**1. Introduction**

Recently, marine environment such as coastal and estuarine regions is contaminated by waste created by human activities containing elevated concentrations of nutrients, organic pollutants, trace metals, and radionuclide [1, 2]. Some of these chemicals are highly toxic and persistent, and these elements have a strong tendency to become concentrated in marine food webs once they enter this aquatic environment. The pollution of coastal zones near metropolitan areas, by these anthropogenic wastes, is due to the large coastal human population and the enormous amounts of sewage discharged into coastal waters [3–6]. The addition of waste products into rivers, estuaries, and wetland environment (**Figure 1**), especially those in industrial and population centers, has led to a significant increase in this pollutant level, especially metal contamination [7]. Accumulation of metals in surface sediments from industrial effluents and urban sewage discharged into the aquatic environment without proper treatment will easily be identified through metal spatial variations in sediments [8, 9].

Rivers can transport metals into the marine environment, and the amount of the chemical element input to the oceans depends on their levels in the river sediments, water, suspended particulate matter, and the exchange processes that occur in the estuaries [10]. With recent industrialization and human activities (**Figure 2**) that happen in the coastal region, these metals are continuing to be discharged to

#### **Figure 1.**

*Wetland ecosystem in Malaysia. This ecosystem may be polluted by metal pollutants derived from human activities. Photo by Ong Meng Chuan.* 

#### **Figure 2.**

*Example of human activities (fishery industry) in the Gulf of Morbihan, France. Photo by Ong Meng Chuan.* 

estuarine and coastal environment through rivers, runoff, and land-based point sources where the chemical elements are produced as a result of metal refinishing by-products.

Metal concentrations in harbor or estuarine sediments usually are high due to significant anthropogenic contaminant loading carried by the upstream of tributary rivers and settled down at this area [11, 12]. The sediments itself can serve as a metal pool that can release metals to the overlying water via natural or anthropogenic chemical and physical processes, causing potential adverse health effects to organisms that live at the ecosystems [13, 14]. Moreover, marine organisms can uptake these chemical elements, which in turn enhances the potential of some elements entering into the food chain. Therefore, metal contaminations are considered by scientists as an environmental problem today in both developing and developed countries throughout the world [15].

Metals accumulate in the sediments through complex physical and chemical adsorption mechanisms depending on the nature of the sediment matrix and the properties of the adsorbed compounds [16, 17]. Several processes had been

#### *Sediment and Organisms as Marker for Metal Pollution DOI: http://dx.doi.org/10.5772/intechopen.85569*

identified for controlling the metal concentration in sediment, such as direct adsorption by small particle of clays, adsorption of hydrous ferric and manganic oxides which may also associate with clay fraction, adsorption of natural organic substances associated with inorganic particle, and precipitation as new solid phases [18, 19]. With this unique characteristic, sediments are usually used as geo-marker for monitoring and identifying the potential pollution sources in aquatic environment. These sediment analyses are an important tool for the determination of pollutants as they sink in the bottom through different chemical constituents and can reflect the pollutant proxy in the environment. In addition, the sediments act as a useful indicator of long- and medium-term metal flux in industrialized estuaries and rivers, and they help to improve management strategies as well as to assess the success of recent pollution controls [20].

 More than 90% of the metal compound load in marine aquatic systems is bound to suspended particulate matter and sediments [21]. Therefore, sediments serve as a pool of metals that could be released to the overlying water from natural and anthropogenic processes such as bioturbation and dredging, resulting in potential adverse health effects toward surrounding organisms [22, 23]. Besides that, it is necessary to determine the metal contamination in estuarine ecosystem because this area is the most productive ecosystem which serves as feeding area, migration route, and nursery area of many juvenile and adult organisms from freshwater and marine water ecosystem. Due of these important to the ecosystem, effective remedial actions to minimize the pollution by metals need to be distinguished if pollution are expected occurs there [24].
