Energy Flow in Marine Ecosystems

Pg. 23

What are primary producers?

• Organisms need energy for growth, reproduction, & metabolic processes.• No organism can create energy, so obtain it from other sources

• Autotrophs (aka Primary Producers)• Plants, algae & some bacteria • get energy from sunlight or chemicals; convert into forms living cells

can use

• Primary producers• Essential to flow of energy through biosphere• store energy in forms convenient for organisms that eat

them • Example: algae get energy from sunlight, turn it into

nutrients that can be eaten & used for energy by animals such as a copepod

• Photosynthesis (6H2O + 6CO2 � C6H12O6 + 6O2)• Process used by most producers to obtain energy• Algae = main photosynthesizers freshwater & upper ocean • Photosynthetic bacteria (cyanobacteria) = important primary

producers in tidal flats & salt marshes.

How do organisms obtain energy in aphotic ecosystems?

• Biologists discovered ecosystems around volcanic vents in total darkness on the deep ocean floor

• Ecosystems are called “Hydrothermal vents”

• Deep-sea ecosystems depend on chemosynthetic primary producers

• Chemosynthesis - use of chemical energy to produce carbohydrates

• harness chemical energy from inorganic molecules (hydrogen sulfide)

How Do Consumers Obtain Energy & Nutrients?

• Heterotrophs (aka consumers) - Organisms that must acquire energy

from other organisms by ingesting it; classified by energy acquisition

• Herbivores - obtain energy & nutrients by eating plant leaves, roots, seeds, or fruits.

• Ex. Sea urchins, mussels, zooplankton

• Carnivores - kill & eat other animals

• Ex. Tuna, Sea snake, Octopus

• Omnivores - animals that eat a variety of different foods; i.e. plants & animals

• Ex. Blue crabs, sea otter

• Scavengers - animals that consume carcasses of other animals that were killed by

predators or died of other causes.

• Ex. hagfish

• Decomposers - feed by chemically breaking down organic matter.

• decay caused by decomposers is part of the process to produce detritus—small pieces of

dead & decaying plant & animal remains

• Ex. Bacteria

• Detritivores - feed on detritus particles; chew or grind them into smaller pieces;

routinely digest decomposers that live on, and in, detritus particles

• Ex. Sea cucumbers

How does energy flow through ecosystems?

• Energy flows through ecosystems in one-way stream• Energy source � primary producers � consumers

• Food chain: series of steps where organisms transfer energy by eating & being eaten

• Vary in length depending on ecosystem & organisms present

• Ex. Aquatic food chains:

• Primary producers = mixture of floating algae called phytoplankton & attached algae

• Primary consumers = small fishes that eat producers (ex. Flagfish)

• Secondary consumers = large fish (ex. largemouth bass) eat small fish

• Tertiary consumers = birds (ex. Anhinga) eat large fish

• Quaternary consumers = top predator (ex. Alligators) eat birds

• 4 steps in this chain, so top predator/carnivore is four steps removed from primary producer

Example from Everglades (aquatic food chain)

• Feeding relationships are more complicated than single, simple chain

• Many animals eat more than one kind of food (generalists)

• Food Web - network of feeding interactions within ecosystem

• Each path through a food web is a food chain

• A food web links all of the food chains in an ecosystem together

• Detritus pathway: • Most producers die without being eaten.

• decomposers convert dead material to detritus

• eaten by detritivores, such as crayfish, grass shrimp, & worms.

• Pig frogs, killifish, & other fishes eat the detritivores

• Decomposition process releases nutrients to be used by primary producers

• Without decomposers, nutrients would remain locked in dead organisms.

How does energy flow through

ecosystems?

What happens when Food Webs are disturbed?

• When disturbances to food webs happen, the effects can be dramatic.

• Example:

• All animals in Arctic food web depend directly or indirectly on shrimplike animals called krill.

• Recently, krill populations have dropped

• Given structure of food web, a drop in the krill population causes drops in populations of all other members