The benthic ecology of Loch Linnhe and loch eil, a sea-loch system on the west coast of Scotland. I. The physical environment and distribution of the macrobenthic fauna
TL;DR: It is concluded that distinct faunal communities do not exist in the Loch Linnhe and Loch Eil sea-loch system and important environmental factors affecting the distribution of species are thought to be sediment-type, bottom current speed and, to a lesser extent, total organic content of the sediment.
About: This article is published in Journal of Experimental Marine Biology and Ecology.The article was published on 1970-08-01. It has received 112 citations till now. The article focuses on the topics: Amphiura & Amphiura chiajei.
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TL;DR: The available evidence suggests that environmental factors such as productivity, temperature, and sediment grain-size diversity play dominant roles in determining patterns of regional-scale species richness and patterns in species turnover, and it is probably the regional scale that primarily determines local species richness.
Abstract: Marine soft sediments comprise one of the largest and oldest habitats in the world, yet remarkably little is known about patterns of species richness. Here I present a short review of patterns of species richness and possible factors that influence such patterns. Species richness in general is remarkably high in both shallow coastal areas and the deep sea. However, there are clear differences-the deep-sea has higher number of species for a given number of individuals than the coast. This can be explained by the larger amounts of primary production that reach coastal compared with deep-sea sediments, leading to higher numbers of individuals per unit area. Species density (the number of species per unit area) is also higher in the deep-sea than in coastal areas, but it is not obvious why this is so. Most studies of the broad patterns of species richness have used samples taken at small scales only. The problem with such analyses is that unless a large number of samples are taken, the true underlying pattern (or lack of it) may be wrongly interpreted. Recent studies have analysed species richness at larger scales. In general there seems to be a cline of increasing species richness from the Arctic to the tropics, but this is not the case in the southern hemisphere, where Antarctic species richness is high. However, it is not known whether high species richness in the Antarctic occurs at all spatial scales. To what extent these patterns are determined by evolutionary factors remains to be determined by the application of molecular methods. The available evidence suggests that environmental factors such as productivity, temperature, and sediment grain-size diversity play dominant roles in determining patterns of regional-scale species richness and patterns in species turnover, and it is probably the regional scale that primarily determines local species richness.
310 citations
TL;DR: Assessment is urgently needed of the spatial scales and dynamics of species richness from point samples to assemblages, habitats and landscapes, especially in coastal areas and in the tropics, where the threats to biodiversity are greatest.
Abstract: SUMMARY: The two central paradigms of marine diversity are that there is a latitudinal cline of increasing species richness from poles to tropics and that species richness increases with depth to a maximum around 2,000 m and thereafter decreases. However, these paradigms were based on data collected in the late 1950’s and early 1960’s. Here I show that the 1960’s data, are not representative and thus the paradigms need re-examination. New data from coastal areas in the northern hemisphere record species richness as high as the highest recorded in the deep-sea. Whilst this suggests that the cline of increasing diversity from shallow to deep-sea does not exist, however, the database for the deep sea is not sufficient to draw such a conclusion. The basic problem with the data from the 1960s is that samples were taken on ecological scales and yet they are used to answer evolutionary questions. The questions that such data were to answer were why do the tropics have higher species richness than polar regions or why do deep-sea sediments have more species than coastal sediments? Evolutionary questions need data from much larger spatial areas. Recently, data representative of large scales have been collected from coastal areas in the northern hemisphere and show that there is a cline of increasing species richness from the Arctic to the tropics, but there does not yet seem to be a similar cline in the southern hemisphere. A number of hypotheses have been proposed for the observed patterns in biodiversity. In terrestrial ecology the energy-productivity hypothesis has gained wide acceptance as an explanation for the latitudinal gradient. Here I examine this and other hypotheses critically. Finally an analysis of research priorities is made. Assessment is urgently needed of the spatial scales and dynamics of species richness from point samples to assemblages, habitats and landscapes, especially in coastal areas and in the tropics, where the threats to biodiversity are greatest. New technologies are available, such as side-scan sonar, acoustics, and under-water digital video cameras but as yet have been relatively little used. Conservation of marine biodiversity must be based on sound theory, yet marine diversity studies lag well behind those of terrestrial habitats.
225 citations
Cites background from "The benthic ecology of Loch Linnhe ..."
...4 11–51 Lochs Linnhe and Eil, Scotland (Pearson, 1970) 323 13,014 12 9-111 Firth of Lorne, Loch Etive, Loch Creran, Scotland (Gage, 1973) c....
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TL;DR: In this paper, the authors examined the estuarine soft bottom infauna of the Baltic Sea along some principal environmental gradients using a functional-group perspective, and identified 25 functional groups, forming clines from complex functional communities in the south and west, towards functionally poor assemblages in the north and east.
Abstract: The enclosed Baltic Sea, one of the world's largest brackish water basins, resembles a large estuary with steep horizontal and vertical environmental gradients. Thus, salinities range from 25 to 30 ppt in the Danish Sound area in the south to 1-3 ppt in the inner reaches of the Gulfs of Bothnia and Finland, and a persistent pycnocline in the Baltic basin causes stagnation of bottom waters for long periods, with periodic hypoxia/anoxia as a consequence, over an area covering up to 100 000 km 2 . Further, climatic variation from boreal to subarctic causes additional stress on the ecosystem, In recent decades, eutrophication and pollution have also significantly affected the biota of the Baltic Sea. The soft bottom infauna is poor in terms of species composition, and functional complexity is considered to be low. This paper examines the estuarine soft bottom infauna of the Baltic Sea along some principal environmental gradients using a functional-group perspective. We have used the functional-group concept (primarily feeding type, mobility and microhabitat), designed for polychaetes by Fauchald and Jumars (1979), to analyze and illustrate if and how the environmental gradients are reflected in the zoobenthos. A total of 25 functional groups were identified, forming clines from complex functional communities in the south and west, towards functionally poor assemblages in the north and east. The shift in functional groups indicates a loss of carnivores, tentaculate sessile organisms, and burrowers from areas beyond the Baltic and its marine approaches towards the inner bays. On the other hand, suspension feeders and surface deposit feeders increase in importance. In the northernmost areas of the Baltic only 1-3 functional groups are found, compared to 8-20 in the south.
202 citations
TL;DR: It is concluded that the log-series and lognormal models provide unsatisfactory explanations for species abundance because they are conceptually unsound and the models on which they are based rarely provide a satisfactory description of samples, which undermines the use of the diversity index $\alpha$ associated with these models.
Abstract: Three theories of explanation for the observed patterns of species abundance in samples from animal and plant communities are reviewed. These are the nichepreemption hypothesis associated with the log-series distribution, the theory based on the central-limit theorem to explain the truncated lognormal distribution, and the explanations associated with a recently published model of community dynamics. The relative performance of the log-series, lognormal, and dynamics models in predicting the species abundance in 222 samples from a wide range of communities is examined. The log-series provides the best prediction of only 4% of the samples, because there were either too few rare species or, more usually, the common species were too abundant. Only 28% of samples, those with a mode in the species-abundance distribution, may be described by a truncated lognormal, but even in these cases the lognormal parameters cannot reasonably be used to predict the abundance of species in the whole community. The species ab...
187 citations
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TL;DR: It is concluded that while there has been much disagreement about the constitution of the communities, the chief criticism has been directed against the view that they are units bound together by biological factors and that any system of classification should be based on the external conditions.
Abstract: SUMMARY
1
The more important contributions to the literature of animal communities on the sea bottom are summarized.
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It is concluded that while there has been much disagreement about the constitution of the communities, the chief criticism has been directed against the view that they are units bound together by biological factors. There is little evidence for this idea. However, most workers agree that communities exist and that there is a correlation between their distribution and that of certain physical factors. Therefore any system of classification should be based on the external conditions.
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The factors affecting the distribution of communities are discussed. The significant factors are probably temperature, salinity, and the nature of the bottom deposit.
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A scheme of classification applying to the communities of the littoral system is suggested, and an attempt is made to define the range of physical conditions within which each exists. Only the Atlantic boreal region is sufficiently well investigated for the classification to be applied in detail. The communities are described as shallow when the animals composing them are eurythermal and euryhaline within wide limits, offshore when they are eurythermal and euryhaline within narrower limits, and deep when they are stenothermal and stenohaline. Each group is subdivided according to the type of bottom on which the communities occur. There is more or less intergrading between neighbouring communities, both vertically and horizontally.
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The more important species occurring in each community are listed and the probable place in the classification of the communities previously described is shown.
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The reasons for the existence of animal communities on the sea bottom are discussed. The morphology and mode of life of certain species seem to be important in restricting them to certain grades of deposit, and while analysis of feeding methods does not at present indicate that the latter are of paramount importance in this respect, it is possible that more detailed studies on individual species will prove them to be so.
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The quantitative investigations into the fauna of the sea bottom are discussed, and it is concluded that there is little probability of valuable results arising from evaluations at the present time. On the other hand, much useful information may be expected from further studies of the differences in production apparent on different deposits and between different areas, and of the changes in numbers that take place from time to time among the population of a single area.
225 citations
TL;DR: In this article, a quantitative wet-combustion method for determining organic carbon in soils is described, which employs a simple apparatus and a rapid procedure of analysis using a Nesbitt bulb.
Abstract: A quantitative wet-combustion method for determining organic carbon in soils is described which employs a simple apparatus and a rapid procedure of analysis. All units of the purifying system are mounted on a compact panel which facilitates assembly and storage of the equipment. Evolved CO₂ in a carrier stream is passed successively through traps containing KI, Ag₂SO₄, concentrated H₂SO₄, zinc and anhydrone, after which the CO₂ is absorbed on Mikohbite in a Nesbitt bulb and determined by weighing. The method determines total (organic plus inorganic) carbon unless any carbonates present in calcareous soils are previously destroyed. A rapid pretreatment for removing carbonates is described which permits the direct determination of organic carbon. The method works satisfactorily on saline soils containing high concentrations of Cl salts and also on extracts that can be evaporated to dryness such as Na-dispersed organic matter extracts.
217 citations
164 citations