Stochastic models for phytoplankton dynamics in Mediterranean Sea

In this paper, we review some results obtained from three one-dimensional stochastic models, which were used to analyze picophytoplankton dynamics in two sites of the Mediterranean Sea. Firstly, we present a stochastic advection–reaction–diffusion model to describe the vertical spatial distribution of picoeukaryotes in a site of the Sicily Channel. The second model, which is an extended version of the first one, is used to obtain the vertical stationary profiles of two groups of picophytoplankton, i.e. Pelagophytes and Prochlorococcus, in the same marine site as in the previous case. Here, we include intraspecific competition of picophytoplanktonic groups for limiting factors, i.e. light intensity and nutrient concentration. Finally, we analyze the spatio-temporal behaviour of five picophytoplankton populations in a site of the Tyrrhenian Sea by using a reaction–diffusion–taxis model. The study is performed, taking into account the seasonal changes of environmental variables, obtained starting from experimental findings. The multiplicative noise source, present in all three models, mimics the random fluctuations of temperature and velocity field. The vertical profiles of chlorophyll concentration obtained from the stochastic models show a good agreement with experimental data sampled in the two marine sites considered. The results could be useful to devise a new class of models based on a stochastic approach and able to predict future changes in biomass primary production.     

Quantifying urban ecological governance: A suite of indices characterizes the ecological planning implications of rapid coastal urbanization

Urban ecosystems in China have undergone a surge of rapid urbanization leading to phenomenal socio-ecological transformation. To mitigate the regional ecological and environmental impacts, cross-scale ecological governance has not been well established. This paper aims to propose an assessment framework to examine and understand urban ecological governance (UEG), a concept that intertwines multiple aspects such as governance, planning, and urban ecology into an integrated procedure for policy formulation and implementation. To test the assessment framework and thereby derive a quantitative approach to studying socio-ecological couplings within the urban systems, we choose Lianyungang, a rapid urbanizing coastal city in China for an empirical study. We ascertain each subsystem (e.g., urbanization, ecological, governance) presents a fluctuating trend particularly after 2005. Also, the overall trends of UEG increased slightly during the two study periods (1997–2012 and 2005–2012), mainly due to the influences of the Urban Master Plan and Eastern Coastal Regional Development Strategic Planning of Lianyungang. These results imply that the UEG in China’s local governments is unique, and the planning system especially acts a core player to cope with increasing regional ecological risks and uncertainties. It is suggested that China’s UEG needs to enhance experimental governance, ecological redline policy (ERP) and multi-plan integration and combine its current government-dominant top-down system with Western bottom-up decision-making mechanisms.     

Quasi-programmed aging of budding yeast: a trade-off between programmed processes of cell proliferation,differentiation, stress response,survival and death defines yeast lifespan

Recent findings suggest that evolutionarily distant organisms share the key features of the aging process and exhibit similar mechanisms of its modulation by certain genetic, dietary and pharmacological interventions. The scope of this review is to analyze mechanisms that in the yeast Saccharomyces cerevisiae underlie: (1) the replicative and chronological modes of aging; (2) the convergence of these 2 modes of aging into a single aging process; (3) a programmed differentiation of aging cell communities in liquid media and on solid surfaces; and (4) longevity-defining responses of cells to some chemical compounds released to an ecosystem by other organisms populating it. Based on such analysis, we conclude that all these mechanisms are programs for upholding the long-term survival of the entire yeast population inhabiting an ecological niche; however, none of these mechanisms is a ?program of aging? - i.e., a program for progressing through consecutive steps of the aging process.     

An approach to analysis of colonization dynamics in community functioning of protozoa for bioassessment of marine pollution

Biological trait analysis is a powerful tool to summarize the spatial/temporal patterns of community functioning and ecosystem process at taxon-free resolutions. To identify the optimal colonization period with high homogeneity in functional patterns of protozoa for bioassessment, 1-month baseline colonization survey was conducted in coastal waters of the Yellow Sea. A fuzzy-coding functional trait system was used to summarize the functional structure of protozoan communities during the colonization process. The functional patterns showed a low homogeneity during the early stage (3–7 days), followed by a stable stage (10–14 days) with high homogeneity, and the last stage (21–28 days) with high heterogeneity. The functional richness showed a low variability, while the functional evenness and divergence generally showed a decreasing trend during the whole colonization process. Furthermore, the functional dispersion and RaoQ indices generally leveled off only during the stable stage. These results suggest that it is necessary to determine the optimal exposure time period with high homogeneity of community functioning for bioassessment using protozoan colonization in marine ecosystems.     

Global Environmental Change and Population Health: Progress and Challenges

Escalating global environmental change (GEC) over the past century has been driven largely by rapid industrialization, population growth, overconsumption of natural resources, and associated waste disposal challenges, as well as the inappropriate uses of technology. These changes are already having and will increasingly continue to have significant impacts on human health and well-being. How to tackle these issues is an important challenge to scientists, policy-makers, and the general public. Scientific consensus now exists that GEC and population health are linked, even though the details and mechanisms underlying this link remain to be both explicated and quantified. In this article we provide an overview of progress and challenges in the area of GEC and population health since the late 1980s, highlighting some of the main landmarks in this area and recommending directions for future research.     

Net primary productivity of two mangrove forest stands on the northwestern coast of Sri Lanka

Productivity studies were carried out from September, 1985 to August, 1987 in two mangrove stands, i.e. estuarine and island fringing, in Dutch bay, a lagoon situated on the northwestern coast of Sri Lanka. Net above-ground primary productivity was measured by monitoring litterfall and above-ground biomass increment. The average annual rate of litterfall in the estuarine and island-fringing mangrove stands are 588.14 g m^–2 (approximately 6 t ha^–1) and 407.33 g m^–2 (approximately 4 t ha^–1) respectively. The average annual rates of above ground woody growth are 614.74 g m^–2 (approximately 6 t ha^–1) in the estuarine stands and 286.8 g m^–2 (approximately 3 t ha^–1) in the island-fringing mangrove stands. Hence estuarine mangrove stands record a higher annual rate of above-ground net primary production (NPP; 1207.88 g m^–2 or approximately 12 t ha^–1) than the fringing mangrove stands (694.22 g m^–2); approximately 7 t ha^–1). The annual rate of NPP in the water front zones of the stands (1300.47 g m^–2 in the estuarine stands and 874.56 g m^–2 in the fringing stands) are greater than those in the back-mangrove zones (115.28 g m^–2 in the estuarine stands and 513.88 g m^–2 in the island-fringing stands). These variations may be attributed to the differences in tidal flushing and influence of freshwater in the two localities.     

Characterization of the carbon fluxes of a vegetated drained lake basin chronosequence on the Alaskan Arctic Coastal Plain

Greenhouse gas fluxes from vegetated drained lake basins have been largely unstudied, although these land features constitute up to 47% of the land cover in the Arctic Coastal Plain in northern Alaska. To describe current and to better predict future sink/source activity of the Arctic tundra, it is important to assess these vegetated drained lake basins with respect to the patterns of and controls on gross primary production (GPP), net ecosystem exchange, and ecosystem respiration (ER). We measured CO₂ fluxes and key environmental variables during the 2007 growing season (June through August) in 12 vegetated drained lake basins representing three age classes (young, drained about 50 years ago; medium, drained between 50 and 300 years ago; and old, drained between 300 and 2000 years ago, as determined by Hinkel et al., 2003) in the Arctic Coastal Plain. Young vegetated drained lake basins had both the highest average GPP over the summer (11.4 gCO₂ m^?2 day^?1) and the highest average summer ER (7.3 gCO₂ m^?2 day^?1), while medium and old vegetated drained lake basins showed lower and similar GPP (7.9 and 7.2 gCO₂ m^?2 day^?1, respectively), and ER (5.2 and 4 gCO₂ m^?2 day^?1, respectively). Productivity decreases with age as nutrients are locked up in living plant material and dead organic matter. However, we showed that old vegetated drained lakes basins maintained relatively high productivity because of the increased development of ice‐wedge polygons, the formation of ponds, and the re‐establishment of very productive species. Comparison of the seasonal CO₂ fluxes and concomitant environmental factors over this chronosequence provides the basis for better understanding the patterns and controls on CO₂ flux across the coastal plain of the North Slope of Alaska and for more accurately estimating current and future contribution of the Arctic to the global carbon budget.     

Predation by cats could lead to the extinction of the Mediterranean endemic Yelkouan Shearwater Puffinus yelkouan at a major breeding site

Feral cats are considered to be one of the main harmful invasive species for island species. Adult shearwaters are highly vulnerable to predation by cats. The population of the Yelkouan Shearwater Puffinus yelkouan, a species endemic to the Mediterranean, is predicted to decline, leaving only a few large breeding colonies, due to the invasion of cats. The impact of cats on the Shearwater population of Le Levant Island, one of the major breeding sites for this species, was evaluated by studying cat diet over a 2‐year period. The predation rate obtained was then included in a Shearwater demographic model. Cats preyed upon rabbits, rats and Shearwaters, with a peak of predation on Shearwaters immediately upon their arrival at the colony. Cat predation was heavy and responsible for the yearly death of about 810–3241 birds. This could lead to the extinction of the Le Levant colony within the next four decades and perhaps within just a few years. Cat predation on prospecting individuals, a parameter essential to assess the real impact of predation, may not have an immediate effect on the Shearwater breeding population but can accelerate population extinction. Cat predation must be reduced or removed to prevent the extinction of one of the most important breeding sites for this species.     

Generalized fire response strategies in plants and animals

Despite the existing large body of research on plant–animal interactions, plant research and animal research are still relatively independent and asymmetrical in relation to disturbance. Animals and plants are likely to have different fire responses, yet biodiversity studies in relation to disturbance may benefit from a more integrated functional approach across kingdoms. This would also force us to go deeper into the biological mechanisms and scales for persistence than a taxonomic‐based classification. An integrated view of plant and animal responses would enable us to learn from a great variety of life forms and benefit from expertise in complementary disciplines. To achieve this integrated view, I propose a functional classification for both plants and animals in relation to their fire response strategy. This classification includes the following strategies: resistance, refugia, avoidance, dormancy, recolonization, crypsis and intolerance. Given the limited knowledge of fire responses for many organisms, and especially for many animals, this classification may require further development. However, it provides a framework that facilitates finding knowledge gaps and directing future research for gaining a better understanding of the role of fire on biodiversity.