An important component of field quality assurance and quality control is the maintenance of field equipment. All nets and sieves must be inspected for damage at least daily and repaired as soon as damage is discovered. Nitex netting can be repaired easi ly using thermoelectric glue guns that are available in corded and cordless models. The locations of holes and worn spots are determined by visual inspection and marked. Hot glue is then applied to the damaged spot from both sides of the net and allowed to cool. This procedure produces a quick, permanent, and durable repair. Small torn places in net seams are repaired in a similar manner, although it is usually advisable to re-sew the seam before sealing it. Similarly, brass and stainless steel sieve s also can be temporarily repaired in this fashion, though permanent repairs are made by having the sieves professionally soldered. The canvas scuff guards present on many samplers, such as D-frame dip nets, Surber samplers, and Hess samplers, are inspected for damage daily and repaired by oversewing with similar canvas materials. Nets are replaced when damage is severe or repairs are impossible. Replacement nets should be part of standard field equipment.
Grab samplers are cleaned after every use to prevent cross contamination of samples and to ensure reliable operation. In most cases, lubrication of grab samplers is not necessary if they are kept clean and are stored properly. Lubrication should be avoided if the sampler is ever intended to be used for collecting chemical samples because of the risk of contamination. Screening on the samplers is inspected and repaired on a daily basis, and samplers are transported in sturdy boxes to prevent damage. All cables are inspected daily to ensure that they are in good condition and are replaced as necessary. Winches, boats, motors, and safety gear such as personal floatation devices (PFD's), fire extinguishers, and first-aid kits are periodically inspected, maintained, and repaired as necessary.
The combining of multiple benthic samples into a single composite sample may result in an unacceptably large volume of material (more than 0.75 L). Consequently, samples are field processed to reduce the volume of each sample component so that it fits in to a 1-L sample container with ample room for preservative. Sample volume reductions are accomplished by removing large debris, elutriating to remove inorganic sediments, and then splitting the elutriated samples (fig. 7). Field processing is applied ei ther to individual samples as they are collected or to the entire composite sample. The latter approach is feasible if each sample produces only a small volume of material. However, if each sample produces a relatively large volume of material, it will be faster to process each sample individually and composite the sample components. The study-unit biologist determines which approach is more appropriate for conditions at the site. Field processing can result in the production of four sample components from each composite sample: large-rare, main- body, elutriate, and split-sample components.