New Records of Freshwater Algae from the Jordanian Aquatic System

Microcystin-LR (MC-LR) and cylindrospermopsin (CYN) are the most representative cyanobacterial cyanotoxins. They have been simultaneously detected in aquatic systems, but their combined ecotoxicological effects to aquatic organisms, especially microalgae, is unknown. In this study, we examined the effects of these cyanotoxins individually and as a binary mixture on the growth rate of the freshwater algae Chlorella vulgaris. Using the MIXTOX tool, the reference model concentration addition (CA) was selected to evaluate the combined effects of MC-LR and CYN on the growth of the freshwater green algae due to its conservative prediction of mixture effect for putative similar or dissimilar acting chemicals. Deviations from the CA model such as synergism/antagonism, dose-ratio and dose-level dependency were also assessed. In single exposures, our results demonstrated that MC-LR and CYN had different impacts on the growth rates of C. vulgaris at the highest tested concentrations, being CYN the most toxic. In the mixture exposure trial, MC-LR and CYN showed a synergistic deviation from the conceptual model CA as the best descriptive model. MC-LR individually was not toxic even at high concentrations (37mgL(-1)); however, the presence of MC-LR at much lower concentrations (0.4-16.7mgL(-1)) increased the CYN toxicity. From these results, the combined exposure of MC-LR and CYN should be considered for risk assessment of mixtures as the toxicity may be underestimated when looking only at the single cyanotoxins and not their combination. This study also represents an important step to understand the interactions among MC-LR and CYN detected previously in aquatic systems.

Predicting the joint algal toxicity of multi-component s-triazine mixtures at low-effect concentrations of individual toxicants

The common metal-organic framework (MOF) MIL-101(Cr)-NH2 has attracted considerable attention due to its great potential applications in the environmental field. Nevertheless, its behavior and fate in aquatic systems are unknown. This study quantified and visualized the interactions of MIL-101(Cr)-NH2 with the freshwater phytoplanktonic alga Chlamydomonas reinhardtii and its potential trophic transfer to zooplankton. The unicellular alga absorbed and accumulated the MOF by surface attachment, forming agglomerates and eventually cosettling out from water. Bioimaging revealed that MIL-101(Cr)-NH2 was internalized by the algal cells and mainly occurred in the pyrenoid. Without algae in a freshwater system, MIL-101(Cr)-NH2 was ingested by Daphnia magna, showing steadily increasing concentrations approaching 1-9% of dry body weight. Addition of algae substantially suppressed D. magna uptake of MIL-101(Cr)-NH2 by 63.8-97.9%. Such inhibition could be explained by the competitive uptake of MOF by the algae and the inductive effects of algal food on MOF elimination by D. magna. The MOF (≤1 mg/L) ingested by D. magna was centered in the gut regions, whereas large MOF or algae-MOF aggregates were adsorbed onto the carapace and appendages, including the antennae, at 10 mg/L. Overall, the algae were the major targets for MIL-101(Cr)-NH2, with nearly all algal cells settling out at 10 mg/L within 24 h. The possibility of trophic transfer of MIL-101(Cr)-NH2 to D. magna in aquatic systems with algae present was limited due to its low accumulation potential and short retention time in D. magna.

The biogeochemical behaviour of selenium in two lentic environments in the Elk River Valley, British Columbia

Studies were undertaken to obtain a more accurate concept of the transport of radionuclides in aquatic systems. Various stages of this research were completed and published previously in progress reports, and are listed in the references. These reports describe the dispersion, uptake, release, and transport of /sup 89/Sr, /sup 137/Cs, /sup 103/Ru, /sup 58/Co and /sup 51/Cr. Transport data were obtained by conducting laboratory, model river, and field tests. Canal, river, and estuarine environmerts provided the necessary field information on hydrodynamic dispersion and on uptake and release of radionuclides by sediments. Model river data provided most of the useful uptake and release information involving special sediments, plants, and aquatic environments. Topics discussed include the factors affecting radionuclide transport, the use of model rivers to study cortinuous release of radionuclides, and the influence of various environmental factors on the accumulation and desorption of mercurials by a fresh water alga. Radioactive isotopes of mercury in the form of mercuric mercury and methyl mercury were used as tracers. (CH)

Time-averaged concentrations are effective for predicting chronic toxicity of varying copper pulse exposures for two freshwater green algae species

Effects of tire wear particle on growth, extracellular polymeric substance production and oxidation stress of algae Chlorella vulgaris: Performance and mechanism

Barium is present at elevated concentrations in oil and gas produced waters, and there is no international water quality guideline value to assess the potential risk of adverse effects to aquatic biota. Sulfate concentration largely controls the solubility of barium in aquatic systems, with insoluble barium sulfate (barite) assumed to be less bioavailable and less toxic than dissolved barium. We exposed aquatic biota to dissolved barium only and to a mixture of dissolved and precipitated barium. The chronic dissolved barium 48-h growth rate inhibition effect concentrations, (EC10 and EC50) for the tropical freshwater alga Chlorella sp. 12 were 40 mg/L (27-54 mg/L 95% confidence limits [CL]), and 240 mg/L (200-280 mg/L 95% CL), respectively. The acute EC10 and EC50 values for 48-h immobilization of the water flea (Ceriodaphnia dubia) by dissolved barium were 14 mg/L (13-15 mg/L 95% CL) and 17 mg/L (16-18 mg/L 95% CL), respectively. Chlorella sp. 12 was significantly more sensitive to precipitated barium than to dissolved barium, whereas the opposite seemed likely for C. dubia. Ceriodaphnia dubia was predicted to be chronically sensitive to dissolved barium at concentrations measured in produced waters and receiving waters, based on a predicted chronic EC10 of 1.7 mg/L derived from the acute EC50/10. Further chronic toxicity data that account for barium toxicity in dissolved and precipitated forms are required to derive a barium guideline for freshwater biota. Environ Toxicol Chem 2018;37:1632-1642. © 2018 SETAC.

This chapter begins with a general description of the structure and functions of the main parts of the insect alimentary system, and how they differ among taxa according to their diet. The alimentary system of most aquatic grazers and shredders is more similar to the relatively simple gut found in generalist terrestrial insects (e.g., cockroaches), than to the gut of terrestrial insects that consume solid plant tissues (e.g., lepidopteran larvae). This is related to the structural and nutritional differences between freshwater algae and terrestrial plants, and to the added nutrition from the microfauna and flora that is often with detritus in aquatic systems. Larvae and adults of the same species often have different diets and their guts differ morphologically and functionally. These differences are often extreme where adults are short-lived and do not feed, e.g. mayflies. Whether the guts served any function in non-feeding adults is unclear. Not all the food consumed by an insect is digested or absorbed and the undigested material is excreted, along with wastes of various metabolic processes. The final section considers the digestive processes and how these differ with the nutritional quality of food, the roles of microorganism in digestion, and the impacts of secondary plant compounds.

Removal of trimethoprim, sulfamethoxazole, and triclosan by the green alga Nannochloris sp.

Enrofloxacin (ENR), a fluoroquinolones antibiotic, is widely used in the medical and aquaculture fields. Its residues in surface waters in China are high. However, few studies have evaluated both its toxicity to phytoplankton and the degradation or removal by microalgae. In this study, the growth, photosynthetic activity, and exopolysaccharides (EPS) of freshwater micro-green algae Dictyosphaerium sp. and the dynamics of ENR concentrations (0, 5, 25, 50, and 100 mg·L-1) were studied through an exposure experiment for 12 days. Results showed that the biomass and photosynthetic pigment content of Dictyosphaerium sp. increased with increasing exposure time in each treatment; however, it showed a significant inhibitory effect on the growth and pigment accumulation of Dictyosphaerium sp. compared with the control group (P<0.01). The LC50 of ENR to Dictyosphaerium sp. was (241.29±7.33) mg·L-1 after 96-h exposure, indicating that Dictyosphaerium sp. could adapt to the stress conditions of high concentration ENR. Meanwhile, when the concentration of enrofloxacin was<5 mg·L-1, it was found to promote the maximum photosynthetic rate (Fv/Fm) of Dictyosphaerium sp. On the contrary, when the concentration of enrofloxacin was>5 mg·L-1, photosynthetic inhibition was observed (P<0.01). The actual photosynthetic rate (Yield) and the maximum electron transfer rate (ETRmax) showed a trend of initially decreasing and then increasing in 12 days. It can gradually adapt to the stress conditions and recover certain photosynthetic activity after 6 days' exposure. In addition, ENR can also stimulate the EPS (RPS and CPS) release. At the end of the experiment, the removal rates of ENR in the four control groups (no algae addition groups) (5, 25, 50, and 100 mg·L-1ENR) were 7.27%, 5.56%, 5.30%, and 4.88%, respectively, while the removal rates of the treatment groups were 3.21, 3.01, 2.69, and 2.83 times of the no algae groups, indicating that Dictyosphaerium sp. had a significant promoting effect on the removal of ENR (P<0.01). Overall, our results can provide new insights for the understanding of the ecological toxicity of fluoroquinolone antibiotics to primary producers in the aquatic system and also provide new ideas for the ecological removal of antibiotic residues in water bodies and the biological resource utilization of freshwater microalgae.

Iron colloids reduce the bioavailability of phosphorus to the green alga Raphidocelis subcapitata

Very little is known about the diversity and distribution of freshwater unicellular coccoid green algae. The simple morphology and small size of these organisms make reliable identification extremely difficult. Current hypotheses suggest that species of coccoid algae are widely distributed, opportunistic organisms that are always present in aquatic systems. These hypotheses are based on the assumption that phytoplankton communities include only one or a few species of coccoid algae. We examined the diversity and distribution of green‐colored autosporic coccoid algae in Itasca State Park in Minnesota and Arrowwood National Wildlife Refuge in North Dakota using molecular techniques and light microscopy. Our preliminary results indicate a higher level of diversity of coccoid green algae than has been reported in regional flora. Contrary to current hypotheses, communities of coccoid green algae vary among the different lakes.

Understanding the relationships between the mor phology of organisms and the environments in which they live is a broad and unifying goal in fields ranging from organismal biology to ecology to evolutionary biology. Life in aquatic systems is particularly inte resting because of the physical challenges presented by water and the broad array of flow regimes to which organisms have adapted, ranging from the open ocean and wave-swept shores to still lakes and fast-flowing streams. The publication of three volumes in the early 1990s helped to synthesize work on this topic: Denny's (1993) Air and Water, Vogel's (1994) expanded second edition of Life in Moving Fluids with regard to life in fluids in particular, and Wainwright's and Reilly's (1994) Ecological Morphology with regard to the general theme of matches between form, function, and environment in organisms. In the years since the publication of those volumes, a wide range of novel systems have been examined and numerous technol ogical and methodological advances have been made. Our goal in organizing this symposium was to bring together a diverse group of biologists who study the relationship between morphology and aquatic habitat in a variety of marine and freshwater vertebrates, invertebrates and algae, with the hope that through such a diversity of systems and perspectives we could identify general functional strategies observed in organisms subjected to different conditions of flow. This symposium thus provided an opportunity to synthesize work in this area since the 1990s, to present new case studies of established systems at a variety of scales (e.g., seasonal, ontogenetic, size, geographic), and to showcase systems that have only recently been explored in detail. A second goal of this symposium was to highlight the use of several relatively new techniques for examining such systems, such as digital particle image velocimetry (DPIV) and 2D/3D geo metric morphometries. By addressing this breadth of topics, we hoped this symposium would promote new, interdisciplinary approaches to advancing under standing of the relationship between the physical characteristics of aquatic environments and the mor phology of organisms that inhabit them. Several topics ran as common threads through many of the studies presented, with a number of issues emerging as directions for future research on ecomor phological variation across aquatic flow regimes. First, it is clear that accommodating environmental flow is critical for the performance of a wide range of functions in organisms. A major focus of work has been the relationship between flow and locomotor function (Bartol et al. 2008; Blob et al. 2008; Fish et al. 2008; Langerhans 2008; Rivera 2008; Vogel 2008), which could be somewhat more broadly considered as including other functions related to organismal move ment such as dispersal and resistance to dislodgement (Carrington et al. 2008; Koehl et al. 2008; Stewart 2008). However, other vital functions are also sub stantially affected by flow and remain important areas of examination, highlighted by Pratt's (2008) study of feeding efficiency in bryozoans and Mead's (2008) study of the effects of flow on olfactory function in crayfish. A major factor repeatedly identified as critical to the accommodation of the demands of flow, particularly in studies of locomotor function, is the pervasive effects of body size on organismal perfor mance. Although commonly highlighted in interspe cific comparisons (Vogel 2008), the effects of body size are also important factors in performance within species as individuals change size through ontogeny. In some cases, as shown by Bartol et al. (2008) for squid, larger individuals may be capable of a broader range of functions and be able to make successful use of a wider range of morphology than can smaller individuals. In other cases, illustrated by the waterfall climbing fish examined by Blob et al. (2008), certain means of performing in flow may only be possible for

The freshwater green algae Closterium ehrenbergii has been considered as a model for eco-toxicological assessment in aquatic systems. Heat shock proteins (HSPs) are a class of highly conserved proteins produced in all living organisms, which participate in environmental stress responses. In the present study, we determined the cDNA sequences of small heat shock protein 10 (sHSP10) and sHSP17.1 from C. ehrenbergii, and examined the physiological changes and transcriptional responses of the genes after exposure to thermal shock and toxicants treatments. The open reading frame (ORF) of CeHSP10 was 300 bp long, encoding 99 amino acid (aa) residues (10.53 kDa) with a GroES chaperonin conserved site of 22 aa. The CeHSP17.1 had a 468 bp ORF, encoding 155 aa with a conserved C-terminal α-crystallin domain. For heat stress, cells presented pigment loss and possible chloroplast damage, with an up-regulation in the expression of both sHSP10 and sHSP17.1 genes. As for the heavy metal stressors, an increase in the production of reactive oxygen species was registered in a dose dependent manner, with a significant up-regulation of both sHSP10 and sHSP17.1 genes. These results suggest that sHSP genes in C. ehrenbergii may play a role in responses to stress environments, and they could be used as an early detection parameter as biomarker genes in molecular toxicity assessments.