Biodiversity Study of Mangrove Forest in Lawas Sarawak

Mangroves are one of the most abundant biological diversity with a valuable ecosystem. They are found on sheltered shores and in estuaries in tropical and subtropical regions. Mangrove ecosystems are made up of organisms that interact with each other in mangrove habitats. It is estimated that mangroves cover more than double the number of species found on land, with the best results occurring in tropical coastal areas. Mangroves are found in Malaysia, particularly in Sarawak, and have an area of around 167,312 ha, which is valuable both financially and ecologically. However, the majority of mangroves found in Southeast Asia are endangered, partially denuded, and have poor species diversity. Sarawak is one of the least affected areas, but there are only a few mangrove surveys being conducted there. The main goal of this study is to conduct a biodiversity study of the mangrove forest in Awat-Awat, Limbang, Sarawak. To support the objectives of the study, three transects were established. The results showed more than 20 species of this mangrove area from upstream to downstream, as well as some wildlife species. This abundance of biodiversity was due to the good environmental conditions, such as less pollution on the soil and better water quality. The ecological function of plants, animals, and the environmental conditions, such as the soil and water, are interdependent and interact to sustain their existence in the same environment, which is Awat- Awat Mangrove Forest (Lawas Limbang) Malaysia. This area can be supported as a potential edu-ecotourism research and development area for the mangrove region of Sarawak in Malaysia.


Introduction
Coastal mangroves forests are native to tropical and sub-tropical tidal areas.Mangroves are among the most productive ecosystems that can be found on sheltered shorelines and in estuaries.A mangrove possesses a unique ability to adapt to soil that is constantly waterlogged and in water that has a fluctuating salinity with low oxygen content [1].Mangroves are recognized as the most abundant biological diversity with its valuable ecosystem.Mangroves grow in sheltered coastal and estuary areas in the tropical and subtropical regions.Mangroves adapt their system to develop specialization in extreme environmental conditions (salinity, anaerobic soils, etc.) [2] [3].
The mangrove ecosystem is made up of organisms (plants and animals) interacting with their environment within the mangrove ecosystem [4].It has been estimated that mangroves support more than double the number of plant and animal species on land, with the best results occurring in tropical coastal regions [1].Mangroves are a valuable resource for both economic and non-economic reasons such as forestry, fisheries, wildlife conservation, eco-tourism, physical environment protection, etc.Despite these benefits, the total mangrove population is still significantly depleted due to various IOP Publishing doi:10.1088/1755-1315/1316/1/012002 2 excisions, with anthropogenic activity being the main contributor to the degradation and loss of the mangrove ecosystem.
In addition, most of the Southeast Asian mangroves are endangered, partially denuded, and poor in number of species [5][6].Malaysia, particularly Sarawak, has approximately 167,312 ha of mangroves [7], and is considered one of the least affected areas.However, only a small number of mangroves are being studied in Sarawak [8][9].This study aims to carry out an ecological survey on Awat-Awat Mangrove Forest, Lawas Limbang in Sarawak.The ecological survey will describe the dominant plant species, wildlife, and environmental conditions (soil and water) as the important factors that support the community ecology of the Awat-Awat mangrove forest.

Site description
The site of the study was in the mangrove in the northern part of the town of Lawas in the state of Limbang, Sarawak, which is situated between the states of Brunei Darussalam and Sabah (Figure 1).

Plant survey
A boat was used to survey the mangrove plant from upstream to downstream.Twelve sampling plots (10 x 10 m square) were set up from landward to seaward of the forest to record the availability of mangrove species.Images and samples of vegetation were collected and compared with the herbarium to determine the species.A schematic profile of the various mangrove species found in the Awat-Awat mangrove forests was created by line transect.A line transect (100 m long) was established in three coastline areas to maximize the plant composition from inland up to the coastline.

Animal survey
Field Transects for mangrove animal survey (100m length) for the Awat-Awat mangrove forest, Sarawak.Mangrove ecosystem baseline ecological studies are necessary for management and conservation purposes.

Soil sampling
This research involved taking 300 soil samples in five different depths of the soil which are 0-15cm, 15-30 cm, 30-50 cm, 50-100 cm, and >100 cm [12].The soil samples were collected in a vacuum plastic bag labelled with a label to reduce contamination.The entire sample was placed in an ice box at a low temperature during transport and then sent to the lab for analysis.

Water sampling
The water samples were obtained from both disturbed and intact mangroves in the Awat-Awat mangroves forest.Twelve stations were chosen for each location, and the water samples were transported from the seaward side to the landward side using in situ equipment.The samples were taken three times at each station for laboratory testing.The standard procedures for water sampling and analysis were followed according to the APHA Methods [13][14] [15].

Plant diversity
The diversity of the mangrove plant species found in Awat Awat mangrove forest is varied.It is found from the coast to the coast and from land to sea level.Table 1 shows that there are sixteen families of mangroves and twenty-four species found in the forest.The dominant species in the forest are Rhizophora apiculata and Nypa fruicans, which are found in almost all areas.The least dominant species is Schypiphora hydrophyllaceae which is only found in a few areas in the mangrove forest [16].

Table 1. Mangrove species and family in Awat-Awat mangrove forests
There are 4 families that were found in transect 2 and each of them was also represented by a single species.These families are Rhizoporaceae (R. apiculata), Sonneratiaceae (S. alba), Avicenniaceae (A. alba) and Arecaceae (N.fruticans).The schematic profile of transect 2 is shown on the Attachment 2.
In Transect 3, two species from the family Sonneratiaceae (S. alba and S. caseolaris) were found in this area, while only one species from the family Avicenniaceae (A. alba) was found in the area.In Transect 2, the mangrove succession was still in progress when the R. Apiculata species began to take over the pioneer species in Transect 1, while it has not yet taken over Transect 3. R. Apiculata trees are not found in this transect, as almost the entire area is still dominated by the Avicenniaceae and Sonneraceae families.N. fruticans species can still be found in this transect, although it is scarce.

Animal diversity 3.2.1. Fisheries product.
The most important economic value that could be gained from the mangrove products in many places is the coastal fisheries and the shelter protection provided by the mangrove ecosystem [17].
Rhizophora   Furthermore, the most famous production that could derive from mangrove ecosystem in Awat-Awat mangrove forest is "tahai" (Figure 6).Tahai is a smoked fish, which has to be smoked and grilled for long hours uses charcoal that is made from Rhizophora spp.Tahai could be saved and preserved for a long period and has usually been used as additional food for dishes to increase flavor and sweetness.In addition, the mangrove environment is also could be used as a spawning and nursery ground for marine shrimps and fishes.

Wildlife diversity.
Mangroves are a habitat of a large number of mammals though only a few live there permanently.There are even fewer mammals that are restricted to mangroves.The proboscis's monkey or bekantan in the Malay language are indigenous species of Borneo mangroves where they feed on leaves of Sonneratia and Nypa.Several kinds of crab-eating macaques (Figure 7), live there even though that species can live in other areas commonly [18].Furthermore, birdlife is abundant in mangroves despite relatively few species that are endemic to mangroves or have mangroves as their main habitat.In addition, the most important reptiles that can be found in mangroves are the saltwater crocodiles and monitors.

Soil physiochemical properties
Table 2 provides an overview of the physiochemical properties of the soil in three zones of Awat-Awat mangrove forest Lawas in Sarawak, which are seaward, middle ward, and landward.The soil texture of the mangroves in these three zones was found to be sandy loam, and the soil fractions of sand and clay were found to be sand-rich (67.00-73.52%),silt-rich (11.89-16.23%),and clay-rich (12.41-15.60%).
The soil pH of the water in the three zones ranged between 2.87-3.83,and the soil pH of the 1M KCl ranged between 2.39-2.82.The seaward zone had the highest soil pH in comparison to water and 1M KCl, and there was a significant difference between the three zones.This is because the topography of each zone is unique.Tidal and inundation and root systems in each zone may be associated with soil pH changes [19].
The soil organic matter (SOM) ranged between 9.22 and 25.93% at three different zones and total organic carbon (TOC) ranged between 5.35 and 15.04%.SOM and TOC were highest at the middle ward zone at 25.93 a (±0.403%) and TOC at 15.04a (±0.23%), respectively.The mean difference in SOM and TOC between the three zones was significant.According to Marchand [20], the soil organic matter and total organic increased with the distance from the seaward zone to the landward zone and with the population density of trees in the zones themselves.The presence of high litter fall at the zones may also contribute to the organic matter.The environmental condition of the mangrove zone also affects the organic matter, the total organic carbon, and the soil depth with the tidal inundation level and the root characteristics of soil particles.Soil pH decreased between soil depth 1 and soil depth 5, indicating that soil pH at soil depth 5 tends to be more acidic.This is due to the fact that soil at soil depth 5 has a high carbon build-up caused by the decomposition of microorganisms, which results in a higher amount of H+ being produced in the soil, thus increasing soil acidity [21].Mangrove ecosystems are generally water-logged, lack proper aeration, and contain a large amount of organic material that decomposes slowly at different soil depths [22].

Water quality
The results of Table 3 show that the mean values for pH, BOD, COD and AN were below the maximum level and are classified as acceptable amounts to the water.The average water quality status for the river water of both the mangrove forest and undisturbed river water was Class III [19] [23].This abundance of biodiversity was supported by good environmental conditions, such as low soil contamination and good water quality (class III).As a function of the ecological system, there are interactions and interactions between plants, animals, and the environmental conditions, such as land and water, to sustain their life within the same habitat, which is Awat-Awat Mangrove Forest (Lawas Limbang) Sarawak, Malaysia.Based on the biodiversity found within Awat-Awat Mangrove Forest, the area has the potential to be a destination for edu-ecotourism (education and eco-tourism) as well as one of the potential research and development areas for mangrove forests in Malaysia's state of Sarawak.

Conclusion
More than 20 of mangrove plants dominated by Rhizophora apiculata from the Rhizophoraceae family and some wildlife species were identified from upstream to downstream in this mangrove area.The zonation pattern of the various types of mangroves found in Awat-Awat Mangrove Forest was evident from land to sea.The abundance of biological diversity found in this forest was supported by good environmental conditions such as low soil contamination and good water quality (class III).Biodiversity in Awat-Awat Mangrove Forest is such that this area has the potential to be managed as an educational and eco-tourist destination, as well as one of the research and development opportunities for mangrove forests in Malaysia's Sarawak state.

Figure 2
shows the location of three Transects of undisturbed Mangrove Ecosystem in the Awat-Awat mangrove forest in Sarawak Malaysia.

Figure 2 .
Figure 2. Line transects and sampling design developed for vegetation study detail

Figure 3 .
Figure 3. Fishes' product of Awat-Awat mangrove forestIn Awat-Awat mangrove forest, the fisheries products that could be harvested include fishes, shrimps, crabs, seaweed, squids, clamp that are abundant seasonally (Figure3, 4, 5 and 6).Those products are usually sold by the local people to the market in Sundar and Lawas town and some of them are exported to Brunei.

Figure 6 .
Figure 6.Air-drying fish as the main ingredient of "tahai" by the local people of Awat-Awat

Table 2 .
Mean soil physiochemical properties in three different zones at Awat-Awat Mangrove Forest Lawas, Sarawak Different alphabets within a row indicate significant different between mean of soil physio-chemical properties of at three different zones using Tukey test at P≤0.05.Plus, and minus symbols