Nutrient Pollution (Eutrophication) • What It Is • What Causes It • What You Can Do About It
Eutrophication – excess nutrients While nutrients – nitrogen and phosphorus are necessary for life, excessive amounts going into aquatic systems cause major problems 1. One major source is human wastes –from cesspools in rural regions, sewage in urban areas. Especially in older cities with combined sewers, where stormwater is sent to sewage treatment plant. When there is much rain, the water exceeds the capacity of the treatment plant and it all (raw sewage) goes into waterbody untreated
AGRICULTURAL SOURCES • FERTILIZER – EXCESS USE. ONLY 18% OF NITROGEN GOES •
INTO CROPS, THE REST RUNS OFF MANURE – WHEN EXCEEDS ABILITY OF CROPLANDS TO SEQUESTER, IT RUNS OFF
ATMOSPHERIC SOURCES • GASES FROM BURNING FOSSIL FUELS RELEASE INTO ATMOSPHERE, THEN THEY ARE DEPOSITED ON LAND AND WATER
URBAN RUNOFF • Lawn fertilizers and animal waste • Impervious surfaces - rooftops, sidewalks, roads - covered •
by asphalt, concrete, brick, and stone - accelerate run-off Land use plays major role in water pollution!
PROBLEMS OF EXCESS NUTRIENTS Nutrients cause algal blooms: (A) When bloom dies, cells sink to the bottom (B) and are decomposed by bacteria which use oxygen. Result is low oxygen (hypoxia) in deeper waters
HYPOXIA USUALLY MOST SEVERE IN LATE SUMMER/EARLY FALL. 150 “DEAD ZONES” IN WORLD ASSOCIATED WITH NITROGEN FROM FERTILIZERS AND SEWAGE
Largest US dead zone is in Gulf of Mexico, which receives nutrient runoff from the main agricultural area of the country. Can be the size of MA or NJ. Size is bigger in years with more rainfall and so more runoff.
SOURCES OF NUTRIENTS FROM FAR AWAY Source: Gulfhypoxia.net
Thousands upon thousands of dead and rotting fish float belly-up in the polluted Indian River Lagoon, devastating indictors of the state’s failure to control nutrient levels in one of the most bio-diverse waterways in the country.
EFFECTS ON CORAL REEFS • NUTRIENTS CAUSE GROWTH OF MACROALGAE THAT •
SPREAD OVER AND SMOTHER CORALS. EFFECTS WORSE WHEN SEA URCHIN OR FISH HERBIVORES (WHICH WOULD EAT THE ALGAE) ARE SCARCE (PERHAPS OVERFISHED) HEALTHY CORAL
CORAL COVERED WITH MACROALGAE
• Harmful Algal Blooms (HAB): phytoplankton species that produce toxins affect many different consumers • Since the 1970s the number of HAB outbreaks has increased 20-fold. Not all related to eutrophication. • Different species produce different symptoms- all unpleasant
Toxins from bloom can accumulate in shellfish and then poison people who eat them
HABs (often Cyanobacteria) also occur in freshwater, where drinking water sources can be impaired. In freshwater, phosphorus is main cause
SOLUTIONS: Controlling AG Inputs • CONSERVATION TILLAGE, TERRACING,
• • •
STRIP CROPPING, CONTOUR CROPPING BUFFER STRIPS OF VEGETATION TO CATCH RUNOFF REDUCE FERTILIZER USE, RECYCLE MANURE OR REMOVE NUTRIENTS BEFORE DISCHARGE REDUCE CONSUMPTION OF HIGH DENSITY FACTORY FARMED BEEF, PIG, AND POULTRY RESTORE/CREATE WETLANDS
SOLUTIONS: Urban Management • IMPROVE SEWER SYSTEMS – INCLUDING COMBINED SEWER OVERFLOW (CSO) PROBLEMS, TERTIARY TREATMENT • INCREASE WETLANDS FOR TERTIARY TREATMENT • REDUCE IMPERVIOUS AREAS – MORE GREEN SPACE • REDUCE EROSION FROM CONSTRUCTION SITES • STREET SWEEPING CSO • STORE STORMWATER
Ways to Store Stormwater Rain Barrels
Bioswale in Brooklyn Green roof in Chicago
Porous pavement in parking lots
SOLUTIONS: In-Water Treatment • SEAWEED FARMING: removes nutrients and might also have a market (agar, sushi) • GROW OYSTERS AND CLAMS: help control plankton blooms – filter large amount of water daily • TREATMENT WETLANDS: Plants absorb nutrients, debris trapped in slowmoving waters, microbes break down other pollutants.
Trends and the Future Eutrophication widespread and increasing in the US and worldwide. Progress (when seen) due primarily to improvement in point sources (sewage); less for non-point (runoff) sources HABs increasing world-wide Recovery time may be very long Fishing and climate change will intensify the problems Good news – whales back in NY area
SOLUTIONS: At Home • CONSIDER YOUR LANDSCAPING • Add an Ocean Friendly Garden, rain garden, xeriscaping, Florida Friendly Landscaping, or other similar program. • IMPROVE WATER STORAGE • Add a rain barrel, swales, and permeable soil to stop runoff. • GO NATIVE • Ditch water and fertilizer intensive turf grasses and plant native plants.
WHAT YOU CAN DO Make changes at home- collect rainwater, plant natives Eat less factory farmed meat, switch to a higher percentage of organically grown plant-based foods Advocate for upgrading sewage treatment systems- and be sure that your septic tank is working correctly! Install a gray water system so you can recycle water that goes down the sink Advocate for strong local fertilizer ordinances and community gray water systems Help eliminate pet waste - advocate for pet waste disposal stations and make sure local litter ordinances are enforced
RESOURCES Questions? Contact Dr. Judith Weis at [email protected]
Join the Grassroots Network Sierra Club Marine Team website at https://content.sierraclub.org/grassrootsnetwork/teams /marine-team Subscribe to the Marine Team List Serve ([email protected]
RESOURCES Check out the Sierra Club Water Sentinels program, nationally and locally. Visit their Grassroots Network Water Sentinels Team website at: https://content.sierraclub.org/grassrootsnetwork/teams /national-water-sentinels As recommended by the Sierra Club Water Sentinels Program, visit the Georgetown Climate Center's Adaptation Clearinghouse for their listing of resources on green infrastructructure. Download their Green Infrastructure Toolkit at: http://www.georgetownclimate.org/adaptation/toolkits /green-infrastructure-toolkit/introduction.html