Marine Bio Exam 4

Community

A group of interacting populations of different species living in the same place at the same time

• Intra - interactions within SAME species

• Inter - interactions between DIFFERENT species

Competitive Exclusion Principle

Two species that use a limited resource in the same way cannot co-exist indefinitely

• Resource Partitioning: species use the same limited resources in different ways to reduce competition to allow coexistence

Adaptations to Avoid Predation

• Armor

• Toxins

• Crypsis

• Mimicry

Predation on Communities Structure

• Species can be organized spatially due to predation pressures

  • Green algae easy to eat → upper intertidal, where herbivores can’t eat as easily

  • Brown and red algae harder to eat (chemicals) → middle/ lower intertidal, can withstand herbivores

  • Crustose coralline algae → subtidal, not eaten

Facilitation

One species benefits another species by improving environmental conditions or provide a habitat

• Rockweed decreases heat and desiccation when tide low → allow species to hunt in intertidal

• Mussels stabilize sediment in Salt marshes

Can aid in restoration efforts!

• Clams increase seed germination due to increasing sediment stability and fertilizing with waste

Ecosystem

A community of living organisms interacting with each other and with their physical environment

Succession

Sequential changes in species composition through time often after a disturbance

1. Pioneer species - 1st organism to colonize a new or disturbed area

• Tolerate harsh conditions, usually small and fast-grow

2. Intermediate species - Organism replaces pioneer species as conditions improve

• Benefits from changes made by pioneers

3. Climax community - final stable community in succession

• Most complex and diverse

• Relatively stable

Succession in Marine Ecosystems

1. Scavenger stage: carcass eaten by mobile scavengers (sharks, fish, crabs)

2. Enriched sediment stage: sediment, rich in nutrients, supports invertebrates

3. Sulfide stage: sediment becomes anoxic, emits hydrogen sulfide, supports chemoautotrophic bacteria

4. Reef stage: bones provide hard substrate for epibenthic organisms

Succession in Rocky Intertidal

Disturbance caused by wave action makes an open patch on rock

1. Bare rock

2. Bacteria film

3. Seaweeds

4. Barnacles

5. Mussels

Succession can vary based on species present

Intermediate Disturbance Hypothesis

Most biodiversity and can coexist

• At low levels: competitive dominants exclude other species

• At high levels: only the most resistant survive

Alternative Stable State

Thresholds of change: borders between alternative stable states

• if disturbance pushes past tipping point, ecosystem will switch to another state rapidly

Regime shifts: transition from one alt stable state to another through passing threshold

• Hysteresis: path of ecosystem recovery is different of its decline, not easy to return to its original state

  • ecosystem shifts to barren ground, remove overgrazers will not automatically return

Ecosystem services

Natural processes and resources provided by ecosystems that support human life/ well-being

1) Provisioning: Provides food, water, and other resources

2) Regulating: Maintenance of stable ecosystem process

• CO2 sequester

3) Cultural: Fostering creativity, culture, recreation, spiritual

4) Supporting: Basal services that support provision of other services

Coral Reefs provide costal protection, food/ fishing, tourism

Fisheries Terminology

Catch: # or weight of fish caught

Directed catch: intended or “target” catch species

Bycatch: unintentional catch species

Discards: # or weight of fish returned to the sea

Landings: # or weight of fish delivered (bycatch & discards removed)

Types of Fisheries

Finfish Fisheries: “fish” vertebrates with fins

• increasing regulation and slowly leading to more sustainable exploitation

Invertebrates Fisheries: invertebrates with no backbone

• rapid increase in demand

Longline

Gillnets

Pots and Traps

Purse seine

Pelagic Trawl

Bottom trawl