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    Vernal Pools at Jockey’s Ridge

    By Ryan
    September 11, 2017

    From the road, Jockey’s Ridge is a huge sand dune, its peaks on a bright day almost painful to look at in their reflected light. From a distance there is no evidence of life, the glistening sandy slopes give the impression of a sterile desert.

    But the environment is not sterile – not at all – and this year with rain totals running 75% above normal at the park, a remarkable phenomenon is springing to life.

    Vernal Pool Jockeys RidgeDirectly across from the observation deck at the end of the boardwalk there is almost always standing water. Called a vernal pool, unlike pools or ponds that form after a hard rain, the source for a vernal pool is ground water being forced to the surface.

    Vernal pools that are found in a dune system are very dependent on rain for their existence. When there is very little rain, the groundwater sinks farther below the surface and the pool will either disappear or become a damp spot in the sand.

    When there are heavy rains, the pools will grow and expand, shrinking quickly, however as soon as a dry spell comes.

    Vernal Pool Jockeys Ridge 2But over a three month period with constant rain and totals that almost double the normal amount of precipitation, something marvelous happens.

    The pool itself has expanded. Where it was typically 10 yards across, it is now double that and even more is some places. Perhaps most remarkably, the pond has grown to a size only seen after hurricanes, but unlike the aftermath of a tropical system, the pond has not shrunk.

    Vernal Pool Jockey's RidgeFor anyone who has seen the water at the base of the dune, the sheer size of what we are witnessing now is astonishing. The pool has always been configured from north to south at the foot of a dune, but it now extends some 500 yards, then takes a 90 degree bend to the left at the base of a north facing fore dune to Jockey’s Ridge before ending about 100 yards from the Bypass.

    For anyone who has been hang gliding, that north facing dune is regularly used when there is a north wind, and there is now three feet of water in the landing zone.

    But the size and semi-permanence of the pond is not the only factor that makes this so fascinating. The vibrancy of life that it has triggered is astonishing.

    Jockey's Ridge west sideThere are grasses growing where bare sand existed last year. There are two possibilities to account for that. Certainly wind-borne seeds have found a home in this emerging ecosystem. Another possibility, and a fascinating one, is seeds have laid dormant for 10 or perhaps 15 years waiting for the right environmental factors to appear.

    Areas that are typically damp, forming the banks of the pond, have always had a denser growth. This year, though, the grasses are thicker and heavier than ever, and it looks as though some woody plants are trying to take root.

    On the north end of the pond, there is an emergent maritime forest. Sandwiched between a low dune to the east and a larger dune to the west, it is about a three acre plot of land and the process has been ongoing for some time. This year, however, with an abundant supply of water, the trees have lost the look of saplings, there is woody undergrowth and almost no grasses among the trees.

    The water has a distinctive red tinge to it. There are a few theories about why that is, although without testing, there is no way to be sure.

    Certainly a red algae could be in the water. Just to allay any fears, even if it is a red algae, it is not a red tide and it is very doubtful if it is toxic.

    Another possibility is that there is some iron content in the sand that has been transferred to the water.

    A option that a number of experts have pointed to is that the color of the water could be caused by tannins from ancient bogs that underly Jockey’s Ridge.

    Much of the Outer Banks rests on a peat bog. At one time the area that is now the vernal pool marked the western edge of the Outer Bank and was a maritime forest. Constant overwash and blowing sand killed the forest and it became a bog. As the ground water is forced through the bog, it would pick up the tannins that remain in the decayed trees.

    Animal life has also been abundant this year, although there have not been any new species spotted yet. However, Jockey’s Ridge Park Rangers have remarked on a bumper crop of frogs, noting that at times they have had to sweep frogs away from the doors just to get in the office.

    How long will this last? No one knows, but while it exists, and what it has created is an extraordinary testament to the beauty and complexity of barrier island life.