AD 2015 Q4

LOCAL DIVING
CAPE COD
Clockwise from top left: A common snapping turtle, an apex predator in ponds and lakes; Cape
Cod’s reefs are home to myriad small fish such as this sea robin; more than 3,000 shipwrecks
are found around the cape; a graceful blue shark, one of the fastest sharks in the sea
young summer flounder glides across the sand searching
for small fish or crustaceans on which to feed. Schools
of small mummichog and translucent silversides dart
through a jungle of grass blades, avoiding deeper waters
where predatory bluefish and striped bass patrol.
Not far from the protected bays, the open ocean is
alive with movement. It swells and subsides, endlessly
rolling and rocking according to earthly, solar and
lunar rhythms. Microscopic, one-celled diatoms and
other phytoplankton invisible to the naked eye make
these pelagic waters so fertile. The shallow photic zone
of the North Atlantic is like a colossal farm, producing
immeasurable quantities of phytoplankton. Stellwagen
Bank and Georges Bank, where nutrient-rich waters
blend with sunlight, are especially productive due to
deepwater upwelling. The abundant plankton feeds
larval crustaceans, mollusks and fish such as sand
lances, which in turn attract larger predators.
MAMMALS
Some of the most extraordinary and rare mammals on
Earth feed and raise young here. Humpback, fin, minke
and North Atlantic right whales may travel thousands of
miles to be off the cape during the spring and summer.
Once there, they strain enormous quantities of plankton
through their baleen, fattening themselves for their
long migrations to distant breeding grounds where they
spend the winter. In near-shore ocean waters, thousands
of harbor and gray seals prosper. Their breeding
colonies have grown rapidly in the past 43 years because
of the Marine Mammal Protection Act of 1972, which
made it illegal to hunt, kill, capture or harass any marine
mammal in U.S. waters (with limited exceptions).
SHARKS
The return of seal populations has signaled another
stirring comeback: that of the great white shark, one
of the food web’s supreme carnivores. The stuff of
legends and nightmares, white sharks appear during
summer months to feed on the fat-rich meat of the
abundant pinnipeds. Researchers have satellite-tagged
more than 50 white sharks off the cape in the past few
years to learn where they were coming from and where
they went in the fall. It appears that the majority of
these sharks migrate along the East Coast, following
the continental shelf from Cape Cod in the summer
and fall to an area between South Carolina and Florida
for winter and spring. It is thought that larger, more
mature white sharks probably exhibit different migratory
behaviors and head for far-off breeding grounds.
A variety of other elasmobranchs — including skates,
torpedo rays, pesky dogfish, gigantic basking sharks,
speedy makos, toothy sand tigers and others — inhabit
Cape Cod’s cold waters. But arguably the most aesthetic
species found offshore is the blue shark. These sleek
and charismatic oceanic marauders prefer the edge of
38 | FALL 2015