Input Of Fresh Organic Matter Research Articles

Benthic nitrogen regeneration under oxygen and organic matter spatial variability off Concepción (∼36°S), central Chile

The effects of dissolved oxygen (DO) and organic matter (OM) on several geochemical parameters and nitrogen cycling were evaluated in the upwelling region off central Chile (∼36°S). The sediments of the study area presented: (i) nearly anoxic conditions (2.68 μM) and high chlorophyll-a content (1112 mg g−1) within the Concepción Bay (29 m water depth); (ii) suboxic to oxic conditions (10–129 μM), and from moderate to low chlorophyll-a levels (47–13 mg g−1), in a depth transect outside the bay (88–820 m depth); and (iii) suboxic conditions (5.75–8.9 μM) and low chlorophyll-a content (∼13 mg g−1) in the Itata Canyon area (209 and 362 m depth). Nitrogen processes (in mmol m−2 d−1) varied with depth, in association with changes in fresh OM input and DO content at the transect stations: i.e. decreased ammonification (from 12.9 to 1.0), NH4+ efflux (from 4.8 to 1.2) and denitrification (from 1.3 to 0.3), and increased potential nitrification (from 1.0 to 2.4). Concepción Bay and one of the Itata Canyon stations (209 m) were notably different from the others, indicating heterogeneity of benthic nitrogen cycling in this upwelling region. The bay presented the highest ammonification and lowest denitrification rates. Itata Canyon sediments showed high urea influxes at both sites, although high NH4+ influxes and the highest potential nitrification were only found at the 209 m station. Patterns such as the occurrence of dissolved organic nitrogen effluxes (4.9–75) and higher ammonification rates were found at stations <30 km offshore; influxes (9.7–20.5) and lower ammonification rates were observed at stations >52 km offshore. All the stations presented NO3−+NO2− influxes (0.6–4.3). A nitrogen-cycling imbalance in the NH4+ benthic cycle was found at four stations: NH4+ excesses (30–>100%) at two transect and one of the canyon stations, and a deficit (>100%) at the other canyon station. A small proportion of the NO3−+NO2− influxes (<42%) was explained by the processes studied herein. These imbalances indicated potential incubation biases and the presence of other N processes not accounted for in this study.

Clear‐cutting of a Norway spruce stand: implications for controls on the dynamics of dissolved organic matter in the forest floor

SummaryClear‐cutting of forest provides a unique opportunity to study the response of dynamic controls on dissolved organic matter. We examined differences in concentrations, fluxes and properties of dissolved organic matter from a control and a clear‐cut stand to reveal controlling factors on its dynamics. We measured dissolved organic C and N concentrations and fluxes in the Oi, Oe and Oa horizons of a Norway spruce stand and an adjacent clear‐cutting over 3 years. Aromaticity and complexity of organic molecules were determined by UV and fluorescence spectroscopy, and we measured δ13C ratios over 1 year.Annual fluxes of dissolved organic C and N remained unchanged in the thin Oi horizon (∼ 260 kg C ha−1, ∼ 8.5 kg N ha−1), despite the large reduction in fresh organic matter inputs after clear‐cutting. We conclude that production of dissolved organic matter is not limited by lack of resource. Gross fluxes of dissolved organic C and N increased by about 60% in the Oe and 40% in the Oa horizon upon clear‐cutting. Increasing organic C and N concentrations and increasing water fluxes resulted in 380 kg C ha−1 year−1 and 10.5 kg N ha−1 year−1 entering the mineral soil of the clear‐cut plots. We found numerous indications that the greater microbial activity induced by an increased temperature of 1.5°C in the forest floor is the major factor controlling the enhanced production of dissolved organic matter. Increasing aromaticity and complexity of organic molecules and depletion of 13C pointed to an accelerated processing of more strongly decomposed parts of the forest floor resulting in increased release of lignin‐derived molecules after clear‐cutting. The largest net fluxes of dissolved organic C and N were in the Oi horizon, yet dissolved organic matter sampled in the Oa horizon did not originate mainly from the Oi horizon. Largest gross fluxes in the Oa horizon (control 282 kg C ha−1) and increased aromaticity and complexity of the molecules with increasing depth suggested that dissolved organic matter was derived mainly from decomposition, transformation and leaching of more decomposed material of the forest floor. Our results imply that clear‐cutting releases additional dissolved organic matter which is sequestered in the mineral soil where it has greater resistance to microbial decay.

Organic matter sources and transport in an agriculturally dominated temperate watershed

The quality, quantity, and origin of suspended organic matter were studied in the highly agricultural Upper Scioto River in Central Ohio. Late summer baseflow conditions were compared to late autumn high flow conditions. Variables examined in the suspended matter were the total suspended solids concentration, semi-quantitative concentrations of lignin, carbohydrate concentrations, total organic C, total and organic P, and δ- 13C. Also examined were ratios of C to N, organic C to organic P ratios and fluxes of total organic C. The primary hypothesis of this research was that the quality (or biodegradability) and quantity of organic matter in the Upper Scioto River would increase during autumn stormflow conditions due to inputs of fresh terrestrial organic matter. The autumn suspended matter was also expected to reflect C4 plant contributions from corn organic matter. Results show that the quality and quantity of organic matter were greater during summer, as reflected in low molar ratios (178:1) of organic C to organic P, and higher organic C content of the suspended matter in summer. Summer suspended matter was 3.6% organic C and autumn suspended matter was 2.3% organic C. Carbon to N molar ratios in both seasons were very close to the Redfield ratio (6.6:1 in summer and 6.7:1 in autumn). Total suspended matter and total organic C concentrations were lower in autumn (8.7 mg/l −1 TOC and 17.7 mg/l −1 TSS) than in summer (17.5 mg/l −1 TOC and 39.0 mg/l −1 TSS), but the fluxes were greater in autumn due to greater stream flow. Stable isotope analyses suggested a phytoplankton or C3 plant source (most likely corn) for summer organic C (mean δ 13C of −24.8‰) and a phytoplankton or C4 plant source for autumn organic matter (δ 13C=−21.5‰).

Carbon utilization profiles of microbial communities in southern and central North Sea sediments in relation to environmental variables

We evaluated the relationship between environmental parameters (chlorophylla supply, C/N ratio, redox potential and silt content) and the functional profile of benthic microbial communities by means of community-level physiological profiling (CLPP). Down-core sediment profiles (0–2 cm, 2–5 cm, 5–10 cm) were examined at seven stations in the North Sea, a shallow European shelf sea. The stations reflected an environmental gradient from the coastal to the offshore area. Microbial communities were clearly separated by site, with the clearest differences observed between German Bight versus the Dogger Bank. Canonical correspondence analysis (CCA) followed by a Monte Carlo permutation test showed that differences in CLPP were significantly related to organic carbon supply, oxygen conditions and silt content. Differences in specific carbon source utilization were related to potential functional changes, such as increased amino acid in sediments receiving fresh organic matter input. Overall, the approach proved successful for testing the significance of environmental conditions on microbial communities across a broad geographical region, and should prove valuable for defining both the sampling design and research questions for further studies.

The priming effect of organic matter: a question of microbial competition?

It is generally accepted that the low quality of soil carbon limits the amount of energy available for soil microorganisms, and in turn the rate of soil carbon mineralization. The priming effect, i.e. the increase in soil organic matter (SOM) decomposition rate after fresh organic matter input to soil, is often supposed to result from a global increase in microbial activity due to the higher availability of energy released from the decomposition of fresh organic matter. Work to date, however, suggests that supply of available energy induces no effect on SOM mineralization. The mechanisms of the priming effect are much more complex than commonly believed. The objective of this review was to build a conceptual model of the priming effect based on the contradictory results available in the literature adopting the concept of nutritional competition. After fresh organic matter input to soils, many specialized microorganisms grow quickly and only decompose the fresh organic matter. We postulated that the priming effect results from the competition for energy and nutrient acquisition between the microorganisms specialized in the decomposition of fresh organic matter and those feeding on polymerised SOM.

Seasonal and interannual variability of benthic foraminiferal faunas at 550 m depth in the Bay of Biscay

Live benthic foraminiferal faunas were sampled 10 times between October 1997 and April 2000 at a 550 m depth open-slope station in the Bay of Biscay. Duplicate cores for 5 samplings allow distinguishing between spatial and temporal variability of the foraminiferal faunas. Although spatial patchiness of the foraminiferal faunas is substantial, especially in the 63–150 μm fraction, the temporal variability appears to be larger. The foraminiferal patterns are compared with surface water primary production as assessed by the study of available SeaWIFS satellite images. In the study area, the primary production regime is marked by a pulselike and prolonged spring bloom and possibly a short fall bloom. Such periods of elevated chlorophyll- a concentration are followed, after a delay of about 4–6 weeks, by a strong frequency increase of the most opportunistic taxa of benthic foraminifera. Surprisingly, no change of bottom and interstitial water oxygenation and of redox conditions within the sediment is recorded. The small taxa Epistominella exigua, Reophax guttiferus, Bolivina spathulata, Cassidulina carinata and Nuttallides pusillus appear to respond first to a labile organic matter input, by a reproductive event marked by a strong patchy spatial distribution hypothetically resulting of the spatial heterogeneity of organic matter deposits. Uvigerina peregrina and Uvigerina mediterranea, the most opportunistic larger taxa, strongly dominate the >150 μm fraction during eutrophic periods (spring and fall blooms). Intermediate and deep infaunal taxa seem to depend less on fresh organic matter input, even if a small frequency increases are recorded in the >150 μm fraction during the most productive periods; Globobulimina affinis and Melonis barleeanus show reproductive events in rather shallow sediment layers in the more oligotrophic periods of the year. A conceptual model explains the increasing delay in the response to important phytoplankton bloom periods for the successive benthic ecosystem compartments.

Are the links between soil aggregate size class, soil organic matter and respiration rate artefacts of the fractionation procedure?

Our aim was to see how variations in aggregate fractionation procedures influence the chemical and biological properties of different sized soil aggregates. Soil was fractionated using two different physical procedures: (1) slaking to simulate a major wetting stress in the field or (2) shaking to simulate mechanical disruption by tillage followed by wet sieving. In the slaked treatment, macro-aggregates (<250 μm dia) contained about 17% more soil organic C and had about 30% faster rates of respiration. This was in contrast to the shaken treatment where micro-aggregates (<250 μm dia) contained about 12% more soil organic C and had about 14% faster rates of respiration. The biological and chemical properties of different sized aggregates were used to describe two different models. These were the aggregate heirarchy model and one based on maximum biological activity at soil surfaces. Our results suggest that the chemical and biological properties of aggregates depend on the fractionation procedure. On this basis we suggest that the observed relationships between aggregate size and other properties, for example biological activity, must be interpreted in terms of the disruptive mechanisms used to fractionate aggregated soil. Our results suggest that the aggregate hypothesis has serious weaknesses: the aggregates measured being largely an artefact of the chosen method of separation. We therefore suggest that future work should also consider biological activities at soil pore surfaces. It is at the surface of these channels that parameters such as oxygen supply, plant roots, root exudates and fresh organic matter inputs first interact with the soil. Biological processes in this region are therefore likely to be more important than those occurring in the bulk soil.

ORGANIC-WALLED ALLOGROMIIDS: ASPECTS OF THEIR OCCURRENCE, DIVERSITY AND ECOLOGY IN MARINE HABITATS

Foraminifera with an organic, or predominantly organic, test wall (‘allogromiids’ in the traditional sense) are an important, diverse but often overlooked component of marine benthic communities. This paper reviews some of the scattered literature on these protists. They vary from <50μm to a centimetre or more in length and are morphologically diverse, including spherical, oval, sausage-shaped and thread-like forms. Most are monothalamous and have either one aperture (e.g. Allogromia ) or two terminal apertures at either end of the test (e.g. Nemogullmia and Tinogullmia ). Some distinctive deep-sea forms ( Nodellum, Placopsilinella and Resigella ) are polythalamous; the test consists of more or less well-defined chambers and the wall is brownish in colour. Organic-walled allogromiids are reported from marine habitats ranging from supralittoral sands and intertidal mudflats to deep-sea trenches and are particularly abundant and diverse in cold, tranquil settings with fine-grained sediments (e.g. the deep sea, fjords, and some polar environments). Relatively few morphospecies have been formally described, and most of these are from coastal and intertidal settings, yet these delicate foraminifera often account for 10–20% of individuals and morphospecies in deep-sea samples. At Arctic coastal sites influenced by turbid glacial meltwater, and in some estuaries, allogromiids (including saccamminids) represent an even higher proportion of live foraminifera, in some cases >90%. In contrast, organic-walled allogromiids and other monothalamous forms are usually relatively uncommon in dysoxic settings. Experimental and field studies support the idea that, in a general sense, allogromiids are less tolerant of oxygen depletion than the calcareous taxa that usually dominate foraminiferal faunas in low-oxygen habitats. Organic-walled allogromiids occupy a variety of microhabitats. Intertidal and sublittoral species have been described from the sheltered interiors of empty polychaete tubes and large foraminiferal tests. Some species are associated with the sediment-water interface while others occur at different depths within the sediment. Very elongate, thread-like morphotypes often live several centimeters below the sediment surface in bathyal and abyssal settings. The ecological role of organic-walled allogromiids is poorly known. In general, they seem to be less responsive to inputs of fresh organic matter than calcareous foraminifera. Indirect evidence suggests that many deep-sea species, particularly forms with two terminal apertures, consume bacteria.

Managing soil organic matter – implications for soil structure on organic farms

Abstract. This paper reviews current understanding of soil structure, the role of soil organic matter (SOM) in soil structure and evidence for or against better soil physical condition under organic farming. It also includes new data from farm case studies in the UK. Young SOM is especially important for soil structural development, improving ephemeral stability through fungal hyphae, extracellular polysaccharides, etc. Thus, to achieve aggregate stability and the advantages that this conveys, frequent input of fresh organic matter is required. Practices that add organic material are routinely a feature of organically farmed soils and the literature generally shows that, comparing like with like, organic farms had at least as good and sometimes better soil structure than conventionally managed farms. Our case studies confirmed this. In the reviewed papers, SOM was generally larger on the biodynamic/organic farms because of the organic additions and/or leys in the rotation. We can therefore hypothesize that, because it is especially the light fraction of SOM that is involved in soil structural development, soil structure will improve in a soil to which fresh organic residues are added regularly. Thus, we argue it is not the farming system per se that is important in promoting better physical condition, but the amount and quality of organic matter returned to a soil.

The Nature of Organic Matter in the Danube River Particles and North-western Black Sea Sediments

Suspended matter and sediments from the Danube River and the adjacent north-western Black Sea were analysed for organic carbon, nitrogen and biogenic carbonate and silica, as well as for different fractions of organic matter such as amino acids and carbohydrates. In addition, the nitrogen isotopic composition of surficial sediments of the NW Black Sea was examined. Particulate organic carbon (POC) contents decrease with total suspended solid (TSS) concentration due to dilution by mineral matter derived from upstream and riverbed erosion. The contribution of labile constituents such as amino acids and carbohydrates to POC remains uniform across the measured TSS contents. This suggests that any possible decrease in labile POC (LPOC) from dilution with refractory organic matter is masked by inputs of fresh organic matter from tributaries downstream. Comparison of TSS, POC and LPOC leaving the Iron Gate I barrier at the head of the Danube delta shows that the bulk of material currently entering the Black Sea is derived from inputs from tributaries and riverbed erosion, downstream of the Iron Gate I. The nature and distribution of organic matter in the surface sediments of the Black Sea are influenced by mixing between Danube-derived material and freshly produced organic matter on the shelf and in the open sea, on the one hand, and by oxic degradation during transport from the shelf to the abyssal Black sea, on the other. Preliminary data on the stable isotopic composition of nitrogen in surface sediments of the Black Sea further suggest that organic matter production on the shelf and the adjacent north-western Black Sea is fuelled by different nitrogen sources.

Characteristics and sources of the settling particulate organic matter in the South Adriatic basin

In the South Adriatic Pit a mooring equipped with two time-series sediment traps and two Aanderaa RCM7 current meters was deployed in the frame of EEC-MAST II Mediterranean Targeted Project 1, Subproject Euromarge-AS. The first trap was located 35 m above the bottom (mab) and the second 500 mab. Sediment deposition fluxes were recorded biweekly over 18 months (1 April 1994 to 31 October 1995) in the deeper sediment trap, and over 12 months (15 November 1994 to 31 October 1995) in the 500 mab trap. The settling material and surficial sediment have been analysed for inorganic and organic carbon, δ 13C composition, total nitrogen, and biogenic silica, in order to infer the sources of material. The total mass fluxes at both depths were characterized by a high variability and did not present a clear seasonal trend. Values obtained in the 500 mab trap were generally 2–3 times lower but occasionally similar. The fluctuations were similar in both traps. Based on analyses of inorganic and organic constituents it appears that the fresh organic matter produced in the surface layer rapidly sank through the water column. Strong seasonal variations of biogenic constituents occurred. During spring–early summer an input of fresh organic matter prevailed due to the blooms of mainly siliceous phytoplankton. Late summer and winter samples were characterized by more degraded matter originating from calcareous phytoplankton. A significant imprint of terrigenous organic matter was observed in summer and winter 1994, most likely because an unusually high Po River inflow was the most important fresh water source for the Adriatic. A vertical budget of organic carbon has been calculated; only 2.7% of mean annual primary production reaches the 500 mab trap, suggesting that remineralization processes take place mainly in the upper part of the water column. Comparison between 35 mab trap particle fluxes and bottom rain (calculated as sum of remineralization fluxes and burial) indicates that a strong near-bottom input of material between the deepest trap and the surficial sediment exists due to the lateral advection.

Chemical nature of soil organic matter under grassland and recently established forest

SummaryCarbon‐13 (C‐13) solid‐state NMR spectroscopy was used to investigate the chemical nature of organic C in mineral topsoil sampled under grassland and adjacent recently established (10–17 years old) coniferous forest (Douglas fir, Pseudotsuga menziesii; Ponderosa pine, Pinus ponderosa; Corsican pine, Pinus nigra) at two sites (Craigieburn, Cave Stream) in the South Island of New Zealand. This involved using a Cross‐Polarized/Magic‐Angle Spinning (CP/MAS) technique to identify different chemical forms of soil organic C, whilst Proton Spin Relaxation Editing (PSRE) was used to determine different ‘pools’ of soil organic C. Results obtained from the Craigieburn soils (0–5 cm) were more promising than those obtained from the Cave Stream soils (0–10 cm) because the total Fe content was smaller, and indicated a shift towards more recalcitrant forms of organic C in soil under trees compared with grassland, which might reflect reduced inputs of fresh organic matter to the soil under trees.

The Metazoan Meiofauna in Its Biogeochemical Environment: The Case of an Antarctic Coastal Sediment

The metazoan meiobenthos was investigated in an Antarctic coastal sediment (Factory Cove, Signy Island, Antarctica). The fine sands contained much higher abundances compared to major sublittoral sediments worldwide. Classified second after Narrangansett Bay (North Atlantic) they reached numbers of 13 × 106ind m-2. The meiofauna was highly abundant in the surface layers, but densities decreased sharply below 2 cm. Vertical profiles mirrored steep gradients of microbiota, chloropigments and organic matter and were coincident with chemical stratification. Spatial patchiness manifested especially in the surface layer. Nematodes dominated (up to 90%), andAponema, Chromctdorita, Diplolaimella, Daptonema, MicrolaimusandNeochromadoraconstituted almost the entire community. Overall, the nematode fauna showed a strong similarity with fine sand communities elsewhere. The dominant trophic strategies were epistrarum and non-selective deposit feeding, but the applied classification for feeding guild structure of the nematodes of Factory Cove is discussed. High standing stock, low diversity and shallow depth distribution may have occurred because of the high nutritive (chlorophyll exceeded lOOOmgm-2and constituted almost 50% of the organic pool) and reductive character of the benthic environment. These observations must have originated from the substantial input of fresh organic matter from phytoplankton and microphytobenthic production, typical for an Antarctic coastal ecosystem during the austral summer.

Nutrient cycling through microbial biomass under rice-pasture rotations replacing native savanna

An area of native savanna on an acid, strongly P-sorbing Oxisol in the Eastern Plains of Colombia was opened and sown to various rotations of grass pasture with rice, grass-legume pasture with rice or rice monocrop. After 4.5 y, the soil under each cropping system was sampled and analysed for total organic matter, microbial C, N and P content, and mineralization rate of C and N. Microbial biomass C did not vary much among treatments, whereas the N and P contents of the biomass were considerably lower in rice monocrop than in any crop-pasture treatment. Biomass P was also low under native savanna. The contribution of microbial N or P to soil-organic-matter N or P was lowest under the rice monocrop and highest under the grass-legume pasture. Microbial C-to-N ratios fell in ranges commonly reported, but C-to-P ratios were rather wide (34–50), indicating that the microbes may have adapted themselves to the low-P conditions of these soils. The contribution of microbial P to soil-organic-matter P, however, was about the same as usually found in soils of much higher P fertility. As microbial biomass nutrients cycle relatively rapidly and P availability in these strongly P-sorbing soils is low, the microbial biomass may play an important role in supplying P to plants growing in these soils. A similar conclusion was reached for N. The microbial respiration rate per unit of microbial biomass C ( qCO 2), as determined during an 11-day incubation, was higher under rice-pasture rotations—particularly in the presence of a legume—than under rice monocropping. This suggests that a greater fraction of microbes was active under rice-pasture rotations, probably because of a more continuous and higher input of fresh organic matter. The fraction of organic matter mineralized during the incubation was also highest for the rice-pasture treatments.

Practical Aspects of Chemistry in Pond Aquaculture

Abstract Relationships among liming, fertilization, water and soil chemistry, phytoplankton response, and aquatic animal production are still poorly understood. There is considerable confusion about critical nutrients and fertilizer formulations for pond fertilization. The literature does not support the high application rates of nitrogen often used. Nitrate is more desirable than ammonium or urea as a source of fertilizer nitrogen. Problems in ponds with water and soil quality that are related to feeding result primarily from high inputs of feed. Organic matter is decomposed mostly to stable humus during a growing season, and there is little accumulation of highly decomposable organic matter from one crop to the next. High input of fresh organic matter to the bottom during a crop period can cause high oxygen demand in sediment, but sediment removal between growth cycles does not greatly reduce soil oxygen demand for the next crop. Organic matter resuspension without erosion of mineral soil has the potent...

Methane Metabolism in a Temperate Swamp

Comparisons between in situ CH(4) concentration and potential factors controlling its net production were made in a temperate swamp. Seasonal measurements of water table level and depth profiles of pH, dissolved CH(4), CO(2), O(2), SO(4), NO(3), formate, acetate, propionate, and butyrate were made at two adjacent sites 1.5 to 2 m apart. Dissolved CH(4) was inversely correlated to O(2) and, in general, to NO(3) and SO(4), potential inhibitors of methanogenesis. At low water table levels (August 1992), maximal CH(4) (2 to 4 muM) occurred below 30 cm, whereas at high water table levels (October 1992) or under flooded conditions (May 1993), CH(4) maxima (4 to 55 muM) occurred in the top 10 to 20 cm. Higher CH(4) concentrations were likely supported by inputs of fresh organic matter from decaying leaf litter, as suggested by high acetate and propionate concentrations (25 to 100 muM) in one of the sites in fall and spring. Measurements of potential CH(4) production (and consumption) showed that the highest rates generally occurred in the top 10 cm of soil. Soil slurry incubations confirmed the importance of organic matter to CH(4) production but also showed that competition for substrates by nonmethanogenic microorganisms could greatly attenuate its effect.

Impact of gypsum application on the methane emission from a wetland rice field

Methane emission from Philippine rice paddies was monitored with a closed chamber technique during the 1991 and 1992 wet season. The methane emission from plots amended with 6.66 tons.ha−1 gypsum was reduced by 55–70% compared to non‐amended plots. Although CH4 emission from fields with a high input of fresh organic matter was strongly enhanced, the experiments showed that the relative reduction in CH4 emission upon gypsum application was independent of organic matter addition. The reduced CH4 emission upon gypsum application was most likely due to inhibition of methanogenesis by sulfate‐reducing bacteria. Observed SO42− concentrations in the soil solution of gypsum‐amended plots were well above minimum concentrations reported in the literature for successful competition of sulfate‐reducing bacteria with methanogens. The data provide a base for reducing the estimates of CH4 emissions from rice grown on high‐sulfate containing soils or gypsum‐amended soils.

Historical Relationships Between Research and Resource Management in the Apalachicola River Estuary.

A continuous field research effort has been carried out in the Apalachicola River estuary since March 1972. The information generated from this interdisciplinary study has been directly applied to the management of the Apalachicola resource by means of close associations among local, state, and federal officials and university scientists. During the early years, scientific data were instrumental in the prevention of the impoundment of the Apalachicola River. A series of regional studies was carried out to evaluate various forms of effects due to forestry activities, pesticides, and stormwater runoff from urban areas. A review was made of fisheries problems associated with dredging, overfishing, and marine pollution. Results of such studies were directly applied to local management questions. Research that linked the river wetlands with the estuary, in terms of the input of fresh water, nutrients, and organic matter, served as the basis for the purchase of extensive bottomland tracts. Other initiatives were carried out that were designed to protect the naturally high productivity of the river estuary. Further purchases of estuarine wetlands and barrier island properties were made that formed an almost continuous buffer of publicly held lands between upland developments and critical habitats and important populations of the bay system. A regional management plan was adopted that was designed to limit local municipal development in the estuarine region. Analyses of the long-term scientific data indicated that dominant, commercially important estuarine populations are associated with river flow, local salinity characteristics, and biological (predation, competition) interactions with the salinity regime and food web structure. Such interactions are not straight forward, however; they reflect complex interactions of the freshwater influxes and biological response in the estuary that are not well understood. Species-specific responses to the principal driving factors further complicate the biological relationships of the Apalachicola system. The management of a river-dominated estuary should be based on protection and control of freshwater sources, nutrients, and organic matter with a minimization of physical alterations that often lead to increased salinity stratification and the associated loss of the nursery function of the estuary. There is growing evidence that changes in upland characteristics and within-system habitat alterations are associated with changes in nutrient distributions and salinity relationships and that such changes can have serious impacts on estuarine systems. Issues involving basic changes in estuarine productivity and associated food webs are far more important than those involving species diversity in the management of such resources. Processes such as nutrient flow and salinity alteration underlie the very basis of estuarine productivity and usefulness. Over the past decade, there has been a gradual reduction in the importance of research as an integral part of the planning and management process in the Apalachicola system. This regional trend follows a national pattern. Dredging effects on the river and bay have gone on without effective challenge even though such activities are damaging productive habitats of the system. The once influential Apalachicola oyster fishery remains in disarray following a series of natural disasters and poor management practices. There is a growing problem with the deliberate obstruction of the generation and use of scientific data to determine management policies by various state and federal agencies. The substitution of public relations activities for the development of needed scientific information concerning factors such as the importance of sustained freshwater input to estuaries is further evidence that even the most elaborate and well-conceived management plans can be reversed by political manipulations and short-sighted bureaucratic policies.

Cellulase activity of leaf litter and stream-dwelling, shredder macroinvertebrates

The magnitude and temporal variability of exocellulase (β-1,4-exoglucanase) activity in leaf litter and guts of shredding macroinvertebrates was determined over one year in four streams in Virginia, USA. The streams flowed in three physiographic provinces and hence varied as to geomorphology, hydrology, water chemistry and riparian landscape. No significant difference in exocellulase activity occurred between streams over the year. Considerable temporal variation in activity did occur in all streams, with peaks in autumn-early winter and again in spring, corresponding to the primary periods of input of fresh allochthonous organic matter. Litter bag studies showed that peak exocellulase activity occurred after about one month of processing. Exocellulase activity in the guts of shredders was generally correlated with activity in their detrital food, suggesting that gut enzyme activity was acquired.

The Influence of Afforestation on Upland Soils: The Use of ‘Bomb 14C’ Enrichment as a Quantitative Tracer for Changes in Organic Status

A series of soil samples were collected in November 1984 from five stands of Sitka spruce planted at recorded times between 1951 and 1968. Within a comprehensive program of ecologic and biogeochemical analyses, natural 14C measurements on selected organic components of the 0 to 5cm soil horizons serve to quantify progressive changes induced in the organic carbon inventory and relative to that of the original grassland. Points of particular interest are: 1) an enhanced input of fresh organic matter in the years immediately following planting; this, in parallel with a net decrease in the total carbon content of the topsoil; 2) this freshly introduced carbon predominates in the soil profile even after 30 years of afforestation; 3) during the 15- to 30-year growth period, the soil carbon content remains constant but progressive changes occur in its biogeochemical composition and rate of turnover.