Thursday, October 14, 2010

Whales Doing Their Part to Recycle

Today it seems that the environment can only be counteracted by us humans but a recent study in the Gulf of Maine by Joe Roman and James J. McCarthy shows that whales are helping the cause. In their journal, “The Whale Pump: Marine Mammals Enhance Primary Productivity in a Coastal Basin”, they state that whales and other large aquatic mammal life are replenishing nitrogen levels by the way of feces and aquatic wastes. It is called a “pump” and the feces surfaces on top of the water and nitrogen is evaporated into the air. Most aquatic life like fish can stay under water all the time so their waste is found deeper in water and eventually makes its way to the ocean floor. Whales excrete their wastes near the surface of the water because they hover around the top for breathing purposes. Also some of their food live closer to the surface. The nitrogen from these plumes improves atmospheric air by replenishing 23,000 metric tons of nitrogen per year in the Gulf of Maine alone. Whale feces tend to float because nitrogen is very buoyant. Cetaceans such as whales bring nutrients from waste to the top and the wastes disperse.

Roman and McCarthy collected sixteen plume samples during two trips. Humpback plume samples of NH4 were from 0.4 to 55.5 ┬Ámol kg -1 near the surface. All samples away from top layer plumes were less than 1 ┬Ámol kg -1. The high level plumes consisted of phytoplankton and microbes able to utilize NH4. None of these samples were greatly affected by the plankton consumption so it concludes that most of the nitrogen excreted still forms at the top of the ocean. There is a strong benefit for the whales because plankton and fish are attracted to the feces so the whales ingest more dense groups of food leaving higher concentrations of nitrogen at the surface.

These whale pumps are most common in the spring and summer. Analysis the whale pump can also help determine the wellness of the whale’s diet. Whales like to bottom feed at night because sand lance are in hidden areas. But during the day, whales prefer to be as close to the surface as possible, the average dive depth is around 113-130m during the highest consumption hours.

Whales are not the only sea mammals that excrete large amounts of Nitrogen waste. Other water mammals such as Pinnipeds and seals excrete about 87% of their nitrogen intake. Around 3% of that is evaporated into the atmosphere. Many oxygen breathing mammals in the ocean contribute to the replenishment of nitrogen levels. Whales also recycle iron back into the atmosphere through feces.

Without nitrogen replenishment, humans and other air breathing organisms would not exist. Air we breathe consists of 78% nitrogen. Nitrogen also makes the sky blue from sun rays. Whales may play a small part in the entire nitrogen cycle but they are vital in the total nitrogen production from our oceans. They are similar to a small nitrogen factory. They search for food when they have to then they can attract most of their prey by their feces while at the same time the feces are being evaporated back into the nitrogen cycle.

Although samples were only collected in the Gulf of Maine, it gives a good representation of the importance of whales in the ecosystem. We should be mindful of whale hunting that is decreasing group populations all over the world. Before commercial hunting of whales started, whale excretion of nitrogen was extremely greater than it is today due to larger numbers. We cannot afford to lose such a species that has proved to be so helpful in replenishing an environmental cycle. Is it morally right to kill whales for financial gain or do mammals like these deserve a part in helping nature as well?


Reference

Joe Roman, James J. McCarthy. “The Whale Pump: Marine Mammals Enhance Primary Productivity in a Coastal Basin”. PLoS ONE, 2010; 5 (10): e13255.

Journal Link: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0013255

By: Peter Bishop

ID: 0718896

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