Nano Gobies

are found on shallow-water tropical reefs, and most of
the unknown species are presumed to be in deep-water
habitats. In terms of higher-level taxonomic diversity,
far more types of corals are found in areas other than
tropical reefs. This richness in different coral varieties is
particularly evident in deeper waters, as has become increasing
apparent over the last decade or two. So far, over
3,300 species of stony corals alone have been recorded
from the deep sea.
It is worth remembering that the largest coral reef
in United States waters is in neither Hawai’i nor Florida
but in Alaska, off the south edge of the Aleutian arc, and
it is, for all intents and purposes, biologically unknown.
Very old Porites lobata on the Great Barrier Reef, Australia,
forming an intertidal ‘micro-atoll’ where its top has eroded.
But it is true that a few shallow-water temperate stony
corals are amongst the better known of all coral species.
In these cases, it appears easier to focus on the biological
attributes of a single coral species, if there are only one
or two species found in the region.
In the shallow waters of the west coast of North
America, the most common coral is the beautiful solitary
cup coral, Balanophyllia elegans. Large individuals reach
about an inch (2.5 cm) in diameter. Lacking zooxanthellae,
they are completely dependent on feeding for their
nutrition; as a result, small B. elegans polyps grow slowly.
In most areas they probably take about a decade, or a bit
more, to reach sexual maturity. After that their growth
rate slows as excess energy is put into gamete production
rather than growth. As with many tropical corals,
B. elegans broods its larvae. They are released from the
parent in the autumn or winter, when the planulae glide
like flatworms out of their mother’s mouth. Unlike most
tropical corals, these larvae only disperse about 4 inches
(10 cm) before metamorphosing into small polyps.
Native to the region from central California to south
central Alaska referred to as the Oregonian biome, arguably
the most ecologically dynamic temperate marine
area known, these small corals face a perilous existence.
The bottom is rife with predators, from crabs to snails
to flatworms, and although it might be theoretically
possible for any given individual to have a long life, the
odds of being eaten set an upper age limit for any B.
elegans population. In the southern
parts of the species’ range, a
few individuals from each year’s
spawning cohort will last to the
ripe old age of 40 years or so before
their number is up. In more
northern areas, it appears that
the hazards facing the polyps are
much more intense, and the longest-lived
individuals do not live
much beyond 10 to 11 years. Few
temperate shallow-water corals
have been investigated, but short
life spans appear to the rule: two
Mediterranean species, B. europaea
and Leptopsammia pruvoti,
have measured life spans within
the extremes known for B. elegans.
Being colonial rather than
solitary, and possibly living in
tropical rather than temperate
waters, may confer a survival advantage
on shallow-water stony
corals. That statement, however, has to be taken as a cautionary
note rather than as a dictum. Relatively few data
on the maximum ages of tropical reef stony corals are
available, and these are, almost without exception, from
massive species, such as Porites. As some of these Porites
colonies are the largest known coral colonies, the ages for
them are probably good approximations of the maximum
ages for tropical massive stony corals. Porites species are
found throughout the tropics and large individuals have
been commonly found, in both the Caribbean and Indo-
Pacific, to reach ages of about 300 to 400 years. Generally,
these are large individuals that have been “cored”
and their growth bands counted. A few exceptionally
large colonies of (presumably) Porites lutea have been
described from various parts of the Indo-Pacific. Based
on comparison with smaller colonies and using known
grow rates, these massive individuals are estimated to be
from about 350 to over 1,000 years old. These animals
are simply too large to reliably core, so estimated ages are
ED LOVEL/AIMS: HTTP://CORAL.AIMS.GOV.AU/
78 CORAL