Piepenburg, Dieter
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Piepenburg, Dieter
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Piepenburg, Dieter
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Item type:Publication, Developments in German Bight benthic ecology driven by climate change and anthropogenic utilization(2016-06-27); ; ; Marine ecosystems are subjected to an unprecedented range of natural and anthropogenic disturbance with an increasing frequency of occurrence over recent decades. Among others, rising sea water temperature, ocean acidification, and coastal water pollution have resulted in alteration of habitats and subsequent changes in the structures of species assemblages. In the face of these challenges, ecological research needs to predict responses of assemblages to global change, a requisite for the adequate prevention of further environmental degradation. However, predicting assemblage responses requires a thorough understanding of ecological processes and of the structure and functioning of assemblages. The present thesis comprises four manuscripts which address in detail a) the temporal variability of benthic macrozoobenthos assemblages and the relative role of different environmental drivers of abundance variations in the North Sea, b) the functional diversity and the dominant functional characteristics of benthic species of the southern North Sea, c) the temporal variations in the functional trait composition, the contribution of different biotic and abiotic predictors to the variation in ecological functioning, the relationship between species diversity and functional diversity and the extent of functional redundancy within benthic communities and d) the degree of functional homogenization and the identification of dynamically-dominant-traits that likely have the greatest effect on biodiversity and ecosystem function. In Manuscript I, the model results revealed that temperature and anomalies of the North Atlantic Oscillation Index (NAOI) play a distinct role in controlling the temporal variation of the benthic assemblages. The results also showed substantial variation in the composition of macrozoobenthos assemblages in the North Sea at decadal and sub-decadal scales. Species react differently to environmental disturbances with generalist species being dominant in the region. Manuscript II and Manuscript III on the functional characteristics of macrozoobenthos assemblages revealed that changes in trait composition were more similar among monitoring sites than changes in the taxonomic composition, emphasizing the role of environmental disturbances in the determination of trait associations in the North Sea system. The relationship between species richness and functional diversity indicates a relatively high functional redundancy within benthic assemblages of the southern North Sea. Manuscripts II - IV showed that some trait modalities such as small body size, high dispersal potential, interface- and deposit-feeding were relatively common in the North Sea benthic assemblages. In fact, this suite of traits represents an adaptive strategy enabling species to survive and thrive in a stressful environment. The replacement of specialist species by generalist species (Manuscripts I and III), less site-specific temporal variations in functional composition as compared to the taxonomic composition (Manuscript III) and a high degree of functional niche overlap (Manuscript IV), imply functional similarity among species assemblages. An increased spatial similarity of assemblages, in turn, generated functional homogenization in the North Sea benthic system. In contrast to the considerable temporal variation in species abundance, the temporal development of functional diversity was relatively stable with only two incidental inconsistencies coinciding with extreme events (i.e. cold winter 1995/96 and extreme negative NAO winter of 2009/10) in the North Sea. Following the temporary changes, the functional diversity rebounded to previous levels after almost one year. The rapid recovery of functionality after disturbance may be attributed to the high functional redundancy in the ecosystem. The results of the present thesis contribute to the understanding of the structural and functional processes of macrozoobenthos in the southern North Sea. The study highlights that a comprehensive understanding of long-term dynamics of benthic ecosystems requires a combined analysis of functionality and taxonomic structure.doctoral thesis654 181 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Trophic structures and flows in marine benthic communities of the Magellan Region, Southern Chile(2016-08-31); ; ; The sub-Antarctic Magellan region in southern Chile belongs to the most extensive fjord regions of the world. Coastal and marine environments are exposed to natural and anthropogenic perturbations. Research on the marine ecosystems have received some attention, however, research on the flow of energy is rather limited. To trace energy flow and resource distribution across communities is of considerable concern to current ecological studies for understanding how marine benthic ecosystems are organized, the base of which food sources they are built upon and how benthic organisms utilize resources. Heterogeneous environmental conditions along the Sub-Antarctic Magellan region, however, suggest the possibility of great heterogeneity in community structure and population dynamics. Studies of the trophic structure and energy flow are essential in this context. The aim of this thesis is to increase the knowledge of the ecological role of benthic species to communities living in the sub-Antarctic Magellan region. The main objectives of this research are (i) to investigate the trophic ecology of conspicuous species and their ecological role in the marine benthic communities of the Magellan region, (ii) to describe the trophic structure of two shallow-water benthic community types in the Strait of Magellan in order to establish baseline descriptions of trophic relationships for community structure and function, and (iii) to estimate benthic secondary production in this sub-Antarctic region as a proxy for energy flow along latitudinal gradients. The main results indicate that both local/regional environmental conditions and biological features cause clear differences in the trophic structure and energy flow patterns. This research gives valuable insight into ecological functioning of marine benthic communities present in the sub-Antarctic Magellan region and offers useful information to build food web models.doctoral thesis359 101