If you’re planning that oncein-
a-lifetime dive trip, you might
ask, “Have I really thought of
everything?” Did you remember
the little boy? The Christ Child?
In Spanish, El Niño. Because if
you don’t understand what this
“little” fellow can do to your
search for schools of hammerheads
and other big critters, you
might be in for one substantial,
and expensive, disappointment.
Fishermen along the coast of
Peru coined the phrase “El Niño”
in the late 1800s. Around
Christmas, they often caught
fewer fish. They didn’t know why
then, but scientists later learned
that the culprit was the seasonal
invasion of a warm southward
ocean current that displaced the
north-flowing cold current in
which the Peruvians normally
fished. Although Peru is among
the most severely affected areas,
the undersea impact of an El
Niño can extend from the
Galapagos north to Costa Rica’s
Cocos Island and as far as the
Indian Ocean, the Maldives, and
beyond. Its effects can spell a big
letdown for divers.
Under normal circumstances,
the rich and interdependent eastern
Pacific marine food web is
well nourished by the continual
upward surging of cooler water.
Flush with plankton, this
upwelling is the mother of oceanic
meals. However, when the nutrientrich
waters are forced deep, there
is big trouble.
Normally, ocean water heated
by the tropical sun is pushed by
trade winds to the western Pacific.
The warm water then piles up
around Indonesia and other
regions west of the International
Date Line. From time to time (the
reasons why aren’t clear) the trade
winds weaken and this water slides
eastward across the Pacific to South
America. When the warm water
reaches the South American coast
near Peru, it spreads far north and
south, along the coast.
When this “big slosh” occurs, the fish are forced to either feed
deeper or leave the warmer
water, returning only when the
water cools again. Dependent
invertebrates, like hard and soft
corals, sea anemones, giant
clams, and zooxanthellae (the
symbiotic algae that give the
coral its color) are not so lucky.
As they cannot move away from
the warmer water, they must
either weather El Niño or perish.
Corals, with their narrow temperature
tolerance, seem to be the
most vulnerable of all.
Since the late 1950s, there
have been seven major El Niño
events. They have occurred as
often as every two years, although
an interval of four to five years is
the norm. Expected to last about
eight to ten months on average,
they have lingered as long as
eighteen years. Popular
Eastern Pacific dive venues
hard hit by the last El Niño,
which spanned 1997 to
1998, include Cocos Island
and the Galapagos, though
the warm currents extended
up the coast as far as
California. According to the
Australian Institute of Marine
Science, that last El Niño significantly
affected sea life in
Australia, Thailand, the Maldives,
and Indonesia. Even the
Caribbean, particularly the
Bahamas, Belize, and the
Cayman Islands, experienced
some coral bleaching.
Now, scientists believe that El
Niño is returning. To show what
effect this might have, we turned
to the Undercurrent archives for
divers’ reports from the critical
areas.
We found that in non-El Niño
seasons nearly all divers visiting
the Galapagos commented on
the outstanding pelagic life, particularly
the abundance of hammerhead sharks. For example,
Joseph Pomento (Redondo
Beach, CA) remarked that in June 1995 he saw “Mantas every
dive, schools of hammerheads
too numerous to count,
squadrons of spotted eagle rays
flying across the reef . . .“
Divers in 1996 continued to
rave about sharks. In November,
Bob Viggers (Seattle, WA) reported
“Diving mostly packed with
lots of fish and sharks, [thousands]
of hammerheads on each
dive at Darwin and Wolf Islands.”
But from the middle through
the end of 1997, divers pointedly
noted the effects of El Niño. For
example, in May 1997, David
Stoll (NYC) found that “Water
temperatures at times exceeded
80 degrees, including Darw i n
Island, where the schooling hamm
e rheads are supposed to be.
Lucky to see two or three in the
distance.” During a January 1998
trip, John Walker (Tampa, FL)
noted, “Because of El Niño, water
was 82 degrees . . . some wildlife
may have moved to colder water,
there was enough to satisfy me.
Saw hammerheads, but only
deep and far away.” However, by
midyear, water temperatures had
cooled. On a July 1998 trip, Dr.
Zygmunt Dembek (Suffield, CT)
found the water ranging from
sixty to seventy-eight degrees,
depending upon thermoclines.
“Huge schools of hammerheads
are back at easy diving levels.”
The remarkable schools of
hammerheads and Galapagos
sharks were out of range,
disappointing many divers. |
The same was true for the
Cocos Islands. In September
1997, Peter Hartlowe said, “most
hammerheads at 120-140 feet . . .
tough to shoot that deep and
dark.” The following January, Ray
Pettigrew (Napa, CA) said, “being
an El Niño year, the sharks were at
200 feet.”
Nevertheless, in both areas divers
reported seeing plenty of mantas,
large schools of fish, rays, and other
sharks; it was just that the remarkable
schools of hammerheads and
Galapagos sharks were out of range,
disappointing many.
Lacking the mobility of the
sharks, the corals of the central and
western Pacific and Indian Oceans
suffered mightily, and bleached
coral still remains in the waters of
Micronesia, especially off Palau.
The Maldives were renowned for
splendid corals. However, the last El
Niño affected them greatly. In
November 1998, Max Herndon
(Pismo Beach, CA) found that “El
Niño currents warmed the water to
92 degrees Fahrenheit and
that killed much of the hard
coral. Reefs that on previous
trips that were a kaleidoscope
of color are now disappointingly
gray.” This devastation
carried over well into 2000,
when on a May trip Gwen
Hyatt (Houston, TX) “. . .
really noticed coral bleaching
of reefs.”
In fact, only recently have the
hard corals started to recover significantly. Karen Uyeda (San Jose, CA)
remarked that on her trip last
August, “The coral is still very damaged,
but is recovering in many
areas. The soft corals are doing
well.” Palau was also seriously hit. El
Niño nearly wiped out the jellyfish
in Jellyfish Lake, but they have since
returned, although in smaller numbers.
NOAA scientists are now reporting
that below-normal sea surface
temperatures in the central equatorial
Pacific off South America have
given way to above-normal readings.
Ocean temperatures increased
more than four degrees Fahrenheit
in February. The head of NOAA,
Admiral Conrad Lautenbacher, says that an El Niño will almost certainly
arrive by summer. Some
researchers believe it will last well
into 2003. However, it is still too
soon to predict its persistence
with any certainty. One
Singapore meteorological center
has also reported the gradual
warming of surface temperatures
in the Pacific and predicts the
onset of a weak to moderate El
Niño episode later in the year.
As you plan your dive trips, follow
these climatological developments
carefully and choose your
destinations with prudence. El
Niño status is updated monthly at
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/
enso_advisory/
----Doc Vikingo