Water from Cutler Reservoir, Utah, being filtered with a 60-ml syringe and a cartridge holder that has 1-um filter in it. The filter allows the limnologist to separate dissolved from particulate material. In this case the filtered water was used for the analysis of dissolved phosphorus and the material remaining on the filter was analyzed to determine the amount of algae in the water. The latter was done by measuring chlorophyll a. Although the technique removes very small particles, even smaller ones (viruses, colloidal materials) still pass through and are included with the dissolved material.