Chapter 6: Ecosystems Chapter 6: Ecosystems and Ecosystem and Ecosystem ManagementManagement

Watershed

• The whole region or extent of land which contributes to the supply of a river, lake or ocean.

Our WatershedElm Fork Trinity Watershed

Bioindicator• The presence, condition, and numbers

of the types of fish, insects, algae, and plants that provide accurate information about the health of a specific body of water.

• By tracking changes, water systems can be identified that have undergone change due to stress placed upon the environment.

BioindicatorsSome bugs can't tolerate water

pollution,

We call these bugs pollution sensitive. 

• 12 points each• Mayfly

CaddisflyWater PennyPlanarianDobsonflyStonefly

Other bugs are less sensitive to pollution...

• Eight points each• Crayfish              Dragonfly

Mussel Riffle Beetle AdultWhirligig DamselflyClam FishflySowbug Riffle Beetle Larva             Alderfly DamselflyCraneflyDragonflyMussel

Some bugs can live in any kind of water.  We call these bugs pollution tolerant.

• Four points each• Leech

MidgeAquatic WormGilled SnailBlack FlyLunged Snail

Osteichthyes

The Clean Water Act (CWA) was based on several laws, (Federal Water Pollution Control Act of 1972, Clean Water Act of 1977, and the Water Quality Act of 1987) and was created to identify and reduce pollution caused by industrial, government, and agricultural facilities.

The Act’s objective is to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters through the use of credible bioindicators to evaluate the health of a body of water.

EPA Case Study

The Ecosystem: Sustaining Life on Earth

• Sustaining life on Earth requires more than individuals

• Life is sustained by interactions of many organisms functioning together in ecosystems– Physical and chemical environments

Basic Characteristics of Ecosystems

• Ecosystems have several fundamental characteristics

• StructureMade up of two major parts: – Biotic or living (ecological community) – Abiotic or non living (physical chemical

environment)

Basic Characteristics of Ecosystems

• Processes– Cycling of chemical elements and

flow of energy

• Change– Undergo development through

succession

Basic Characteristics of Ecosystems

• For complete recycling of chemical elements to take place, several species must interact.– Photosynthetic organisms produce

sugar from carbon dioxide and water– From sugar and inorganic compound

they make other organic compounds (protein, woody tissue)

– Need decomposers to get back to inorganic compounds

Basic Characteristics of Ecosystems

• At its simplest a community will have– At least one species that is a

producer– Another species that is a decomposer– Plus a fluid medium

Ecological Communities

• Ecological community defined in two ways– A set of interacting species found in

the same place and functioning together to maintain life.

– Operational def= all the species found in an area, whether or not they interact.

Food Chains

• Energy, chemicals and some compounds are transferred from creature to creature along food chains (food webs).– The linkage of who feeds on whom

• Grouped by trophic level– # of feeding levels away from original

source of energy

Trophic Levels

• First trophic level– Use energy from the sun and carbon

dioxide from the air to photosynthesizes– Green plants, algae and certain bacteria– Called autotrophs

• Second trophic level– Organisms that feed on autotrophs– Called herbivores

Trophic Levels

• Third trophic level– Feed directly on herbivores– Called carnivores (meat eaters)

• Fourth trophic level– Carnivores that feed on third-level

carnivores

• Decomposers- feed on waste and dead organisms of all trophic levels

A Terrestrial Food Chain

• Example: North American Temperate Woodland

• 1st level- grasses, herbs and trees• 2nd level- mice, pine borer and deer• 3rd level- foxes, wolves, hawks and

other predatory birds and insects• 4th level- humans

An Oceanic Food Chain

• Tend to have more trophic levels• 1st level- planktonic algae and

planktonic bacteria• 2nd level- zooplankton and some fish• 3rd level- fish and invertebrates feed

on herbivores, baleen whales• 4th+ levels- killer whales, predatory

fish

The Food Web of the Harp Seal

• Food webs are complex because most species feed on several trophic levels.

• Harp seal (shown at 5th level)– Feeds on flatfish (4th level)– But also feed on foods from 2nd – 4th – A species that feeds on several levels

placed in a category one above the highest level it feeds on.

Community Level Interactions

• Indirect and more complicated community wide affects species have on one another.

• Sea otter of the Pacific Ocean– Came close to extinction because of over

hunting for fur– Feed on shellfish (abalone, sea urchins)– Where sea otters abundant kelp beds

abundant and few sea urchins – Otters affects the abundance of kelp

• Sea otters have community level effect– Where more kelp is present more

habitat for many species• Keystone species

– A species that has a large effect on its community or ecosystem

• Holistic view– Ecological community is more than the

sum of its parts

Community Level Interactions

How do you know when you have found an ecosystem?

• An ecosystem is the minimal entity that has the properties required to sustain life.

• Vary greatly in structural complexity and clarity of their boundaries.

• Differ is size, composition, proportion of non-biological constituents and degree of variation in time and space.

Watershed

• Watershed– Commonly used practical delineation

of the boundary of an ecosystem– Determined by topography– United in terms of chemical cycling

Ecosystem Management

• Ecosystem can be natural or artificial

• Can also be managed– Agriculture– Wildlife preserves

• Ecosystem concepts lies at the heart of the management of natural resources.