of suitable size to colonize. In the case of remote atolls in
the Pacific, this is often marked by the appearance of
Lapita pottery (Bellwood, 1987; Weisler, 1994; Nunn,
1999). Human occupation has shaped atoll ecosystems
in a number of ways. The vegetation of many has been
modified with the planting of coconut plantations, and
the introduction of plants as described above.
Human activities have had the greatest impact where
there are high population densities (See Mining and Quarrying of Coral Reefs; Engineering on Coral Reefs with
Emphasis on Pacific Reefs). Impacts have affected corals
and other carbonate producing organisms. Corals suffer
mortality when smothered by sediment (Zann, 1982).
Seawater contamination is indicated by increased nutrient
levels. Sewerage contains nutrients, and contamination of
seawater is often measured by using coliform counts.
Increased nutrients can cause localized coral mortality as
observed by a high incidence of dead corals on the
oceanward reef flat in front of Bikenibeu, a densely populated island on the southern rim of Tarawa Atoll, which
has received sewerage outfall in the past (Lovell, 2000).
Domestic waste poses a further threat to ecosystems on
some atolls. Certain macrofauna located in the shallow areas
of the lagoon at Tarawa may have been organically enriched
from land-based anthropogenic sources (Kimmerer and
Walsh, 1981; Newell et al., 1996). Also, direct disposal
of raw sewerage into the sea has likely increased the seawater nutrient level causing bacterial contamination of
the lagoon seawater at Tarawa, but the lagoon ecosystem
has been flourishing as a result (Kelly, 1994).
On atolls such as those in the Marshall Islands, Funafuti
in Tuvalu and Tarawa in Kiribati increasing population
pressure has led to houses being built in inappropriate
locations, such as near active beaches and on low-lying
areas. In South Tarawa this has prompted the construction of coastal protection structures to avoid overtopping
during storms and high water events. There are a large
number of reclamations of varying designs and materials
built to expand the land area (Figure 9). Betio, Bairiki,
and Bikenibeu, the administrative centers of Kiribati, have
grown significantly compared to the comparatively pristine islands of Buariki and Abatao on the same atoll,
Atolls, Figure 7 Three atolls in Tuvalu, showing distribution of mangrove and Pemphis, and the degree that these environments
are impounded (after Woodroffe, 1988).
64
ATOLLS
the Pacific, this is often marked by the appearance of
Lapita pottery (Bellwood, 1987; Weisler, 1994; Nunn,
1999). Human occupation has shaped atoll ecosystems
in a number of ways. The vegetation of many has been
modified with the planting of coconut plantations, and
the introduction of plants as described above.
Human activities have had the greatest impact where
there are high population densities (See Mining and Quarrying of Coral Reefs; Engineering on Coral Reefs with
Emphasis on Pacific Reefs). Impacts have affected corals
and other carbonate producing organisms. Corals suffer
mortality when smothered by sediment (Zann, 1982).
Seawater contamination is indicated by increased nutrient
levels. Sewerage contains nutrients, and contamination of
seawater is often measured by using coliform counts.
Increased nutrients can cause localized coral mortality as
observed by a high incidence of dead corals on the
oceanward reef flat in front of Bikenibeu, a densely populated island on the southern rim of Tarawa Atoll, which
has received sewerage outfall in the past (Lovell, 2000).
Domestic waste poses a further threat to ecosystems on
some atolls. Certain macrofauna located in the shallow areas
of the lagoon at Tarawa may have been organically enriched
from land-based anthropogenic sources (Kimmerer and
Walsh, 1981; Newell et al., 1996). Also, direct disposal
of raw sewerage into the sea has likely increased the seawater nutrient level causing bacterial contamination of
the lagoon seawater at Tarawa, but the lagoon ecosystem
has been flourishing as a result (Kelly, 1994).
On atolls such as those in the Marshall Islands, Funafuti
in Tuvalu and Tarawa in Kiribati increasing population
pressure has led to houses being built in inappropriate
locations, such as near active beaches and on low-lying
areas. In South Tarawa this has prompted the construction of coastal protection structures to avoid overtopping
during storms and high water events. There are a large
number of reclamations of varying designs and materials
built to expand the land area (Figure 9). Betio, Bairiki,
and Bikenibeu, the administrative centers of Kiribati, have
grown significantly compared to the comparatively pristine islands of Buariki and Abatao on the same atoll,
Atolls, Figure 7 Three atolls in Tuvalu, showing distribution of mangrove and Pemphis, and the degree that these environments
are impounded (after Woodroffe, 1988).
64
ATOLLS