19 Feb 2015
Poop In The Ocean: Who, Me?
I can still hear my high school friend Don telling me, ‘Gay kocken offen yam!’—a colorful Yiddish phrasethat translates as ‘Go poop in the ocean,’ meaning roughly, ‘Get outta here, that’s ridiculous!’ The phrase has resonance, since there’s lots of ocean pooping by countless ocean-dwelling animals and —regrettably— by the 60% of us living close to the coast. We’ll begin with marine systems where poop is a welcome source of nutrients and food.
Smells Like Poop
Let’s start at the moist black nose of a Rottweiler dog named Fargo, who is trained to smell right whale poop and can point researchers from the New England Aquarium toward it from two miles away.
With a net the researchers snare a sample of the gloppy cloud of reddish or brownish material that captured Fargo’s attention, analyzing it later in the laboratory to measure reproductive and adrenal steroid hormones ("stress" hormones). Among other things, the tests can tell whether a whale is sexually mature and if a female is pregnant or nursing.
Whale poop provides information useful for managing endangered right whales, orcas (also see here) and others, but it also does something perhaps even more important, beginning in the ocean’s sunny surface waters. It helps fertilize the entire pelagic food web. In the ocean, as on land, plants anchor the food web. In shallow water where light is abundant, plants such as mangroves, seagrasses, salt marshes and large seaweeds (kelps, rockweeds etc.) thrive, but in deeper water plants must float to stay in the sunlit zone, so the food web begins with tiny single-celled algae (phytoplankton) kept aloft by oil droplets, flagellae and spiny hairs to slow their sinking. (The only large plant able to float is the rockweed Sargassum spp. which normally lives attached to rocks and whose fronds are buoyed by gas bladders. Fragments dislodged or broken by storm waves float, grow, and accumulate into large mats in the Sargasso Sea that host a diverse and unique biological community.)
Using the sun’s energy and nitrogen, phosphorus, iron and other nutrients in the water, phytoplankton multiply rapidly, forming the base of all major marine ecosystems, feeding countless marine larvae, copepods, krill, shrimps, mussels, clams, scallops, anchovies and other grazing fish —and everything that eats them.
Looks Like Snow
Billions of fecal pellets from the animals, plus molted exoskeletons and dead organisms gently sink. If the water is not too deep, some fecal pellets reach the bottom nearly intact, where worms, sea cucumbers and other bottom dwellers probably eat those with highest content of carbon and nitrogen. As the downward journey continues, bacteria slowly decompose the material, creating sticky mucus that binds particles together into flakes. Marine explorer William Beebe saw the particles from the window of the Bathysphere during his first dive off Bermuda in 1930 and described them as ‘marine snow’. Later, Rachel Carson wrote in The Sea Around Us (1951), “When I think of the floor of the deep sea…I see always the steady, unremitting, downward drift of materials from above, flake upon flake, layer upon layer…the most stupendous “snowfall” the earth has ever seen.”
This oceanwide ‘snowfall’ is also called the ‘biological pump’ because it is the primary way food reaches deep water animals and seafloor communities. But it creates a big potential problem as rapidly growing plankton plants deplete available nutrients and their potential sources of replenishment--the nutrients in marine snow--sink below the sunlit zone. What keeps the system going? The problem is less pressing near shore, where runoff from land brings nutrients from eroded soil, decaying plants and animals and fertilizers used in agriculture as well as discharge from sewers and sewage treatment plants (more on this later). Furthermore, in shallow water it is easier for winds and currents to mix nutrient-rich water upward into the sunlit zone. But offshore, nutrients are often in short supply, relieved only by upwelling where currents diverge, nitrogen fixed by bacteria or deposited from the atmosphere and windblown dust blown from land. Only very strong storm winds can stir the cool, dense, nutrient-rich water up into the warmer surface layer.
Whale Poop to the Rescue
This big problem may have a big answer: whale poop. Whales often feed well below the sunlit zone where plant plankton grow. Sperm whales and beaked whales may dive a mile or more to hunt squids and fish. Whales and other deep divers, such as elephant seals and Weddell seals deliver nutrients to the plants by feeding at depth, but frequently pooping near the surface. Joe Roman and James McCarthy named this process the ‘whale pump.’
In the Gulf of Maine, whale and seal poop probably made 23,600 metric tons of nitrogen per year available to plant plankton, more than the input of all rivers combined and approximately the same as input from the land, but less than the amount deposited from the atmosphere.
Whale poop may be critically important in another way in Antarctica, where lack of iron in the surface waters limits phytoplankton growth. Krill eat the phytoplankton, accumulate iron from the minute plants and store the iron in their bodies, retaining nearly one-quarter of all the iron in the sunlit zone. Everything in the Antarctic eats krill and whales are the major consumers. Each whale eats up to several tons of krill per day, but the whales excrete most of the iron in their poop, which contains roughly 10 million times the concentration of iron as in the surrounding water. By making iron available, whales and probably other poopers like seals, sea lions and marine birds fertilize the life of the whole ecosystem. The Gulf of Maine and Antarctic studies suggest that fertilization of primary production by the whale pump or by recycling iron was even more important before hunting decreased whale populations and before industrial-age air pollution delivered large amounts of atmospheric nitrogen.
Now the Bad News: People Poop
Population trends for whales and people have gone in opposite directions during recent centuries, causing the ocean to see a lot less whale poop and a whole lot more people poop. As one example, numbers of blue whales in the Southern Hemisphere have declined by 99% during the last century, from approximately 327,000 (298,000-359,000) to 1,180 (885-1,490).
At the same time, the
human population has skyrocketed from 1.6 billion in 1900 to more than 7
billion and is expected to reach 9 billion by 2050.
Why is People Poop A Problem?
Poop smells and can transmit disease either by direct contact or through pollution of water supplies. Among other fecal-borne diseases are gastroenteritis, typhoid, paratyphoid, salmonella, cholera, meningitis, hepatitis, encephalitis, dysentery, amoebic dysentery, giardia and parasites such as roundworms. For most of human history our communities were so small that poop was mainly a nuisance, at times spreading disease or parasites locally, but also providing a benefit as a fertilizer for crops. As communities grew, so did filth, odor and disease. More poop entered wells, lakes, streams and rivers, affecting the environment as well as human health. During the last century population growth far outstripped effective treatment of wastes.
Increased coastal migration and rapid urbanization are compounding the pressure on coastal marine habitats. As one example, Boston, Massachusetts, did not begin to build a sewer system until 1877. That system, completed in 1884, collected sewage from 18 cities and towns, piped it to Moon Island in Boston Harbor for released on every outgoing tide! The first plant to treat the sewage was built in 1952, but raw sewage was released until 1997, and dumping of sewage sludge into Boston Harbor only ceased in 1995. Normally millions of gallons per day of secondary-treated waste water (see below) are discharged into the harbor. However, like most ‘old’ cities, Boston has a ‘combined’ sewer system that gathers both sewage and rainwater. Sewer flow overwhelms treatment plants when rainfall exceeds about one-half inch (13 mm). When that happens, the combined flow bypasses treatment plants and is to this day released untreated into the harbor from several dozen outlets. The story is similar, or worse, in cities worldwide, especially those that are larger and older than Boston.
How Much People Poop Is There?
Calculating the global amount of people poop is difficult. Individuals make different amounts depending on their sex, body size, diets, frequency of bowel movements, states of health and other factors. Most studies estimate daily output to be 3 to 8 ounces, with higher amounts where people eat lots of fiber. Poop contains 50% to 75% water and the remaining material is about 30% bacteria, 30% undigested food and fiber, 10-20% fat, 10% inorganic matter and several percent protein. The bacteria are normal residents of the intestinal microbiota that digests food and helps us in many other ways.
Using a rough average of 5 ounces of poop per person per day, consisting of about 1.25 ounces of solid matter and 3.75 ounces of water, the daily global load is 284,871 tons (258,431 metric tonnes) of solids and 854,613 quarts (808,766 liters) of liquid. Of course people pee too, an average of 1 to 2 liters per day (we’ll say 1.5 l), so that adds nearly 11 billion more liters of fluids excreted to the environment (see other estimates here).
What Happens to the Poop?
Not much happens to the poop made by 14% of us (more than a billion people) who have no sanitary facilities at all and defecate in the open, mainly in India, Indonesia, China, Ethiopia, Pakistan, Nigeria, Sudan, Nepal, Brazil, Niger and Bangladesh. Pigs, dogs and other scavengers may eat it and flies attend to the rest. In very sparsely settled areas material from diseased individuals may wash into wells, waterholes, lakes, streams or rivers bringing illness to people drinking or contacting the water, but in sparsely settled areas .
The 11% with “unimproved” sanitation have a ‘pour flush’ toilet (to which users add the water themselves), a pit latrine without a slab, or use a bucket, hanging toilet or hanging latrine. An additional 11% share sanitary facilities with two or more families, or use public facilities, but do not have such facilities at home. Shared facilities are not counted as ‘improved’ in World Health Organization-UNICEF data.
Finally, the 64% with access to “improved” sanitation have a flush toilet with a piped sewer system, septic tank, use a pour flush toilet, pit latrine, ventilated improved pit latrine, pit latrine with slab or a composting toilet. Distribution is very uneven, with 99% of people in the developed world having improved sanitation compared to only 52% in developing regions. The percentage of world population using improved sanitation increased from 49% in 1990 to 64% in 2012, but the Millenial Development Goal (7c) of 75% coverage is unlikely to be met by the 2015 target date, and a 2.5 billion people still lack such facilities.
How Does Improved Sanitation Help?
Improved sanitation reduces the spread of fecal-borne disease both by limiting direct contact with excrement and separating the flow of excrement from drinking water supplies, but it does not necessarily help the environment. The top line solution for improved sanitation has been flush toilets piped to sewers that connect to a sewage treatment plant. Whatever comes out of the treatment plant has to go somewhere, and towns or cities located along rivers or the ocean, like Boston, typically pump their effluent into those waters. About 90% of sewage is water, since sewer pipes also includes the water from baths, showers, dishwashing, toilet flushing and many business and industrial uses. Treatment plants must be designed to accommodate such large volumes.
What comes out of the sewage system may be untreated (raw) sewage; sewage with big pieces screened or settled out and fat skimmed away (‘primary treatment’); screened and de-fatted sewage that has been digested by bacteria and other microbes (‘secondary treatment’); or screened, settled, digested sewage that has been further treated to remove nitrogen and/or phosphorus (‘tertiary treatment’). Tertiary treatment removes nitrogen by using bacteria that convert ammonia to harmless nitrogen gas; and removes phosphorus either using particular bacteria that bioaccumulate it or by coagulation with aluminum or iron followed by precipitation and filtering. Tertiary treatment can also be done by running waste water through marshes or reed beds, where the plants take up the nutrients.
Release of untreated or primary-treated sewage harms biological communities near the outfall pipe, because it contains huge amounts of organic matter that smell, are unsightly, smother the local seafloor and deplete oxygen from the water as bacteria decompose the organic material. Pathogens contained in the outflow can infect people, commercial fish or shellfish and some marine wildlife.Primary sewage can be chlorinated to kill pathogens, but chlorine can react with the large amount of organic matter present to create chlorinated hydrocarbons that are potentially harmful. Effluent from secondary-treated sewage is almost always partially disinfected using chlorine, ozone or ultraviolet light to kill most microbes, though viruses may survive. However, it still contains all the nutrients that people excreted, including the nitrogen, phosphorus, iron and other elements that plants use. The excessive nutrients foster large populations of ‘weed’ species of algae and phytoplankton that reduce water quality, clog fishermen’s nets, harm fisheries and mariculture and help cause toxic red tides. When the plants die, bacteria decompose them, often using up the water’s dissolved oxygen and creating a ‘dead zone’ where aerobic marine life cannot survive.
Tertiary-treatment protects people, because it is disinfected to remove pathogens; and it also protects the environment, because it removes the nutrients that cause eutrophication and excessive algal growth. However, the process is usually judged too expensive for most treatment plants. In the meantime, the human poop problem is growing much faster than its solution, especially with regard to the ocean. Half the world's population now lives within 60 km of the sea, and three-quarters of all large cities are located on the coast, including 11 of the world’s 15 megacities, each of which has a population greater than 10 million and will add millions more citizens in the coming decade. By 2025 the world is expected to have 35 megacities.
Human poop isn’t the sole cause of all the problems mentioned above, because sewerage also contains discarded food, wastes from our pets and some industrial wastes. Furthermore, runoff of fertilizers and soil from agricultural fields and runoff from livestock feedlots where cattle and pigs are raised at high density join the effluent from numerous cities along river courses, contributing to dead zones where many rivers meet the sea. Many things must be done to maintain human health and restore ocean health, but for coastal waters, solving the human poop problem is one of the most important.
This story relates to the Ocean Health Index’s Clean Waters goal, which, among other things, assesses the presence of pathogens in coastal water based on the proportion of the populations served by adequate sanitary facilities; and the presence of excessive nutrients based on modeled input of land-based nitrogen from coastal countries and territories.