Search

Finding effective solutions to manage marine resources is high on political and conservation agendas worldwide. This is made more urgent by the rate of increase in the human population and concomitant resource pressures in coastal areas. This paper links empirical socio-economic data about perceptions of marine resource health to the breaking of marine management rules, using fisheries as a case study. The relationship between perceived rule-breaking (non-compliance with regulations controlling fishing) and perceived health of inshore marine environments was investigated through face-to-face interviews with 299 heads of households in three Tanzanian coastal communities in November and December 2011. Awareness of rules controlling fishing activity was high among all respondents. Fishers were able to describe more specific rules controlling fishing practices than non-fishers (t = 3.5, df = 297, p<0.01). Perceived breaking of fishing regulations was reported by nearly half of all respondents, saying “some” (32% of responses) or “most” (15% of responses) people break fishing rules. Ordinal regression modelling revealed a significant linkage (z = −3.44, p<0.001) in the relationship between respondents' perceptions of deteriorating marine health and their perception of increased rule-breaking. In this paper, inferences from an empirical study are used to identify and argue the potential for using perceptions of ecosystem health and level of rule-breaking as a means to guide management measures. When considering different management options (e.g. Marine Protected Areas), policy makers are advised to take account of and utilise likely egoistic or altruistic decision-making factors used by fishers to determine their marine activities. [ABSTRACT FROM AUTHOR]

The temperate waters of the North-Eastern Atlantic have a long history of maritime resource richness and, as a result, the European Union is endeavouring to maintain regional productivity and biodiversity. At the intersection of these aims lies potential conflict, signalling the need for integrated, cross-border management approaches. This paper focuses on the marine megafauna of the region. This guild of consumers was formerly abundant, but is now depleted and protected under various national and international legislative structures. We present a meta-analysis of available megafauna datasets using presence-only distribution models to characterise suitable habitat and identify spatially-important regions within the English Channel and southern bight of the North Sea. The integration of studies from dedicated and opportunistic observer programmes in the United Kingdom and France provide a valuable perspective on the spatial and seasonal distribution of various taxonomic groups, including large pelagic fishes and sharks, marine mammals, seabirds and marine turtles. The Western English Channel emerged as a hotspot of biodiversity for megafauna, while species richness was low in the Eastern English Channel. Spatial conservation planning is complicated by the highly mobile nature of marine megafauna, however they are important components of the marine environment and understanding their distribution is a first crucial step toward their inclusion into marine ecosystem management. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, control of Hopf bifurcation for a plankton population model with a non-integer exponent of closure is studied. For the plankton model with the closure term varies continuously between the commonly used linear and quadratic forms, washout filter aided feedback controllers are employed to control the stability of the Hopf bifurcation, and thus the chaos could be eliminated. By employing the stability theorems derived, the stability of a control system is investigated. Finally numerical simulations are provided to show the effectiveness and feasibility of the developed methods. [Copyright &y& Elsevier]

In Europe there is an extensive history of the derivation and use of benthic indicators which parallels similar developments in North America and elsewhere. Most recently, this has increased because major European Union Directives require that indicators of marine benthic change are used to confirm good ecological status quality (as in the Water Framework Directive) and favourable conservation status (as in the Habitats and Species Directive). Furthermore, these indicators have to fit within the current philosophy of the Ecosystem Approach requiring the development and use of Ecological Quality Objectives and Standards. Despite this, comparisons of families of indicators derived by differing methods have not been carried out such that the robust nature of the indicators on differing spatial scales and under differing benthic conditions has not been rigorously assessed. Using case studies from the Portuguese coasts and estuaries, this paper compares and contrasts univariate and multivariate macrobenthic indicators to quantify comparisons of change. The studies indicate the relative value of those indicators at contrasting spatial scales, e.g. in the transition from small areas around coastal submarine outfalls, to the local and regional estuarine and coastal scale. The analysis indicates the difficulties of deriving and using qualitative and quantitative indicators from benthic communities in stable, and in moderately and highly variable environmental conditions in estuarine, coastal and open sea habitats. In some areas, the variability in the indicators and indices within a station and site is as large as that between stations and sites. For those areas studied, there is an adequate quality and quantity of benthic data available for making management decisions but this is unlikely to be the case for all areas. Similarly, the interrogation of the methods shows that while their use and interpretation rely on a good understanding of the biology of the individual species and their responses to physical and polluting stress, that understanding is not yet available for many of the species. Most notably, while the indices and integrative indicators are becoming increasingly sophisticated, many are still dependent on the Pearson–Rosenberg model for organic enrichment hence they require to be validated for physical disturbance and for chemical pollution. Because of these features, the outcome of the analysis has repercussions for the management of coastal and estuarine areas. Although the present study indicates the value of indicators of benthic change for making management decisions at the various scales, further validation is required especially, for example, where one indicator over-estimates the ecological status for poor areas and underestimates it for good areas. [Copyright &y& Elsevier]

Surface area measurement is a common component of benthic research, especially in the quantification of chlorophyll. Multiple techniques are available and 10 are described: artificial substrates, area-specific sampling, geometric approximation, stone shape equations, foil wrapping, grids, stamps, wetted layer, particle layer, and planar area measurement. A literature search of 130 papers indicated the most common methods: using artificial substrates of known area, subsampling a specific area using a template or sampler, measuring stone dimensions and using an equation to derive area, and using the weight of foil wrapped on stones. Methods were compared using spheres of known area, smooth and rough granite stones, and plastic macrophytes. Most methods produced highly correlated measurements and accurately estimated surface area. The wetted layer method was sensitive to stone roughness and plant complexity, but may overestimate the area of complex surfaces. Replication of one method by 10 biologists indicated that individual differences in technique can affect surface area values. Factors to consider in choosing an appropriate method include ease of use, characteristics of the substrates (e.g., porosity and flexibility), fineness of scale in measuring area, and whether methods must be field-based or can include laboratory techniques. [ABSTRACT FROM AUTHOR]

Morphological taxonomy is a critical component of all aspects of aquatic biology. Hydrobiologia receives many manuscripts that focus on descriptions of new species of aquatic organisms. We offer suggestions for how these papers can better conform to the stated aims and scope of Hydrobiologia, which read, in part: ‘ Hydrobiologia publishes original articles of interest to a broad and international audience. Purely descriptive work will be considered if it is firmly embedded in a larger biological framework’. In our opinion, taxonomic studies that classify new species are more likely to meet these aims if they state the species concept being used, and include additional experimental, analytical or conceptual analyses. For example, we recommend that studies that use morphological taxonomy also include independent tests of species boundaries, such as multivariate analyses, molecular genetic analyses, and/or tests of reproductive isolation. Given the constraints under which many taxonomists operate, collaboration might be the most effective strategy for achieving these goals. [ABSTRACT FROM AUTHOR]

Rapid progress has been made recently in the understanding of heavy metal sorption and speciation on sediment and soils. One aspect that was overlooked in the previous studies was the process of pollutant transformation and transportation in hyper-concentrated solid-liquid systems. In this paper, batch experiments on copper sorption in association with loess at high sediment concentrations were conducted. However, some reaction mechanisms were difficult to determine experimentally due to the limitations of speciation extraction methods. In an additional study, the MINTEQA2 chemical equilibrium model was used to calculate the speciation and precipitation of copper sorption by loess to give quantitative predictions and detailed information about the reaction process. The experiments and the modeling simulation were made under the same sorption conditions, with sediment concentrations ranging from 50 to 200 kg/m3 and adsorbates of CuSO4 and Cu(NO3)2, in order to compare their results. The modeling results clearly supported the experimental results, fully explained the mechanisms of the effects of chemical form and sediment concentration on the copper sorption, and strengthened the dominant role of carbonates among the main components of loess in the process of copper sorption. [ABSTRACT FROM AUTHOR]

The Langmuir equation has been widely used for description of the adsorption characteristics in different solid–liquid systems, although it was originally advanced for adsorption of gas molecules on a planar surface. In this paper, the applicability of the Langmuir equation was discussed when it is modified or extended to describe sorption on heterogeneous surfaces such as soils or soil components. The sorption of Cu(II) by loess was investigated experimentally with sediment concentration ranging from 10 to 100 kg/m3, and copper concentration from 64.80 to 7499 mg/l. The measured results were found well fitted with the nonlinear Langmuir isotherm in form, but for the loess with high carbonate content, the Cu precipitation becomes the primary mechanism instead of the original adsorption in the ordinary cases with low carbonate content. Thus, the parameters identified from the same Langmuir form would be essentially different in their physical meanings comparing with those in the conventional Langmuir equation. Using the MINTEQA model, copper precipitation was calculated and the implications of parameters in Langmuir equation were interpreted. Both the `sorption coefficient' and the `sorption maximum' in the Langmuir equation for copper precipitation are very close to those for copper sorption, but the `sorption coefficient' for copper precipitation is greater than that for copper sorption and oppositely for the `sorption maximum', which explains why precipitation dominates the sorption process. [ABSTRACT FROM AUTHOR]

The magnitude and frequency of events leading to changes in turbidity have been studied in a large (61 km2), shallow (mean depth 3.4 m) wind-exposed lake basin at the western end of Lake Mälaren, Sweden. In this paper we couple changes in suspended particulate inorganic material (SPIM) resulting from wind driven sediment resuspension, and variations in the discharge and sediment load, to spectral variations in subsurface light and estimates of photosynthetically active radiation (PAR). To accomplish this we use a semi-analytical model which predicts the spectral variations in downwelling irradiance (E d(λ)) and the attenuation coefficient of downwelling irradiance (K d(λ)), as a function of the concentrations of chlorophyll, dissolved yellow substances, and suspended inorganic and organic particulate material. Unusually high river discharge, led to large inputs of yellow substances and large in lake yellow substance concentrations (a ys(420) ≈ 20 m-1), causing variations in yellow substance concentration to have the greatest role in influencing temporal trends in the attenuation of PAR and variations in the depth of the euphotic zone (Z eup). In spite of this, variations in SPIM could account for approximately 60% of the variation in Z eup attributed to changes in yellow substances alone. Our results show that changes in suspended sediment concentration leads to both long-term and short-term changes in the attenuation of PAR, even in the presence of high concentrations of dissolved yellow substances. [ABSTRACT FROM AUTHOR]

In a classical paper, Hutchinson (1961) argued that the large number of species in most plankton communities is remarkable in view of the competitive exclusion principle, which suggests that in homogeneous, well-mixed environments species that compete for the same resources cannot coexist. Few ideas in aquatic ecology have evoked more research than this `paradox of the plankton'. This review is an effort to put the main solutions to the paradox that have been proposed over the years into perspective. Hutchinson himself already suggested that the explanation could be that plankton communities are not in equilibrium at all due to weather-driven fluctuations. Subsequent research confirmed that such externally imposed variability can allow many species to coexist. Another important point is that in practice the homogeneous well-mixed conditions assumed in the competitive exclusion principle hardly exist. Even the open ocean, for instance, has a spatial complexity resulting from meso-scale vortices and fronts that can facilitate coexistence of species. Perhaps most excitingly, theoretical work on species interactions has given a counter-intuitive new dimension to the understanding of diversity. Various competition and predation models suggest that even in homogeneous and constant environments plankton will never settle to equilibrium. Instead, interactions between multiple species may give rise to oscillations and chaos, with a continuous wax and wane of species within the community. Long-term laboratory experiments support this view. This chaotic behavior implies among other things that plankton dynamics are intrinsically unpredictable in the long run when viewed in detail. Nonetheless, on a higher aggregation level, indicators such as total algal biomass may show quite regular patterns. [ABSTRACT FROM AUTHOR]

Although evolutionary ecologists agree that proximate and ultimate aspects are two sides of one coin, they are seldom interested in studies on physiological and behavioural mechanisms at the base of ecological phenomena. Nevertheless, these mechanisms are objects of selection and evolved to realise adaptive significances. This paper is a plea to bring both fields closer together, and, by means of an example of Diel Vertical Migration of Daphnia, some proximate and ultimate aspects are discussed. It is argued that light changes, not fish kairomone, is the primary cause for an individual to swim downwards at dawn and upwards at dusk. However, what is called a causal factor might differ when ecosystems or individuals are studied. In addition, causality in ecology is not simple, and has the character of a `set of necessary conditions'. To illustrate the importance of proximate analyses in DVM, two basic response mechanisms are discussed: Photobehaviour system 1 and 2. The physiological character of these systems leads to a fixed type of migration or to a phenotypically induced DVM, respectively. The adaptive significance of the first might be a reduction of the hazardous effects of UV radiation and of the second a lowering of mortality due to visually hunting predators. [ABSTRACT FROM AUTHOR]

In this paper I review the three best-known aspects of community structure in the deep-sea benthos: depth gradients of species diversity, spatial dispersion, and faunal replacement with depth. Patterns of species diversity are documented for the megafaunal invertebrates and fishes and four macrofaunal taxa (bivalves, gastropods, cumaceans, and polychaetes). These trends and data on spatial dispersion provide the basis for evaluating theories of species diversity in the deep sea. I then compare rates of species replacement with depth in megafaunal and macrofaunal elements, and relate differences between the groups to life-history parameters and trophic roles. [ABSTRACT FROM AUTHOR]