Summary
Summary Marine Systems
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Exam: online modules + scientific articles + tutorialsOceans cover 71%
Terrigenous => sediment eroded from land
Dominant elements dissolved in water = Na & Cl
Average salinity sea water = 35%o
(bi)carbonates buffer the ocean
Poles
High density, cold air sinks high pressure zone forms
Rotation of Earth on its axis Coriolis deflection
Diurnal tides = 1 high tide & 1 low tide each day
Spring tides occur at new & full moon
Intertidal zone => part of sea bottom that is regularly exposed to the atmosphere
Plankton => all floating & drifting organisms in the sea
Diatoms (algae) => most abundant plants in ocean
Salt wedge estuary
Low tidal input
High river input
Low mixing of water
Primary production facilitated by sunlight & nutrients
~10% of energy transferred to next trophic level
Competitive exclusion => 1 species outcompetes other species & drives them extinct
Filter feeders live in place with high bottom energy + high bottom substrate
Upwelling areas & river outlets unsuitable for corals
Institution => social organization that is emerging, developing, functioning, and becoming structural
, Main purpose: create order in (inter)actions of people
E.g. UNCLOS (UN Convention Law Of the Seas)
Policy => range of decisions, that guide actions & assist in future decision-making
E.g. Wadden Sea UNESCO World Heritage (policy arrangement)
Agency => capacity of individuals to construct the world around them, through day-to-day choices
E.g. Marine Stewardship Council (actor)
Tragedy of the commons => users of a commons are caught in an inevitable process that leads to
destruction of the resources on which they depend
Key concepts
Module 1: ecological dynamics & resilience
Social-ecological systems (SESs)
- Understand & manage change
Key variables & interactions in SES assess resilience
1. Interaction web: + & - interactions
2. Identify important feedback loops
Changes in marine systems
Shifting baselines => rapid change not noticed
Fish are getting smaller over time
Causes
Human activity
Coastal development
- Fishing
- Oil spillage
- Nutrient runoff from land
- Climate change
Effects
Single stressor response
1. Proportional responses (linear)
2. Sudden responses (non-linear) problematic for management (unpredictable) shift to
alternative regime
But: multiple drivers/causes of change (not 1 stressor)
,Ecological dynamics
Important to understand dynamics of marine systems, not only ecosystem
Anthropocene => time of (human driven) change
- Response to change?
- Systemic approach also consider e.g. geology & sociology
Complex dynamics complex systems perspective
Role of interactions in marine systems
(socio)ecological interactions key to understand emergent dynamics
Interaction = effect of 1 population on the other
Direct interactions
o Biotic
o Intraspecies => within species
o Interspecies => between species
o Biotic-abiotic
o Humans – biota
o Humans – abiota
↓
Trophic (+/-)
- Predation & herbivory
Interference competition (-/0)(-/-)
- Aggression & establishment
Direct facilitation (+/+)(+/0)
- Substrate &barnacles on whales
Indirect interactions
Trophic cascade
- Bottom up control => prey determines top predator population
- Top down control => top predator determines prey population
Negative and positive feedbacks: response to changes in marine environment
Feedback mechanisms => species has effect on itself through other species (circle)
, Results in non-linear responses to change, important!
Negative feedback => species has indirect – effect on itself
Dampen change
Positive feedback => species has indirect + effect on itself
Accelerate change potential to destabilize systems
- Facilitate regime shifts
- May lead to alternative regimes/traps
Recognition can help understand emergent dynamics & potentially break them
Non-linear effects of change
Trophic cascades
Alternative stable states
Alternative stable states & critical transitions
Regime shift => relatively rapid change from 1 regime to a contrasting one
Some shifts are difficult or impossible to reverse
Examples
- Coral bleaching
- Shift from coral to macroalgae
Causes
- Severe disturbance or permanent change (e.g. hurricanes, higher sea surface T=SST)
- Gradually changing conditions (internal dynamics, tipping point)
- Or a combination
- Tipping point = critical transition
Pulse disturbances
Temporary
Coral reefs:
- Hurricane
- Sea urchin disease
Press disturbances (drivers of change)
Gradually changing environment, permanent
Coral reefs:
- Increased fishing
- Increased nutrient runoff
- Increasing SST
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