Secondary Productivity Research Articles

Effect of sediment and aquatic ecosystem on fisheries of Mithilanchal

Sediments play on important role in maintaining the productivity of water body, has ability to store the nutrients and release them into water through different mechanisms under different conditions and maintain aquatic ecosystem. The elevate level of sodimentation and turbidity can reduce the productivity of aquatic system both these correlated factors have the potential to decrease primary productivity that may have consequence to secondary productivity and the energy low to higher topic levels. Guidelines that rely on the volumetric determination of "settleable solids" are not endorsed or use because of the difficulty of obtaining a meaningful and generally applicable relationship between this variable and suspended solids Guidelines that rely on gravimetric determination of suspended sediments concentration are recommended for use over those that rely solely on turbidity. However if the relationship is known between these variables, then turbidity may be used as a surrogate or suspended sediment. The use of guidelines that incorporate the duration of exposure to sediments provide useful analytical information or predictive purposes but caution is warranted when attempting to predict the effects of low (d" tens of mgl") levels of sediment over protected period of time. It is concluded that elevated levels of sediment may be harmful to fish and in addition negatively impact on their habitat.

Influence of pH and CO2 source on the performance of microalgae-based secondary domestic wastewater treatment in outdoors pilot raceways

The influence of pH (7, 8 and 9) and CO2 source (pure CO2 or CO2 from flue gas) on both the performance of secondary domestic wastewater treatment and biomass productivity and composition in three outdoors pilot raceways was evaluated for 6months. Average COD, TN, TP and Escherichia coli removal efficiencies of 84±7%, 79±14%, 57±12% and 93±7%, respectively, were recorded. The influence of pH on wastewater treatment was negligible, while the supply of CO2 from flue gas supported higher COD, TOC and TP removals. Biomass productivities ranged from 4±0gm−2d−1 in December to 17±1gm−2d−1 in July. The highest C, N and P biomass contents (64.8%, 12.6% and 2.4%, respectively) were recorded when flue gas was supplied. Finally, while the protein content in the biomass remained constant (38.2±3.3%), the lipid and carbohydrate contents ranged from 5.8% to 23.0% and from 38.0% to 61.2%, respectively.

Opposing forces: Evaluating multiple ecological roles of Pacific salmon in coastal stream ecosystems

Resource flows and disturbance from species migrations can alter the productivity, structure and function of an ecosystem. Annual mass migrations of Pacific salmon (Oncorhynchus spp.) to coastal watersheds import vast quantities of potentially limiting nutrients that have been shown to increase primary and secondary productivity in streams and lakes. Substrate disturbance during spawning can also export nutrients and reduce primary and secondary production. Here we study the impacts of these dual roles of salmon on stream invertebrates. We collected benthic macroinvertebrates in 15 streams prior to and following peak salmon spawning on British Columbia's central coast. Along with other habitat measurements including stream water chemistry, temperature, and watershed size, we investigated the effects of salmon on invertebrate δ15N, δ13C and biomass density (mg/m2) among 15 streams and within 5 streams, upstream and downstream of barriers to spawning salmon. We found that stream invertebrates assimilate salmon‐derived nutrients in proportion to availability but invertebrate biomass density declines in both seasons with increasing salmon density. Benthic disturbance appears to be the cause of this decline in the fall, but the decline in the spring may be due to the slow recovery of invertebrates from substrate disturbance the previous fall or salmon nutrients may be indirectly driving declines in spring invertebrate biomass by subsidizing other trophic levels and eliciting a trophic cascade.

Dynamics of biomass composition and growth during recovery of nitrogen-starved Chromochloris zofingiensis.

The effect of nitrogen replenishment on the kinetics of secondary carotenoids, triacylglycerol (TAG) and primary cell components was studied in nitrogen-starved Chromochloris zofingiensis (Chlorophyta), an oleaginous and carotenogenic microalga. Nitrogen resupplied after a period of starvation was initially consumed at a more than four times higher rate than in an equivalent nitrogen-replete culture. Simultaneously, chlorophylls, primary carotenoids, polar (membrane) lipids and proteins were rapidly produced. After 2days, the contents of these primary metabolites, as well as the nitrogen consumption rate and the overall biomass production rate, had returned to values equivalent to those of cells grown under nitrogen-replete conditions, indicating that culture recovery required 2days. Nitrogen resupply was immediately followed by rapid degradation of TAG and starch, suggesting that these metabolites served as carbon and energy source for the recovery process. Also, the secondary carotenoids canthaxanthin and ketolutein were rapidly degraded upon nitrogen resupply, whereas degradation of astaxanthin, the main secondary carotenoid, started only when the cells were fully recovered 2days after nitrogen resupply. This is the first time that such culture recovery has been described in detail and, moreover, that astaxanthin was found to be not immediately degraded after nitrogen resupply. The observed rapid recovery of C. zofingiensis and the delay in astaxanthin degradation suggest that a repeated batch cultivation may result in a higher secondary carotenoid productivity than a series of classical single batch cultivations.

REVIEW: Chemical contaminant effects on marine ecosystem functioning

Summary Ecosystem functioning underpins the ecosystem services upon which humans rely. Critical functions, such as primary and secondary productivity, are, however, increasingly threatened by a range of anthropogenic stressors. Although the extent of the threat of contamination is large and has been increasing, pollution is one of the least‐studied stressors in ecology. We did a systematic review and critical synthesis of the effects of contaminants on marine and estuarine ecosystem functioning. No other stressors besides toxic chemicals were included in this review. We identified 264 relevant studies across a range of contaminants. Toxic contaminants generally altered marine ecosystem functioning by reducing productivity and increasing respiration. Effects varied, however, according to the type of contaminant and the component(s) of the system studied (e.g. particular trophic levels, functional groups or taxonomic groups). Toxicity studies that included a measure of ecosystem function were strongly biased towards planktonic communities in contrast to studies of biodiversity, which have been dominated by work on soft‐sediment communities. Toxicant studies that included measures of ecosystem function rarely included a measure of biodiversity and rarely interpreted their findings within an ecosystem function context. Studies that included multiple components of an ecosystem, that is more than one functional group of organisms, were more likely to find no effect of contamination, possibly due to ecological interactions. Studies that suffered from unclear or flawed methodology were more likely to find a significant impact of contaminants on some endpoints of ecosystem functioning than studies with appropriate designs. Synthesis and applications. Up to 70% of studies found negative impacts of contaminants on primary production. Toxic contaminants therefore have the potential to greatly affect the ecosystem services and benefits provided by these systems. Our findings will help managers and policymakers to determine whether contaminants are affecting both biodiversity and ecosystem functioning in a given context, therefore helping to prioritize areas for remediation. There is still, however, much to understand about the relationships between biological diversity and ecosystem functioning. Our understanding of chemical contaminant effects will remain patchy until direct measures of both variables are undertaken within multiple ecosystems. We therefore recommend the adoption of functional endpoints, such as productivity and respiration, in ecological studies, routine toxicological studies and ecological risk assessment.

The effects of DDT on the feeding, respiration, survival, and reproduction of Sinocalanus tenellus (Copepoda: Calanoida)

DDT (dichloro-diphenyl-trichloroethane) as a type of organochlorine pesticides, is an important component of pesticides pollution whose impact on the marine ecosystem is urgently to be evaluated. To investigate the biological effects of DDT on the marine ecosystem, copepods being the main contributor of secondary productivity in the marine ecosystem, were selected as target animals. The influence of DDT on the feeding, respiration, survival, and reproduction of Sinocalanus tenellus (S. tenellus) was analyzed and the antioxidant enzymes activities in the individuals were measured under different exposure concentrations of DDT. The 48 h median lethal concentration (LC50) and 96 h LC50 of DDT to S. tenellus were 5.44 and 2.50 μg/dm3, respectively. The filtration rates, grazing rates, and respiration of S. tenellus decreased apparently with increased DDT concentrations. Under lower concentration (<625 ng/dm3) of DDT, the activities of the antioxidant enzymes, including superoxide dismutase and catalase in the animals increased significantly compared with those in the animals without any exposure to DDT, which suggested that the antioxidant enzymes can protect the animals from oxidative damage. However, the activity of the antioxidant enzyme decreased when the animals were exposed to higher concentration (1 250–2 500 ng/dm3) of DDT. The survival rate of both females and males was reduced when they were exposed to DDT less than 250 ng/dm3, but females showed higher survival rate than males when they are under the same concentration. The hatching ratio and the egg diameters of S. tenellus decreased significantly when they were exposed to DDT with a concentration of 25 and 250 ng/dm3, however, the cumulative egg production did not show any significant variation when the animals were exposed to the above DDT concentration. These data in the preset study suggested that exposure to DDT can cause the variation of the species composition of copepods, and further affect the marine ecosystem.

Litter elemental stoichiometry and biomass densities of forest soil invertebrates

To maintain constant chemical composition, i.e. elemental homeostasis, organisms have to consume resources of sufficient quality to meet their own specific stoichiometric demand. Therefore, concentrations of elements indicate resource quality, and rare elements in the environment may act as limiting factors for individual organisms scaling up to constrain population densities. We investigated how the biomass densities of invertebrate populations of temperate forest soil communities depend on 1) the stoichiometry of the basal litter according to ecological stoichiometry concepts and 2) the population average body mass as predicted by metabolic theory. We used a large data set on biomass densities of 4959 populations across 48 forests in three regions of Germany. Following various ecological stoichiometry hypotheses, we tested for effects of the carbon‐to‐element ratios of 10 elements. Additionally, we included the abiotic litter characteristics habitat size (represented by litter depth), litter diversity and pH, as well as forest type as an indicator for human management. Across 12 species groups, we found that the biomass densities scaled significantly with population‐averaged body masses thus supporting metabolic theory. Additionally, 10 of these allometric scaling relationships exhibited interactions with stoichiometric and abiotic co‐variables. The four most frequent co‐variables were 1) forest type, 2) the carbon‐to‐phosphorus ratio (C:P), 3) the carbon‐to‐sodium ratio (C:Na), and the carbon‐to‐nitrogen ratio (C:N). Hence, our analyses support the sodium shortage hypothesis for microbi‐detritivores, the structural elements hypothesis for some predator groups (concerning N), and the secondary productivity hypothesis (concerning P) across all trophic groups in our data. In contrast, the ecosystem size hypothesis was only supported for some meso‐ and macrofauna detritivores. Our study is thus providing a comprehensive analysis how the elemental stoichiometry of the litter as the basal resource constrain population densities across multiple trophic levels of soil communities.

Meta-analysis of Ecopath models reveals secondary productivity patterns across the Gulf of Mexico

The Gulf of Mexico large marine ecosystem (LME) is ecologically and economically important, yet faces numerous anthropogenic stressors. Common metrics driving ecosystem assessment and management, particularly at the LME scale, include fisheries harvest and primary productivity. However, neither is adequate in revealing a complete picture of ecosystem health. Secondary production is an important functional component of marine ecosystems. Yet, inherent difficulties in measuring higher productivity limit its use as an ecosystem indicator. The goals of this study were to: 1) use existing ecosystem models to estimate secondary production within the Gulf of Mexico, 2) identify productivity hotspots based on spatial patterns of secondary productivity across the Gulf LME, 3) compare trophic structure, function, efficiency, and productivity among ecosystem types within the Gulf, and 4) determine effectiveness of primary productivity as an indicator of secondary productivity. A meta-analysis of 18 Ecopath models describing Gulf of Mexico subsystems was conducted. Representative systems included temperate estuaries, tropical lagoons, continental shelves, and coral reefs. Annual secondary production ranged from 128 tonnes (t) wet weight (ww) km−2 in Tampamachoco Lagoon to 15 466 t ww km−2 in the Florida Keys. Spatial patterns of secondary productivity across the Gulf of Mexico LME demonstrate higher values in coastal regions, especially coral reefs. Secondary production is largely supported by benthic food webs across all ecosystems. Benthic food webs are also more efficient with regards to transfer of production than pelagic food webs. No significant relationships between primary and secondary production were observed via linear regression for any ecosystem type, indicating that primary production is not a strong indicator of secondary production. Comparative analyses of ecosystems across the Gulf of Mexico, such as the one presented here, identify critical areas at the LME scale, and support ecosystem-based management initiatives.

Leaf dry matter content predicts herbivore productivity, but its functional diversity is positively related to resilience in grasslands.

This paper addresses whether the ecosystem service of animal production from grasslands depends upon plant functional identity, plant functional diversity or if the resilience of production is a function of this diversity. Using the results of nine grazing experiments the paper shows that productivity is highly dependent on one leaf trait, leaf dry matter content, as well as rainfall. Animal (secondary) productivity is not dependent on plant functional diversity, but the variability in productivity of grasslands is related to the functional diversity of leaf dry matter content. This and a range of independent studies have shown that functional diversity is reduced at high levels of grassland productivity, so it appears that there is a trade-off between productivity and the resilience of productivity in the face of environmental variation.

Biogenic gradients in algal density affect the emergent properties of spatially self-organized mussel beds

Theoretical models highlight that spatially self-organized patterns can have important emergent effects on the functioning of ecosystems, for instance by increasing productivity and affecting the vulnerability to catastrophic shifts. However, most theoretical studies presume idealized homogeneous conditions, which are rarely met in real ecosystems. Using self-organized mussel beds as a case study, we reveal that spatial heterogeneity, resulting from the large-scale effects of mussel beds on their environment, significantly alters the emergent properties predicted by idealized self-organization models that assume homogeneous conditions. The proposed model explicitly considers that the suspended algae, the prime food for the mussels, are supplied by water flow from the seaward boundary of the bed, which causes in combination with consumption a gradual depletion of algae over the simulated domain. Predictions of the model are consistent with properties of natural mussel patterns observed in the field, featuring a decline in mussel biomass and a change in patterning. Model analyses reveal a fundamental change in ecosystem functioning when this self-induced algal depletion gradient is included in the model. First, no enhancement of secondary productivity of the mussels comparing with non-patterns states is predicted, irrespective of parameter setting; the equilibrium amount of mussels is entirely set by the input of algae. Second, alternate stable states, potentially present in the original (no algal gradient) model, are absent when gradual depletion of algae in the overflowing water layer is allowed. Our findings stress the importance of including sufficiently realistic environmental conditions when assessing the emergent properties of self-organized ecosystems.

Seasonal occurrence of sperm whales (Physeter macrocephalus) around Kelvin Seamount in the Sargasso Sea in relation to oceanographic processes

Sperm whales (Physeter macrocephalus) are widely distributed in all oceans, but they are clumped geographically, generally in areas associated with high primary and secondary productivity. The warm, clear waters of the Sargasso Sea are traditionally thought to be low in productivity, however recent surveys have found large numbers of sperm whales there. The New England Seamount Chain bisects the north-western portion of the Sargasso Sea, and might influence the mesoscale eddies associated with the Gulf Stream; creating areas of higher productivity within the Sargasso Sea. We investigated the seasonal occurrence of sperm whales over Kelvin Seamount (part of the New England Seamount Chain) and how it is influenced by oceanographic variables. An autonomous recording device was deployed over Kelvin Seamount from May to June 2006 and November 2006 to June 2007. A total of 6505 hourly two-minute recordings were examined for the presence of sperm whale echolocation clicks. Sperm whales were more prevalent around Kelvin in the spring (April to June: mean=51% of recordings contained clicks) compared to the winter (November to March: mean=16% of recordings contained clicks). Sperm whale prevalence at Kelvin was related to chlorophyll-a concentration four weeks previous, eddy kinetic energy and month. The mesoscale activity associated with the Gulf Stream and the Gulf Stream׳s interaction with the New England Seamount Chain likely play an important role in sperm whale occurrence in this area, by increasing productivity and perhaps concentration of cephalopod species.

Aspergillus oryzae-based cell factory for direct kojic acid production from cellulose.

BackgroundKojic acid (5-Hydroxy-2-(hydroxymethyl)-4-pyrone) is one of the major secondary metabolites in Aspergillus oryzae. It is widely used in food, pharmaceuticals, and cosmetics. The production cost, however, is too high for its use in many applications. Thus, an efficient and cost-effective kojic acid production process would be valuable. However, little is known about the complete set of genes for kojic acid production. Currently, kojic acid is produced from glucose. The efficient production of kojic acid using cellulose as an inexpensive substrate would help establish cost-effective kojic acid production.ResultsA kojic acid transcription factor gene over-expressing the A. oryzae strain was constructed. Three genes related to kojic acid production in this strain were transcribed in higher amounts than those found in the wild-type strain. This strain produced 26.4 g/L kojic acid from 80 g/L glucose. Furthermore, this strain was transformed with plasmid harboring 3 cellulase genes. The resultant A. oryzae strain successfully produced 0.18 g/L of kojic acid in 6 days of fermentation from the phosphoric acid swollen cellulose.ConclusionsKojic acid was produced directly from cellulose material using genetically engineered A. oryzae. Because A. oryzae has efficient protein secretion ability and secondary metabolite productivity, an A. oryzae-based cell factory could be a platform for the production of various kinds of bio-based chemicals.

Induced transcriptional profiling of phenylpropanoid pathway genes increased flavonoid and lignin content in Arabidopsisleaves in response to microbial products

BackgroundThe production and use of biologically derived soil additives is one of the fastest growing sectors of the fertilizer industry. These products have been shown to improve crop yields while at the same time reducing fertilizer inputs to and nutrient loss from cropland. The mechanisms driving the changes in primary productivity and soil processes are poorly understood and little is known about changes in secondary productivity associated with the use of microbial products. Here we investigate secondary metabolic responses to a biologically derived soil additive by monitoring changes in the phenlypropanoid (PP) pathway in Arabidopsis thaliana.ResultsThis study was designed to test the influence of one of these products (Soil Builder™-AF, SB) on secondary metabolism after being applied at different times. One time (TI) application of SB to Arabidopsis increased the accumulation of flavonoids compared to multiple (TII) applications of the same products. Fourteen phenolic compounds including flavonols and anothocyanins were identified by mass spectrometry. Kaempferol-3,7-O-bis-α-L-rhamnoside and quercetin 3,7-dirhamnoside, the major compounds, increased 3-fold and 4-fold, respectively compared to control in the TI treatment. The most abundant anthocyanin was cyanidin 3-rhamnoglucoside, which increased 3-fold and 2-fold in TI compared to the control and TII, respectively. Simultaneously, the expression of genes coding for key enzymes in the PP pathway (phenylalanine ammonia lyase, cinnamate 4-hydroxylase, chalcone synthase, flavonoid-3′-O-hydroxylase, flavonol synthase1 and dihydroflavonol-4-reductase) and regulatory genes (production of anthocyanin pigment2, MYB12, MYB113, MYB114, EGL3, and TT8) were up-regulated in both treatments (TI and TII). Furthermore, application of TI and TII induced expression of the lignin pathway genes (hydroxyl cinamyl transferase, caffeyl-CoA O-methyl transferase, cinnamyl alcohol dehydrogenase, cinnamyl-CoA reductase, secondary wall-associated NAC domain protein1, MYB58 and MYB63 resulting in higher accumulation of lignin content compared to the control.ConclusionsThese results indicate that the additions of microbially based soil additives have a perceptible influence on phenylpropanoid pathway gene regulation and its production of secondary metabolites. These findings open an avenue of research to investigate the mode of action of microbially-based soil additives which may assist in the sustainable production of food, feed, fuel and fiber.

Food Sources for Ruditapes philippinarum in a Coastal Lagoon Determined by Mass Balance and Stable Isotope Approaches

The relationship between the food demand of a clam population (Ruditapes philippinarum (Adams & Reeve 1850)) and the isotopic contributions of potential food sources (phytoplankton, benthic diatoms, and organic matter derived from the sediment surface, seagrass, and seaweeds) to the clam diet were investigated. In particular, we investigated the manner in which dense patches of clams with high secondary productivity are sustained in a coastal lagoon ecosystem (Hichirippu Lagoon) in Hokkaido, Japan. Clam feeding behavior should affect material circulation in this lagoon owing to their high secondary productivity (ca. 130 g C m−2 yr−1). Phytoplankton were initially found to constitute 14–77% of the clam diet, although phytoplankton nitrogen content (1.79–4.48 kmol N) and the food demand of the clam (16.2 kmol N d–1) suggest that phytoplankton can constitute only up to 28% of clam dietary demands. However, use of isotopic signatures alone may be misleading. For example, the contribution of microphytobenthos (MPB) were estimated to be 0–68% on the basis of isotopic signatures but was subsequently shown to be 35±13% (mean ± S.D.) and 64±4% (mean ± S.D.) on the basis of phytoplankton biomass and clam food demand respectively, suggesting that MPB are the primary food source for clams. Thus, in the present study, the abundant MPB in the subtidal area appear to be a key food source for clams, suggesting that these MPB may sustain the high secondary production of the clam.

Effects of Bivalve Aquaculture on the Environment and Their Possible Mitigation: A Review

Bivalve aquaculture, in particular oyster, clam, scallop and mussel culture, is a globally increasing activity. Increased bivalve production translates inevitably into increased impact on the environment surrounding the aquaculture activities. The effects of this type of aquaculture on the environment are often considered less important compared to those of finfish culture. However, bivalves due to their natural characteristics are considered keystone species in the ecosystem and therefore they have the ability to affect the surrounding environment in both negative and positive ways. They influence primary and secondary productivity and start a series of cascade effects on water column and sediment population and dynamics. The purpose of this article is to present a review of the effects of bivalve aquaculture on the surrounding environment and the current mitigation strategies. In addition, this review highlights how the same natural characteristics of bivalves can positively interact with the environment, and the possible use of bivalve aquaculture as restoration and remediation tool for marine environments.

Eyes in the sky: linking satellite oceanography and biotelemetry to explore habitat selection by basking sharks

Satellite-based oceanographic data products are a valuable source of information on potential resource availability for marine species. Satellite oceanography data may be particularly useful in biotelemetry studies on marine species that feed at low trophic levels, such as zooplanktivorous whales, sharks, and rays. The basking shark, Cetorhinus maximus, is a well-documented zooplanktivore in the western North Atlantic, yet little is known of its movements and spatial ecology in this region. A combination of satellite tag technologies were used to describe basking shark movements with respect to concurrent satellite-observed oceanographic conditions in order to test for selection of these environmental variables. Satellite-linked ‘smart’ position only transmitting tags (SPOTs, N = 10) were used to assess horizontal movements, activity space, and habitat selection, while pop-up satellite archival tags (PSATs, N = 7) were used to describe depth preferences of basking sharks during summer and fall. The duration of SPOT tracks ranged from 5 to 45 days. Basking sharks used relatively small activity spaces in three focal areas off Massachusetts: Vineyard Sound, the Great South Channel, and Cape Cod Bay. These sharks appeared to select areas with shallow bottom depths, high primary production and chlorophyll concentrations, and steep surface gradients, but significant selection for these variables was only detected between mid-August and mid-October when the sharks were primarily located in Cape Cod Bay. Basking sharks in the southern Gulf of Maine during summer and fall focus their activities in discrete areas likely to support high primary and secondary productivity. Habitat selection may also be influenced by mating and social activity at times, but further research is needed to differentiate these behaviors from foraging activity. Satellite-based biotelemetry and oceanography are powerful tools that together can provide valuable new insights into habitat selection patterns of highly mobile marine species.

Storm‐induced changes in coastal geomorphology control estuarine secondary productivity

AbstractEstuarine ecosystems are highly sensitive not only to projected effects of climate change such as ocean warming, acidification, and sea‐level rise but also to the incidence of nor'easter storms and hurricanes. The effects of storms and hurricanes can be extreme, with immediate impact on coastal geomorphology and water circulation, which is integral to estuarine function and consequently to provision of ecosystem services. In this article, we present the results of a natural estuarine‐scale experiment on the effects of changes in coastal geomorphology on hydrodynamics and aquaculture production. A bay in Prince Edward Island, Canada, was altered when a nor'easter storm eroded a second tidal inlet through a barrier island. Previous field and modeling studies allowed a comparison of prestorm and post‐storm circulation, food limitation by cultured mussels, and aquaculture harvest. Dramatic increases in mussel production occurred in the year following the opening of the new inlet. Model studies showed that post‐storm circulation reduced food limitation for cultured mussels, allowing greater growth. Climate change is expected to have severe effects on the delivery of marine ecosystem services to human populations by changing the underlying physical‐biological coupling inherent to their functioning.

The biogeography of insects' length–dry mass relationships

Abstract Biomass measures are central to estimating secondary productivity and studying how resources are distributed within an ecosystem. Because directly measuring insect biomass is a lengthy process, many authors have resorted to empirical length–dry mass relationships. The objective of this study was to evaluate the relative importance of latitude, climate and physical habitat (aquatic vs. terrestrial) in explaining the variability in length–dry mass relationships among insect populations. A global meta‐analysis of the body length–dry mass power coefficients of 457 insect samples was conducted using mixed‐effects models. The length–dry mass power coefficients of insects were positively related to the absolute latitude of the study site and to habitat type; with insects captured in aquatic habitats being characterised by higher allometric coefficients than terrestrial ones. Neither the annualised climatic variables (temperature and precipitation) nor the metamorphosis type of insect taxa had a significant effect on the allometric coefficients. The findings may lead to a generalised body length–dry mass relationship for insects, accounting for both the phylogenetic relatedness and the environmental (biotic and abiotic) context of populations.

Associações genotípicas entre componentes de produção e caracteres agronômicos em feijão-caupi

A análise de coeficiente de correlação é uma importante ferramenta no estudo da associação entre os caracteres de feijão-caupi e para avaliar a contribuição de cada fator na produtividade desta cultura. Objetivou-se investigar as relações genotípicas entre a produtividade de grãos em feijão-caupi e alguns componentes de produção e características agronômicas, utilizando a análise de trilha para decompor as correlações em seus efeitos diretos e indiretos. O experimento foi realizado no período de maio a agosto de 2010. Foram utilizadas as cultivares BR8 Caldeirão, IPEAN V69, BRS Guariba e BR17 Gurguéia. Estimou-se as correlações genotípicas entre pares de caracteres e seus efeitos diretos e indiretos considerando os componentes de produção (número de vagens.planta-1 e número de sementes.vagem-1), caracteres agronômicos (altura da planta, área foliar e peso da matéria seca da parte aérea) e a produtividade de grãos. O diagrama de trilha com duas cadeias mostrou-se adequado em explicar as relações entre componentes primários, secundários e produtividade, considerando as altas estimativas dos coeficientes de determinação (R²) e baixos efeitos residuais. O número de vagens.planta-1 e a área foliar foram os caracteres mais correlacionados com a produtividade e se mostram eficientes em praticar-se seleção indireta, com o intuito de obter ganhos genéticos sobre o rendimento de grãos. Também mostraram ser caracteres importantes sobre os efeitos indiretos do número de sementes vagem-1, altura da planta e peso da matéria seca da parte aérea.

Ecological tradeoffs of stabilized salt marshes as a shoreline protection strategy: Effects of artificial structures on macrobenthic assemblages

Armoring shorelines to prevent erosion is a long-standing global practice that has well-documented adverse effects on coastal habitats and organisms. A relatively new form of shoreline protection, referred to as hybrid stabilization, incorporates created marsh in combination with a stabilizing structure such as a low-profile stone sill and is being implemented in many US coastal states as a means to not only control erosion but also to restore coastal habitat. However, there has been limited scientific investigation of ecological benefits and impacts associated with implementation of hybrid stabilization. We evaluated relative habitat capacity of marsh-sills by comparing plant, sediment, and benthic macroinvertebrate attributes in intertidal and subtidal zones of existing marsh-sills, natural marshes, tidal flats, and riprap revetment within two subestuaries of Chesapeake Bay, USA. Low and high marsh plant characteristics (stem count and height) of marsh-sills were similar to or greater than natural marshes. However, sediment was coarser, total organic carbon and total nitrogen concentrations were lower, and benthic macrofaunal community structure differed in marsh-sills compared to natural marshes. Marsh-sills supported lower deposit-feeding infaunal biomass than marshes in the intertidal. Epifaunal suspension-feeders were most prevalent at sites with artificial structure (riprap and marsh-sill), but highly variable among subestuaries. Infaunal abundance, biomass, diversity, and proportion of suspension/interface and deposit feeding animals were greater in shallow subtidal than in intertidal environments. Conversion of existing habitat to marsh-sills may cause localized loss of benthic productivity and sediment bioturbation and nutrient-cycling functions, with the opportunity to enhance filtration capacity by epifaunal recruitment to structures. When creating marshes that require structural support, there should be a balance of minimizing loss of existing habitats while encouraging use of suitable structural habitat for suspension-feeders. If properly implemented, the addition of structural habitat could subsidize secondary productivity particularly in areas where loss of complex biogenic habitat (e.g., oyster reefs) has occurred.