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TL PhD Comprehensive Exam
  • Introduction
  • Tasklist
  • 1. Basics
    • 1.1 Basic Biology Review
    • 1.2 Basic Genetics Review
    • 1.3 Light & Photosynthesis
  • 2. Coral Biology
    • 2.1 Basic Coral Biology
      • 2.1a Food Webs
    • 2.2 Reef Structure
    • 2.3 Growth & Reproduction
    • 2.4 Morphology
    • 2.5 Physiology
    • 2.6 Mixotrophy & Energy
    • 2.7 Symbiosis
    • 2.8 Reef Mortality
      • 2.8a Conservation
  • 3. Ecology & Evolution
    • 3.1 Evolution & Plasticity
    • 3.2 General Ecology
    • 3.3 Species
    • 3.4 Cryptic Species
  • 4. Isotopes
    • 4.1 Isotope Basics
      • 4.1a Instrumentation & methodology
      • 4.1b Environmental O & H
      • 4.1c Environmental C and N
      • 4.1d Organismal Isotopes
    • 4.2 Fractionation in Corals
    • 4.3 Trophic Niche Analysis
    • 4.4 CSIA
      • 4.4a C: Essential vs. Nonessential
      • 4.4b N: Trophic vs. Source
  • 5. Other
    • 5.1 Science & Society
    • 5.2 Stats
  • 6. Summary & Resources
    • 6.1 Glossary
    • 6.2 Resources
    • 6.3 Questions From Exam
    • 6.4 Recommendations & Reflections
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  1. 2. Coral Biology

2.8 Reef Mortality

Last updated 1 year ago

Climate Change & Bleaching

  • sea level rise, changes in storm frequency and intensity, changed ocean circulation & warming waters

  • Bleaching summary

    • symbiont photosystem is easily overwhelmed by excess light leading to the production of reactive oxygen species

    • create oxidative stress in the coral tissue, causing coral to expel symbionts to avoid tissue damage

    • previous exposure & symbiont species affects bleaching severity

  • Bleaching causes slowed growth, mortality, reduced reproduction, increased susceptibility to disease

Sedimentation

  • sediments can smother coral colonies, clogging feeding structures, blocking sunlight, and causing exhaustion by forcing the animal to clean itself off (using mucus)

  • caused by deforestation, coastal development, and agriculture

  • black band, white band, white plague etc.

Deoxygenation

  • 1-2% decrease in global dissolved oceanic oxygen. Deoxygenation negatively affects disease, bleaching, reproduction & growth rate.

  • Sources: UN Report 2019, Hughes et al. 2020, Nelson & Alteri 2019, Report- UN 2019,

Acidification

  • Increased CO2 in the atmosphere leads to increased DIC in the ocean, and the consumption of carbonate ions impedes calcification rates, making corals grow more slowly.

  • Sources: Fabricus 2011, Johnson et al. 2017, Wall et al. 2017, Schoepf et al. 2013

  • any organism that erodes and weakens the calcareous skeletons of reefbuilding species.

  • external - parrot fish, puffer fish, hermit crab, limpet, urchin, chiton

  • Internal - algae, fungi, bacteria, sponges, bivalves, barnacles, worms

Reef destruction

  • harmful fishing practices, development or other physical destruction of reefs

Algal competition / shifting states

  • Decline in herbivores - fewer herbivores like urchins allows the shift to algal steady state

  • Overfishing - removal of herbivorous teleosts enables macroalgal growth

    • break down of food web

    • cyanide & dynamite fishing

  • predators - crown of thorns sea star,

Pollution

  • Sunscreen (Danovaro et al. 2008)

  • Excess nutrients - runoff from agriculture (fertilizers) and sewage, increasing N and P which peaks algal growth (phytoplankton blooms -> no oxygen, no light)

  • Plastics - microplastics ingested & smothered/light blocked by macro plastics

Bioerosion
Disease