The structure,diversity and somatic production of the fish community in an estuarine coastal lagoon,Ria de Aveiro (Portugal)

The present study aims to determine biological fish production of a lagoon and relate this to the commercial fisheries yield. The fish community of an estuarine lagoon in the west coast of Portugal was sampled between November 1998 and November 2000 to estimate the production ecology of the community, including somatic production, population size, species richness, species diversity, and biomass. Using the Allen curve method of determination, the total annual fish production of all fish species in the lagoon was calculated at 90.3 tonnes or 2.1 g m⁻² year⁻¹ in the first year and 106.7 tonnes or 2.5 g m⁻² year⁻¹ in the second year. The marine seasonal migrant species, sardine, Sardina pilchardus, which colonises the lagoon during the juvenile period of its life stages, produced more than 35 tonnes in each year and accounted for >39 and >33%, in the first and second year respectively, of the total fish production in this lagoon. Sardine was numerically more abundant (18,217 specimens) but due to their small size contributed only 13% to the total biomass. Sardine was thus the most important fish species in terms of the consumption and production processes of the whole fish community in this system. Commercial fisheries’ records indicate that approximately 300 tonnes per annum of fish are taken from the lagoon, which corresponds to three times more than the estimated production in the lagoon. Thus, if it exists, the sustainability of the fishery appears to depend on the immigration of fish from the adjacent coastal area and it is questioned whether the fishery is sustainable in the long-term. The findings indicate that careful and effective management of the lagoon is required to ensure a long-term healthy aquatic environment and sustainable catches in the future.     

Calcium carbonate budgets for two coral reefs affected by different terrestrial runoff regimes, Rio Bueno, Jamaica

A process-based carbonate budget was used to compare carbonate framework production at two reef sites subject to varying degrees of fluvial influence in Rio Bueno, Jamaica. The turbid, central embayment was subjected to high rates of fluvial sediment input, framework accretion was restricted to ≤30 m, and net carbonate production was 1,887 g CaCO₃ m⁻² year⁻¹. Gross carbonate production (GCP) was dominated by scleractinians (97%), particularly by sediment-resistant species, e.g. Diploria strigosa on the reef flat (<2 m). Calcareous encrusters contributed very little carbonate. Total bioerosion removed 265 g CaCO₃ m⁻² year⁻¹ and was dominated by microborers. At the clear-water site, net carbonate production was 1,236 g CaCO₃ m⁻² year⁻¹; the most productive zone was on the fore-reef (10 m). Corals accounted for 82% of GCP, and encrusting organisms 16%. Bioerosion removed 126 g CaCO₃ m⁻² year⁻¹ and was dominated by macroborers. Total fish and urchin grazing was limited throughout (≤20 g CaCO₃ m⁻² year⁻¹). The study demonstrates that: (1) carbonate production and net reef accretion can occur where environmental conditions approach or exceed perceived threshold levels for coral survival; and (2) although live coral cover (and carbonate production rates) were reduced on reef-front sites along the North Jamaican coast, low population densities of grazing fish and echinoids to some extent offset this, thus maintaining positive carbonate budgets.     

Age and productivity of the Antarctic scallop, Adamussium colbecki, in Terra Nova Bay (Ross Sea, Antarctica)

Body size, geographical distribution, and biomass make Adamussium colbecki (Smith, 1902) one of the most conspicuous bivalve species in the Antarctic. Based on samples collected in austral summer 1999/2000 in Terra Nova Bay, the annual formation of shell growth bands visible on X-ray photographs was verified by stable isotope analysis. A general von Bertalanffy growth function was fitted to size-at-age data of 25 individuals (H_∞=108.86 mm, K=0.114 year⁻¹, t₀=−0.367, D=1.284). Somatic production calculated from mass-specific growth rates was 234.6 kJ m⁻² year⁻¹. Gonadal productivity amounted to 70.92 kJ m⁻² year⁻¹. Annual somatic and gonad production-to-biomass ratios (P/B) were 0.199 and 0.052, respectively. According to its consumption and production, A. colbecki is likely to play a significant role in the trophic web of Terra Nova Bay.     

Bacterial production in the carbon flow of a central European stream, the Breitenbach

1. Over the last 30 years, many investigations have been performed on the dynamics of bacteria and organic matter in the Breitenbach, a first‐order stream in central Germany. The data now available allow a synthesis of the role of bacteria in the carbon budget, as an example of the general importance of bacteria in stream ecosystems. 2. Comparing measured and estimated inputs and outputs to the ecosystem, the organic matter budget of the Breitenbach is fairly balanced: 1.84 kg C m^?2 year^?1 (sum of inputs) versus 1.88 kg C m^?2 year^?1 (sum of outputs). No major missing link remains. 3. The basis of the food web in the Breitenbach is mainly allochthonous organic matter (dissolved and particulate 1.02 and 0.42 kg C m^?2 year^?1, respectively). Autochthonous gross primary production is 0.4 kg C m^?2 year^?1. Most of the organic matter leaves the stream via transport to the River Fulda (dissolved and particulate 0.74 and 0.34 kg C m^?2 year^?1, respectively), the rest by respiration (0.80 kg C m^?2 year^?1 or 43% of total outputs). 4. Bacteria constitute an important part (36%) of heterotrophic biomass (average: 0.004 kg m^?2 bacterial C of 0.011 kg m^?2 total heterotrophic C). Bacteria also account for the major fraction (71%) of heterotrophic production: 0.20 of 0.28 kg C m^?2 year^?1 total heterotrophic production. Bacterial production in the Breitenbach is similar in magnitude to the estimate of photoautotrophic net primary production: both approximately 0.20 kg C m^?2 year^?1. 5. Protozoa, the main consumers of bacteria in the Breitenbach, consume approximately one‐third of bacterial production (0.07 kg C m^?2 year^?1). Small metazoa (meiofauna, <0.5 mm) play a lesser role in the consumption of bacteria, consuming <0.01 kg bacterial C m^?2 year^?1. Larger metazoa (macrofauna, >0.5 mm) consume approximately 10% of bacterial production. Although this is a considerable amount of the carbon resources needed by the macrofauna (0.02 kg C m^?2 year^?1 of bacterial production versus 0.06 kg C m^?2 year^?1 macrofauna production plus respiration), the carbon demand of the macrofaunal community is met to a larger extent by particulate organic matter than by bacteria. 6. Bacteria are the main decomposers in the Breitenbach. They account for 78% of heterotrophic respiration (0.47 of 0.60 kg C m^?2 year^?1) and 59% of total respiration (0.47 of 0.80 kg C m^?2 year^?1).     

Differences in carbon fluxes between forested and cultivated micronesian tropical peatlands

Taro is a staple crop that is often grown in wetlands throughout the Indo-Pacific, but the long-term impacts of its cultivation on wetland ecosystem functions are unknown. The objective of this study was to determine how cultivating taro affects carbon cycling by comparing key pathways in a forested peatland and an adjacent cultivated taro patch. Leaves decomposed rapidly at both sites with roughly 73% remaining after 2 weeks, 53% after 8 weeks, 38% after 17 weeks, and 17% after 36 weeks. Root decomposition proceeded much more slowly with roughly 93% remaining after 2 weeks, 80% after 8 weeks, 71% after 17 weeks, and 66% after 36 weeks. Annual litterfall was 1181 g m^–2 year^–1 and 849 g m^–2 year^–1 for the forested and cultivated sites, respectively. For the two sites combined, litterfall consisted of 78% leaves, 10% reproductive material, 3% branches, and 9% miscellaneous material. Fine root biomass was greater in the forested site than the cultivated site, averaging 205 g m^–2 and 34 g m^–2, respectively. Fine root production was much greater in the forested than the cultivated site, averaging 226 g C m^–2 year^–1 and 48 g C m^–2 year^–1, respectively. Soil respiration averaged 99 mg C m^–2 h^–1 and 55 mg C m^–2 h^–1 at the forested and cultivated sites, respectively. We found that the major change to carbon fluxes in the cultivated site was less carbon was entering the peatland, particularly less root production. Alterations to the carbon cycle caused by cultivation would probably not be permanent, because taro patches are periodically abandoned and allowed to regenerate naturally.     

Simulated annual plankton production in the northeastern Pacific Coastal Upwelling Domain

A microcomputer simulation model is presented that describesthe generalized plankton production dynamics, in the surfacemixed layer, of the Juan de Fuca Eddy located on the southwesternBritish Columbia continental shelf. The Juan de Fuca Eddy simulationmodel evaluates how the annual biomass production of diatoms,copepods and euphausiids is forced by plankton feeding interactions,seasonal variability in upwelling, water temperature and solarradiation, and generalized fish predation. The model estimatesannual primary production of 345 g C m^–2 year^–1and secondary production of 19.4 g C m^–2 year^–1for copepods and 6 g C m^–2 year^–1 for euphausiids,during 1985–89; -90% of the annual plankton productionwas generated during the April-October upwelling season. Perturbationsof 22 abiotic and biotic parameters, one at a time by ±10%of nominal values, indicated that oceanic variability (e.g.upwelling rate) most strongly affected primary production. Conversely,zooplankton production was most sensitive to variability inbiological parameters describing zooplankton grazing potentialand growth (e.g. gross growth efficiency). Simulated seasonalbiomass patterns of diatoms, copepods and euphausiids were foundto closely match empirical data. However, euphausiid biomassproduction in the Juan de Fuca Eddy alone was unable to meetthe demands of estimated pelagic fish consumption. Local Eddyeuphausiid populations had to be supplemented, from regionaleuphausiids. by a mechanism that is proposed to be linked tothe seasonal pattern and intensity of positive Ekman transport(upwelling).     

Energy flow and subsidies associated with the complex life cycle of ambystomatid salamanders in ponds and adjacent forest in southern Illinois

Breeding adults and metamorphosing larval amphibians transfer energy between freshwater and terrestrial ecosystems during seasonal migrations and emergences, although rarely has this been quantified. We intensively sampled ambystomatid salamander assemblages (Ambystoma opacum,A. maculatum, and A. tigrinum) in five forested ponds in southern Illinois to quantify energy flow associated with egg deposition, larval production, and emergence of metamorphosed larvae. Oviposition by female salamanders added 7.0–761.4 g ash-free dry mass (AFDM) year⁻¹ to ponds (up to 5.5 g AFDM m⁻² year⁻¹). Larval production ranged from 0.4 to 7.4 g AFDM m⁻² year⁻¹ among populations in three ponds that did not dry during larval development, with as much as 7.9 g AFDM m⁻² year⁻¹ produced by an entire assemblage. Mean larval biomass during cohort production intervals in these three ponds ranged from 0.1 to 2.3 g AFDM m⁻² and annual P/B (production/biomass) ranged from 4 to 21 for individual taxa. Emergent biomass averaged 10% (range=2–35%) of larval production; larval mortality within ponds accounted for the difference. Hydroperiod and intraguild predation limited larval production in some ponds, but emerging metamorphs exported an average of 70.0±33.9 g AFDM year⁻¹ (range=21.0–135.2 g AFDM year⁻¹) from ponds to surrounding forest. For the three ponds where larvae survived to metamorphosis, salamander assemblages provided an average net flux of 349.5±140.8 g AFDM year⁻¹ into pond habitats. Among all ponds, net flux into ponds was highest for the largest pond and decreased for smaller ponds with higher perimeter to surface area ratios (r ² =0.94, P<0.05, n=5). These results are important in understanding the multiple functional roles of salamanders and the impact of amphibian population declines on ecosystems. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

The populations of fish in tributaries of the River Eden on the Moor House National Nature Reserve,northern England

The population dynamics of trout (Salmo trutta L.) were studied in two high-altitude streams flowing westwards into the River Eden in northern England. The results from one (Knock Ore Gill), which is accessible to spawners from downstream, were compared with published data from an isolated population in a nearby stream which flows eastward into the River Tees. The Knock Ore Gill trout had a population density of 0.4–0.9 fish m^–2, a biomass of 12.4 g m^–2, annual production of 12–14 g m^–2 year^–1 and an instantaneous mortality rate of 0.97 year^–1. Comparable values from the Tees tributary were 0.2, 3.3, 2.3 and 0.66 respectively. The Knock Ore Gill population also contrasted with that of the Tees tributary in having reliable recruitment from year to year. These differences were related to differences in the chemistry and spate characteristics of the two streams and to the fact that immigrants from downstream were responsible for over 30% of the annual oviposition in Knock Ore Gill.     

An Analysis of the Biotic Community in a Kumaun Himalayan Lake,Nainital (U. P.), India

A comprehensive study of phyto- and zooplankton and macrozoobenthic components in Lake Nainital showed that species richness was high for plankton and low for macrozoobenthos. The algal biomass was dominated by greens (54 %) and blue-greens (31 %), the zooplankton population by copepods (84 %), and the macrozoobenthic community by a Tubifex-Chironomus association constituting≥95 % of the annual number of the macrobenthic invertebrates. Respiration (807.5g C m⁻² year⁻¹) surpassed gross production (630.5 g C m⁻² year⁻¹). The mean annual ratio between phyto- and zooplankton biomass is 3.3 and between phytoplankton and herbivores it is 4.6. If biomass is treated as a measure of crude production, the relationship among the three trophic levels suggests that herbivory is inefficient while carnivory is efficient, because part of the primary production remains unutilized by dominant herbivorous zooplankters, whereas Mesocyclops leuckarti, the sole carnivore, feeds efficiently on rotifers and juveniles of other copepods. The low diversity of different biotic components and the P/R ratio of less than 1 perhaps suggest that the lake is passing through the stage of heterotrophic succession.     

Micronekton and macrozooplankton in the open waters near Antarctic ice edge zones (AMERIEZ 1983 and 1986)

Summary Micronekton and macrozooplankton assemblages (0–1000 m) were sampled from the open ocean in the vicinity of marginal ice zones in the southern Scotia and western Weddell Seas using midwater trawls. Small regional differences in species composition were found in the differing hydrographic settings with the Scotia Sea being slightly more diverse. Most species exhibited broad vertical ranges with no distinct pattern of vertical movement. Exceptions were mesopelagic fish and Salpa thompsoni which undertook diel vertical migrations. Biomass was high (2.4–3.1 g DW/m²), comparable to Pacific subarctic waters. Euphausia superba and Salpa tompsoni were the numerical and biomass dominants, representing over 50% of the total numbers and standing stocks. In terms of biomass, euphausiids were the most important group at shallow depths (0–200 m) but were surpassed by salps in the Scotia Sea and mesopelagic fish in the Weddell Sea when all depths down to 1000 m were considered. Pelagic fish biomass (3.3–4.4 g WW/m²) greatly exceeded published estimates for birds (0.025–0.070 g WW/m²), seals (0.068–0.089 g WW/m²) and whales (0.167 to 0.399 g WW/m²), making mesopelagic fish the most prevalent krill predators in the Antarctic oceanic system.     

Primary production and nutrient budgets of Sarcocornia perennis ssp. alpini (Lag.) Castroviejo in the salt marsh of the Palmones River estuary (Southern Spain)

Biomass, primary production and nutrient budgets associated to Sarcocornia perennis subspecies (ssp.) alpini were studied in the Palmones River estuary salt marsh (Southern Spain) to evaluate the nutrient sequestration capacity of the low marsh. Above- and belowground living and dead biomass, as well as carbon, nitrogen and phosphorus content were monitored during 1 year. Additionally, the fate of aboveground detritus was evaluated in an experiment on litter decomposition. The detritus production of S. perennis ssp. alpini was almost equivalent to its annual primary production indicating a rapid turnover of biomass. We calculated that only 12% of the aboveground detritus was exported out of the low marsh while the rest was decomposed in the sediment with a rate of 0.8 year⁻¹. Changes in concentrations of total carbon, nitrogen and phosphorus in the sediment showed patterns related to S. perennis ssp. alpini belowground biomass. Our results suggested that the sediment functions as a net sink for nutrients accumulating 550 g C m⁻² year⁻¹, 55 g N m⁻² year⁻¹, and 13 g P m⁻² year⁻¹.     

Fine-root seasonal pattern,production and turnover rate of European beech (Fagus sylvatica L.) stands in Italy Prealps: Possible implications of coppice conversion to high forest

Abstract

The aim of this study was to investigate the possible effects of coppice conversion to high forest on the beech fine-root systems. We compared the seasonal pattern of live and dead fine-root mass (d < 2 mm), production and turnover in three beech stands that differed in management practices. Tree density was higher in the 40-year-old coppice stand than in the stands that were converted from coppice to high forest in 1994 and 2004, respectively. We found that a reduction in tree density reduced the total fine-root biomass (Coppice stand, 353.8 g m^?2; Conversion 1994 stand, 203.6 g m^?2; Conversion 2004 stand, 176.2 g m^?2) which continued to be characterised by a bimodal pattern with two major peaks, one in spring and one in early fall. Conversion to high forest may also affect the fine-root soil depth distribution. Both fine-root production and turnover rate were sensitive to management practices. They were lower in the Coppice stand (production 131.5 g m^?2 year^?1; turnover rate 0.41 year^?1) than in the converted stands (1994 Conversion stand: production 232 g m^?2 year^?1, turnover rate 1.06 year^?1; 2004 Conversion stand: production 164.2 g m^?2 year^?1, turnover rate 0.79 year^?1).     

Trophic interactions and community structure in the upwelling system off Central Chile (33-39°S)

Trophic interactions and community structure in the upwelling system off Central Chile (USCCh) (33-39°S) are analyzed using biological and ecological data concerning the main trophic groups and the Ecopath with Ecosim software version 5.0 (EwE). The model encompasses the fisheries, cetaceans, sea lion, marine birds, cephalopods, large-sized pelagic fish (sword fish), medium-sized pelagic fish (horse mackerel, hoki), small-sized pelagic fish (anchovy, common sardine), demersal fish (e.g. Chilean hake, black conger-eel), benthic invertebrates (red squat lobster, yellow squat lobster) and other groups such as zooplankton, phytoplankton and detritus. Input data was gathered from published and unpublished reports and our own estimates. Trophic interactions, system indicators and food web attributes are calculated using network analysis routines included in EwE. Results indicate that trophic groups are aligned around four trophic levels (TL) with phytoplankton and detritus at the TL=1, while large-sized pelagic fish and cetaceans are top predators (TL>4.0). The fishery is located at an intermediate to low trophic level (TL=2.97), removing about 15% of the calculated system primary production. The pelagic realm dominates the system, with medium-sized pelagic fish as the main fish component in biomass, while small-sized pelagic fish dominate total landings. Chilean hake is by far the main demersal fish component in both, biomass and yield. Predators consume the greater part of the production of the most important fishery resources, particularly juvenile stages of Chilean hake. Consequently, mortality by predation is an important component of total mortality. However, fishery also removes a large fraction of common sardine, anchovy, horse mackerel, and Chilean hake. The analysis of direct and indirect trophic impacts reveals that Chilean hake is a highly cannibalistic species. Chilean hake is also an important predator on anchovy, common sardine, benthic invertebrates, and demersal fish. The fisheries heavily impact on Chilean hake, common sardine, anchovy, and horse mackerel. Total system biomass (B=476 t km⁻² year⁻¹) and throughput (T=89454 t km⁻² year⁻¹) estimated in the USCCh model are in accordance with models of comparable systems. Considering system attributes derived from network analysis, the USCCh can be characterized as an immature system, with short trophic chains and low trophic transfer efficiency. Finally, we suggest that trophic interactions should be considered in stock assessment and management programs in USCCh. In addition, future research programs should be carried out in order to understand the ecosystem effects of fishing and trophic control in this highly productive food web.     

Benthic Bacterial and Fungal Productivity and Carbon Turnover in a Freshwater Marsh

Heterotrophic bacteria and fungi are widely recognized as crucial mediators of carbon, nutrient, and energy flow in ecosystems, yet information on their total annual production in benthic habitats is lacking. To assess the significance of annual microbial production in a structurally complex system, we measured production rates of bacteria and fungi over an annual cycle in four aerobic habitats of a littoral freshwater marsh. Production rates of fungi in plant litter were substantial (0.2 to 2.4 mg C g⁻¹ C) but were clearly outweighed by those of bacteria (2.6 to 18.8 mg C g⁻¹ C) throughout the year. This indicates that bacteria represent the most actively growing microorganisms on marsh plant litter in submerged conditions, a finding that contrasts strikingly with results from both standing dead shoots of marsh plants and submerged plant litter decaying in streams. Concomitant measurements of microbial respiration (1.5 to 15.3 mg C-CO₂ g⁻¹ of plant litter C day⁻¹) point to high microbial growth efficiencies on the plant litter, averaging 45.5%. The submerged plant litter layer together with the thin aerobic sediment layer underneath (average depth of 5 mm) contributed the bulk of microbial production per square meter of marsh surface (99%), whereas bacterial production in the marsh water column and epiphytic biofilms was negligible. The magnitude of the combined production in these compartments (~1,490 g C m⁻² year⁻¹) highlights the importance of carbon flows through microbial biomass, to the extent that even massive primary productivity of the marsh plants (603 g C m⁻² year⁻¹) and subsidiary carbon sources (~330 g C m⁻² year⁻¹) were insufficient to meet the microbial carbon demand. These findings suggest that littoral freshwater marshes are genuine hot spots of aerobic microbial carbon transformations, which may act as net organic carbon importers from adjacent systems and, in turn, emit large amounts of CO₂ (here, ~870 g C m⁻² year⁻¹) into the atmosphere.     

Earthworm secondary production and N flux in agroecosystems: a comparison of two approaches

Production was estimated for Aporrectodea spp. and Lumbricus spp. populations in corn agroecosystems with a 5-year history of manure or inorganic fertilizer applications during 1994–1995 and 1995–1996. Earthworm biomass and production were greater in manure than inorganic fertilizer plots, although biomass and production declined by about 50% between 1994–1995 and 1995–1996 due to unfavorable climatic conditions. Production was highest during the spring and autumn when soil temperatures were between 4 and 22°C. Production was higher in Lumbricus spp. than Aporrectodea spp. populations due to greater Lumbricus spp. biomass. Aporrectodea spp. production was 3.47–16.14 g ash-free dry weight (AFDW) m^–2 year^–1, while Lumbricus spp. production was 6.09–18.11 g AFDW m^–2 year^–1, depending on the fertilizer treatment and the method used to estimate production. However, production estimates from the instantaneous growth rate method were within 27% of the values calculated using the size-frequency method. Nitrogen flux through earthworms was used to estimate efficiency quotients. Net production efficiency (P/A) ranged from 0.64 to 0.76, assimilation efficiency (A/C) ranged from 0.1 to 0.3, and gross production efficiency (P/C) ranged from 0.06 to 0.22. Annual N flux through earthworm populations was higher in manure than inorganic fertilizer plots, and ranged from 2.95 to 5.47 g N m^–2 year^–1 in 1994–1995 and 1.76 to 2.92 g N m^–2 year^–1 in 1995–1996. The N flux through earthworms represented an amount equivalent to 16–30% of crop N uptake during 1994–1995 and 11–18% of crop N uptake during 1995–1996. We concluded that the effects of earthworms on N cycling in corn agroecosystems were substantial, and that N flux through earthworms was influenced significantly by fertilizer amendments. Received: 20 September 1999 / Accepted: 24 March 2000     

Life history and production of Caenis luctuosa (Burmeister) (Ephemeroptera, Caenidae) in two nearby reaches along a small stream

Population dynamics and production of C. luctuosa were compared in two reaches of the Agüera stream (northern Spain). This species showed univoltine winter life history in both sites. However, the start of the recruitment period, and the cohort production interval differed in 1 month between reaches. Secondary production of C. luctuosa ranged from 76 mg m^–2 year^–1 (upper site) to 93 mg m^–2 year^–1 (lower site). Although annual production seemed to be mainly influenced by the biomass found at each site, changes in life history may have also been important. The need to have accurate information about life history of the analysed species at the study sites when assessing secondary production is highlighted.     

Carbon cycling in a loblolly pine plantation

Summary The carbon cycle of a loblolly pine plantation in North Carolina was examined during its 12th through 16th years from planting. Net primary production during the study period averaged 2056 g C m^-2 year^-1. With autotrophic respiration equal to 2068 g C, the calculated gross production was 4124 g C m^-2 year^-1. Heterotrophic respiration of 694 g C m^-2 year^-1 resulted in net ecosystem production of 1362 g C m^-2 year^-1. In carbon cycle comparisons between forest ecosystems, autotrophic respiration rates were found to be closely coupled to regional temperature.     

Linking Belowground Carbon Allocation to Anaerobic CH4 and CO2 Production in a Forested Peatland,New York State

Heterotrophic soil microorganisms rely on carbon (C) allocated belowground in plant production, but belowground C allocation (BCA) by plants is a poorly quantified part of ecosystem C cycling, especially, in peat soil. We applied a C balance approach to quantify BCA in a mixed conifer-red maple (Acer rubrum) forest on deep peat soil. Direct measurements of CH₄ and CO₂ fluxes across the soil surface (soil respiration), production of fine and small plant roots, and aboveground litterfall were used to estimate respiration by roots, by mycorrhizae and by free-living soil microorganisms. Measurements occurred in two consecutive years. Soil respiration rates averaged 1.2 bm μmol m^{? 2} s^{? 1} for CO₂ and 0.58 nmol m^{? 2} s^{? 1} for CH₄ (371 to 403 g C m^{? 2} year^{? 1}). Carbon in aboveground litter (144 g C m^{? 2} year^{? 1}) was 84% greater than C in root production (78 g C m^{? 2} year^{? 1}). Complementary in vitro assays located high rates of anaerobic microbial activity, including methanogenesis, in a dense layer of roots overlying the peat soil and in large-sized fragments within the peat matrix. Large-sized fragments were decomposing roots and aboveground leaf and twig litter, indicating that relatively fresh plant production supported most of the anaerobic microbial activity. Respiration by free-living soil microorganisms in deep peat accounted for, at most, 29 to 38 g C m^{? 2} year^{? 1}. These data emphasize the close coupling between plant production, ecosystem-level C cycling and soil microbial ecology, which BCA can help reveal.     

Benthic secondary production and biomass of insects emerging from a northern German temperate stream

• 1 Secondary production and emergence of aquatic insects were examined in the outlet of Lake Belau, Northern Germany, by means of benthic samples and emergence traps.
• 2 At three stream sections annual larval secondary production varied between 4.9 and 10.8 gDM (dry mass) m^‐2 year^‐1. Insects contributed with 3.4, 8.9, and 8.7% to the total macroinvertebrate production that varied between 56.5 and 215.1 gDM m^‐2 year^‐1. Emerged biomass was between 1.0 and 2.0 gDM m^‐2 year^‐1. At all three stream sections Diptera dominated with a larval production of 3.0–l6.1 gDM m^‐2 year^‐1, followed by Trichoptera with 1.0–2.1 and Ephemeroptera with up to 0.9 gDM m^‐2 year^‐1.
• 3 Average larval production amounted to 9.0 gDM m^‐2 year^‐1 and emerged biomass to 1.7 gDM m^‐2 year^‐1. Larvae of insects amounted to 7.0% of total macroinvertebrate production.
• 4 The ratio of annual emerged biomass to secondary production (E/P) varied among individual taxa. At the stream sections the ratio ranged from 15.9% to 20.1% with an average of 18.3% for the stream.
• 5 Relative constancy of the E/P ratio suggests that the determination of emerged biomass can be used as a method for estimating the secondary production of aquatic insects. The composition of functional feeding groups clearly differs between emerged biomass and total macroinvertebrate production. Therefore, the method does not allow conclusions on the level of production of the whole benthic community. However, composition of functional feeding groups at emergence roughly reflects composition of these groups in the benthic insect community.

     

Measurements of salmonid population performance in relation to habitat in eastern Newfoundland streams

The density, biomass and estimated production of brook trout Salvelinus fontinalis and Atlantic salmon Salmo salar were related to habitat factors in streams of Terra Nova National Park, Newfoundland, Canada. Fish communities at 29 sites (18 brooks; 15 watersheds) were sampled in the summer of 2002, 2003 and 2005. Salmonid density, biomass per unit area and production (derived from biomass and fish size using allometric P:B relationships) were compared with site habitat characteristics (wetted width, lactustrine habitat, per cent riffle habitat, canopy coverage and stream gradient), using an interactive stepwise multiple linear regression. Salmonid biomass (mean: 2·87 g m^?2; range: 0·33–10·88 g m^?2) and estimated production (mean: 3·05 g m^?2 year^?1; range: 0·32–10·98 g m^?2 year^?1) within the study area varied by an order of magnitude, however, habitat variables accounted for much of this variation. Specifically, wetted width and lacustrine area of the tributary played important roles in explaining density, biomass and production. Wetted width was important for all measurements of brook trout and total salmonids while lacustrine area was important for all measurements of Atlantic salmon and played a lesser role in total salmonid biomass. Other factors such as the percentage of riffle habitat, site gradient and canopy coverage provided modest improvements to the fit of some relationships. When models using the same environmental factors were compared, those using production estimates derived from allometric P:B equations in the literature provided improved predictive capability than did those from direct density and biomass estimates. It is proposed that allometric P:B relationships have utility in improving comparisons of stream fish communities, particularly in studies with insufficient resources to measure production directly.