Macrofauna

Meiofauna

Birds

Fish

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 monitored.

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.

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).

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; Thomas, 1998).

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 1992.)

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; 1994.

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

Monitoring change

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