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Showing papers on "Productivity (ecology) published in 2013"


Journal ArticleDOI
TL;DR: The hypothesis that the long-term impacts of anthropogenic drivers of environmental change on ecosystem functioning can strongly depend on how such drivers gradually decrease biodiversity and restructure communities is supported.
Abstract: Anthropogenic drivers of environmental change often have multiple effects, including changes in biodiversity, species composition, and ecosystem functioning. It remains unknown whether such shifts in biodiversity and species composition may, themselves, be major contributors to the total, long-term impacts of anthropogenic drivers on ecosystem functioning. Moreover, although numerous experiments have shown that random losses of species impact the functioning of ecosystems, human-caused losses of biodiversity are rarely random. Here we use results from long-term grassland field experiments to test for direct effects of chronic nutrient enrichment on ecosystem productivity, and for indirect effects of enrichment on productivity mediated by resultant species losses. We found that ecosystem productivity decreased through time most in plots that lost the most species. Chronic nitrogen addition also led to the nonrandom loss of initially dominant native perennial C4 grasses. This loss of dominant plant species was associated with twice as great a loss of productivity per lost species than occurred with random species loss in a nearby biodiversity experiment. Thus, although chronic nitrogen enrichment initially increased productivity, it also led to loss of plant species, including initially dominant species, which then caused substantial diminishing returns from nitrogen fertilization. In contrast, elevated CO2 did not decrease grassland plant diversity, and it consistently promoted productivity over time. Our results support the hypothesis that the long-term impacts of anthropogenic drivers of environmental change on ecosystem functioning can strongly depend on how such drivers gradually decrease biodiversity and restructure communities.

511 citations


Journal ArticleDOI
TL;DR: In this paper, the intermediate fire-productivity model has been validated across all world ecosystems, including Antarctica, and it has been suggested that on a global scale, fire activity changes along the productivity/aridity gradient following a humped relationship.
Abstract: Aim It has been suggested that on a global scale, fire activity changes along the productivity/aridity gradient following a humped relationship, i.e. the intermediate fire–productivity hypothesis. This relation should be driven by differing relative roles of the main fire drivers (weather and fuel) along the productivity gradient. However, the full intermediate fire–productivity model across all world ecosystems remains to be validated. Location The entire globe, excluding Antarctica. Methods To test the intermediate fire–productivity hypothesis, we use the world ecoregions as a spatial unit and, for each ecoregion, we compiled remotely sensed fire activity, climate, biomass and productivity information. The regression coefficient between monthly MODIS fire activity and monthly maximum temperature in each ecoregion was considered an indicator of the sensitivity of fire to high temperatures in the ecoregion. We used linear and generalized additive models to test for the linear and humped relationships. Results Fire occurs in most ecoregions. Fire activity peaked in tropical grasslands and savannas, and significantly decreased towards the extremes of the productivity gradient. Both the sensitivity of fire to high temperatures and above-ground biomass increased monotonically with productivity. In other words, fire activity in low-productivity ecosystems is not driven by warm periods and is limited by low biomass; in contrast, in high-productivity ecosystems fire is more sensitive to high temperatures, and in these ecosystems, the available biomass for fires is high. Main conclusion The results support the intermediate fire–productivity model on a global scale and suggest that climatic warming may affect fire activity differently depending on the productivity of the region. Fire regimes in productive regions are vulnerable to warming (drought-driven fire regime changes), while in low-productivity regions fire activity is more vulnerable to fuel changes (fuel-driven fire regime changes).

273 citations


Journal ArticleDOI
TL;DR: This work focuses on forests, which represent a majority of global biomass, productivity and biodiversity, and investigates the relationship between species richness and ecosystem function as measured by productivity or biomass.
Abstract: 1. The relationship between species richness and ecosystem function, as measured by productivity or biomass, is of long-standing theoretical and practical interest in ecology. This is especially true for forests, which represent a majority of global biomass, productivity and biodiversity.

256 citations


Journal ArticleDOI
01 Apr 2013-Ecology
TL;DR: The results suggest the productivity of diverse plant communities was partly dependent on belowground plant interactions that caused roots to be distributed more deeply in soil.
Abstract: The relationship between plant diversity and productivity in grasslands could depend, partly, on how diversity affects vertical distributions of root biomass in soil; yet, no prior study has evaluated the links among diversity, root depth distributions, and productivity in a long-term experiment. We use data from a 12-year experiment to ask how plant species richness and composition influenced both observed and expected root depth distributions of plant communities. Expected root depth distributions were based on the abundance of species in each community and two traits of species that were measured in monocultures: root depth distributions and root to shoot ratios. The observed proportion of deep root biomass increased more than expected with species richness and was positively correlated with aboveground productivity. Indeed, the proportion of deep root biomass explained variation in productivity even after accounting for legume presence/abundance, and greater nitrogen availability in diverse plots. Diverse plots had root depth distributions that were twice as deep as expected from their species composition and corresponding monoculture traits, partly due to interactions between C4 grasses and legumes. These results suggest the productivity of diverse plant communities was partly dependent on belowground plant interactions that caused roots to be distributed more deeply in soil.

240 citations


Journal ArticleDOI
TL;DR: Wang et al. as mentioned in this paper suggested that a phytoplankton-dominated autotrophic lake gradually shifts to a turbid-water, algae-dominated ecosystem.
Abstract: China is a country with many lakes, about one-third of which are freshwater mainly distributed in the middle and lower reaches of the Yangtze River. Currently most of the lakes are mesotrophic or eutrophic. Lake eutrophication has become one of the major ecological and environmental problems faced by lakes in China and can lead to a series of abnormal ecosystem responses, including extinction of submerged plants, frequent occurrence of cyanobacterial blooms, increased microbial biomass and productivity, decreased biodiversity, accelerated cycles, and a change in the efficient use of nutrients. With development of eutrophication, the whole lake ecosystem suffers decreased biodiversity, simplification of biotic community structure, instability of the ecosystem, and ultimately the clear-water, macrophyte-dominated ecosystem gradually shifts to a turbid-water, algae-dominated ecosystem. This ecosystem succession mechanism is speculated to be caused by different nutrient utilization efficiencies of macrophytes and phytoplankton. The ultimate ecosystem succession trend of seriously eutrophic lakes is that a phytoplankton-dominated autotrophic lake shifts to a heterotrophic lake dominated by micro-organisms, protozoans.

229 citations


Journal ArticleDOI
02 May 2013-PLOS ONE
TL;DR: It is proposed that globally sea floor elevation has no effect on deep sea biomass; pelagic plus benthic biomass is constant within a given surface productivity regime.
Abstract: In contrast to generally sparse biological communities in open-ocean settings, seamounts and ridges are perceived as areas of elevated productivity and biodiversity capable of supporting commercial fisheries. We investigated the origin of this apparent biological enhancement over a segment of the North Mid-Atlantic Ridge (MAR) using sonar, corers, trawls, traps, and a remotely operated vehicle to survey habitat, biomass, and biodiversity. Satellite remote sensing provided information on flow patterns, thermal fronts, and primary production, while sediment traps measured export flux during 2007–2010. The MAR, 3,704,404 km2 in area, accounts for 44.7% lower bathyal habitat (800–3500 m depth) in the North Atlantic and is dominated by fine soft sediment substrate (95% of area) on a series of flat terraces with intervening slopes either side of the ridge axis contributing to habitat heterogeneity. The MAR fauna comprises mainly species known from continental margins with no evidence of greater biodiversity. Primary production and export flux over the MAR were not enhanced compared with a nearby reference station over the Porcupine Abyssal Plain. Biomasses of benthic macrofauna and megafauna were similar to global averages at the same depths totalling an estimated 258.9 kt C over the entire lower bathyal north MAR. A hypothetical flat plain at 3500 m depth in place of the MAR would contain 85.6 kt C, implying an increase of 173.3 kt C attributable to the presence of the Ridge. This is approximately equal to 167 kt C of estimated pelagic biomass displaced by the volume of the MAR. There is no enhancement of biological productivity over the MAR; oceanic bathypelagic species are replaced by benthic fauna otherwise unable to survive in the mid ocean. We propose that globally sea floor elevation has no effect on deep sea biomass; pelagic plus benthic biomass is constant within a given surface productivity regime.

199 citations


Journal ArticleDOI
TL;DR: The results provide some of the first direct evidence for below-ground species complementarity in heterogeneous natural forests, by demonstrating that tree species evenness increases fine root productivity by filling/exploiting the soil environment more completely in space and time.
Abstract: Summary 1. Although fine roots (< 2 mm in diameter) account for a major share of the production of terrestrial ecosystems, diversity effects on fine root productivity and their mechanisms remain unclear. 2. We hypothesized that: (i) fine root productivity increases with tree species diversity, (ii) higher fine root productivity is a result of greater soil volume filling due to species-specific patterns of root placement and proliferation, and (iii) differences in fine root productivity and soil volume filling associated with tree species diversity are more pronounced in summer when plants are physiologically active and demand for water and nutrients is at its greatest. 3. We investigated the effects of tree species diversity on fine root productivity and soil volume filling of boreal forest stands that have grown naturally for 85 years on similar sites. 4. Annual fine root production was 19–83% higher in evenly mixed- than single-species-dominated stands, and increased with tree species evenness, but not tree species richness. Fine root biomass was higher in evenly mixed- than single-species-dominated stands in summer months, but not in spring or fall. Higher fine root productivity in evenly mixed- than single-species-dominated stands was realized by filling more soil volume horizontally and vertically in the forest floor in the mixtures of deep- and shallow-rooted species vs. the deeper mineral soil in the mixtures of deeprooted species. 5. Synthesis. Our results provide some of the first direct evidence for below-ground species complementarity in heterogeneous natural forests, by demonstrating that tree species evenness increases fine root productivity by filling/exploiting the soil environment more completely in space and time, driven by differences in the inherent rooting traits of the component species and variations of root growth within species.

181 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that future CO2 emissions from lakes will be strongly related to productivity in the lake catchment, and that CO2 in lakes may be delivered directly via inflowing streams.
Abstract: Most lakes are net sources of CO2; conventionally the CO2 in lake waters is attributed to in-lake oxidation of terrestrially-produced dissolved organic carbon. Now research indicates that CO2 in lakes may be delivered directly via inflowing streams. These findings suggest that future CO2 emissions from lakes will be strongly related to productivity in the lake catchment.

171 citations


Journal ArticleDOI
TL;DR: In this paper, the authors analyzed nearly three decades (1982?2008) of observational records and derived products, including satellite microwave and optical imagery as well as upscaled ecosystem flux observations, to better understand how shifts in seasonality impact hydrology and productivity in the North American boreal forests.
Abstract: In the northern high latitudes, alternative hypotheses with regards to how warming-related shifts in seasonality influence ecosystem productivity exist. Increased plant growth associated with a longer growing season may enhance ecosystem productivity, but shifts to earlier springs may also negatively influence soil moisture status and productivity during the peak of the growing season. Here, we analyzed nearly three decades (1982?2008) of observational records and derived products, including satellite microwave and optical imagery as well as upscaled ecosystem flux observations, to better understand how shifts in seasonality impact hydrology and productivity in the North American boreal forests. We identified a dominant adverse influence of earlier springs on peak summer forest greenness, actual evapotranspiration and productivity at interannual time scales across the drier western and central sections of the North American boreal forests. In the vast regions where this spring onset mechanism operates, ecosystem productivity gains from earlier springs during the early portion of the growing season are effectively cancelled through corresponding losses in the later portion. Our results also indicate that recent decadal shifts towards earlier springs and associated drying in the midst of the growing season over western North American boreal forests may have contributed to the reported declines in summer productivity and increases in tree mortality and fire activity. With projections of accelerated northern high-latitude warming and associated shifts to earlier springs, persistent soil moisture deficits in peak summer may be an effective mechanism for regional-scale boreal forest dieback through their strong influence on productivity, tree mortality and disturbance dynamics.

171 citations


Journal ArticleDOI
TL;DR: In this article, a CO 2 perturbation study in Kongsfjorden on the west coast of Spitsbergen (Norway), in the framework of the EU-funded project EPOCA, was followed in nine mesocosms, manipulated for CO 2 levels ranging from about 185 to 1420 μatm.
Abstract: Ocean acidification and carbonation, driven by anthropogenic emissions of carbon dioxide (CO 2 ), have been shown to affect a variety of marine organisms and are likely to change ecosystem functioning. High latitudes, especially the Arctic, will be the first to encounter profound changes in carbonate chemistry speciation at a large scale, namely the under-saturation of surface waters with respect to aragonite, a calcium carbonate polymorph produced by several organisms in this region. During a CO 2 perturbation study in Kongsfjorden on the west coast of Spitsbergen (Norway), in the framework of the EU-funded project EPOCA, the temporal dynamics of a plankton bloom was followed in nine mesocosms, manipulated for CO 2 levels ranging initially from about 185 to 1420 μatm. Dissolved inorganic nutrients were added halfway through the experiment. Autotrophic biomass, as identified by chlorophyll a standing stocks (Chl a ), peaked three times in all mesocosms. However, while absolute Chl a concentrations were similar in all mesocosms during the first phase of the experiment, higher autotrophic biomass was measured as high in comparison to low CO 2 during the second phase, right after dissolved inorganic nutrient addition. This trend then reversed in the third phase. There were several statistically significant CO 2 effects on a variety of parameters measured in certain phases, such as nutrient utilization, standing stocks of particulate organic matter, and phytoplankton species composition. Interestingly, CO 2 effects developed slowly but steadily, becoming more and more statistically significant with time. The observed CO 2 -related shifts in nutrient flow into different phytoplankton groups (mainly dinoflagellates, prasinophytes and haptophytes) could have consequences for future organic matter flow to higher trophic levels and export production, with consequences for ecosystem productivity and atmospheric CO 2 .

157 citations


Journal ArticleDOI
TL;DR: The importance of autumn phenology in controlling interannual variability of forest net ecosystem productivity and to derive new phenological metrics to explain the interannually variability of NEP are investigated.
Abstract: Aim To investigate the importance of autumn phenology in controlling interannual variability of forest net ecosystem productivity (NEP) and to derive new phenological metrics to explain the interannual variability of NEP. Location North America and Europe.

Journal ArticleDOI
TL;DR: In this paper, the authors used the Normalized Difference Vegetation Index (NDVI) from both field and satellite measurements as an indicator of vegetation phenology and productivity, and monitored spatial and temporal patterns of vegetation growth for a coastal wet sedge tundra site near Barrow, Alaska.

Journal ArticleDOI
TL;DR: Results suggest that poor trophic conditions, likely due to climate-driven environmental factors, and warmer ocean temperatures throughout their marine habitat area are constraining the productivity and recovery of North American Atlantic salmon populations.
Abstract: North American Atlantic salmon (Salmo salar) populations experienced substantial declines in the early 1990s, and many populations have persisted at low abundances in recent years. Abundance and productivity declined in a coherent manner across major regions of North America, and this coherence points toward a potential shift in marine survivorship, rather than local, river-specific factors. The major declines in Atlantic salmon populations occurred against a backdrop of physical and biological shifts in Northwest Atlantic ecosystems. Analyses of changes in climate, physical, and lower trophic level biological factors provide substantial evidence that climate conditions directly and indirectly influence the abundance and productivity of North American Atlantic salmon populations. A major decline in salmon abundance after 1990 was preceded by a series of changes across multiple levels of the ecosystem, and a subsequent population change in 1997, primarily related to salmon productivity, followed an unusually low NAO event. Pairwise correlations further demonstrate that climate and physical conditions are associated with changes in plankton communities and prey availability, which are ultimately linked to Atlantic salmon populations. Results suggest that poor trophic conditions, likely due to climate-driven environmental factors, and warmer ocean temperatures throughout their marine habitat area are constraining the productivity and recovery of North American Atlantic salmon populations.

Journal ArticleDOI
TL;DR: In this article, a 5-yr livestock exclosure experiment along the southfacing slope of the Nyaiqentanglha Mountains, central Tibetan Plateau was conducted to test the hypotheses that for alpine grasslands along a large altitudinal gradient in semi-arid regions, plant growth is mainly limited by drought at low altitudes but by low temperature at high altitudes, resulting in aunimodal pattern of biomass and productivity associated with an optimal combination of temperature and precipitation.
Abstract: Questions: How can we understand the limitations to plant growth at high altitudes? Our aimwas to test the hypotheses that for alpine grasslands along a large altitudinal gradient in semi-arid regions, plant growth is mainly limited by drought at low altitudes but by low temperature at high altitudes, resulting in a unimodal pattern of biomass and productivity associated with an optimal combination of temperature and precipitation. Such knowledge is important to understanding the response of alpine ecosystems to climate change. Location: We conducted a 5-yr livestock exclosure experiment along the southfacing slope of the Nyaiqentanglha Mountains, central Tibetan Plateau. Methods: We measured above- and below-ground biomass, species richness, leaf d13C and water potential, and related climate and soil variables across 42 fenced and unfenced quadrats near seven HOBO weather stations along the slope. The vegetation changed from alpine steppe-meadow at 4390–4500 m to alpinemeadow at 4600–5210 m. Results: Total above- and below-ground biomass across fenced and unfenced quadrats increased with increasing altitude up to 4950–5100 m, and then decreased above 5100 m. Altitudinal trends in leaf d13C and water potential of dominant species also showed a unimodal pattern corresponding to that of vegetation biomass. Total above- and below-ground biomass as well as sedge above-ground biomass all showed a quadratic relationship with mean temperatures and the ratio of growing season precipitation (GSP) to 5 °C accumulated temperature (AccT; R2 = 0.830.88, P < 0.001). In general, above- and below-ground biomass increased with increasing water availability when the GSP/AccT ratio was lower than the threshold level of 0.80–0.84, but decreased when the GSP/AccT ratio was higher than this threshold level. No significant relationship was found between residuals of above-ground biomass and species richness after removing the effects of climate factors on both stand variables. Conclusions: The results support our hypotheses, further suggesting a threshold ofwater limitation that is consistent with themodel prediction over the Tibetan Plateau. Species richness per se appears to weakly affect community-level productivity. The response of alpine grasslands to climate warming may vary with altitude because of altitudinal shifts in factors limiting plant growth. Keywords: Alpine grassland; Biomass; Functional groups; Leaf water potential; Net primary productivity; Plant–climate interactions; Species richness

Journal ArticleDOI
TL;DR: In this paper, the authors assessed annual aboveground net primary productivity (ANPP) and its relation to climatic factors and [CO2] in a neotropical rainforest through 1997-2009.
Abstract: [1] A directional change in tropical-forest productivity, a large component in the global carbon budget, would affect the rate of increase in atmospheric carbon dioxide ([CO2]). One current hypothesis is that “CO2 fertilization” has been increasing tropical forest productivity. Some lines of evidence instead suggest climate-driven productivity declines. Relevant direct field observations remain extremely limited for this biome. Using a unique long-term record of annual field measurements, we assessed annual aboveground net primary productivity (ANPP) and its relation to climatic factors and [CO2] in a neotropical rainforest through 1997–2009. Over this 12 year period, annual productivity did not increase, as would be expected with a dominant CO2 fertilization effect. Instead, the negative responses of ANPP components to climatic stress far exceeded the small positive responses associated with increasing [CO2]. Annual aboveground biomass production was well explained (73%) by the independent negative effects of increasing minimum temperatures and greater dry-season water stress. The long-term records enable a first field-based estimate of the [CO2] response of tropical forest ANPP: 5.24 g m−2 yr−1 yr−1 (the summed [CO2]-associated increases in two of the four production components; the largest component, leaf litterfall, showed no [CO2] association). If confirmed by longer data series, such a small response from a fertile tropical rainforest would indicate that current global models overestimate the benefits from CO2 fertilization for this biome, where most forests' poorer nutrient status more strongly constrains productivity responses to increasing [CO2]. Given the rapidly intensifying warming across tropical regions, tropical forest productivity could sharply decline through coming decades.

Journal ArticleDOI
TL;DR: The present study examines the possibility of enhancement of fatty acid productivity of Scenedesmus obliquus by modifications of the culture medium composition by studying the effect of different concentrations of sodium bicarbonate, salinity, potassium nitrate, glycerol and sugarcane molasses on the enhancement of biomass and esterified fatty acids production.
Abstract: Nowadays, microalgae are discussed as a promising feedstock for biodiesel production. The present study examines the possibility of enhancement of fatty acid productivity of Scenedesmus obliquus by modifications of the culture medium composition. The effect of different concentrations of sodium bicarbonate, salinity, potassium nitrate, glycerol and sugarcane molasses on the enhancement of biomass and esterified fatty acids production was studied. NaHCO3 caused an increase in the biomass productivity at low concentrations (0.5 g L−1), while negatively affected fatty acid productivity at all tested concentrations. Increase of salinity enhanced both biomass and fatty acid productivity. The optimum NaCl concentration and sea water ratio were 0.94 g L−1 and 25 % which resulted in 56 and 39 % increase in fatty acid productivity, respectively. Nitrogen deficiency showed increase in fatty acid content by 54 % over control but fatty acid productivity was decreased as a result of growth inhibition. Nitrogen-free cultures and cultures treated with −50 % concentrations of KNO3 showed 96 and 42 % decrease in EFA productivity, respectively, as compared with the control. Addition of 0.05 and 0.1 M of glycerol increased the biomass productivity by 6 and 5 %, respectively but showed no significant effect on fatty acid productivity as a result of decrease in fatty acid content. Finally, usage of sugarcane molasses stimulated both biomass and fatty acid content. The increase in fatty acid productivity was 32, 65 and 73 % above the control level at 1, 3 and 5 g L−1 of sugarcane molasses, respectively.

Book ChapterDOI
16 Mar 2013
TL;DR: Macnae et al. as discussed by the authors investigated the role of mangroves in supporting secondary productivity in coastal waters and found that they are a source of organic detritus yet a nutrient sink, contributing to the confusion of their role in coastal processes.
Abstract: Most of the tropical coastline between 25° N and 25° S latitude is vegetated by forested wetlands called mangroves (McGill, 1958). These plant communities have received considerable botanical investigation because of their unique taxonomy and ovivipary (Tomlinson, 1986), and the diverse fauna that inhabit these coastal areas (Macnae, 1968;Chapman, 1976). However, the ecology of mangroves is poorly understood, particularly the significance of these ecosystems to the productivity and nutrient cycling of estuarine and adjacent coastal waters. It has been suggested that the high fishery yields of coastal tropical waters are due to the presence of these communities (Macnae, 1974; Turner, 1977; Jothy, 1984), yet there is no evidence of a cause and effect relationship for mangroves and fisheries (Macnae, 1974). Thus the function of these wetlands in supporting secondary productivity continues to be a complex issue. Mangroves may also influence the primary productivity of coastal waters by controlling the fate of dissolved nutrients and suspended sediments. Mangroves are considered a source of organic detritus yet a nutrient sink, contributing to the confusion of their role in coastal processes.

Journal ArticleDOI
TL;DR: The study revealed that at the initial part of a productivity gradient, stress is likely responsible for low species richness, thus the litter effect is one of the major mechanisms structuring grassland diversity.
Abstract: Question Explaining the biomass–species richness relationship is key to understanding vegetation dynamics. Several possible mechanisms have been suggested, but complex analysis of plant strategies, major biomass and species richness components along a long productivity gradient is still lacking. We provide a detailed analysis of the relationship between major biomass components (total above-ground biomass, green biomass and litter), plant strategies and species richness along a long gradient of alkali and loess grasslands in a steppe landscape in Central Europe. Location Hortobagy, Great Hungarian Plain, East Hungary. Methods Above-ground biomass of characteristic alkali and loess grassland stands was sampled along a gradient of increasing productivity. In each grassland stand, a 25-m2 sample site was randomly selected. Within each site, ten above-ground biomass samples (20 × 20 cm) were collected randomly in June 2009, at the peak of biomass production. We classified all species into mixed C-S-R strategy types. To obtain correlations between various biomass and species richness data, Spearman rank correlation was used. The relationship between plant strategies and species composition were displayed with a DCA ordination. Results The frequently detected humped-back relationship was valid for the relation of total biomass and species richness. With increasing amount of total biomass, we detected an increasing proportion of competitors, and a decreasing proportion of stress tolerators in green biomass. A low proportion of ruderals was detected at both low and high biomass levels. Species richness was affected positively by litter at low litter scores, but there was a negative litter effect from much lower scores than detected previously (from 400 g·m−2). There was a positive relationship between green biomass production and species richness. Conclusions The study revealed that at the initial part of a productivity gradient, stress is likely responsible for low species richness. Our results show that litter can shape changes in species richness along the whole biomass gradient, thus the litter effect is one of the major mechanisms structuring grassland diversity.

Journal ArticleDOI
TL;DR: It is suggested that a significant amount of energy moves through trematode parasites in freshwater pond ecosystems, and that their contributions to ecosystem energetics may exceed those of many free-living taxa known to play key roles in structuring aquatic communities.
Abstract: Summary Ecologists often measure the biomass and productivity of organisms to understand the importance of populations and communities in the flow of energy through ecosystems. Despite the central role of such studies in the advancement of freshwater ecology, there has been little effort to incorporate parasites into studies of freshwater energy flow. This omission is particularly important considering the roles that parasites sometimes play in shaping community structure and ecosystem processes. Using quantitative surveys and dissections of over 1600 aquatic invertebrate and amphibian hosts, we calculated the ecosystem-level biomass and productivity of trematode parasites alongside the biomass of free-living aquatic organisms in three freshwater ponds in California, USA. Snails and amphibian larvae, which are both important intermediate trematode hosts, dominated the dry biomass of free-living organisms across ponds (snails = 3·2 g m−2; amphibians = 3·1 g m−2). An average of 33·5% of mature snails were infected with one of six trematode taxa, amounting to a density of 13 infected snails m−2 of pond substrate. Between 18% and 33% of the combined host and parasite biomass within each infected snail consisted of larval trematode tissue, which collectively accounted for 87% of the total trematode biomass within the three ponds. Mid-summer trematode dry biomass averaged 0·10 g m−2, which was equal to or greater than that of the most abundant insect orders (coleoptera = 0·10 g m−2, odonata = 0·08 g m−2, hemiptera = 0·07 g m−2 and ephemeroptera = 0·03 g m−2). On average, each trematode taxon produced between 14 and 1660 free-swimming larvae (cercariae) infected snail−1 24 h−1 in mid-summer. Given that infected snails release cercariae for 3–4 months a year, the pond trematode communities produced an average of 153 mg m−2 yr−1 of dry cercarial biomass (range = 70–220 mg m−2 yr−1). Our results suggest that a significant amount of energy moves through trematode parasites in freshwater pond ecosystems, and that their contributions to ecosystem energetics may exceed those of many free-living taxa known to play key roles in structuring aquatic communities.

Journal ArticleDOI
TL;DR: The combined improvements that recycling triggered in biomass productivity, harvest efficiency and energy content enhanced the harvested biomass energy yield by 66% and confirmed, for the first time in the literature, that species control is possible for similarly sized co-occurring algal colonies in outdoor HRAP by algal recycling.

Journal ArticleDOI
TL;DR: This article examined impacts of climate treatments on above-ground biomass and community structure for 4-yr, and investigated the relationship between biomass production, species diversity and three key functional traits: specific leaf area, leaf dry matter content and leaf N content.
Abstract: Questions How does above-ground grassland biomass production respond to change in multiple climate drivers over a 4-yr period? Can climate-induced patterns of biomass response be explained by shifts in plant community structure? Does sustained climate change affect the relationships between abundance of functional groups, community-scale leaf traits and above-ground production? Location Perennial grassland in the French Massif Central. Methods Monoliths extracted from the study grassland were exposed to a simulated climate change corresponding to the air temperature, atmospheric CO 2 and summer rainfall conditions projected for 2080. We examined impacts of climate treatments on above-ground biomass and community structure for 4 yr, and investigated the relationship between biomass production, species diversity and three key functional traits: specific leaf area, leaf dry matter content and leaf N content. Results Both warming and simultaneous application of warming, summer drought and elevated CO 2 were associated with an increase in annual above-ground biomass at the start of the study, but biomass responses became progressively negative over the course of the experiment. Decreases in vegetation N exports were also observed over time, possibly due to reduced soil N availability under climate change. Taxonomic diversity showed no response to climate treatments, but the relative abundance of grasses decreased under both warming and simultaneous application of warming, summer drought and elevated CO 2 after 3 yr. In parallel, legume relative abundance increased in all warmed treatments. Functional diversity responses varied depending on climate treatment and leaf trait. In the control treatment, patterns of variation in annual plant biomass were best explained by functional diversity during the study period. However, in warmed treatments, variation in annual plant biomass was more closely linked to the functional traits of dominant species. Conclusions Continuous, multi-year exposure to projected climate conditions has a negative impact on above-ground biomass in our grassland study system. Our data suggest that climate-induced decreases in above-ground biomass may be driven by changes in the relative abundance of plant functional groups, and could also reflect changes in soil nutrient availability. Unlike species diversity, community-level leaf traits and functional diversity appear to play an important role for above-ground biomass production, and may have indirect effects on ecosystem stability in changing climates.

Journal ArticleDOI
TL;DR: The calculation-based results show that climate conditions such as solar irradiation and temperature dynamics play an important role in open raceway ponds and a framework to validate specific cultivation systems is given.
Abstract: To evaluate microalgae production in large scale open ponds under different climatologic conditions, a model-based framework is used to study the effect of light conditions, water temperature and reactor design on trends in algae productivity. Scenario analyses have been done for two algae species using measured weather data of the Netherlands and Algeria. The effects of temperature control, photo-inhibition and using monthly or yearly fixed biomass concentrations are estimated by a sensitivity analysis. The calculation-based results show that climate conditions such as solar irradiation and temperature dynamics play an important role in open raceway ponds. In moderate climate zones low and high temperatures over a season suppress growth. At high latitudes this effect is important as light levels vary much during the day and between seasons. Optimal biomass concentrations in ponds depend on location, pond depth and algae species. Pond design, location and algae species interact and productivity cannot be based solely on general or assumed efficiencies. It is essential to select algae species that have a suitable growth rate, light absorption coefficient and the ability to grow over a broad temperature range. The presented approach gives a framework to validate specific cultivation systems.

Journal ArticleDOI
TL;DR: In this article, a method that uses satellite data to estimate changes in forest aboveground biomass associated with forest disturbances and recovery at annual time steps is presented. But the method is limited to a coniferous forest region in the Western Carpathian Mountains, which experienced long-term environmental changes.

Journal ArticleDOI
22 May 2013-PLOS ONE
TL;DR: The high productivity, bioenergy potential and competitive dominance of Oedogonium make this species an ideal freshwater macroalgal target for large-scale production and a valuable biomass source for bioenergy applications.
Abstract: Intensive cultivation of freshwater macroalgae is likely to increase with the development of an algal biofuels industry and algal bioremediation. However, target freshwater macroalgae species suitable for large-scale intensive cultivation have not yet been identified. Therefore, as a first step to identifying target species, we compared the productivity, growth and biochemical composition of three species representative of key freshwater macroalgae genera across a range of cultivation conditions. We then selected a primary target species and assessed its competitive ability against other species over a range of stocking densities. Oedogonium had the highest productivity (8.0 g ash free dry weight m−2 day−1), lowest ash content (3–8%), lowest water content (fresh weigh: dry weight ratio of 3.4), highest carbon content (45%) and highest bioenergy potential (higher heating value 20 MJ/kg) compared to Cladophora and Spirogyra. The higher productivity of Oedogonium relative to Cladophora and Spirogyra was consistent when algae were cultured with and without the addition of CO2 across three aeration treatments. Therefore, Oedogonium was selected as our primary target species. The competitive ability of Oedogonium was assessed by growing it in bi-cultures and polycultures with Cladophora and Spirogyra over a range of stocking densities. Cultures were initially stocked with equal proportions of each species, but after three weeks of growth the proportion of Oedogonium had increased to at least 96% (±7 S.E.) in Oedogonium-Spirogyra bi-cultures, 86% (±16 S.E.) in Oedogonium-Cladophora bi-cultures and 82% (±18 S.E.) in polycultures. The high productivity, bioenergy potential and competitive dominance of Oedogonium make this species an ideal freshwater macroalgal target for large-scale production and a valuable biomass source for bioenergy applications. These results demonstrate that freshwater macroalgae are thus far an under-utilised feedstock with much potential for biomass applications.

Journal ArticleDOI
TL;DR: In this article, the authors evaluated relative habitat capacity of marsh-sills by comparing plant, sediment, and benthic macroinvertebrate attributes in intertidal and subtidal zones of existing marshsills, natural marshes, tidal flats, and riprap revetment within two subestuaries of Chesapeake Bay, USA.

Journal ArticleDOI
TL;DR: Under landscape ATS operation, substrate manipulation provides a considerable opportunity to increase ATS productivity, water quality amelioration, and biomass coproduction for fertilizers, fermentation energy, and omega‐3 products.
Abstract: Two Algal Turf Scrubber (ATS) units were deployed on the Great Wicomico River (GWR) for 22 months to examine the role of substrate in increasing algal productivity and nutrient removal. The yearly mean productivity of flat ATS screens was 15.4 g · m(-2) · d(-1) . This was elevated to 39.6 g · m(-2) · d(-1) with a three-dimensional (3-D) screen, and to 47.7 g · m(-2) · d(-1) by avoiding high summer harvest temperatures. These methods enhanced nutrient removal (N, P) in algal biomass by 3.5 times. Eighty-six algal taxa (Ochrophyta [diatoms], Chlorophyta [green algae], and Cyan-obacteria [blue-green algae]) self-seeded from the GWR and demonstrated yearly cycling. Silica (SiO2 ) content of the algal biomass ranged from 30% to 50% of total biomass; phosphorus, nitrogen, and carbon content of the total algal biomass ranged from 0.15% to 0.21%, 2.13% to 2.89%, and 20.0% to 25.7%, respectively. Carbohydrate content (at 10%-25% of AFDM) was dominated by glucose. Lipids (fatty acid methyl ester; FAMEs) ranged widely from 0.5% to 9% AFDM, with Omega-3 fatty acids a consistent component. Mathematical modeling of algal produ-ctivity as a function of temperature, light, and substrate showed a proportionality of 4:3:3, resp-ectively. Under landscape ATS operation, substrate manipulation provides a considerable opportunity to increase ATS productivity, water quality amelioration, and biomass coproduction for fertilizers, fermentation energy, and omega-3 products. Based on the 3-D prod-uctivity and algal chemical composition demonstrated, ATS systems used for nonpoint source water treat-ment can produce ethanol (butanol) at 5.8× per unit area of corn, and biodiesel at 12.0× per unit area of soy beans (agricultural production US).

Journal ArticleDOI
15 Sep 2013
TL;DR: In this article, the seasonal and interannual variability of the planktonic communities in a densely sampled region of the northeastern Chukchi Sea as part of a multidisciplinary ecosystem study from 2008 to 2010 was analyzed.
Abstract: We analyzed the seasonal and interannual variability of the planktonic communities in a densely sampled region of the northeastern Chukchi Sea as part of a multidisciplinary ecosystem study from 2008 to 2010. Observations of chlorophyll-a, inorganic macronutrients, and zooplankton (using both 150-μm and 505-μm mesh nets) were made within two 900-NM 2 grids (Klondike and Burger) at high spatial resolution three times each in 2008 and 2009, with a third grid (Statoil) sampled twice in 2010. Sea-ice conditions prior to sampling varied notably during the study: seasonal sea ice retreat was earlier and sea-surface temperatures (SSTs) were warmer in 2009 than in 2008, whereas SSTs for 2010 were intermediate between the 2008 and 2009 values. Eighty taxonomic categories of zooplankton, including 11 meroplanktonic categories, were recorded, with the greatest diversity found within the copepods (25 species), followed by the cnidarians (11 species). All species are typical for the region and most are seeded from the Bering Sea. A seasonal progression of the community structure was apparent over each survey area and was likely influenced by temperature. Cold oceanographic conditions in 2008 likely slowed growth and development of the zooplankton, such that holozooplankton abundance averaged 2389 and 106 individuals m–3 and biomass averaged 10.5 and 8.3 mg DW m–3 in the 150- and 505-μm nets, respectively. An early phytoplankton bloom in 2009 apparently supported a zooplankton community of greater abundance, but moderate biomass, averaging 6842 and 189 individuals m–3, and 16.3 and 7.0 mg DW m–3 in the 150- and 505-μm nets, respectively. Highest zooplankton abundance and biomass values among the three years occurred in 2010: 7396 and 198 individuals m–3 and 102.9 and 33.5 mg DW m–3 in the 150- and 505-μm nets, respectively. Holozooplankton biomass changes were driven by increases in large-bodied, lipid-rich copepods. The contribution of meroplankton was substantial in this shallow-water ecosystem: numerically, they contributed 28% in 2008, 8% in 2009 and 56% in 2010 to the total zooplankton community and 43%, 27%, and 11%, respectively, terms of biomass for the 150-μm nets. Interannual differences in ice-melt timing, water temperatures, northward transport of water masses, and nutrients and chlorophyll concentrations resulted in highly variable pelagic productivity.

Book ChapterDOI
16 Mar 2013
TL;DR: The Pahner Long-Term Ecological Research (LTER) area, the area west of the Antarctic Peninsula, is an important oompmml r:l the Antarctic marine CCOIystem which is composed of • coastal and continental shelf ZOOt (CCSZ) annually IWept by the marginal ice zooe (MIZ).
Abstract: The Pahner Long-Term Ecological Research (LTER) area, the area west of the Antarctic Peninsula, is an important oompmml r:l the Antarctic marine CCOIystem which iJ composed of • coastal and continental shelf ZOOt (CCSZ) annually IWept by the marginal ice zooe (MIZ). This couul canponent of the Antarctic marine ecocy.tem i. influenced by meltwater from glacien and iceberg., inclusive d areas providing some prOl.ectioo from wind and storms, potentially enriched by eu ential micronutrienu from land, supportive of massive blooms that do, in fact. reduce m.crcnutrientJ and supportive of relatively high levelJ of primary productivity. We present an overview of the temporal and spatial variability in phytOplankton biomass and primary produaivily for the LTER area based 00 &hip and satellite dill colleaed in this region and summarize factors controlling primary productivity. H historical data are rqm:sentative, considering the complex It-ce/time variability of the an:.a, then the average primary productivity of thil region is of the order of a few hundred ge m·2 y.1 which, while about a factO!'" of S lower, is roughly ccmparable to other productive coastalan:.al of the world's oceans.