Figrure 12-1. Handheld, flow-through coring device for quantitative sampling of infauna. Core tubes in A,C and D are 10 cm (4 in) inside diameter (ID); core tube in B is 15 cm ID.
All tudes shown are 20 to 30 cm long.
A. sample tube corer with rubber stopper at top ;
B. sample tube corer with aluminum bar handle for easier insertion and withdrawal from sediment;
C. JET (Jackson Estuarine Laboratory) remote corer with 5 cm (2 in) ID PVC handle (~2m long) attached to one-way valve via threaded coupling; handle extansions can be added via threaded coupling;
D. As sample C except core tube is constructed of clear polycarbonate which
is attached to PVC coupling with stainless steel hose clamp; handles are made of aluminum pipe and are coupled to flow-through valve and one another via bolts through pipe and aluminum bar inserted into both pipe ends for added strength.
Further identification depends on the reqirements of the study.
Bentic ecologists traditionally have tried to achieve species-level identification, but this can be a costly and difficult goal in many areas because of the number of species that are encountered.
Recently, however, there has been a concerted effort to determine what level of taxonomic resolution is needed for particular research questions.
In a major review, Warwick (1993) concluded for many ecological investigations that very little information is lost by working at the taxonomic level of family or higher.
Regardless of what level of identification is needed for a particular study , appropriate taxonomic keys must be used, and those doing the work must be well-trained
A few of the major taxonomic references suitable for the identification of infaunal and epifaunal invertebrates for the global geographic regions are presented in the Appendix.
We have concentrated on recent , widely available , and comprehensive works.
There is no intention here to cover the primary taxonomic literature or to list specialized keys for particular taxa.
12.3.5 Data processing and analysis
Abundance data are typically derived from counts of each taxon and can be expressed in any of several different units.
Biomass can be measured as wet weight, dry weight , or ash-free dry weight and typically expressed in g per unit area (e.q., table 12-1)
12.3.6 Trouble Shooting and Hints for infauna
simple tube corers are rugged and dependable.
We have used acrylic and PVC tubes on all types of soft sediment with no serious problems.
Although remote corers are more complicated than simple tube corers, and problmes can occur, our experiences have indicated that they are also quite dependable.the remote corer in Figure 12-1 D has been in use at Jackson Estuarine laboratory for about 10 years.
It has taken hundreds of cores from a variety of soft sediment habitats,including eelgrass beds, and in sediments ranging in texture from sand to soft mud.
It has been used in water depths up to about 4 m.
All the original components are still in use, including the removable polycarbonate tube.
Our experiences with this remote corer as well as other hand-held corers suggest several important considerations for corer design and operation.
Regardless of core tube material, the bottom edge of the tube should be bevelled to provide a sharp edge for easy entry into the bottom and for cutting the seagrass root mat.
The bevel should be applied on the outside edge so that sediment is forced outward as the tube enters the bottom and so the diameter of the sediment entering the tube is constant.
A sharp cutting edge is essential for consistent penetration and minimization of core compaction.
In some cases the root/rhizome mat may be so dense as to require cutting with a "pre-corer"cylinder the same diameter as the sample tube and made of thin steel or aluminum with a sharp edge
The one-way valve on the remote corers is made of rubber.
It is good practice to keep the valve clean by rinsing with fresh water after a day's use, which prolongs valve life and ensures a good seal during operation.
Most components of the corers can withstand considerable abuse, but the valve can be damaged and the rubber material deteriorates over time
When sampling in areas that have rocky bottoms, one should be careful when encountering the bottom.
Core tubes made of acrylic can be easily cracked or chipped on rock.
PVC , polycarbonate, and metals are more rugged than acrylic, but any core tube can be damaged if one is not careful.
For remote corers, the use of PVC handles with threaded coupling (Figure 12-1 C ) is more economical than aluminum pipe handles (Figure 12-1 D ).
The PVC handles, however, are not as rugged.
It is good general practice to carry spare parts along for all gear being used, but it is particularly recommended for remote corers with PVC handles.
The PVC tends to weaken at the joints over time because of side-to-side movement that invariably occur to some extent when sampling , especially in deeper waters where one or more handle extensions are used.
Although handle breakage has been rare in our experience , it has always occurred at a coupling
12.3.7 Discussion
most of the above methods result in capture of some epifauna along with infauna.
there is no standard technique for dealing with this problem.
we usually remove all seagrass parts protruding from the bottom of the core tube but retain what in inside the tube for further processing .
capture of epifauna is not eliminated, but is at least reduced in a consistent manner.
until there is further work on this issue, we recommend this as the standard procedure.
corers are recommend as the standard sampling devices for quantitative sampling of infauna, but other techniques are mentioned.
all these techniques at least potentially provide quantitative data on infauna.
one of the most important things to keep in mind when using any sampling
device is to be sure that the selected amount (typically surface area or volume