Acute and chronic effects of toxic metals on viability, encystment and bioluminescence in the dinoflagellate Gonyaulax polyedra

Impact of natural events on metal bioaccumulation in Anemonia sulcata

Samples of Anemonia sulcata were collected in 2022 from different areas of the Canary Islands affected by different natural contamination sources, such sandstorms, submarine volcanic activity, continuous rainfall, upwelling and dinoflagellate blooms. Significant differences were observed between the zones for the metals and trace elements analyzed (Al, Zn, Cd, Pb, Ni, Co, Fe, B, Cu, Mg and Li). Anemones from volcanic areas showed higher levels of Cd, Pb and Ni. Individuals from sandstorm areas showed elevated levels of Al, Zn and Fe. Samples collected from areas affected by upwelling processes had higher concentrations of Cu, Mg and Li. Finally, the areas affected by dinoflagellates showed lower levels of Zn, Pb, Fe, Mg and Li. The study reveals how natural phenomena dramatically influence metal accumulation in A. sulcata, which is of great value for anticipating and managing potential problems associated with public health.

Bioluminescent Dinoflagellates as a Bioassay for Toxicity Assessment

Dinoflagellates bioluminescence mechanism depends upon a luciferin–luciferase reaction that promotes blue light emission (480 nm) in specialized luminogenic organelles called scintillons. The scintillons contain luciferin, luciferase and, in some cases, a luciferin-binding protein (LBP), which prevents luciferin from non-enzymatic oxidation in vivo. Even though dinoflagellate bioluminescence has been studied since the 1950s, there is still a lack of mechanistic understanding on whether the light emission process involves a peroxidic intermediate or not. Still, bioassays employing luminous dinoflagellates, usually from Gonyaulax or Pyrocystis genus, can be used to assess the toxicity of metals or organic compounds. In these dinoflagellates, the response to toxicity is observed as a change in luminescence, which is linked to cellular respiration. As a result, these changes can be used to calculate a percentage of light inhibition that correlates directly with toxicity. This current approach, which lies in between fast bacterial assays and more complex toxicity tests involving vertebrates and invertebrates, can provide a valuable tool for detecting certain pollutants, e.g., metals, in marine sediment and seawater. Thus, the present review focuses on how the dinoflagellates bioluminescence can be applied to evaluate the risks caused by contaminants in the marine environment.

Acute Toxicity of Divalent Mercury Ion to Anguilla japonica from Seawater and Freshwater Aquaculture and Its Effects on Tissue Structure

The acute toxicity of divalent mercury ion to Anguilla japonica from seawater and freshwater aquaculture was assessed. In particular, the effects of toxicity on the microstructures of the gill and liver tissues were examined using the hydrostatic method, without feeding, at a water temperature of 20 °C. The median lethal concentrations (LC₅₀) of divalent mercury ion to fishes in seawater and freshwater over various durations were: 24 h = 1.637 and 1.428 mg/L; 48 h = 1.562 and 1.377 mg/L; 72 h = 1.530 and 1.284 mg/L; and 96 h = 1.442 and 1.228 mg/L. The safety mass concentrations were 0.1442 and 0.01228 mg/L, respectively. After exposure to divalent mercury ion, adhesion between the gill lamellae and massive cellular disintegration and necrotic shedding were observed in the gill tissue sections. The liver tissues underwent hyperemia and swelling, with the appearance of blood spots, swelling of the hepatocyte mitochondria, dilation of the rough endoplasmic reticulum, and intercellular inflation.

Comparison of the Qwiklite algal bioluminescence test with marine algal growth rate inhibition bioassays

Although marine algal bioassays based on growth rate inhibition over 72-96 h have been widely used to assess the toxicity of contaminants in waters and sediments, changes in pH over the test duration can lead to changes in contaminant speciation and consequently an under- or over-estimation of toxicity. In addition, high cell densities are used in order to obtain a detectable response, further reducing the tests' environmental relevance in marine waters. There is a need for rapid acute tests with ecologically relevant test endpoints that may be used as surrogates for longer-term chronic tests. This study compares the sensitivity and reproducibility of a rapid marine dinoflagellate (Pyrocystis lunula) bioluminescence test (QwikLite) with standard algal growth rate bioassays (Nitzschia closterium and Entomoneis c.f. punctulata) using ammonia and several antifouling agents (tributyltin [TBT], copper, and diuron) as reference toxicants. QwikLite was of similar sensitivity to ammonia as standard algal growth rate tests, but was less sensitive to copper, diuron and TBT, with 24-h EC50 values of 10 +/- 1.1 mg N/L, 0.128 +/- 0.021 mg Cu/L, 19 +/- 13 mg diuron/L, and 0.226 +/- 0.028 mg TBT/L. Inter-test precision using different batches of P. lunula was generally acceptable. On the basis of NOEC values, QwikLite was more sensitive to copper and ammonia at 25 degrees C than at 21 degrees C. QwikLite shows promise as a rapid, inexpensive screening test for acute toxicity of contaminants in marine environments.

Chemical speciation and toxicity of metals assessed by three bioluminescence-based assays using marine organisms

Metal toxicity is a function of the biology of the target organism and the chemical speciation of the metal. The toxicity of 11 metals was assessed with three cell-based bioassays based on marine organisms: the bacterium Photobacterium phosphoreum of the Microtox bioassay, an environmental strain of P. phosphoreum, and photocytes isolated from the brittlestar Ophiopsila californica. Metal speciation was calculated for three commonly used media: NaCl-based Microtox bioassay medium, artificial seawater glycerol, and artificial seawater. Decreased bioluminescence was considered a proxy for cell toxicity. In all three assays the elements Cd and Hg exhibited similar speciation as well as similar toxicity profiles. The element Cu was toxic in all three assays despite different metal speciation for the P. phosphoreum bioassay. The element Ag was toxic to both bacterial strains but not to photocytes despite a similar chemical speciation for all three assays. In general, the Microtox bioassay was sensitive to all metals (except Pb), whereas the photocytes were the least sensitive to the metals. The heightened response of the Microtox bioassay probably resulted from a combination of the limited complexing power of the medium and the greater sensitivity of the bacterial strain.