Monitoring of Nutritional Status in Sediments, Water and Plant Leaves from Ratargul Swamp Forest at Sylhet in Bangladesh

Introduction

Fresh water swamps are the unique ecosystems having very specific vegetation. Water is the prime requisite of the vegetation of the swamp forests [1]. These forests are sites of natural succession and therefore contain all the groups of plant kingdom in a single place [2]. Ratargul swamp forest is the only one fresh water swamp ecosystem in Bangladesh. Swamps play a vital role in landscaping with a wide variety of flora and fauna [3]. Due to variation in topography, a distinct floristic diversity is seen which is quite varied from the surrounding area [4]. They support characteristic vegetation on account of specialized edaphic conditions, as influenced by free water accumulation [5]. They form integral part of the wetland ecosystems, serving as habitats, nursery grounds and sources of food for many organisms [6]. Forest swamp has important hydrological supportive functions including providing water storage space, adjusting and saving the flood peak, keeping the underground water level, recharging runoff, taking the degradation of pollution and purifying water quality etc [7]. An ecosystem consists of plants, animals and microorganisms, which live in a definite zone along with the physical factors such as sediments; water and air, within an ecosystem, there are dynamic interrelationships between the living form and their physical environment [8]. This relationship is manifested as the natural nutrient cycles which provide a continuous circulation of the essential constituents necessary for sustains the life processes on an ecosystem [9].

The swamp water has low pH, nutrient levels and very low levels of anions and cations in the surface water, even lower than in the ground water, whereas nutrient limited sediments retards plant growth. Therefore, plants growing on peat sediments must develop some specific mechanisms, such as organic acid exudation from roots, to accumulate nutrients [10]. In general, plant species that grow and dominate in an ecosystem are affected by various environmental parameters, so differences in plant physiology, e.g. seed germination, relative growth rate, and competition with other plant species, can also express the changes in the environmental development of an ecosystem [11]. Nutrient concentration is used as an important parameter to recognize critical processes of an ecosystem. Nitrogen (N) and phosphorus (P) both are shown to control the rates of ecosystem processes and primary productivity in both aquatic and terrestrial ecosystems [12]. Global pattern analysis of C, N and P stoichiometry in foliage and litter supports the hypothesis that N is the major limiting nutrient in temperate regions, while P tends to limit ecosystem productivity and processes in the tropical regions [13]. The objectives of the study was to investigate the concentration of total nitrogen (TN), total phosphorus (TP) and total organic carbon (TOC) in sediments, water and plant leaves of the forest and their inter relationship.

TOC (%)

St-1 St-2 St-3 St-4

Sampling station

High amount of nitrogen (N) in the sediments of Sundarbans mangrove forest was also found by previous study [21]. The deposition and decomposition of huge quantities of solid wastes from the forest and surrounding area, and the use of N as a fertilizer in the agricultural land are responsible for the enrichment of TN content in the sediments. Study concluded that nitrogen content in the sediments of the forest was suitable for growth of pant and microorganism in the forest.

0.000 0.100 0.200 0.300 0.400 0.500 0.600

TN (%)

Figure 3: Status of TN in sediments at different sampling stations at Ratargul swamp forest. Total phosphorus (TP): Total phosphorus content was ranged from 0.032 to 0.035%, where mean contents were 0.034%. The highest and lowest TP contents were found 0.035 and 0.032% at St-3 and St-2, respectively (Figure 4). The average TP contents were 0.034, 0.032, 0.351 and 0.034% at St-1, St-2, St-3 and St-4, respectively. Study stated that phosphorus (P) contents were suitable for growth of pant and microorganism in the forest. The TP content in the surface sediments of wetland was 0.034% which was significantly higher than other wetland [20]. Another study in Sundarbans mangrove forest revealed that high amount of phosphorous (P) in sediments [21], due to deposition and decomposition of huge quantities of solid wastes in the forest and surrounding area, and the use of P as fertilizer in the agricultural land may be responsible for the enrichment of TP in sediments.

St-1 St-2 St-3 St-4

Sampling station

Click to enlarge

Sampling station

Figure 5: The TN of water in Ratargul swamp forest at different sampling season. Total phosphorus (TP): The total phosphorus (TP) contents were ranged from 0.002 to 0.366% with a mean of 0.166%, where significant variation of total phosphorus in dry and wet season (P>0.018, df=3) was found. The highest TP content 0.366% was found at St-3 during the wet season and the lowest was 0.002% at St-2 during dry season (Figure 6). The average TP content along the Ratargul swamp forest was 0.027, 0.028, 0.068 and

6.42% at St-1, St-2, St-3 and St-4, respectively in dry season, whereas, during the wet season the TN contents were 15.52, 15.37, 21.523 and 19.133% at St-1, St-2, St-3 and St-4, respectively. A study found that higher amount of N content in the wet season than the dry season due to use of excessive nitrogen in the surrounding agricultural land and mixed with the water through the run off during the wet season [21].

$$ = 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $$ Wet season

0.047% at St-1, St-2, St-3 and St-4, respectively in dry season. However, during the wet season, the TP contents were 15.52, 21.523, 15.37 and 19.133% at St-1, St-2, St-3 and St-4, respectively. The study found that the amount of TN and TP were higher in the wet season than the dry season due to use of excessive nitrogen fertilizer in the surrounding agricultural land which in turn mixed with the water through the run off during the wet season.

Dry season

A B

$$ \mathrm {d} = \mathrm {d} _ {1} + \mathrm {d} _ {2} + \mathrm {d} _ {3} + \dots + \mathrm {d} _ {n} $$ $$ = 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $$

4 4.5

Sampling stations

$$ \mathrm {d} = \mathrm {d} _ {1} + \mathrm {d} _ {2} + \mathrm {d} _ {3} + \dots + \mathrm {d} _ {n} $$ $$ \mathrm {d} = \mathrm {d} _ {1} + \mathrm {d} _ {2} + \mathrm {d} _ {3} + \dots + \mathrm {d} _ {n} $$ $$ = 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $$ $$ = 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $$

Sampling stations

5

4 4.5

Sampling statoins

0.102, 0.11, 0.126 and 0.122% during dry season and 0.031, 0.036, 0.03 and 0.053% during wet season at St-1, St-2, St-3 and St-4, respectively (Figure 11). TP contents were 0.093, 0.086, 0.98 and 0.098% in brown leaves of Hijal during dry season at St-1, St-2, St-3 and St-4, respectively. During wet season TP contents in brown leaves were 0.029 at St-1, 0.039 at St-2, 0.025 at St-3 and

0.041% at St-4. In the Koroch plant leaves, there was statistically significant (p> 0.001) variation of TP in dry and wet season, however a significant variation (p>0.002) was found in green and brown leaves. The highest content of TP was 0.118% (brown leaves) in St-3 during the dry season and lowest was 0.04% (green leaves) in St-3 during the wet season. The TP contents were 0.112 (St-1), 0.107 (St-2), 0.012 (St-3) and 0.106% (St-4) in green leaves during dry season while TP were 0.62 (St-1), 0.067 $$ \mathrm {d} = \mathrm {d} _ {1} + \mathrm {d} _ {2} + \mathrm {d} _ {3} + \dots + \mathrm {d} _ {n} $$ $$ = 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $$ (St-2), 0.047 (St-3) and 0.78% (St-4) in wet season (Figure 12). In brown leaves of Koroch plant TP contents were 0.104, 0.092, 0.109 and 0.096% during dry season, and 0.041, 0.043, 0.04 and 0.054% during wet season at St-1, St-2, St-3, and St-4, respectively. The TP contents in plant leaves were higher in dry season than wet season might be due to the high temperature in wet season, though the TP was higher in brown leaves than green.

$$ \mathrm {d} = \mathrm {d} _ {1} + \mathrm {d} _ {2} + \mathrm {d} _ {3} + \dots + \mathrm {d} _ {n} $$ $$ \mathrm {d} = \mathrm {d} _ {1} + \mathrm {d} _ {2} + \mathrm {d} _ {3} + \dots + \mathrm {d} _ {n} $$ $$ = 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $$ $$ \mathrm {d} = \mathrm {d} _ {1} + \mathrm {d} _ {2} + \mathrm {d} _ {3} + \dots + \mathrm {d} _ {n} $$ $$ \mathrm {d} = \mathrm {d} _ {1} + \mathrm {d} _ {2} + \mathrm {d} _ {3} + \dots + \mathrm {d} _ {n} $$ $$ = 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $$ Figure 11: The TP in green (A) and brown (B) leaf of Hijal plant in different sampling season.

Click to enlarge

* Correlation is significant at the 0.05 level and Correlation is significant at the 0.01 level (2-tailed). SP=TP in Sediments, SN=TN in Sediments, WP=TP in Water, WN=TN in water, HLP= TP in the leaf of Hijal, HLN= TN in the leaf of Hijal, KLP=TP in the leaf of Koroch, KLN = TN in the leaf of Koroch. Table 1:** Correlations among nutrients in sediments, water and plant leaves.

The study found that there was a significant positive correlation between TP of plants leaves and TP of water. In both Koroch and Hijal leaves, the amount of TP was increased when the amount of TP was increased in sediments. There was a positive statistical correlation between TN of leaves of Hijal and TN of water. Study found that the content of TN in the leaves of Koroch increased with the increasing of TN in the sediments and there was a strong positive statistical correlation between them. Study showed that there was a significant positive correlation between TP of plants leaves and TP of sediments. The TP in leaves of Hijal increased with the increase of TP in water and there was also a strong positive correlation between them. The content of TP in the leaves of Koroch increased with the increasing of TP in sediments and there was a strong positive statistical relationship between them. The vegetation responds positively to surface water inorganic N (NH4-N, NO3-N) and P (PO4-P) [22]. The content of TP of plants leaves increased with the increase of the TP of sediments and also showed a significant positive correlation. The content of TN in the leaves of Hijal increased with the increase of TP in water. There was a strong positive statistical relationship between them. The content of TN in the leaf of Koroch also increased with the increase of TN in the sediments. The vegetation responds positively to available N and P in surface sediments [22].

Conclusion

Results of the study concluded that the sediments of the Ratargul Swamp forest were nutrients-enriched which indicated that more input of external anthropogenic nutrient in turn may disturb the present ecological balance of this complex ecosystem. The amount of TN and TP in the water was higher in the wet season than dry season which might be due to the excessive use of nitrogen and phosphorous in the surrounding agricultural land. The average TOC in the plant leaves were higher in wet season than dry season, while the TN and TP in the plant leaves were higher during dry season than in the wet season. Thus the study concluded that the amount of TN and TP in the plants leaves depend on the amounts of TN and TP in the sediments and water. Finally, the study stated that aquatic environment of Ratargul swamp forest in terms of nutrients load are suitable with the changes of seasons. Thus the study suggested maintaining the sound and healthy ecosystem of the forest and surrounding areas are needed regular monitoring and proper management of the forest.

Acknowledgment

Special appreciation to Mr. Rony Basak (Assistant Professor, Department of Geography and Environment, Shahajalal University of Science and Technology, Sylhet), Mr. Nuraalam Siddique (Assistant Professor, Department of Biotechnology, Bangabandu Sheikh Mujibur Rahman Agricultural University, Gazipur) and Mr. Md. Nahian (Dept. of ESRM, MBSTU) for their constructive advices and suggestions during the research work.