mg/L) was the dominant ion in all springs except Ojo de Santa María where Na+ (180-290 mg/L) dominated. Of 57 rotifer species identified, Lepadella patella (Müller, 1786), Lepadella triptera (Ehrenberg, 1830), and Philodina megalotrocha, Ehrenberg, 1832 were present in most springs. The rotifer community exhibited nestedness among the sites (supported by four null modes, p<0.05) and was correlated with fall season, DO, and nitrate concentration. This work provides information that will aid in management practices and provide important baseline data on water quality and regional diversity of a major component of the zooplankton.

Trace-metal contamination in the glacierized Rio Santa watershed, Peru.

The objective of this research is to characterize the variability of trace metals in the Rio Santa watershed based on synoptic sampling applied at a large scale. To that end, we propose a combination of methods based on the collection of water, suspended sediments, and riverbed sediments at different points of the watershed within a very limited period. Forty points within the Rio Santa watershed were sampled between June 21 and July 8, 2013. Forty water samples, 36 suspended sediments, and 34 riverbed sediments were analyzed for seven trace metals. The results, which were normalized using the USEPA guideline for water and sediments, show that the Rio Santa water exhibits Mn concentrations higher than the guideline at more than 50% of the sampling points. As is the second highest contaminating element in the water, with approximately 10% of the samples containing concentrations above the guideline. Sediments collected in the Rio Santa riverbed were heavily contaminated by at least four of the tested elements at nearly 85% of the sample points, with As presenting the highest normalized concentration, at more than ten times the guideline. As, Cd, Fe, Pb, and Zn present similar concentration trends in the sediment all along the Rio Santa.The findings indicate that care should be taken in using the Rio Santa water and sediments for purposes that could affect the health of humans or the ecosystem. The situation is worse in some tributaries in the southern part of the watershed that host both active and abandoned mines and ore-processing plants.

Lethal and sublethal effects of selected PPCPs on the freshwater rotifer, Plationus patulus.

Pharmaceuticals and personal care products (PPCPs) have been reported in surface waters around the world. The continuous input of these pollutants into freshwaters and their potential effects on aquatic life are of increasing concern. The rotifer Plationus patulus, a basal member of riverine food webs, was used to test acute and chronic toxicity of 4 PPCPs (acetamidophenol, caffeine, fluoxetine, triclosan). A population from a remote site in Mexico (reference population) and one from an urbanized stretch of the Rio Grande were exposed. Acute toxicity tests show that both populations were more sensitive to fluoxetine. Chronic exposure to acetamidophenol (10 mg/L, 15 mg/L, and 20 mg/L) inhibited reference population growth, whereas Rio Grande population growth was inhibited only at 15 mg/L and 20 mg/L. Population growth was inhibited at 200 mg/L and 300 mg/L of caffeine for both populations. Chronic exposure to fluoxetine (0.020 mg/L) significantly inhibited population growth for the Rio Grande population only. Triclosan (0.05 mg/L, 0.075 mg/L, 0.10 mg/L) had the most deleterious effects, significantly reducing both populations' growth rates. Sublethal effects of chronic exposure to PPCPs included decreased egg production and increased egg detachment. A mixed exposure (6 PPCPs, environmentally relevant concentrations) did not affect population growth in either population. However, the continuous introduction of a broad suite of PPCPs to aquatic ecosystems still may present a risk to aquatic communities. Environ Toxicol Chem 2015;34:913-922. © 2014 SETAC.

Rotifers from selected inland saline waters in the Chihuahuan Desert of México.

BACKGROUND: In spite of considerable efforts over past decades we still know relatively little regarding the biogeography of rotifers of inland waters in México. To help rectify this we undertook an extensive survey of the rotifer fauna of 48 water bodies in the Chihuahuan Desert of México. RESULTS: Of the sites surveyed, 21 had salinities >or= 2000 microS cm-1 and in these we found 57 species of monogonont rotifers and several bdelloids. Species richness in the saline sites varied widely, with a range in species richness of 1 to 27 and a mean (+/- 1SD) = 8.8 (+/- 6.2). Collectively all sites possess relatively high percent single- and doubletons, 33.3 and 21.7%, respectively. Simpson's Asymmetric Index indicated that similarity in rotifer species composition varied widely among a set of 10 sites. These were selected because they were sampled more frequently or represent unusual habitats. These SAI values ranged from 0.00 (complete dissimilarity) to 1.00 (complete similarity). The Jaccard Index varied between 0.00 and 0.35. This observation probably reflects similarities and differences in water chemistry among these sites. Inland saline systems differed in their chemical composition by region. Conductivity was related to hardness and alkalinity. In addition, hardness was positively associated with chloride and sulfate. RDA showed that several species were positively associated with chloride concentration. Other factors that were significantly associated with rotifer species included the presence of macrophytes, nitrate content, oxygen concentration, TDS, latitude and whether the habitat was a large lake or reservoir. CONCLUSION: This study illustrates the diversity of the rotiferan fauna of inland saline systems and the uniqueness among waterbodies. Conservation of these systems is needed to preserve these unique sources of biodiversity that include rotifers and the other endemic species found in association with them.