L2 - Introduction to Marine Ecology

Question 1

What is marine ecology?

Scientific method

Scales of study

Major divisions of the marine environment

Comparison of marine & terrestrial ecosystems

Answer 1

Question 2

“…the study of the principles which govern temporal & spatial patterns for assemblages of organisms.” (Fenchel 1987)

“…the study of the relationship between organisms and their physical and biological environments.” (Ehrlich & Roughgarden 1987)

Answer 2

Intrinsic value

Why study ecology?

But what we tell the funding agencies is that …..

Effective management requires:

Knowledge about how ecosystems function

ie. What processes govern the spatial and temporal variability in organism abundance

Then (maybe)….

Isolate natural variability from anthropogenic disturbance

Prediction

Question 3

Scientific method

Answer 3

Scales of Study: The Ecological Hierarchy

Biosphere > Ecosystem

(Global warming will impact Ecosystems through acidification, changing nutrient cycles)

Ecosystem > Community

Acidification and Nutrient cycle changes in the above cascades down to the:

Population

Individual

May affect population numbersd, restructure communities and alter the ecosystem

Question 4

Biosphere

Interaction between environment and life on earth

Global carbon cycles, effects of climate change on biosphere

Dark green = photosynthesis and plant biomass

ocean bright colours represent phytoplankton biomass

annual cycle of biosphere breathing

Answer 4

Ecosystem

Question 5

Assemblage of interdependent biological communities in a single geographic area

Boundaries set by researcher

Quantify environmental effects on energy flow

Not interested in individual performance

Interest is how nutrience and energy flows through system

example: oceanic ecosystem

interested in the relationship between how much solar energy inout from sun and how much primary production as a result.

Variations in cloud cover and solar radiance affecting the amount of fixed carbon

(not looking at how many individual species of phytoplankton)

The role of bacteria and decomposition and the regeneration of nutrience

LARGER SCALE QUESTIONS

ECO SYSTEM CONSTRAINTS ON PRODUCTION?

HOW DOES SOLAR RADIATION AFFECT FIXED CARBON?

CONSEQUENCES FOR HIGHER TROPHIC LEVELS?

Answer 5

Question 6

Assemblage of interacting species

Studies focus on interspecific interactions

(most ecologists work at this scale)

Dropping down through the ecological heriechy the unit of scale becomes smaller and the focus and questions become different.

Question 7

Interested in interactions between individuals

Predation (+ -)

Benefit for one and negative for prey

Parasitism (+ -)

Benefit for parasite and negative for host

Competition (+ - or - -)

Positive for winner (gain territory/food)

Negative for Loser

Or cost of interaction a negative for both participants if damage done

Territoriality (+ - or - -)

Winner positive

Loser negative

Neagtive for both if damage inflicted

Commensalism (+ 0)

an association between two organisms in which one benefits and the other derives neither benefit nor harm.

Mutualism (+ +)

Both positive effect for other

Question 8

Community Studies

Address processes affecting species distribution and abundance (ie community composition)

Includes

Dispersal

Interspecific competition

Predation

Disease & parasitism

Disturbance

Facilitation

Example: Removing Grazing Community

-Green grass a result of opertunistic algae in the absence of grazers

Question 9

Population

A group of individuals that are affected by the same environment and are relatively unconnected with other populations of the same species - A management unit.

Important in fisheries management as when we remove biomass or remove individuals from a population we’re adding mortality to a system.. If that mortality is not compensated through new individuals arriving through emmigration/immigration? or more critically through recuitment to that population then that population can crash and abundance will can down.

Answer 9

Question 10

Individual

These studies are done at much smaller scales

• Physiologically independent from other organisms
• Studies at this scale are concern with organism growth & behavioura

Question 11

Ecological cascade

Biosphere all the way to individual and we begin to think about top down affects which is occuring at the scale higher which cascades back down but there is also bottom up affects where individual performance (extra nutrience in system) may cause good recruitment years which affect populations in communities and eco systems.

TIERS ARE NOT ISOLATED FROM THOSE ABOVE AND BELOW IT, THEY ARE CONNECTED THROUGH THESE INTERFACES.

Question 12

55 % of the pelagic environment by volume is deeper than 2000 m

80 % of the benthic environment by area is deeper than 2000 m

Ocean divided in two ways

Pelagic = Water Collumn

Benthic = Sea Bed

Answer 12

Epipelagic (first 200m)

• The depth of light penetration
• Where most of the primary production is occuring
• Average depth of ocean is 7000m deep, all the biomass in the ocean is supported by the top 100-200m of water where organic matter is being fixed

Mesopelagic (200-1000m)

Depth of permanent thermocline occurs. Where seperation of water in contact with atmosphere seasonally/regularly is seperated from the top of the atmosphere.

As we move near shore to offshore, envrionmental variability decreases (salinity, temp, nutrient availability)

The closer to land, the more terrestrial infuence and climatic variations

Intertidal zone = Extreme climatic variations

Offshore: Less environmental variability.

Deep ocean: Environmental variability decreases further

Surface area: Day night variance

The further and deeper you go.. the less environmental variance

Question 13

Neritic = Near Shore

The distinction between these two points is generally made at the continental shelf where the water depth is at around 200m. This is where the seabed begins to get deeper very very quickly.

Neritic Zone: Water influenced by run off from the continent

(Fresh water from rivers, sediments, nutrience)

Lots of Primary Production occuring, way more productive than oceanic environment. Sub division made because of influence of terrestrial run off in the near shore environment.

Question 14

Oceanic Zone

Sufficently far offshore where the effects of land run off don’t impact upon the ecology or systems that are working there.

Oceanic zones further sub divided by depths

(WILL NOT COME UP IN TEST)

Question 16

Light & Temperature

Question 17

Marine vs Terrestrial Ecosystems

Water provides buoyancy

Planktonic life forms, no need for structural components

Narrow temperature range

Dispersal medium for organisms, eggs & larvae

Universal solvent

Plants acquire nutrients directly from the water

Dilutes & disperses metabolic wastes & pollutants

Third habitat dimension (water column) supports many organisms not found on land

Water is wet air is dry!

Answer 17

Obvious statement

Water: wet

Air: dry

Fundamental shift in terms of the ammount of stuff you need to survive in that environment

Surviving in terrestrial very difficult

Surviving in water easier

High thermal capacity but low temperature range

Organisms don’t have to worry to much about heating

Question 18

Number of higher animal taxa (endemic)

Answer 18

Marine Vs Terrestrial

Terrestrial

Primary production is dominated by large (carbon fixing) autotrophs

(trees, grasses, shrubs)

Consumed by large warm blooded herbivores

Consumed by large warm blooded predators

Marine

Predominantly based on microscopic autotrophs

(small phytoplankton)

Eaten my microscopic herbivores

(zoo plankton)

Eaten by Herring

Eaten by squid and higher order predators

Question 19

Marine vs Terrestrial Production

Marine

• Primary production is carried out by small phytoplankton
• Phytolankton are high in protein
• Majority of production is readily consumed and digested by herbivores
• Primary production = 50-350 g C m-2 a-1
• P/B ratio = 100-300
• High secondary production (cold-blooded, buoyant fluid, high reproductive output)

Terrestrial

• Primary producers are large trees & grasses
• Terrestrial plants are high in carbohydrates & cellulose
• Most production enters the food chain via decomposition cycles
• Primary production = 0-3900 g C m-2 a-1
• P/B ratio = 0.5-2.0 a large fraction of production is used to maintain the high biomass
• Lower secondary production (warm blooded, gravity, parental care)

Answer 19

-Phytoplankton very high in protein

(They don’t need structual elements so just about all of their form is highly nutritional)

-Terrestiral plants high in carbohydrates and cellulose

(Alot of non-nutritional material for example in grasses and also in trees and shrubs such as bark)

Question 20

Marine

Zooplankton cold blooded

Buoyant so little energy expenditure

High reproductive output

Terrestrial (herbivores)

Warm blooded

Gravity to fight (energy expenditure)

Parental care (energy expenditure)

Costs mean that energy can’t be cast up the food chain

Oceans contribute 35 % of the World’s plant production

but accounts for 80 % of the animal biomass production

Primary production turns over very fast and its highly nutritional and its going into animal production that has high reproductive output with low cost.

Although more carbon fixed in terrestrial systems, alot of carbon unavailable to the animal production as its being respired to support the structure and alot of it is indigestible and the animal production is warm blooded and its not using it for production and growth.