Thursday, September 23, 2010

The Bleaching of Coral in Today’s Ocean Habitats

In the infinite oceans of our planet, lives a species that plays a very important role in sustaining approximately a quarter of all marine life. Although it only “[covers] less than one percent of the ocean floor”, coral is a vital part of the marine ecosystem. Coral is composed of “tiny, soft-bodied organisms” called polyps. These polyps are “related to sea anemones and jellyfish”, and their appearance instantly reveals the close similarities between the species. Coral are capable of “[living] on their own, but are primarily associated with the spectacularly diverse limestone communities, or reefs, they construct”. When one imagines a coral reef, images of a serene, colourful underwater paradise usually float into ones mind. The incredible colour and vibrancy of the coral is due to “the billions of [colourful] zooxanthellae (ZOH-oh-ZAN-thell-ee) algae they host”. Coral is highly influenced by “such things as temperature change or pollution,” which can result in bleaching of the polyps. If these external stress factors continuously alter the coral, without any form of relief, the coral community will die.

In the summer of 2005, an increase in water temperatures led to a massive coral die-off both in the Virgin Islands and around the world”, according to Aldeth Lewin, a member of the Daily News staff. The higher temperature of the water is what causes the coral to “expel the symbiotic algae that live within [the polyps]”, thus eliminating the food source on which it relies. This “symbiotic algae” is what gives each polyp of coral its individual colour. When the algae is removed, “the coral becomes stark white or “bleached,”” which in turn makes the coral “vulnerable to disease and predators”.

The National Oceanic and Atmospheric Administration releases a Coral Bleaching Thermal Stress Outlook annually, which for 2010 “[predicted] a high likelihood for coral bleaching this [past] summer”. The basis of the secondary source article to which I am blogging about draws information from the 2010 Coral Bleaching Thermal Stress Outlook. The Coral Bleaching Thermal Stress Outlook includes satellite imagery of sea surface temperatures, which get analyzed and interpreted through computer software and models. In Lewin’s article, the NOAA Coral Reef Watch coordinator, Mark Eakin is quoted saying, “the temperatures in the Caribbean have been above normal since January. The models are showing similar trends to those recorded in 2005”.

Jeff Miller, a fisheries biologist for the Virgin Islands National Park, said that “from October 2009 until the end of August, the water temperatures have been at or above normal”. According to Lewin, “[corals] have a range of temperatures in which they can survive. Every year at this time, corals reach the upper limit of their thermal tolerance.” Lewin argues that “global warming is causing the water temperatures to stay in the high end of the corals’ threshold all year round”, which is in turn causing large colonies to perish. Tyler Smith, an assistant professor at the University of the Virgin Islands Center for Marine and Environmental Studies believes that the “water temperatures in the [Virgin Island] territory seem to be hovering around 86 degrees,” and that “[without] a strong event to force the cooling of the water, sea surface temperatures will remain as warm or warmer for... four to six weeks [longer]”. It is at these warm temperatures when “mass bleaching” occurs.

In his recent research, fisheries biologist Jeff Miller noticed “water temperatures at reef level dropped three to four degrees [immediately after hurricane Earl passed]” through the region. This lead him to believe that “the storm may have prevented the water from heating up beyond the coral’s threshold” for survival. In her article, Aldeth Lewin mentions how she believes “that scientists do not really know how the reef will react or recover”, with regards to the warming of the ocean waters. Lewin goes on to include an alternate idea from Tyler Smith at the University of the Virgin Islands Center for Marine and Environmental Studies stating that “the corals may actually do better” and adapt to the climate change. Currently, scientists, coral conservationists, and the NOAA are working towards discovering “whether there are some areas in the territory that may be less susceptible to bleaching”, which would be more crucial to the overall survival of the coral communities. The following paragraphs will explain the contrast between both the primary and the secondary sources.

The secondary source article entitled, “Scientists Watching V.I. Coral Bleaching” gives the public quick insight into the problems the coral polyp are facing near the Virgin Islands, but also in other ocean reefs around the world. The article draws information and data from numerous sources including a fisheries biologist from the Virgin Islands National Park, an assistant professor at the University of the Islands Center for Marine and Environmental Studies, a coral conservation manager at The Nature Conservancy, and also experimental data and analysis from the NOAA (National Oceanic and Atmospheric Administration) Coral Reef Watch.

Dissimilarly, the primary source, the NOAA Coral Reef Watch’s Seasonal Coral Bleaching Thermal Stress Outlook report, is directed at a more scientifically inclined reader or analyst. The report includes data charts, models, thermal maps, pattern descriptions and satellite imagery which have little or no significance to the typical reader. This sort of data is generally directed at scientific analysts, statisticians and researchers who are able to interpret it in a way that makes it easier for the general public to understand.

Works Cited

NOAA Coral Reef Watch. (2010). Seasonal Coral Bleaching Thermal Stress Outlook

Lewin, Aldeth. (September 18, 2010). Scientists watching V.I. coral bleaching

Coral Anthozoa. National Geographic.

- Cooper Rice, Student I.D. # 0723086

1 comment:

  1. This was previously posted on Thursday, September 23rd before the deadline. The image I uploaded was not loading properly, so I changed the image and therefore had to repost the blog.