The disease, causing extreme stomach upsets, is caused by a waterborne parasite.这种导致胃部极度不适的疾病是由一种水生寄生虫引起的。Visitors can view a rich and colorful array of aquatic plants and animals.游客们可以看到一系列各种各样、色彩斑斓的水生动植物。Tests showed increased levels of toxin in shellfish.检验表明水生有壳动物的毒素水平提高了。