35 research outputs found
The influence of ocean warming on the provision of biogenic habitat by kelp species
No full textKelp forests represent some of the most productive and diverse habitats on Earth, and play a critical role in structuring nearshore temperate and subpolar environments. They have an important role in nutrient cycling, energy capture and transfer, and offer biogenic coastal defence. Kelps also provide extensive substrata for colonising organisms, ameliorate conditions for understorey assemblages, and generate three-dimensional habitat structure for a vast array of marine plants and animals, including a number of ecologically and commercially important species. This thesis aimed to describe the role of temperature on the functioning of kelp forests as biogenic habitat formers, predominantly via the substitution of cold water kelp species by warm water kelp species, or through the reduction in density of dominant habitat forming kelp due to predicted increases in seawater temperature. The work comprised three main components; (1) a broad scale study into the environmental drivers (including sea water temperature) of variability in holdfast assemblages of the dominant habitat forming kelp in the UK, Laminaria hyperborea, (2) a comparison of the warm water kelp Laminaria ochroleuca and the cold water kelp L. hyperborea as habitat forming species, and further investigation into the impacts of this subtle climate driven substitution of habitat forming kelps, and (3) experimental manipulation of densities of the dominant intertidal kelp in the UK, Laminaria digitata, in order to understand the impacts of climate driven loss of a dominant habitat forming species.L. hyperborea assemblages varied significantly between study regions spanning ~9° of latitude, as well as between and within sites at a local scale. Patterns in mobile and sessile assemblage structure were driven principally by different environmental factors. Overall patterns in the structure of biogenic habitat and assemblage structure did not vary predictably with latitude, indicating that other processes acting across multiple spatial scales are important drivers of assemblage structure.L. ochroleuca hosted impoverished assemblages associated with both holdfasts and stipes, compared with L. hyperborea. Further, climate driven increases in the relative abundance of L. ochroleuca relative to L. hyperborea lead to disruption of an important habitat cascade associated with the stipe of L. hyperborea and epiphytic algae. L. ochroleuca stipes typically lack the dense epiphytic assemblage associated with L. hyperborea, and host depauperate faunal assemblages which may have impacts on higher trophic levels.Experimental reduction in the density of L. digitata led to a dramatic shift in dominance from perennial to annual species, particularly the pseudo-kelp Saccorhiza polyschides on an exposed rocky shore. Impacts on a sheltered shore were subtler, and may have been tempered by the presence of another perennial kelp, Saccharina latissima. Loss of L. digitata led to a reduction in the standing stock of macroalgae after ~2.5 years of manipulation on both shores. These findings have significant implications for the structure and functioning of rocky shores in the future.Overall, anthropogenic climate change is likely to negatively impact the functioning of kelp forests as repositories of biodiversity in the future via the reshuffling of warm- and cold-water kelp species and through an overall loss of algal biomass and associated habitat due to continued increases in seawater temperature in the northeast Atlantic
Climate-driven substitution of habitat-forming species leads to reduced biodiversity within a temperate marine community
No full textAim: In marine ecosystems, habitat-forming species (HFS) such as reef-building corals and canopy-forming macroalgae alter local environmental conditions and can promote biodiversity by providing biogenic living space for a vast array of associated organisms. We examined community-level impacts of observed climate-driven shifts in the relative abundances of two superficially similar HFS, the warm-water kelp Laminaria ochroleuca and the cool-water kelp Laminaria hyperborea. Location: Western English Channel, north-east Atlantic Methods: We compared algal and invertebrate assemblages associated with kelp stipes and holdfasts, across multiple sites and sampling events. Significant differences were recorded in the structure of assemblages between the host kelp species at each site and event. Results: Assemblages associated with stipes of the cool-water HFS were, on average, >12 times more diverse and supported >3600 times more biomass compared with the warm-water HFS. Holdfast assemblages also differed significantly between species, although to a lesser extent than those associated with stipes. Overall, assemblages associated with the warm-water HFS were markedly impoverished and comprised far fewer rare or unique taxa. Main conclusions: While previous research has shown how climate-driven loss of HFS can cause biodiversity loss, our study demonstrates that climate-driven substitutions of HFS can also lead to impoverished assemblages. The indirect effects of climate change remain poorly resolved, but shifts in the distributions and abundances of HFS may invoke widespread ecological change, especially in marine ecosystems where facilitative interactions are particularly strong.</p
Spatial variability in the diversity and structure of faunal assemblages associated with kelp holdfasts (<i>Laminaria hyperborea</i>) in the northeast Atlantic - Fig 2
No full textMap indicating the locations of the four study regions in the UK, northeast Atlantic: (A) northern Scotland, (B) western Scotland, (C) southwest Wales and (D) southwest England. Smaller panels show the positions of the 3 study sites within each region.</p
The role of kelp species as biogenic habitat formers in coastal marine ecosystems
No full textKelps are ecologically important primary producers and ecosystem engineers, and play a central role in structuring nearshore temperate habitats. They play an important role in nutrient cycling, energy capture and transfer, and provide biogenic coastal defence. Kelps also provide extensive substrata for colonising organisms, ameliorate conditions for understorey assemblages, and provide three-dimensional habitat structure for a vast array of marine plants and animals, including a number of commercially important species. Here, we review and synthesize existing knowledge on the functioning of kelp species as biogenic habitat providers. We examine biodiversity patterns associated with kelp holdfasts, stipes and blades, as well as the wider understorey habitat, and search for generality between kelp species and biogeographic regions. Environmental factors influencing biogenic habitat provision and the structure of associated assemblages are considered, as are current threats to kelp-dominated ecosystems. Despite considerable variability between species and regions, kelps are key habitat-forming species that support elevated levels of biodiversity, diverse and abundant assemblages and facilitate trophic linkages. Enhanced appreciation and better management of kelp forests are vital for ensuring sustainability of ecological goods and services derived from temperate marine ecosystems
Spatial variability in the diversity and structure of faunal assemblages associated with kelp holdfasts (<em>Laminaria hyperborea</em>) in the northeast Atlantic
No full text\ua9 2018 Teagle et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Kelp species are ecologically-important habitat-formers in coastal marine ecosystems, where they alter environmental conditions and promote local biodiversity by providing complex biogenic habitat for an array of associated organisms. While it is widely accepted that kelps harbour significant biodiversity, our current understanding of spatiotemporal variability in kelp-associated assemblages and the key environmental drivers of variability patterns remains limited. Here we examined the influence of ocean temperature and wave exposure on the structure of faunal assemblages associated with the holdfasts of Laminaria hyperborea, the dominant habitat-forming kelp in the northeast Atlantic. We sampled holdfasts from 12 kelp-dominated open-coast sites nested within four regions across the UK, spanning ~9 in latitude and ~2.7 C in mean sea surface temperature. Overall, holdfast assemblages were highly diverse, with 261 taxa representing 11 phyla recorded across the study. We examined patterns of spatial variability for sessile and mobile taxa separately, and documented high variability between regions, between sites within regions, and between replicate holdfasts for both assemblage types. Mobile assemblage structure was more strongly linked to temperature variability than sessile assemblage structure, which was principally structured by site-level variability in factors such as wave exposure. Patterns in the structure of both biogenic habitat and associated assemblages did not vary predictably along a latitudinal gradient in temperature, indicating that other processes acting across multiple spatial and temporal scales are important drivers of assemblage structure. Overall, kelp holdfasts in the UK supported high levels of diversity, that were similar to other kelp-dominated systems globally and comparable to those recorded for other vegetated marine habitats (i.e. seagrass beds), which are perhaps more widely recognised for their high biodiversity value
Climate-driven substitution of habitat-forming species leads to reduced biodiversity within a temperate marine community
No full textStates, firms, and oil : British policy, 1939-54
No full textNew
evidence
from the records of the Anglo-Iranian Oil Company (now British
Petroleum) and Shell for the period,
1939-45 supplements accounts of British
oil relations
based on state archives. This historical account demonstrates the continuity between the
interwar industry cartel and the Allied
wartime collaboration orchestrated through industry
committees. The
companies made use of their quasi-official position to manage crisis of
prewar arrangements aggravated by the war which presaged the rapid expansion of
postwar Middle East production. The companies then shaped the Anglo-American Oil
Agreements of
1944
and 1945, establishing a
basis for
remaking their position
in the
Middle East, expanding the web of
interfirm
relations. The nationalisation of
Anglo-
Iranian in 1951 threatened the web and the companies were able to embargo nationalised
Iranian oil and thus bankrupt the state. This society of oil majors was constituted by
shared
understandings and interests cultivated by the companies.
Structures of private governance may be quite significant factors for
states allied to them.
The United Kingdom
was more closely tied into the system of private governance that
prevailed in international oil
in the middle
decades of the century than was the United
States and consequently was able to call on more resources to resist
United States
initiatives during this period. British influence persisted in the oil
issue-area, in
spite of
greater
United States resources overall, because of this close working relationship
between state and companies. Close examination of the relationship reveals the extent of
penetration by the companies into both the decision-malting and implementation of
foreign
relations. The `national' interest was thus articulated through an interplay of
Governmental
and corporate agendas, and this supports a general argument that `national' power
is not
exercised solely
by the state, but by the state in
cooperation with other powerful social
institutions. Non-state actors and their archives may enrich the study of foreign relations
Results of univariate PERMANOVA to test for differences in habitat metrics (a. kelp age, b. total holdfast volume, c. habitable holdfast space and d. relative holdfast space).
No full textPermutations were based on a Euclidean distance similarity matrix generated from untransformed data. All tests used a maximum of 4999 permutations under a reduced model; significant effects (P<0.05) are shown in bold. An underlined P-value indicates that PERMDISP detected significant differences in within-group dispersion between levels of that factor (P<0.05).</p
Spatial variability in the diversity and structure of faunal assemblages associated with kelp holdfasts (<i>Laminaria hyperborea</i>) in the northeast Atlantic - Fig 4
No full textUnivariate assemblage-level metrics for sessile holdfast assemblages: (a) the proportion of major taxonomic groups, (b) sessile assemblage taxon richness, (c) total biomass of sessile organisms, (d) taxa equatorward range edge. Values for (b) and (c) are means of 6 replicate holdfasts per site (±SE).</p
Predictor variables recorded at 12 study sites within 4 distinct regions in the UK.
No full text‘Mean SST’ is the annual mean temperature calculated from satellite-derived sea surface temperature (SST) data (2005–2014). ‘Log wave fetch’ is a broad-scale metric of wave exposure, derived by summing fetch values calculated for 32 angular sectors surrounding each site (see [71]). ‘Log chl a mean’ is the average annual concentration of chlorophyll a (log10 mg m-3 from MODIS Aqua satellite data, 2002–2012). ‘Peak summer max (mean) temp’ is the maximum (average) daily temperature recorded between 26 July and 18 August 2014, when all sensor array deployments overlapped. ‘Summer daylight’ is the average daytime (08:00–20:00) light intensity during a 14 d deployment of light loggers. ‘Tidal water motion’ is a proxy for water movement driven by tidal flow, derived from the range in water motion values recorded during a 24 h period, averaged over the 45 d accelerometer deployment. ‘Wave water motion’ is a proxy for water movement driven by waves, derived from averaging the 3 highest-magnitude water motion values observed during the 45 d accelerometer deployment (following correction for tidal-movement). ‘PO43-‘ and ‘NO3- +NO2-‘ indicate averaged spring and summer concentrations of phosphate and nitrite + nitrate respectively (n = 4 water samples taken from ~1 m above the kelp canopy).</p
