Land reclamation along with other coastal activities such as shipping and dredging (clearing out mud, weeds and rubbish from the beds of water bodies) increases the levels of sedimentation in the water, which in other words, causes water pollution. These sediments could affect the giant clams in 3 different ways.
Firstly, photosynthetic activity of zooxanthellae in the giant clams is inhibited. It is caused by the presence of copper in the sediments despite it being an important micronutrient for plants and animals. This means that the giant clams would not have sufficient nutrients.
Bleaching of giant clams, which is similar to coral bleaching, would then be observed. Thus, the continual increase in copper concentration and other factors that result in giant clam bleaching can lead to the demise of them.
Secondly, the unstable sediments on the coral reefs reduce the ability for giant clam larvae to settle. Giant clams have poor early life survivorship and with the increase in sediments, it further threatens the survival rates of their larvae.
Thirdly, nutrients from sediments, to a certain extent, promotes the growth rate of the giant clams. However, scientists have found that these increase in nutrients could reduce the shell’s density, causing them to be more vulnerable towards predators and natural conditions. This is similar to the effects of global warming.