#eutrophication

Sand tiger sharks, or carcharias taurus, are a species of sharks that can be found all along the Atlantic, Pacific, and Indian Ocean coastlines. They also can be found in estuaries, reefs, or shallow bays. More locally, these sharks can be seen in the Great South Bay, the Long Island Sound, and all along the south shore. Sand tiger sharks tend to stay within warm, temperate waters, salt or freshwater. Their diet changes with their growth, and it depends on the type of water and really what is available, since sand tigers are opportunistic hunters. However, pretty commonly, their diet ranges from your average bony fish to crustaceans, or even to other smaller sharks/rays and squids.

Now, for a quick biology lesson. In most shark species, you can expect a litter of pups to be among the larger numbers of offspring. Sandbar sharks, another species of shark in the sound, have any number around 6-12 pups, while great whites can range from 2-14 pups. Nurse sharks, though they are not native to Long Island waters, have an average of 20-30 pups per litter. This is not the same case for sand tiger sharks.

Although female sand tiger sharks can have up to 25 embryos in one of their two uterine horns at a time, the ovoviviparous (meaning the embryos begin as eggs and hatch within the womb before birth) embryos perform a specific (and special) type of cannibalism (intrauterine cannibalism [cannibalism within the womb] or oophagy [egg eating]) where after one embryo reaches 10 cm, it will begin consuming the rest of the embryos within the uterine horn, leaving a maximum of 2 pups to be able to be born at a time. Gestation for the embryos lasts 8-12 months, giving this shark species a maximum of 2 pups to be born every 2 - 3 years.

Why does mentioning all of this matter, you may ask?

Everything concerning their diet, their biology, and their habitats are what is leading to the endangerment of sand tiger sharks.

Currently, the major issues that are endangered this species lie in overfishing and in habitat degradation. Overfishing, in this context, refers to the overfishing of the sand tigers diet rather than of the sand tigers themselves, since all endangered animals are protected in the United States under the Endangered Species Act. This article is going to focus on the habitat degradation portion of the endangerment, as overfishing sort of explains itself - overfishing of smaller animals on lower trophic levels = less food for bigger animals on higher trophic levels, leading to an increase of competition and a drop of populations that rely on those prey. The habitat degradation that is mentioned is a bit more specific than that.

Most commonly on Long Island, habitat degradation of estuaries and other bodies of water occur through runoff - the movement of water that does not get infiltrated back into the earth over land after some sort of rainfall. This runoff, on it's way to sea level, picks up soil, sediments, and anything that can be very easily transported, especially fertilizer and animal waste. When reaching the nearest body of water, this runoff with everything in it can increase turbidity (cloudiness of the water), which inhibits sunlight from reaching underwater plants, increase water pollution, and can cause eutrophication. 

Eutrophication is the effect of an increase of nutrients, such as nitrogen and phosphorus, which that increase leads to the build up of other organisms - usually algae in the form of algae blooms - that deplete the oxygen from the water that the usual organisms in that space need. Eutrophication is the creation of dead zones within the water from these blooms, which kills and prevents species from living in certain areas of the water.

It's a sort of snowball effect. Algae bloom causes a dead zone, plants die first since they can’t move to and from areas, which prevents a lower trophic level organism, like plankton, from getting food and therefore dropping in population amount, and the same can be said for the rest of the populations that hunt in that now dead zone. 

So what can be done?

With overfishing, it's the same sort of thing that people have been advocating for for years. Promoting more aquaculture (though not completely to overtake wild fish catching, since they both have their issues) can help popularly fished prey regain some numbers. Even just calling for catch and quota limits to be put out helps.

With runoff pollution, there’s a lot that people can individually do. Lowering fertilizer use, as fertilizer holds a lot of nutrients, and gets carried away fairly easily, can help lower the amount of dead zones. Even making sure that all animal waste you can see, be it from a pet or from livestock, is properly disposed of can help out tremendously.

The issue with runoff eroding soil and dragging it to bodies of water can also be helped, though not completely solved. Planting plants that have deep root systems can help to increase soil structure, lowering erosion of top soil, and sucks up nutrients left behind on the surface that would otherwise be carried away. In good news, just this last November, the Long Island South Shore Estuary Reserve has been said to be receiving a 2.4 million dollar boost in funding that will be going to many different conservation projects across Long Island, like to Oyster Bay to plant dune grass on beaches to protect against shoreline erosion.