A strategy is presented for analysing marine biological survey data and relating the biotic patterns to environmental data. To avoid circular argument, biotic and environmental data are kept separate. The strategy is illustrated by a worked example using data on the distribution of 182 nematode species in 107 samples in the River Exe estuary. Nineteen stations are grouped Into 4 main clusters using complementary classification and multi-dimensional scaling (MDS) ordination techniques. These are both based on root-root transformed abundance data with the Bray-Curtis measure of similarity. Indicator species characterising each group are extracted using information statistics. Inverse analyses give clusters of co-occurring species which are strongly related to the station groups. Relationships of station groups to environmental variables are revealed by superimposing data for one variable at a time on the MDS plot, showing that some station groups differ in sediment granulometry and others in salinity, for example. Some of the other factors plotted show no difference between station groups. Similarly, physiognomic characteristics of the species are superimposed on the MDS plots of the inverse analysis of species groups, revealing differences in setal length and trophic status between the species groups. Finally, the 4 major station groups and species groups are related to one another in terms of morphological adaptation to the habitat.

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A practical strategy for analysing multispecies distribution patterns

Benthic macrofauna was sampled by grab at 16 stations in Hampton Roads and the adjacent Elizabeth River, Virginia, USA. Samples were taken in February, May and August. Sampling sites and species were grouped by a classification strategy which basically consisted of the Canberra metric dissimilarity-measure and flexible and group average clustering. Following reallocations, 8 site groups and 16 species groups instructively classified the 47 sites and 93 species considered in the analysis. The sites were grouped into “associations” on mud, muddy-sand and sand-bottom, and those in the Elizabeth River. Species groupings distinguished a few species most frequent at Elizabeth River or mud and muddy-sand sites, larger numbers of species restricted to muddy-sand and sand or solely to sand sites, ubiquitous species, epifaunal species which were microhabitat-restricted, and seasonal species. An analysis of numerically dominant species in the different associations indicated the relative importance of ubiquitous species and seasonally abundant species. Community-structure statistics (species diversity, species richness and evenness) showed definite spatial and temporal patterns. Diversity was high at sand and muddy-sand sites and low at mud and Elizabeth River sites. This spatial pattern was predominantly one of species richness. At Elizabeth River and mud stations, diversity increased from February to August because of increased evenness, while at sand and muddy-sand stations, diversity peaked in May in response to both high species richness and high evenness. The applicability of “community concepts”, the causes of substrate specificity, seasonality and species diversity, and the effects of pollution on community structure are discussed.

Classification and community structure of macrobenthos in the Hampton Roads area, Virginia

The distribution of benthic communities in the Strait of Georgia is partially determined by the relative areas of various sediment types, their depths, and characteristics of overlying water. Rocky shores, which account for 88% of the shoreline length, have been fairly closely examined and communities have been described in the context of worldwide zonation patterns. The ecology of macrofauna and meiofauna of unconsolidated sediments at several estuaries (Nanaimo, Fraser, Squamish) has been documented. In eelgrass beds, very diverse invertebrate communities are found, whereas in brackish marshes closer to river mouths the ecosystem is characterized by a few very abundant species. To date, between 325 and 350 macroalgae species have been recorded from the shallow subtidal habitats of the Strait. In an intensive study at Bath Island, 10 algal communities were defined, each with an associated faunal group. The deep subtidal habitats are extensive: 71% of the surface area of the bottom of the Strait is betwee...

Review of the Benthos of the Strait of Georgia and Contiguous Fjords

Publisher Summary The purpose of this chapter is to examine the development of practical analytical approaches that have traditionally been applied to benthic soft-bottom macrofaunal (particularly marine) studies. 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. 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. The primary aim of all methods discussed here continues to be the simplification of complex patterns occurring in benthic faunal assemblages, such that interpretation and comparison is possible. The key to further progress in this field is to develop sampling and analytical techniques in concert. This presupposes that research aims and study hypotheses can be more clearly stated in benthic studies than has often been the case in the past.

The Development and Application of Analytical Methods in Benthic Marine Infaunal Studies

Epibenthic (trawlable) macrofauna and hydrographic variables were sampled at ten stations in the Calcasieu estuary, Louisiana, from June, 1974, through February, 1976. The 100 otter trawl samples collected contained 32,221 individuals belonging to 63 invertebrate and 68 fish species. The 10 most abundant fish and invertebrate species represented 95.3 and 90.0%, respectively, of the total number of individuals collected. Seasonal variation in numbers of species and individuals were similar, with significant increases in number of species during spring and early summer months. Numerical classification was used to analyze spatial and temporal patterns of utilization of the estuary and to examine correlates of demographical variation and assemblage structure. Eight site groups and seven species groups were allocated by normal and inverse analyse^, respectively. Four of the site groups were seasonally restricted, two were habitat restricted and two were both habitat and seasonally restricted. Nodal analyses identified patterns of constancy and fidelity, with spatial and temporal partitioning of the estuary by the species groups. Biotic interactions were implied by separation of congeners or closely related species into different species groups having separate centers of distribution. Diversity and evenness values, although not utile in assessing areal and seasonal patterns of fluctuations in assemblages, did delimit structural differences in closely related species groups. A relatively straight, deep ship channel extended the length of the

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Spatial and Temporal Variations in Community Structure of the Demersal Macrofauna of a Subtropical Estuary (Louisiana).

A Zurich-Montpellier analysis provided more detailed information about pelecypod associations in two sediment beds than either a traditional subjective approach or a cluster analysis based on Jaccard's coefficient. The Zurich-Montpellier test separated till and sand pelecypod associations, and indicated distinguishing species and atypical samples. Species distinguishing the till association were Cardita ventricosa, Yoldia myalis, Semele rubropicta, Venerupis kennerlyi, Clinocardium nuttallii, Nuculana minuta and Macoma incongrua. Species distinguishing the sand were Macoma elimata, Compsomyax subdiaphana, Yoldia ensifera, Macoma calcarea, M. lipara, M. brota, Yoldia limatula and Macoma alaskana. Two samples contained species from both associations plus some species rare elsewhere. Combined R-and Q-type grouping procedures, of which the Zurich-Montpellier approach is an example, are useful in evaluating benthic faunal similarities, but the suitability of various forms of the procedure needs further study.

D. V. Ellis

Papers

A comparison of traditional, cluster and Zürich-Montpellier analyses of infaunal pelecypod associations from two adjacent sediment beds