Currently, our understanding of the mechanisms for, and potential functional implications of, changes in seabed assemblages resulting from dredged material disposal is relatively unknown. Based on ...empirical data from 17 disposal sites, we address this by quantifying the nature and magnitude of shifts in the relative composition of response and effects traits within disposal site assemblages relative to their reference assemblages.
Differing shifts in both response and effects traits were observed across sites, regardless of the trait composition of the reference assemblages. Notable differences in the magnitude of traits changes were also observed for both trait types. Traits shifts are difficult to predict as they appear to reflect both environmental conditions and disposal regime. Temporal data revealed that some sites display relatively consistent responses while others presented large inter-annual variability. These findings are discussed in relation to dredged material monitoring and with respect to conservation objectives of marine protected areas.
•Macrofaunal response and effects traits affected by dredged material disposal.•Nature and magnitude of traits shifts are variable between sites.•Traits shifts show notable variability between years.•Functional effects of disposal may not always be incompatible with management aims.
There is a growing need to understand the functional implications of anthropogenic pressures, such as those following coastal disposal of dredged material. Current assessments, based on taxonomic ...structure of benthic organisms, only provide a limited capacity to determine functional impacts or recovery. This study assesses recovery of two intertidal dredged material recharge schemes, comparing results obtained based on taxonomic structure (univariate and multivariate approaches) and function (biological trait composition, functional diversity, secondary production) of the benthic assemblages.
The assemblages recolonising both schemes were consistently less speciose, less densely-populated and exhibited multivariate community structures that differed from those of the reference areas. However, for both schemes metrics of functionality converged to those of reference areas, although some differences in trait composition persisted for up to 3 years.
These data support the proposition that impacts of, and recovery from, anthropogenic disturbance should be assessed using a combination of both functional and taxonomic structural approaches.
•Macrofaunal recolonisation occurred rapidly following recharge.•Uni- and multivariate assemblage structure of neither scheme recovered.•Both schemes attained functional diversity equivalent to references within 3 months.•Secondary production of recolonising assemblages was generally recovered.•Traits composition of recolonising assemblage remained different from reference.
Biological trait analysis (BTA) is increasingly being employed to improve our understanding of the ecological functioning of marine benthic invertebrate communities. However, changes in trait ...composition are seldomly compared with concomitant changes in metrics of ecological function. Consequently, inferences regarding the functional implications of any changes are often anecdotal; we currently have a limited understanding of the functional significance of the traits commonly used. In this study, we quantify the relationship between benthic invertebrate trait composition and secondary production estimates using data spanning almost the breadth of the UK continental shelf.
Communities described by their composition of 10 traits representing life history, morphology and behaviour showed strong relationships with variations in total secondary production. A much weaker relationship was observed for community productivity (or P:B), a measure of rate of energy turnover. Furthermore, the relationship between total production and multivariate taxonomic community composition was far weaker than that for trait composition. Indeed, the similarities between communities as defined by taxonomy were very different from those depicted by their trait composition. That is, as many studies have demonstrated, taxonomically different communities may display similar trait compositions, and vice versa. Finally, we found that descriptions of community trait composition vary greatly depending on whether abundance or biomass is used as the enumeration weighting method during BTA, and trait assessments based on biomass produced better relations with secondary production than those based on abundance. We discuss the significance of these findings with respect to BTA using marine benthic invertebrates.
•Secondary production varies greatly over the UK continental shelf.•Weighting method (abundance, biomass) strongly affects trait assessments.•Production is more related to trait composition than taxonomic composition.•Trait composition and taxonomic composition are only weakly linked.•Biological trait analysis describes functioning better than structural approaches.
There is an implicit requirement under contemporary policy drivers to understand the characteristics of benthic communities under anthropogenically-unimpacted scenarios. We used a trait-based ...approach on a large dataset from across the European shelf to determine how functional characteristics of unimpacted benthic assemblages vary between different sedimentary habitats.
Assemblages in deep, muddy environments unaffected by anthropogenic disturbance show increased proportions of downward conveyors and surface deposit-feeders, while burrowing, diffusive mixing, scavenging and predation traits assume greater numerical proportions in shallower habitats. Deep, coarser sediments are numerically more dominated by sessile, upward conveyors and suspension feeders. In contrast, unimpacted assemblages of coarse sediments in shallower regions are proportionally dominated by the diffusive mixers, burrowers, scavengers and predators. Finally, assemblages of gravelly sediments exhibit a relatively greater numerical dominance of non-bioturbators and asexual reproducers. These findings may be used to form the basis of ranking habitats along a functional sensitivity gradient.
•A trait-based approach is used to determine how functional characteristics of unimpacted assemblages vary between habitats.•Assemblages in deep, muddy environments show increased proportions of downward conveyors and surface deposit-feeders.•Deep, coarser sediments are numerically more dominated by sessile, upward conveyors and suspension feeders.•Coarse sediments in shallower regions are dominated by the diffusive mixers, burrowers, scavengers and predators.•These findings may be used to form the basis of ranking habitats along a functional sensitivity gradient.
While the effects of coastal disposal of dredged material on benthic assemblage structure have been well studied, our understanding of the mechanism of such responses, and their potential ecological ...implications, remain relatively unknown. Data from a licenced disposal site off the northeast coast of England are analysed to address this and improve our ability to make informed licencing decisions for this activity. Assemblages within the disposal site displayed reduced number of species and total invertebrate density, an altered assemblage taxonomic structure, and a shift towards a greater numerical dominance of less-productive individuals. Following separate analyses of biological response and effect traits, a novel approach for marine benthic trait analysis, we identify the traits responsible (i.e. response traits) for the observed structural alterations. Furthermore, analysis of the effect traits revealed that the assemblages characterising the disposal site possess a greater bioturbative capability compared to those not directly impacted by disposal.
•Benthic community structure was impacted by dredge material disposal.•Alterations to taxonomic composition reduced secondary production.•Response and effect traits were separated prior to Biological Traits Analysis.•This novel trait approach provided an improved assessment of functional change.
The circadian clock is a specialised cell signalling circuit present in almost all cells. It controls the timing of key cell activities such as proliferation and differentiation. In osteoarthritis, ...expression of two components of the circadian clock, BMAL1 and PER2 is altered in chondrocytes and this change has been causally linked with the increase in proliferation and altered chondrocyte differentiation in disease. IL-1β, an inflammatory cytokine abundant in OA joints, has previously been shown to induce changes in BMAL1 and PER2 expression in chondrocytes. The purpose of this study is to identify the mechanism involved.
We found IL-1β treatment of primary human chondrocytes led to activation of NMDA receptors as evidenced by an increase in phosphorylation of GluN1 and an increase in intracellular calcium which was blocked by the NMDAR antagonist MK801. Levels of phosphorylated CREB were also elevated in IL-1β treated cells and this effect was blocked by co-treatment of cells with IL-1β and the NMDAR antagonist MK-801. Knockdown of CREB or inhibition of CREB activity prevented the IL-1β induced increase in PER2 expression in chondrocytes but had no effect on BMAL1. Phosphorylated p65 levels were elevated in IL-1β treated chondrocytes indicating increased NF-κB activation. Inhibition of NF-κB activity prevented the IL-1β induced reduction in BMAL1 expression and partially mitigated the IL-1β induced increase in PER2 expression in chondrocytes. These data indicate that the NMDAR/CREB and NF-κB signalling pathways regulate the core circadian clock components PER2 and BMAL1 in chondrocytes. Given that changes in expression of these clock components have been observed in a wide range of diseases, these findings may be broadly relevant for understanding the mechanism leading to circadian clock changes in pathology.
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•IL-1β regulates expression of the core circadian clock components PER2 and BMAL1 in chondrocytes.•IL-1β activates NMDA receptors on chondrocytes leading to increased CREB activation.•CREB activity contributes to the IL-1β induced increase in peak expression of PER2 in chondrocytes.•IL-1β reduces BMAL1 expression in chondrocytes through NF-κB activation.•NF-κB activity also contributes to the IL-1β induced increase in peak PER2 levels in chondrocytes.
Although many studies have investigated the effects of disturbance and environmental drivers on marine ecosystems, comparatively few have studied their interactions. Using fuzzy coded biological ...traits, we compared the functional composition, diversity and evenness of benthic communities in the English Channel and in the Celtic and Irish Seas across interacting gradients of bottom trawling and primary production. Fuzzy correspondence analysis indicated greater similarity in trait composition at sites of high trawling pressure than at those of low trawling. In contrast, the analysis revealed no relationship between trait composition and primary production. Trawling and primary production had no effect on the traits ‘longevity’, ‘sediment position’, or ‘feeding mode’. However, trawling had negative effects on all modalities within the trait ‘living habit’, and these effects were strongest for attached and epifaunal organisms but weakest for burrow- and tube-dwelling species. Trawling also negatively affected most modalities within the trait ‘maximum weight’, with strongest effects for organisms weighing between <0.1 g and up to 1 kg. Conversely, trawling positively affected organisms weighing >10 kg. For the trait ‘bioturbation’, upward conveyors were positively related with primary production, whilst other modalities exhibited no clear pattern. Because trawling affected some traits more than others, community biomass was less evenly distributed across traits in highly trawled areas, which resulted in lower levels of functional diversity and evenness. Overall, the effects of bottom trawling were greater in areas of high primary production.
Abstract
Fisheries using bottom trawls are the most widespread source of anthropogenic physical disturbance to seafloor habitats. To mitigate such disturbances, the development of fisheries-, ...conservation-, and ecosystem-based management strategies requires the assessment of the impact of bottom trawling on the state of benthic biota. We explore a quantitative and mechanistic framework to assess trawling impact. Pressure and impact indicators that provide a continuous pressure–response curve are estimated at a spatial resolution of 1 × 1 min latitude and longitude (∼2 km2) using three methods: L1 estimates the proportion of the community with a life span exceeding the time interval between trawling events; L2 estimates the decrease in median longevity in response to trawling; and population dynamic (PD) estimates the decrease in biomass in response to trawling and the recovery time. Although impact scores are correlated, PD has the best performance over a broad range of trawling intensities. Using the framework in a trawling impact assessment of ten métiers in the North Sea shows that muddy habitats are impacted the most and coarse habitats are impacted the least. Otter trawling for crustaceans has the highest impact, followed by otter trawling for demersal fish and beam trawling for flatfish and flyshooting. Beam trawling for brown shrimps, otter trawling for industrial fish, and dredging for molluscs have the lowest impact. Trawling is highly aggregated in core fishing grounds where the status of the seafloor is low but the catch per unit of effort (CPUE) per unit of impact is high, in contrast to peripheral grounds, where CPUE per unit of impact is low.
Demersal trawling constitutes the most significant human impact on both the structure and functioning of coastal seabed fauna. While a number of studies have assessed the impacts of trawling on ...faunal community structure and the degree to which different taxa are vulnerable to trawling, few have focused on how these impacts affect important ecological functions of the seabed. In this study, we use biological trait analysis (BTA) to assess the relative sensitivity of benthic macrofauna to trawling, in both the short- and long-term, and use this information to describe the spatial variation in sensitivity of secondary production for the Greater North Sea (GNS).
Within the GNS, estimates of total production varied by almost three orders of magnitude, from 1.66kJm−2y−1 to 968.9kJm−2y−1. Large-scale patterns were observed in the proportion of secondary production derived from trawling-sensitive taxa. In the southern North Sea, total production is predominantly governed by taxa with low sensitivity to trawling, whereas production is relatively trawling-sensitive in the northern North Sea and western English Channel. In general, the more sensitive and productive regions are associated with poorly-sorted, gravelly or muddy sediments, while the less sensitive and less productive regions are associated with well-sorted, sandy substrates. These relationships between production sensitivity and environmental features are primarily due to variations in long-term recovery; total production of most assemblages is highly sensitive to the direct impacts of trawling. We discuss the implications of these findings for management 1decisions to improve the environmental sustainability of trawling.
•Secondary production estimates greatly vary for the Greater North Sea.•Total production in the southern North Sea is by taxa with low trawling sensitivity.•Production is relatively trawl-sensitive in northern North Sea and western Channel.•Production sensitivity is correlated with sediment granulometric properties.•These findings can aid fisheries managers identify areas for protection.
Stable isotope analyses of the abundant infaunal polychaete Hediste diversicolor, recognised as an indicator of sewage pollution, support the hypothesis that nutrient enrichment promotes surface ...deposit feeding, over suspension feeding and predation. At sewage-polluted sites in three estuaries in SE England Hediste mainly consumed microphytobenthos, sediment organic matter and filamentous macroalgae Ulva spp. At cleaner sites Hediste relied more on suspension feeding and consumption of Spartina anglica. There were no consistent differences in Hediste densities between the polluted and cleaner sites, probably because of increased densities at the cleaner sites too, facilitated by the planting of Spartina and nitrogen enrichment there too, including from agricultural run-off. Increased nutrient enrichment and the artificial availability of Spartina have probably increased densities of, and deposit-feeding by, Hediste in the past half-century and contributed indirectly to saltmarsh losses, since deposit-feeding by Hediste has been implicated in recent saltmarsh erosion in SE England.
•Nitrogen (sewage) pollution promotes surface deposit-feeding by Nereis diversicolor.•In less polluted areas Spartina anglica detritus is important in Nereis diets.•These two anthropogenic factors have probably increased Nereis densities.•Deposit-feeding and herbivory by Nereis contributes to erosion of saltmarsh creeks.•Saltmarsh management should attempt to alleviate this artificial cause of erosion.
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