A complete analytic theory for structure and dynamics of populations and communities spanning wide ranges in body size

The prediction and management of ecosystem responses to global environmental change would profit from a clearer understanding of the mechanisms determining the structure and dynamics of ecological communities. The analytic theory presented here develops a causally closed picture for the mechanisms controlling community and population size structure, in particular community size spectra, and their dynamic responses to perturbations, with emphasis on marine ecosystems. Important implications are summarised in non-technical form. These include the identification of three different responses of community size spectra to size-specific pressures (of which one is the classical trophic cascade), an explanation for the observed slow recovery of fish communities from exploitation, and clarification of the mechanism controlling predation mortality rates. The theory builds on a community model that describes trophic interactions among size-structured populations and explicitly represents the full life cycles of species. An approximate time-dependent analytic solution of the model is obtained by coarse graining over maturation body sizes to obtain a simple description of the model steady state, linearising near the steady state, and then eliminating intraspecific size structure by means of the quasi-neutral approximation. The result is a convolution equation for trophic interactions among species of different maturation body sizes, which is solved analytically using a novel technique based on a multiscale expansion.

Marine spatial planning from the perspective of a small seaside community in Ireland

Marine spatial planning (MSP) is advocated as a means of managing human uses of the sea in a manner that is consistent with the maintenance of the ecological goods and services of the marine environment. Support for the process is evident at international and national levels but the degree to which it is acceptable to local level stakeholders is not clear. An Daingean (formely Dingle) is a small sea-oriented town situated on the southwest coast of Ireland in which marine-based tourism and other relatively new uses of the sea are pursued along side traditional fishing activities. Stakeholders in An Daingean are found to be positively disposed to a local process of MSP that incorporates meaningful local involvement.

Food web indicators under the Marine Strategy Framework Directive: From complexity to simplicity?

The Marine Strategy Framework Directive (MSFD) requires that European Union Member States achieve "Good Environmental Status" (GES) in respect of 11 Descriptors of the marine environment by 2020. Of those, Descriptor 4, which focuses on marine food webs, is perhaps the most challenging to implement since the identification of simple indicators able to assess the health of highly dynamic and complex interactions is difficult. Here, we present the proposed food web criteria/indicators and analyse their theoretical background and applicability in order to highlight both the current knowledge gaps and the difficulties associated with the assessment of GES. We conclude that the existing suite of indicators gives variable focus to the three important food web properties: structure, functioning and dynamics, and more emphasis should be given to the latter two and the general principles that relate these three properties. The development of food web indicators should be directed towards more integrative and process-based indicators with an emphasis on their responsiveness to multiple anthropogenic pressures. (C) 2013 Elsevier Ltd. All rights reserved.

Hydrological and photochemical influence on dynamics of estuarine bacteria

Os estuários são ecossistemas complexos, onde os processos físicos, químicos e biológicos estão intimamente ligados. A dinâmica bacteriana num estuário reflete a interação e a elevada variação temporal e espacial desses processos. Este trabalho teve como objetivo elucidar as interações entre os processos físicos, fotoquímicos e microbiológicos no sistema estuarino da Ria de Aveiro (Portugal). Para tal, foi realizada uma abordagem inicial no campo, durante a qual as comunidades bacterianas na coluna de água foram caracterizadas em termos de abundância e atividade ao longo de 2 anos. O estudo foi realizado em dois locais distintos, escolhidos por tipificarem as características marinhas e salobras do estuário. Estes locais possuem diferentes hidrodinâmicas, influências fluviais e, quantidade e composição de matéria orgânica. Numa perspectiva mecanicista, foram realizadas simulações laboratoriais no sentido de elucidar a resposta das bactérias à matéria orgânica foto-transformada. As comunidades bacterianas no estuário adaptam-se a diferentes regimes de água doce, desenvolvendo padrões de abundância e atividade distintos nas zonas marinha e salobra. Os elevados caudais dos rios induzem estratificação vertical na zona marinha, promovendo o fluxo de fitoplâncton do mar para o estuário, do bacterioplâncton do estuário para o mar, e estimulam a importação de bactérias aderentes a partículas na zona salobra. O transporte advectivo e os processos de ressuspensão contribuem para aumentar 3 vezes o número de bactérias aderentes a partículas durante os períodos de intensas descargas fluviais. Adicionalmente, a atividade bacteriana no estuário é controlada pela concentração de azoto inerente à variações de água doce. O fornecimento de azoto em associação com a fonte dos substratos bacterianos induzem alterações significativas na produtividade. O padrão de variação vertical de comunidades bacterianas foi distinto nas duas zonas do estuário. Na zona marinha, as bactérias na microcamada superficial (SML) apresentaram taxas de hidrólise mais elevadas, mas menores taxas de incorporação de monómeros e produção de biomassa que na água subjacente (UW), enquanto na zona salobra, as taxas de hidrólise e incorporação foram similares nos dois compartimentos, mas a produtividade foi significativamente mais elevada na SML. Apesar da abundância bacteriana ter sido semelhante na SML e UW, a fração de células aderentes a partículas foi significativamente maior na SML (2-3 vezes), em ambas as zonas do estuário. A integração dos resultados microbiológicos com as variáveis ambientais e hidrológicos mostraram que fortes correntes na zona marinha promovem a mistura vertical, inibindo o estabelecimento de uma comunidade bacteriana na SML distinta da UW. Em contraste, na zona de água salobra, a menor velocidades das correntes fornece as condições adequadas ao aumento da atividade bacteriana na SML. Características específicas do local, tais como a hidrodinâmica e as fontes e composição da matéria orgânica, conduzem também a diferentes graus de enriquecimento superficial de matéria orgânica e inorgânica, influenciando a sua transformação. Em geral, o ambiente da SML estuarina favorece a hidrólise de polímeros, mas inibe a utilização de monómeros, comparativamente com água subjacente. No entanto, as diferenças entre as duas comunidades tendem a atenuar-se com o aumento da atividade heterotrófica na zona salobra. A matéria orgânica dissolvida cromófora (CDOM) das duas zonas do estuário possui diferentes características espectrais, com maior aromaticidade e peso molecular médio (HMW) na zona de água salobra, em comparação com a zona marinha. Nesta zona, a abundância bacteriana correlacionou-se com a350 e a254, sugerindo uma contribuição indireta das bactéria para HMW CDOM. A irradiação do DOM resultou numa diminuição dos valores de a254 e a350, e, em um aumento do declive S275-295 e dos rácios E2:E3 (a250/a365) e SR. No entanto, a extensão de transformações foto-induzidas e as respostas microbianas são dependentes das características iniciais CDOM, inferidas a partir das suas propriedades ópticas. A dinâmica estuarina influencia claramente as atividades heterotróficas e a distribuição dos microorganismos na coluna de água. A entrada de água doce influencia a dinâmica e os principais reguladores das comunidades bacterianas no estuário. Os processos fotoquímicos e microbianos produzem alterações nas propriedades ópticas da CDOM e a combinação desses processos determina o resultado global e o destino da CDOM nos sistemas estuarinos com influência na produtividade nas áreas costeiras adjacente.

Microphytoplankton community structure in the North Eastern Arabian Sea during Winter Monsoon

The overall attempt of the study was aimed to understand the microphytoplankton community composition and its variations along a highly complex and dynamic marine ecosystem, the northern Arabian Sea. The data generated provides a first of its kind knowledge on the major primary producers of the region. There appears significant response among the microphytoplankton community structure towards the variations in the hydrographic conditions during the winter monsoon period. Interannually, variations were observed within the microphytoplankton community associated with the variability in temperature patterns and the intensity of convective mixing. Changing bloom pattern and dominating species among the phytoplankton community open new frontiers and vistas towards more intense study on the biological responses towards physical processes. The production of large amount of organic matter as a result of intense blooming of Noctiluca as well as diatoms aggregations augment the particulate organic substances in these ecosystem. This definitely influences the carbon dynamics of the northern Arabian Sea. Detailed investigations based on time series as well as trophodynamic studies are necessary to elucidate the carbon flux and associated impacts of winter-spring blooms in NEAS. Arabian sea is considered as one among the hotspot for carbon dynamics and the pioneering records on the major primary producers fuels carbon based export production studies and provides a platform for future research. Moreover upcoming researches based on satellite based remote sensing on productivity patterns utilizes these insitu observations and taxonomic data sets of phytoplankton for validation of bloom specific algorithm development and its implementation. Furthermore Saurashtra coast is considered as a major fishing zone of Indian EEZ. The studies on the phytoplankton in these regions provide valuable raw data for fishery prediction models and identifying fishing zones. With the Summary and Conclusion 177 baseline data obtained further trophodynamic studies can be initiated in the complex productive North Eastern Arabian Seas (NEAS) ecosystem that is still remaining unexplored.

Vegetation and environmental dynamics in the southern Black Sea region since 18 kyr BP derived from the marine core 22-GC3

Sediments from the Black Sea, a region historically dominated by forests and steppe landscapes, are a valuable source of detailed information on the changes in regional terrestrial and aquatic environments at decadal to millennial scales. Here we present multi-proxy environmental records (pollen, dinoflagellate cysts, Ca, Ti and oxygen isotope data) from the uppermost 305 cm of the core 22-GC3 (42°13.53′N, 36°29.55′E) collected from a water depth of 838 m in the southern part of the Black Sea in 2007. The records span the last ~ 18 kyr (all ages are given in cal kyr BP). The pollen data reveal the dominance of the Artemisia-steppe in the region, suggesting rather dry/cold environments ~ 18–14.5 kyr BP. Warming/humidity increase during melt-water pulses (~ 16.1–14.5 kyr BP), indicated by δ18O records from the 22-GC3 core sediment and from the Sofular Cave stalagmite, is expressed in more negative δ13C values from the Sofular Cave, usually interpreted as the spreading of C3 plants. The records representing the interstadial complex (~ 14.5–12.9 kyr BP) show an increase in temperature and moisture, indicated by forest development, increased primary productivity and reduced surface run-off, whereas the switch from primary terrigenous to primary authigenic Ca origin occurs ~ 500 yr later. The Younger Dryas cooling is clearly demonstrated by more negative δ13C values from the Sofular Cave and a reduction of pines. The early Holocene (11.7–8.5 kyr BP) interval reveals relatively dry conditions compared to the mostly moist and warm middle Holocene (8.5–5 kyr BP), which is characterized by the establishment of the species-rich warm mixed and temperate deciduous forests in the low elevation belt, temperate deciduous beech-hornbeam forests in the middle and cool conifer forest in upper mountain belt. The border between the early and middle Holocene in the vegetation records coincides with the opening of the Mediterranean corridor at ~ 8.3 kyr BP, as indicated by a marked change in the dinocyst assemblages and in the sediment lithology. Changes in the pollen assemblages indicate a reduction in forest cover after ~ 5 kyr BP, which was likely caused by increased anthropogenic pressure on the regional vegetation.

The relationship between community-based organisations and the effective management of coastal and marine resources in the Western Indian Ocean region

This study examines the relationship between community based organisations and marine and coastal resource management in the Western Indian Ocean Region.

Effects of plant pathogens on population dynamics and community composition in grassland ecosystems: two case studies

Grassland ecosystems comprise a major portion of the earth’s terrestrial surface, ranging from high-input cultivated monocultures or simple species mixtures to relatively unmanaged but dynamic systems. Plant pathogens are a component of these systems with their impact dependent on many interacting factors, including grassland species population dynamics and community composition, the topics covered in this paper. Plant pathogens are affected by these interactions and also act reciprocally by modifying their nature. We review these features of disease in grasslands and then introduce the 150-year long-term Park Grass Experiment (PGE) at Rothamsted Research in the UK. We then consider in detail two plant-pathogen systems present in the PGE, Tragopogon pratensis-Puccinia hysterium and Holcus lanata-Puccinia coronata. These two systems have very different life history characteristics: the first, a biennial member of the Asteraceae infected by its host-specific, systemic rust; the second, a perennial grass infected by a host-non-specific rust. We illustrate how observational, experimental and modelling studies can contribute to a better understanding of population dynamics, competitive interactions and evolutionary outcomes. With Tragopogon pratensis-Puccinia hysterium, characterised as an “outbreak” species in the PGE, we show that pathogen-induced mortality is unlikely to be involved in host population regulation; and that the presence of even a short-lived seed-bank can affect the qualitative outcomes of the host-pathogen dynamics. With Holcus lanata-Puccinia coronata, we show how nutrient conditions can affect adaptation in terms of host defence mechanisms, and that co-existence of competing species affected by a common generalist pathogen is unlikely.

Fungal community associated with marine macroalgae from Antarctica

Filamentous fungi and yeasts associated with the marine algae Adenocystis utricularis, Desmarestia anceps, and Palmaria decipiens from Antarctica were studied. A total of 75 fungal isolates, represented by 27 filamentous fungi and 48 yeasts, were isolated from the three algal species and identified by morphological, physiological, and sequence analyses of the internal transcribed spacer region and D1/D2 variable domains of the large-subunit rRNA gene. The filamentous fungi and yeasts obtained were identified as belonging to the genera Geomyces, Antarctomyces, Oidiodendron, Penicillium, Phaeosphaeria, Aureobasidium, Cryptococcus, Leucosporidium, Metschnikowia, and Rhodotorula. The prevalent species were the filamentous fungus Geomyces pannorum and the yeast Metschnikowia australis. Two fungal species isolated in our study, Antarctomyces psychrotrophicus and M. australis, are endemic to Antarctica. This work is the first study of fungi associated with Antarctic marine macroalgae, and contributes to the taxonomy and ecology of the marine fungi living in polar environments. These fungal species may have an important role in the ecosystem and in organic matter recycling.

Population dynamics of genetically diverse Plasmodium falciparum lineages: community-based prospective study in rural Amazonia

Temporal changes in the prevalence of antigenic variants in Plasmodium falciparum populations have been interpreted as evidence of immune-mediated frequency-dependent selection, but evolutively neutral processes may generate similar patterns of serotype replacement. Over 4 years, we investigated the population dynamics of P. falciparum polymorphisms the community level by using 11 putatively neutral microsatellite markers. Plasmodium falciparum Populations were less diverse than sympatric P. vivax isolates, with less multiple-clone infections, lower number of alleles per locus and lower Virtual heterozygosity, but both species showed significant multilocus linkage disequilibrium. Evolutively neutral P. falciparum polymorphisms showed a high turnover rate, with few lineages persisting for several months in the population. Similar results had previously been obtained, in the same community, for sympatric P. vivax isolates. In contrast, the prevalence of the 2 dimorphic types of a major antigen, MSP-2, remained remarkably stable throughout the Study period. We Suggest that the relatively fast turnover of parasite lineages represents the typical population dynamics of neutral polymorphisms in small populations, with clear implications for the detection of frequency-dependent selection of polymorphisms.

Community structure and dynamics in climate networks

We consider climate networks constructed from observed and model simulated fields of three climate variables and investigate their community structure. We find that for all fields the number of effective communities is rather small (four to five). We are able to trace the origin of these communities to certain dynamical properties of climate. Our results suggest that the complete complexity of the climate system condenses beyond the `weather` time scales into a small number of low-dimensional interacting components and provide clues as to the nature of the climate subsystems underlying these components.

The succession dynamics of a macroalgal community after a flood disturbance in a tropical stream from São Paulo State, southeastern Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)