[Advances in Marine Biology] Advances in Marine Biology Volume 26 Volume 26 || The Development and Application of Analytical Methods in Benthic Marine Infaunal Studies

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<ul><li><p>The Development and Application of Analytical </p><p>Methods in Benthic Marine Infaunal Studies </p><p>Brenda J. Burd,' Amanda Nemec2 and Ralph 0. Brinkhurst3 </p><p>'Galatea Research Inc., Brentwood Bay, 'International Statistics and Research Corp.. Brentwood Bay and 30cean Ecology Laboratory, Institute of </p><p>Ocean Sciences, Sidney, British Columbia, Canada </p><p>I. Introduction . . . . . . . . . . 11. Collection of Data . . . . . . . . </p><p>A. Sampling devices , . . . . . . . B. Sieving of samples . , . . . . . . C. Sampling effort . . . . . . . . D. Temporal sampling design , . . . . . </p><p>111. Analysing the Data Matrix . , . . . . A. The data matrix . . . . . . . . B. The subjective approach: Community concepts C. Descriptive univariate community indices . . D. Statistical inference . . . . , . . . E. Multivariate data analyses , . . . . . F. Time-series analysis , . . . . . . . </p><p>IV. Summary , . . . . . . . . . . . V. References . . . . . . . . . . . . </p><p>ADVANCES IN MARINE BIOLOGY VOLUME 26 ISBN 0-12-026126-X </p><p>. . . . . . . . 170 </p><p>. . . . . . . . 172 </p><p>. . . . . . . . 173 </p><p>. . . . . . . . 174 </p><p>. . . . . . . . 175 </p><p>. . . . . . . . 177 </p><p>. . . . . . . . 178 </p><p>. . . . . . . . 178 </p><p>. . . . . . . . 186 </p><p>. . . . . . . . 192 </p><p>.. . . . . . . 212 </p><p>. . . . . . . . 214 </p><p>. . . . . . . . 231 </p><p>. . . . . . . . 232 </p><p>. . . . . . . . 234 </p><p>Copyright 0 19W by Academic Press Limited AN rights of rrproduclion in m y form reserved </p><p>169 </p></li><li><p>170 B. J. BURD E T A L . </p><p>I. Introduction </p><p>The purpose of this review is to examine the development of practical analytical approaches that have traditionally been applied to benthic soft- bottom macrofaunal (particularly marine) studies. We hope to provide some insight into why certain approaches are used, and the assumptions and resulting limitations of these methods. A thorough review of all methods ever used by benthic researchers is impossible and unnecessary, as specific reviews are available on many topics and will be referred to. Theoretical aspects of ecology are not examined in detail, but reference to recent treatments is included for those who have the time and energy to delve into such issues. Some commonly applied methods and topics are covered in more detail than others, especially if they are considered to be pivotal in the development of benthic analytical studies. It is felt this type of review is useful because of the diffuse nature of the large volume of literature and research in benthic ecology. For ecologists recently embarked on benthic studies, sorting through this literature is a difficult task. In order to design a survey program, it is important to consider why certain theories are currently popular. Are they logical developments of trial and error, honest representations of well thought out hypotheses or just trendy? Our bias towards certain methods may be obvious to the reader, but there is no formal attempt to declare a right or wrong approach. This is a rapidly changing field and the review can only be considered up to date as of December 1988. </p><p>In this review, benthic studies include what Hurlbert (1984) described as mensurative or survey research, which is non-experimental. Mensurative studies involve random sampling of the organisms (and related factors) from different stations, selected according to some reasonable survey pattern based on the objectives of the study. Our treatment is limited mainly to the literature on the remote sampling (shipboard) of marine macrobenthic infauna inhabiting soft substrata. Examples of studies and theories derived from meiofaunal, intertidal, freshwater and some land-based study areas are included where they have contributed to marine benthic survey theory. </p><p>There are three basic issues which have been prominent in benthic ecological research in one form or other over the years. These are: </p><p>( I ) What is the most efficient and accurate method of identifying and describing the underlying faunal structure of a sample? How does this depend on the concept of a community in benthic ecology? </p><p>(2) How can the faunal structure of samples be distinguished from each other over time and space? </p><p>(3) How do natural and anthropogenic habitat variables affect the faunal </p></li><li><p>BENTHIC MARINE INFAUNAL STUDIES 171 </p><p>structure of samples, and can these two types of effects be dis- tinguished? </p><p>From time to time, attempts have been made to synthesize or standardize approaches to benthic sampling and analysis (for recent examples, see Boesch, 1977; Verner et al., 1985; Chapman et al., 1987; Becker and Armstrong, 1988), or to discuss statistical problems, sampling practices and new methods (cf. Green and Vascotto, 1978; Tetra Tech Inc., 1986; GEEP workshop, Mar. Ecol. Prog. Ser. 46, 1988). Recently, Lopez (1988) discussed the comparative aspects of limnological and marine benthic macrofaunal studies, a rare effort indeed. </p><p>Section I1 of this chapter defines sampling terms and basic sampling considerations. Sampling design is very much dependent on the objective of a study. Therefore it is virtually impossible to describe the right or wrong way to sample data. The important sampling parameters (size and number of samples) can only be confidently decided upon after preliminary reconnaissance sampling and analysis of data from the study site. Therefore, most methods for sampling design are reviewed along with the appropriate discussion of analytical methods in Section 111. </p><p>Section I11 discusses the organization (1II.A) and analysis (1II.B-1II.E) of data in benthic studies, starting with the simple methods developed early in benthic ecological study, and progressing to the currently popular computer- intensive multivariate methods. The development of each stage in analysis has continued in parallel to some extent. Therefore, the discussion does not attempt to present a chronology of methodological development. The types of analysis in order of discussion include: </p><p>Section IZI.B: The subjective approach: Community concepts. An under- standing of the term community and such related concepts as con- tinuum is perhaps the primary requirement for the analysis and interpret- ation of benthic survey data. Petersens pioneering work in the early 1900s marks the first serious attempt to tackle these issues. Although Petersen used subjective methods to describe and compare benthic communities, he recog- nized the need for an objective and systematic approach. However, it was only with the development of computer technology that the necessary methods were to become readily available. Consequently, more or less subjective methods were employed until recently, and many continue to be used today. For example, in limnology, the Theinemann school of lake typology, which advocates the use of characteristic taxa to identify com- munities, is in this philosophical paradigm (Brinkhurst, 1974). </p><p>Section 1ZI.C: Descriptive univariate community analysis. Since Petersens </p></li><li><p>172 B. J. BURD E T A L . </p><p>time, ecologists have sought to describe communities using graphical and mathematical models which reduce all the data from a given sampling station to a single number, index or function. Univariate models do not recognize the multidimensional effects of species interacting with each other. Nevertheless, their simplicity makes these models popular, particularly in pollution contexts. This phase in the evolution of an objective methodology is dominated by the diversity index in applied aquatic studies in North America, and by the pseudoquantitative Saprobian system once popular in Europe (cf. Leppakoski, 1977), particularly in freshwater studies. </p><p>Section ZZZ.D: Most of the recent advances in inferential hypothesis testing have focused on computer-intensive descriptive analytical methods, which are often too complex to interpret subjectively. Of particular interest is the recent proliferation of non-parametric simulation techniques for significance testing of large and complex data sets. </p><p>Section ZZZ.E: Multivariate community analysis. Though some of these methods are quite old, they have gained wider acceptance in recent years than the methods discussed in Section 1II.C. These methods incorporate the multidimensionality of species relationships within benthic assemblages. </p><p>Section ZZZ..F: Most time-series studies use multivariate methods because of the increased dimensional complexity added by temporal considerations. Time-series studies are still relatively rare, but are increasingly becoming prevalent in the literature as computer-intensive multivariate methods develop. </p><p>The primary aim of all methods will continue to be the simplification of complex patterns occurring in benthic faunal assemblages so that interpret- ation and comparison is possible. Much of the audience for simplified reporting of complex taxonomically based data sets consists of environ- mental managers, engineers and political agencies that no longer accept the tlitist testimony of experts, particularly when major industrial or other developments clash with environmental concerns. </p><p>II. Collection of Data </p><p>In this section, we review briefly four important aspects of benthic surveys: the choice of a suitable sampling device, the sieve size, the number and spatial distribution of the samples, and the timing of samples. We make no attempt to give a specific set of guidelines. The purpose is simply to highlight the main issues, many of which continue to be debated, and which are reviewed elsewhere. </p></li><li><p>BENTHIC MARINE INFAUNAL STUDIES 173 </p><p>We will refer to the data collected from one unit of sample effort, whether by grab, core, quadrat, photograph, trawl or other, as the sample unit or replicate. The term sample has been used in benthic studies in a variety of different ways, but usually corresponds to the data for a station (i.e. it includes all the replicates from a designated site, for which all variables are measured). The reader will also find throughout this chapter that sample in inverse analyses means the total complement of a given taxon across all sample units. Therefore, where the distinction is important, the term station will be used to indicate the total data complement of the sample units for one designated site. </p><p>A. Sampling Devices </p><p>The vast array of grabs, cores, sleds, trawls, suction samplers, etc., which have been used for benthic survey research preclude an effective review in this chapter. Grabs and cores have traditionally been used for quantitative sampling of infaunal animals since the early 19OOs, whereas sleds, dredges and trawls have been used for qualitative sampling of larger and more dispersed epifauna. </p><p>Thorson (1957) drew attention to the problems caused by the shock wave created in front of many sampling devices as they approach the bottom. Since that time, there have been a number of good descriptive reviews of sampling devices (Holme, 1964; Hopkins, 1964; McIntyre, 1970; Eleftheriou and Holme, 1984). Statistical tests have been published relating to the relative efficacy of different samplers. Grab or core-type samplers can profoundly affect the quantitative results from coarse sediments and at shallow depths (Wigley, 1967; Christie, 1975; Tyler and Shackley, 1978; Hartley, 1982). Gerlach et al. (1985) pointed out that the loss of meiofaunal animals using remote grabs or cores was very high compared to direct sampling (such as SCUBA). </p><p>Rutledge and Fleeger (1988) describe a laboratory experiment on the efficiency of sampling the meiobenthos with respect to core penetration rate. Hartley (1982) cites an example of an inter-calibration experiment between laboratories from which he concluded that differences in results were related partially to the differences in design of two different Van Veen grabs. Dybern et al. (1976) reviewed and recommended standard procedures for sampling in the Baltic Sea, in order to avoid sampling discrepancies between studies. Many authors have their own justifications and reasons for using specific sampling devices, or make it clear that convenience or cost is of primary importance. For limnological sampling, reviews include Brinkhurst (1 974) and Edmondson and Winberg (1971), while Hartley and Dicks (1987) provide a review of sampling methods in estuaries. </p></li><li><p>174 B. J. BURD E T A L . </p><p>B. Sieving of Samples </p><p>An important consideration in quantitative sampling of the benthos is choice of screen size. Historically, benthic fauna have been delimited into three groups based on the size of organisms trapped by different sized screens (see Reish, 1959; Thorson, 1966; Schwinghamer, 1981; Warwick, 1984; Gerlach et al., 1985; Platt, 1985). In general, researchers have recog- nized up to four size groups usually referred to as microbes (bacteria, etc.), meiofauna (including foraminifera and the smallest invertebrate fauna), macrofauna (most of the biomass of benthic animals) and megafauna (often lumped with macrofauna; low in abundance but with high individual biomass). Over the years, there has been disagreement as to the optimum screen sizes for benthic studies, although most researchers have focused on the middle (macrofauna) group. </p><p>Reish (1959) indicated that a screen as small as 0.27mm is required to sample 95% of the animals, whereas a 1-mm mesh will sample 95% of the biomass, and therefore all of the megafauna and most of the macrofauna. The 1-mm mesh screen has been applied most often in pollution monitoring studies of macrofauna and in those studies in which the primary concern is to sample most of the biomass of the animals present (cf. Pearson, 1975; Poore and Kudenov, 1978a,b), whereas studies concerned with meiofauna commonly employ 0.063- to 0.1-mm mesh screeens. More recently, Holme and McIntyre (1984) have recommended the lower size limit of 0.5 mm for macrofaunal sampling, based on their belief that the smaller macrofauna are an important component of benthic assemblage structure even if they do not make up a significant portion of the biomass. Rees (1984) also notes that many polychaete species fragment into pieces smaller than 1 mm during shipboard processing, and recommends the use of 0.5-mm screens. Becker and Armstrong (1988) recommend an initial sieving with a 1-mm screen, followed by a secondary sieve with a 0.5-mm screen (the material from the latter may or may not be processed, but is available if required). The choice of screen size obviously depends on the objectives of the study. For example, in areas of gross pollution, there may be no macrofauna. Therefore, the only sensible sampling program may be designed to capture meiofauna, as some meiofaunal species tend to be more tolerant than the macrofauna. Studies of energy flow or respiration may require a more comprehensive sample. The smaller the screen, the greater the cost and time required to process samples, particularly if taxonomic expertise for the smaller groups is not readily available. (For more detail on the functional s...</p></li></ul>