Ssm Winter 2007 Biomed Polluter

biology + medicine

the

invisible polluter

The Effect of Groundwater Discharge on Coastal Ecosystems

Credit: Jenny Huang

by Misha Tran

10 10 stanford scientific

T

he next time you reach for that bottle of Advil or that cup of coffee as you try

to fend off an on-setting headache and to gain a few more hours for that problem set, consider this: you may be contributing to the presence of ibuprofen and caffeine in coastal oceans and inadvertently affecting coral reefs and other coastal ecosystems. In a study conducted by Dr. Adina Paytan, assistant professor of Geological and Environmental Sciences at Stanford, and her team of Stanford University researchers, Dr. Alexandria Boehm and students in Civil and Environmental Engineering, found that groundwater discharge is a source of pollution for coastal waters.

The State Of Coral Reefs Today Coral reefs, found in the clear, warm waters of tropical oceans, are an important source of productivity and diversity in the ocean environment. The corals maintain a symbiotic relationship with algae and together, provide food and shelter for many different species of fish and marine life. Additionally, coral reefs protect coasts from erosion by slowing down and thus minimizing the impact of strong waves. In recent years, however, coral reefs have been in decline in most places around the world due to human activities such as: sediment overloading, over fishing, climate change, eutrophication, and diseases. Increasing nutrient pollution at some locations has led to algal blooms and inversely, a decline in the coral reefs. The coral is better adapted to water where the nutrient concentration is low while macro algae flourish when there are more nutrients, particularly phosphorous and nitrogen. In the Bahamas and in Jamaica, according to Dr. Paytan, “it’s been documented that nutrient loading has caused a phase shift between coral to algae.” In her study, Dr. Paytan looked at groundwater as a potential source of nutrient pollution. Scientists have long suspected groundwater as a source, but according to Dr. Paytan, there has been no previous extensive study that has “directly quantified the nutrient and pollutant flux associated with this submarine groundwater discharge and its effect on the reef.” Although the percolation of groundwater into the ocean is typically not a visible process, a mixture of groundwater and sea water seeps into the ocean wherever the coast washes the land. In the past, there have been cases where pollution was seen to impact the surrounding coastal biological community, including corals, but not always a specific source of pollution was identified. Thus, Dr. Paytan wanted to determine if groundwater could be this “hidden” source.

biology

was the presence of bacteria, estrogen, caffeine, + pharmaceutical drugs, nitrate, and other pollutants in medicine the water. Since pinpointing groundwater as a source of coastal pollution, Paytan and her researchers have returned several times to Hawaii and have documented high radium and nutrient levels at different sites. They are also starting to analyze samples of ocean water for the presence of human-made products, such as caffeine and pharmaceutical products, and are indeed finding them in the sea water. In this next phase of her research, Paytan hopes to elucidate the relationship between the amount of nutrients and pollutants in sea water and the health of the coral reef and the effect of land use on these two factors.

Looking Into The Future The objective of this study was to determine if groundwater is present in coastal oceans and if it is a source of pollutants, and Dr. Paytan’s research has shown the presence of groundwater and pollutants in sea water. Ultimately, Dr. Paytan wants her research to raise public awareness about the impact that humans have on coral reefs and other coastal ecosystems. She says, “I want the public to realize that there is another conduit of pollution that’s not easily seen... [groundwater] is like an invisible invader.” Dr. Paytan believes that the protection of coral reefs is vital to the maintenance of biodiversity in the oceans and industries, such as fishery and tourism, that depend on them. The health of the coral reefs, Dr. Paytan believes, should be taken into account when developmental projects are undertaken in the future. For example, instead of having golf courses and other facilities be built adjacent to the shore line, we should build these further away to minimize the impact of groundwater discharge on coral reefs. The challenge for us in the future, therefore, will be to balance economic development and expansion with the maintenance of a fragile natural resource that is invaluable to the ocean ecosystem by considering the impact of groundwater discharge as a pollution source. S MISHA TRAN is a sophomore with interests in biology and history.

To Learn More: For more information, visit the website of Dr. Adina Paytan’s Chemical Oceanography Lab: http://pangea.stanford.edu/research/paytanlab/main.html

Focusing On Groundwater

layout design: Ly Nguyen

Photo Credit: NOAA

Over the course of several years, Dr. Paytan and her team took samples of oceanwater and groundwater in Mexico, Hawaii, California, Florida, and the Red Sea. The level of radium isotopes, geochemical tracers produced in rocks and soil, was used to determine the extent to which groundwater was mixing with the oceanwater since radium isotope is found at a much higher concentration in saline groundwater than in sea water. The researchers found that radium isotopes existed at higher than normal concentrations in open sea water at the land-ocean interface at all sites including where coral live. They then measured the type and amount of nutrients and pollutants in the groundwater and used this to determine how much pollution from land sources was present in the sea water. What Dr. Paytan and her collaborators found

Coral reef bleaching, resulting from the loss of symbiotic algae, occurs under environmental stresses such as increasing ocean temperature.

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