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PubMed2006

Sequentially assembled food webs and extremum principles in ecosystem ecology.

1. Successional changes during sequential assembly of food webs were examined. This was carried out by numerical methods, drawing one species at a time from a species pool and obtaining the permanent (persistent) community emerging at each step. Interactions among species were based on some simple rules about body sizes of consumers and their prey, and community dynamics were described in terms of flows of biomass density. 2. Sequential assembly acted as a sieve on the communities, assembled communities having many properties different on average from those of feasible, stable communities taken at random from the species pools. 3. Time-series of community development were consistent with certain functions thought to go to an extremum (maximum or minimum) in ecosystem ecology, including a rapid early increase in net primary productivity and ascendency, although a clear trend in total biomass density was not evident and resilience decreased rather than increased. 4. In addition, more gradual changes in food web structure took place during succession to which the ecosystem goal functions were relatively insensitive. These changes included gradual increases in the number of species, invasion resistance, number of loops of length > 2 and number of prey species per consumer species. 5. We therefore argue that ecosystem and community dynamics can offer complementary insights into the process of ecological succession. The extremum principles of ecosystem ecology highlight some of the major properties of succession, whereas the community ecology sheds light on some more subtle changes taking place within the networks.

Animals↗

PubMed1994

Aye-ayes: specialists on structurally defended resources.

During the course of a 2-year field study on aye-ayes (Daubentonia madagascariensis), data were collected on dietary composition, food acquisition and structural properties of food resources. Aye-ayes in this study sampled remarkably few species from a variety of food types. A majority of these resources were heavily structurally defended and therefore difficult of access for other mammals. Aye-ayes used their modified finger and anterior teeth to harvest most of these resources.

Animals↗

PubMed2004

Impact of climate change on marine pelagic phenology and trophic mismatch.

Phenology, the study of annually recurring life cycle events such as the timing of migrations and flowering, can provide particularly sensitive indicators of climate change. Changes in phenology may be important to ecosystem function because the level of response to climate change may vary across functional groups and multiple trophic levels. The decoupling of phenological relationships will have important ramifications for trophic interactions, altering food-web structures and leading to eventual ecosystem-level changes. Temperate marine environments may be particularly vulnerable to these changes because the recruitment success of higher trophic levels is highly dependent on synchronization with pulsed planktonic production. Using long-term data of 66 plankton taxa during the period from 1958 to 2002, we investigated whether climate warming signals are emergent across all trophic levels and functional groups within an ecological community. Here we show that not only is the marine pelagic community responding to climate changes, but also that the level of response differs throughout the community and the seasonal cycle, leading to a mismatch between trophic levels and functional groups.

Animals↗

PubMed2004

Feeding practices of infants through the first year of life in Italy.

AIM: To investigate infant feeding practices through the first year of life in Italy, and to identify factors associated with the duration of breastfeeding and early introduction of solid foods. METHODS: Structured phone interviews on feeding practices were conducted with 2450 Italian-speaking mothers randomly selected among women who delivered a healthy-term singleton infant in November 1999 in Italy. Interviews were performed 30 d after delivery and when the infants were aged 3, 6, 9 and 12 mo. Type of breastfeeding was classified according to the WHO criteria. RESULTS: Breastfeeding started in 91.1% of infants. At the age of 6 and 12 mo, respectively, 46.8% and 11.8% of the infants was still breastfed, 68.4% and 27.7% received formula, and 18.3% and 65.2% were given cow's milk. Solids were introduced at the mean age of 4.3 mo (range 1.6-6.5 mo). Introduction of solids occurred before age 3 and 4 mo in 5.6% and 34.2% of infants, respectively. The first solids introduced were fruit (73.1%) and cereals (63.9%). The main factors (negatively) associated with the duration of breastfeeding were pacifier use (p < 0.0001), early introduction of formula (p < 0.0001), lower mother's age (p < 0.01) and early introduction of solids (p = 0.05). Factors (negatively) associated with the introduction of solids foods before the age of 3 mo were mother not having breastfed (p < 0.01), early introduction of formula (p < 0.01), lower infant bodyweight at the age of 1 mo (p = 0.05) and mother smoking (p = 0.05). CONCLUSION: The duration of breastfeeding in Italy is still inadequate, as well as compliance with international recommendations for timing of introduction of complementary foods. National guidelines, public messages and educational campaigns should be promoted in Italy.

Breast Feeding↗

PubMed2002

Community and ecosystem level consequences of chemical cues in the plankton.

Aquatic organisms produce compounds that deter consumers, alter prey behavior, suppress or kill target and nontarget species, and dramatically affect food-web structure, community composition, and the rates and pathways of biogeochemical cycles. Toxins from marine and freshwater phytoplankton create health hazards for both aquatic and terrestrial species and can significantly affect human activities and the economic vitality of local communities. A reasonable case can be made that phytoplankton metabolites such as dimethyl sulfide (DMS) link interaction webs that span hundreds to thousands of kilometers and connect production from oceanic phytoplankton to desert cacti and coyotes via zooplankton, fishes, and sea birds. The possible role of DMS in global heat budgets expands this effect even further. The ecosystem-wide and potentially global consequences of aquatic chemical cues is an underappreciated topic that warrants additional attention.

Air Movements↗

PubMed2004

Unified spatial scaling of species and their trophic interactions.

Two largely independent bodies of scaling theory address the quantitative relationships between habitat area, species diversity and trophic interactions. Spatial theory within macroecology addresses how species richness scales with area in landscapes, while typically ignoring interspecific interactions. Complexity theory within community ecology addresses how trophic links scale with species richness in food webs, while typically ignoring spatial considerations. Recent studies suggest unifying these theories by demonstrating how spatial patterns influence food-web structure and vice versa. Here, we follow this suggestion by developing and empirically testing a more unified scaling theory. On the basis of power-law species-area relationships, we develop link-area and non-power-law link-species models that accurately predict how trophic links scale with area and species richness of microcosms, lakes and streams from community to metacommunity levels. In contrast to previous models that assume that species richness alone determines the number of trophic links, these models include the species' spatial distribution, and hence extend the domain of complexity theory to metacommunity scales. This generality and predictive success shows how complexity theory and spatial theory can be unified into a much more general theory addressing new domains of ecology.

Animals↗

PubMed2003

The Seto Inland Sea--eutrophic or oligotrophic?

The present water quality conditions in the Seto Inland Sea of Japan are described along with an historical background before and after the measures taken to reduce eutrophication. The directive to reduce phosphorus discharge into this area was very effective, reducing the number of red tides from about 300 cases per year at their peak in 1976 to the recent level of about 100 cases per year, indicating the improvement of seawater quality. However, the hastiness of the measures taken to reduce phosphorous seems to have led to a depletion of dissolved inorganic phosphorus that is an essential nutrient for the growth of phytoplankton. Fishery production has also decreased with the reduction of phosphorus, showing a time lag, and the relationship between them shows a hysteresis-like pattern indicating that the condition of fishery production is currently in a critical stage of collapse. This implies that the phosphorus reduction could have lowered the phytoplankton primary production and also caused a detrimental effect on the fishery production. Noteworthy is the change in the phytoplankton species composition. The dominant species that form red tides have changed from non-harmful diatoms to harmful raphidophytes in the eutrophication process and then finally to harmful/toxic dinoflagellates in the oligotrophication process. This indicates that the measures to reduce phosphorus have caused a change in phytoplankton species composition, thereby altering the food web structure, suggesting that this might be the major cause of the reduction of fishery production. In conclusion, the Seto Inland Sea of Japan is apparently in an oligotrophic condition, and it could be said to be in the state of "cultural oligotrophication" caused by the hasty reduction of phosphorus loading. Dam construction, as another possible cause of the cultural oligotrophication, is also discussed, and evidence relating to the existence of numerous dams in this area is also shown. Stress is placed on the regulation of the level of nutrients and their elemental ratio in the seawater, because these factors are considered to be effective in preventing the generation of harmful algae and in sustaining the fishery production through preservation of the natural environment. A proposal is also described regarding how these factors could be controlled.

Environmental Monitoring↗

PubMed2006

Long-term change in benthopelagic fish abundance in the abyssal northeast Pacific Ocean.

Food web structure, particularly the relative importance of bottom-up and top-down control of animal abundances, is poorly known for the Earth's largest habitats: the abyssal plains. A unique 15-yr time series of climate, productivity, particulate flux, and abundance of primary consumers (primarily echinoderms) and secondary consumers (fish) was examined to elucidate the response of trophic levels to temporal variation in one another. Towed camera sled deployments in the abyssal northeast Pacific (4100 m water depth) showed that annual mean numbers of the dominant fish genus (Coryphaenoides spp.) more than doubled over the period 1989-2004. Coryphaenoides spp. abundance was significantly correlated with total abundance of mobile epibenthic megafauna (echinoderms), with changes in fish abundance lagging behind changes in the echinoderms. Direct correlations between surface climate and fish abundances, and particulate organic carbon (POC) flux and fish abundances, were insignificant, which may be related to the varied response of the potential prey taxa to climate and POC flux. This study provides a rare opportunity to study the long-term dynamics of an unexploited marine fish population and suggests a dominant role for bottom-up control in this system.

Animals↗

PubMed2006

Consumer-resource body-size relationships in natural food webs.

It has been suggested that differences in body size between consumer and resource species may have important implications for interaction strengths, population dynamics, and eventually food web structure, function, and evolution. Still, the general distribution of consumer-'resource body-size ratios in real ecosystems, and whether they vary systematically among habitats or broad taxonomic groups, is poorly understood. Using a unique global database on consumer and resource body sizes, we show that the mean body-size ratios of aquatic herbivorous and detritivorous consumers are several orders of magnitude larger than those of carnivorous predators. Carnivorous predator-prey body-size ratios vary across different habitats and predator and prey types (invertebrates, ectotherm, and endotherm vertebrates). Predator-prey body-size ratios are on average significantly higher (1) in freshwater habitats than in marine or terrestrial habitats, (2) for vertebrate than for invertebrate predators, and (3) for invertebrate than for ectotherm vertebrate prey. If recent studies that relate body-size ratios to interaction strengths are general, our results suggest that mean consumer-resource interaction strengths may vary systematically across different habitat categories and consumer types.

Animals↗

PubMed2005

Soy isoflavones modulate the expression of BAD and neuron-specific beta III tubulin in male rat brain.

Isoflavones, the most abundant phytoestrogens in soy foods, are structurally similar to 17beta-estradiol. There is evidence that soy isoflavones influence neuronal apoptosis or proliferation in vitro and in vivo. However, little research has been done to investigate the effects of soy isoflavones on markers of neuronal apoptosis and survival in vivo. We examined brain BAD (a proapoptotic member of Bcl-2 protein family) and neuron-specific beta III tubulin (an early marker of neuronal differentiation/survival) levels in male rats fed either a standard chow rich of soy isoflavones (Phyto-600) or one free of soy isoflavones (Phyto-free) life-long (from conception until time tissue collected). Among five brain regions, the expression of BAD was highest in medial basal hypothalamus (MBH); the next highest in hippocampus; moderate in amygdala and frontal cortex; and lowest in cerebellum in Phyto-free fed animals. In animals on Phyto-600 diet, the levels of BAD were significantly decreased in frontal cortex and MBH; but significantly increased in the amygdala. The expression of beta III tubulin was highest in frontal cortex; moderate in amygdala, hippocampus and MBH; and lowest in cerebellum in the Phyto-free group. In rats fed with the Phyto-600 diet, levels of beta III tubulin were significantly increased in amygdala, frontal cortex, hippocampus and MBH compared to Phyto-free values. In summary, these findings provide evidence for the neuroprotective potential of soy isoflavones in the amygdala, frontal cortex, hippocampus and MBH. This implies that consumption of soy isoflavones may be beneficial on learning and memory, anxiety-related behaviors, and recovery from trauma.

Animals↗

PubMed1992

Significance of iron bioavailability for iron recommendations.

Recently, recommended dietary allowances (RDA) have been formulated by the Dutch Nutrition Council for minerals and trace elements, including iron (Fe). For some population groups in the Netherlands, it is questionable whether they easily meet the Fe recommendation. An increase in Fe intake is not always possible, but "manipulation" of Fe bioavailability ultimately may result in better Fe utilization. Various factors are known to affect Fe bioavailability. Generally, much attention is paid to diet-related factors, such as inhibitors and enhancers of Fe availability for absorption. Factors such as pH, oxidation potential, structure of food, and time of digestion often are overlooked. Of the diet-related factors, heme Fe and ascorbic acid have a strong positive effect on Fe availability for absorption, whereas oxalate and polyphenols seem to be strong inhibitors of Fe availability. Because of the many interactions that may occur simultaneously, the net effect of the various combined factors in a meal is not equal to the sum of the individual factors.

Biological Availability↗

PubMed2005

Life cycle strategy of Hysterothylacium aduncum to become the most abundant anisakid fish nematode in the North Sea.

The present study demonstrates the influence of physical systems (mixed and stratified waters) on the occurrence and distribution of the anisakid nematode Hysterothylacium aduncum in commercially important gadiform fish species from the central and northern North Sea. Stratified waters are essential in structuring marine food webs and are therefore also important for the transfer of fish parasites to their host species. During two research cruises in 2001, 308 haddocks (Melanogrammus aeglefinus) and 203 whitings (Merlangius merlangus) were caught in the central and northern North Sea and were examined for anisakid nematode parasites and food composition. Additionally, the most abundant pelagic invertebrates, hyperiid amphipods, of the investigated area were sampled and examined with regard to their parasite infestation rates. The influence of stratified waters on the infestation of the gadiform fish species by H. aduncum was shown by ecological and parasitological investigations. In stratified areas haddocks and whitings feed specifically and invariably on pelagic hyperiids. The number of ingested hyperiids in these areas was in both fish species correlated with infestation rates of H. aduncum. Therefore, hyperiids were identified as the obligatory intermediated host of H. aduncum, since these crustaceans carried high numbers of nematode larvae in their haemocoel. The results of the present study demonstrate that haddocks and whitings from the stratified waters are highly parasitised, both in terms of the numbers of individuals of larval and adult stages of H. aduncum.

Adaptation, Physiological↗

PubMed2006

Dietary calcium and bone mineral density in premenopausal women with systemic lupus erythematosus.

The primary objective of this study was to determine the relationship between dietary calcium intake and bone mineral density (BMD) in premenopausal women with systemic lupus erythematosus (SLE) on corticosteroids (CS). The secondary aim was to identify other risk factors for osteoporosis in these patients. A cross-sectional sample of patients attending the SLE Clinic at a teaching hospital was recruited. BMD was measured using dual-energy X-ray absorptiometry. Daily dietary calcium intake was assessed using a structured validated food frequency questionnaire, in which patients were asked to estimate their food intake based on their recent 2-month dietary habits. Sixty subjects were recruited with a mean age of 33.70+/-8.46 years. The median duration of CS use was 5.5 years (range 0.08-24). The median cumulative dose of steroids was 17.21 g (range 0.16-91.37). The median daily dietary calcium intake was 483 mg (range 78-2101). There was no significant correlation between calcium intake and BMD, even after correcting for CS use. There were also no correlations between BMD and the duration of SLE, cumulative CS use, duration of CS use, smoking, alcohol intake, and SLE disease activity index score. Twenty-eight (46.7%) patients had normal BMD, 28 (46.7%) had osteopenia, and four (6.6%) had osteoporosis. Duration of SLE significantly correlated with cumulative CS dosage. In conclusion, 6.7% of these Asian premenopausal SLE women had osteoporosis and only 46.7% had normal BMD. Daily dietary calcium intake did not correlate with BMD.

Absorptiometry, Photon↗

PubMed1990

Effects of anaesthesia of human oral structures on masticatory performance and food particle size distribution.

Ten persons with intact dentitions performed a series of 6 masticatory tests, employing 5, 10, 20, 40, 80 and 160 strokes to chew standard quantities of peanuts on their preferred chewing side for each of three test conditions: (1) before anaesthesia: (2) after maxillary anaesthesia; and, (3) after maxillary and mandibular anaesthesia (unilateral). A seventh test employing 20 strokes was also repeated on the non-anaesthetized contralateral side. The chewed food was sieved through 5, 10, 20, 40, 80 and 100 mesh screens. The percentage of the ratio of the volume of peanuts that passed through the sieve and the total volume of recovered food provided the performance score for the given sieve. The performance scores increased significantly with the number of stokes and dropped markedly after anaesthesia. The maximum reduction of 19.6% in the mean masticatory performance and 46% in the mean masticatory efficiency occurred after unilateral anaesthesia at 10 mesh particle size in the 20-stroke test. An average of 40 strokes was required after unilateral anaesthesia to achieve almost the same performance achieved with 20 strokes before anaesthesia. The regression slopes, derived from the 5, 10 and 20 mesh particle distributions showed that coarse particles were ground more rapidly than fine particles before anaesthesia. This preferential comminution became less evident after maxillary anaesthesia and was least evident after unilateral anaesthesia. The regression slope for the control peaked at 10 strokes as compared to 20 strokes after unilateral anaesthesia. Thus peripheral sensory impairment affects masticatory efficiency in dentate persons.

Adult↗

PubMed1993

Assessment of disturbance on soil ecosystems.

Given the complexity of ecosystems, the high degree of interactions among species, and the numerous responses of systems to disturbance, it is unlikely that simple assays developed for other systems would adequately serve to monitor soil systems. Apart from the questionable applicability of non-soil techniques, protocols to monitor soil biota in a standardized manner have not been developed. To monitor soils, a five-phase plan is proposed. The plan involves: (1) a thorough survey of the systems biota; (2) laboratory toxicity trials on indicator species (Folsomia candida); (3) field tests on indicator processes (litter decomposition); (4) field monitoring of indicator functional groups (nematodes); (5) the development of standardized statistical techniques and simulation models. Each phase of the plan was designed to capture a different aspect of food web structure and function.

Animals↗

PubMed2000

Are there real differences among aquatic and terrestrial food webs?

Recently, aquatic and terrestrial ecologists have put forward several hypotheses regarding similarities and differences in food-web structure and function among these ecosystem types. Although many of these hypotheses explore why strong top-down effects and trophic cascades might be less common in terrestrial than in aquatic ecosystems, there is little theoretical or empirical evidence available to support or refute these hypotheses. Many unanswered questions remain about potential differences across ecosystem types: progress will require empirical studies designed within a broader context that allows for more direct comparisons.

Journal Article↗

PubMed2001

Production of atmospheric sulfur by oceanic plankton: biogeochemical, ecological and evolutionary links.

Biological production of the volatile compound dimethylsulfide in the ocean is the main natural source of tropospheric sulfur on a global scale, with important consequences for the radiative balance of the Earth. In the late 1980s, a Gaian feedback link between marine phytoplankton and climate through the release of atmospheric sulfur was hypothesized. However, the idea of microalgae producing a substance that could regulate climate has been criticized on the basis of its evolutionary feasibility. Recent advances have shown that volatile sulfur is a result of ecological interactions and transformation processes through planktonic food webs. It is, therefore, not only phytoplankton biomass, taxonomy or activity, but also food-web structure and dynamics that drive the oceanic production of atmospheric sulfur. Accordingly, the viewpoint on the ecological and evolutionary basis of this amazing marine biota-atmosphere link is changing.

Journal Article↗

PubMed2000

Summary of a systematic review on oral nutritional supplement use in the community.

Despite a marked increase in the prescription of oral nutritional supplements (ONS) in the community (Department of Health, 1991-7), there is still uncertainty about the value of their use in patients with different diseases. To answer questions about the effects on ONS on body weight and structure, spontaneous food intake and body function, a critical systematic review was undertaken (Stratton & Elia, 1999a). Eighty-four trials were reviewed (forty-five randomized, thirty-nine non-randomized: 2,570 patients; diagnoses including chronic obstructive pulmonary disease, Crohn's disease, cystic fibrosis, human immunodeficiency virus and acquired immune deficiency syndrome and cancer). Most studies (83 %) were conducted in patients living at home. The supplements were typically mixed macronutrients in liquid form, providing < 0.42-10.5 MJ/d for 1 week-2 years. The studies reviewed in patients with predominantly chronic conditions living in the community suggested that: (1) ONS produce demonstrable clinical (including functional) benefits, but the nature and extent of these benefits varies with the underlying chronic condition; (2) ONS increase total energy intake with > 50 % of the energy from ONS typically additional to that from habitual food intake; (3) improvements in body weight, total energy intake and body function following ONS appear to occur more frequently in individuals with a BMI < 20 kg/m2 than in those with a BMI > 20 kg/m2.

Appetite↗