[Coral-List] FIELD OF GIANTS

[Charles Birkeland]

FIELD OF THE GIANTS

Findings on the GBR usually get a lot of notice. For example, the
description in a recent Nature Scientific Reports (online 19 August 2021)
of the largest massive *Porites* colony on the GBR (5.3 m high, 10.4 m
wide, 31 m in circumference and between 421 and 438 years old) received a
lot of attention. A few months earlier (same journal, online 7 December
2020), a similar article (I was *not* an author) described a scattered
group of seven very large massive *Porites* cf. *lutea* at the island of
Ta’u, American Samoa (the two largest were 8 and 7 m high, 22.4 m wide
(over twice the diameter of the GBR specimen) and 17 m wide (diameter),
circumference 69.4 and 41.0, and I heard that growth rings from a core
indicated the second largest one to be 540 years old), but this article was
hardly noticed. If we assume the *Porites* colonies were hemispherical,
which I believe is quite reasonable, then the volume of the GBR colony 2πr3/3
is 294 m3. The volumes of the two largest in the Field of the Giants were
1286 and 2942 m3, or were 4.4 and 10 times the mass of the largest on the
GBR. For surface area, 2πr2, the areas of the *Porites* colonies were 170 m2
(GBR) and 454 and 788 m2 for the two at Ta’u. The two at Ta’u were 2.7 and
4.6 times the area of the largest on the GBR. Twice the diameter is not
particularly impressive, but this indicates 4.6 times the surface area and
10 times the mass. American Samoa is thought of as a tough and challenging
environment for corals with major crown-of-thorns outbreaks, numerous
cyclones, mass bleaching events, occasional extreme low tides, a tsunami,
and with sea level rising five times as fast as the global average because
the islands are sinking relatively (geologically) fast (Han et al. 2019 JGR
Solid Earth 124: 4142-4156). Despite these harsh conditions and frequent
damage to coral communities, the corals of American Samoa are remarkably
resilient and the dynamic system deserves attention. It is good to keep a
log of all massive *Porites *colonies greater than 10 m in diameter, and
around the world, there are probably a number of colonies larger than the
22.4 m diameter colony at Ta’u; but no matter how many are larger, the
Field of the Giants is still a marvelous sight in American Samoa.