Energy Flow in Marine Ecosystems Pg. 23
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