Manganese

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

supporting study

Justification for type of information:

See the read-across report attached in Section 13.

Reason / purpose for cross-reference:

read-across source

Remarks on result:

not measured/tested

Remarks on result:

not measured/tested

Remarks on result:

not measured/tested

Remarks on result:

not measured/tested

Reference 2

Endpoint:

bioaccumulation in aquatic species: invertebrate

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

April 2014 to September 2015

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

In order to determine the metal-accumulating ability of the burrowing crab, Neohelice granulata, concentrations of Mn in soft tissues of adult specimens were measured. Subsequently, the bioconcentration factor (BCFs) was determined using levels of concentrations previously obtained in intertidal sediments.

GLP compliance:

not specified

Remarks:

Published literature

Test organisms (species):

other: Neohelice granulata

Route of exposure:

other: Intertidal water and sediment

Test type:

field study

Water / sediment media type:

natural water: marine

Details on test conditions:

The Bahia Blanca Estuary is located in the southwestern Atlantic Ocean (38°45′–39°40’S and 61°45′–62°30’W). It is a mesotidal coastal plain estuary extended over 2 300 km^2, formed by several tidal channels, islands, and extensive tidal flats with patches of low salt marshes dominated by crab caves of the burrowing crab Neohelice granulata.
Sampling of males and females of N. granulata was seasonally performed from April 2014 to September 2015 in two locations within the Bahía Blanca estuary.
Cuatreros Port (CP) located in the inner part of the estuary receives the contribution of the Sauce Chico River and the Saladillo de García stream, which drain an area of approximately 1 600 km^2 that involve large extensions of agricultural fields. Rosales Port (RP), located in the middle part of the estuary, is influenced by Punta Alta city (~ 60 thousand inhabitants) and its sewage outfall, which discharges into the estuary with no treatment. Samples of intertidal superficial sediment (n = 3 for each site) for determination of metal concentrations were taken with PVC cores (100 mm i.d.; 150 mm long). Afterwards, they were kept in polyethylene bags, carried to the laboratory in refrigerated boxes and stored up to maximum of 48 h at 4 °C. Sampling was done in the morning at low tide. In the laboratory, sediment samples were oven dried at 60 ± 5 °C for 4 days. Then, samples were ground in a porcelain mortar and they were sifted through stainless steel meshes until fine particles (< 63 μm) were obtained. Finally, they were stored in plastic desiccators until their analytical treatment.
Crabs were caught using a crab trap with bait during high tide. Only adult males and females (i.e., maximum width carapace > 15 mm for males and > 17 mm for females) were selected. Individuals of each sex were placed in two plastic boxes with estuarine water and were transported to the laboratory where they were washed with distilled water and preserved at − 20 °C until analysis. The soft tissues obtained by dissection of the crab samples were pooled (five or six specimens) according to sex and location and placed in Petri dishes in an oven at 50 °C until constant weight was reached. Then, dried samples were grinded in a porcelain mortar for homogenisation. Acid digestion of crab tissues and fine sediment was performed according to the methodology described previously. Samples of 500 ± 50 mg were mineralised with 5 mL concentrated HNO3 (65 %) and 1 mL concentrated HClO4 (70 – 72 %) and placed in a heated glycerin bath at 120 ± 10 °C until complete mineralisation. The residue was completed with diluted HNO3 (0.7 %) up to 10 mL into centrifuge tubes. All glassware and equipment used for dissection and drying of samples were cleaned with diluted nitric acid (5 % v/v) to prevent contamination.

Value:

< 1

Basis:

whole body d.w.

Details on results:

The concentration of all metals assessed, except Mn in the fine sediments, were significantly higher in Rosales Port than Cuatreros Port (p < 0.005). However, the concentrations found in burrowing crabs at both sites did not exhibit the same behaviour.
The availability of metals to be bioaccumulated is dependent upon the concentration of the element within the sediment as well as its geochemical behaviour and physical-chemical conditions within that matrix. On the other hand, for crustaceans, several intrinsic factors, for instance age, size, stage in the molt cycle and reproductive cycle, may influence bioaccumulation process.
The results of this study showed a BCF < 1 for Mn.
Differences between sites and/or sexes were analysed (i.e., two-way ANOVA).
Significant differences between the two sites were found for Mn, with concentrations significantly greater in crabs from Rosales Port (Mn: 64.20 ± 16.93 μg/g dw vs 47.51 ± 16.69 μg/g dw, p = 0.002).
In this study, significant differences between sexes were found for Mn in both sites (p < 0.003), being superior in males than females in all cases.

Reported statistics:

Samples were considered in the dataset for statistical treatment only if they represented less than 40 % of the total samples. Otherwise, only descriptive statistics was performed using the detectable values. Two-way analysis of variance (ANOVA) was performed to analyze possible interactions between sites and sexes. Statistical analyses were carried out with appropriate software (IBM SPSS Statistics 22.0 and Infostat version 2016- Grupo InfoStat, FCA, Universidad Nacional de Córdoba, Argentina). We used bioconcentration factors (BCFs) to analyze the relationship between heavy metals in crabs and sediment. It was calculated as BCF = Corg/Csed, where Corg is the concentration of metal in the organism and Csed is the concentration of the same metal in the environment, intertidal superficial fine sediment in this case.

Metal concentration (μg/g dw) in intertidal fine sediment and burrowing crabs from the Bahia Blanca estuary.

	Mn
Cuatreros Port
Sediment (n = 18)
Mean	346.86
STD	82.11
Min	224.45
Max	516.10
No. MDL	0
Male soft tissue (n = 12)
Mean	57.72
STD	15.03
Min	40.50
Max	98.21
BCF	0.17
No. MDL	0
Female soft tissue (n = 12)
Mean	36.37
STD	10.15
Min	20.87
Max	59.06
BCF	0.11
No. MDL	0
Rosales Port
Sediment (n = 18)
Mean	303.98
STD	46.02
Min	220
Max	383.65
No. MDL	0
Male soft tissue (n = 10)
Mean	68.22
STD	15.02
Min	49
Max	97.69
BCF	0.22
No. MDL	0
Female soft tissue (n = 7)
Mean	58.45
STD	18.98
Min	40
Max	85.03
BCF	0.19
No. MDL	0

Validity criteria fulfilled:

not applicable

Conclusions:

Under the conditions of the study the BCF for Mn in the burrowing crab, Neohelice granulata, was < 1.

Executive summary:

In order to determine the metal-accumulating ability of the burrowing crab, Neohelice granulata, in the intertidal areas of the Bahía Blanca estuary, concentrations of Mn in soft tissues of adult specimens were measured. Subsequently, the bioconcentration factor (BCF) was determined using levels of concentrations previously obtained in intertidal sediments. The results showed concentrations above the detection limit in soft tissues of male and female crabs.

The availability of metals to be bioaccumulated is dependent upon the concentration of the element within the sediment as well as its geochemical behaviour and physical-chemical conditions within that matrix. For crustaceans, several intrinsic factors, for instance age, size, stage in the molt cycle and reproductive cycle, may influence bioaccumulation process.

Differences between sites and/or sexes were analysed by two-way ANOVA.  Significant differences between the sites were found for Mn, with concentrations significantly greater in crabs from Rosales Port (Mn: 64.20 ± 16.93 μg/g dw vs 47.51 ± 16.69 μg/g dw, p = 0.002).  In this study, significant differences between sexes were found for Mn in both sites (p < 0.003), being superior in males than females in all cases.

Under the conditions of the study the BCF for Mn in the burrowing crab, Neohelice granulata, was < 1.

Reference 3

Endpoint:

bioaccumulation in aquatic species, other

Remarks:

Pelagic Arctic marine food web species, including algae, plankton, cod, seabirds and ringed seals.

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

May 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

Trace elements were measured in ice algae, three species of zooplankton, mixed zooplankton samples, Arctic cod (Boreogadus saida), ringed seals (Phoca hispida) and eight species of seabirds to examine the trophodynamics of metals in an Arctic marine food web. All samples were collected in 1998 in the Northwater Polynya (NOW) located between Ellesmere Island and Greenland in Baffin Bay.

GLP compliance:

not specified

Remarks:

Published literature

Test organisms (species):

other: See below.

Details on test organisms:

Zooplankton including ice algae, the calanid copepod Calanus hyperboreus, the amphipod Themisto libellula, and the mysid, Mysis oculate; Arctic cod (Boreogadus saida); seabirds namely Dovekie (Alle alle), Black-legged kittiwake (Rissa tridactyla), Black guillemot (Ceppus grille), Thick-billed murre (Uria lomvia), Ivory gull (Pagophilia eburnean), Northern fulmar (Fulmarus glacialis), Glaucus gull (Larus hyperboreus) and Thayer’s gull (Larus thayeri); and ringed seal (P. hispida, age 8 to 10 years only).

Samples were collected during May 1998 from the CCGC Pierre Radisson in the Northwater Polynya located in northern Baffin Bay. Zooplankton were collected from vertical tows from bottom to surface using a 1-m diameter zooplankton net with 520-μm mesh. After collection, zooplankton were either unsorted (“mixed”) or sorted by species, including the amphipod Themisto libellula, the calanid copepod Calanus hyperboreus and the mysid, Mysis oculata. Arctic cod Boreogadus saida were opportunistically sampled at one location using hand-held nets. Sea birds were collected by shotgun from a Zodiac boat, measured and sexed, and dissected for liver and muscle samples. Ringed seal P. hispida (age 8 to 10 years only) liver and muscle samples were obtained from Inuit hunters from Ausuittuq (Grise Fijord) in Ellesmere Island and Qânâq in north western Greenland. All samples were placed in Whirl-Pak bags, cryo-vials or aluminium foil and frozen until analysed for stable isotopes or elements.

Route of exposure:

other: Aqueous and feed

Test type:

field study

Water / sediment media type:

natural water: marine

Details on test conditions:

Determination of relative trophic level:
Relative trophic levels were determined using equations derived from a model reported previously. Trophic level was determined relative to the copepod C. hyperboreus which we assumed occupied trophic level (TL) 2 as a primary herbivore (although it is known to be an omnivore during low productivity periods in the winter).
For each individual zooplankton, fish and ringed seal sample (whole or muscle), the following equation was used:

TLconsumer = 2 + (δ^15Nconsumer -7.7) / 3.8

For sea birds, rearing studies suggest that diet-tissue isotopic enrichment factor is + 2.4% and so we adopted the TL model:

TLbird = 3 + (δ^15Nbird -10.1) / 3.8

Data analyses were done using SYSTAT version 10.0 (SPSS Inc, Chicago IL, USA). As a pelagic counterpart to benthic ice algae, the published data for POM were included in the food web analyses.
Sex differences in metal accumulation were not observed for most elements in all seabird species and ringed seals. In general, both sexes of most species in this study exhibited similar bioaccumulation and biodilution patterns, therefore both sexes were pooled. Metals were log-transformed to normalize the distribution, and simple linear regressions were performed using metal concentrations in muscle and whole animal tissue vs. trophic level (as indicated by δ^15N values) as a possible tool to estimate metal levels in the food web. Muscle tissue concentrations were used in order to enable comparisons with other biomagnification studies which usually examined muscle tissue from vertebrates and whole invertebrates. Metals were regressed against δ^13C values in seabird samples to assess tissue-specific and possible diet-specific variation within the seabird portion of the food web. However, δ^13C values were not included in metal trophodynamics for the whole food web because δ^15N and δ^13C of all sampled biota are correlated (p ≤ 0.01). This correlation can be explained by the smaller trophic fractionation of δ^13C (≈ 1 ‰ to 2 ‰) that happens in unison with δ^15N fractionation (3.2 - 3.6 ‰). Element values below detection limits were not included in the regressions, although the total numbers of data points above detection limit are included to indicate the degree of “censoring”. Correlations of element concentrations in liver vs. muscle samples for each ringed seal and bird species were Bonferroni-corrected to provide protection for multiple tests.

Remarks on result:

not measured/tested

Remarks:

Mn was shown to neither biomagnify nor biodilute through the food web.

Details on results:

Manganese was consistently found above detection limits in all biota.
Results showed non-significant slopes (p = 0.029 to 0.792) were found for some elements, including manganese, indicating that those elements neither biomagnify nor biodilute through the food web.
Element concentrations were typically higher in liver tissue than in muscle tissue for seals and seabirds. Correlations of various elements in liver against muscle can provide insights into how elements are distributed throughout the body. When all bird species were grouped together, most element concentrations in liver tissue were significantly correlated with muscle tissue. There were exceptions however, including Mn.
A lack of correlation with trophic level was observed for Mn.

Mean and standard deviations for Mn (μg/g ww) for whole (W), liver (L), and muscle (M) samples.

Species Code	Tissue	n	Mn
IALG	W	3	5.2 ± 0.003
CHYP	W	3	0.29 ± 0.07
ZOOP	W	4	0.43 ± 0.37
TLIB	W	3	0.46 ± 0.14
MOCC	W	3	1.14 ± 0.32
ACOD	W	1	1.21
	L	2	0.79 – 0.91
DOVE	M	10	0.65 ± 0.07
	L	9	3.32 ± 0.31
BLKI	M	10	0.52 ± 0.08
	L	10	3.52 ± 0.67
BLGU	M	10	0.61 ± 0.09
	L	10	2.67 ± 0.42
TBMU	M	10	0.49 ± 0.05
	L	10	3.28 ± 0.30
IVGU	M	5	0.50 ± 0.12
	L	2	2.05 – 2.36
NOFU	M	10	0.68 ± 1.32
	L	10	4.29 ± 0.55
GLGU	M	10	0.54 ± 0.05
	L	9	3.72 ± 0.87
THGU	M	1	0.49
	L	1	4.31
RSEA	M	9	0.19 ± 0.09
	L	9	2.79 ± 0.52

 

Linear regression equations for metal concentration vs. δ^15N relationships for NOW marine food web using whole vertebrates, Arctic cod and vertebrate muscle data

Object vs. δ^15N	n	Slope	Intercept	R adj^2	p-values
Mn*	94	-0.05	-0.109	0.015	0.042

* No significant trend

 

Bonferroni-corrected multiple correlation coefficients of elements in liver vs. muscle tissue from ringed seals and seabirds

	RSEA	All birds	DOVE	BLKI	BLGU	TMBU	NOFI
n	9	50	10	10	10	10	10
Mn*	0.029	0.462	-0.284	0.804	0.326	0.500	0.415

*Not significantly different

Validity criteria fulfilled:

not applicable

Conclusions:

Under the conditions of the study, Mn showed no relationship with trophic position, as indicated by δ^15N values. Mn was shown to neither biomagnify nor biodilute through the food web.

Executive summary:

Trace elements were measured in ice algae, three species of zooplankton, mixed zooplankton samples, Arctic cod (Boreogadus saida), ringed seals (Phoca hispida) and eight species of seabirds to examine the trophodynamics of metals in an Arctic marine food web. All samples were collected in 1998 in the Northwater Polynya located between Ellesmere Island and Greenland in Baffin Bay.  

Under the conditions of the study, Mn showed no relationship with trophic position, as indicated by δ^15N values. Mn was shown to neither biomagnify nor biodilute through the food web.

Reference 4

Endpoint:

bioaccumulation in aquatic species, other

Remarks:

Fish, crustacean and gastropod samples

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

23 April 2004 - 24 April 2004

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The concentrations of 21 trace elements, including Mn were assessed for the various biota that make up the food web in the main stream of the Mekong Delta near Can Tho, South Vietnam.

GLP compliance:

not specified

Remarks:

Published literature

Details on sampling:

All sampling was conducted in or along the main stream of the Mekong River near Can Tho on 23 and 24 April 2004. Fish, crustacean and gastropod samples were purchased directly from local fishermen operating in the main stream of the Mekong River. Phytoplankton and particulate organic matter (POM) were collected by towing a North Pacific plankton net (NOR-PAC) (0.10 mm in mesh size) horizontally using small boats. In the laboratory, the samples collected by the net were gently transferred to plastic bottles and kept in a refrigerator for two to four hours. The organisms were naturally divided into two layers: A green layer that formed near the surface of the bottle and that was composed of phytoplankton, and a brown one sunk near the bottom of the bottle and was recognised as POM. The phytoplankton, POM and other parts of the water column were clearly distinguishable. Water samples were collected directly from the surface of the Mekong Delta using polyethylene bottles. These samples were kept frozen at -20 °C until dissection and chemical analysis.

Vehicle:

no

Test organisms (species):

other: Various, detailed below.

Details on test organisms:

Crustaceans:
M. rosenbergii, M. equidens, Macrobrachium sp. 3, Macrobrachium sp. 4, M. tenuis.

Fishes:
Clupeodes sp., P. boro, E. melanosoma, P. paradiseus, G. aureus, P. proctozysron, C. armatus, P. wolffi, Cyoglossus sp. 2.

Route of exposure:

aqueous

Justification for method:

other: Not specified

Test type:

field study

Water / sediment media type:

natural water: freshwater

Details on test conditions:

The water samples were filtered (pore size: 0.45 μm) and acidified with HNO3. MilliQ water acidified with HNO3 was used as a control. Whole homogenised biological samples were dried for 12 hrs at 80 °C.
The average moisture contents were found to be 96.2 % in phytoplankton, 74.8 % in POM, 73.5 ± 3.5 % in crustaceans, and 77.0 ± 2.5 % in fish. Concentrations of trace elements were determined using the procedure described previously. About 0.2 g of the sample was digested in 5 mL of concentrated HNO3 in a microwave system for 30 min.

Nominal and measured concentrations:

Concentrations of Mn in water was 3.57 μg/L.

Remarks on result:

not measured/tested

Details on results:

Phytoplankton, POM, five species of crustaceans, and nine species of fish were used for trace element analysis. The concentration of Mn was relatively high in POM. Concentrations of Mn (p < 0.01) were significantly higher in crustaceans than those in fish. Such differences in trace element concentrations between fish and crustaceans might be attributable to differences in the metal accumulation and detoxification abilities such as those conferred by possessing metal-binding proteins.
Mn was not biomagnified or biodiluted through the food chain in the Mekong Delta.

Reported statistics:

One-half of the respective limit of detection was substituted for those values below the limit of detection was used in statistical analyses. When > 50 % of the observations were below the detection limit, further statistical analyses were not conducted. All data were tested for goodness of fit to a normal distribution with a Kolmogorov–Smirnov one-sample test. Because the concentrations of many elements follow a normal distribution, parametric tests were used. Single regression analysis was conducted between the stable isotopes values and trace element concentrations. Analysis of variance (ANOVA) was used to compare the concentrations of trace elements between crustaceans and fish. These analyses were carried out with StatView software (version 5.0, SAS Institute).

Trace element concentration in Mekong Delta water, South Vietnam

Element	Water 1	Water 2
Mn	3.58 μg/L	3.55 μg/L

 

Trace element concentration (mean ± SD μg g^-1 dry wt) in whole organisms of the Mekong Delta, South Vietnam.

Organism	N	Moisture (%)	Mn
Phytoplankton	1	96.2	18.1
POM	1	75.8	436
Crustaceans
M. rosenbergii	5	70.2	54.5 ± 14.3 (37 – 69.1)
M. equidens	7	73.9	47.5 ± 20.5 (8.80 – 68.3)
Macrobrachium sp. 3	2	71.4	96.9 (53.7 – 140)
Macrobrachium sp. 4	3	78.7	30.1 ± 7.7 (22.4 – 37.8)
M. tenuis	1	75.2	17.3
Fishes
Clupeodes sp.	1	81.9	25.6
P. boro	2	74.2	18.6 (17.1 – 19.4)
E. melanosoma	1	75.5	8.76
P. paradiseus	3	79.2	21.8 ± 1.1 (20.5 – 22.5)
G. aureus	5	76.7	24.4 ± 5.6 (18.2 – 33.4)
P. proctozysron	1	74.1	9.59
C. armatus	1	74.3	9.40
P. wolffi	1	76.9	47.9
Cyoglossus sp. 2	1	79.5	40.2

Values in parentheses indicate the range.

 

Statistics for the regression between trace element concentration and δ-^15N values of the crustaceans and fish of the Mekong Delta, South Vietnam

Element	N	Wet Weight Basis				Dry Weight Basis
		Slope	Intercept	r	p-value	Slope	Intercept	r	p-value
Log10 Mn	18	-0.061	1.895	0.363	0.139	-0.044	2.247	0.307	0.215

 

Statistics for the regression between trace element concentration and δ-^15N values of the biota on the Mekong Delta, South Vietnam

Element	N	Wet Weight Basis				Dry Weight Basis
		Slope	Intercept	r	p-value	Slope	Intercept	r	p-value
Log10 Mn	36	-0.048	1.563	0.221	0.196	-0.060*	2.371	0.330	0.049

*Statistically significant

Validity criteria fulfilled:

not applicable

Conclusions:

Concentrations of Mn were higher in crustaceans than fishes. Mn was not biomagnified or biodiluted through the food chain in the Mekong Delta.

Executive summary:

A recent study conducted in the Mekong Delta revealed that concentrations of Mn in the groundwater collected from several locations exceeded World Health Organization (WHO) drinking-water guidelines.  In the present study the concentrations of 21 trace elements were reported, as well as the results of analysis of the various biota that make up the food web in the main stream of the Mekong Delta near Can Tho, South Vietnam.

All sampling was conducted in or along the main stream of the Mekong River near Can Tho (45°10’ N, 141°15’E) on 23 and 24 April 2004.  Fish, crustacean and gastropod samples were purchased directly from local fishermen operating in the main stream of the Mekong River.  Phytoplankton and particulate organic matter (POM) were collected by towing a North Pacific plankton net (NOR-PAC) (0.10 mm in mesh size) horizontally using small boats.  In the laboratory, the samples collected by the net were gently transferred to plastic bottles and kept in a refrigerator for two to four hours.  The organisms were naturally divided into two layers: A green layer that formed near the surface of the bottle and that was composed of phytoplankton, and a brown one sunk near the bottom of the bottle and was recognised as POM.  The phytoplankton, POM and other parts of the water column were clearly distinguishable.  Water samples were collected directly from the surface of the Mekong Delta using polyethylene bottles.  These samples were kept frozen at -20 °C until dissection and chemical analysis.

The water samples were filtered (pore size: 0.45 μm) and acidified with HNO3. MilliQ water acidified with HNO3 was used as a control. Whole homogenised biological samples were dried for 12 hrs at 80 °C. The average moisture contents were found to be 96.2 % in phytoplankton, 74.8 % in POM, 73.5 ± 3.5 % in crustaceans, and 77.0 ± 2.5 % in fish.  Concentrations of trace elements were determined using the procedure described previously. About 0.2 g of the sample was digested in 5 mL of concentrated HNO3 in a microwave system for 30 min. The concentration of Mn was measured with an inductively coupled plasma mass spectrometer (ICP-MS). Yttrium was used as the internal standard. To guarantee the accuracy and precision of the method, standard reference materials DORM2 (National Research Council Canada) were used. Recoveries of trace elements ranged from 86.0 to 116 %. The precision of the method (expressed as coefficient of variation) for replicate samples was better than 10 %.

The study revealed that concentrations of Mn were higher in crustaceans than fishes.  Such differences in trace element concentrations between fish and crustaceans might be attributable to differences in the metal accumulation and detoxification abilities such as those conferred by possessing metal-binding proteins, e.g., metallothioneins (MT), that can bind and sequester toxic and excess heavy metals. Metallothioneins are found in almost all major invertebrate phyla as well as in all vertebrates.

Mn was not biomagnified or biodiluted through the food chain in the Mekong Delta.

Reference 5

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The impact of dietary manganese levels and sources on the growth and mineral composition of post-smolt Atlantic salmon (Salmo salar) fed practical diets was studied.

GLP compliance:

not specified

Remarks:

Published literature

Vehicle:

no

Test organisms (species):

Salmo salar

Details on test organisms:

TEST ORGANISM
- Common name: Atlantic salmon
- Age at study initiation: Post-smolt
- Weight at study initiation: Mean initial weight, 307 ± 25 g

Route of exposure:

feed

Justification for method:

dietary exposure method used for following reason: The impact of dietary manganese (Mn) levels and sources on the growth and mineral composition of post-smolt Atlantic salmon (Salmo salar) fed practical diets was studied.

Test type:

flow-through

Water / sediment media type:

natural water: marine

Total exposure / uptake duration:

8 wk

Total depuration duration:

8 wk

Test temperature:

10 – 12 °C

Salinity:

33 ppt

Details on test conditions:

TEST SYSTEM
- No. of organisms per vessel: Thirty-five fish in each tank.
- No. of vessels per concentration: Triplicate
- Biomass loading rate: Mean initial biomass of 10.75 ± 0.09 kg
- Test diet: The basal diet was intended to closely represent the commercially used feed formulations for seawater Atlantic salmon in Norway. Nevertheless, ingredients were chosen to be as low in Mn as possible and similar to the diet formulation used in a previous study to examine the apparent availability of mineral sources (inorganic, IM or organic, OM) in seawater Atlantic salmon. The basal diet was then formulated to contain no > 15 mg Mn kg^-1 diet.
Five different diets were then prepared from the basal diet with graded inclusion levels of Mn. All the seven diets were isocaloric and isonitrogenous. The analysed Mn concentration in the basal diet was 15 mg kg^-1 diet; the four IM diets (MnSO4 supplemented) were analysed to contain 19, 34, 46 and 79 mg Mn kg^-1 diet; and the two Mn-gly supplemented diets had 20 and 33 mg Mn kg^-1 diet.
- Formulation and composition of the basal experimental diet: 8.3 % whole wheat, 15.0 % corn gluten, 14.4 % hi-pro soya, 20.0 % wheat gluten, 10.0 % soy protein concentrate, 5.0 % fish meal (north Atlantic), 9.9 % fish oil (north Atlantic), 12.3 % rapeseed oil (European, non-GM), 5.4 % micro-ingredients and premixes (contains monoammonium phosphate, histidine HCl, yttrium oxide, l-lysine and DL-methionine and astaxanthin; standard vitamin and mineral mix, excluding manganese.
Proximate composition (analysed, n = 7): 92 ± 0.1 % dry weight, 23.5 ± 0.1 KJ/g energy, 25 ± 0.4 % lipid, 45 ± 0.5 % protein analysed as N * 6.35, 4.5 ± 0.3 % ash, 0.9 ± 0.02 % phosphorous, 0.6 ± 0.02 % calcium.
- The uneaten feed pellets were collected to estimate the actual feed intake.
- The weight and length of the fish were recorded at the start and after 4 and 8 weeks of experimental feeding period after euthanasia by an overdose (6 mL L^-1 ) of tricaine methanesulphonate.
- Justification for choice of test concentrations: To establish the supplementation level, a single standard factorial regression with five graded supplementation levels of Mn was used. Two additional treatments supplemented with chelated Mn-gly in place of MnSO4 at two inclusion levels were also included.

Nominal and measured concentrations:

0, 5, 15, 35, 65 mg Mn kg^-1 diet as manganous sulphate monohydrate (MnSO4.H2O, Mn 32 %) to obtain targeted total nominal levels of 15, 20, 35, 50 or 80 mg Mn kg^-1.
5 or 15 mg Mn kg^-1 diet as Mn-gly (Mn chelate of glycine hydrate, Mn 22 %).

Reference substance (positive control):

no

Details on estimation of bioconcentration:

- Samples for proximate composition and mineral analysis were taken at start and at the end of week 4 and 8. Homogenised pooled samples of whole body (10 fish/tank), liver (6 fish/tank), and vertebrae (6 fish/tank) and individual samples of plasma, bile, liver (aliquot from same 6 fish used for pooled samples above) were collected. Plasma, bile and vertebrae were stored at -20 °C; whereas, the liver samples were flash frozen in liquid nitrogen and further stored at -80 °C until analysis. In addition, at the end of week 8, faeces were collected by stripping from all fish and pooled per tank for apparent availability measurements. Faeces samples were freeze dried for 72 h at -80 °C, homogenised with a pestle and mortar into a fine powder and stored at room temperature until further analysis. The diets were homogenised and analysed for estimating the dry matter, ash, lipid, protein following standard procedures. Briefly, dry matter was measured after drying at 103 °C for 24 h; ash content determined by combustion in a muffle furnace at 550 °C for 16 – 18 h; lipid was determined following ethyl-acetate and acid-extraction in fish tissue and feeds, respectively; protein (6.25 x nitrogen) was measured with a nitrogen analyser according to AOAC official methods of analysis. Haematocrit were measured. The concentration of Mn in diets, faeces and tissues were analysed by inductively coupled plasma mass spectrometry (ICP-MS); and, yttrium in diets and faeces samples were analysed

Remarks on result:

not measured/tested

Remarks on result:

not measured/tested

Remarks on result:

not measured/tested

Remarks on result:

not measured/tested

Details on results:

- Mortality of test organisms: No mortality was observed.
- Observations on body length and weight: Atlantic salmon fed the different experimental diets more than doubled their body weight in the period of 8 weeks with no differential effect of the Mn levels or sources. The mean weight gain of the fish was 320 ± 15 g (mean ± SD); with the highest recorded in OM5 fed fish (336 ± 10 g) and the lowest in fish fed diet with OM15 diet (305 ± 6 g).
- Other biological observations: None of the performance indicators examined were significantly different between the treatments. The mean ± SD across all the groups for specific growth rate, condition factor, percentage feed intake per day, feed efficiency and hepatosomatic index was 1.4 ± 0.03, 1.4 ± 0.02, 1.1 ± 0.03, 1.28 ± 0.03, and 1.16 ± 0.03, respectively.
- Organ specific bioaccumulation: Manganese concentration in all the analysed tissues of fish fed the basal diet after 8 weeks of feeding was significantly lower compared to all other diets (p < 0.05). Vertebrae Mn concentration in Atlantic salmon fed graded Mn inclusion levels followed a curvilinear regression. Also, the fish fed OM5 diet had a significantly higher Mn status in the vertebrae compared to those fed the un-supplemented diet. The Mn concentration in the liver of Atlantic salmon at week 4 was not significantly different between the groups and was not affected by Mn level or source. However, at week 8, a significant linear relation was observed in liver Mn with increasing Mn supplementation. The Mn concentration in the plasma and bile of Atlantic salmon were significantly altered by dietary Mn concentration, both at week 4 (p < 0.05) and week 8 (p < 0.05). Among other micro-minerals, Zn concentration in plasma, liver and vertebrae after 8 weeks of feeding were significantly (p < 0.05) affected by Mn level and source. Plasma Zn increased with increasing Mn supplementation in MnSO4 groups and the highest plasma Zn concentration was observed in fish fed IM65 diets. Among Mn-gly fed fish, OM5 treatment had the highest plasma Zn, which was 40 % higher than corresponding group fed IM5 diet; whereas, it decreased markedly in OM15 groups. The AAC of Zn was significantly higher in basal diet and it was reduced by 5 mg inclusion of MnSO4, but not by Mn-gly. Apart from AAC of Cu, the concentration of Cu in whole body, liver, vertebrae, plasma and faeces were not significantly affected by Mn level or source. Except for fish fed the IM5 diet, the AAC of Cu was significantly reduced by Mn inclusion and was the lowest in OM15.
- The proximate composition of whole body was not influenced by dietary treatments at any stage of the experiment, neither at week 4 nor at week 8. At the end of week 8, dry matter, protein, fat, ash and energy content were not significantly different between the treatments averaging 35 ± 0.1 %, 17 ± 0.1 %, 15 ± 0.1 %, 2 ± 0.1 % and 9.9 ± 0.1 kJ/g, respectively. Similarly, the final whole- body concentration of phosphorus, calcium, magnesium, sodium and potassium were respectively 4.7 ± 0.4, 4 ± 0.7, 0.37 ± 0.2, 0.87 ± 0.3 and 3.9 ± 0.1 g kg^-1 and were also not differentially affected by the Mn levels or sources. Among the micro-minerals, whole body Mn concentration showed significantly different response to dietary treatments at week 8, but not at week 4. At week 8, fish fed the basal diet had the lowest whole-body Mn level (p < 0.001); increasing with level of Mn inclusion, and then reached a plateau. Difference in Mn source (MnSO4 vs Mn-Gly) did not have a differential impact on the whole-body Mn concentration. Whole body concentration (mg kg^-1 fresh weight) of other essential micro-minerals namely Cu, Fe, Zn and Se were 1.8 ± 0.1, 9.6 ± 0.3, 26.8 ± 1.4 and 0.16 ± 0.005, respectively and were similar between the treatments.
- Faecal manganese loss, apparent availability coefficient and retention: The Mn concentration in the faeces, apparent availability and retention were all influenced by dietary treatments. Faecal Mn concentration increased linearly with increasing Mn supplementation irrespective of the Mn source (p < 0.0001). Zn concentration in the faeces was significantly higher in IM5 fed fish compared to other IM supplemented groups (p < 0.05, Kruskal-Wallis non-parametric test). The AAC of Mn followed a non-linear response and was significantly higher in MnSO4 supplemented diets (p < 0.05). Retention of dietary Mn was significantly higher in Atlantic salmon fed with diets IM5 and OM5, irrespective of the source (p < 0.0001).
- Estimation of dietary manganese inclusion level: Whole body, vertebral, plasma Mn concentrations and AAC were used as response criteria. Modelling of data from MnSO4 supplemented groups showed that, Mn saturation of whole body, vertebrae, plasma and apparent availability occurred at dietary Mn inclusion level of 16.3 mg Mn kg^-1 diet (total 29.5 ± 5.3 mg kg^-1 diet), 22.1 mg kg^-1 diet (total, 26.2 ± 2.7 mg kg^-1 diet), 14.1 mg Mn kg^-1 (total, 26.3 ± 4.9 mg kg^-1 diet) and 17.8 mg Mn kg^-1 diet (total, 34 ± 3.4 mg kg^-1 diet), respectively. Parameter estimates (requirement and plateau) obtained through the non-linear regression from graded inclusion of MnSO4 were used to calculate the relative bioavailability index of Mn-gly. The relative bioavailability index of Mn-gly was 2.6 to 4.5-fold higher compared to MnSO4 to reach saturation levels of Mn in plasma, whole body and vertebrae. Overall, required Mn supplementation level (as MnSO4) for Atlantic salmon in seawater fed low fish meal, plant-based diets range from 14.1 to 22.1 mg kg^-1; the corresponding supplementation levels for Mn-gly as the Mn source range from 4.9 to 5.7 mg kg^-1 diet.

Reported statistics:

The determination of the required level of Mn inclusion, three non-linear regression models namely (i) BL1, broken-line with plateau (Robbins et al., 2006); (ii) BL2, broken-line with two lines (Robbins et al., 2006); and (iii) QP, quadratic plateau (Simongiovanni et al., 2012) were applied to the data from five dietary groups (basal diet and four graded inclusion of Mn as MnSO4), and the best-fit model was selected based on R2 value. Apparent availability coefficient (AAC) and retention were calculated according to the formulae described in Antony Jesu Prabhu et al. (2014). The relative bioavailability index of Mn-gly compared to MnSO4 was calculated considering the percentage saturation in specific response criteria achieved with 5 mg Mn supplementation kg^-1 diet as Mn-gly, adapted from Antony Jesu Prabhu et al. (2018).
The data are presented as mean and pooled standard deviation, using tanks as the experimental units for all parameters analysed (n = 3). One-way ANOVA at significance level of 0.05, followed by Tukey's multiple comparison analysis was used to determine the effect of dietary treatments. In the case of non-normal distribution of data, Kruskal-Wallis non-parametric test was used. Area under the curve analysis was used to identify the peaks in bile and plasma Mn concentrations. All the data analysis was performed using GraphPad Prism version 8.0 for Windows, GraphPad Software, California USA.

Growth Performance of Atlantic Salmon Fed Different Dietary Levels and Sources of Mn for 8 Weeks in Seawater.

Mn Source	Mn Inclusion Level (mg kg^-1)	Bodyweight (g)		Weight Gain (g)		Specific Growth Rate (% Day ^-1)
		Week 4	Week 8	Week 4	Week 8	Week 4	Week 8
Basal diet	0	454.2	633.4	148.4	327.6	1.62	1.42
	5	451.7	620.8	145.7	314.8	1.59	1.38
	15	450.8	621.5	143.7	314.5	1.57	1.37
	35	456.5	624.6	147.1	315.8	1.62	1.38
	65	454.6	633.7	147.2	326.3	1.62	1.42
Mn-gly	5	454.5	643.8	147.1	336.5	1.62	1.45
	15	443.8	611.7	137.2	305.0	1.53	1.35
Pooled SD		6.9	16.2	5.9	15.3	0.07	0.03
p-value		ns	ns	ns	ns	ns	ns

Treatment effects were considered significant when p < 0.05 upon ANOVA followed by Tukey’s multiple comparison post-hoc analysis.

ns: Treatment effects not statistically significant, p > 0.05.

Mean initial weight of fish was 307 ±26 g.

 

Whole Body and Tissue Manganese Concentration of Atlantic Salmon Fed Different Dietary Levels and Sources of Mn for 8 Weeks in Seawater.

Mn Source	Mn Inclusion Level (mg kg^-1)	Whole Body		Vertebrae		Liver
		Week 4	Week 8	Week 4	Week 8	Week 4	Week 8
Basal diet	0	1.3	1.0 (a)	10.1	9.5 (a)	1.4	1.4 (a)
	5	1.1	1.3 (a, b)	11.0	11.7 (a, b)	1.5	1.5 (a)
	15	1.4	1.7 (b)	11.7	12.7 (b)	1.5	1.5 (a)
	35	1.6	1.5 (a, b)	12.3	13.3 (b)	1.6	1.6 (b)
	65	1.5	1.8 (b)	12.0	13.7 (b)	1.6	1.7 (b)
Mn-gly	5	1.6	1.5 (a, b)	13.7	13.7 (b)	1.7	1.5 (a)
	15	1.0	1.7	12.7	12.7 (b)	1.6	1.5 (a)
Pooled SD		0.32	0.18	1.6	0.7	0.09	0.05
p-value		ns	0.004	ns	0.0004	ns	0.001

All data presented as mg per kg wet weight. Treatments effects were considered significant when p < 0.05 upon ANOVA followed by Tukey's multiple comparison post-hoc analysis. Different letters within a column indicate statistically significant difference between the groups.

ns: Treatment effects not significant, p > 0.05.

 

 

Haematocrit (Hct), Plasma and Bile Mn Concentration of Atlantic Salmon Fed Different Dietary Levels and Sources of Mn for 8 Weeks in Seawater.

Mn Source	Mn Inclusion Level (mg kg^-1)	Hct	Plasma		Bile		Plasma: Bile
		Week 8	Week 4	Week 8	Week 4	Week 8	Week 4	Week 8
Basal diet	0	40.1	1.1	1.4 (a)	0.47 (a)	0.37 (a)	2.5	3.8
	5	45.4	1.3	2.3 (b)	0.47 (a)	0.47 (a)	3.0	5.0
	15	40.2	2.1	3.2 (c)	0.52 (a)	0.59 (a, b)	4.0	5.0
	35	41.4	1.8	2.8 (b, c)	0.74 (b)	0.79 (b)	2.5	3.7
	65	40.5	1.7	3.0 (c)	0.58 (a)	0.55 (a, b)	2.9	5.5
Mn-gly	5	40.6	2.1	3.0 (c)	0.85 (b)	0.55 (a, b)	2.4	5.3
	15	42.5	1.6	2.3 (b)	0.53 (a)	0.55 (a, b)	3.1	4.3
Pooled SD		2.7	0.3	0.5	0.08	0.09	0.4	0.9
p-value		ns	0.02	0.02	0.001	0.01	ns	ns

Hct presented as %; plasma and bile Mn concentrations presented as μmol L^-1.

Treatments effects were considered significant when p < 0.05 upon ANOVA followed by Tukey's multiple comparison post-hoc analysis. Different letters within a column indicate statistically significant difference between the groups.

ns: Treatment effects not significant, p > 0.05.

 

Faecal Loss, Apparent Availability Coefficient (AAC) and Retention of Mn from Atlantic Salmon Fed Different Dietary Levels and Sources of Mn for 8 Weeks in Seawater.

Mn Source	Mn Inclusion Level (mg kg^-1)	Faeces Mn (mg kg^-1 Wet Weight)	AAC (%)	Retention (% Total Intake)
Basal diet	0	5.4 (a)	26.2 (c)	6.4 (a)
	5	8.3 (b)	29.1 (d)	10.8 (c)
	15	10.3 (b)	43.5 (f)	9.6 (b)
	35	18.7 (c)	37.9 (e)	5.7 (a)
	65	33.0 (d)	23.5 (c)	5.2 (a)
Mn-gly	5	9.3 (b)	17.7 (b)	12.5 (c)
	15	21.7 (c)	-17.3 (a)	9.0 (b)
Pooled SD		0.6	2.2	1.9
p-value		< 0.0001	< 0.0001	0.0009

Treatments effects were considered significant when p < 0.05 upon ANOVA followed by Tukey's multiple comparison post-hoc analysis. Different letters within a column indicate statistically significant difference between the groups.

ns: Treatment effects not significant, p > 0.05.

 

Relative Bioavailability Index of Mn-Glycine over MnSO4 to Meet the Mn Requirement of Atlantic Salmon in Seawater Fed Low Fish Meal, Plant-Based Ingredient Diets

Criteria	A. Saturation Level Reached (mg kg^-1 Wet Weight, or μM)	B. Mn (as MnSO4) Required to REACH Saturation (mg kg^-1 Diet)	C. Response Level Reached with 5 mg Mn mg^-1 Mn-Gly (mg kg^-1 Wet Weight or μM)	D. Percentage Saturation with 5 mg Mn kg-1 Mn-Gly	E. Relative Bioavailability Index	F. Estimated Inclusion of Mn-Gly to Meet Requirement
Whole body Mn	1.7	16.3	1.5 ns	88.2	2.9	5.7
Plasma Mn	3.02	14.1	2.8 ns	92.7	2.6	5.4
Vertebrae Mn	13.4	22.1	13.7 ns	102.2	4.5	4.9

A: Saturation level reached: Mean value of parameter L (plateau) from the non-linear regression model.

B: Mn (as MnSO4) required to reach saturation: Mean value of parameter R from the non-linear regression model.

C: Response level reached with 5 mg Mn kg^-1 Mn: gly: Mean value of data presented for 5 mg Mn kg^-1 Mn-gly group. Ns denotes the lack of significant difference between C and A.

D: Percentage saturation with 5 mg mN kg^-1 Mn-gly: Calculated as (C / A) * 100.

E: Relative bioavailability inex: Calculated as (B / 5) * (C / A).

F: Estimated inclusion of Mn-gly to meet requirement: Calculated as B / E.

Validity criteria fulfilled:

not applicable

Conclusions:

Under the conditions of the study, plasma and bile Mn concentrations were significantly affected by dietary treatments at both sampling points, at week 4 and 8; whereas, whole body, liver and vertebrae responded significantly only at the end of 8 weeks. Dietary Mn level needed to meet the requirement of post-smolt Atlantic salmon was estimated by non-linear regression models using saturation of whole body or tissue Mn status asresponse criteria. The estimates based on Mn concentration in whole body, vertebrae, plasma and apparentavailability were 29.5 ± 5.3, 26.2 ± 2.7, 26.3 ± 4.9 and 34 ± 3.4 mg Mn kg^-1 diet, respectively. Analysis of relative bioavailability index showed that low inclusion of Mn-gly (5 mg kg^-1 supplementation) was 2.6 to 4.5-fold more efficient than MnSO4 to attain whole body or tissue Mn saturation levels.

Executive summary:

The impact of dietary manganese (Mn) levels and sources on the growth and mineral composition of post-smolt Atlantic salmon (Salmo salar) fed practical diets was studied. Seven experimental diets were prepared with graded supplementation level of Mn; basal diet had a Mn concentration of 15 mg kg^−1 , four diets with 5, 15, 35 and 65 mg kg^−1 supplementation of Mn as MnSO4 and two diets with at 5 and 15 mg kg^−1 supplementation of Mn as Mn-glycine (Mn-gly). Atlantic salmon (initial weight, 307 ± 25 g) were distributed to 21 tanks (35 fish/ tank). These fish were randomly fed with one of the experimental diets, in triplicate groups to apparent satiation for 8 weeks. At week 4 and 8, samples of whole body, plasma, bile, liver and vertebrae were collected, and their mineral concentration determined. At week 8, faeces were collected by stripping for measuring apparent availability coefficient (AAC).

Neither the Mn inclusion level, nor the source had a significant impact on growth and other performance indicators. Plasma and bile Mn concentrations were significantly affected by dietary treatments at both sampling points, at week 4 and 8; whereas whole body, liver and vertebrae responded significantly only at the end of 8 weeks. Dietary Mn level needed to meet the requirement of post-smolt Atlantic salmon was estimated by non-linear regression models using saturation of whole body or tissue Mn status as response criteria. The estimates based on Mn concentration in whole body, vertebrae, plasma and apparent availability were 29.5 ± 5.3, 26.2 ± 2.7, 26.3 ± 4.9 and 34 ± 3.4 mg Mn kg^-1 diet, respectively. Analysis of relative bioavailability index showed that low inclusion of Mn-gly (5 mg kg^-1 supplementation) was 2.6 to 4.5-fold more efficient than MnSO4 to attain whole body or tissue Mn saturation levels. On the contrary, high inclusion of Mn-gly (15 mg kg^-1 supplementation) reduced the AAC of Mn, zinc (Zn) and copper (Cu), along with lower Mn and Zn status in tissues. The mean estimate of dietary Mn required to maintain tissue Mn saturation ranged between 26 and 34 mg Mn kg^-1 diet; the corresponding Mn supplementation (as MnSO4) ranged from 14 to 22 mg Mn kg^-1 diet. The supplementation level can be reduced to 4.9 to 5.7 mg Mn kg^-1 diet by using Mn-gly as Mn source without compromising growth or Mn status of Atlantic salmon. High inclusion levels of Mn-gly (15 mg kg^-1 diet) was found to be not beneficial.

Reference 6

Endpoint:

bioaccumulation in aquatic species: fish

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Description of key information

In accordance with section 1 of REACH Annex XI (testing does not appear scientifically necessary), the bioaccumulation study (required in section 9.3.2.) does not need to be conducted.

Other information is already available to determine the bioaccumulation potential of soluble manganese salts ( worse-case and) and manganese metal, specifically  discussed below.

Two reports (as attached to the dataset) provide comprehensive information on the behaviour of several inorganic manganese substances including the registered substance in the environment;

Manganese and its compounds, environmental aspects, WHO, 2004

Proposed EQS for Water Framework Directive Annex VIII substances: manganese (total dissolved), UK Environment Agency, 2007

Manganese is a naturally occurring essential metal element found widely in rock, soil, water and food. Generally aquatic biota regulate actively their internal concentrations of metals by active transport, storage or a combination of both. As a result of these processes which do often not discriminate non-essential metals, an inverse relationship gets established between water concentrations and the corresponding accumulation factors (e.g. BCF, BAF) of most metals. This means that organisms accumulate metals unspecifically to meet their metabolic requirements, whereat non-essential metals are moderately accumulated as well.

The WHO and UK Environment Agency reports determined that manganese (in 2+ and 4+ are the most relevant valencies in the environment of which the registered substance exhibites a valency of 0) can be significantly bioaccumulated in aquatic systems, especially by lower trophic levels, but less so in fish. 

Both the WHO and the UK Environment Agency cite the following BCF values:

• Marine and freshwater plants BCF: 2 000 - 20 000 (Folsom et al., 1963)


• Phytoplankton BCF: 2 500 - 6 300 (Thompson et al., 1972)


• Marine macroalgae BCF: 300 - 5 500 (Bryan & Hummerstone, 1973)


• Intertidal mussels BCF: 800 - 830 (Pentreath, 1973)


• Fish BCF: 35 - 930 (Rai & Chandra, 1992)

Marine fish do not accumulate manganese to the same extent as organisms at lower trophic levels, with typical BCFs of about 100 (Ichikawa, 1961).  Uptake of manganese by aquatic invertebrates and fish significantly increases with temperature (Miller et al., 1980) and increases with decreasing salinity (Struck et al., 1997).  Uptake of Mn also decreases with pH (Rouleau et al., 1996), while dissolved oxygen has no significant effect (Miller et al., 1980); Baden et al., 1995). Despite the potential to bioaccumulate, biomagnification does not appear to occur to a significant extent.  No biomagnification was found in a freshwater food-chain, with maximum BCFs of 911, 65, and 23 for algae, Daphnia magna, and fathead minnows (Pimephales promelas), respectively (Kwasnik et al. (1978). Weak biomagnification was found in some systems (Stokes et al., 1988), but not in Pelagic Arctic marine food web species (Campbell, 2005).

Prabhu et al. (2019 shows clearly that there is no bioaccumulation from dietary manganese.

Speciation of manganese can be affected by variable such as pH and water hardness, and yield forms which are more, or less, bioavailable from the water column.  It should be noted that values refer to soluble bioavailable manganese forms rather than the pure elemental Mn, which is poorly soluble.  A water solubility study determined that at 20 °C the water solubility of Mn metal was 0.7 mg/L.  In comparison, the water solubility of the soluble Mn salts, MnCl2 and MnSO4 799.0 mg/L and 450 mg/L respectively.  A transformation/dissolution study on Mn metal massive determined that 4.6 μg/g and 11.5 μg/g was released at 7 and 28 days respectively (Brouwers, 2017).  The study showed that the test material had no immediate influence on the pH of the test system.  As such the BCF values above would be considered to be worst case values for soluble manganese substances and that the relatively insoluble Mn metal would have BCF factors very much lower, hence of no concern especially if the background level of this naturally occurring element is taken into consideration with only the added contribution considered for effects evaluation as discussed in the aforementioned WHO and UKEQS report

Manganese is an essential element and nutrient for animals and is required for the photosynthetic process in plants.  As such it is subject to homeostatic mechanisms which means that bioaccumulation factors are independent of exposure concentrations.

The manganese uptake requirement may be different not only across different species, but also be influenced by life-stage and metabolic differences due to seasonal variations which result in different Mn requirements.  Furthermore, where environmental levels of Mn are low, or the organism’s requirement higher than the environmental concentrations, active regulation may result in higher BCFs for essential elements.  The poor applicability of BCFs for metals, particularly for essential metals, is recognized in the regulatory framework of aquatic hazard classification (OECD Series on testing and assessment No. 27, 2001).  The degree of bioconcentration depends not only the intrinsic properties of the substance, but also on factors such as the degree of bioavailability, the physiology of the test organism, maintenance of constant exposure concentration, exposure duration, metabolism inside the body of the target organism and excretion from the body (OECD Series on testing and assessment No. 27, 2001).

Overall, the bioaccumulation study on manganese metal is waived on the basis that considerable existing data is already available which establishes the following points:

1) Manganese is an essential element and nutrient for animals and as such is regulated by organisms depending on their biological burden and requirement.

2) Bioaccumulation testing is poorly applicable to essential metals because of the homeostatic regulation of essential metals.

3) Existing data demonstrates that whilst manganese (in valencies not relevant to elemental Mn) can bioaccumulate, at lower trophic levels biomagnification up the food chain is weak or does not occur.

4) Whilst there is a significant volume of published literature on the bioaccumulation of manganese that may be used to determine the bioconcentration and bioaccumulation factors these data are largely based on soluble manganese salts, as opposed to the registered substance manganese metal. Manganese metal itself is very poorly soluble with low bioavailability, as shown in the transformation dissolution data included in this dataset. Data on the more soluble salts commonly referenced in existing literature are likely to over-estimate the bioaccumulation potential of manganese metal itself.

Additional supporting data is included as robust study summaries; namely papers by Prabhu (2019, Simonetti (2018), Ikemoto (2008a) and Campbell (2005).

Further references:

Howe PD, Malcolm HM, Dobson S MANGANESE AND ITS COMPOUNDS: ENVIRONMENTAL ASPECTS. Concise International Chemical Assessment Document 63, WHO 2004.

OECD SERIES ON TESTING AND ASSESSMENT Number 27 GUIDANCE DOCUMENT ON THE USE OF THE HARMONISED SYSTEM FOR THE CLASSIFICATION OF CHEMICALS WHICH ARE HAZARDOUS FOR THE AQUATIC ENVIRONMENT. ENVIRONMENT DIRECTORATE JOINT MEETING OF THE CHEMICALS COMMITTEE AND THE WORKING PARTY ON CHEMICALS, PESTICIDES AND BIOTECHNOLOGY. ENV/JM/MONO(2001)8. 23-Jul-2001

Crane M, Sorokin N, Atkinson C, and Maycock D. Water Framework Directive - United Kingdom Technical Advisory Group (WFD-UKTAG) (2007) Proposed EQS for Water Framework Directive Annex VIII substances: manganese (total dissolved). Report No. SC040038/SR10

Ando T, Yamamoto M, Tomiyasu T, Hashimoto J, Miura T, Nakano A, Akiba S (2002) Bioaccumulation of mercury in a vestimentiferan worm living in Kagoshima Bay, Japan. Chemosphere, 49:477–484.

Bryan GW, Hummerstone LG (1973) Brown seaweed as an indicator of heavy metals in estuaries in south-west England. Journal of the Marine Biological Association of the U.K., 53:705– 720.

Folsom TR, Young DR, Johnson JN, Pillai KC (1963) Manga nese-54 and zinc-65 in coastal organisms of California. Nature , 200:327–329

Pentreath RJ (1973) The accumulation from water of 65Zn, 54Mn, 58Co, and 59Fe by the mussel, Mytilus edulis. Journal of the Marine Biological Association of the U.K., 53:127–143.

Rai UN, Chandra P (1992) Accumulation of copper, lead, manganese and iron by field populations of Hydrodictyon reticulatum (Linn.) Lagerheim. Science of the Total Environment, 116(3):203–211.

Thompson SE, Burton CA, Quinn DJ, Ng YC (1972) Concen - tration factors of chemical elements in edible aquatic organisms. Livermore, CA, University of California, Lawrence Livermore Laboratory, Bio-Medical Division.

Ichikawa R (1961) On the concentration factors of some impor tant radionuclides in marine food organisms. Bulletin of the Japanese Society of Scientific Fisheries, 27:66–74.

Miller DW, Vetter RJ, Atchinson GJ (1980) Effect of temperature and dissolved oxygen on uptake and retention of 54Mn in fish. Health Physics, 38(2):221–225.

Rouleau C, Tjälve H, Gottofrey J (1996) Effects of low pH on the uptake and distribution of 54Mn(II) in brown trout (Salmo trutta). Environmental Toxicology and Chemistry, 15(5):708–710

Struck BD, Pelzer R, Ostapczuk P, Emons H, Mohl C (1997) Statistical evaluation of ecosystem properties influencing the uptake of As, Cd, Co, Cu, Hg, Mn, Ni, Pb and Zn in seaweed (Fucus vesiculosus) and common mussel (Mytilus edulis). Science of the Total Environment, 207:29–42.

Baden SP, Eriksson SP, Weeks JM (1995) Uptake, accumulation and regulation of manganese during experimental hypoxia and normoxia by the decapod Nephrops norvegicus (L.). Marine Pollution Bulletin, 31(1–3):93–102

Kwasnik GM, Vetter RJ, Atchison GJ (1978) The uptake of manganese-54 by green algae (Protococcoidal chlorella), Daphnia magna, and fathead minnows (Pimephales promelas). Hydrobiologia, 59:181–185

Stokes PM, Campbell PGC, Schroeder WH, Trick C, France RL, Puckett KJ, LaZerte B, Speyer M, Hanna JE, Donaldson J (1988) Manganese in the Canadian environment. Ottawa, Ontario, National Research Council of Canada, Associate Committee on Scientific Criteria for Environmental Quality (NRCC No. 26193).

Additional information

Prabhu et al. (2019)

The impact of dietary manganese (Mn) levels and sources on the growth and mineral composition of post-smolt Atlantic salmon (Salmo salar) fed practical diets was studied. The study was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997).

Seven experimental diets were prepared with graded supplementation level of Mn; basal diet had a Mn concentration of 15 mg kg^−1 , four diets with 5, 15, 35 and 65 mg kg^−1 supplementation of Mn as MnSO4 and two diets with at 5 and 15 mg kg^−1 supplementation of Mn as Mn-glycine (Mn-gly). Atlantic salmon (initial weight, 307 ± 25 g) were distributed to 21 tanks (35 fish/ tank). These fish were randomly fed with one of the experimental diets, in triplicate groups to apparent satiation for 8 weeks. At week 4 and 8, samples of whole body, plasma, bile, liver and vertebrae were collected, and their mineral concentration determined. At week 8, faeces were collected by stripping for measuring apparent availability coefficient (AAC).

Neither the Mn inclusion level, nor the source had a significant impact on growth and other performance indicators. Plasma and bile Mn concentrations were significantly affected by dietary treatments at both sampling points, at week 4 and 8; whereas whole body, liver and vertebrae responded significantly only at the end of 8 weeks. Dietary Mn level needed to meet the requirement of post-smolt Atlantic salmon was estimated by non-linear regression models using saturation of whole body or tissue Mn status as response criteria. The estimates based on Mn concentration in whole body, vertebrae, plasma and apparent availability were 29.5 ± 5.3, 26.2 ± 2.7, 26.3 ± 4.9 and 34 ± 3.4 mg Mn kg^-1 diet, respectively. Analysis of relative bioavailability index showed that low inclusion of Mn-gly (5 mg kg^-1 supplementation) was 2.6 to 4.5-fold more efficient than MnSO4 to attain whole body or tissue Mn saturation levels. On the contrary, high inclusion of Mn-gly (15 mg kg^-1 supplementation) reduced the AAC of Mn, zinc (Zn) and copper (Cu), along with lower Mn and Zn status in tissues. The mean estimate of dietary Mn required to maintain tissue Mn saturation ranged between 26 and 34 mg Mn kg^-1 diet; the corresponding Mn supplementation (as MnSO4) ranged from 14 to 22 mg Mn kg^-1 diet. The supplementation level can be reduced to 4.9 to 5.7 mg Mn kg^-1 diet by using Mn-gly as Mn source without compromising growth or Mn status of Atlantic salmon. High inclusion levels of Mn-gly (15 mg kg^-1 diet) was found to be not beneficial.

 

Ikemoto et al. (2008)

A recent study conducted in the Mekong Delta revealed that concentrations of Mn in the groundwater collected from several locations exceeded World Health Organization (WHO) drinking-water guidelines.  In the present study the concentrations of 21 trace elements were reported, as well as the results of analysis of the various biota that make up the food web in the main stream of the Mekong Delta near Can Tho, South Vietnam.  The study was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997).

All sampling was conducted in or along the main stream of the Mekong River near Can Tho (45°10’ N, 141°15’E) on 23 and 24 April 2004.  Fish, crustacean and gastropod samples were purchased directly from local fishermen operating in the main stream of the Mekong River.  Phytoplankton and particulate organic matter (POM) were collected by towing a North Pacific plankton net (NOR-PAC) (0.10 mm in mesh size) horizontally using small boats.  In the laboratory, the samples collected by the net were gently transferred to plastic bottles and kept in a refrigerator for two to four hours.  The organisms were naturally divided into two layers: A green layer that formed near the surface of the bottle and that was composed of phytoplankton, and a brown one sunk near the bottom of the bottle and was recognised as POM.  The phytoplankton, POM and other parts of the water column were clearly distinguishable.  Water samples were collected directly from the surface of the Mekong Delta using polyethylene bottles.  These samples were kept frozen at -20 °C until dissection and chemical analysis.

The water samples were filtered (pore size: 0.45 μm) and acidified with HNO3. MilliQ water acidified with HNO3 was used as a control. Whole homogenised biological samples were dried for 12 hrs at 80 °C. The average moisture contents were found to be 96.2 % in phytoplankton, 74.8 % in POM, 73.5 ± 3.5 % in crustaceans, and 77.0 ± 2.5 % in fish.  Concentrations of trace elements were determined using the procedure described previously. About 0.2 g of the sample was digested in 5 mL of concentrated HNO3 in a microwave system for 30 min. The concentration of Mn was measured with an inductively coupled plasma mass spectrometer (ICP-MS). Yttrium was used as the internal standard. To guarantee the accuracy and precision of the method, standard reference materials DORM2 (National Research Council Canada) were used. Recoveries of trace elements ranged from 86.0 to 116 %. The precision of the method (expressed as coefficient of variation) for replicate samples was better than 10 %.

The study revealed that concentrations of Mn were higher in crustaceans than fishes.  Such differences in trace element concentrations between fish and crustaceans might be attributable to differences in the metal accumulation and detoxification abilities such as those conferred by possessing metal-binding proteins, e.g., metallothioneins (MT), that can bind and sequester toxic and excess heavy metals. Metallothioneins are found in almost all major invertebrate phyla as well as in all vertebrates.

Mn was not biomagnified or biodiluted through the food chain in the Mekong Delta.

 

Simonetti et al. (2018)

In order to determine the metal-accumulating ability of the burrowing crab, Neohelice granulata, in the intertidal areas of the Bahía Blanca estuary, concentrations of Mn in soft tissues of adult specimens were measured. Subsequently, the bioconcentration factor (BCF) was determined using levels of concentrations previously obtained in intertidal sediments. The results showed concentrations above the detection limit in soft tissues of male and female crabs.  The study was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997).

The availability of metals to be bioaccumulated is dependent upon the concentration of the element within the sediment as well as its geochemical behaviour and physical-chemical conditions within that matrix. For crustaceans, several intrinsic factors, for instance age, size, stage in the molt cycle and reproductive cycle, may influence bioaccumulation process.

Differences between sites and/or sexes were analysed by two-way ANOVA.  Significant differences between the sites were found for Mn, with concentrations significantly greater in crabs from Rosales Port (Mn: 64.20 ± 16.93 μg/g dw vs 47.51 ± 16.69 μg/g dw, p = 0.002).  In this study, significant differences between sexes were found for Mn in both sites (p < 0.003), being superior in males than females in all cases.

Under the conditions of the study the BCF for Mn in the burrowing crab, Neohelice granulata, was < 1.

 

Campbell et al. (2005)

Trace elements were measured in ice algae, three species of zooplankton, mixed zooplankton samples, Arctic cod (Boreogadus saida), ringed seals (Phoca hispida) and eight species of seabirds to examine the trophodynamics of metals in an Arctic marine food web. All samples were collected in 1998 in the Northwater Polynya (NOW) located between Ellesmere Island and Greenland in Baffin Bay.  The study was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997).

Under the conditions of the study, Mn showed no relationship with trophic position, as indicated by δ^15N values.  Mn was shown to neither biomagnify nor biodilute through the food web.