The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Cédric Leroux - One of the best experts on this subject based on the ideXlab platform.
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A seasonal stable isotope survey of the food web associated to a peri-urban Rocky Shore
Marine Biology, 2010Co-Authors: Gauthier Schaal, Pascal Riera, Cédric Leroux, Jacques GrallAbstract:We characterized the structure and functioning of the food web associated to an intertidal Rocky Shore in the harbour of Brest (Western Brittany, France), through a seasonal delta(13)C and delta(15)N survey. The dominance of benthic-derived organic matter, and particularly resuspended sediment, in the local pool of suspended organic matter, is highlighted. This benthic-derived organic matter dominates the diet of filter-feeders, including a certain degree of selectivity displayed by various taxa belonging to this trophic group. The food web structure appeared very stable temporally, which suggested the dominance of mixed diets, rather than the consumption of pure sources. It was constituted of 4 trophic levels, including a large diversity of predators, likely favoured by the diversity of microhabitats that characterize this intertidal habitat. From our results, the trophic functioning of this peri-urban Rocky Shore community does not appear functionally simplified as previously reported for other anthropized and/or artificial Rocky ecosystems. We suggest that the topological complexity of Rocky habitats, including a diversity of microhabitats, might be responsible of the important animal diversity, in spite of the anthropogenic disturbances characterizing this peri-urban area.
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Trophic ecology of the Rocky Shore community associated with the Ascophyllum nodosum zone (Roscoff, France): A delta C-13 vs delta N-15 investigation
Estuarine Coastal and Shelf Science, 2009Co-Authors: Pascal Riera, Carole Escaravage, Cédric LerouxAbstract:This study aimed to characterize the structure and functioning of the benthic food web associated with the Ascophyllum nodosum zone of the Rocky Shore of Roscoff by using delta C-13 and delta N-15. Several characteristics of the trophic ecology of the invertebrates associated with this mid-littoral habitat and which belong to different functional groups (e.g., grazers, filter-feeders, predators and omnivores) were highlighted. In particular, the filter feeder species (including mostly sponges) used macroalgae-derived organic matter as a substantial food requirement. The results also pointed out an important stable isotopes variability for strict coexisting primary consumers which: (1) is directly related to the high delta N-15 range of the food sources; (2) makes it impossible to establish a unique trophic level scale based on delta N-15 values, as previously done in coastal environments; and (3) points out the existence of major co-occurring trophic pathways which characterise the Ascophyllum nodosum habitat. (C) 2008 Elsevier Ltd. All rights reserved.
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trophic ecology of the Rocky Shore community associated with the ascophyllum nodosum zone roscoff france a δ13c vs δ15n investigation
Estuarine Coastal and Shelf Science, 2009Co-Authors: Pascal Riera, Carole Escaravage, Cédric LerouxAbstract:Abstract This study aimed to characterize the structure and functioning of the benthic food web associated with the Ascophyllum nodosum zone of the Rocky Shore of Roscoff by using δ13C and δ15N. Several characteristics of the trophic ecology of the invertebrates associated with this mid-littoral habitat and which belong to different functional groups (e.g., grazers, filter-feeders, predators and omnivores) were highlighted. In particular, the filter feeder species (including mostly sponges) used macroalgae-derived organic matter as a substantial food requirement. The results also pointed out an important stable isotopes variability for strict coexisting primary consumers which: (1) is directly related to the high δ15N range of the food sources; (2) makes it impossible to establish a unique trophic level scale based on δ15N values, as previously done in coastal environments; and (3) points out the existence of major co-occurring trophic pathways which characterise the Ascophyllum nodosum habitat.
Finn Surlyk - One of the best experts on this subject based on the ideXlab platform.
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Morphological adaptations of the brachiopods from a Late Cretaceous Rocky Shore, Ivö Klack, southern Sweden
Palaeogeography Palaeoclimatology Palaeoecology, 2019Co-Authors: Ane Elise Schrøder, Anne Mehlin Sørensen, Finn SurlykAbstract:Abstract In 1965 D.V. Ager highlighted the concept of morphological adaptations of Mesozoic brachiopods to different environments. Rocky Shores were only indirectly included in his seven habitats, undoubtedly due their rarity in the fossil record. A diverse brachiopod fauna, comprising 19 species, lived on the late early Campanian gneissic Rocky Shore at the palaeo-island of Ivo, southern Sweden. The brachiopods show many different morphological adaptations to the contrasting local habitats in the turbulent and highly variable environment. They are grouped into guilds and related to preferred habitats according to their morphology, substrate strategies, mode of life and preservation. Four main local habitats are recognized, representing different energy and illumination conditions, ranging from protected areas below and between gneiss boulders and hummocks to the most exposed areas on the vertical sides of these rocks. Medium-sized delicate species preferred the protected habitats, whereas large, robust species occupied the most exposed habitats. No small-sized brachiopod species are known from Ivo Klack in marked contrast to contemporaneous faunas of the more basinal chalks. The only observed direct indication of predation on the brachiopods is boreholes after carnivorous gastropods. The brachiopod fauna is by far the richest in terms of species diversity compared not only to other Late Cretaceous Rocky Shore faunas worldwide, but Rocky Shore faunas in the entire Phanerozoic. This difference is so remarkable that it cannot be explained by taphonomic factors alone and the density and diversity of the well-preserved brachiopods at Ivo Klack and the great variety in shell morphologies gives a unique opportunity to examine the variety in attachment strategies used in such a highly variable environment.
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Rocky Shore taphonomy—A comparative study of modern and Late Cretaceous analogues
Palaeogeography Palaeoclimatology Palaeoecology, 2015Co-Authors: Anne Mehlin Sørensen, Finn SurlykAbstract:Abstract Rocky Shores are rare in the fossil record due to erosion under both sea-level rise and fall. In contrast, modern Rocky Shores are well-studied, but little is known about the evolution of their ecosystems due to the rarity of ancient counterparts. Reconstruction of these ancient ecosystems is thus essential to get an insight into their evolution. A high-diversity Late Cretaceous (Campanian) Rocky Shore fauna is found in southern Sweden. The original composition of the shelly fauna cannot be interpreted by direct examination of the preserved fauna due to the effects of taphonomic processes. Life and death assemblages from a modern Rocky Shore fauna from Thailand have previously been analysed and a hypothetical fossil assemblage was reconstructed in order to attempt an interpretation of the Campanian life assemblage. This study shows a low taxonomic agreement between the original Campanian life assemblage and the fossil assemblage, due to taphonomic processes, and high environmental fidelity with only a few out-of-habitat species represented. The modern life assemblage showed in an earlier study, a high loss of species before onset of fossilisation. This suggests that the faunal composition of the Campanian life assemblage cannot be easily reconstructed, and time averaging by generations of death assemblages makes this even more difficult. The Campanian aragonitic fauna is poorly represented and the rarity of moulds after aragonitic species is interpreted as due to taphonomic processes and not to lower richness of aragonitic species in the Cretaceous. This is supported by comparison with the high richness of aragonitic species found on a Late Cretaceous Rocky Shore in Germany. An originally high-diversity gastropod fauna is thus interpreted to have dominated the intertidal zone in the Campanian example, and the rare moulds of each of the aragonitic species indicate a high taphonomic loss in spite of rapid burial. Calcitic species-richness is higher in the Campanian fauna than in the modern life, death, and constructed hypothetical fossil assemblages. This is interpreted as reflecting time averaging of generations of calcitic species and low loss of calcitic species by taphonomic processes in the Campanian fauna. It is thus assumed that the original Campanian fauna experienced a change in faunal composition from a gastropod-dominated life assemblage to a bivalve-dominated fossil assemblage due to dissolution of aragonite and excellent preservation of calcite. Reconstruction of ancient Rocky Shore shelly faunas can thus be considerably improved by comparison with analogous modern Rocky Shore faunas.
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Mollusc life and death assemblages on a tropical Rocky Shore as proxies for the taphonomic loss in a fossil counterpart
Palaeogeography Palaeoclimatology Palaeoecology, 2013Co-Authors: Anne Mehlin Sørensen, Finn SurlykAbstract:Abstract Comparison of a modern Rocky Shore mollusc life assemblage from Thailand with the associated death assemblage, and interpretation of the fossilization potential of the latter, are used to investigate the fidelity in reconstruction of ancient analogues. The fauna from the death assemblage represents species from the Rocky Shore and the associated sandy pocket beaches, and only a few exotic species from other, completely different habitats are present. The environmental fidelity between the life and death assemblage is thus high, with the majority of species from the death assemblage representing the intertidal to shallow subtidal Rocky Shore environment, from which the life assemblage was sampled, and the associated sandy beach environment. The life assemblage should in principle have a high fossilization potential because only two out of 67 species are without a calcareous shell, but it actually has a lower taxonomic agreement to the death assemblage than found in previous published studies. Rocky Shore life and death assemblages thus appear to show lower taxonomic agreement compared to muddy or sandy shelf assemblages due to the mix after death with the sandy beach assemblage. A hypothetical fossil assemblage is constructed from the death assemblage, assuming that only calcitic and infaunal aragonitic species have a chance to be preserved in the geological record. The hypothetical fossil assemblage is not taxonomically similar to the life assemblage but shows high environmental fidelity to the Rocky Shore and sandy pocket beach. In terms of species richness the life assemblage is dominated by epifaunal, herbivorous gastropods, whereas the hypothetical fossil assemblage is dominated by infaunal, suspension feeding bivalves. The hypothetical fossil assemblage thus represents a faunal community from an intertidal to shallow subtidal Rocky Shore environment and the associated sandy pocket beach environment, and shows marked differences in faunal composition, modes of life, richness and density patterns compared to the Rocky Shore life assemblage due to the mix between the two associated habitats. This serves to illustrate the significance of integrating the taphonomic influence on a fossil faunal assemblage before attempting to reconstruct an ancient ecosystem and environment.
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adaptive morphologies and guild structure in a high diversity bivalve fauna from an early campanian Rocky Shore ivo klack sweden
Cretaceous Research, 2012Co-Authors: Anne Mehlin Sørensen, Finn Surlyk, John W M JagtAbstract:Abstract The bivalve fauna from a late early Campanian Rocky Shore at Ivo Klack (southern Sweden), comprises just over sixty species, a very high diversity in comparison to other Late Cretaceous and modern Rocky Shore bivalve assemblages. This high diversity is here considered to represent a reliable census of the fauna; only in part can it be explained by the cumulative effect of generations of bivalves inhabiting this coastal environment. The high density and diversity and the wide range of shell morphologies allow interpretation of different modes of life in this variable environment with many contrasting habitats. Study of the functional morphology of bivalve shells and comparison with extant relatives has resulted in a subdivision of the fauna into seven guilds and five habitats. The bivalve fauna represents a within-habitat, time-averaged assemblage to which none of the species was introduced from adjacent environments. It includes some of the most northerly known, very small rudistid bivalves, in addition to the oldest known occurrences of Mytilus and Barbatia in association with Rocky Shores. Bivalves constituted the most important invertebrate group inhabiting the late early Campanian Rocky Shore at Ivo Klack, in terms of diversity, density and biomass.
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Taphonomy and palaeoecology of the gastropod fauna from a Late Cretaceous Rocky Shore, Sweden
Cretaceous Research, 2011Co-Authors: Anne Mehlin Sørensen, Finn SurlykAbstract:A gastropod fauna comprising 17 species, each represented by a limited number of specimens, is described from a Late Cretaceous, late early Campanian Rocky Shore at Ivo Klack, southern Sweden. The gastropod fauna is associated with the most diverse ancient Rocky Shore fauna ever found. However, the low gastropod species diversity compared to the faunas of modern Rocky Shores is ascribed to taphonomic factors, notably dissolution of the aragonitic shells, but the predominance of epifaunal herbivores is indicative of a guild structure similar to that found on modern Rocky Shores. The presence of drill holes assigned to the ichnospecies Oichnus simplex suggests the former presence of muricid gastropods which have not been found as body fossils. A single drill hole is referred to Oichnus paraboloides and was probably made by a naticid gastropod. The infaunal mode of life of naticids makes preservation of such drill holes difficult, since the majority of infaunal prey such as burrowing bivalves has aragonitic shells which are not preserved. The relatively high number of species in comparison to many other Late Cretaceous Rocky Shore faunas, offers an opportunity to compare gastropod guild structure at Ivo Klack with modern counterparts, even though taphonomic processes such as mechanical destruction and aragonite dissolution have played an important role in the fossil gastropod assemblage.
Pascal Riera - One of the best experts on this subject based on the ideXlab platform.
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A seasonal stable isotope survey of the food web associated to a peri-urban Rocky Shore
Marine Biology, 2010Co-Authors: Gauthier Schaal, Pascal Riera, Cédric Leroux, Jacques GrallAbstract:We characterized the structure and functioning of the food web associated to an intertidal Rocky Shore in the harbour of Brest (Western Brittany, France), through a seasonal delta(13)C and delta(15)N survey. The dominance of benthic-derived organic matter, and particularly resuspended sediment, in the local pool of suspended organic matter, is highlighted. This benthic-derived organic matter dominates the diet of filter-feeders, including a certain degree of selectivity displayed by various taxa belonging to this trophic group. The food web structure appeared very stable temporally, which suggested the dominance of mixed diets, rather than the consumption of pure sources. It was constituted of 4 trophic levels, including a large diversity of predators, likely favoured by the diversity of microhabitats that characterize this intertidal habitat. From our results, the trophic functioning of this peri-urban Rocky Shore community does not appear functionally simplified as previously reported for other anthropized and/or artificial Rocky ecosystems. We suggest that the topological complexity of Rocky habitats, including a diversity of microhabitats, might be responsible of the important animal diversity, in spite of the anthropogenic disturbances characterizing this peri-urban area.
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Trophic ecology of the Rocky Shore community associated with the Ascophyllum nodosum zone (Roscoff, France): A delta C-13 vs delta N-15 investigation
Estuarine Coastal and Shelf Science, 2009Co-Authors: Pascal Riera, Carole Escaravage, Cédric LerouxAbstract:This study aimed to characterize the structure and functioning of the benthic food web associated with the Ascophyllum nodosum zone of the Rocky Shore of Roscoff by using delta C-13 and delta N-15. Several characteristics of the trophic ecology of the invertebrates associated with this mid-littoral habitat and which belong to different functional groups (e.g., grazers, filter-feeders, predators and omnivores) were highlighted. In particular, the filter feeder species (including mostly sponges) used macroalgae-derived organic matter as a substantial food requirement. The results also pointed out an important stable isotopes variability for strict coexisting primary consumers which: (1) is directly related to the high delta N-15 range of the food sources; (2) makes it impossible to establish a unique trophic level scale based on delta N-15 values, as previously done in coastal environments; and (3) points out the existence of major co-occurring trophic pathways which characterise the Ascophyllum nodosum habitat. (C) 2008 Elsevier Ltd. All rights reserved.
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trophic ecology of the Rocky Shore community associated with the ascophyllum nodosum zone roscoff france a δ13c vs δ15n investigation
Estuarine Coastal and Shelf Science, 2009Co-Authors: Pascal Riera, Carole Escaravage, Cédric LerouxAbstract:Abstract This study aimed to characterize the structure and functioning of the benthic food web associated with the Ascophyllum nodosum zone of the Rocky Shore of Roscoff by using δ13C and δ15N. Several characteristics of the trophic ecology of the invertebrates associated with this mid-littoral habitat and which belong to different functional groups (e.g., grazers, filter-feeders, predators and omnivores) were highlighted. In particular, the filter feeder species (including mostly sponges) used macroalgae-derived organic matter as a substantial food requirement. The results also pointed out an important stable isotopes variability for strict coexisting primary consumers which: (1) is directly related to the high δ15N range of the food sources; (2) makes it impossible to establish a unique trophic level scale based on δ15N values, as previously done in coastal environments; and (3) points out the existence of major co-occurring trophic pathways which characterise the Ascophyllum nodosum habitat.
Anne Mehlin Sørensen - One of the best experts on this subject based on the ideXlab platform.
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Morphological adaptations of the brachiopods from a Late Cretaceous Rocky Shore, Ivö Klack, southern Sweden
Palaeogeography Palaeoclimatology Palaeoecology, 2019Co-Authors: Ane Elise Schrøder, Anne Mehlin Sørensen, Finn SurlykAbstract:Abstract In 1965 D.V. Ager highlighted the concept of morphological adaptations of Mesozoic brachiopods to different environments. Rocky Shores were only indirectly included in his seven habitats, undoubtedly due their rarity in the fossil record. A diverse brachiopod fauna, comprising 19 species, lived on the late early Campanian gneissic Rocky Shore at the palaeo-island of Ivo, southern Sweden. The brachiopods show many different morphological adaptations to the contrasting local habitats in the turbulent and highly variable environment. They are grouped into guilds and related to preferred habitats according to their morphology, substrate strategies, mode of life and preservation. Four main local habitats are recognized, representing different energy and illumination conditions, ranging from protected areas below and between gneiss boulders and hummocks to the most exposed areas on the vertical sides of these rocks. Medium-sized delicate species preferred the protected habitats, whereas large, robust species occupied the most exposed habitats. No small-sized brachiopod species are known from Ivo Klack in marked contrast to contemporaneous faunas of the more basinal chalks. The only observed direct indication of predation on the brachiopods is boreholes after carnivorous gastropods. The brachiopod fauna is by far the richest in terms of species diversity compared not only to other Late Cretaceous Rocky Shore faunas worldwide, but Rocky Shore faunas in the entire Phanerozoic. This difference is so remarkable that it cannot be explained by taphonomic factors alone and the density and diversity of the well-preserved brachiopods at Ivo Klack and the great variety in shell morphologies gives a unique opportunity to examine the variety in attachment strategies used in such a highly variable environment.
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Rocky Shore taphonomy—A comparative study of modern and Late Cretaceous analogues
Palaeogeography Palaeoclimatology Palaeoecology, 2015Co-Authors: Anne Mehlin Sørensen, Finn SurlykAbstract:Abstract Rocky Shores are rare in the fossil record due to erosion under both sea-level rise and fall. In contrast, modern Rocky Shores are well-studied, but little is known about the evolution of their ecosystems due to the rarity of ancient counterparts. Reconstruction of these ancient ecosystems is thus essential to get an insight into their evolution. A high-diversity Late Cretaceous (Campanian) Rocky Shore fauna is found in southern Sweden. The original composition of the shelly fauna cannot be interpreted by direct examination of the preserved fauna due to the effects of taphonomic processes. Life and death assemblages from a modern Rocky Shore fauna from Thailand have previously been analysed and a hypothetical fossil assemblage was reconstructed in order to attempt an interpretation of the Campanian life assemblage. This study shows a low taxonomic agreement between the original Campanian life assemblage and the fossil assemblage, due to taphonomic processes, and high environmental fidelity with only a few out-of-habitat species represented. The modern life assemblage showed in an earlier study, a high loss of species before onset of fossilisation. This suggests that the faunal composition of the Campanian life assemblage cannot be easily reconstructed, and time averaging by generations of death assemblages makes this even more difficult. The Campanian aragonitic fauna is poorly represented and the rarity of moulds after aragonitic species is interpreted as due to taphonomic processes and not to lower richness of aragonitic species in the Cretaceous. This is supported by comparison with the high richness of aragonitic species found on a Late Cretaceous Rocky Shore in Germany. An originally high-diversity gastropod fauna is thus interpreted to have dominated the intertidal zone in the Campanian example, and the rare moulds of each of the aragonitic species indicate a high taphonomic loss in spite of rapid burial. Calcitic species-richness is higher in the Campanian fauna than in the modern life, death, and constructed hypothetical fossil assemblages. This is interpreted as reflecting time averaging of generations of calcitic species and low loss of calcitic species by taphonomic processes in the Campanian fauna. It is thus assumed that the original Campanian fauna experienced a change in faunal composition from a gastropod-dominated life assemblage to a bivalve-dominated fossil assemblage due to dissolution of aragonite and excellent preservation of calcite. Reconstruction of ancient Rocky Shore shelly faunas can thus be considerably improved by comparison with analogous modern Rocky Shore faunas.
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Mollusc life and death assemblages on a tropical Rocky Shore as proxies for the taphonomic loss in a fossil counterpart
Palaeogeography Palaeoclimatology Palaeoecology, 2013Co-Authors: Anne Mehlin Sørensen, Finn SurlykAbstract:Abstract Comparison of a modern Rocky Shore mollusc life assemblage from Thailand with the associated death assemblage, and interpretation of the fossilization potential of the latter, are used to investigate the fidelity in reconstruction of ancient analogues. The fauna from the death assemblage represents species from the Rocky Shore and the associated sandy pocket beaches, and only a few exotic species from other, completely different habitats are present. The environmental fidelity between the life and death assemblage is thus high, with the majority of species from the death assemblage representing the intertidal to shallow subtidal Rocky Shore environment, from which the life assemblage was sampled, and the associated sandy beach environment. The life assemblage should in principle have a high fossilization potential because only two out of 67 species are without a calcareous shell, but it actually has a lower taxonomic agreement to the death assemblage than found in previous published studies. Rocky Shore life and death assemblages thus appear to show lower taxonomic agreement compared to muddy or sandy shelf assemblages due to the mix after death with the sandy beach assemblage. A hypothetical fossil assemblage is constructed from the death assemblage, assuming that only calcitic and infaunal aragonitic species have a chance to be preserved in the geological record. The hypothetical fossil assemblage is not taxonomically similar to the life assemblage but shows high environmental fidelity to the Rocky Shore and sandy pocket beach. In terms of species richness the life assemblage is dominated by epifaunal, herbivorous gastropods, whereas the hypothetical fossil assemblage is dominated by infaunal, suspension feeding bivalves. The hypothetical fossil assemblage thus represents a faunal community from an intertidal to shallow subtidal Rocky Shore environment and the associated sandy pocket beach environment, and shows marked differences in faunal composition, modes of life, richness and density patterns compared to the Rocky Shore life assemblage due to the mix between the two associated habitats. This serves to illustrate the significance of integrating the taphonomic influence on a fossil faunal assemblage before attempting to reconstruct an ancient ecosystem and environment.
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adaptive morphologies and guild structure in a high diversity bivalve fauna from an early campanian Rocky Shore ivo klack sweden
Cretaceous Research, 2012Co-Authors: Anne Mehlin Sørensen, Finn Surlyk, John W M JagtAbstract:Abstract The bivalve fauna from a late early Campanian Rocky Shore at Ivo Klack (southern Sweden), comprises just over sixty species, a very high diversity in comparison to other Late Cretaceous and modern Rocky Shore bivalve assemblages. This high diversity is here considered to represent a reliable census of the fauna; only in part can it be explained by the cumulative effect of generations of bivalves inhabiting this coastal environment. The high density and diversity and the wide range of shell morphologies allow interpretation of different modes of life in this variable environment with many contrasting habitats. Study of the functional morphology of bivalve shells and comparison with extant relatives has resulted in a subdivision of the fauna into seven guilds and five habitats. The bivalve fauna represents a within-habitat, time-averaged assemblage to which none of the species was introduced from adjacent environments. It includes some of the most northerly known, very small rudistid bivalves, in addition to the oldest known occurrences of Mytilus and Barbatia in association with Rocky Shores. Bivalves constituted the most important invertebrate group inhabiting the late early Campanian Rocky Shore at Ivo Klack, in terms of diversity, density and biomass.
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Taphonomy and palaeoecology of the gastropod fauna from a Late Cretaceous Rocky Shore, Sweden
Cretaceous Research, 2011Co-Authors: Anne Mehlin Sørensen, Finn SurlykAbstract:A gastropod fauna comprising 17 species, each represented by a limited number of specimens, is described from a Late Cretaceous, late early Campanian Rocky Shore at Ivo Klack, southern Sweden. The gastropod fauna is associated with the most diverse ancient Rocky Shore fauna ever found. However, the low gastropod species diversity compared to the faunas of modern Rocky Shores is ascribed to taphonomic factors, notably dissolution of the aragonitic shells, but the predominance of epifaunal herbivores is indicative of a guild structure similar to that found on modern Rocky Shores. The presence of drill holes assigned to the ichnospecies Oichnus simplex suggests the former presence of muricid gastropods which have not been found as body fossils. A single drill hole is referred to Oichnus paraboloides and was probably made by a naticid gastropod. The infaunal mode of life of naticids makes preservation of such drill holes difficult, since the majority of infaunal prey such as burrowing bivalves has aragonitic shells which are not preserved. The relatively high number of species in comparison to many other Late Cretaceous Rocky Shore faunas, offers an opportunity to compare gastropod guild structure at Ivo Klack with modern counterparts, even though taphonomic processes such as mechanical destruction and aragonite dissolution have played an important role in the fossil gastropod assemblage.
Patrik Kraufvelin - One of the best experts on this subject based on the ideXlab platform.
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Biomass, diversity and production of Rocky Shore macroalgae at two nutrient enrichment and wave action levels
Marine Biology, 2010Co-Authors: Patrik Kraufvelin, Ann Lindholm, Morten Foldager Pedersen, Lars Andreas Kirkerud, Erik BonsdorffAbstract:The littoral zone of temperate Rocky Shores is normally dominated by perennial macroalgae (e.g. Fucus, Ascophyllum, Laminaria ), but nutrient enrichment and/or permanently decreased wave action may lead to structural community changes from dominance of perennials to increased amounts of annual opportunistic species (mainly green algae). Macroalgal biomass, diversity and production as well as relationships between the two latter were studied using Solbergstrand’s Rocky Shore mesocosms in SE Norway in connection with a long-term experimental manipulation of nutrient addition and wave action (high and low levels of both factors applied in a crossed way to eight outdoor basins). After more than 2 years of experimental treatment, the total standing stock of macroalgae was larger in low nutrient than in high nutrient treatments as well as in high wave compared to low wave treatments (in autumn only). For macroalgal functional groups, bushy and filamentous brown and filamentous red algae were generally favoured by low nutrient concentrations, while annual filamentous and sheet-like green algae were stimulated by the nutrient enrichment. There was only one significant interaction between nutrient enrichment and wave action (for brown filamentous algae in autumn) and also only one significant main effect of the wave treatment (for bushy brown algae in autumn). Surprisingly, the high nutrient treatments supported a higher diversity of macroalgae, whereas the low nutrient treatments generally showed higher production rates. Moreover, significantly negative correlations were found between macroalgal diversity and primary productivity in both summer and autumn. This study shows that it is the biological components of the communities subjected to external forcing (nutrient addition or decreased wave action) that regulate production and this contradicts the common misperception that resource production in natural systems simply can be fast-forwarded by fertilization. The negative relationships between diversity and productivity, although a consequence of unexpected results for diversity and production, are also novel and hint towards species identities having more important functional consequences than general species dominance patterns and the amount of species per se. These results also emphasise the context dependency of findings within the field of biodiversity and ecosystem functioning.
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Responses to nutrient enrichment, wave action and disturbance in Rocky Shore communities
Aquatic Botany, 2007Co-Authors: Patrik KraufvelinAbstract:Abstract A high degree of resistance against nutrient enrichment has previously been demonstrated for macroalgal-dominated Rocky Shore communities in the presence of moderate to large amounts of macroinvertebrate grazers. To experimentally examine, under controlled conditions, the possible roles for this resistance of two other factors, i.e. disturbance (presence/absence of the macroalgal canopy itself) and wave action, the canopy algae and associated algal and animal assemblages were removed by scraping from approximately one third of the area of eight littoral mesocosms, subjected to two different wave action regimes. After this, excessive nutrients were added to four mesocosms with the factor nutrients fully crossed with the factor wave action with two replicate mesocosm basins of each nutrient/wave treatment combination. Disturbance was added to the design as a within-basin factor thus making up a split-plot experiment. The abundance of grazers was allowed to vary freely and under the influence of the treatments. After 11 summer weeks, there were significant differences in community structure between nutrient enrichment levels for both algal and animal assemblages when examined by multivariate statistical techniques. Univariate analyses confirmed a significantly stimulated colonisation by green algae, mainly Ulva lactuca , in both disturbed (scraped) and undisturbed areas of nutrient-enriched mesocosms. In un-enriched mesocosms, the green algae were absent from undisturbed areas and rare in disturbed areas, where mainly brown Ectocarpus spp. and red algae had settled. Among the macrofauna, the total abundance of grazers was stimulated in nutrient-enriched mesocosms with individuals of the amphipod genus Gammarus and the isopod genus Jaera being especially numerous. With regard to wave action, no significant differences occurred in community structure, although there were indications of significant nutrient × wave effects for both the amount of exported red algae and the amount of accumulated brown algae. The study shows that eutrophication-related community shifts on Rocky Shores may occur very rapidly, regardless of the level of wave-energetic stress and the abundance of grazers, if the nutrient concentrations are high and the colonisation and growth of opportunistic algae are facilitated by disturbance such as (naturally or anthropogenically driven) canopy gap forming processes.
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nutrient addition to experimental Rocky Shore communities revisited delayed responses rapid recovery
Ecosystems, 2006Co-Authors: Patrik Kraufvelin, Frithjof E. Moy, Hartvig Christie, Tor L. BoknAbstract:Coastal eutrophication may alter the dominance patterns of marine macroalgae, with potential consequences for the associated fauna and the entire ecosystem. Benthic macroalgae and animals in control and nutrient-enriched mesocosms were monitored to investigate eutrophication-induced changes in Rocky Shore communities. During a 3-year project, nutrient addition had only minor effects on the community structure, such as increased cover and biomass of green Ulva spp. and increased abundance of certain animal species at high nutrient levels. This study is a 4-year extension of a previously reported project, with 2 extra years of effect studies (altogether 5 years) and a subsequent 2 years for recovery. During the 4th year of nutrient enrichment, the cover of Fucus vesiculosus and Fucus serratus started to decline. In the 5th year, these canopy species crashed and there was an evident take-over by green algae at high nutrient addition levels. The previously observed abundance stimulation for fauna disappeared later in the time series, probably due to the loss of the macroalgal canopy. After less than 2 years on regular seawater, the algal and animal communities had returned to within the range of normal variability. The results indicate that established Rocky Shore communities of perennial algae with associated fauna are able to persist for several years, even at very high nutrient levels, but that community shifts may suddenly occur if eutrophication continues. They also indicate that Rocky Shore communities have the ability to return rapidly to natural undisturbed conditions after the termination of nutrient enhancement.
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littoral macrofauna secondary responses to experimental nutrient addition to Rocky Shore mesocosms and a coastal lagoon
Hydrobiologia, 2002Co-Authors: Patrik Kraufvelin, Hartvig Christie, Marianne OlsenAbstract:Macrofauna secondary responses to controlled eutrophication within two MARICULT/MAST-III projects, EULIT and COMWEB, are compared. EULIT utilises a nutrient gradient established in eight hard bottom mesocosms, whereas the data from COMWEB originate from a whole-ecosystem study – the case of experimental nutrient addition to Hopavagen lagoon. In both systems, nutrient addition started in May 1998, after initial studies of the background macrofauna communities, thus allowing application of Before-After-Control-Impact-Pairs techniques (BACIP). The main objectives have been to investigate the macrofauna responses to eutrophication in littoral Rocky Shore ecosystems and to evaluate if similar responses could occur in mesocosm and `field' systems, despite their inherent differences. Apart from a distinct increase in numbers of Littorina littorea L. and some indications of increased abundance of the genus Jaera, no significant changes, caused by 2.5 years of nutrient addition, could be detected in the mesocosm fauna. It is interesting, however, that these two possibly stimulated animal groups have two things in common: (1) both belong to the rather few mobile taxa, which are not flushed out of the system through the mesocosm outlets, (2) both feed on microalgae and green algae in the upper littoral zone, i.e., algal groups that have shown the clearest response to the nutrient addition. In Hopavagen, 1.5 years of nutrient addition only caused modest plant and animal responses in the Rocky Shore ecosystem, although there was a markedly increased settlement of Mytilus edulis L. at one lagoon site. This increase was probably due to elevated levels of digestible particles (increased phytoplankton production) caused by the nutrient addition. There were also some indications of increased production of filamentous algae at this same lagoon site. All in all, both studies demonstrate only minor responses to increased nutrient levels within the littoral community (both plants and animals). One explanation to this may be that longer time-scales are needed in order for clear-cut changes to occur. Several observations also indicate that wave exposure (significant in both systems) may largely modulate the impact of increased nutrient load on the structure of littoral communities. Another explanation is the high degree of stability among littoral macroalgae-dominated communities with internal biological regulation factors (like grazing) possibly being able to counteract effects.
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are Rocky Shore ecosystems affected by nutrient enriched seawater some preliminary results from a mesocosm experiment
Hydrobiologia, 2002Co-Authors: Tor L. Bokn, Patrik Kraufvelin, Núria Marbà, Frithjof E. Moy, Hartvig Christie, Silke Engelbert, C Lindblad, Kees Kersting, Rolf Karez, Morten Foldager PedersenAbstract:The response of Rocky Shore ecosystems to increased nutrient availability was examined in eight land-based mesocosms designed for hard-bottom littoral communities built at Marine Research Station Solbergstrand (Norway). The average seawater volume in each basin was 9 m3 with an average water residence time of about 2 h. A tidal regime resembling that in the fjord was maintained in the basins, and waves were generated regularly. NH4NO3 and H3PO4, at a constant molar NP ratio of 16:1, was added into 6 basins at concentrations 1, 2, 4, 8, 16, 32 μM DIN above the background DIN concentration during 1 1/2 years. Two mesocosms were kept as control treatment. Marine communities were introduced into the basins two years prior to the start of nutrient dosage. The effects of nutrient enrichment were few and only marginal during the first year of nutrient addition, while some effects became more obvious during the second year. The growth rate of the periphyton and fast-growing macroalgae communities was stimulated by nutrient enrichment, while the response was less evident among the perennial fucoids. The structure of the macroalgal communities, however, did not change during 16 months' measurements. In contrast, growth on artificial rock substrates during the same period of time revealed intensive growth of the fast-growing Ulva lactuca in high-dosed basins compared with low-dosed and control basins, which were dominated by the fucoid Fucus serratus. The fauna communities exhibited only a minor response to nutrient treatment. The common periwinkle Littorina littorea, however, appeared with increased abundance in the high-dosed basins. The total system metabolism tended to increase slightly, but not significantly, with increased nutrient loading.
