How does rising atmospheric CO2 affect marine organisms?

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Sediment Impact on Nearshore Coral Reefs
Reference
Nowlis, J.S., Roberts, C.M., Smith, A.H. and Siirila, E.  1997.  Human-enhanced impacts of a tropical storm on nearshore coral reefs.  Ambio 26: 515-521.

What was done
The authors analyzed the thickness, texture, and organic matter content of sediment deposits on offshore coral reefs following the passage of a tropical storm near the West Indies island of St. Lucia in an effort to document sediment effects on coral bleaching and mortality rates.

What was learned
Sediment accumulation rates during and just after the passage of the storm ranged from five to thirty times the average daily accumulation rate over the period 1989-1994.  Less than one month after the storm, thirty to fifty-five percent of the three reefs studied were covered with mud, and a number of corals had begun to show signs of bleaching, with the greatest proportion of bleaching occurring near the mouths of three nearby river basins.  Three months after the storm, coral mortality reached over fifty percent at the most heavily impacted site in the study.  It was also noted that "higher levels of dead and bleached coral" were found "in areas with thicker layers of clay-like sediment, strongly suggesting that the sediment was primarily responsible for the damage."

What it means
The authors of this paper found a relationship between sediment deposition rates and subsequent coral reef bleaching and mortality rates.  Furthermore, they showed "how land development can increase the risk of severe damage to coral reefs by sediment runoff during storms."  These findings suggest that the natural course of human population growth and societal and economic development over the period of the Industrial Revolution may, via gradual intensification of near-coastal riverine sediment transport rates, have predisposed coral reefs to ever-increasing incidences of bleaching and subsequent mortality.


Reviewed 1 June 1999