Tolerance of Physocypria kraepelini (Crustacean, Ostracoda) to water-borne ammonia, phosphate and pH value

A review of the toxic effects of ammonia on invertebrates in aquatic environments

Aquatic invertebrates are the organisms most susceptible to ammonia toxicity. However, the toxic effects of ammonia on invertebrates are still poorly understood. This study reviews the research progress in ammonia toxicology for the period from 1986 to 2023, focusing on the effects on invertebrates. Through examining the toxic effects of ammonia at different levels of organization (community, individual, tissue and physiology, and molecular) as well as the results from omics studies, we determined that the most significant effects were on the reproductive capacity of invertebrates and the growth of offspring, although different populations show variation in their tolerance to ammonia, and tissues have varied potential to respond to ammonia stress. A multicomponent analysis is an in-depth technique employed in toxicological studies, as it can be used to explore the enrichment pathways and functional genes expressed under ammonia stress. This study comprehensively discusses ammonia toxicity from multiple aspects in order to provide new insights into the toxic effects of ammonia on aquatic invertebrates.

Ammonia and chromate interaction explains unresolved Hyalella azteca mortality in Flanders' sediment bioassays

Agricultural, industrial and household chemicals are emitted in large rivers along populated areas, transported by water and deposited in sediments, posing (eco)toxicological risks. Sediments have received less attention than surface waters, likely because of the intrinsic complexity of interactions between sediment constituents complicating correct framing of exposures. Sadly, thorough assessment of the in situ behavior of sediment constituents in bioassays is often not practical. Alternatively, we related physicochemical properties of sediments from field testing to results from bioassays. The case study covers Flemish sediment (incl. Scheldt and Meuse) and mortality of Hyalella azteca, a sensitive bio-indicator. Though variable across Flanders' main water bodies, heavy metals and ammoniacal nitrogen dominate the observed toxicity according to toxic unit (TU) assessments. Depending on the water body we explain between 50 and 90% of the variance in the observed H. azteca mortality, substantially more than previous ecotoxicity studies. We attribute the remaining variance to potential incoherently documented biophysicochemical sediment properties and concentrations of non-target biocides, testing conditions/set-ups and/or species variabilities. We discuss the relative influence of heavy metals/metaloxides, nitrogen (e.g. fertilizer), polycyclic aromatics and organochlorides. We highlight both direct and indirect mortality mechanisms. We note potential synergetic mixture effects between ammoniacal nitrogen and chromium. Such synergy may be phenomenological of 'standard' aerobic bioassays, and prove a complementary method alongside the 'acid-volatile sulfide test' to more effectively link concentration to toxicity. Future study ought to include variation in biophysicochemical properties between sampling locations and batch bioassays. Our approach enables water managers to interpret their monitoring data by converting sediment concentrations to H. azteca mortality and prioritize substances that contribute most.

Bioconcentration of Organotin Cations during Molting Inhibits Heterocypris incongruens Growth

The densely populated North Sea region encompasses catchments of rivers such as Scheldt and Meuse. Herein, agricultural, industrial, and household chemicals are emitted, transported by water, and deposited in sediments, posing ecological risks. Though sediment monitoring is often costly and time-intensive, modeling its toxicity to biota has received little attention. Due to high complexity of interacting variables that induce overall toxicity, monitoring data only sporadically validates current models. Via a range of concepts, we related bio-physicochemical constituents of sediment in Flanders to results from toxicity bioassays performed on the ostracod Heterocypris incongruens. Depending on the water body, we explain up to 90% of the variance in H. incongruens growth. Though variable across Flanders' main water bodies, organotin cations and ammonia dominate the observed toxicity according to toxic unit (TU) assessments. Approximately 10% relates to testing conditions/setups, species variabilities, incoherently documented pollutant concentrations, and/or bio-physicochemical sediment properties. We elucidated the influence of organotin cations and ammonia relative to other metal(oxides) and biocides. Surprisingly, the tributylin cation appeared ∼1000 times more toxic to H. incongruens as compared to "single-substance" bioassays for similar species. We inferred indirect mixture effects between organotin, ammonia, and phosphate. Via chemical speciation calculations, we observed strong physicochemical and biological interactions between phosphate and organotin cations. These interactions enhance bioconcentration and explain the elevated toxicity of organotin cations. Our study aids water managers and policy makers to interpret monitoring data on a mechanistic basis. As sampled sediments differ, future modeling requires more emphasis on characterizing and parametrizing the interactions between bioassay constituents. We envision that this will aid in bridging the gap between testing in the laboratory and field observations.

Protection of Danio rerio from cadmium (Cd2+) toxicity using biological iron sulfide composites

Cadmium (Cd²⁺) pollution has become a global environmental problem. This study is the first to demonstrate the feasibility and effects of applying biological iron sulfide composites (BISC) for the protection of Cd²⁺ exposed fish, aiming at remediation of Cd²⁺ polluted waters during emergency pollution events. Experimental results indicate that BISC can remove Cd²⁺ efficiently and significantly protect Cd²⁺ exposed Danio rerio, by increasing its overall survival rates. Meanwhile, the protective effect of BISC is significantly enhanced with optimized BISC dosing ratios of 2.4 or more, as well as with more rapid onset of BISC dosing following Cd²⁺ exposure and in water with higher pH levels in the range of 6-8, with D. rerio survival rates increased by more than 90% (P = 0.05). Additionally, BISC confers advantages over SRB and combinations of its constituents, with effective removal of Cd²⁺ and increasing survival rates of Cd²⁺ exposed D. rerio.

Geographical distribution of zooplankton biodiversity in highly polluted running water ecosystems: Validation of fine-scale species sorting hypothesis

Dispersal, rather than species sorting, is widely recognized as the dominant driver for determining meta-community structure at fine geographical scales in running water ecosystems. However, this view has been challenged by a recently proposed "fine-scale species sorting hypothesis," where community structure can be largely determined by an environmental gradient formed by local pollution at fine scales. Here, we tested this hypothesis by studying community composition and geographical distribution of metazoan zooplankton in a heavily polluted river-the North Canal River in the Haihe River Basin, China. Analysis of similarity (ANOSIM) showed that the community composition of metazoan zooplankton differed significantly (p = .001) along the environmental gradient. Ammonium (NH4-N) was the leading factor responsible for changes in zooplankton community structure and geographical distribution, followed by total dissolved solid (TDS), Na, dissolved oxygen (DO) and temperature (T). Variation partitioning revealed a larger contribution of environmental variables (21.6%) than spatial variables (1.1%) to the total explained variation of zooplankton communities. Our results support that species sorting, rather than dispersal, played a key role in structuring communities. Threshold Indicator Taxa ANalysis (TITAN) also revealed significant change points at both taxon and community levels along the gradient of NH4-N, providing further support for the influence of environmental variables on zooplankton communities. Collectively, we validate the fine-scale species sorting hypothesis when an environmental gradient exists in running water ecosystems at fine geographical scales. However, future studies on interactions between pollutants and zooplankton communities are still needed to better understand mechanisms responsible for the meta-community dynamics.

The influence of gravity and light on locomotion and orientation of Heterocypris incongruens and Notodromas monacha (Crustacea, Ostracoda)

For future manned long-d uration space missions, the supply of essentials, such as food, water, and oxygen with the least possible material resupply from Earth is vital. This need could be satisfied utilizing aquatic bioregenerative life support systems (BLSS), as they facilitate recycling and autochthonous production. However, few organisms can cope with the instable environmental conditions and organic pollution potentially prevailing in such BLSS. Ostracoda, however, occur in eu- and even hypertrophic waters, tolerate organic and chemical waste, varying temperatures, salinity, and pH ranges. Thus, according to their natural role, they can link oxygen liberating, autotrophic algae, and higher trophic levels (e.g., fish) probably also in such harsh BLSS. Yet, little is known about how microgravity (µg) affects Ostracoda. In this regard, we investigated locomotion and orientation, as they are involved in locating mating partners and suitable microhabitats, foraging, and escaping predators. Our study shows that Ostracoda exhibit altered activity patterns and locomotion behavior (looping) in µg. The alterations are differentially marked between the studied species (i.e., 2% looping in Notodromas monacha, ~50% in Heterocypris incongruens) and also the thresholds of gravity perception are distinct, although the reasons for these differences remain speculative. Furthermore, neither species acclimates to µg nor orientates by light in µg. However, Ostracoda are still promising candidates for BLSS due to the low looping rate of N. monacha and our findings that the so far analyzed vital functions and life-history parameters of H. incongruens remained similar as under normal gravity conditions despite of its high looping rate.

Despite disorientation in microgravity, seed shrimp could form part of the food chain in artificial ecosystems designed for space missions. Jessica Fischer and Christian Laforsch of Germany’s University of Bayreuth investigated how simulated microgravity changed the movement of two species of seed shrimp (Ostracoda). Ostracoda can cope in unstable conditions and are being considered as food for fish in aquatic bioregenerative life support systems (BLSS) in manned space missions. Fish fed on Ostracoda that eat algae in these systems could form an important source of proteins for humans. Notodromas monacha and Heterocypris incongruens moved around in loops when exposed to simulated microgravity, but N. monacha did not loop as much. Looping movements suggest that gravity is an important orientational cue. Previous studies showed Ostracoda survived and reproduced successfully for months in space despite their looping behavior. Further studies are needed on N. monacha, since its low looping behavior could mean lower energy consumption making it better qualified for BLSS.