ENS-112 Environmental Science Chapter 12 PDF

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Chapter 12 notes from Dr. Adrienne George's lectures for ENS-112 Environmental Science at The University of Tampa...

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Environmental Science 112 FALL SEMESTER 2018 INSTRUCTOR: DR. Adrienne George [email protected]

Chapter 12 Freshwater Systems ● Majority (97.5%) of Earth’s Water is in the oceans and is too salty to drink or use for irrigation ○ Only 2.5% is considered fresh water, water that is relatively pure and free from salts ■ 79% trapped in ice caps and glaciers ■ 20% trapped in groundwater ■ 1% is surface water, fresh water that is easily available to us ● Figure 12.3 ● Surface water is located atop Earth’s surface, such as in a river or lake ● Groundwater is water beneath the surface that resides within pores in soil or rock ○ Any water that does not evaporate, flow into waterways, or get taken up by organisms will infiltrate into groundwater ○ Groundwater can remain underground for thousands of years at a time

Groundwater plays key roles in the hydrologic cycle ● Groundwater is contained within aquifers… ● … ● Areas where water can infiltrate through the surface and reach the aquifer = recharge zone ● Confined aquifers are trapped between impermeable clay, while unconfined aquifers are not

Surface Water converges in river and stream ecosystems 1

● Surface water becomes groundwater by infiltration ● Groundwater becomes surface water through springs ● Water that falls from the sky or melts from snow or a glacier that flows over a land surface is called runof ○ Runof converges in low-lying areas, forming streams, which can merge into rivers, which eventually reach a lake or oceans ● The are of land drained by a river system and all of its tributaries makes up that river’s drainage basin or watershed ● Areas near a river's course that are flooded periodically are within the rivers floodplain ○ Frequent flooding and deposition of soil makes floodplain soils especially fertile ○ Agriculture thrives in flood plains, and riparian forests near riversides are especially rich in species

Lakes and ponds are ecologically diverse systems ● Different Zones ○ Littoral: outer edge/coast, aquatic plants ○ Limnetic: top, sun, photosynthesis, phytoplankton ○ Profundal: middle, no sun, no photosynthesis ○ Benthic: bottom, no sun, no photosynthesis ● Ponds and lakes can change over time as rivers and streams bring them nutrients ● Oligotrophic lakes and ponds are low in nutrients and high in oxygen ● Over time, the addition of nutrients can transition the lake or pond to eutrophic -high-nutrient, low oxygen -- conditions

Freshwater wetlands include marshes, swamps, bogs, and vernal ponds ● Wetlands are systems where the soil is saturated with water ● Freshwater marshes consist of plants that grow above the water's surface ● Swamps also contain standing water but are in forested areas

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● Bogs are ponds covered in thick floating mats of vegetation ● Wetlands can be seasonal, such as vernal pools that form in the snowmelt of early springs and dry up later in the summer ● Wetlands provide many water-related ecosystem services including slowing runoff, reducing flooding, recharging aquifers, and filtering pollutants ● Wetlands have been heavily impacted by human activities, including draining and filling for agriculture, withdrawing water for irrigation, and construction of dams

The Oceans ● The world’s five oceans are all connected, making a single body of water that covers 71% of Earth’s surface

The physical makeup of the ocean is complex ● Ocean water contains ~ 96.5% water by mass, with the rest consisting of ions from dissolved salts ○ The salts arise from runoff that carries salts and sediments from continents into the oceans ● Sunlight does not penetrate ocean water deeply, so temperatures tend to decrease with depth ● Vast, river like flows of water called currents are driven by differences in density, heating, cooling, gravity, and wind

● Water movement ○ Horizontal ■ Currents ○ Vertical ■ Pulling ● Brings nutrients up the the surface ↑ ■ Downwelling ● Moving water from the surface down to the depths ↓ 3

● Can bring oxygen down to the depths and takes carbon dioxide down to the depths, and out of the atmosphere ● Surface winds and heating also create vertical currents in seawater ● Upwelling pulls cold,deep, nutrient-rich water to the surface ● Surface currents that converge create downwellings, which transport warm surface water to deeper waters, providing and influx of dissolved oxygen and “burying” carbon dioxide from the atmosphere ● Many parts of the ocean floor are rugged and complex ○ Underwater volcanoes can build islands above sea level ○ The Mid-Atlantic Ridge is an underwater mountain range that runs the length of the Atlantic Ocean

Ocean Currents afect Earth’s climate ● The thermohaline circulation is a worldwide current system in which warmer, lower-salinity water moves along the surface and colder, saltier (denser) water moves horizontally below the surface ○ This moves warm water in the Gulf Stream to the Atlantic Ocean near Europe, where heat is released and the cooler water sinks ● The region of downwelling near western Europe is called the North Atlantic Deep Water (NADW) ○ Scientists are concerned that an influx in freshwater from melting glaciers in Greenland could disrupt this flow ■ Water loses heat to cold air and sinks ■ Sunlight warms water on ocean's surface in tropics ■ This whole process takes about 1000 years

Ocean currents afect Earth’s climate ● The El Nino-Southern Oscillation (ENSO) is a systematic shift in atmospheric pressure, sea surface temperature, and ocean circulation in the tropical Pacific Ocean

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● Under normal conditions, prevailing winds blow from east to west along the equator, forming a large convective loop in the atmosphere ○ This causes a “pile-up” of warm water to form near Indonesia, fueling storms in that region ● El Nino conditions are triggered when air pressure decreases in the eastern pacific and increases in the western Pacific ○ This can create storm activity in normally arid regions like california and drier conditions in Indonesia ● La Nina events are the opposite of El Nino events; unusually cold waters rise to the surface and extends westward, causing winds blowing to the west to strengthen ● ENSO cycles occur every 2-8 years ○ Scientists are studying whether changes in air and sea temperatures are increasing the frequency and strength of these cycles

Marine and Coastal Ecosystems ● Regions of ocean water differ greatly, with certain zones supporting more life than others depending on characteristics such as: ○ Topography ○ Temperature

Intertidal zones undergo constant change ● Intertidal ecosystems spread between the uppermost reach of the high tide and lowest limits of the low tide

Fresh water meets saltwater in estuaries ● Estuaries are bodies of water where rivers flow into the ocean, mixing saltwater with freshwater ○ Salinity fluctuates daily due to the tides and changes in river flow ○ Estuaries are sheltered from the heavy waves of the ocean and provide habitat for many plants, which provide food for shellfish, birds, and fish

Salt marshes line temperate shorelines

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● Salt marshes occur where the tides wash over gently sloping sandy or silty substrates ○ Water from rising and falling tides flows in and out of salt marshes through channels called tidal creeks ○ Salt marshes provide biodiversity, filter pollutants, and stabilize shorelines

Mangrove forests line coasts in the tropics and subtropics ● Mangroves are trees that are salt tolerants, with roots that grow upward to gather oxygen and others that grown down to support the tree like stilts ○ Fish, shellfish, snakes, and other organisms thrive among the roots in the water, while many birds feed and nest in the tree foliage

Kelp forests harbor many organisms ● Along many temperate coasts, large brown algae called kelp grow from the floor of the continental shelves, reaching toward the sunlit surface ○ Dense stands form underwater “forests,”which provide food and shelter for many animals

Coral reefs are treasure troves of biodiversity ● A coral reef is a mass of calcium carbonate composed of the shells of tiny animals called corals ● Coral reefs host tremendous biodiversity because they provide shelter from waves and their complex physical structure produces many habitats ● Form symbiotic relationships with algae called zooxanthellae, which produce food through photosynthesis ● Many coral reefs are “bleaching,” a process that occurs when zooxanthellae lose color or are released, depriving the coral of nutrition ○ Occurs when coral are stressed by increased water temperatures and elevated pollution levels

Open-ocean ecosystems vary in their biodiversity ● In the open ocean, most primary productivity occurs in the top layer, called the

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photic zone ○ Microscopic phytoplankton constitute the base of the food chain ● Pelagic habitats are found between the ocean surface and floor ● Benthic habitats occur on the ocean floor

Human activities afect our waterways ● Water is one of our most precious resources and is renewable ● People are withdrawing water at unsustainable levels and depleting many sources of surface water and groundwater ● The construction of engineered waterways like dams and canals …

Fresh water and human populations are unevenly distributed around earth ● Climate differences and other factors have created varying amounts of groundwater, surface water, and precipitation across Earth

Water supplies households, industry, and agriculture ● The majoritt of our freshwater use about 70% is for agriculture ○ Industry accounts for about 20% ○ Residential use accounts for about 10% ● The increase demand for irrigation has led to consumptive use of aquifers and surface waters, where we remove water but do not return it ○ Nonconsumptive use, such as with hydroelectric energy…

Excessive water withdrawal of water faster than it can drain rivers and lakes ● Water mining the withdrawal of water faster than it can be replenished, is taking place in many regions

Groundwater can also be depleted ● Groundwater is depleted more easily than surface water because it is recharged so slowly ● As aquifers are mined, water tables drop ● When groundwater is over extracted in coastal areas, saltwater from the ocean can intrude into inland aquifers

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● As aquifers lose water, they become less able to support overlying strata, causing the land surface to subside ○ This can cause buildings to lean or large areas of land to suddenly collapse

Bottled water has ecological costs ● Bottled water has become a booming business, with a $160 billion in annual sales ○ People buy bottled water for convenience and taste, even though blind taste tests have shown no preference ● Bottled water has major ecological impacts, with energy costs 1000-2000 times greater than tap water and 1.5 million tons of plastic waste generated annually

We have erected thousands of dams ● A dam is any obstruction placed in a river or stream to block its flow ● Dams create reservoirs, artificial lakes that store water for human use ○ Dams help prevent floods, provide drinking water facilitate irrigation, and generate electricity

Solutions to depletion of fresh water ● Population growth, expansion of irrigation, and industrial development have doubled our use of freshwater over the past 50 years ● Addressing water shortages means either increasing supply or… ● Desalination or desalinization is the removal of salt from seawater or other water ○ Salt can be removed by heating and evaporating ocean water (destillation) or by filtering through membranes with tiny pores that trap the salt (reverse osmosis) ● Desalination is expensive, uses a lot of energy, and generates concentrated salty waste ○ Saudi arabia gets mosts of its drinking water from desalination

We can reduce our demand for water ● Since agriculture makes up the majority of water demand, it is the most logical place to start conserving

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○ Lining irrigation canals ○ Leveling fields to minimize runoff ○ Efficient irrigation methods, like drop irrigation ○ Eliminating water-intensive crops from arid region ● Water use can be reduced in households by installing low-flow faucets, showerheads, washing machines, and toilets ● Using alternative sources of water for gardening and lawn care also helps to reduce a home’s footprint ○ Rainwater harvesting is the process of collecting rainwater with a rain barrel ○ Graywater is the used water from showers and sinks and can be used in some places for watering ○ Xeriscaping …. ○ Water pollution includes and changes in the chemical, physical, or biological properties of water due to human activities ○ Many impacts of water pollution are not visible, such as pH, nutrient concentration, and dissolved oxygen, so they must be chemically monitored ○ Point sources are discrete locations that release water pollution ○ Non-point sources are many location that release water pollution, we cannot determine where it comes from exactly

Water pollution takes many forms ● Many types of toxic chemicals have been released into water sources ● Eutrophication is a natural process, but human inputs from farms, golf courses, lawns, and sewage can dramatically increase its rate ● A “dead-zone” of very low oxygen waters has formed in the Gulf of Mexico due to nutrient flow from the mississippi and atchafalaya rivers ● Excessive nutrient concentrations can lead to harmful algae blooms, which are population explosions of algae that produce powerful toxins ○ If the algae produce a red pigment that discolors the water it is called red 9

tide ● … ● Wastewater is water affected by human activities and includes water from toilets, sinks, dishwashers, and washing machines ● Sediments are eroded soils carried to rivers by runoff and transported long distances ○ Clear-cutting, mining and clearing land for development have all increased rates of erosion, creating sediment pollution ● Large oil spills are infrequent but their impacts around the spill site are staggering ○ The deepwater horizon was an offshore oil platform that exploded in 2010, spilling oil…. ● Discarded fishing nets, fishing line, plastic bags and bottles, and other trash accumulate in regions of the ocean where currents converge called gyres ● One such area is the Great Pacific Garbage Patch, and area in the northern pacific where plastic outnumbers plankton by a 6 to 1 ratio

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