Transcript No Slide Title - Penn State York

Marine Ecosystem Structure
and Organisms
• Ecosystem = A biotic community and its
interaction with the abiotic environment.
• Flow of Energy and Cycling of Mass.
• Population & Community Controls.
• Marine Environment Zonation.
• Plankton Community
Flow of energy and
cycling of mass.
All ecosystems require
energy inputs and a supply
of carbon to create its living
mass (biomass)
Primary Producers refer to
organisms whose biomass is
the ultimate source of energy
and carbon for all other biota
in an ecosystem; they are
always autotrophs
(= organisms that use energy
to convert inorganic carbon
(CO2) and nutrients to the
organic matter of biomass;
typically plants.
Solar radiation supplies the
energy for photosynthesis.
Some autotrophs use
energy rich minerals like
sulfur as their energy
source for chemosynthesis
Organic matter represents energy in a
chemical form. It is converted to other
forms of energy, CO2 and nutrients in
the process of respiration. Even
plants respire in the dark.
Energy is ultimately lost
to space as heat, but the
CO2 and nutrients get
reused, or cycled, within
the ecosystem; hence
energy flows and mass
cycles in ecosystems.
Heterotrophs are all organisms,
including bacteria, that solely depend on
eating organic matter (dead or living) for
energy and biomass carbon.
When heterotrophs eat other living
organisms they are called consumers.
When they eat dead organic matter
(detritus) they are called decomposers.
Generation of CO2 and mineral nutrients
as respiration byproducts is a process
called remineralization or nutrient
regeneration.
Net Primary Productivity =
All the photosynthetic/chemosynthetic production of
organic carbon minus the respiration of primary producers
when they are in the dark.
= (Gross Primary Productivity – Respiration)
Chlorophyll a is the
primary light
harvesting pigment
involved in
converting light
energy to chemical
energy during
photosynthesis.
It is located in cell
structures called
chloroplasts, as seen
in this diatom cell.
Chlorophyll a
content in seawater is
a good estimate of
phytoplankton
biomass.
Global estimates of chlorophyll content measured by satellite.
Note, where nutrients are found so are high levels of phytoplankton.
Energy flows up through a hierarchy of different feeding groups, called
trophic levels, within biotic communities. Each higher trophic level
looses 90% of the lower levels available energy, so there is less total
biomass in progressively higher trophic levels; hence trophic pyramid.
Typically, more small guys than big guys and they grow faster.
Simple linear links between prey and predators of progressively higher
trophic levels is called a food chain. Food webs include all possible
feeding relationships, which are typically more complex, yet reality.
Ecological Terms
Population = group of individual organisms of the same
species residing in a specific area.
Community = many populations interacting in a habitat.
Habitat = where a population is physically located (address).
Niche = what the population does; its function or role (job).
Species richness = numbers of species in a community.
Species diversity = combines in a single index the richness
and evenness of population distributions.
Physical-Chemical Factors
• An organism must live within its tolerance range for all of physical and
chemical factors (e.g. temperature and nutrients)
• An organism has an optimum value within its tolerance range for each factor.
• The factor provided at a level below or in excess of an organisms tolerance
range will harm the organism; we call this the limiting factor.
• What are best conditions for one organisms may not be the case for other
organisms. Some organisms have strategies for coping with conditions that
we humans consider extreme (limiting to our survival).
• What are the important physical and chemical factors that can limit growth?
Physical-Chemical Factors
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Temperature (ectotherms versus endotherms)
Nutrients (nitrogen and phosphate)
Salinity
Dissolved Gases
Acid-Base Balance (pH)
Hydrostatic Pressure
Light (not just for plants; UV light is harmful)
Harsh conditions, i.e. extreme
physical and chemical factors,
favor lower species diversity.
e.g. This deep-sea environment
Mild conditions, i.e. more
optimal physical and
chemical factors, favor
higher species diversity.
e.g. coral reef environment
Population & Community Controls
• Physical & Chemical Factors (must be tolerant of all)
• Biological Factors:
– Competition
• Intraspecific (within same population)
• Interspecific (between different populations)
– Predation
• Co-dependence of predator and prey
• Balanced state confers community stability
– Disease (parasites)
• Impacts weakened/stressed populations
• May counteract imbalances (overpopulation of a species)
• Disturbance (physical or biological in nature)
Consider these two species of barnacles in a rocky intertidal
zone community. Tolerance of desiccation and competition
for space and prey are important in maintaining their
intertidal location. Similar interactions explain the zone of
the brown seaweed, Fucus. Disturbance or predation may
create opportunities for rapid colonizers of open space.
Disturbance:
– Creates new habitat; thereby opens new niches for other organisms.
– The stepwise replacement of one group of organisms in a community with
another over time is called succession. The process may be seasonal.
– Succession after disturbance may ultimately lead to a stable community, called
a climax community that remains until the next disturbance.
Predation as a
disturbance:
Predators may
remove the
dominant species.
Such local
disturbance opens
habitat for
organisms of an
earlier succession
stage.
Marine Environment Zonation
• Pelagic Zones: water environment
– By light
– By depth (pressure and temperature changes)
• Benthic Zones: bottom environment
– By depth
• Both zones have many different habitat types;
therefore, different communities within each.
Life in the deep dark
ocean (>600m) has
evolved special
means of
communication,
finding mates &
detecting prey:
Echolocation,
electrosensing,
bioluminescence,
and smell are four
mechanisms for
getting around in the
dark.