Marine Ecology 010. Ecology = the study of the interaction of organisms with their environments

Marine Ecology

010

Ecology = the study of the interaction of organisms with their environments.

It involves understanding biotic and abiotic factors influencing the distribution and abundance of living things.

Biotic Factors• Competitors

• Disease

• Predators

• Food availability

• Habitat availability

• Symbiotic relationships

Abiotic Factors• pH

• Temperature

• Weather conditions

• Water availability

• Chemical composition of environment

• nitrates, phosphates, ammonia, O2, pollution

The word "ecology" coined from Greek word "oikos", which means "house" or "place to live”.

• population growth

• competition between species

• symbiotic relationships

• trophic (=feeding) relationships

• origin of biological diversity

• interaction with the physical environment

Energy Flow & Nutrient CycleEnergy Flow & Nutrient Cycle

Food ChainsFood Chains

• Artificial devices to illustrate energy flow from one trophic level to another

• Trophic Levels: groups of organisms that obtain their energy in a similar manner

• Total number of levels in a food chain depends upon locality and number of species

• Highest trophic levels occupied by adult animals with no predators of their own

• Secondary Production: total amount of biomass produced in all higher trophic levels

Food ChainsFood Chains

NutrientsNutrients• Inorganic nutrients incorporated

into cells during photosynthesis- e.g. N, P, C, S

• Cyclic flow in food chains

• Decomposers release inorganic forms that become available to autotrophs again

EnergyEnergy• Non-cyclic, unidirectional flow• Losses at each transfer from one

trophic level to another- Losses as heat from respiration- Inefficiencies in processing

• Total energy declines from one transfer to another- Limits number of trophic levels

Energy Flow

Primary Producer

Primary Consumer

Secondary Consumer

Tertiary Consumer

Food Chain

Decomposer

zooplankton larval fish

fish

fungi

Energy Flow through an EcosystemEnergy Flow through an Ecosystem

heat heatheat

phytoplankton

sun

water

Nutrients

Transfer EfficienciesTransfer Efficiencies• Efficiency of energy transfer called

transfer efficiency

• Units are energy or biomass

Et = Pt

Pt-1

Pt = annual production at level t

Pt-1 = annual production at t-1

Transfer Efficiency ExampleTransfer Efficiency Example• Net primary production = 150 g C/m2/yr• Herbivorous copepod production = 25 g C/m2/yr

• Typical transfer efficiency ranges*Level 1-2 ~20%*Levels 2-3, …: ~10%

Et = Pt

Pt-1

= Pcopepods

Pphytoplankton

= 25 = 0.17150

Primary producers

Tertiary consumers

Secondary consumers

Primary consumers

1,000 J

10% efficiency

Deposit feeders, filter feeders, grazers

1,000,000 J sunlight

10,000 J

algae, seagrass, cyanobacteria, phytoplankton

100 J

1st order carnivores

10 J

2nd order carnivores

Feces

Growth

CellularRespiration

Food WebsFood Webs

• Food chains don’t exist in real ecosystems

• Almost all organisms are eaten by more than one predator

• Food webs reflect these multiple and shifting interactions

Antarctic Food Web

Some Feeding TypesSome Feeding Types

Many species don’t fit into convenient categories• Algal Grazers and Browsers• Suspension Feeding• Filter Feeding• Deposit Feeding• Benthic Animal Predators• Plankton Pickers• Corallivores• Piscivores• Omnivores• Detritivores• Scavengers• Parasites• Cannibals• Ontogenetic dietary shifts

Recycling: The Microbial LoopRecycling: The Microbial Loop

• All organisms leak and excrete dissolved organic carbon (DOC)

• Bacteria can utilize DOC• Bacteria abundant in the euphotic

zone (~5 million/ml)• Numbers controlled by grazing due to

nanoplankton• Increases food web efficiency

Solar Energy

Microbial Loop

CO2

nutrients

Phytoplankton

Herbivores

Planktivores

Piscivores

DOC

Bacteria Nanoplankton(protozoans)

Keystone Species

A species whose presence in the community exerts a significant influence on the structure of that community.

Keystone predator hypothesis - predation by certain keystone predators is important in maintaining community diversity.

Paine’s study on Pisaster and blue mussels

Kelp Forests

Keystone Species

Keystone Species

Keystone SpeciesKeystone Species

Algal turf farming by the Pacific Gregory (Stegastes fasciolatus)

An Ecological Mystery

An Ecological MysteryAn Ecological Mystery• Long-term study of sea otter populations

along the Aleutians and Western Alaska• 1970s: sea otter populations healthy and

expanding• 1990s: some populations of sea otters

were declining• Possibly due to migration rather than

mortality• 1993: 800km area in Aleutians surveyed

- Sea otter population reduced by 50%

Vanishing Sea OttersVanishing Sea Otters

• 1997: surveys repeated• Sea otter populations had declines by 90%

- 1970: ~53,000 sea otters in survey area- 1997: ~6,000 sea otters

• Why?- Reproductive failure?- Starvation, pollution disease?

Cause of the DeclineCause of the Decline• 1991: one researcher observed an orca

eating a sea otter• Sea lions and seals are normal prey for

orcas• Clam Lagoon inaccessible to orcas- no

decline• Decline in usual prey led to a switch to sea

otters• As few as 4 orcas feeding on otters could

account on the impact- Single orca could consume 1,825 otters/year

Ecological Succession

The progressive change in the species composition of an ecosystem.

Ecological Succession

Climax StageClimax Stage

New Bare SubstrateNew Bare Substrate

Colonizing StageColonizing Stage

Successionist StageSuccessionist Stage

PRIMARY SECONDARY

Growth occurs on newly exposed surfaces where no soil exists

Ex. Surfaces of volcanic eruptions

Growth occurring after a disturbance changes a community without removing the soil

2 types of succession

• For example, new land created by a volcanic eruption is colonized by various living organisms

• Disturbances responsible can include cleared and plowed land, burned woodlands

Mount St. Helens

prior 1980

Mount St. Helens

May 18, 1980

Sep. 24, 1980

Mount St. Helens

Fireweed 1980 after eruption

2004

2012

Hanauma Bay Tuff Ring(shield volcano)

Succession after Volcanic Eruption

What organisms would appear first?

How do organisms arrive, i.e., methods for dispersal?

Volcanic eruption creates sterile environment

Mechanisms of Succession

Facilitation

Inhibition

Tolerance

Early species improve habitat.

Ex. Early marine colonists provide a substrate conducive for settling of later arriving species.

As resources become scarce due to depletion and competition, species capable of tolerating the lowest resource levels will survive.

Competition for space, nutrients and light; allopathic chemicals.

First arrivals take precedence.

r & K Selected Species

Pioneer species- 1st species to colonize a newly disturbed area

r selected

Late successional species

K selected

low competitive abilityshort life spanhigh growth rate

higher maternal investment per offspringlow reproductive output

high reproductive output

slow growth ratelong life spanhigh competitive ability

r & K refer to parameters in logistic growth

equation

Ecological Succession on a Coral Reef

Successional Models and their Impacts

Case 1: No Disturbance (Competitive Exclusion Model)

Case 2: Occasional Strong Disturbance (Intermediate Disturbance Model)

Case 3: Constant Strong Disturbance (Colonial Model)

Case 1: No Disturbance(Competitive Exclusion Model)

• As the reef becomes complex, organisms compete for space.• Dominant organism outcompetes other species.• Occurs in stable environments. • Results in low species diversity.• Highly protected patch reefs within lagoons or protected bays• Deeper water

Case 2: Occasional Strong Disturbance(Intermediate Disturbance Model)

• Storms and hurricanes allow for other species to move in

• Dominant species would not be allowed to reach competitive exclusion

• After each disturbance have a recovery period

• Area of high diversity

Case 3: Constant Strong Disturbance(Colonial Model)

• Constant exposure to disturbance• Shallow environment• High turnover of species• r-selected species

Reef

Case 3

Case 2

Case 1Deep reef slope

Reef slope beneath reef crest

Near reef crest

Ecological Succession on a Coral ReefThe Big Island

Ecological Succession on a Coral Reef

Ecological Succession on a Coral Reef

Ecological Succession on a Coral Reef

Ecological Succession on a Coral Reef

Ecological Succession on a Coral Reef

Ecological Succession on a Coral Reef

Ecological Succession on a Coral Reef

Successional Models and their Impacts

Successional Models and their Impacts