A Review of Sublittoral Monitoring Methods in Temperate Waters: a Focus on Scale

doi:10.3723/ut.28.099 International Journal of the Society for Underwater Technology, Vol 28, No 3, pp 99–113, 2009 A review of sublittoral monitoring methods in temperate waters: a focus on scale HB Van Rein, CJ Brown and R Quinn Technical Paper Centre for Coastal and Marine Research, School of Environmental Science, University of Ulster, Coleraine, Northern Ireland J Breen Northern Ireland Environment Agency, Belfast, Northern Ireland Abstract the extent of compliance with a predetermined A plethora of methods to monitor shallow sublittoral standard or the degree of deviation from an benthic habitats and communities are available to expected norm'. Monitoring has also been defined the marine researcher today. The most widely used as: `sampling in time with adequate replication to methods are reviewed and evaluated, with reference detect variation over a temporal range from short to the spatial scale at which they operate. For ease and long time periods, done at more than one loca- of comparison, methods are categorised as operating tion', (Kingsford and Battershill, 1998). Ecological over broad (>1km), meso (10m–1km) and fine scales monitoring programmes are specifically designed (<10m). A measure of efficiency and data resolution are to detect trends or changes from normal conditions provided by exploring the range of sampling techniques or a predetermined standard over time. Equally, and strategies at each of these spatial scales. they may monitor the progress of ecological change Recommendations are made regarding which methods and provide evidence of the efficacy of legislative are most effective at each scale: light detection and directives (Goldsmith, 1991). ranging (LIDAR) and multibeam sonar over broad Predetermined targets are, therefore, necessary scales; sidescan sonar, drop-down cameras, towed for the basis of a monitoring programme and will cameras and remotely operated vehicles (ROVs) over drive what needs to be monitored, where the mon- meso scales; and grab samplers, sediment corers for itoring will take place, when and in what manner soft, unconsolidated sediments and photoquadrats, the monitoring is to be conducted, and at what and video transects for hard, consolidated sediments frequency will samples be collected. The practical at fine scales. Emphasis is placed on the development issues related to what sampling equipment is best of standardised methodologies for sampling each scale suited to survey different sublittoral environments within a nested design, for the monitoring programmes and community assemblages, as well as at what of the future. sampling scales should these surveys be conducted, need to be appropriately addressed before the onset Keywords: marine, benthos, monitoring, scale, of any monitoring programme. temperate, resolution This review attempts to answer the methodolog- ical questions of scale, habitat and community by providing an account of current monitoring 1. Introduction methods available to marine researchers. In the The status of the seas and oceans is of increasing dynamic and growing field of marine habitat importance to conservation agencies, marine-based characterisation, varied sampling techniques are industries and government departments worldwide. employed by researchers. Rather than compile Evaluating status of the marine environment is an extensive list of methods and research equip- linked strongly with effective monitoring that may ment, which have been covered adequately in be employed for the accurate assessment of re- previous reviews (Kingsford and Battershill, 1998; sources (such as fish stocks, mineral deposits and Eleftheriou and McIntyre, 2005; Coggan et al., hydrocarbon reserves), marine habitats and pollu- 2007), this account consolidates current monitor- tant levels and for making reliable observations and ing research and makes recommendations for the informed predictions. monitoring programmes of the future based on The concept of monitoring is defined by current technological developments. Goldsmith (1991) as: `intermittent (regular or irreg- In Europe, recent international legislation, such ular) surveillance carried out in order to ascertain as the EU Habitats Directive (Council Directive 99 Van Rein et al. A review of sublittoral monitoring methods in temperate waters: a focus on scale 92/43/EEC on the conservation of natural habitats their associated environment; `community' is most and of wild fauna and flora, 1992) and the Water closely related to the dynamic assemblage of species Framework Directive (WFD 2000/60/EC, 2000), living within a habitat; and `biotope' is seen as a has spurred marine agencies and institutions into blend of the two, with both habitat and community developing a range of monitoring programmes to as one functional unit. suit a variety of environmental concerns. These programmes have to meet the challenges of 2. Communitymonitoring(fine-scalemethods) sampling scale, resolution and robustness over time, The biological component of any monitoring pro- yet be practical and cost-effective in a challenging gramme requires the collection of high resolution environment. However, marine monitoring of data from fine spatial scales (0.01–10m) to facili- temperate waters has historically developed slower tate accurate species identification. As species are than that in tropical waters (Davies et al., 2001; Hill present within a habitat at micro-, meio- and macro- and Wilkinson, 2004; Jokiel et al., 2005; Coggan faunal scales, it is also necessary to determine which et al., 2007). In the tropics, field survey conditions species are to be targeted and at what scale should are more amenable to all scales of marine research, the surveys operate. Once a species or assemblage and well established programmes conducted at has been targeted, it is important that sampling community, government and research institute equipment appropriate to the size and ecology of levels of expertise have been operating for some that species is selected for monitoring to avoid time (Hill and Wilkinson, 2004). Indeed, the better misrepresenting it in the data. Usually conspicuous developed areas of tropical marine research may macrofauna (0.01–1.00m scale), indicative of a be of great benefit to the contemporary areas of particular habitat or environmental condition, are temperate marine research programmes, an issue selected for monitoring. In this way the presence, which is addressed in this review. absence, abundance and percentage cover of these In contemplating these issues, this account biota can provide proxy indicators of the status of covers the most common methods used to monitor the environment (Goldsmith, 1991). shallow (0–40m) sublittoral benthic communities At the scale of centimetres to metres, soft and from temperate waters, incorporating tropical hard substrata present the researcher with very methods where appropriate. The benthos has been different conditions in which to monitor. At these regarded as a good indicator of environmental fine scales, the methods best employed within each condition and quality (Alden et al., 1997), and broad habitat type are very different as a direct the majority of conservation work and research result of the physical substratum. efforts are likely to occur in the shallow sublittoral zone (encompassing the infralittoral and shallow 2.1. Soft substratum community monitoring circalittoral zones). Limiting this review to shallow Unconsolidated sediments of soft substrata, con- water benthic environments will cover a large sisting of varying proportions of clay, mud, silt, degree of the current monitoring effort. sand and gravel, typically support rich infaunal The present account is divided into three broad communities of meio- and macro-fauna, along with sections: spatial monitoring, which reviews the motile epifaunal communities. Habitats within soft methodologies used to map and identify habitats substratum areas can cover vast regions of seabed at a range of different spatial scales; community (e.g. abyssal plains), but are considered to be monitoring, which reviews the high resolution relatively homogenous in terms of the community methods used within those habitats to qualify and assemblage within each habitat (Zajac, 2008). quantify fine-scale biological communities (from Methods used to sample these communities both soft and hard benthic substrata); and biotope at fine scales have changed little over the past monitoring, which reviews a newly emerging area of century, with the exception of sediment profile marine monitoring where habitat- and community- imagery, or SPI (Solan et al., 2003). Samples based methods are blended to study meso-scale from the seabed have been collected through changes in marine environments. These sections the physical removal of known areas of seabed are discussed in order of ascending spatial scales, brought to the surface, where they are usually from fine-scale community monitoring, through sieved (to remove larger particles of sediment) meso-scale biotope monitoring, to broad-scale and sorted to identify the biota. Sediment grab habitat monitoring methods (Table 1). samplers have proved effective for this task and are For the purposes of consistency, the concepts used widely today (Kingsford and Battershill, 1998; of habitat, community and biotope used in this Elías et al., 2005; Lu and Wu, 2007). A variety of paper are taken from Olenin and Ducrotoy (2006). grab samplers (such as Petersen, Campbell, Day, In brief, `habitat' is related most to the physical van Veen, Shipek,

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