Biomes and Aquatic Ecosystems Study Notes

3.1 How Does Climate Affect the Nature and Locations of Biomes? (1 of 2)

  • Biomes: Large terrestrial regions characterized by different type of climate and dominant plant life

  • Biome distribution is based on:

    • Precipitation

    • Average temperature

    • Geography

    • Nutrient availability

    • Soil

    • Altitude

    • Latitude (distance from equator)

  • Latitudinal bands:

    • Tropical: 0^{\circ}-30^{\circ}

    • Temperate: 30^{\circ}-60^{\circ}

    • Polar: 60^{\circ}-90^{\circ}

  • These factors determine the plant and animal species adapted to a biome, which further characterize a biome

3.1 How Does Climate Affect the Nature and Locations of Biomes? (2 of 2)

  • Natural capital: natural resources and ecosystem services that keep us and other species alive and support our economies

  • Average precipitation and average temperature, acting together as limiting factors over a long time, help to determine the type of desert, grassland, or forest in any particular area, and thus the types of plants, animals, and decomposers found in that area (assuming it has not been disturbed by human activities).

Deserts

  • Desert – annual precipitation low and scattered unevenly throughout the year

  • Desert ecosystems vulnerable to disruption:

    • Slow plant growth and low species diversity

    • Slow nutrient cycling

    • Low bacterial activity in soil and very little water

    • Takes decades to recover after disturbances

Three Types of Deserts

  • Tropical: dry most of the year, few plants, hard windblown surface with rocks and sand

  • Temperate: high temp in summer and low in winter, more precipitation than tropical, drought-resistant shrubs, cacti and succulents

  • Cold: cold winters, warm summers, low precipitation

Desert Survival Adaptations

  • Plant water conservation – Dormancy – Deep roots – Storing water in leaves – Waxy leaves reduce water loss – Open pores only at night

  • Desert animal adaptations – Hiding in cool burrows or rocky crevices by day – Dormancy – Camels drink massive amounts of water and store – Reptiles’ thick outer coverings minimize water loss

Grasslands

  • Grasslands exist in continent interiors – Areas too moist for deserts but too dry for forests

  • Grasslands are maintained by fire and large grazing herbivores – both prevent shrubs and trees from taking over – Fire helps grasslands: replaces nutrients, puts carbon in the soil, improves water cycling, removes invasive plants, increases the nutritional quality and taste of grass for herbivores

  • Cold winters and hot dry summers make deep and fertile soil ideal for growing crops and grazing cattle.

Three Types of Grasslands

  • Tropical savanna: scattered trees, warm year-round temperatures, alternating dry and wet seasons, grazing and browsing animals

  • Temperate grassland: very cold winter, hot and dry summer, sparse and uneven rainfall, Tallgrass prairies, Short-grass prairies, fertile topsoil, often converted to farmland

  • Arctic Tundra: cold, treeless plains, cold winds, covered in ice and snow, few hours of sunlight in winter and most precipitation is snow, low-growing plants to conserve heat, permafrost (underground soil that stays frozen), most growth in short summer, Animals have thick fur

Chaparral: A Dry, Temperate Biome

  • Occur in coastal regions that border deserts

  • Dense growths of low growing, evergreen shrubs

  • Some small trees with leathery leaves

  • Thin soil

  • Adapted to and maintained by occasional fires

Forests

  • Forests – lands dominated by trees

  • Mountains play an important ecological role in forests – Mountains – steep or high elevation lands – provide vital ecosystem services

  • Large portion of world’s forests – Islands of biodiversity – Habitats for endemic species – Help regulate the earth’s climate – Major storehouses of water

Three Types of Forests

  • Tropical rainforests: Most productive biome, hot and high moisture air, rapid recycling of scarce soil nutrients due to nutrients rapidly taken up by plants, little vegetation on the floor, plants use animals for pollination, high decomposition rates, rapid deforestation

  • Temperate deciduous forests: Cooler temperatures, abundant moisture, broadleaf deciduous trees, slow rate of decomposition, four seasons, deciduous plants drop leaves, rich soil, easiest to restore

  • Cold (northern) coniferous forest: also called boreal forests or taigas, south of arctic tundra, long cold winters and short summers, coniferous trees, low levels of diversity, slow decomposition due to low temps, thin/nutrient poor/acidic soil

  • Coastal coniferous forest: Also called temperate rain forests, found in scattered coastal regions, ample rainfall and moisture from fog, evergreen coniferous trees

Humans Have Disturbed Much of the Earth’s Land

  • About 60% of world’s major terrestrial ecosystems being degraded or used unsustainably

  • The human ecological footprint is spreading across the globe

Shifting Biomes

  • Biomes are constantly changing and shifting location on Earth due to climate change

  • Ex: warming climate will shift boreal forests further north as tundra permafrost soil melts & lower latitudes become too warm for aspen & spruce

  • Historically, non-human impacts affect climate change – changes in earth’s tilt, atmospheric composition, volcanic activity, asteroid/ comet hits

  • Humans are not a major driver of climate change – Example: Desertification – expansion of deserts or degradation of land that was once arable

Core Case Study: Coral Reefs

  • Coral reefs among world’s oldest, most diverse, and most productive ecosystems

  • Form in clear, warm coastal waters in tropical areas

  • Tiny animals (polyps) and single-celled algae have a mutualistic relationship

  • Polyps secrete calcium carbonate shells, which become coral reefs

  • Marine equivalent of tropical rainforests

  • Provide important ecological and economic services – Natural barrier to protect coastlines – Habitat, food, or spawning grounds for one-quarter to one-third of ocean’s organisms

  • Vulnerable to damage – Soil runoff – Climate change increasing ocean temperature – Increasing ocean acidity

  • Reefs are being destroyed and damaged worldwide

  • Ocean acidification – Oceans absorb CO2 – CO2 reacts with ocean water to form a weak acid that decreases levels of carbonate ions (CO_3^{2-}) needed to form coral

  • This bleached coral has lost most of its algae because of changes in the environment such as warming of the waters and deposition of sediments.

4.1 What Is the General Nature of Aquatic Systems?

  • Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth’s surface

  • Saltwater covers 71\% of earth’s surface

  • Freshwater occupies 2\%

  • Distribution of organisms determined largely by salinity – How much salt there is in a body of water, determines which species can survive & usability for drinking

  • Other key factors determining aquatic biodiversity – Temperature: warmer water holds less dissolved O2 so it can support fewer organisms – Dissolved oxygen content: Determines which plants & organisms can survive – Availability of food – Depth and Turbidity: Access to light and nutrients necessary for photosynthesis

Aquatic Life Zones and Species

  • Aquatic life zones – Saltwater life zones (marine life zones) ▪ Examples: oceans, estuaries, coasts, coral reefs, and mangrove forests – Freshwater life zones ▪ Examples: lakes, rivers, streams, and inland wetlands

  • Plankton–drifting – Phytoplankton: Primary producers for most aquatic food webs – Ultraplankton: Tiny photosynthetic bacteria – Zooplankton: Secondary consumers

  • Nekton: Strong swimmers – fish, turtles, whales

  • Benthos: Bottom dwellers – oysters, sea stars, clams, lobsters, crabs – Decomposers – Mostly bacteria

Oceans Provide Vital Ecosystem and Economic Services

  • Saltwater ecosystems provide major ecosystem and economic services

  • Oceans produce more than half of oxygen we breathe – Provide most of the rain that sustains water supply

  • Irreplaceable reservoirs of biodiversity

  • 110 million tons of seafood harvested per year

Three Major Life Zones of the Ocean

  • Coastal zone – Warm, nutrient rich, shallow water – Extends from land to edge of continental shelf – Makes up less than 10% of world ocean area – Contains 90% of all marine species

  • Open sea

  • Ocean bottom

  • Available light and temperature varies with depth

Rocky and Sandy Shores

  • Intertidal zone – Area of shore between high and low tides

  • Organisms must survive with daily salinity and moisture changes (specialized niches)

  • Rocky shores – Pounded by waves

  • Barrier beaches (sandy shores) – Most organisms burrow, dig, or tunnel in sand

Open Sea and the Ocean Floor

  • Three vertical zones of the open sea (pelagic zone):

    • Euphotic zone ▪ Phytoplankton ▪ Nutrient levels low ▪ Dissolved oxygen levels high ▪ Upwelling brings nutrients from below

    • Bathyal zone ▪ Dimly lit middle zone ▪ Zooplankton and smaller fishes

    • Abyssal zone ▪ Dark and cold ▪ High levels of nutrients ▪ Little dissolved oxygen ▪ Deposit feeders ▪ Filter feeders

  • NPP low in the open sea – Except in upwelling areas

  • A shore upwelling occurs when deep, cool, nutrient-rich waters are drawn up to replace surface water moved away from a steep coast by wind flowing along the coast toward the equator

4.3 How Have Human Activities Affected Marine Ecosystems?

  • Human activities threaten aquatic biodiversity – disrupt ecosystem and economic services provided by saltwater systems

  • Climate change and ocean acidification are largest threats

  • Coastal development – destroys or degraded coastal habitats

  • Overfishing

  • Destruction of ocean bottom habitats

  • Runoff of pollutants

  • Pollution from ships and tanker spills

  • Introduction of invasive species

Critical Concept in Sustainability: The Importance of Wetlands

  • Wetlands are areas that are saturated with water all or part of the year

  • Have standing shallow water with emergent vegetation

  • Contain communities of plants and animals that have adapted to continuously wet conditions

  • Highly productive because of available nutrients

  • Freshwater wetlands include – Swamps – Marshes – Bogs – Fens – Prairie potholes

  • Saltwater wetlands include – Estuaries: Aquatic zone where river meets the sea – Mangrove swamps: have roots that curve up from the mud and water to obtain oxygen from the air, wildlife habitats – Coastal marshes

  • Both provide many ecosystems services – help maintain water quality in tropical coastal zones by filtering toxic pollutants, excess plant nutrients, and sediments, and by absorbing other pollutants – provide food, habitats, and nursery sites for a variety of species – reduce storm damage and coastal erosion by absorbing waves and storing excess water by storms and tsunamis

4.4 Why Are Freshwater Ecosystems Important?

  • Freshwater ecosystems – Provide major ecosystem and economic services – Irreplaceable reservoirs of biodiversity

  • Water Stands in Some Freshwater Systems and Flows in Others – Standing (lentic) surface water ▪ Lakes, Ponds, Inland wetlands – Flowing (lotic) systems of freshwater ▪ Streams, Rivers

Water Stands in Some Freshwater Systems and Flows in Others

  • Lakes have four life zones defined by depth and distance from shore – Littoral zone: Shallow water with emergent plants; high biodiversity – Limnetic zone: sunlight area away from shore; main photosynthetic zone – Profundal zone: Too deep for photosynthesis, low oxygen levels – Benthic zone: Lake bottom, nutrient-rich sediment

Some Lakes Have More Nutrients Than Others

  • Oligotrophic lakes – Low levels of nutrients and low NPP – Very clear water

  • Eutrophic lakes – High levels of nutrients and high NPP – Shallow, murky water – Covered in algae

  • Cultural eutrophication of lakes from human input of nutrients

Freshwater Streams and Rivers Carry Large Volumes of Water (1 of 2)

  • Downward flow of surface water and groundwater from mountain highlands

  • Three aquatic life zones – Source zone: Shallow, cold, clear, swiftly flowing streams ▪ High dissolved oxygen, Nutrients come from organic matter – Transition zone: Wider, deeper, warmer streams ▪ More turbid, with less dissolved oxygen – Floodplain zone: Wide, deep rivers that flow across valleys ▪ Higher temperatures, less dissolved oxygen

4.5 How Have Human Activities Affected Freshwater Ecosystems?

  • Human activities threaten biodiversity and disrupt ecosystem and economic services provided by freshwater lakes, rivers, and wetlands – Dams and canals restrict the flows of rivers – 40% of the world’s largest rivers – Flood-control destroys aquatic habitats and alters wetlands – Cities and farms pollute water – Many wetlands have been drained for human purposes