Pine Barrens Surface Water
by Dr. Ruth Patrick
Many people over the years have enjoyed the beauty of the Pine Barrens streams. One has only to go by canoe through the black waters bordered by cedar swamps and open pinelands, to become enchanted by their uniqueness. However, few people realize that these are truly unique streams containing a very unusual fauna and flora. They are confined largely to the coastal plains of the United States, and are commonly called "Blackwater Streams".
The substrate through which they flow is sand and gravel, commonly referred to as an unconsolidated substrate. Underlying most of these streams is the large Cohansey Formation, which is a great underground aquifer of water. Its area is about 2,000 square miles, and it is estimated to reach a depth of 37 feet in some places. This formation is seldom more than 20 feet below the surface, and as a result, it greatly influences the surface waters. In the summer these streams are relatively cool, generally being below 25 C, and in winter they rarely freeze.
White cedar swamps, sphagnum, and cranberry bogs drain into the stream channels of these river basins. Scattered through the river systems are lakes formed by man's damming of the streams.
The black or brown water color is caused by large amounts of humates arising from the drainage of the swamp's vegetation. These streams are very acid - the pH varies from about 3.6 to 5.2 with a mean around 4.4. Typically, they also have very low amounts of alkaline metals and the oxygen content is usually lower than in a circumneutral stream. However, if these streams receive pollution resulting from sanitary wastes and farming wastes, from fertilizers applied to cranberry bogs and stands of blueberries, and from other types of agricultural activities, these characteristics may be considerably altered. The usual effects of such pollutants are to raise the pH and increase the organic load, the nitrates and the phosphates in the water.
Another characteristic of these streams is an orange to yellowish- brown flocculant material often seen near the banks, particularly in slow-f lowing water. This is iron oxide formed by bacteria such as Leptothrix ochracea. It is this bacterium, and others that are similar, that oxidizes the iron present in the water and causes these large orange to brown colored f locs. This oxidation is believed to be involved in the formation of "Bog Iron".
Because these streams are typically very acid, are low in alkaline metals, and contain considerable amounts of iron, they have a unique fauna and flora (though they may include some more tolerant species). For example, one finds few freshwater clams and snails in these waters because they require calcium to form their shells. Crustacea are typically scarce in waters with a pH below 6. Many fishes, such as bluegills, yellow perch, golden shiner and calico bass do not reproduce in water with a very low pH. The pickerel is one fish that seems to reproduce and be successful under these acid-water conditions.
Vertebrates characteristic of, or confined to, these acid streams are the frogs, Rana virgatipes and Hyla andersonii, and such fish as the mud sunfish, the banded sunfish and the chub sucker.
The algal flora of these streams is also greatly altered. One typically finds many desmids (desmids differ from diatoms in lacking a siliceous skeleton) present in them. The main diatom genera are Eunotia, Pinnularia and Frustulia. The other characteristic algae of Pine Barrens streams are some of the green algae, particularly Zygnema and Mougeotia, and the red alga Batrachospermum. This red alga typically occurs in the spring of the year. Although it is classed as a red alga, its color in these streams is a bluish-green.
When pollution such as that from fertilized cranberry bogs enters these streams, the flora and fauna change considerably, the pH is raised, as noted above, and the nutrients increase. The first effect of such increased nutrients is to produce large populations of the characteristic species. Thus, we often find large amounts of the diatom genus Eunotia present, and the populations of the red alga Batrachospermum increase greatly.
These streams have not only aesthetic beauty, but, as we can see from the above discussion, a unique fauna and flora correlated with the high humates and iron, low pH and meager content of alkaline metals. Any alteration of these black water streams would probably eliminate many of these characteristic Pine Barrens species.
Permission to reprint this article which appeared in the Winter 1978 edition of Frontiers magazine was granted by the Academy of Natural Sciences of Philadelphia.