Extremely Acidic Eukaryotic (Micro) Organisms: Life in Acid Mine Drainage Polluted Environments—Mini-Review

Acid Mine Drainage (AMD) results from sulfide oxidation, which incorporates hydrogen ions, sulfate, and metals/metalloids into the aquatic environment, allowing fixation, bioaccumulation and biomagnification of pollutants in the aquatic food chain. Acidic leachates from waste rock dams from pyritic and (to a lesser extent) coal mining are the main foci of Acid Mine Drainage (AMD) production. When AMD is incorporated into rivers, notable changes in water hydro-geochemistry and biota are observed. There is a high interest in the biodiversity of this type of extreme environments for several reasons. Studies indicate that extreme acid environments may reflect early Earth conditions, and are thus, suitable for astrobiological experiments as acidophilic microorganisms survive on the sulfates and iron oxides in AMD-contaminated waters/sediments, an analogous environment to Mars; other reasons are related to the biotechnological potential of extremophiles. In addition, AMD is responsible for decreasing the diversity and abundance of different taxa, as well as for selecting the most well-adapted species to these toxic conditions. Acidophilic and acidotolerant eukaryotic microorganisms are mostly composed by algae (diatoms and unicellular and filamentous algae), protozoa, fungi and fungi-like protists, and unsegmented pseudocoelomata animals such as Rotifera and micro-macroinvertebrates. In this work, a literature review summarizing the most recent studies on eukaryotic organisms and micro-organisms in Acid Mine Drainage-affected environments is elaborated.

Responses of Freshwater Zooplankton as Biological Indicators to the Aquatic Chemical Properties

Zooplankton are found very sensitive to even slight aquatic pollution due to a number of chemical imbalances in freshwater bodies. As an amazing tiny creature zooplankton play a very crucial role in the aquatic food chain by transferring energy from primary levels to tertiary organisms. For many years it has been well established that zooplankton act as promising biological indicators to continuously fluctuating aquatic environments and subsequently to global warming. While reacting to these aquatic environmental fluctu-ations, zooplankton population growth can either be stimulated or inhibited. The presence or absence of particular zooplankton species can reveal the trophic status of the water body. Moreover, in a harsh env-ironment, algal toxins may have drastic effects on the behavioral characteristics of zooplankton.

Toxicity and bioaccumulation of 2,2', 4,4'-tetrabromodiphenyl ether (BDE47) in a laboratory aquatic food chain

Rising levels of polybrominated diphenyl ethers (PBDEs) have been ovserved in the environment, humans, and animlas. Studies have shown that these compounds can elicit toxic effects in animals (e.g. neurotoxicity and thyroid toxicity). This research investigated the effects of BDE47 on the survival and reproduction of Daphnia magna over two generations. The impacts of water-borne exposure were compared to dietary exposure using the following treatments: dosed water (DW), dosed algae (DA) and dosed water and algae (DWA). In the first generation, significant impacts on reproduction were observed in daphnids in the DA and DWA treatments. In the second generation, no significant impacts on reproduction were observed indicating a recovery from maternal exposure. When second generation daphnids were exposed to BDE47, there was high mortality in the DWA treatment anad reduced reproduction in all dosed treatments. Dietary exposure to BDE47 had a more profound impact on daphnid reproduction than water exposure. In the second generation, dietary exposure affected both survival and reproduction and water exposure reduced reproduction, indicating that maternal exposure was a factor.

Toxicity and bioaccumulation of 2,2', 4,4'-tetrabromodiphenyl ether (BDE47) in a laboratory aquatic food chain

Rising levels of polybrominated diphenyl ethers (PBDEs) have been ovserved in the environment, humans, and animlas. Studies have shown that these compounds can elicit toxic effects in animals (e.g. neurotoxicity and thyroid toxicity). This research investigated the effects of BDE47 on the survival and reproduction of Daphnia magna over two generations. The impacts of water-borne exposure were compared to dietary exposure using the following treatments: dosed water (DW), dosed algae (DA) and dosed water and algae (DWA). In the first generation, significant impacts on reproduction were observed in daphnids in the DA and DWA treatments. In the second generation, no significant impacts on reproduction were observed indicating a recovery from maternal exposure. When second generation daphnids were exposed to BDE47, there was high mortality in the DWA treatment anad reduced reproduction in all dosed treatments. Dietary exposure to BDE47 had a more profound impact on daphnid reproduction than water exposure. In the second generation, dietary exposure affected both survival and reproduction and water exposure reduced reproduction, indicating that maternal exposure was a factor.

Tracking Recent DDT Contamination in a Northern New England Watershed: A Geosciences Approach

The p,p’ isomers of DDT, DDE, and DDD were analyzed in soils, sediments, and crayfish in the Squam Lake watershed in central New Hampshire (NH), U.S.A. Bennett Brook sources elevated levels of DDT residues to Squam Lake through sediment transport, likely due to legacy contamination from applications to an apple orchard surrounding the stream in the mid 1900s. Results reveal a point source located at a barn used during the orchard operation, which was burned down around 1967, with up to 723 µg/kg p,p’ DDT and 721 µg/kg p,p’ DDE in the soils. Higher DDT than DDE in soil samples, but not in sediment samples, suggests persistence of the contaminant in watershed soils, and faster degradation once mobilized into Bennett Brook and Squam Lake. DDT residues in the lake sediments from 1951 to the present, reveal DDT has consistently been entering Squam Lake since usage began in the U.S. There are likely multiple sources that have contributed to the constant supply, including the orchard soils treated with DDT serving as a nonpoint source, the barn site, and DDT-laden soils vulnerable to erosion, including stream banks and logged or steeply sloped land. Detections of residues in the stream and lake sediments exceed certain sediment quality guidelines for the protection of aquatic life. Higher p,p’ DDE levels in crayfish collected in the mouth of Bennett Brook versus crayfish collected in Squam Lake, distant from Bennett Brook, suggests that residues sourcing from this sub-watershed are entering the aquatic food chain at levels higher than other parts of the lake.

Particle number-based trophic transfer of gold nanomaterials in an aquatic food chain

Analytical limitations considerably hinder our understanding of the impacts of the physicochemical properties of nanomaterials (NMs) on their biological fate in organisms. Here, using a fit-for-purpose analytical workflow, including dosing and emerging analytical techniques, NMs present in organisms are characterized and quantified across an aquatic food chain. The size and shape of gold (Au)-NMs are shown to control the number of Au-NMs attached to algae that were exposed to an equal initial concentration of 2.9 × 1011 particles mL−1. The Au-NMs undergo size/shape-dependent dissolution and agglomeration in the gut of the daphnids, which determines the size distribution of the NMs accumulated in fish. The biodistribution of NMs in fish tissues (intestine, liver, gills, and brain) also depends on NM size and shape, although the highest particle numbers per unit of mass are almost always present in the fish brain. The findings emphasize the importance of physicochemical properties of metallic NMs in their biotransformations and tropic transfers.