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Ecotoxicological information

Toxicity to other aquatic organisms

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Administrative data

Endpoint:
toxicity to other aquatic vertebrates
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study design and performance followed state-of-the-art protocols for microcosm systems. Control treatments were included for all statistical comparisons and characteristics of water composition (background and treatments) were analytically verified. Study conditions relevant for EU waters.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2012
Report Date:
2012

Materials and methods

Test guideline
Qualifier:
no guideline required
Principles of method if other than guideline:
Custom-designed study. Each mesocosm study is designed to answer specific questions; nonetheless various guidance documents that describe the basic principles of this kind of studies when performed for risk assessment were used as general guidance. Although these guiding documents concern fresh water mesocosm studies, the addressed issues were taken into account as much as possible during the marine mesocosm study that is described in this report.

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
The concentration of total dissolved zinc in the water column was analysed three times per week using new 60 mL polypropylene syringes (BD Plastipak) in each mesocosm. Filtration of the water was performed immediately after sampling, using an acid washed 0.45 μm pore size cellulose acetate membrane filter (25 mm Ø, Whatman) contained in a polypropylene filter holder (25 mm, Millipore Swinnex), connected to the syringe by luer lock. During filtration, the first 5 mL of the filtrate was discarded; the last 5 mL were retained. The filtrate was collected in 50 mL narrow mouth LDPE polythene bottles (Kautex) and acidified to pH<2 (HCl, Merck Suprapur). Sampling for zinc always started with the lowest zinc concentration (control) mesocosms, and ended with the highest concentration. To avoid contamination after sampling the sample bottles were packed in clean polythene zip-bags for transport. Samples were transported within one hour to the laboratory..
Sampling for the concentration of nutrients, dissolved organic carbon (DOC) and hardness was performed every other week by immersion of the sample bottles (supplied by the laboratory) in the mesocosm while avoiding the collection of the surface micro-layer. Sample bottles were rinsed with sample water twice before sampling. Samples were transported to the laboratory for analysis within one hour after collection.

Test solutions

Vehicle:
no
Details on test solutions:
Test water was Northsea natural water. On April 19, 2011, seawater for the mesocosms was collected by pre-cleaned road tanker from the Oosterschelde, a relatively pristine tidal bay in direct connection with the North Sea. It was transported to the test facility, where it was added to all mesocosms simultaneously. The time between collection and introduction in the mesocosms was kept as short as possible and was always less than 10 hours, this in order to provide a healthy inoculum of planktonic organisms in the mesocosms. Larger macro invertebrates and macro algae were introduced during the following days.The mesocosms were installed with approximately 20 cm natural sediment and a water column of approximately 140 cm.
The sediment used for this study was collected from the coastal North Sea and was distributed equally over the mesocosms on April 18, 2011. The sandy sediment consisted for almost 80% of a grain size between 125 and 250 μm and contained approximately 0.5% organic matter.

Test organisms

Test organisms (species):
other: Species of macro-algae, crustaceae, sponges, mollusca and annelids were introduced. Zoo- and phytoplankton and other macro invertebrates were introduced with the water and sediment.
Details on test organisms:
Zoo- and phytoplankton and other macro invertebrates were introduced with the water and sediment.
The following species were deliberately introduced (individuals were introduced in the mesocosms following a random table, to ensure comparable starting material in all mesocosms):
Ulva intestinalis (sea lettuce; Macro algae; Chlorophyta)
Halichondria panicea (bread-crumb sponge; sponges; Porifera)
Corophium volutator (mud shrimp; Crustacea; Amphipoda)
Littorina littorea (common periwinkle; Mollusca; Gastropoda)
Cerastoderma edule (cockle; Mollusca; Bivalvia)
Arenicola marina (lugworm; Annelids; Polychaeta)

Study design

Test type:
static
Water media type:
saltwater
Limit test:
no
Total exposure duration:
83 d

Test conditions

Hardness:
The total hardness of the mesocosm water was 59 mmol/L on day –15. It steadily increased to about 63 mmol/L on day 41. From then on, the values decreased again and at the end of the study the total hardness was approximately 55 mmol/L. The development was comparable for all mesocosms
Test temperature:
The water temperature in the mesocosms varied in time due to the ambient conditions (between 17°C and 21°C), but was comparable in all mesocosms
pH:
At the start of the experiment the pH was 8.5. During the following two weeks it dropped to approximately 8.2, which level remained until about 14 days after the start of the exposure period. From then on, the pH increased with the same rate in all mesocosms until day 28.
Differences between mesocosms started to appear after day 28, when the increase of the pH accelerated (up to pH 9.2) in the control mesocosms and similarly in the zinc treatments up to 12 μg Zn/L . In the higher treatments, the increase was less pronounced. At the end of the experiment, all pH levels were similar again.
Dissolved oxygen:
Supported by the continuous aeration of the water column, the dissolved oxygen concentrations in the mesocosms remained between 90 and 110% of the maximum saturation level
Salinity:
The salinity of the water that was added to the mesocosms during installation was 32. During the following 4 weeks the salinity rose due to evaporation to approximately 33‰. From then on, the salinity was actively maintained between 32 and 33‰ by adding demineralized water to compensate for evaporation losses.
Nominal and measured concentrations:
Constant concentration of total dissolved zinc in the water column was maintained by regular sampling and dosing up to required concentrations. To this end, the test substance was applied continuously to compensate for dissipation of the dissolved zinc due to sorption to sediment, suspended particles and the tank wall, due to bioaccumulation, etc.
Treatment levels were 5.6, 7.5, 12, 43, and 91 µg Zn/l. background was 2.7µg Zn/l on average.
Details on test conditions:
The mesocosms used for this study were intended to mimic a shallow soft sediment marine ecosystem. This type of ecosystem is common along European coasts.

Results and discussion

Effect concentrations
Duration:
83 d
Dose descriptor:
other: No Observed Ecological Adverse Effect Concentration
Effect conc.:
12 µg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
dissolved
Basis for effect:
other: primary production, grwoth of Littorina littorea
Details on results:
The dataset shows a consistent picture of the impact of the continuous exposure of dissolved zinc on the mesocosm communities during 83 days. The two highest treatment levels of 91 and 43 μg Zn/L caused clear direct and indirect effects on various taxa. Indications that the primary production was negatively affected were seen in different water characteristics, and seemed to be related to reduced development of the sessile algae. Macro algae took advantage of the reduced competition, but gastropods that mainly feed on sessile algae showed indications of reduced food availability. The phytoplankton community showed no indications of being affected by the treatments. Zooplankton, especially Harpacticoid copepods showed a strong reduced population density at the highest treatment level.
At treatment levels 5.6, 7.5 and 12 μg Zn/L, no negative effects were observed, but indications were found of a slight stimulation of the productivity, that might be related to zinc essentiality. Since this did not result in substantial changes in the composition or functioning of the mesocosm ecosystem these effects are not considered as being ecological adverse.





Reported statistics and error estimates:
For single species/endpoints, the significance of differences between the controls and the treated mesocosms was tested by using a one-way ANOVA with a Dunnett’s multiple comparison test as post-test for single data sets. In case of time series a two-way ANOVA with Bonferroni post-test for time series was applied. Both analyses are contained in and were performed with the software package GraphPad Prism™ version 4.03 (January 21, 2005).
Principal Response Curve (PRC) analyses were performed in order to evaluate the response in time of the phytoplankton and the zooplankton community on the treatment. For these analyses, the dominant species were selected and the less abundant species were combined in taxonomic groups. For the PRC analysis the data of zooplankton and phytoplankton were centred per species. The results of the PRC analysis were summarised in a PRC plot per group, showing the canonical coefficient for each concentration at each observation time. The value of this coefficient is set at 0 for the control.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
Technically sound, extensively documented study in natural seawater from the Northsea, so relevant for EU marine conditions.
Executive summary:

The impact of zinc on marine mesocosm communities was studied in a large scale , state-of-the-art outdoor mesocosm study with natural seawater from the Northsea. The results show a consistent picture: the two highest treatment levels of 91 and 43 μg Zn/L caused clear direct and indirect effects on various taxa. Indications that the primary production was negatively affected were seen in different water characteristics, and seemed to be related to reduced development of the sessile algae. Macro algae took advantage of the reduced competition, but gastropods that mainly feed on sessile algae showed indications of reduced food availability. The phytoplankton community showed no indications of being affected by the treatments. Zooplankton, especially Harpacticoid copepods showed a strong reduced population density at the highest treatment level. At treatment levels 5.6, 7.5 and 12 μg Zn/L, no negative effects were observed, but indications were found of a slight stimulation of the productivity, that might be related to zinc essentiality. Since this did not result in substantial changes in the composition or functioning of the mesocosm ecosystem these effects are not considered as being ecological adverse. The No Observed Ecological Adverse Effect Concentration (NOEAEC) derived from this study was set at 12 μg Zn/L.