Monitoring of biological attributes
Key macrofaunal species which are indicative of the area or rare/sensitive species
should be monitored for changes in presence and/or abundance. Species such as Capitella
capitata should also be monitored as they are often indicative of organic enrichment.
Conversely, other species and assemblages indicative of good water quality should also be
The estimation of primary and derived biological parameters such as total abundance,
species richness and diversity will indicate the nature of the community. Graphical
measures such as Abundance-Biomass-Comparison (ABC), k-dominance and rarefaction curves
and trophic measurements such as the Infaunal Trophic Index (UKITI) provide a valuable
summary of the large amounts of data obtained from benthic sampling programs (Elliott,
1993). It is emphasised that although these indices involve a loss of information, they
allow simple indications of change within a community.
In cases where the above parameters are measured in relation to environmental and
biological quality, the use of the Sediment Quality Triad approach (Chapman et al,
1987) will be required. This provides concurrent assessments of sediment contamination,
community structure and the health of an individual species by using a bioassay.
Intertidal mud and sandflats
i. Sediment cores
Core sampling is required to obtain and extract the infauna for identification and
enumeration and surface quadrat sampling will allow surface features to be quantified.
These methods have the advantage of providing quantitative data for statistical analysis
and a valid comparison of different datasets. However, core sampling is time-consuming and
thus costly. Further details are given by Dalkin and Barnett (1998).
ACE surveys allow information to be obtained rapidly and thus are cost-effective
(Hiscock 1998b). They also provide sufficiently detailed information on species richness
and the presence of rare species or unusual features for comparison with elsewhere.
However the results of ACE surveys are not amenable to statistical analysis and the worker
variability may be high, hence the need for method standardisation and analytical quality
control (see below).
ii. Remote sensing
Remote sensing by aerial and satellite techniques is particularly valuable for large
intertidal areas and intertidal SACs. It is widely used and, when combined with false
colour spectroscopy, will give good ground resolution to determine the size and morphology
of large intertidal areas such as mudflats and the distribution of topographic and
biological features e.g. seagrasses, mussel beds and bird populations. Digitally-enhanced
remote sensing from satellite or aircraft is useful for determining environmental
conditions such as water depth, suspended sediments, temperature and effluent plumes.
Wide-scale surveying by techniques such as remote sensing will provide valuable
information necessary for the planning of biological surveys by conventional techniques
such as core-sampling. More detailed information is given by Baker and Wolff (1987),
Curran (1985) and Gierloff-Emden (1982).
Subtidal mobile sandbanks
i. Direct sampling
Quantitative substratum samples can be obtained by lowering equipment from vessels.
This includes the Van Veen or Day grabs (for less-compacted sediments), Hamon or Shipek
grabs (for coarser or compacted sediments), Craib and Knudson cores in soft sediments, or
the Reineck box corer, and Forster anchor dredge (for semi quantitative sampling of mobile
megafauna). These techniques provide standardised and quantitative data for statistical
analysis and comparison across surveys although the sample collection and analysis is time
consuming. Diver-operated suction corers can give undisturbed samples with precise
positioning. Site conditions, size of vessel and previous experience will dictate which
equipment is most suitable (see Holme & McIntyre 1984; Kramer et al 1994;
In areas where the epifaunal and demersal fish components are important, small beam
trawls fitted with tickler chains can be towed for a fixed time, for example 20 minutes,
to give a semi-quantitative estimation. Such samples can be fully analysed on board.
ii. Towed and remote operated video
Still and video photography of the bed, by towed or deployed cameras or by diving, are
of limited use in quantifying the fauna of mobile sandbanks as most of the biota are
within the substratum. However, the techniques may be valuable in planning a survey
strategy. Towed and remote operated vehicles, supporting still and video cameras, can
visually record large expanses of the seafloor and are not restricted by depth or time as
with diving (CEC, 1989). (See Donna, 1998; Service, 1998; Michalapoulos et al
The techniques can give semi-quantitative estimations of faunal abundance as well as
providing a permanent visual record of the epifauna and seabed topography. However, the
use of the techniques and the analysis of film may be costly. Turbidity, caused by the
equipment moving on the sandbank, is less likely to cause difficulties than on softer
sediments although the strong tidal currents may affect the use of these systems. The
systems require ground-truthing using conventional grab and core techniques but they do
provide a greater coverage of the biological features of a biotope compared with the very
limited coverage given by those conventional sampling techniques.
Sediment profile imaging (SPI) techniques (e.g. REMOTS) have a large use in sediment
analysis and can determine the features such as degree of bioturbation, and redox and
grain characteristics (Elliott, 1991). They provide a rapid indication of these features
and thus may be used in survey design. However, the techniques are less suitable for
compacted sands (SOAEFD, 1996).
iii. Acoustic survey
Acoustic methods such as side-scan sonar and the RoxAnn® system have a high
value in discriminating the surface features of biotopes. They can be used to survey large
areas but require ground-truthing by conventional sampling and photographic techniques
(see Rees & Foster Smith, 1998).
The meiobenthic fauna is little-studied but plays an important role in the functioning
of the community and is valuable in detecting change. The organisms occur in high
densities, hence sub-sampling or the use of small sample areas is required, and the
community in subtidal sandbanks is likely to be diverse. However, the taxonomic expertise
for their study is not yet widely available although methods are being developed (SOAEFD,
1996). If meiofauna are to be examined they should be sampled concurrently with the
macrofaunal samples if this is feasible.
Meiofaunal sample sizes are smaller than for macrofauna and require cores ranging from
2 to 4 cm diameter, depending on the nature of the sediment. These can be taken
intertidally and subtidally either from grab samples or directly using Craib corers which
reduces disturbance of the surface sediment. Elutration and centrifugation followed by
microscopic examination are required to extract and analyse the samples (Schwinghamer,
1981) and the time-consuming nature dictates that few samples can be analysed in detail.
See the methodologies in Holme and McIntyre 1984; Baker and Wolff, 1987; Kramer et al;
The study of bird communities will indicate maintenance of the integrity of the many
Special Areas of Conservation. This is especially so as both the intertidal mud and sand
flats and the subtidal mobile sandbanks may support nationally or internationally
important populations of birds. It is necessary to monitor the bird communities, for
example using WeBS counts, as they may be characteristic of the biotope complex and will
be important in the ecological dynamics and functioning of the biotope complex.
Bird census techniques are detailed in Baker and Wolff (1987) and Bibby et al
(1992). Such techniques are required to determine the size of the bird communities
associated with the biotope complexes and thus the carrying capacities of those areas.
The continued maintenance of juvenile fish populations over intertidal sand and
mudflats and subtidal mobile sandbanks will indicate the health and integrity of the
biotope complexes. Hence it is necessary to identify any nursery areas and areas with
sensitive species and trends should be monitored against previous data in order to
determine any major changes. Sampling will be primarily by trawls, especially beam
trawling, and fixed netting, including traps, and water quality and sediment information
will be required to interpret the data produced. In contrast to methods for the other
biological components, each fish capture method is species and area specific; details of
methodologies required are given in Morris (1983), Baker and Wolff (1987) and Hemmingway
and Elliott (in press).
Further information on:
Monitoring Macrofauna, birds and fish
Characterisation of the biotope