Volume 36/Number 12/December 1998

carcasses were washed up. Further studies showed that the decline in populations were only occurring in coastal areas which were accessible to whales and not in the more sheltered zones. The two have co-existed for thousands of years but living in totally different parts of the sea. This is what makes the shift in killer whale behaviour alarming. Both sea otters and killer whales are top predators in their respective habitats. The sea otters control the sea urchin population in the coastal regions allowing the kelp forest to thrive. Already there has been a rise in sea urchin population in response to the decline in sea otters and this means that the kelp populations will be more heavily grazed by the urchins, causing a decline in their populations. The whole balance of these coastal systems will be altered if this new predation continues. The researchers have calculated that a killer whale feeding exclusively on sea otters would consume 1,825 in a year. As few as four whales feeding in the Aleutian archipelago could have caused the recorded population declines.

The report likens the whole process to an ecological chain reaction where a dramatic change in the inter- relationships between ocean and coastal systems is occurring. This could directly and indirectly affect numerous marine and coastal species and hence the stability of food chains in different parts of the sea.

Rio Grande River Studies The Rio Grande, one of America's 14 American Heritage Rivers has been undergoing an extensive pollution and water quality study for the last three years along with the Rio Bravo in Mexico. The Environmental Protection Agency (EPA) and Mexico's National Water Agency have funded the study which has been co-ordinated by the United States and Mexican sections of the International Boundary and Water Commission (IBWC). Environmental concerns have been growing in the Rio Grande/Rio Bravo border area between the US and Mexico where there are rapidly expanding industrial and population centres. Considerable co-operation between the two countries has enabled the work to move smoothly resulting in a large collection of high quality data. Samples of water, sediment and fish tissue have been taken from 27 main river sites and 19 tributary sites. They have been analysed for 161 different chemicals. Only a few samples showed concentrations of chemi- cals above the acceptable levels. However, these do not pose an immediate threat to public health. However, the information should enable some chosen areas to be then examined more fully to determine particular pollution sources and work towards more effective management.

Damaged Wetlands To Be Restored A Colorado private rancher has undertaken to restore damaged wetlands in response to a threat of heavy fines. A wetland area on Whatley Ranch, associated with the Blue River in Denver, has recently been damaged with bulldozes and backhoes. Alterations were made to wetlands, creeks and beaver ponds with no permits, illegally damaging the habitats. Discharges were also made of dredged materials in direct violation of the Clean Water Act. Material running off into the river would have moved on into the Colorado and ultimately into the Gulf of California. The owners of the ranch have agreed to restore much of the area in order to avoid the heavy fines that could come into operation. Civil penalties of up to $27,000 per day per violation are the going rate. In order to avoid these fines Clean Water Act permits have to be obtained from the Corps of Engineers.

The wetland areas in the Colorado mountains are considered of great importance as they provide habitats for migratory birds, fish elk and beaver. They also improve water quality, detain floodwaters and connect with underground aquifers. With the mountain areas under such pressure from development for recreation the wetlands are being closely monitored.

The owners will restore the beaver pond and wetlands complex as well as remove the illegal discharges. Together with their restoration of a large willow wetland, the area should be largely restored to its earlier quality.

Mercury And Other Toxins Contaminate Fish Tuna and other sea foods and fresh water fish could contain dangerous levels of mercury according to a recent report from the Environmental News Network (ENN). The Coastal Alliance, a coalition of 300 environmental groups across the US has already identi- fied 1,600 sites where fish from local waters are considered unsafe. Mercury contamination is very readily recognised in animal tissue as the mercury is converted into methylmercury, a potent neurotoxin, which then accumulates. The accumulated mercury can have a wide variety of effects particularly in vulnerable groups such as pregnant women and developing children. The foetus and young child are particularly sensitive to levels of this heavy metal and the effects can be difficult to pinpoint if the levels are low. Slow neurological development is just one consequence which can be measured when mercury is found in tissues. Even half a can of tuna a day can cause these elevated levels.

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