Environmental Assessment
Volume E-3.9
Tailings Facility
Oceanography
Ambatovy Project
91
January 2006
3.9.3
Marine Outfall Assessment – Physico-Chemical
Composition and Possible Impacts
3.9.3.1 INTRODUCTION
A large body of information exists on the approximately 1,500 known chemical
compounds and elements, which could act as pollutants in the marine
environment (USEPA, 2004). The impacts of these on individual organisms
depend on a number of factors, which can alter the inherent character of the
chemicals in question. These factors could be as simplistic as a change to
ambient temperature or a change in the pH of the water. Additional factors
include individual organism’s range of tolerance to these changes, the
concentration of the pollutant and the time of exposure to it. In addition, the
impact of pollution may not affect the organism or community directly but is
dependent on the pollutants fate within the aquatic environment (Figure 3.9-1).
For example, a chemical constituent such as zinc, an important micronutrient in
plants, does not present a threat to these primary producers. The algae, however,
absorb this element and through a process of bio-accumulation can become toxic
at a higher trophic level (Figure 3.9-1). For example, predatory fish that prey on
herbivorous fish accumulate the zinc in their livers or kidneys. The
concentrations of zinc in their organs then affect the fish’s fitness and ability to
reproduce. A decrease in reproductive rates then lowers abundance in a
particular population and in turn affects community structure (Figure 3.9-1). A
community response over time to a pollutant may change its trophic structure
(reduction of predators), which results in an overall increase in the amount of
grazers. The high numbers of grazers places pressure on the primary producers,
leading to an overall reduction in food resources. This results in a reduction in
biodiversity and a degradation of the environment.
