Assessment of Metal Accumulation and Bioaccumulation Factor of Some Trace and Heavy Metals in Freshwater Prawn and Crab

*Osikemekha Anthony Anani and John Ovie Olomukoro*

#### **Abstract**

Globally, freshwater decapods have been one of the major food delicacies because of their rich deposits of minerals. High metals are usually accumulated in the body tissues of these organisms because of their lifestyle. Metal accumulation in freshwater decapods has been acclaimed and perceived to cause serious health concerns when transferred to humans along the food chain. A recent study has shown that freshwater biota, prawn (*Macrobrachium rosenbergii*), showed significant differences (p < 0.05) in Mn, Cu, Pb and Cr and no significant difference (p > 0.05) in Fe, Zn and Cd. In contrast, the freshwater biota, crab (*Sudanonautes africanus*), showed significant differences (p < 0.05) in Fe, Zn and Mn and no significant differences (p > 0.05) in Pb, Cr and Cd. A high accumulation of Fe in the whole tissues of *Macrobrachium rosenbergii* and *Sudanonautes africanus* was also established. This is because Fe in the Nigerian soil and sediment is naturally very high beyond slated thresholds and tend to accumulate and transcend or magnify in benthic. It was noticed that Zn (2.68) and Cr (4.52) had the highest bioaccumulation factors in prawn and crab, respectively. Chromium has been observed to be carcinogenic. The consumption of Cr in the muscles of crab might constitute probable serious health risk.

**Keywords:** accumulation, biomagnification, decapods, risk, carcinogenicity

#### **1. Introduction**

Globally, freshwater decapods have been one of the major food delicacies because of their rich deposits of minerals, metals; calcium (Ca), iron (Fe), zinc (Zn) and copper (Cu), Nickel (Ni), Vanadium (V) and Cadmium (Cd) as well as nutrients; protein, fibers and cellulose. High levels of mineral contents like metals are usually accumulated in the body tissues of these organisms because of their lifestyle. This has necessitated the increased rate of human consumption in recent times [1].

It has been documented that freshwater crab (*Sudanonautes africanus*) and prawn (*Macrobrachium rosenbergii*) have high deposits of Fe, Zn and Mn, with few traces of Cu, Pb, Cr, Cd, Ni and V [1–4].

Metal accumulation in freshwater decapods has been acclaimed and perceived to cause serious health concerns when transferred to humans along the food chain. Environmental valuation of the noxiousness of metals in the freshwater *Sudanonautes africanus* and *Macrobrachium rosenbergii* had been shown to have probable human health hazard effect concomitant by way of ingestion [1].

Health risks associated with heavy metals such as renal failure, skeletal deformation, and hepatic failure have been linked to their non-decomposable and persistence nature in the visceral organ-parts of humans [5]. This can lead to severe maladies like dysentery, stomach aches, head-tremor, anemia, paralysis, nausea, paroxysm, melancholy and even respiratory disorders [6], which can be either acute or chronic forms; neuron toxicity, oncogenic, genetic alteration or teratogenicity [7].

High levels of bio-accumulated heavy metals in freshwater decapods have been identified in these ranks; Fe > Zn > Mn > Cu > Pb > Cr [1] as interconnected with their sediment background levels [8].

#### **2. Methodology**

#### **2.1 Sampling technique**

Samples of freshwater prawns and crabs (*Macrobrachium rosenbergii* and *Sudanonautes africanus*) were captured and collected monthly from March 2015 to August 2016 at designated stations by some fishermen, using local-hand nets enticed with ox-heart, set at the river bank of each station 24 hours before capturing. The prawns and crabs were collected and kept in different labeled plastic rubbers according to the stations, filled with the river water and immediately taken to the laboratory for heavy metal analysis and identifications.

#### **2.2 Extraction and determination of heavy metals in freshwater decapods**

Employing the methods of [1], the freshwater biota was oven dried at 105°C. About 2 g of a dried up standardized sample of each tissue were digested and sample was made up to about 50 ml of purified water. Samples of the biota were analyzed for iron, manganese, zinc, copper, chromium, cadmium, nickel, lead, and vanadium with an AAS (atomic absorption spectrophotometer; SOLAAR 969AA UNICAM, Spectronic Unicam, Cambridge, UK) [1].

#### **2.3 Data analysis**

Simple descriptive analysis, ANOVA (Analysis of variance), was employed using SPSS version 20.0.

To determine the accumulation rate of heavy metals in the freshwater biota, the bio-indices; bioaccumulation factor was employed with Micro Excel version 2013. Bioaccumulation factor (BAF) is the concentration of metals in sediment or water over the concentration of metals in the biota in mg kg<sup>−</sup><sup>1</sup> [8]. This can be represented in the equation below:

concentration of metals in the photo in mg kg ${}^{-}$  [8]. I his can be represented activation below:

$$\textbf{BAF} = \frac{\textbf{concentration of metals in sediment/water (mg/kg)}}{\textbf{concentration of metals in Carbon (mg/kg)}} \tag{1}$$

**157**

*Assessment of Metal Accumulation and Bioaccumulation Factor of Some Trace and Heavy…*

The assessment of metal contents in freshwater decapods is suitable for both water and terrestrial life forms. This is based on their significance as water indicators of pollutants via monitoring in spatial or temporal, in order to quantify their ecological role in the ecosystem. Even though the dangers of water pollution by metals are fully acknowledged, it is still a subject of discussing in line with the over increasing anthropogenic activities [9] and as well as the lithogenic activities [1]. Freshwater prawn and shrimp (Macroinvertebrates) are commonly recommended as fauna-indicators for evaluating the fluctuation of aquatic disorders in the region of probable pollution [3]. In general, decapods are of certain prominence for bio-monitoring survey [10], as the bedrock species in most aquatic systems [11], as well as the most tolerated species against water pollution. This shows their pollution status as regards to the buildup of the corresponding components of metals in

**3.1 Accumulation of metals in** *Sudanonautes africanus* **and** *Macrobrachium* 

Metal contamination in freshwater ecosystem is of utmost worry everywhere in the biosphere [13–15]. This might be as a result of their persistence noxious special effects and accumulation features in the aquatic system and fauna respectively [16–22]. Metals go in into freshwater ecosystem via lithogenic and human activities [18, 22–24]. Benthic region is a key sink and a basis for metal pollution [25]. Built-up substances such as metals can be a sign of macrobenthic fauna-accumulation severity, ill health or death as the case may arise [24]. Certain residential chemicals in the sediment can exterminate benthic macroinvertebrates, thus

However, a recent study has shown that freshwater biota; prawn (*Macrobrachium* 

*rosenbergii*) showed significant differences (p < 0.05) in Mn, Cu, Pb and Cr and no significant difference (p > 0.05) in Fe, Zn and Cd. No observable p-values were noticed for Ni and V respectively (**Table 1**). In contrast, the freshwater biota; crab (*Sudanonautes africanus*) showed significant differences (p < 0.05) in Fe, Zn and Mn and no significant difference (p > 0.05) was observed in Pb, Cr and Cd. There was also no observed p-values in Ni and V (**Table 2**) [28]. It was noticed that the ranks of heavy metals and their spatial variability in the shrimps and crabs were Fe > Zn > Cu > Pb = Cd > Cr = Ni = V and Fe > Zn > Mn > Cu > Pb > Cr = Cd > Ni = V respectively.

The food chain structure has served as a pointer where metals are streamed along. Freshwater ecosystem pollution by metals, especially the heavy ones is on the increase daily around the world, causing several problems globally. Consequent of the buildup effect of certain heavy metals, particularly via the food chain, their bio-availability needs to be examined. This can be done via investigation of metal contents in biota in order to gather and predict its bioavailability and subsequent

Generally, freshwater decapods freely accumulate metals in their muscles in order to meet their basic metabolic needs. This makes them appropriate as bio-indicators of metals in the ecosystem. For example, freshwater *Sudanonautes africanus* and *Macrobrachium rosenbergii* accumulate high levels of Fe, Zn and Mn in their muscles [28] based on the facts that these metals play vital role in the respiratory pigment

**3. Assessment of metal contents in freshwater decapods**

*DOI: http://dx.doi.org/10.5772/intechopen.88103*

plummeting the food chain structure [26].

their muscles [12].

*rosenbergii*

**3.2 Bioaccumulation**

accumulation in the organism(s).

*Assessment of Metal Accumulation and Bioaccumulation Factor of Some Trace and Heavy… DOI: http://dx.doi.org/10.5772/intechopen.88103*

#### **3. Assessment of metal contents in freshwater decapods**

The assessment of metal contents in freshwater decapods is suitable for both water and terrestrial life forms. This is based on their significance as water indicators of pollutants via monitoring in spatial or temporal, in order to quantify their ecological role in the ecosystem. Even though the dangers of water pollution by metals are fully acknowledged, it is still a subject of discussing in line with the over increasing anthropogenic activities [9] and as well as the lithogenic activities [1].

Freshwater prawn and shrimp (Macroinvertebrates) are commonly recommended as fauna-indicators for evaluating the fluctuation of aquatic disorders in the region of probable pollution [3]. In general, decapods are of certain prominence for bio-monitoring survey [10], as the bedrock species in most aquatic systems [11], as well as the most tolerated species against water pollution. This shows their pollution status as regards to the buildup of the corresponding components of metals in their muscles [12].

#### **3.1 Accumulation of metals in** *Sudanonautes africanus* **and** *Macrobrachium rosenbergii*

Metal contamination in freshwater ecosystem is of utmost worry everywhere in the biosphere [13–15]. This might be as a result of their persistence noxious special effects and accumulation features in the aquatic system and fauna respectively [16–22].

Metals go in into freshwater ecosystem via lithogenic and human activities [18, 22–24]. Benthic region is a key sink and a basis for metal pollution [25]. Built-up substances such as metals can be a sign of macrobenthic fauna-accumulation severity, ill health or death as the case may arise [24]. Certain residential chemicals in the sediment can exterminate benthic macroinvertebrates, thus plummeting the food chain structure [26].

However, a recent study has shown that freshwater biota; prawn (*Macrobrachium rosenbergii*) showed significant differences (p < 0.05) in Mn, Cu, Pb and Cr and no significant difference (p > 0.05) in Fe, Zn and Cd. No observable p-values were noticed for Ni and V respectively (**Table 1**). In contrast, the freshwater biota; crab (*Sudanonautes africanus*) showed significant differences (p < 0.05) in Fe, Zn and Mn and no significant difference (p > 0.05) was observed in Pb, Cr and Cd. There was also no observed p-values in Ni and V (**Table 2**) [28]. It was noticed that the ranks of heavy metals and their spatial variability in the shrimps and crabs were Fe > Zn > Cu > Pb = Cd > Cr = Ni = V and Fe > Zn > Mn > Cu > Pb > Cr = Cd > Ni = V respectively.

#### **3.2 Bioaccumulation**

The food chain structure has served as a pointer where metals are streamed along. Freshwater ecosystem pollution by metals, especially the heavy ones is on the increase daily around the world, causing several problems globally. Consequent of the buildup effect of certain heavy metals, particularly via the food chain, their bio-availability needs to be examined. This can be done via investigation of metal contents in biota in order to gather and predict its bioavailability and subsequent accumulation in the organism(s).

Generally, freshwater decapods freely accumulate metals in their muscles in order to meet their basic metabolic needs. This makes them appropriate as bio-indicators of metals in the ecosystem. For example, freshwater *Sudanonautes africanus* and *Macrobrachium rosenbergii* accumulate high levels of Fe, Zn and Mn in their muscles [28] based on the facts that these metals play vital role in the respiratory pigment

*Crustacea*

traces of Cu, Pb, Cr, Cd, Ni and V [1–4].

their sediment background levels [8].

**2. Methodology**

**2.3 Data analysis**

SPSS version 20.0.

in the equation below:

**2.1 Sampling technique**

It has been documented that freshwater crab (*Sudanonautes africanus*) and prawn (*Macrobrachium rosenbergii*) have high deposits of Fe, Zn and Mn, with few

to cause serious health concerns when transferred to humans along the food chain. Environmental valuation of the noxiousness of metals in the freshwater *Sudanonautes africanus* and *Macrobrachium rosenbergii* had been shown to have probable human health hazard effect concomitant by way of ingestion [1].

Metal accumulation in freshwater decapods has been acclaimed and perceived

Health risks associated with heavy metals such as renal failure, skeletal deformation, and hepatic failure have been linked to their non-decomposable and persistence nature in the visceral organ-parts of humans [5]. This can lead to severe maladies like dysentery, stomach aches, head-tremor, anemia, paralysis, nausea, paroxysm, melancholy and even respiratory disorders [6], which can be either acute or chronic forms; neuron toxicity, oncogenic, genetic alteration or teratogenicity [7]. High levels of bio-accumulated heavy metals in freshwater decapods have been identified in these ranks; Fe > Zn > Mn > Cu > Pb > Cr [1] as interconnected with

Samples of freshwater prawns and crabs (*Macrobrachium rosenbergii* and *Sudanonautes africanus*) were captured and collected monthly from March 2015 to August 2016 at designated stations by some fishermen, using local-hand nets enticed with ox-heart, set at the river bank of each station 24 hours before capturing. The prawns and crabs were collected and kept in different labeled plastic rubbers according to the stations, filled with the river water and immediately taken

**2.2 Extraction and determination of heavy metals in freshwater decapods**

Employing the methods of [1], the freshwater biota was oven dried at

105°C. About 2 g of a dried up standardized sample of each tissue were digested and sample was made up to about 50 ml of purified water. Samples of the biota were analyzed for iron, manganese, zinc, copper, chromium, cadmium, nickel, lead, and vanadium with an AAS (atomic absorption spectrophotometer; SOLAAR 969AA

Simple descriptive analysis, ANOVA (Analysis of variance), was employed using

To determine the accumulation rate of heavy metals in the freshwater biota, the bio-indices; bioaccumulation factor was employed with Micro Excel version 2013. Bioaccumulation factor (BAF) is the concentration of metals in sediment or water

BAF = concentration of metals in sediment/water (mg/kg) \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ concentration of metals in Crab/prawn (mg/kg)

[8]. This can be represented

(1)

to the laboratory for heavy metal analysis and identifications.

UNICAM, Spectronic Unicam, Cambridge, UK) [1].

over the concentration of metals in the biota in mg kg<sup>−</sup><sup>1</sup>

**156**

