Divers began reporting dead fish and shellfish on the wrecks off of the Northern Coast of
New Jersey in June 1976. They also reported that the water was murkier than usual and a dark scum covered the wrecks. Water samples were taken and showed extremely low levels of oxygen in the bottom waters (hypoxia). The thick scum was tested and turned out to be the remainders of a thick bloom of algae. Soon fish kills were being reported as far south as Atlantic City. Three thousand square miles at the bottom of the ocean, from
Sandy Hook to Atlantic City, 60 ft off shore was either hypoxic (low oxygen) or anoxic
(no oxygen). Slow-moving organisms such as crabs, scallops, barnacles, starfish, worms and clams perished, along with territorial fish like eels and sea bass that were reluctant to leave the safety of the wrecks for areas with greater oxygen concentrations. The impacts to the fisheries due to New Jersey’s dead zone were disastrous and amounted to $430 million in losses. Commercial fish affected included the surf clam, bluefish, tuna, fluke, sea bass, and lobster.
Pictures of SCUBA divers, underwater wrecks, and murky water.
What caused the dead zone?
Oxygen reaches surface waters from the air and through photosynthesis of algae. The oxygen makes its way through the water column by the process of diffusion (molecules moving from an area of higher concentration to an area of lower concentration), wave action and currents. Because of differing densities, as the surface waters are warmed by the sunlight in the spring, two separate layers of ocean are created. The surface waters are warmer and the deeper ocean is colder. Between them is a thin zone where temperature decreases rapidly with depth called the thermocline. If you have ever dove straight into a lake you may have passed through the thermocline as you reached the deeper, colder waters. Because the bottom layer of colder water is much denser, the two layers resist mixing and so no new oxygen makes its way into the deeper waters. This means the oxygen that was trapped in the bottom layers must be sufficient to maintain the marine life through the summer. Usually there is enough oxygen to keep the marine life in the ocean depths alive through the summer, but in 1976 a large amount of algae died and sank to the bottom. As it decayed the oxygen was used up and carbon dioxide was released, which caused the hypoxic conditions experienced that summer.
A picture of the a thermocline, the coast of New Jersey, and a shot of the Jersey Beach.
Why in the summer of ’76?
Several conditions led to the dead zone in 1976. The temperatures were much warmer than usual, which resulted in the thermocline forming earlier. This meant the trapped oxygen had to last a few months longer. Secondly, river run off began two months earlier and this led to more nutrients being deposited into the bay. On top of all of this, there was significantly less storm action that spring and summer. Usually the storms break up algae blooms and mix up the water column bringing oxygen to the deeper water layers. All of

this meant the oxygen in the ocean depths had to last the marine life two additional months. This was impossible with the decaying of a massive algae bloom exhausting the oxygen supply.
New Jersey’s commercial and recreational fishing industries as well as its ocean based tourism are all dependent on the health of the coastal waters. No one is sure if the conditions that lead to the dead zone in 1976 could happen again, and for this reason the water condition must be closely monitored. Determining and monitoring the factors that cause dead zones is the only way to safeguard the marine life that live off of the coast of
New Jersey.
Pictures of the Hudson River running into the bay, the dead zone off of New Jersey, and organisms like the Surf Clam that were affected by the dead zone.
1.
The dead zone in the summer of 1976 went from ______________________ in the north to ___________________________ in southern New Jersey.
2.
The thin zone in the ocean where temperature decreases rapidly with depth is: a.
The dead zone b.
An algae bloom c.
The thermocline d.
Hypoxic
3.
The reason the ocean separates into two layers is because of: a.
The different densities b.
Extra nutrients from river run off c.
The different temperatures d.
An algae bloom e.
A and C
4.
All of the following are reasons why the dead zone occurred in 1976 EXCEPT: a.
Temperatures were warmer earlier that year b.
Too many fish using up oxygen c.
River run off began two months earlier d.
Less storms than usual
5. (T / F ) The condition of no oxygen in the water is known as hypoxic.