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Effects of the Discharge of Iron Ore Tailings
of solid wastes of anthropogenic origin on the beaches and floating in the
water, in quantities comparable to densely populated areas of the northern
hemisphere (Bravo et al., 2009; Hinojosa and Thiel, 2009).
The mining industry in Chile, mainly in the central and northern parts
of the country, comprises 421 plants, of which ca. 5% exert direct influence
on the coast (Escobar, 2002). It may be supposed a priori that alteratio ns
in natural coastal ecosystems occur along the coast of northern Chile when
considering the large number of mining operations established along the
coast above 30° S. As a result of intense mining activity over many years,
diverse types of tailings have been released to the sea, which have generated
important effects on the marine environment, including mass mortalities
of algae, invertebrates, and fishes (Castilla and Nealler, 1978); nevertheless, few studies have investigated these effects in Chile (Fariña and Castilla,
2001; Vásquez, 2005; Vásquez et al., 1999, 2000). Although many studies
have investigated the environmental impacts on subtidal, soft-bottom habitats, few studies have been done on the effects on rocky subtidal communities (Ellis, 2002a; Marchini, Gauzer, and Occhipinti-Ambrogi, 2004), those
mostly associated with waste waters (Chapman, Underwood, and Skilleter,
1995; Echavarri-Erasum et al., 2007; Fraschetti et al., 2006; Roberts et al.,
1998; Terlizzi et al., 2002; Underwood and Chapman, 1996).
Iron mining has been one of the important industries on Chile’s northern
coast. The most prominent of these is the iron ore pellet plant of the Compañia Minera del Pacifico S.A. (CMP) located on the coast near Huasco
(288300 S). This installation has discharged process tailings into the nearby
Ensenada Chapaco since 1978. In contrast with most other types of mine
tailings in Chile, which may contain toxic metals and process chemicals, the
CMP tailings in Chapaco are largely inert (Núñez, 1993) because no chemicals are used in the process, which is based on magnetic separation. The tailings, which include iron ore and clay particles, produce high turbidity in the
waters of Ensenada Chapaco, as well as heavy sedimentation of particulate
materials (Stotz et al., 1994). Similar effects have been described by coastal
sediments discharges from diamondiferous dune sands mining (Smith et al.,
2002).
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Among the effects of turbidity, interference with light transmission is
important in affected waters because of its adverse effect on primary production (Bellamy et al., 1972; Hanelt, 1992; Margalef, 1972). Water turbidity has been cited as a possible cause for low fecundity in macroalgae
(Hagmeier, 1971; Lobban and Wynne, 1981). Stress due to turbidity could
eliminate algae or change their limits of distribution with depth (Bellamy et
al., 1972; Lewis, 1964; Reish, 1972). Excessive turbidity might inhibit feeding mechanisms in filter feeders such as oysters and mussels, interfering with
their growth (Grant and Thorpe, 1991; Meyhöfer, 1985), although Wilber
(1971) demonstrated that increases in suspended solids did not necessarily produce mortalities in bivalves. Although adults of invertebrates might
not be affected by increases in suspended solids, their reproductive capacity
could be severely reduced (Bricelj, Malouf, and Quillfeldt, 1984). The various effects of inorganic particulate materials on marine fauna have been well
documented (see Airoldi, 2003, for review; Moore, 1977).
Indirect effects of particulate matter in suspension might be adsorption of
dissolved organic matter and promotion of microbial growth in the water
column (Wainwright, 1987). In ecosystems stressed by particulate matter,
filter feeders might be favored over other trophic groups (Bellamy et al.,
1972) and be maintained in an ‘‘immature state’’ (Davis, 1993; sensu Smith
and Simpson, 1992). A more obvious effect of allochthonous suspended
matter is heavy sedimentation, which could impede settlement of invertebrate larvae and algal propagules on rocky substrates (Núñez, 1993; Santos 1993), as well as suffocate juvenile organisms (Johannes, 1972; Menzie,
1984; Roberts et al., 1991; Walters, 1992). As little as 1 mm of deposited
material could prevent the settlement of some invertebrates on rocky substrates (Wilber, 1971), compared with deposition rates of 20 mm yr-1 with
no obvious effects on organisms in soft-bottom environments (Burd, 2002;
Ellis, 2002a). Nevertheless this has been a rarely studied aspect, compared
with studies regarding factors such as light or predation in hard-bottom environments. More recent studies show that turbidity and consequent associated sedimentation could be key factors affecting rocky subtidal community
structure (Airoldi, 2003; Balata, Piazzi, and Cinelli, 2007; Irving and Con-

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