Why are areas closed for shellfish harvesting?

There are several different types of closures associated with harvesting clams. There are closures for pollution and closures for conservation efforts. Pollution closures include such things as excessive rainfall (runoff from the land carrying toxins into the water), closures for Sewer Treatment areas (outflow areas), Red Tide Closures and seasonal closures (as with seasonal Marina areas). There are also closures for conservation efforts such as closures in newly seeded areas.