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Ecological survey strategy
Ecological Survey Strategy The marine ecologist concerned with studying pollution is involved with one or both of two questions. First, at this point in time, is there an ecosystem p a t t e r n correlated spatially with areas of pollution, and second, given the spatial p a t t e r n of ecosystems t o d a y , how will this p a t t e r n by modified by future extension or intensification of pollution? Data drawn from an investigation of the sublittoral kelp holdfast ecosystem (Laminaria hyperborea (Gunn.) Foslie.) along the north-east coast of Britain, as part of the north-east marine pollution programme for IBP, will be used to illustrate the author's approach to the first p r o b l e m and to precede an a t t e m p t e d general formalization of strategy which may prove b o t h useful and controversial. Seventy-two holdfast samples from fifteen approximately equidistant sites from St. Abbs, Berwickshire to Flamborough Head, Yorkshire were collected in J u l y 1969 by SCUBA divers at as near as possible one instant in time, that is during one spring tide p e r i o d (Fig. 1). Five holdfast samples were taken at m o s t sites in individual plastic bags secured under water. The central zone of the sampled area receives effluent from the industrial and domestic complexes at the mouths of the Rivers Tyne, Wear a n d Tees. Colliery ~aste from the N o r t h u m b e r l a n d a n d Durham coalfield is also d u m p e d along this stretch of coastline (ICES report no. 13, 1969). Total macro- a n d meiofaunal c o n t e n t o f the samples was established (with the exception of Protozoa, Porifera and Platyhelminthes) and a m o u n t e d to some 90,000 animals of 387 species from most invertebrate phyla. Various approaches have been and are being used to elucidate the pattern of relationship exhibited by the fauna o f these samples. It is inappropriate to include detailed results here but the following outline is relevant. Preliminary ordering of the data was accomplished using the classificatory multivariate technique o f association analysis (Williams & Lambert, 1959, 1960, 1961) based on qualitative i.e. presence/absence attribute occurrences. Normal association analysis has led to a classification o f samples based on species attributes. This hierarchy has been considered at an arbitrarily selected five-community level and the independence of the sample grouping so p r o d u c e d tested against the distribution of likely environmental factors recorded at the time of the survey. The d i s t r ~ u t i o n of the physical parameters of turbidity, 'poUution' and water movement (as strong current), each a c c o u n t signiiicandy for the partition of the samples into the fivecommunities. The distribution of holdfast m o r p h o m e t r i c parameters does not. Methodological limitations arising from t h e m o n o t h e t i c nature of association analysis, and special considerations relating to the F a m e Islands and F l a m b o r o u g h samples cause interpretational difficulties over communities 4 and 5. C o m m u n i t y I is, however, highly associated with clear, unpolluted waters; c o m m u n i t y 2 with turbid, u n p o l l u t e d waters; and c o m m u n i t y 3 with t u r b i d p o l l u t e d waters. Inverse Association Analysis leading to a classification of the 387 species individuals based on their sample (i.e. distributional) attributes has been c o m b i n e d with the normal hierarchy to p r o d u c e a two-way table enabling recognition of doubly defined species/site groupings. Objective recognition of certain species or groups o f species characterizing areas of differing water quality has thus been achieved. The following major species/site groupings can be distinguished (1) a group of ubiquitous species occurring across the five communities of the Normal .~malysis, (2) a group of species confined to the clear water c o m m u n i t y 1, (3) a group of species occurring in the turbid u n p o l l u t e d
c o m m u n i t y 2, only a p r o p o r t i o n of which occur in the turbid polluted c o m m u n i t y 3 and (4) a group of potentially ubiquitous species which do not occur in the turbid p o l l u t e d c o m m u n i t y 3. By this m e t h o d of analysis, the 115 species in the groups above out of the total of 387 considered, carry the bulk of the ecologically i m p o r t a n t information. Lea~'ing aside the ubiquitous species, the major d i c h o t o m y in the kelp holdfast fauna along the north-east coast is thus associated 2°W
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with differences in seawater turbidity; the clear water fauna of Berwickshire and north N o r t h u m b e r l a n d being distinct from the t u r b i d water fauna to the south. In the latter the p o l l u t e d area is then characterized by the absence o f twelve i m p o r t a n t turbid water species and by the absence of thirty potentially ubiquitous species. Qualitative data derived from a spatial survey of this ecosystem have thus enabled recognition of the following, (1) the level of heterogeneity or scale of pattern, (2) correlation of faunal p a t t e r n with habitat pattern, and (3) recognition of c o m p o n e n t s of the total system whose distribution is correlated with the distribution of particular environmental variables. The analysis is therefore predictive and restrictive. Predictive in that experimental and field survey work using the significant c o m p o n e n t s of the total system could now be undertaken, and restrictive in that a number of habitat factors and the bulk o f the species could be ignored in future work directed towards monitoring the faunal pattern associated with the significant environmental variables along the north-east coast. It is my purpose here to propose that such a rationale may be of wider applicability to surveys of marine 37
ecosystems. Any approach must be theoretically capable of detecting pattern and must be sensitive to changes therein. An equally important practical consideration concerns efficiency. In commercial terms our strategy needs a high work-return. Existing and future philosophies must be examined in terms of their relevance to providing answers (not excuses) to the questions posed at the beginning. In outline, it is p r o p o s e d that primary field surveys be spatial in emphasis, qualitative not quantitative, that modern data handling methods be used to store, analyze and correlate total data and indicate nodes of ecological importance, that follow-up experimental and/or p o p u l a t i o n investigation of noda m a y then be applicable, and that temporal variability might be assessed on the basis of any changes in pattern revealed b y subsequent spatial surveys. An emphasis on spatial primary field survey c o m b i n e d with an objective habitat classification will encompass the widescale pattern of marine ecosystems and define their range of expression, that is, degree of heterogeneity. Collection of relevant habitat data relating to each field sample is crucial. Whereas the scale of survey will in all likelihood be limited b y practical rather than theoretical strictures, the advent of high speed computing facilities enables large bodies of information to be stored, analyzed, correlated and recalled at will. Multivariate statistical techniques offer a logical approach to the ordering of complex faunal and/or habitat data collections b u t their use in the marine c o n t e x t is as y e t e m b r y o n i c (see Williamson (1961), Cassie (1967) on p l a n k t o n ; Cassie & Michael (1968) on infauna; Field (1968, 1970) on r o c k y b e n t h o s and the present investigation on a p h y t a l system). Recurrent group analysis (Fager, 1957) has also been little used ( see Fager & McGowan (1963) on z o o p l a n k t o n ; Fager & Longhurst (1968) on fish). The use and application of methods from other disciplines, for example, trend surface analysis and spatial autocorretation m e t h o d s used in geography, is as y e t untested ecologically. Restriction to qualitative rather t h a n ' q u a n t i t a t i v e data may facilitate a more r a p i d field survey and should reduce subsequent sample processing. It is p r o b a b l y a t this p o i n t that the credibility of the scheme breaks down in the eyes of practising marine ecologists. There is no d o u b t that the relative amounts of different species are i m p o r t a n t and this is not denied. It is only questioned whether, in the context of the g o a l ' w e have set ourselves this offers the most efficient approach to the exploration o f c o m p l e x systems. The considerable difficulties involved in a field investigation of spatial and long-term fluctuations in numbers o f animals, such as would be implicit in any quantitative study, have recently been outlined b y Dr. J . g . Lewis (Marine Pollution Bulletin (1970) 1: 53). One would hesitate to e m b a r k on this t y p e of investigation especially with little-known communities until a primary survey had defined significant components. We must also be aware that s t u d y of the numerical fluctuations o f species with time m a y not be the only way to assess ecosystem stability (I leave aside the question of whether fluctuation in numbers has anything to do with stability (Preston, 1969). The use of qualitative data is widespread in plant ecology a n d is becoming increasingly advocated for survey work (Greig-Smith, 1969, and personal communication). A useful strategy might be to undertake a qualitative primary survey of this nature, a n d then, on the basis of the scale of heterogeneity and the relatability o f the faunal p a t t e r n to areas of pollution, decide whether or not immediate experimental a n d / o r detailed p o p u l a t i o n investigation of significant noda is indicated. In the event of a less convincing differential picture emerging, such intensive c o m m i t m e n t of facilities could be p o s t p o n e d until a repeat survey (after perhaps a year) has d e m o n s t r a t e d the consistency or otherwise of the scale of pattern originally observed. Repetition of the primary widescale survey would be a 38
salid theoretical m e t h o d of investigating the stability of pattern at the species structure level, that is, by monitoring any expansion or contraction of species occurrence in relation to habitat components. However, it is as yet impossible to say whether extensive qualitative treatment would detect gradual changes at the c o m m u n i t y or ecosystem level more efficiently than intensive quantitative population studies. Over a period of years a continuing widescale faunistic trend might show up as a directional shift in the relationships between future and present day samples. I believe that the monitoring of change in biological systems at this level of abstraction is possible and should be considered. Ecosystem as opposed to p o p u l a t i o n monitoring is currently also advocated by consideration of system diversity, a concept that has recently become fashionable and is generally accepted to have a bearing on system stability (Margalef, 1968). In this sense the hypothesis purports to involve a measure of ecosystem function which, and space does not permit expansion here, is felt to be largely devoid of empirical evidence. We are well advised meantime to treat the hypothesis as such and beware of assuming it to be axiomatic. It may one day be possible to assess the functioning of complex systems via measurements of their metabolic properties (McNeill & Lawton, 1970; .]. Phillipson, personal communication). However, tmtil some such approach becomes feasible, the field ecologist is essentially concerned with the structure of ecosystems, that is, the recognition and interpretation of pattern and changes therein. In formulating research programmes it is advisable that we weigh the usefulness of all available approaches. We are perhaps little aware of the e x t e n t of possibly relevant progress made along analagous lines of enquiry in terrestrial animal ecology, plant ecology, soil survey, land-use assessment m e t h o d s and geographical analytical techniques. The type of data collected will depend as much on the m e t h o d of analysis chosen as on the precise definition of the programme's objective. Concluding The Pattern o f Animal Communities, Charles Elton outlined the philosophy behind the integrated studies of the terrestrial ecosystems of Whytham Hill as follows • '... the large number of species of plants and animals and micro-organisms, and a g o o d many real problems in t a x o n o m y have made animal ecologists hesitant to investigate whole ecosystems - plant, animal a n d environment. I believe that at every level in science this sort of view is natural, and that one has to make a considerable effort to break through from one level of study to another above it, a n d while doing so to forge through the apparent complexities to a higher level o f integration and arrive at simple ideas applicable to that higher level but invisible from the jungle below. A t each stage the synoptic view will appear superficial to the person working at a less synoptic level. The only way, however, to decide whether or not a particular m e t h o d of ecological survey is rewarding in this way is to show whether it has p r o d u c e d some new concepts on the structure of natural systems'. The rationalization a t t e m p t e d here is put forward in this spirit. Dr .1. R. Lewis is thanked for supervision and criticism of the manuscript. Diving assistance was provided by members of the Department of Botany, University of Durham and East Yorkshire branch of the British Sub-Aqua Club. Dr J o y c e Lambert kindly g-ave advice and made available computing facilities. The project is supported by N.E.R.C. Wellcome Marine L a b o r a t o r y University of Leeds, Robin Hood's Bay, N. Yorkshire, England
P. G. Moore
Cassie, R.M. (1967). IVlathematicai models for the interpretation of inshore plankton communities. 'Estuaries, .-M-kAS'. 509-514. Cassie, R.M. and Michael, A . D . (196g). Fauna and sediments of an intertidal mudflat: a multivariate analysis. 'J. exp. mar. Biol. Ecol'., -°:1-25. Fager, E.W. (1957). Determination and analysis of recurrent groups. 'Ecology', 58:586-595. Fager, E.W. and Longhurst, A . R . (1968). Recurrent Group Analysis of species assemblages of demersal fish in the Gulf of Guinea. iJ. Fish. Res. Bd. Canada', 25: 1405-14Ol. Fager, E. W. and McGowan, J. A. (1"965). Zooplankton species groups in the north Pacific. 'Science', 140:453-460. Field, J . G . and McFariane, G. (1968). Numerical methods in marine ecology. 1. A quantitative 'sir,~ilarity' analysis of rocky shore samples in False Bay, South Africa. 'Zool. Air.', 3:119-137. Field, J. G. and Robb, F. 2". (1970). Numerical methods in marine ecology. 2. Gradient analysis of rocky shore samples from False Bay. 'Zool. Afr.', 5;191-210. Greig-Smith, P. (1969). Analysis of vegetation data: The user viewpoint. 'International Symposium on Statistical Ecology', New Haven, (in press).
I.C.E.S. (1969). Report of the working group on pollution of the North Sea. CM. 1968, A: 13. Margalef, g. (1968). 'Perspectives in Ecological Theory', (Univ. of Chicago Press, Chicago.) McNeill, S. and Lawton, J. H.(1970). Annual production and respiration in animal populations. 'Nature', 2.°5:472-474. Preston, F.W. (1969). Diversity and stability in the biological world, in 'Diversity and stability in Ecological Systems' Brookhaven Symposia in Biology no. 2-0:1-12. Williams, W. T. and Lambert, J. M. (1959). Multivariate methods in plant ecology. I. Association Analysis in plant communities. 'J. Ecol.', 47:85-101. Williams, W. T. and Lambert, J. M. (1970). Multivariate methods in plant ecology.. II. The use of an electronic digital computer for association analysis. 'J. Ecol.', 48: 689-710. Williams, W. T. and Lambert, J. M. (1961). Multivariate methods in plant ecology. III. Inverse Association Analysis. 'J. Ecol.', 49:71 7-729. Williamson, M.H. (1961). An ecological survey of a Scottish herring fishery, IV. Changes in the plankton during the period 1949 to 1959. 'Bull. Mar. Ecol.', 5:207-229.
Pollution Effects on Micro-and Heiofauna of Sand Although the concenti'ations of pesticides and heavy metals in potential sea-food is currently attracting widespread attention, the effects of pollution on lower trophic levels in the sea remain almost unknown. In the sediment ecosystem pollution could have far-reaching consequences at high trophic levels through for example alteration of the composition of important species at low trophic levels in food webs, or by irradication of organisms fundamental to the breakdown processes of the carbon, nitrogen and sulphur cycles. Toxic effects of pollutants have been assessed mainly at high trophic levels (Portman 1970), and only acute effects involving 48 or 96 h L.C.s0 tests have been considered. Of potentially greater long-term importance are the synergistic effects of low levels of pollutants on growth, respiration and fertility rates and the possible alteration of behavioural patterns caused by pollutants. The large size and relatively long life-span of commercially important marine species renders studies of the effects of pollutants on complete life-cycles difficult to accomplish. Thus, smaller animals have a~'antages in pollution research in having short life-cycles and being easy to manipulate experimentally. The effects of pollution on genetic stability is also of fundamental interest and rapidly reproducing species are of importance in this context. Marine sand beaches contain an abundance of micro- and meiofauna which provide ideal experimental material for pollution studies. In addition to being small (by definition) most species have short Life-cycles and undergo direct development, ~Sthout planktonic larvae and a variety of ~'ophic levels exists in accessible communities. A large section of the sand-beach micro- and meiofauna feeds at the primary, trophic level on bacteria and microalgae. As no information exists on the effects of pollutants at this trophic level, a bacterivorous ciliate protozoan and .a -oa.icroa]" v ~ . o u s arch_iannelid were_studie.d. The ciliate, Cristigera spp. was isolated from beach sand at Robin Hood's Bay, using the seawater-ice extraction method
(Uhlig, 1964). Cristigera was cultured on a diet of bacterium Pseudomonas spp.), also isolated from beach sand. The growth characteristics of the bacterium in relation to salinity, temperature and some chemical pollutants were established. From this knowledge an excess of food was maintained in experiments measuring the growth rate of Cristigera. Growth rates of Cristigera were measured as increase in number of cells per unit time, using a Coulter Model A paxticle counter, with periodic direct microscopic examination of sub-samples to check accuracy of counting. The exponential growth phase alone was studied. (A more detailed description o f methods is out of place in the present report and will be given in subsequent papers). A routine temperature of 15°C-*0.5°C and salinity of 34.5-*0.5°/00 were maintained in culture vessels. Each experiment was done in duplicate with an unpolluted control. The archlannelid Dinophilus gyrociliatus O. Schmidt was cultured on a diet of ground deep-frozen spinach (Akesson, 1970), at a temperature of 16 C - 1 C and a salinity of 34.5 -* 0.5 /oo, m sohd watch glasses (2 ml. capacity). The increase in length of ten recently hatched juveniles was measured every two days when the food source and seawater were changed. Growth rate measurements were continued until the Fl generation hatched. The pollutants tested for their effect on growth rate were c o m m o n North Sea pollutants (I.C.E.S. Cooperative Research Report Series A, 1969), namely hea~w metals, phenol, and sulphuric acid. Concentrations usecl were below that cause-d['~o-~'lete inhibition of growth rates, as synergistic effects of low levels of pollutant were the main interests. Experiments followed a 23 factorial design with replication, but will be extended to encompass a 33 factorial design where interaction terms are non-linear. The S 3 factorial design will enable linear, quadratic and cubic components of the response curves to be established, if present. The design will be extended to explore three dimensional response surfaces (Box and Wilson, 1951), o
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.
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39
c o m m u n i t y 2, only a p r o p o r t i o n of which occur in the turbid polluted c o m m u n i t y 3 and (4) a group of potentially ubiquitous species which do not occur in the turbid p o l l u t e d c o m m u n i t y 3. By this m e t h o d of analysis, the 115 species in the groups above out of the total of 387 considered, carry the bulk of the ecologically i m p o r t a n t information. Lea~'ing aside the ubiquitous species, the major d i c h o t o m y in the kelp holdfast fauna along the north-east coast is thus associated 2°W
i°W
•t"
÷
Q°
"I" 56"N
1t
f
RTHUN~B
-ERLAND •t" 55°N
"I"
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NORTH D U'R H A N ~ SEA
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I
R KS H I
I 50km.
with differences in seawater turbidity; the clear water fauna of Berwickshire and north N o r t h u m b e r l a n d being distinct from the t u r b i d water fauna to the south. In the latter the p o l l u t e d area is then characterized by the absence o f twelve i m p o r t a n t turbid water species and by the absence of thirty potentially ubiquitous species. Qualitative data derived from a spatial survey of this ecosystem have thus enabled recognition of the following, (1) the level of heterogeneity or scale of pattern, (2) correlation of faunal p a t t e r n with habitat pattern, and (3) recognition of c o m p o n e n t s of the total system whose distribution is correlated with the distribution of particular environmental variables. The analysis is therefore predictive and restrictive. Predictive in that experimental and field survey work using the significant c o m p o n e n t s of the total system could now be undertaken, and restrictive in that a number of habitat factors and the bulk o f the species could be ignored in future work directed towards monitoring the faunal pattern associated with the significant environmental variables along the north-east coast. It is my purpose here to propose that such a rationale may be of wider applicability to surveys of marine 37
ecosystems. Any approach must be theoretically capable of detecting pattern and must be sensitive to changes therein. An equally important practical consideration concerns efficiency. In commercial terms our strategy needs a high work-return. Existing and future philosophies must be examined in terms of their relevance to providing answers (not excuses) to the questions posed at the beginning. In outline, it is p r o p o s e d that primary field surveys be spatial in emphasis, qualitative not quantitative, that modern data handling methods be used to store, analyze and correlate total data and indicate nodes of ecological importance, that follow-up experimental and/or p o p u l a t i o n investigation of noda m a y then be applicable, and that temporal variability might be assessed on the basis of any changes in pattern revealed b y subsequent spatial surveys. An emphasis on spatial primary field survey c o m b i n e d with an objective habitat classification will encompass the widescale pattern of marine ecosystems and define their range of expression, that is, degree of heterogeneity. Collection of relevant habitat data relating to each field sample is crucial. Whereas the scale of survey will in all likelihood be limited b y practical rather than theoretical strictures, the advent of high speed computing facilities enables large bodies of information to be stored, analyzed, correlated and recalled at will. Multivariate statistical techniques offer a logical approach to the ordering of complex faunal and/or habitat data collections b u t their use in the marine c o n t e x t is as y e t e m b r y o n i c (see Williamson (1961), Cassie (1967) on p l a n k t o n ; Cassie & Michael (1968) on infauna; Field (1968, 1970) on r o c k y b e n t h o s and the present investigation on a p h y t a l system). Recurrent group analysis (Fager, 1957) has also been little used ( see Fager & McGowan (1963) on z o o p l a n k t o n ; Fager & Longhurst (1968) on fish). The use and application of methods from other disciplines, for example, trend surface analysis and spatial autocorretation m e t h o d s used in geography, is as y e t untested ecologically. Restriction to qualitative rather t h a n ' q u a n t i t a t i v e data may facilitate a more r a p i d field survey and should reduce subsequent sample processing. It is p r o b a b l y a t this p o i n t that the credibility of the scheme breaks down in the eyes of practising marine ecologists. There is no d o u b t that the relative amounts of different species are i m p o r t a n t and this is not denied. It is only questioned whether, in the context of the g o a l ' w e have set ourselves this offers the most efficient approach to the exploration o f c o m p l e x systems. The considerable difficulties involved in a field investigation of spatial and long-term fluctuations in numbers o f animals, such as would be implicit in any quantitative study, have recently been outlined b y Dr. J . g . Lewis (Marine Pollution Bulletin (1970) 1: 53). One would hesitate to e m b a r k on this t y p e of investigation especially with little-known communities until a primary survey had defined significant components. We must also be aware that s t u d y of the numerical fluctuations o f species with time m a y not be the only way to assess ecosystem stability (I leave aside the question of whether fluctuation in numbers has anything to do with stability (Preston, 1969). The use of qualitative data is widespread in plant ecology a n d is becoming increasingly advocated for survey work (Greig-Smith, 1969, and personal communication). A useful strategy might be to undertake a qualitative primary survey of this nature, a n d then, on the basis of the scale of heterogeneity and the relatability o f the faunal p a t t e r n to areas of pollution, decide whether or not immediate experimental a n d / o r detailed p o p u l a t i o n investigation of significant noda is indicated. In the event of a less convincing differential picture emerging, such intensive c o m m i t m e n t of facilities could be p o s t p o n e d until a repeat survey (after perhaps a year) has d e m o n s t r a t e d the consistency or otherwise of the scale of pattern originally observed. Repetition of the primary widescale survey would be a 38
salid theoretical m e t h o d of investigating the stability of pattern at the species structure level, that is, by monitoring any expansion or contraction of species occurrence in relation to habitat components. However, it is as yet impossible to say whether extensive qualitative treatment would detect gradual changes at the c o m m u n i t y or ecosystem level more efficiently than intensive quantitative population studies. Over a period of years a continuing widescale faunistic trend might show up as a directional shift in the relationships between future and present day samples. I believe that the monitoring of change in biological systems at this level of abstraction is possible and should be considered. Ecosystem as opposed to p o p u l a t i o n monitoring is currently also advocated by consideration of system diversity, a concept that has recently become fashionable and is generally accepted to have a bearing on system stability (Margalef, 1968). In this sense the hypothesis purports to involve a measure of ecosystem function which, and space does not permit expansion here, is felt to be largely devoid of empirical evidence. We are well advised meantime to treat the hypothesis as such and beware of assuming it to be axiomatic. It may one day be possible to assess the functioning of complex systems via measurements of their metabolic properties (McNeill & Lawton, 1970; .]. Phillipson, personal communication). However, tmtil some such approach becomes feasible, the field ecologist is essentially concerned with the structure of ecosystems, that is, the recognition and interpretation of pattern and changes therein. In formulating research programmes it is advisable that we weigh the usefulness of all available approaches. We are perhaps little aware of the e x t e n t of possibly relevant progress made along analagous lines of enquiry in terrestrial animal ecology, plant ecology, soil survey, land-use assessment m e t h o d s and geographical analytical techniques. The type of data collected will depend as much on the m e t h o d of analysis chosen as on the precise definition of the programme's objective. Concluding The Pattern o f Animal Communities, Charles Elton outlined the philosophy behind the integrated studies of the terrestrial ecosystems of Whytham Hill as follows • '... the large number of species of plants and animals and micro-organisms, and a g o o d many real problems in t a x o n o m y have made animal ecologists hesitant to investigate whole ecosystems - plant, animal a n d environment. I believe that at every level in science this sort of view is natural, and that one has to make a considerable effort to break through from one level of study to another above it, a n d while doing so to forge through the apparent complexities to a higher level o f integration and arrive at simple ideas applicable to that higher level but invisible from the jungle below. A t each stage the synoptic view will appear superficial to the person working at a less synoptic level. The only way, however, to decide whether or not a particular m e t h o d of ecological survey is rewarding in this way is to show whether it has p r o d u c e d some new concepts on the structure of natural systems'. The rationalization a t t e m p t e d here is put forward in this spirit. Dr .1. R. Lewis is thanked for supervision and criticism of the manuscript. Diving assistance was provided by members of the Department of Botany, University of Durham and East Yorkshire branch of the British Sub-Aqua Club. Dr J o y c e Lambert kindly g-ave advice and made available computing facilities. The project is supported by N.E.R.C. Wellcome Marine L a b o r a t o r y University of Leeds, Robin Hood's Bay, N. Yorkshire, England
P. G. Moore
Cassie, R.M. (1967). IVlathematicai models for the interpretation of inshore plankton communities. 'Estuaries, .-M-kAS'. 509-514. Cassie, R.M. and Michael, A . D . (196g). Fauna and sediments of an intertidal mudflat: a multivariate analysis. 'J. exp. mar. Biol. Ecol'., -°:1-25. Fager, E.W. (1957). Determination and analysis of recurrent groups. 'Ecology', 58:586-595. Fager, E.W. and Longhurst, A . R . (1968). Recurrent Group Analysis of species assemblages of demersal fish in the Gulf of Guinea. iJ. Fish. Res. Bd. Canada', 25: 1405-14Ol. Fager, E. W. and McGowan, J. A. (1"965). Zooplankton species groups in the north Pacific. 'Science', 140:453-460. Field, J . G . and McFariane, G. (1968). Numerical methods in marine ecology. 1. A quantitative 'sir,~ilarity' analysis of rocky shore samples in False Bay, South Africa. 'Zool. Air.', 3:119-137. Field, J. G. and Robb, F. 2". (1970). Numerical methods in marine ecology. 2. Gradient analysis of rocky shore samples from False Bay. 'Zool. Afr.', 5;191-210. Greig-Smith, P. (1969). Analysis of vegetation data: The user viewpoint. 'International Symposium on Statistical Ecology', New Haven, (in press).
I.C.E.S. (1969). Report of the working group on pollution of the North Sea. CM. 1968, A: 13. Margalef, g. (1968). 'Perspectives in Ecological Theory', (Univ. of Chicago Press, Chicago.) McNeill, S. and Lawton, J. H.(1970). Annual production and respiration in animal populations. 'Nature', 2.°5:472-474. Preston, F.W. (1969). Diversity and stability in the biological world, in 'Diversity and stability in Ecological Systems' Brookhaven Symposia in Biology no. 2-0:1-12. Williams, W. T. and Lambert, J. M. (1959). Multivariate methods in plant ecology. I. Association Analysis in plant communities. 'J. Ecol.', 47:85-101. Williams, W. T. and Lambert, J. M. (1970). Multivariate methods in plant ecology.. II. The use of an electronic digital computer for association analysis. 'J. Ecol.', 48: 689-710. Williams, W. T. and Lambert, J. M. (1961). Multivariate methods in plant ecology. III. Inverse Association Analysis. 'J. Ecol.', 49:71 7-729. Williamson, M.H. (1961). An ecological survey of a Scottish herring fishery, IV. Changes in the plankton during the period 1949 to 1959. 'Bull. Mar. Ecol.', 5:207-229.
Pollution Effects on Micro-and Heiofauna of Sand Although the concenti'ations of pesticides and heavy metals in potential sea-food is currently attracting widespread attention, the effects of pollution on lower trophic levels in the sea remain almost unknown. In the sediment ecosystem pollution could have far-reaching consequences at high trophic levels through for example alteration of the composition of important species at low trophic levels in food webs, or by irradication of organisms fundamental to the breakdown processes of the carbon, nitrogen and sulphur cycles. Toxic effects of pollutants have been assessed mainly at high trophic levels (Portman 1970), and only acute effects involving 48 or 96 h L.C.s0 tests have been considered. Of potentially greater long-term importance are the synergistic effects of low levels of pollutants on growth, respiration and fertility rates and the possible alteration of behavioural patterns caused by pollutants. The large size and relatively long life-span of commercially important marine species renders studies of the effects of pollutants on complete life-cycles difficult to accomplish. Thus, smaller animals have a~'antages in pollution research in having short life-cycles and being easy to manipulate experimentally. The effects of pollution on genetic stability is also of fundamental interest and rapidly reproducing species are of importance in this context. Marine sand beaches contain an abundance of micro- and meiofauna which provide ideal experimental material for pollution studies. In addition to being small (by definition) most species have short Life-cycles and undergo direct development, ~Sthout planktonic larvae and a variety of ~'ophic levels exists in accessible communities. A large section of the sand-beach micro- and meiofauna feeds at the primary, trophic level on bacteria and microalgae. As no information exists on the effects of pollutants at this trophic level, a bacterivorous ciliate protozoan and .a -oa.icroa]" v ~ . o u s arch_iannelid were_studie.d. The ciliate, Cristigera spp. was isolated from beach sand at Robin Hood's Bay, using the seawater-ice extraction method
(Uhlig, 1964). Cristigera was cultured on a diet of bacterium Pseudomonas spp.), also isolated from beach sand. The growth characteristics of the bacterium in relation to salinity, temperature and some chemical pollutants were established. From this knowledge an excess of food was maintained in experiments measuring the growth rate of Cristigera. Growth rates of Cristigera were measured as increase in number of cells per unit time, using a Coulter Model A paxticle counter, with periodic direct microscopic examination of sub-samples to check accuracy of counting. The exponential growth phase alone was studied. (A more detailed description o f methods is out of place in the present report and will be given in subsequent papers). A routine temperature of 15°C-*0.5°C and salinity of 34.5-*0.5°/00 were maintained in culture vessels. Each experiment was done in duplicate with an unpolluted control. The archlannelid Dinophilus gyrociliatus O. Schmidt was cultured on a diet of ground deep-frozen spinach (Akesson, 1970), at a temperature of 16 C - 1 C and a salinity of 34.5 -* 0.5 /oo, m sohd watch glasses (2 ml. capacity). The increase in length of ten recently hatched juveniles was measured every two days when the food source and seawater were changed. Growth rate measurements were continued until the Fl generation hatched. The pollutants tested for their effect on growth rate were c o m m o n North Sea pollutants (I.C.E.S. Cooperative Research Report Series A, 1969), namely hea~w metals, phenol, and sulphuric acid. Concentrations usecl were below that cause-d['~o-~'lete inhibition of growth rates, as synergistic effects of low levels of pollutant were the main interests. Experiments followed a 23 factorial design with replication, but will be extended to encompass a 33 factorial design where interaction terms are non-linear. The S 3 factorial design will enable linear, quadratic and cubic components of the response curves to be established, if present. The design will be extended to explore three dimensional response surfaces (Box and Wilson, 1951), o
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