398
Destruction and Recovery of Reef Systems, Reef and Man
observers of the Acanthaster phenomenon (Goreau 1963). Therefore, such
reefs permanently inhibited by Acanthaster would have a tendency toward
gradual destruction. Even if repeated attacks stop, a reef once damaged by
Acanthaster could completely recover only after 20-40 years (Endean and
Cameron 1985).
The actual cause of recent Acanthaster outbreaks on reefs of the IndoPacific is still disputed (Eann, 1990). Existing hypotheses are based mainly
on two controversial postulates: (1) the outbreaks are a natural periodical
phenomenon and happened also in the past (Walsh et al. 1971; Dana et al.
1972; Vine 1973), and (2) they are a unique biological phenomenon, the
ecocatastrophe, which did not happen before, being in some manner
triggered by increased human activity in reef regions (Kuhlmann 1971;
Randall 1972; Endean 1973, 1974, 1977; Cameron 1977; Cameron and
Endean 1985). The followers of the first opinion have serious arguments of
their own but, the latter position seems to be more reasonable. (It coincides
also with the author's own observations.) In fact, in abundant literature on
the reef bottom fauna, describing results of more than a century of
observations in various areas of the Indo-Pacific, no mention was made of
such catastrophic infestations of reefs by this star. Through the whole period
before 1960 A. planci had been described as a rare species of sea stars. R.
Endean (1973) stated that such allusious were absent also in the mythology
of island aborigines. Cases of the presence of skeletal remains of
Acanthaster in ancient reef rocks (Frankel 1977; Walbran et al. 1989) could
not be accepted as proof of past outbreaks because of the ability of these
stars to form aggregations in their breeding period, while still remaining a
rare species. Also, quite reasonable is the remark that the ecosystems of
Holocene reefs could not exist at all had it been periodically subjected to
catastrophic damage by Acanthaster invasions, as happened in 1960-1970,
which, as we have seen above, have a tendency to become chronic.
As for this author's own experience, during 2 weeks of swimming among
reefs off Tahiti in 1961 he did not meet with a single Acanthaster. But in
1968, when large construction works started there in the lagoon of the
Barrier Reef, in connection with future nuclear tests at Moruroa, during 1 h
of swimming he came upon 2-3 stars, which were devouring corals in the
daytime. As it was pointed out above, this transfer from nocturnal to
daytime habit is a sign of future outbreak of invasion by this star. In 1984
this author witnessed a heavy invasion on the reefs near the Hon Gom
Peninsula along the coast of central Vietnam. The reefs in this area were
severely stressed during the war (bombing) and after (lime excavation,
explosives fishery). In accordance with the author's observations, in 1981 the
stars were practically absent there, but in 1984 their invasions at some reefs
were terrific. Reefs were literally eaten up. Their density in many places was
up to one per 1 m- 2 . These observations seem to be evidencing, that the
outbreaks in the above-mentioned sites were triggered by the destabilization
of the reef communities there by man (Chesher 1969; Fishar 1969). This
Destruction and Recovery of Reef Systems, Reef and Man
observers of the Acanthaster phenomenon (Goreau 1963). Therefore, such
reefs permanently inhibited by Acanthaster would have a tendency toward
gradual destruction. Even if repeated attacks stop, a reef once damaged by
Acanthaster could completely recover only after 20-40 years (Endean and
Cameron 1985).
The actual cause of recent Acanthaster outbreaks on reefs of the IndoPacific is still disputed (Eann, 1990). Existing hypotheses are based mainly
on two controversial postulates: (1) the outbreaks are a natural periodical
phenomenon and happened also in the past (Walsh et al. 1971; Dana et al.
1972; Vine 1973), and (2) they are a unique biological phenomenon, the
ecocatastrophe, which did not happen before, being in some manner
triggered by increased human activity in reef regions (Kuhlmann 1971;
Randall 1972; Endean 1973, 1974, 1977; Cameron 1977; Cameron and
Endean 1985). The followers of the first opinion have serious arguments of
their own but, the latter position seems to be more reasonable. (It coincides
also with the author's own observations.) In fact, in abundant literature on
the reef bottom fauna, describing results of more than a century of
observations in various areas of the Indo-Pacific, no mention was made of
such catastrophic infestations of reefs by this star. Through the whole period
before 1960 A. planci had been described as a rare species of sea stars. R.
Endean (1973) stated that such allusious were absent also in the mythology
of island aborigines. Cases of the presence of skeletal remains of
Acanthaster in ancient reef rocks (Frankel 1977; Walbran et al. 1989) could
not be accepted as proof of past outbreaks because of the ability of these
stars to form aggregations in their breeding period, while still remaining a
rare species. Also, quite reasonable is the remark that the ecosystems of
Holocene reefs could not exist at all had it been periodically subjected to
catastrophic damage by Acanthaster invasions, as happened in 1960-1970,
which, as we have seen above, have a tendency to become chronic.
As for this author's own experience, during 2 weeks of swimming among
reefs off Tahiti in 1961 he did not meet with a single Acanthaster. But in
1968, when large construction works started there in the lagoon of the
Barrier Reef, in connection with future nuclear tests at Moruroa, during 1 h
of swimming he came upon 2-3 stars, which were devouring corals in the
daytime. As it was pointed out above, this transfer from nocturnal to
daytime habit is a sign of future outbreak of invasion by this star. In 1984
this author witnessed a heavy invasion on the reefs near the Hon Gom
Peninsula along the coast of central Vietnam. The reefs in this area were
severely stressed during the war (bombing) and after (lime excavation,
explosives fishery). In accordance with the author's observations, in 1981 the
stars were practically absent there, but in 1984 their invasions at some reefs
were terrific. Reefs were literally eaten up. Their density in many places was
up to one per 1 m- 2 . These observations seem to be evidencing, that the
outbreaks in the above-mentioned sites were triggered by the destabilization
of the reef communities there by man (Chesher 1969; Fishar 1969). This