Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The exhorbitant price of unmanaged shrimp farming

14.01.2005


Water quality in the Rio Chone estuary in Ecuador has degraded over the last three decades by a combination of man-made impacts, including the input of organic wastes from shrimp farming activities located in what were once tropical mangrove forests.



An article in the current issue of the Journal of Coastal Research describes water quality experiments by University of Rhode Island oceanographers Diana Stram and Chris Kincaid and US Environmental Protection Agency (EPA) oceanographer Dan Campbell to assess the extent of water quality degradation in this ecologically sensitive area. The project was funded by a URI/EPA cooperative fellowship agreement and by the URI Coastal Resources Center.

The Rio Chone estuary has a history of water quality problems due to the combination of seasonal climate influences and management of natural resources. The estuary is affected primarily by an influx of sediment because of erosion of hillsides and construction of ponds; seasonal climate changes combined with decreased freshwater flow; and shrimp mariculture development resulting in mangrove habitat loss and the flushing of shrimp pond production wastes into the estuary.


The team of scientists characterized the water quality problems in the Rio Chone estuary by modeling the seasonal distribution of biochemical oxygen demand (BOD) and dissolved inorganic nitrogen (DIN) within the water column. The model allows the scientists to simulate which areas of the estuary are at greatest risk for low water quality, as well as which regions are primarily contributing to the pollution of the estuary.

The model was run under varying water conditions, during both wet and dry seasons, and for a variety of pond effluent locations. The development of the shrimp mariculture industry without regard to its environmental impacts has led to increased BOD and DIN, which, in turn, has caused a number of problems in the estuary.

Shrimp mariculture effluents contain high concentrations of BOD, DIN, and salt (from high evaporation). In the dry season, when the estuarine salinity is inverted (with higher salinity at the head than at the mouth) and circulation in the estuary is sluggish, elevated BOD concentrations from the pond effluents are not flushed from the upper estuary leading to areas of extreme oxygen depletion.

Ammonia represents a large proportion of the DIN concentration. Ammonia can impact aquatic life by acute and chronic toxicity as well as ammonia oxidation, which reduces dissolved oxygenlevels. Ammonia in shrimp ponds causes high mortality rates and can also cause low growth rates in shrimp. Low dissolved oxygen concentrations also increase the toxicity of ammonia to shrimp. Thus, a combination of chronic dissolved oxygen problems and an increase in nutrients can lead to serious effects of decreased water quality on shrimp growth. Increased nitrogen can also contribute to the development of toxic phytoplankton blooms such as red tides. Red tides have not occurred in the Rio Chone, but the increased nitrogen loading may allow them to develop.

The average production in shrimp ponds in the Rio Chone has decreased over the last decade. Increased DIN (and therefore increased ammonia) coupled with increased BOD has likely produced this decline.

The conversion of 90% of the area’s mangrove forests to shrimp mariculture ponds is of particular importance to water quality issues. Studies have shown that mangroves can be used for removing excess nutrients from coastal waters, and mangrove sediments may also be able to absorb some of the BOD from pond effluent.

Other studies have attempted to link water quality with profitability of shrimp mariculture. In the Rio Chone, the ponds closer to the mouth of the estuary, where there is more well-flushed water than the ponds located in the upper regions of the estuary, enjoy higher growth rates of shrimp.

"Our results suggest that site selection of shrimp ponds as well as restoration plans for mangroves should consider the hydrodynamic regime of the estuary in order to maximize pond production and maintain estuarine water quality," said Stram. "Site selection and the subsequent conversion of mangroves to ponds near the head of the estuary should be avoided in order to sustain water quality and prevent seasonal self-pollution problems in pond production."

Lisa Cugini | EurekAlert!
Further information:
http://www.gso.uri.edu

More articles from Ecology, The Environment and Conservation:

nachricht Bioinvasion on the rise
15.02.2017 | Universität Konstanz

nachricht Litter Levels in the Depths of the Arctic are On the Rise
10.02.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Switched-on DNA

20.02.2017 | Materials Sciences

Second cause of hidden hearing loss identified

20.02.2017 | Health and Medicine

Prospect for more effective treatment of nerve pain

20.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>