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Water Studies

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Corals in Bunaken

Brain Coral, Author Alexander Vasenin

Source Orang-Utan Crab (Achaeus japonicus) on Bubble-Coral (Plerogyra sinuosa)
Author Bernard DUPONT

Meandering hard coral, Author:Johnmartindavies

Plate coral (Mycedium sp)  credit: James Oliver (

Corals in Indonesia

A sandy lagoon dominated by soft corals credit: Mark V. Erdmann (

The reef flat dominated by branching and table Acropora,  credit: Mark V. Erdmann (

Acropora nasuta
Author NPS photo - Eva DiDonato. Identified by Charles Birkeland


Staghorn corals

Science Explained: Coral Bleaching & Ocean Acidification

Explains the biology of corals and their symbiotic algae and how bleaching occurs.
Demonstrates the chemical processes related to carbon dioxide in the atmosphere, the effect on pH of the oceans, and the result for corals and other sea creatures.

Importance of Research

The absence of regional-scale quantitative analyses of reef health in general and coral cover in particular has led to substantial confusion and disagreement about the patterns and causes of coral decline. This shortcoming has also greatly limited our ability to measure the efficacy of different management practices designed to mitigate and reverse reef degradation.
Most marine conservation policies focus on the commercially harvested occupants of these habitats. Such remedies will fail unless we gather the scientific knowledge and political will needed to effectively reduce the stressors degrading corals and other marine foundation species.  
Bruno & Selig,  2007

Bleaching & Death

Photos taken of corals during a bleaching event. Created by: Ham Merhead (© Jan. 2016)
Video captures a coral ejecting its resident population of algae, which helps corals survive warmer water in the short term, but in the longer term can be lethal to corals. Taken by scientists at Queensland University of Technology in Australia,

Coral Restoration Projects

A project that aims to balance the environmental needs of the reefs with locals who need the reefs to survive. Lesson by Joshua Drew, animation by Veronica Wallenberg

Corals in Bunaken

Coral Reef Growth and Disruption

Macro-Scale Factors

  • Tectonics
  • Sea Level

Meso-Scale Factors

  • Temperature
  • Salinity
  • Wave Energy

Micro-Scale Factors

  • Light
  • Nutrients
  • Sediment
  • Previous Structure

Hubbard, D.K. (1997). Reefs as Dynamic Systems 

Threats to Coral Reefs


  • coral bleaching
  • global climate change
  • diseases of corals and other reef organisms
  • plagues of predators like the crown-of-thorns starfish and other damaging organisms such as the sea urchin
  • invasive species which have been introduced onto new coral reefs.

These threats are in addition to natural stresses that have always existed on coral reefs such as storms, freshwater inundation and seismic and volcanic events.

Goldberg, J. and C. Wilkinson, 2004
Global Threats to Coral Reefs: Coral Bleaching, Global Climate Change, Disease, Predator Plagues, and Invasive Species.
p: 67-92. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p.

Crown of Thorns Starfish

Outbreaks of the corallivorous crown-of-thorns seastar Acanthaster planci (COTS) represent one of the greatest disturbances to coral reef ecosystems in the Indo-Pacific, affecting not only coral reefs but also the coastal communities which rely on their resources.

At normal population densities, COTS play essential roles in the food webs of coral reef ecosystems. However, when outbreaks occur and their population density greatly increases in relatively concentrated areas, COTS become a problem.     - Moutardier et al., 2015

The crown-of-thorns starfish is nearly the largest species of starfish (Asteroidea). It may be 50 cm or more in diameter and can have more than 15 arms. Its ‘crown-of-thorns’ are the long sharp spines that cover its upper surface. What is more, the spines are coated with a saponin toxin, which causes irritation to puncture wounds.
Crown-of-thorns starfish feed on the living surface tissue of hard corals (Scleratinia). Using hundreds of small, sucking tube feet in each arm, the starfish slowly moves onto the surface of the corals. It pushes its stomach out through its mouth on the underside, spreading the stomach across the surface of the coral beneath it to about its own diameter. It digests the coral tissue with enzymes secreted from the stomach and harvests the digested tissue as it retracts the stomach. 
Lucas, 2013

Coral Reefs - Human Impact

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Reef RSS

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