Manganese dichloride

Long-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Conducted to an acceptable scientific standard.

Data source

Reference

Reference Type:

publication

Title:

Comparative Study of the Effects of Metals on the Settlement of Crassostrea gigas

Author:

WatlingHR

Year:

1983

Bibliographic source:

Bull. Environ.Contam.Toxicol. 31, 344-351

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The effects of up to eight elements, including manganese, on C.gigas larval settlement and spat growth were investigated using a single larval culture for each comparative test. The metal concentrations were chosen in the range to cause sub-lethal rather than lethal effects. Lethal concentrations (LC50; causing 50% mortality in a specified period) were not determined except where they occurred in the selected concentration range. Experimental observations included growth and behaviour in addition to mortality.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Mn2+

IUPAC Name:

Mn2+

Details on test material:

Form of the test substance: Mn2+

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 10 and 20 µg/l of Mn2+.
- Sampling method: Samples from each treatment were collected at selected intervals and behaviour and structure examined.

Test solutions

Vehicle:

no

Details on test solutions:

Treatments, 10 and 20 µg/l of Mn2+ prepared in triplicate, were continued throughout the 20-day experiment.

Test organisms

Test organisms (species):

other aquatic mollusc: Crassostrea gigas

Details on test organisms:

C. gigas larvae and spat were obtained from hatchery stock cultures . Hatchery procedure included the sieving of larvae and spat through nylon screens of selected mesh sizes. Thus the range of individual sizes was restricted at the beginning of each experiment. Samples from each treatment were collected at selected intervals and behaviour and structure examined. Measurements made included width across the value for larvae and length of spat.

Larvae were encouraged to settle on discs of black PVC placed in the bottom of each beaker. These discs were slightly arched so that both upper and lower surfaces were available for settlement. The number of larvae settling on the black discs in each beaker was counted but spat were not scraped off. Those which settled in the presence of metals were grown for an additional period in clean water.

Small cultchless-spat were suspended on a 400 µm nylon mesh; older spat were suspended on screens of larger mesh size. Samples were examined daily and measured at intervals during both the treatment and the succeeding period in clean sea water. Gaping individuals were removed. Spat in the size range tested may have been dead for up to two days before the shells gaped.

Study design

Test type:

static

Water media type:

saltwater

Total exposure duration:

20 d

Test conditions

Nominal and measured concentrations:

10 and 20 µg/l of Mn2+

Details on test conditions:

TEST MEDIUM
The experimental solutions were prepared to contain a combination of the flagellates Monochrysis lutherii, Isochrysis galbana, Chaetoceros calcitrans and Tetraselmis chui to give a final combined concentration of 150 cells/µl.
The algal mix was supplied daily from the hatchery.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Growth and settlement.

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

14 d

Dose descriptor:

other: effect on growth

Effect conc.:

10 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Effect concentrations 2

Duration:

20 d

Dose descriptor:

NOEC

Effect conc.:

20 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Settlement

Details on results:

Settlement was plotted on a daily basis and settlement patterns for zinc, cadmium and copper illustrated three possible effects:

a) Maximum settlement delayed with respect to that in the control (zinc, also lead).

b) Maximum settlement coincident with that in the control (cadmium, also MANGANESE, nickel and chromium).

c) Maximum settlement occurring earlier than that in the control (20 µg/l copper, also 20 µg/l cobalt).

The only element which appeared to promote metamorphosis and settlement was copper, for which 80 and 95% of the larvae settled in the 10 and 20 µg/l treatments respectively, compared with 72% in the controls and 68% in the presence of manganese. All other elements tested caused a significant decrease in the total numbers of larvae settling (between 35-45%).

The effects of manganese on 51-day old cultchless C. gigas spat were recorded (see table 1).
All the metals which were tested caused a reduction in growth during the 14-day treatment period. However, recovery was such that individuals in all treatments were approximately the same size as those in the controls after a further 14 days in clean sea water.

Any other information on results incl. tables

Table 1:

Growth and recovery of 51 -day old cultchless spat (mean length 3.7 mm) exposed to eight elements (results as mean spat length (mm)).

Treatment	After 14 days treatment	After further 14 days in clean water
Control	6.3	8.2
Control	6.2	8.2
Mn 10 µg/l	5.2	7.9
Mn 20 µg/l	5.4	7.6

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

The 20-day No Observable Effect Concentration (NOEC) for settlement is 0.02 mg Mn/L. The 14-day No Observable Effect Concentration (NOEC) for growth is 0.01 mg Mn/L.