Zooplankton communities in freshwaters are principally comprised of protozoans, rotifers, cladocerans and copepods, although the variety of organisms is wider in marine environments. Zooplankton are important in the aquatic food chain acting as both a predator to groups such as phytoplankton and as a prey to larger animals such as fish. Due to their relatively short life cycle, zooplankton respond quickly to environmental change, hence sudden fluctuations in zooplankton numbers or species composition can be an indication of a change in water quality. Such changes may be linked to seasonal variations, the transient nature of the waterbody in question or, in the case of long term monitoring programmes, as a result of other factors such as pollution, eutrophication or an imbalance between numbers of piscivorous and planktivorous fish.

APEM ZOOPLANKTON SERVICES

Through the launch of Biolabs, APEM's skilled scientists provide the following zooplankton analytical services:

• Identification of zooplankton to the lowest practical taxonomic level
• Analysis of entire samples where zooplankton counts are less than 200 specimens per sample without sub-sampling. For all other samples sub-sampling procedures would usually be employed.
• Enumeration and determination of the relative abundance of the different taxonomic groups using both a binocular dissecting microscope at 20x to 40x magnification in conjunction with examinations at a higher magnification under a compound microscope
• Analysis and graphical representation of data
• Calculation of densities based upon the numbers of individuals per cubic meter

As with our macroinvertebrate services, our clients can use our analytical services as well as enlist our field scientists to do the actual sampling. The sampling is carried out by using our conical tow-nets, ideal for the sampling of planktonic groups such as zooplankton, which can be rigged for vertical, oblique or horizontal tows. With vertical and oblique tows being used to collect composite samples and horizontal tows to collect samples at a discrete depth.