Modelling black fly production dynamics in blackwater streams

SUMMARY. 1. Two predictive models were employed along with intensive field sampling to estimate production of black flies ( Simulium spp.) on snags (submerged wood) in three blackwater streams on the Georgia Coastal Plain of the southeastern U.S.A. One model predicts daily growth rate from temperature and hydrograph pattern; the other predicts habitat abundance (of snags) from river height.
2. In the sixth order Ogeechee River, annual production was twice as high in 1982 (7.1 g dry mass [=DM] m⁻² of snag surface) as in 1983 (3.6 g DM m⁻²). When converted to production per m² of river bottom, values were 35–40% of the snag surface estimates. Annual production was much lower in fourth order Black Creek (1982, 1.3 g DM m⁻² of snag surface) and much higher in the sixth order Satilla River (1975, 15.6–40.0 g DM m⁻²).
3. There was a distinct bimodal pattern of black fly production in the Ogeechee River in both years, with peaks occurring in winter and summer. Similar bimodal patterns of production were found in Black Creek and in the Satilla River. Although there appears to be an intrinsic component to the bimodal pattern, production peaks (growth rate and biomass) appear to be associated with initial stages of flooding.
4. Annual production/biomass ratios (37–85) are the highest reported for black fly populations. The variation of annual P/B ratios among sites was more strongly dependent on the temporal distribution of standing stock biomass than on differences in growth rates. Variation in production among sites appears to be due to differences in current velocity, hydro-graph variability, and abundance of coexisting consumers.     

Host-use patterns of saproxylic phloeophagous and xylophagous Coleoptera adults and larvae along the decay gradient in standing dead black spruce and aspen

Wood-feeding insects play important functional roles in forest ecosystems, contributing significantly to wood decay processes. However, sampling these species in a direct and quantitative way is difficult because they live most of their lives as larvae deep into the wood; knowledge of species-specific host-use patterns along the decay gradient is thus lacking in this group. To cope with these difficulties, we used a novel approach, snag dissection, to investigate occurrence patterns of such Coleoptera adults and larvae. We selected 80 snags of both black spruce and aspen along four classes of decay in five different stands distributed over the tree species' ranges within the province of Quebec, Canada, and dissected a one-meter section of each. All adults and larvae of Buprestidae, Cerambycidae and Scolytinae (Coleoptera: Curculionidae) were collected and identified to the lowest taxonomical level possible. Wood density and snag age were also calculated for each sampled snag. In black spruce, host-use was mostly concentrated at the beginning of the decay gradient. Patterns observed in aspen were opposite, as few insects were found in fresh snags, while most snags in middle to late stages of decay contained insects, often in large numbers, in some reaching densities of over 1000 cerambycid larvae m⁻³. For both tree species, patterns observed were similar across regions sampled. Differences in host-use patterns between the coniferous and deciduous host species may be due to differences in secondary chemistry, mechanical defence mechanisms or the stand dynamics typically associated with each tree species.     

Polar deserts, their plant cover and plant production in the Canadian High Arctic

A total of 41 stands was sampled for species composition and 29 of these stands for plant standing crop and net annual production at 7 sites on 6 arctic islands. Fourteen additional sites on 10 islands were studied in less detail.
Through polar ordination, three groupings were recognized: polar barrens with an average species richness of 6, a phytomass of 24 g m⁻², and a net annual production of 0.8 g m⁻². Comparable data for the cushion plant and snowflush communities were 9, 120, 3 and 13 species, 400 g m⁻², phytomass and 41 g m⁻² net production respectively. Cryptogams are minor except within showflush communities.
The soils show no horizon development, arc alkaline, and are very tow in organic matter, nitrogen, and phosphorus. It is believed that the combination of limited soil moisture in mid-summer and very low nutrient levels are the primary reason for such low plant cover and plant production in these predominantly polar barren landscapes. Geologic substrate with an abundance of frost-shattered rock and topographic position are factors that control the limited availability of water.     

Very high secondary production at a lake outlet

SUMMARY. 1. Larvae and pupae of Simulium noelleri Fried, coated the concrete of parts of an artificial lake outlet in southern England.
2. In the first two (of three) summer generations, development was synchronous and this allowed the calculation of their secondary production by the instantaneous growth method. The production of the two summer generations was, respectively, 229.1 g C m⁻² (7.4 g C m⁻²day⁻¹) and 185.5 g C m⁻² (8.8 g C m⁻² day⁻¹) The contribution of the third summer generation, and the overwintering generation, to annual production would be less than that of the first two summer generations. Nevertheless, annual production will have exceeded 500 g C m⁻² at this site.
3. Larvae are suspension feeders and they captured the rich supply of particulate and dissolved organic material which passed over them after export from the lake. As food is brought to the larvae they only require space for attachment and can thus build up very high population densities (which exceeded 1 × 10⁶ m⁻² on some occasions during the summer). The high population densities result in a high biomass and hence in the high levels of production.     

Peat respiration and decomposition in Antarctic terrestrial moss communities

Oxygen uptake by the peat of two Antarctic bryophyte communities (a moss turf and a moss carpet) is converted to organic matter loss and used to derive the rate of decomposition. The decay rates obtained in this way are evaluated in two mathematical models which simulate the accumulation of dead organic matter (DOM) in the communities from the litter production and decomposition rate. Litter production, the extent of DOM accumulations at present on the sites and mean decomposition rates (i.e. fraction of standing crop lost per year) were 409 g m^-2 year^-1, 33.5 kg m^-2 and 0.017 g g^-1 year^-1 in the moss turf and 392 g m^-2 year^-1, 29.6 kg m-² and 0.010 g g^-1 year^-1 in the moss carpet respectively (all weights expressed as dry weight). Aerobic decomposition rate declined with depth in both communities. From the model's predictions it is suggested that the observed decay rate was too high in the moss turf and too low in the carpet. Possible reasons for this are discussed and suggestions made for future work.     

Biomass and production estimates of a fish community in a small South African estuary

The fish community of the small (17·5 ha) intermittently open East Kleinemonde estuary was sampled between 1994 and 1997 to estimate population size, standing stock, growth and productivity. The estuarine-spawning species were numerically more abundant ( n c . 750 000) but due to their small size contributed only 11·7% to the total biomass. The total annual productivity of all fishes in the estuary ( n c . 890 000), with a standing stock of 28·44 g m ⁻², was calculated at 55·89 g m⁻² year⁻¹. The small sparid Rhabdosargus holubi with a production estimate of 41·35 g m⁻² year⁻¹ accounted for <74% of the total fish production in this estuary.     

Stream channel experiments on downstream movement of recently emerged trout, Salmo trutta L. and salmon, S. salar L.—I. Effect of four different water velocity treatments upon dispersal rate

Four experimental stream channels were used to study instantaneous downstream dispersal rates of young trout, Salmo trutta L., and salmon, S. salur L ., relative to four different water velocities.
Young salmon showed a high rate of dispersal at a low velocity of 7.5 cm s⁻¹ and lower rates at higher velocities of 25 to 70cm s⁻¹. Trout showed their lowest rate at 25cm s⁻¹ with a slightly higher rate at 7.5 cm s⁻¹ and increasingly higher rates at velocities in excess of 25 cm s⁻¹. These results are consistent with field observations on the velocity preferences of young trout and salmon.     

Water velocity, growth-form and diffusion resistances to photosynthetic CO2 uptake in aquatic bryophytes

Abstract. Boundary-layer resistances of aquatic bryophytes for CO₂ diffusion in water were estimated from wind tunnel measurements of evaporation of aniline in air, using the principle of dynamic similarity. The results indicated resistances at water velocities between 0.02 and 0.2 m s ⁻¹ ranging from about 35 to 5 s mm⁻¹ and 70 to 9 s mm⁻¹, respectively, for the mat-forming liverworts Nardia compressa and Scapania undulata , measured on a projected area (canopy) basis. Over a range of velocities from 0.01 to 0.2 m s⁻¹ the estimated CO₂ boundary-layer resistance of the streamer-like shoots of the moss Fontinalis antipyretica is between about 180 and 15 s mm⁻¹. Comparison with experiments on photosynthetic ¹⁴CO₂-uptake at a range of water velocities suggests that boundary-layer resistance limits photosynthesis at velocities below about 0.01 m s^−l in Fontinalis and below about 0.1 m s⁻¹ in the mat-forming species. It is suggested that high leaf-area index allows the mat growth form more effectively to exploit the low boundary-layer resistance at high velocities while remaining relatively invulnerable to drag. By contrast, the streamer form allows Fontinalis to maximize surface area under conditions where boundary-layer resistance is limiting.     

Effects of copper on species composition of benthic insects in a Sierra Nevada, California, stream

SUMMARY. 1. Effects of copper on species composition and production of benthic insects in an oligotrophic stream dosed at low concentrations (2.5-15 μg 1^-1 Cu_r; approximately 12-75 ng 1^-1 Cu²⁺) were determined. Dosing was initially in autumn-early winter when peak densities of many species occur. It was resumed the following summer near the time of egg hatch of most species and continued through the remaining aquatic stages of univoltine and multivoltine taxa.     

The seasonal biomass and productivity of the submerged macrophytes in a polluted Wisconsin stream

SUMMARY 1. We measured biomass and light/dark bottle productivity of macrophytes in a Wisconsin stream throughout one growing season. Except for a brief period in early spring when a Cladophora glomerata -filamentous algal community was dominant, Potamogeton pectinatus was the dominant macrophyte species in Badfish Creek.
2. Maximum community biomass was 710 g DW m⁻², with a maximum above ground biomass of 620 g DW m⁻² and a maximum below ground biomass of 120 g DW m⁻². Annual productivity was estimated at 1435 g DW m⁻² year⁻¹, with a calculated P/B of 2.01.
3. In situ net production averaged 2.83g C g AFDW⁻¹ h⁻¹ Net positive carbon gain by the P. pectinatus community occurred when water temperatures were above 15°C, and daylength at least 12h. This is correlated to the onset of tuber germination in spring, and the point of maximal biomass decline in autumn.     

DOMOIC ACID PRODUCTION IN NITZSCHIA SP. (BACILLARIOPHYCEAE) ISOLATED FROM A SHRIMP-CULTURE POND IN DO SON, VIETNAM

Domoic acid (DA), a neuroexcitatory amino acid, was detected in batch culture of the newly recognized species Nitzschia navis-varingica Lundholm et Moestrup . The production of DA by this diatom was confirmed by electrospray ionization mass spectrometry. The diatom was collected from a shrimp-culture pond in Do Son, Vietnam. The production of DA (1.7 pg·cell ^{− 1}) is within the levels reported for Pseudo-nitzschia multiseries (Hasle) Hasle. The DA production started during the late exponential growth phase and reached a maximum during the early stationary growth phase. Maximum DA levels in the axenic culture decreased to about half that of the nonaxenic culture (0.9 pg·cell ^{− 1} vs. 1.7 pg·cell ^{− 1}), suggesting that DA production by the new species is influenced by bacteria.     

Production and litter processing by crayfish in an Appalachian mountain stream

SUMMARY 1. Mean annual density and biomass () of Cambarus bartonii in an Appalachian mountain stream (U.S.A.) was 12 individuals m⁻² and 1669 mg (ash-free dry weight) m⁻².
2. Annual production ( P ) of C bartonii was 961 mg AFDW m⁻². Despite high biomass, low growth rates resulted in low production and a low P/ ratio of 0.58.
3. While C bartonii constituted 61% of the total macroinvertebrate biomass, it contributed only 13% of annual community secondary production.
4. Litter processing was positively related to temperature and crayfish size. Cambariis bartotnii was estimated to comminute 36 g m⁻² y⁻¹ of leaf litter (>1 mm²) to 24 g m−^>2 y⁻¹ fine particulate material (<1 mm²). The annual pattern of litter comminution by crayfish was regulated by temperature. As a result, >5()% of shredding activity by crayfish occurred from June to September which was also the period of lowest litter standing crops and activity of other shredding macroinvertebrates.
5. We speculate that during summer crayfish play an important role in temperate woodland streams by converting slowly processed leaf litter species (e.g. Rhododendron ) to fine particles which are then available to collector-gatherers (e.g. Chironomidae, Oligochaeta).     

Spatial variations in nutrient supply to the red algae Eucheuma serra (J. Agardh) J. Agardh

The nutrient supply rates within the canopy of the economically important red algal species, Eucheuma serra J. Agardh were determined experimentally in a recirculating flow-chamber. A single individual was placed in the working section of the 2000 × 200 × 250 mm³ acrylic flow-chamber and subjected to unidirectional water velocities from 1.0 to 9.3 cm s⁻¹. Rates of nutrient supply were determined using 9.7 mm diameter CaSO₄ (gypsum) spheres that were attached to the thallus inside and outside of the canopy. The supply rates within the canopy were 56% less than outside of the canopy. Increases in internal and external water velocity asymptotically increased the nutrient supply rates regardless of location. A model was developed to examine how changes in ammonium and nitrate supply compared with the physiologically maximum uptake rates of these nutrients. The results suggest that when the ammonium concentration in the water was 20 µmol L⁻¹ uptake rates were limited by the supply rate especially at velocities below 5 cm s⁻¹, whereas in the case of 20 µmol L⁻¹ of nitrate, the supply of nitrate was more than adequate to maximize nutrient uptake.     

Life-cycle, drift and production of Gammarus pulex L. (Amphipoda) in a Danish spring

SUMMARY. Gammarus pulex L. was studied at three sites in a Danish spring. Breeding took place during the summer and therefore cohorts could be followed. Sexual maturity was not reached until the next summer and maximum age appeared to be two years.
Changes in population size differed between stations and was tentatively related to differences in drift and numbers of predators. Generally the drift was non-selective between cohorts and within cohorts.
Yearly production estimated from production curves was 2.6 g dry weight m⁻² (the young cohort) and 1.2 g dry weight (the old cohort) at Station 1. The respective P / ratios were 3.35 and 1.22. Production of the youngest cohort at the three stations in the period September-May was 0.9–1.3 g m⁻² and P / ratios were 2.14–2.31. Total yearly production at the three stations was estimated at 4–7 g dry weight m⁻².     

The trophic basis of production of the macroinvertebrate community of a southeastern U.S.A. blackwater stream

The trophic basis of production of the macroinvertebrate communities at three sites on a second-order, low gradient blackwater stream in southeastern U.S.A. was determined. The sampling sites were located above, within and below a low-flow swamp system. From 47–64% of macroinvertebrate production was supported by FPOM at the three sites, with dependence on FPOM being greatest at the swamp site. Algae (filamentous species and diatoms) supported 15–31% of production, indicating that algae can be of considerable importance even in fully canopied headwater streams. The production of some collector-gatherers including Stenonema modestum (55%), Hexagenia munda (58%) and Baetis spp. (78%), was supported predominantly by algae. Algae also supported 61–79% of Hydropsychidae production and 68% of Simuliidae production. Animal material supported 16–26% of macroinvertebrate production at the three sites. CPOM was of minor direct importance to the macroinvertebrate community of this headwater stream, supporting only 1–3% of macroinvertebrate production. Shredders ingested only 1–3 g m⁻² y⁻¹ of CPOM, or about 1% of the annual direct leaf fall to this stream. Assuming a 10% assimilation efficiency for CPOM, shredders produced <3 g m⁻² y⁻¹ of FPOM through CPOM processing, this being approximately 2 orders of magnitude less than reported for high gradient headwater streams. These results indicate that low-order coastal plain streams vary somewhat from the River Continuum Concept in that they exhibit little utilization of and dependence on CPOM as a direct energy source. Only the smallest first-order streams and especially the extensive floodplains may be the functional headwaters of these stream systems.     

Effect of organic loading on nitrification and denitrification in a marine sediment microcosm

Abstract The effects of organic additions on nitrification and dentrification were examined in sediment microcosms. The organic material, heat killed yeast, had a C/N ratio of 7.5 and was added to sieved, homogenized sediments. Four treatments were compared: no addition (control), 30 g dry weight (dw) m⁻² mixed throughout the 10 cm sediment column (30M), 100 g dw m⁻² mixed throughout sediments (100M), and 100 g dw m⁻² mixed into top 1 cm (100S). After the microcosms had been established for 7–11 days, depth of O₂ penetration, sediment-water fluxes and nitrification rates were measured. Nitrification rates were measured using three different techniques: N-serve and acetylene inhibition in intact cores, and nitrification potentials in slurris. Increased organic additions decreased O₂ penetration from 2.7 to 0.2 mm while increasing both O₂ consumption, from 30 to 70 mmol O₂ m⁻² d⁻¹, and NO₃⁻ flux into sediments. Nitrification rates in intact cores were similar for the two methods. Highest rates occurred in the 30M treatment, while the lowest rate was measured in the 100S treatment. Total denitrification rates (estimated from nitrification and nitrate fluxes) increased with increased organic addition, because of the high concentrations of NO₃⁻ (40 μM) in the overlaying water. The ratio of nitrification: denitrification was used as an indication of the importance of nitrification as the NO₃⁻ supply for denitrificaion. This ratio decreased from 1.55 to 0.05 iwth increase organic addition.     

The weight-volume relationship of the test of Alveolinella quoyi: Implications for the taphonomy of large fusiform foraminifera

Severin, Kenneth P. & Lipps, Jere H. 1989 01 15: The weight-volume relationship of the test of Alveolinella quoyi: Implications for the taphonomy of large fusiform foraminifera. Lethaia , Vol. 22, pp. 1–12. Oslo. ISSN 0024–1164.
Alveolinella quoyi , the largest living fusiform foraminifer, can be used to infer the paleobiology of extinct fusulinids and alveolinids. We measured test plus organic material weight, test weight, and test volume for A. quoyi , allowing the calculation of test density under various conditions. Tests have an average of 43% chamber space, and an average density of 1.5 gcm^-3. Living individuals can only fill an average of 39% of their chamber space with protoplasm. If they fill the remaining space with sea water, average effective test density is 0.953 gcm^-3, if the space is filled with a gas the density is 0.671 gcm^-3. Living individuals can withstand current velocities of 3–4 m sec^-1, velocities greater than commonly occur in A. quoyi's habitat. Dead tests have lower effective densities than many carbonate sedimentary particles (0.508 g cm^-3 if the chamber space is gas filled, 0.953 g cm^-3 if it is sea water filled), making their settling velocities slow relative to similarly shaped and sized particles. Their large size and high traction velocities (>0.2m sec^-1) makes them unaffected by gentle currents which can remove 100–200 μ sized particles from the sediment. Their low settling velocity will tend to concentrate A. quoyi tests during subsequent resuspension, creating a layer of tests near the sediment-water interface. Concentrations of extinct fusiform foraminifera may have formed in a similar manner. □ Lorger foraminifera, test weight, test volume, test density, taphonomy .     

Galacto-oligosaccharide production using a recycling cell culture of Sterigmatomyces elviae CBS8119

Addition of small amounts of Fe²⁺, Zn²⁺, Cu²⁺ and thiamine-HCl to the culture medium was required for promoting the galacto-oligosaccharide (Gal-OS)-producing activity of Sterigmatomyces elviae CBS8119, when the concentration of yeast extract in the medium was lowered to 0·1 g l⁻¹. Galacto-oligosaccharide production using a recycling cell culture was performed in a medium containing 360 mg ml⁻¹ of lactose supplemented with optimal concentrations of Fe²⁺ (1·5 mg l⁻¹ of FeSO₄.7H₂O), Zn²⁺ (15 mg l⁻¹ of ZnSO₄.7H₂O), Cu²⁺ (0·5 mg l⁻¹ of CuSO₄.5H₂O) and thiamine-HCl (1 mg l⁻¹ ) . Galacto-oligosaccharide production was maintained at high levels during six cycles of production, with the amount of Gal-OS produced in each cycle being more than 216 mg ml⁻¹ (weight yield of more than 60%).     

Abrupt change in primary productivity in a littoral zone of Lake Biwa with the development of a filamentous green-algal community

1. Some characteristics of the photosynthesis and primary production of benthic and planktonic algal communities were investigated in a littoral zone covered with gravel in the north basin of Lake Biwa, paying special attention to the recent development of filamentous green algae (FGA) in the benthic algal community.
2. P_max (maximum gross photosynthesis rate) values of the benthic algal community (0.1–1.2 mg C mg chl. a ⁻¹ h⁻¹) obtained from photosynthesis–irradiance (P–I) curves were lower than those of the planktonic algal community (2.4–11.5 mg C mg chl. a ⁻¹ h⁻¹). This is apparently a result of the high degree of self shading in the benthic algal community and its low turnover as compared with that of the planktonic algal community.
3. Relatively high I_k values (150–200 μmol photon m⁻² s⁻¹) were observed in the benthic algal community only in June–July when a FGA, Spirogyra sp., was abundant. This reflected a photosynthetic characteristic of the Spirogyra itself, in which photosynthesis was saturated at high light intensity.
4. The FGA community established in the layer between planktonic and sessile (benthic algae except for FGA) algal communities. It brought about extraordinarily high organic matter production in the littoral zone at the expense of production in the sessile algal community.     

Litter decomposition by slugs in mixed deciduous woodland

For the one year period considered, it is calculated that 683.5 g m^-2 plant litter entered the study area site. Of the six slugs studied, Arion intermedius Normand, the smallest species, had the highest overall consumption rate on the nine test foods (29.1 ± 0.9 mg dry wt g live wt^-1 d^-1) and the highest overall mean assimilation efficiency (72.0 + 0.9%). The mean faecal production for each of the six slug species was very similar, ranging from 8.4 to 9.9 mg dry wt g live wt^-1 d^-1. Using regression equations of food consumed on faeces produced, it is estimated that the slug fauna each year consumes 8.4% of the leaf litter input and 6.5% of the total available plant litter. Of the plant material consumed, 13.8 g dry wt m^-2 are deposited annually as faeces. The role of slugs in decomposition processes is discussed and compared with that of other soil organisms.