DEALING WITH OIL SPILL CRM completes Environmental Sensitivity Index map

The Coastal Resources Management has completed last month the Environmental Sensitivity Index, a project designed to assist Northern Marianas officials and planners in dealing with oil spills.

According to John Jordan, manager of Geographic Information System, the ESI maps show the key biological resources — birds, fish, mollusks, mammals, reptiles and amphibians and coral reef areas — that are most likely at risk in the event of an oil spill. The atlas provides information on what species live in various areas, their reproductive activity such as nesting for birds, spawning for fish.

The eight-month project, which was prepared by Jordan along with the National Oceanic and Atmospheric Administration and the US coast Guard, covers the areas of Saipan, Rota, Tinian and Aguijan.

Among the factors considered in determining the relative sensitivity of shoreline habitats are shoreline type, exposure to wave and tidal energy, biological productivity and sensitivity, ease of cleanup and physical characteristics of the discharged pollutant.

The strength of the waves will have a direct effect on the persistence of stranded oil. Need for shoreline or cleanup activities is determined, in part, by the lack or slowness of natural processes in removal of oil stranded on the shoreline.

For example, clean up of an oil spill in Banaderu Watershed, where green sea turtles are found, would have to take into consideration its toxic effects on eggs in the nest. But because the eggs are laid above the high tide line, direct oiling is unlikely except during storms.

Nesting beaches should receive highest priority for cleanup if they are oiled prior to the nesting period. Rapid removal of oil from a beach with active nests may be attempted, specifically if the oil has not reached the nest sites.

Beach cleanup operations and heavy machinery can disturb nesting adults, and emerging hatchling which maybe killed by being trapped behind booms placed on the shoreline.

Cleanup activities on nesting beaches should be monitored by experienced personnel so that the nests are not physically disturbed.

The ESI maps ranked shoreline environments (1 lowest to 10 highest) in relation to their relative sensitivity to oil spills, potential biological injury and ease of cleanup.

Areas exposed to high levels of physical energy, such as wave action and currents and low biological activity rank low on the scale, while sheltered areas with associated high biological activity are given the highest ranking.

The rankings follow a shoreline classification system that has been applied throughout the United States.

Mangrove areas with an (ESI-10) are considered the most sensitive habitat on the islands to oil-spill impacts because these are the most difficult to clean up.

In dealing with the mangrove areas, vegetation should never be cut or otherwise removed. Under most conditions, the best practice is to allow the natural recovery, especially where natural cleaning can occur.

Seagrasess, which are found extensively in the lagoon system, must be handled with extreme care during cleanup operations because this may result in the total loss of seagrass bed.

No cleanup is recommended for most oil spills involving coral reef structures as natural processes is expected to be rapid. Sorbents and booms can be used to prevent oil from being transported over the reefs.

Jordan said there is little documentation of long-term impacts to coral reefs from oil spills, except in situations where pollution was chronic. He said the greatest impact to the reef would result from spills of light refined products directly into the shallow water overlying reefs and where high concentrations of water-soluble fractions persist.

During low tides, marine resources are highly susceptible to direct exposure from oil and hazardous substance spills. In the CNMI, reef flat habitats tend to be dominated by algae, seagrasses and encrusting corals.

Coral reproduction is most vulnerable to oiling impacts during the actual spawning event when they spread their floating pelagic eggs. A study conducted by Dr. Robert Richmond, University of Guam, revealed that the peak coral spawning period is 7 to 10 days after the July full moon.