advanced placement environmental science · freshwater biomes runoff of precipitation from...

ENVIRONMENTAL SCIENCE

Aquatic + Terrestrial Biomes Adv

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Instructor 2014

Aquatic & Terrestrial Biomes

Copyright © 2013 National Math + Science Initiative®, Inc., Dallas, TX. All rights reserved.

Aquatic Biomes are large geographic areas that have similar plant and animal communities. Aquatic biomes are generally divided into two groups based on the absence or presence of salt. Marine biomes generally have a salt concentration greater than 3%, whereas freshwater biomes have a salt concentration that is less than 1%.

Several properties of water have allowed life to flourish within these biomes. The ability of water to stabilize temperature depends on its relatively high specific heat. The buoyant force that water provides minimizes the energy spent by organisms in the struggle against gravity. In addition, when present, dissolved nutrients are readily obtained by aquatic organisms. Nutrient availability, dissolved oxygen content, and access to sunlight determine where aquatic organisms can live.

Freshwater Biomes Runoff of precipitation from watersheds provides the water for freshwater biomes. Freshwater biomes can be grouped in two distinct categories. The first category is standing water or lentic ecosystems, which consist of lakes, ponds, and inland wetlands.

Lakes are classified by their rate of primary productivity: 1. Oligotrophic Lake – very low primary productivity; generally considered

nutrient-poor; newly formed or located in cold regions; high dissolved oxygen2. Mesotrophic Lake – fall somewhere between oligotrophic and eutrophic lakes in

productivity3. Eutrophic Lake - high primary productivity; contain large communities with

diverse populations; often older lakesEutrophic lakes are often caused by an influx of limiting nutrients such as nitrates and phosphates. This anthropogenic cause is called cultural eutrophication.

The waters of these freshwater lakes can be defined based on thermal characteristics. Thermal Zones (Fig. 1): Epilimnion warm upper layer of water with high levels of dissolved oxygen Hypolimnion lower, colder, denser layer that is not exposed to atmosphere which leads to a lower dissolved oxygen content Thermocline the region between the two layers that has a rapid temperature change

Fig. 1

Aquatic + Terrestrial Biomes


The waters of freshwater lakes can also be defined based upon depth and distance from the shoreline (Fig. 2). The littoral zone is the shallow area near the shore. Plants can take root and thrive in this area. The limnetic zone is the open surface water of the lake past the littoral zone. Together the limnetic and littoral zones make up the photic or euphotic zone (light-penetrating zone). Plankton (small, drifting organisms) are common here. They consist of phytoplankton (autotrophic) and zooplankton (heterotrophic). The profundal zone is the deep water beneath the limnetic zone and does not receive light (aphotic). The benthic zone lies at the bottom of the lake. The organisms that live here rely on detritus for energy.

Inland wetlands are lands covered with fresh water all or part of the year. These include marshes, swamps, bogs, prairie potholes, and floodplains. They have great ecological and economic importance. These include wildlife habitat, charge zones for aquifers, filter water to improve quality, reduce erosion, and contribute to the biogeochemical cycles. Inland wetlands have been greatly reduced by man. Agriculture is the chief contributor to the loss of wetlands. Urban development has also played a role in wetland degradation.

The second category of freshwater biomes is flowing water or lotic ecosystems. These include streams and rivers. Rivers typically have three phases that they undergo as they flow towards the sea. Many rivers’ headwater or source originates in the mountains. The river here is cold, narrow, and turbulent. Dissolved oxygen is high, while primary productivity is low. Organisms found here have to be well adapted to fast-moving water. Further downstream, the river enters a transition zone where it slows, widens and often becomes deeper. This promotes production, and supports a more diverse community. Once the river enters the flood plain it is very broad and moves very slowly. Dissolved oxygen is much lower at this point.

Fig. 2



Marine Biomes Marine biomes consist of coastal ocean, open ocean, coral reefs, estuaries, coastal marshes, and mangrove swamps.

Oceans cover over 70% of earth’s surface. They regulate earth’s climate by distributing heat throughout the world on ocean currents. The ocean is divided vertically into the intertidal zone, the neretic zone, and the oceanic zone (Fig. 3). The intertidal zone is the land that is exposed at low tide and covered at high tide. Organisms here must be very tolerant to harsh, extremely varying conditions. The neretic zone is the ocean covering the continental shelf. Although this makes up only ten percent of the ocean, it contains over ninety percent of the ocean’s organisms. The oceanic zone is the waters past the continental shelf and is much less productive. Nektonic (strong-swimming) organisms swim long distances through this “desert” in search of food. The ocean can also be divided as shown below (Fig. 3). In this way it is separated into the euphotic, aphotic, abyssal, and hadal regions.

Coral reefs are found in the clear, warm coastal waters of the tropics and subtropics. These have often been called the “rainforest” of the marine ecosystems due to their high diversity. The foundation of these unique ecosystems is the calcium carbonate exoskeleton secreted by coral. This becomes the backbone of the reef which provides habitat for many species. These reefs are important nurseries for many species of fish. Coral reefs are currently under extreme pressure by man. This includes pollution, destruction for shipping channels, and even bleaching. Coral bleaching is due to an increase in water temperature, which is attributed to global warming.

Estuaries, coastal marshes, and mangrove swamps are all found along the coast.

Fig. 3



Estuaries are areas of coastal water where freshwater from rivers empty into the ocean. This creates brackish water that varies in salinity and temperature. The flowing water does, however, provide a constant supply of nutrients making this ecosystem one of the most productive. Estuaries are vital nurseries for oceanic fish and critical habitat for migratory birds.

Estuaries have been badly abused with pollution from agriculture runoff to over-fishing. Eutrophication has also led to hypoxia (reduction of dissolved oxygen) that leads to “dead zones.”

Coastal wetlands, which include coastal marshes and mangrove swamps, maintain the integrity of the shoreline by reducing erosion. They also provide areas for breeding and for the rearing of young fish and invertebrates. Mangrove swamps are found in the tropical areas of the world while coastal marshes are found more in temperate areas.

Almost forty percent of the world’s population lives within one hundred kilometers of the coast. This has caused coastal wetlands to be greatly degraded over the years. Habitat conversion, pollution, and introduction of invasive species are among some of the threats.

Terrestrial Scientists divide the terrestrial world into seven major biomes. Based on the following factors:

• average annual precipitation• temperature• soil type

These factors are a result of each biome’s latitude and altitude leading to unique biological communities.

Tundra The term tundra is Russian for “treeless mountain.” This is an apt description of a biome dominated by dwarf shrubs, mosses, grasses and lichens. Tundra is found in the extreme northern and southern latitudes. It is also found at higher elevations throughout the world’s mountain ranges as alpine tundra. Melted surface water exists only during a short summer season. High winds, limited water (melted) and low temperature inhibit plant growth. Ranging from a few inches to a few feet below the surface, permanently frozen soil (permafrost) is found.

During the summer months, millions of birds migrate to the Arctic tundra. However, only 48 species of land mammals can be found in the Arctic tundra. These mammals escape the extreme winters by hibernating or migrating.

Due to extreme conditions, tundra has remained relatively free from human activity. However, the pursuit of natural resources (oil, uranium, etc.) and global warming could radically change this biome in a relatively short period of time.



Taiga The taiga is the world’s largest terrestrial biome. Evergreens (pines and spruces) dominate this biome. Slow decomposition and leaching conspire to deplete nutrients in the soil. Another Russian term, podzol, is used to describe this “ashy” soil. The taiga is also known as the boreal forest.

The taiga is found throughout the high northern latitudes (Russia and Canada). This biome supports a larger number of mammals than the tundra and is also nesting grounds for many migrating birds.

Large tracts of taiga have been harvested for lumber. A common practice for removing timber is called clear-cutting. This removes all trees in an area and is very disruptive to the soil.

Grassland Two main divisions of grasslands:

• Tropical grasslands (savannas)• Temperate grasslands

Grasslands are commonly found between deciduous forests and deserts. This biome became widespread toward the end of the Cretaceous. The flora typically consists of a variety of grasses and arid-tolerant trees. Many of the animals found in this biome have unique adaptations that enable them to exploit grasses. These adaptations include specialized dentition and digestive tracts.

Temperate grasslands typically receive 20 – 35 inches of rain each year. The soil is rich (dark, fertile humus) in nutrients and held together by a vast network of roots. The quality of the soil, the lack of trees, and the relative “flatness” of grasslands has led to this biome being the most disturbed biome in North America. Over 99% of this biome has been altered by farming and ranching.

Temperate grassland names: 1. Prairie (North America)2. Veldt (Africa)3. Steppes (Asia)4. Pampas (South America)

Tropical grasslands are equatorial in occurrence and are usually savannas. Savannas cover almost half of Africa. Savannas typically receive 20 – 50 inches of precipitation each year.

Both temperate and tropical grasslands are fairly resilient. Fire and grazing (controlled) maintain the integrity of the biome.



Temperate Forest Temperate forests occur in eastern North America, northeastern Asia, and Europe. Broad-leaf trees (deciduous) dominate the flora. Although they have more tree diversity (3-4 species per km2) than the taiga, they pale in comparison to tropical rainforests (up to 100 species per km2). Temperate forests receive on average 30 to 60 inches of precipitation each year. The soil found here is fertile and enriched by decaying leaves.

Tropical Rainforest Tropical rainforests occur near the equator, within the Tropic of Cancer and Tropic of Capricorn. This is the most biodiverse of all biomes. A major characteristic of tropical rainforests is their lack of traditional seasonality. Temperature (20-25° C) and amount of sunlight varies little throughout the year. Precipitation exceeds 2000 mm (>80 inches) and is equally distributed throughout the year. The soil found in tropical rainforests is very poor. Decomposition is very rapid and soils are subject to heavy leaching.

Tropical rainforests have a multilayered canopy that allows very little light to reach the ground. Plant-life is very diverse Buttressed trunks and prop roots support tall trees that are mostly evergreen with large leaves. Epiphytes are abundant (orchids, bromeliads, and lianas). More than half of tropical rainforests have been destroyed.

Mediterranean Mediterranean or chaparral is a temperate biome, characterized by hot-dry summers and mild and rainy winters. Nearly all of the rainfall occurs in the winter. This biome occurs in the Mediterranean Basin, California, Central Chile, Southwest Australia, and the Cape Province of South Africa.

Desert Deserts cover 20% of Earth’s surface. A desert is a biome where potential evaporation exceeds precipitation (<10 inches). The vegetation is drought-resistant, sparse, and widely spread. The flora and fauna possess adaptations that enable them to survive in extreme conditions. Soil is practically non-existent. Deserts are found in the interior of continents or from rain shadow effect.

Three classes of deserts: 1. Tropical desert – temperatures usually high year-round and little rain.

Ex. Sahara 2. Temperate desert – Daytime temperatures high in summer and low in winter,

more precipitation than tropical desert. Ex. Mojave

3. Cold desert – Winters are cold and summers are warm or hot.Ex. Gobi

Semi-deserts are intermediate between desert and grassland and dominated with thorn trees and shrubs adapted to long dry spells, with brief periods of sometime heavy rain.


(a) Discuss TWO important causes for the variation in the temperature and/or salinity of an estuary. Be sure to include the connection between each cause and temperature and/or salinity. (2 points total)

1 point for each cause and connection – 2 point maximum

2 points can be earned for: • 2 causes and connections for temperature OR• 2 causes and connections for salinity OR• 1 for temperature and 1 for salinity

Cause/Variation in Temperature connection with direction of change

Salinity connection with direction of change

Daily tidal cycle Mixing of waters of different temperatures

Fluctuations due to mixing of waters of different salinities.

Seasonal/diurnal flow of freshwater from rivers, streams and runoff from land including snow melt & ice melt

Mixing of waters of different temperatures

Fluctuations due to mixing of waters of different salinities.

Suspended solids/turbidity Increased solar absorption resulting in higher temperatures

Warmer temperatures increase evaporation which would increase salinity

Storms (rainfall), hurricanes or typhoons

Mixing of waters of different temperatures

Influx of additional freshwater, lowering salinity levels Influx of ocean water from onshore storms, hurricanes and typhoons, raising salinity levels

Seasonal air temperature variations Seasonal solar influx Seasonal variation in vegetation

Water is colder in the winter and warmer in the summer (Shallow waters have low capacity to store heat over time)

Warmer temperatures increase evaporation which would increase salinity Warmer water has increased salt solubility

Rate of evaporation

Evaporation is a cooling process and therefore lowers the temperature of surface layers

Loss of water due to evaporation increases salt concentration

Wind (Seiche-wind driven tides) Promotes mixing of the water column

Onshore wind would bring in ocean water and raise salinity Offshore wind would bring in freshwater from tributaries and lower salinity

Color of substrate

The darker the substrate, the greater the solar absorption and therefore the greater the increase in water temperature

Warmer temperatures increase evaporation which would increase salinity

Cloud cover Greater cloud cover results in reduced solar input and cooler water temperatures


Cause/Variation in Temperature connection with direction of change

Salinity connection with direction of change

Diurnal air temperature variations

Solar input during the day increases water temperatures Lack of solar input at night allows cooling of the water

Warmer temperatures increase evaporation

Drought Mixing of water of different temperatures

Decrease in freshwater flow to estuary or increased influx of ocean water will lead to increased salinity

(b) Discuss TWO roles that coastal wetlands play that are ecologically important, and TWO roles that wetlands play that are economically important. (4 points total) 1 point for each ecologically important role discussed for a total of 2 points and 1 point for each economically important role discussed for a grand total of 4 points

Ecologically Important Roles

ecologically important role discussion High productivity (net primary)

Carbon Dioxide Sink Supports complex food webs, high rate of photosynthesis absorbs large amounts of CO2 & releases O2

High species diversity/Biodiversity Promotes ecosystem stability, resilience and nutrient cycling

Nursery for fish & crustaceans Sustain/support marine ecosystems & life cycles

Nesting/Migration sites Sustain/support marine ecosystems & the life cycles of waterfowl, shorebirds, & other appropriate wildlife

Filters/Sponges Contributes to water quality by trapping suspended solids, sediments, sediment (toxic) pollutants (toxins), and/or nutrients

Reduction of flooding Slowing the flow of water from ocean to upland ecosystems

Reduction of erosion Absorbing erosive energy of wave action or slowing the flow of floodwater

Unique habitat Provides habitat for organisms with specific needs such as moisture, salinity, temperature, flat water


economically important role discussion

Recreational income (tourism) Boating, fishing, hunting, bird-watching, photography, and/or outdoor recreation

Property protection Absorbing the flow of water and/or buffering shores from damage and erosion

Fishing industry Commercial harvesting and/or processing of fish (shellfish); provides employment, tax base, or the selling of the catch

Intercoastal waterway Protected passage for commerce which is cheaper and safer than ocean passage

Filters/Sponges

Contribute to water quality by trapping suspended solids, sediments, sediment pollutants and/or nutrients that would otherwise be subjected to water purification processes that would be supported financially by the local community

Employment opportunities Such as wetland ecologists, wildlife managers, tour guides, and nature or recreational store owners

Sewage treatment or storm water treatment Wastewater treatment that would otherwise be paid for by the local community

Agriculture Haying or grazing in salt marshes, seaweed harvesting; rice paddies and the sale of (appropriate) agricultural products

Aquaculture/Mariculture Raising, harvesting, & selling of fish & shellfish Aesthetic value Leads to increased property values

High biodiversity Leads to increased bioprospecting for commercial use

Cooling of power plants/industrial facilities Use of brackish water allows power plants to use land that is less expensive than upstream land with freshwater accessibility

Tidal power Provides an alternative energy source in an area protected from open ocean

Carbon dioxide sink Removes & sequesters CO2 from the atmosphere that might otherwise be subjected to expensive removal methods

Source of methane gas Might be collected and sold as a fuel


(c) Identify and explain THREE ways in which humans have had a negative impact on or have degraded coastal wetlands. (3 points total)

1 point for each identification and explanation of the negative impact

Identification Explanation

Construction/Building/Developme nt

Filling in/ draining of wetlands, modification of shorelines, increase in impervious surfaces causing more runoff, point & non-point source pollution. Habitat destruction; habitat fragmentation; loss of native flora and fauna.

Industrial/Commercial enterprises Point source pollution including heavy metals, organic chemicals, thermal pollution, PCBs. Acid deposition upwind of estuary causes a decrease in pH releasing heavy metals.

Housing, agriculture, golf courses & commercial/popular-use beaches

Non-point source pollution such as fertilizers, pesticides, or pet waste. Fertilizers lead to eutrophication; pesticides weaken or kill native species; hypoxia; habitat destruction; loss of native flora & fauna; sedimentation

Roads and bridges

Increased traffic adds NOx and particulates to the air and contributes to ground-level ozone. Point & nonpoint source pollution such as heavy metals, fuel, & antifreeze. Bridges restrict the flow of water and modify sedimentation patterns; salt runoff from roadways & bridges

Dredging (deepen channels for navigation, water exchange, and

species access to spawning grounds)

Sediment covers benthic vegetation, spawning sites, and fouls feeding apparatus of filter feeders Habitat destruction; loss of native flora and fauna Stirring up of toxic material & heavy metals in sediment

Petroleum drilling Transportation of petroleum

Contamination of water from oil spills degrades habitat Sediment covers benthic vegetation, spawning sites, and fouls feeding apparatus of filter feeders Habitat destruction; loss of native flora and fauna

Oyster shell, aggregate, or fill material dredging (including

dredging to replenish beaches)

Increased wave action contributes to erosion and/or turbidity of the water Sediment covers benthic vegetation, spawning sites, and fouls feeding apparatus of filter feeders Habitat destruction; loss of native flora and fauna Stirring up of toxic material & heavy metals in sediment

Over-harvest/over-hunting of commercial & sport species

Reduction of commercial & sport species populations that may create ecosystem instability and impact food webs; decrease in biodiversity

Dam construction & water diversion projects (levees, channelization, irrigation)

Redistributes fresh water & nutrients; interferes with fish migration; restricts sediment flow


(d) Choose one of the negative human impacts you identified in part (c), and explain one environmental policy and one economic incentive that could have prevented it. (2 points)

1 point for the explanation of an environmental policy and 1 point for the explanation of an economic incentive that could have prevented the negative human impact selected from part( c)

Explanation could include a specific law or policy, but just naming the law or policy is not sufficient.

• If part (c) is unanswered then no points will be awarded for part (d)• If an incorrect identity from part (c) is chosen for part (d), then no points will be awarded for part (d)• If a negative human impact is not specifically identified from part (c), then no points will be awarded for

part (d)

Environmental Policy – “official rules or regulations concerning the environment adopted, implemented, and enforced by some governmental agency”, Cunningham & Saigo, 6th edition.

Regulations Pertaining to Wetlands Description

Clean Water Act Regulates placement of all dredge and fill materials, sets national water goals, requires projects to meet water quality standards; requires replacement of damaged or destroyed wetlands

Federal River and Harbor Act Regulates construction activities in navigable waters National Environmental Policy Act

(NEPA) Requires full disclosure of the potential effects of proposed federal action (environmental impact statement)

Coastal Zone Management Act Federal funds will be awarded to projects that comply with the coastal zone management plan

Endangered Species Act Prohibits any land use that will threaten the survival of an endangered or threatened species (fines, seizures, imprisonment)

“Safe Harbor Agreements” Landowners voluntarily agree to maintain habitats for endangered or threatened species who inhabit their land with technical support from the government

Marine Protection Act Regulates waste disposal into coastal waters

Fifth Amendment, Eminent Domain Private landowners must sell property to the government if the area is needed for the public good, must be purchased at a fair market value

Clean Air Act Includes provisions for primary & secondary air pollutants; trading emissions credits

Migratory Bird Conservation Act Protection & preservation of migratory bird habitats

Other Environmental Policies:

• rolling easements; prioritize public access to the shore over properties rights to build seawalls• zonings• increase number of wildlife refuges and/or coastal wetlands• local and regional governments adopt policies guided by the “precautionary principle” (if potential harm is

suspected, then precaution measures should be taken)• local/regional policies or ordinances that are applicable

Economic Incentives: • taxes (reductions, increases, or waiving) or government backed bonds to promote preservation of coastal

wetlands • fines/penalties for noncompliance• government subsidies to promote preservation of coastal wetlands


• land trade-offs to discourage development of coastal wetlands• charge user fees to discourage development of coastal wetlands• waiving of permit fees in lieu of damaging environmental practices• use green taxes or effluent fees to internalize harmful environmental costs of production and consumption of

industrial products• reduce property taxes on wetlands maintained in their natural state• nontaxable profits from land sales to conservancy based organizations• establish performance /assurance bonds to mitigate any damages to coastal wetlands that occur during the

construction and/or operation of a business or industry; deposit is returned minus the actual or estimatedenvironmental costs

• trading of emission credits for industries

advanced placement environmental science · freshwater biomes runoff of precipitation from...

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