Shallow-water benthic and pelagic metabolism:

Pelagic primary production and benthic and pelagic aerobic metabolism were measured monthly at one site in the estuarine plume region of the nearshore continental shelf in the Georgia Bight. Benthic and water-column oxygen uptake were routinely measured and supplemented with seasonal measures of total carbon dioxide flux. Average respiratory quotients were 1.18:1 and 1.02:1 for the benthos and water column, respectively. Benthic oxygen uptake ranged from 1.23 to 3.41 g O₂ m^-2 d^-1 and totalled 756 g O₂ m^-2 over an annual period. Water column respiration accounted for 60% of total system metabolism. Turnover rates of organic carbon in sediment and the water column were 0.09 to 0.18 yr^-1 and 6.2 yr^-1, respectively. Resuspension appeared to control the relative amounts of organic carbon, as well as the sites and rates of organic matter degradation in the benthos and water column. Most of the seasonal variation in benthic and pelagic respiration could be explained primarily by temperature and secondarily by primary productivity. On an annual basis, the shelf ecosystem appeared to be heterotrophic; primary production was 73% of community metabolism, which was 749 g C m^-2 yr^-1. The timing of heterotrophic periods through the year appeared to be closely related to both river discharge and the periodicity of growth and death of marsh macrophytes in the adjacent estuary. The results of this study support the estuarine outwelling hypothesis of Odum (1968).This is Contribution No. 530 from the University of Georgia Marine Institute. This work was supported by the Georgia Sea Grant College Program maintained by the National Oceanic and Atmospheric Administration, US Department of Commerce     

Seasonal variations of organic-carbon and nutrient transport through a tropical estuary (Tsengwen) in southwestern Taiwan

This paper reports the fluvial fluxes and estuarine transport of organic carbon and nutrients from a tropical river (Tsengwen River), southwestern Taiwan. Riverine fluxes of organic carbon and nutrients were highly variable temporally, due primarily to temporal variations in river discharge and suspended load. The sediment yield of the drainage basin during the study period (1995–1996, 616 tonne km^–2 year^–1) was ca. 15 times lower than that of the long-term (1960–1998) average (9379 tonne km² year^–1), resulting mainly from the damming effect and historically low record of river water discharge (5.02 m³ s^–1) in 1995. The flushing time of river water in the estuary varied from 5 months in the dry season to >4.5 days in the wet season and about 1 day in the flood period. Consequently, distributions of nutrients, dissolved organic carbon (DOC) and particulate organic carbon (POC) were of highly seasonal variability in the estuary. Nutrients and POC behaved nonconservatively but DOC behaved conservatively in the estuary. DOC fluxes were generally greater than POC fluxes with the exception that POC fluxes considerably exceeded DOC fluxes during the flood period. Degradation of DOC and POC within the span of flushing time was insignificant and may contribute little amount of CO₂ to the estuary during the wet season and flood period. Net estuarine fluxes of nutrients were determined by riverine fluxes and estuarine removals (or additions) of nutrients. The magnitude of estuarine removal or addition for a nutrient was also seasonally variable, and these processes must be considered for net flux estimates from the river to the sea. As a result, nonconservative fluxes of dissolved inorganic phosphorus (DIP) from the estuary are –0.002, –0.09 and –0.59 mmol m^–2 day^–1, respectively, for dry season, wet season and flood period, indicating internal sinks of DIP during all seasons. Due to high turbidity and short flushing time of estuarine water, DIP in the flood period may be derived largely from geochemical processes rather than biological removal, and this DIP should not be included in an annual estimate of carbon budget. The internal sink of phosphorus corresponds to a net organic carbon production (photosynthesis–respiration, p–r) during dry (0.21 mmol m^–2 day^–1) and wet (9.5 mmol m^–2 day^–1) seasons. The magnitude of net production (p–r) is 1.5 mol m^–2 year^–1, indicating that the estuary is autotrophic in 1995. However, there is a net nitrogen loss (nitrogen fixation–denitrification < 0) in 1995, but the magnitude is small (–0.17 mol m^–2 year^–1).     

Community metabolism of intertidal flats in the Ems-Dollard estuary

To obtain an insight into the flux of carbon through intertidal sediments of the Ems-Dollard estuary, the annual cycles of gross benthic primary production and community respiration were measured at six stations, together with a set of environmental parameters. In a stepwise multiple regression analysis it was shown that temperature alone and temperature plus viable bacteria explained 50 and 70% respectively of the observed variation in community respiration. Other variables, including the rate of primary production and amount of organic carbon in the sediment were less important. The rate of primary production could not be fitted adequately into a multiple regression equation. The annual values of community respiration (177–794 gO₂·m^-2·yr^-1) and primary production (82–628 gO₂·m^-2·yr^-1) were within the range of published values. except for one station in the vicinity of a wastewater outfall, which had an extreme production (average 984 gO₂·m^-2·yr^-1). At four stations, annual community respiration exceeded primary production by 40%. It is concluded that the main carbon flux within the sediment, from CO₂ to benthic primary producers, to benthic consumers and from there to CO₂ again,was completed within a month or so, leaving untouched the large bulk of organic matter within the sediment. Possible effects of wastewater discharges on community metabolism are discussed.Publication No. 43 of the project Biological Research in the Ems-Dollard Estuary     

Methane Production in River and Lake Sediments in Taiwan

To investigate the relationship between methane production in the sediments and pollution of the river and lake, biochemical oxygen demand (BOD) and chemical oxygen demand (COD) of the water sample, organic matter content and methane production of the sediment were measured. Experimental results indicated that BOD, COD and organic matter contents were low in Bei-tan Lake, the I-lan River and reservoirs; and methane production of these sediments ranged from 0.24 to 1.06 mg L- 1. However, BOD, COD and organic matter contents were high in the Hsin-dan River, Keelung River, drainage river of Taoyuan County, park pond and fishery pond. Methane production of these sediments was between 11.75 and 54.54 mg L-1. Sediments of drain river and fishery pond had high methane production, at 25.41 to 54.54 mg methane L. Methane production of sediments had a good correlation with BOD, COD and organic matter contents. Methane production was proportional to the increment in incubation temperature from 12 to 40C.     

苏州河底泥对上复水水质污染影响

研究了上海市苏州河底泥中有机物及营养盐释放对上复水水质的影响,分析了微生物与底栖生物底泥再悬浮对底泥释放过程的影响。研究表明,底泥中化学需氧量与水体中的化学需氧量成正比,底泥中生化需氧量与水体中的生化需氧量呈正比,再悬浮促进底泥中污染物向上复水体释放。底泥SOD与水体中DO成正比,底泥污染是影响苏州河水质的重要因素;对苏州河底泥进行疏浚工程可较好地提高水体中溶解氧的浓度、降低化学需氧量、生化需氧量及氨氮的浓度。     

Benthic oxygen uptake and carbon cycling under aphotic and resource-limiting conditions in a submarine cave

To establish relationships between organic input to the benthos and decreases in benthic population biomass and density, benthic oxygen uptake was measured in an oligotrophic submarine cave in the northwestern Mediterranean Sea (Marseille, France), on seven separate occasions in 1987, using an in situ bell-jar respirometer. Oxygen uptake was measured in both the outer twilight section and the dark inner section of the cave during an annual survey (seven recording periods from February 1987 to November 1988). The mean annual benthic oxygen uptake was 80.9 litres O₂ m^–2 yr^–1 for the twilight outer section and 15.5 litres O₂ m^–2 yr^–1 for the dark inner section. The results are discussed and the biogeochemical budget for particulate organic carbon at the sediment-water interface calculated. Respiration rates (expressed as carbon equivalents), together with previously published data on vertical fluxes and burial of organic carbon, revealed that anaerobic pathways accounted for 14% and aerobic pathways for 86% of the total benthic metabolism in the outer part of the cave. In the inner section of the cave, degradation of organic carbon occurred only through aerobic degradation, indicating a strongly carbon-limited ecosystem. The low respiration rates recorded in the dark section were similar to values recorded for some oligotrophic deep-sea environments (1 000 to 2 000 m). Such budgets are essential preliminary steps in order to accurately model benthic metabolic pathways. The determination of annual fluxes linked to the acquisition of long-term data will yield better knowledge of the recycling processes at the water-sediment interface.     

In situ respiration of benthic communities in Castle Harbor,Bermuda

In situ measurements of community respiration were made at two stations in Castle Harbor, Bermuda, during April and May, 1971. Total community respiration was 20.67 and 19.11 ml O₂ m^-2 h^-1 at Stations 1 and 2, respectively, in April. In May, respiration increased with water temperature to 26.99 and 24.56 ml O₂ m^-2 h^-1. Significant differences (P<0.05) existed between stations and sampling periods. Bacterial respiration was estimated from sediment treatment with streptomycin-SO₄. Values ranged from 7.71 to 8.72 ml O₂ m^-2 h^-1 in April and May, respectively. No significant difference existed between sampling periods or stations. No detectable chemical O₂ demand of the sediment, determined by a formalin treatment, was found. Total community respiration was further compartmentalized into macrofaunal, meiofaunal, and microfaunal-microfloral components. Both the macrofaunal and meiofaunal respiration was negligible compared to that estimated for the microfaunal-microfloral component.Contribution No. 2708 from the Woods Hole Oceanographic Institution, and Contribution No. 552 from the Bermuda Biology Station. This study was supported in part by National Science Foundation Grants GZ 1508 and GB 16161.     

不同溶氧条件下九龙江口湿地沉积物一水界面氨氮释放与氧化规律

摘要：沉积物中氨氮（NH4^＋-N）的释放与氧化是河口湿地生态系统氮素生物地球化学循环的关键过程。本文通过室内模拟,构建饱和（BH）、好氧（HY）、缺氧（QY）和厌氧（YY）等四种上覆水溶氧（DO）条件,研究九龙江口湿地两种沉积物（红树林、光滩）中NH4^＋-N在沉积物-水界面的释放与氧化规律。结果表明,不同溶氧条件下,两种沉积物氨氮的释放、氧化存在显著差异。首先,红树林沉积物上覆水NH4^＋-NN的累积释放量是光滩沉积物的1．9-4．5倍,其中红树林沉积物上覆水NH4LN释放量分别达到1．64mg（BH）、2．07mg（HY）、3．47mg（QY）和3．20mg（YY）,而光滩沉积物则分别为0．85mg（BH）、1．00mg（HY）、0．77mg（QY）和1．27mg（YY）。在较高DO条件下两种沉积物NH。’一N均呈低释放状态,而在较低DO条件下则呈高释放状态。另外,四种溶氧条件下红树林沉积物NH4^＋-NN的释放速率（N43．73-78．51mg-m^-2-d^-1）和氧化速率（N26．19-40．68mg-m^-2-d^-1）均高于光滩（分别为N14．50-19．22mg-m^-2-d^-1和N8．89-22．53mg-m^-2-d^-1）,原因可能是红树林沉积物微生物种类丰富,群落多样性更高,矿化和硝化作用强烈。本文明晰了不同溶氧条件下河口红树林湿地沉积物NH4^＋-N的迁移转化过程,可促进滨海湿地的生态保护以及近海水域富营养化的控制。     

Evaluating the seasonal changes of some water quality parameters of the Buyuk Melen River Basin (Duzce, Turkey)

In this study, some heavy metal concentrations (Pb, Zn, Fe, Cr, Cu), suspended sediment, chemical oxygen demand (COD), biological oxygen demand (BOD), cyanide, phenol, fecal coliform and total coliform water parameters were determined in the streams (Kucuk Melen, Asarsuyu, Ugursuyu, Buyuk Melen and Aksu) of Buyuk Melen Watershed that provides drinking water to Istanbul in Western Black Sea Region of Turkey. Measurements of water quality parameters were done monthly in eleven separate stations (4 in Kucuk Melen Stream, 1 in Asarsuyu Stream, 1 in Ugur Stream, 1 in Aksu Stream and 4 in Buyuk Melen Stream) from August 2001 to August 2002. The seasonal changes in water quality parameters were evaluated statistically. The results, the parameters, COD, BOD, Pb, Zn, Fe, Cr, Cu, cyanide, fecal coliform, total coliform and suspended sediment showed significant differences among seasons and streams (ANOVA; P <0.05). According to Turkish Standarts (TS) 266, European Union (EU) and World Health Organization (WHO) criteria, the maximum values of each parameter in streams within the Buyuk Melen watershed are recorded and evaluated in this study.     

Diurnal variation of nitrogen cycling in coastal,marine sediments

A closed chamber technique was developed to determine the emission of microbially produced N₂O from an estuarine sediment. A diurnal variation was observed; maximum emissions of 0.4 to 4.0 mol N₂O–N m^-2 h^-1 were recorded at night whereas the rates were low or even negative, -0.4 to 0.4 mol N₂O–N m^-2 h^-1, during the day. The bacterial denitrification located in the uppermost centimeter was apparently the major source of the emitted N₂O. The diurnal emission pattern was thus inversely related to the O₂ availability at the sediment surface; in the dark, the lack of O₂ production by benthic photosynthesis allowed the denitrification to occur closer to the sediment-water interface and was likely to enhance the release of N₂O to the water. The daily averages for the emission were about 40 mol N₂O–N m^-2 d^-1 for three investigation periods in autumn (November), winter (February) and spring (April), whereas no significant emission was recorded in the NO ₃ ^- -depleted sediment in early summer (June). In this estuary, the N₂O emissions from the sediment were significant contributions to the overall release of N₂O to the atmosphere.     

Energy flow through the benthos in a Scottish Sea Loch

Analysis of material collected in settlement traps at regular intervals over a period of a year gave an estimate of the annual organic input to the bottom sediment of about 28 gC/m² year, which is a little less than one third of the primary production in the overlying water column. The aerobic benthic community metabolism, estimated from in situ respiration measurements, was not significantly different from the carbon input. The rate of release of ammonia from the sediment was also measured in situ and would be sufficient to supply the greater part of the required input of inorganic nitrogen for photosynthesis in the water column.     

Effect of elevated temperature on aerobic respiration of coral recruits

Metabolic rates provide a valuable means to assess the condition of early life stages of scleractinians, but their small biomass creates a signal-to-noise problem in a confined respirometer. To avoid this problem, measurements of the oxygen diffusion boundary layer (DBL) and Ficks first law were used to calculate the respiration rate of coenosarc tissue on recruits (i.e., colonies 5–14 mm diameter) of Porites lutea (Edwards and Haime, 1860) exposed to two temperatures at a flow speed of 0.6 cm s^–1. All experiments were completed in Moorea, French Polynesia, between November and December 2003. At 26.8°C, the DBL was 565±55 µm thick, the oxygen saturation adjacent to the tissue was 80±3%, and the mean respiration of the coenosarc was 1.2±0.1 µl O₂ cm^–2 h^–1 (all values mean ± SE, n=10). Exposure to 29.7°C for 24–48 h did not affect the DBL thickness but significantly reduced the oxygen saturation adjacent to the tissue (to 74%) and increased the mean respiration rate by 35%. As the small corals differed slightly in size, in a uniform flow speed they experienced dissimilar flow environments as characterized by the Reynolds number (Re), thereby creating the opportunity to test the flow dependency of respiration. At 26.8°C, respiration and Re were unrelated, but at 29.7°C, the relationship was positive and statistically significant. Thus, respiration of small corals may not be mass transfer limited at low temperature, but relatively small increases in temperature may result in an increased metabolic rate leading to mass transfer limitation and flow-dependent rates of respiration.Communicated by J.P. Grassle, New Brunswick     

Effect of low dissolved oxygen concentrations on behavior and predation rates on red sea bream Pagrus major larvae by the jellyfish Aurelia aurita and by juvenile Spanish mackerel Scomberomorus niphonius

A shift in outcomes of predator-prey interactions in plankton community may occur at sublethal dissolved oxygen concentrations that commonly occur in coastal waters. Laboratory experiments were conducted to investigate how a decline in dissolved oxygen concentration alters the predation rate on fish larvae by two estuarine predators. Behavior and consumption of larval fish by moon jellyfish Aurelia aurita (103.1±12.4 mm in bell diameter) and by a juvenile piscivore, Spanish mackerel Scomberomorus niphonius (30.1±2.1 mm in standard length: SL), were observed under four oxygen concentration treatments (1, 2 and 4 mg l^–1 and air-saturated: 5.8 mg l^–1). Larvae of a coastal marine fish species, red sea bream Pagrus major (7.21±0.52 mm SL), were used as prey for the experiment. Bell contraction rate of the jellyfish did not vary among the oxygen concentrations tested, indicating a tolerance to low oxygen concentration. Gill ventilation rate of the Spanish mackerel increased and swimming speed decreased as the oxygen concentration decreased, indicating that oxygen concentrations 4 mg l^–1 are physiologically stressful for this species. The number of larvae consumed in 15 min. by jellyfish increased whereas those consumed by Spanish mackerel decreased with the decrease in oxygen concentration. Low oxygen concentrations that are commonly observed in coastal waters of Japan during summer have the potential to increase the relative importance of jellyfish as predator of fish larvae and to change the importance of alternative trophic pathways in estuarine ecosystems.Communicated by T. Ikeda, Hakodate     

Separating the effects of partial submergence and soil oxygen demand on plant physiology

In wetlands, a distinct zonation of plant species composition occurs along moisture gradients, due to differential flooding tolerance of the species involved. However, "flooding" comprises two important, distinct stressors (soil oxygen demand [SOD] and partial submergence) that affect plant survival and growth. To investigate how these two flooding stressors affect plant performance, we executed a factorial experiment (water depth x SOD) for six plant species of nutrient-rich and nutrient-poor conditions, occurring along a moisture gradient in Dutch dune slacks. Physiological, growth, and biomass responses to changed oxygen availability were quantified for all species. The responses were consistent with field zonation, but the two stressors affected species differently. Increased SOD increased root oxygen deprivation, as indicated by either raised porosity or increased alcohol dehydrogenase (ADH) activity in roots of flood-intolerant species (Calamagrostis epigejos and Carex arenaria). While SOD affected root functioning, partial submergence tended more to reduce photosynthesis (as shown both by gas exchange and 13C assimilation), leaf dark respiration, 13C partitioning from shoots to roots, and growth of these species. These processes were especially affected if the root oxygen supply was depleted by a combination of flooding and increased SOD. In contrast, the most flood-tolerant species (Juncus subnodulosus and Typha latifolia) were unaffected by any treatment and maintained high internal oxygen concentrations at the shoot : root junction and low root ADH activity in all treatments. For these species, the internal oxygen transport capacity was well in excess of what was needed to maintain aerobic metabolism across all treatments, although there was some evidence for effects of SOD on their nitrogen partitioning (as indicated by 865N values) and photosynthesis. Two species intermediate in flooding tolerance (Carex nigra and Schoenus nigricans) responded more idiosyncratically, with different parameters responding to different treatments. These results show that partial submergence and soil flooding are two very different stressors to which species respond in different ways, and that their effects on physiology, survival, and growth are interactive. Understanding species zonation with water regimes can be improved by a better appreciation of how these factors affect plant metabolism independently and interactively.     

The capacity of the filter-feeding bivalve Mya arenaria L. to affect water transport in sandy beds

Benthic filter feeding macrofauna organisms may be an important factor linking sediment and water column. Transport of water and concomitantly of suspended matter is directly related to the size of the benthic filter feeding population. This paper aims to determine the potential for water transport by the bivalve Mya arenaria along a coastal stretch of roughly 100 km length in the southern Baltic Sea. Quantification of population filtration rates specific to the area is based on distribution, abundance and biomass of M. arenaria and calculated according to previously published filtration rate–biomass relations. Calculated rates range up to >8 m³ m^–2 day^–1 (at 5–20 m water depth in sandy sediment) with the potential to locally process a volume of water equivalent to the water column within <1 day. Data from 1991–2002 at one site suggest that the area-specific potential population filtration rate remains remarkably constant in time despite changes in population structure of M. arenaria. The related impact on pore water exchange within the permeable sediment associated with the leakage of water from the gape of M. arenaria valves is discussed.Communicated by L. Hagerman, Helsingør     

Root respiration and oxygen flux in salt marsh grasses from different elevational zones

Plants growing in waterlogged environments are subjected to low oxygen levels around submerged tissues. While internal oxygen transport has been postulated as an important factor governing flooding tolerance, respiration rates and abilities to take up oxygen under hypoxic conditions have been largely ignored in plant studies. In this study, physiological characteristics related to internal oxygen transport, respiration, and oxygen affinity were studied in low intertidal marsh species (Spartina alterniflora and S. anglica) and middle to high intertidal species (S. densiflora, S. patens, S. foliosa, a S. alterniflora × S. foliosa hybrid, S. spartinae, and Distichlis spicata). These marsh plants were compared to the inland species S. pectinata and the crop species rice (Oryza sativa), corn (Zea mays), and oat (Avena sativa). Plants were grown in a greenhouse under simulated estuarine conditions. The low marsh species S. anglica was found to transport oxygen internally at rates up to 2.2 μmol O₂ g fresh root weight⁻¹ h⁻¹. In contrast, marsh species from higher zones and crop species were found to transport significantly less oxygen internally, although rice plants were able to transport 1.4 μmol g⁻¹ h⁻¹. Under hypoxic conditions, low marsh species were better able to remove dissolved oxygen from the medium compared to higher marsh species and crops. The oxygen concentration at which respiration rates declined due to limited oxygen (P _crit) was significantly lower in low marsh species compared to inland and crop species; P _crit ranged from <4 μM O₂ in the low marsh species S. anglica up to 20 μM in the inland species corn. Flooding-sensitive crop species had significantly higher aerobic respiration rates compared to flooding-tolerant species in this study. Crop species took up 3.6–6.7 μmol O₂ g⁻¹ h⁻¹ while all but one marsh species took up <3.5 μmol O₂ g⁻¹ h⁻¹. We conclude that oxygen transport, aerobic demand, and oxygen affinity all play important and interrelated roles in flood tolerance and salt marsh zonation.     

Sensitivity of benthic community respiration and primary production to changes in temperature and light

In-situ measurements of benthic community respiration and primary production on an intertidal sandflat in Nova Scotia, Canada were used to test the hypothesis that community responses to light and temperature were similar within and between seasons. Multiple regression indicated that mean incubation temperature explained 57% of the variance in total sediment oxygen demand (TOD). The logarithmic relationship between TOD and temperature (Q₁₀=6.5) was not significantly different between fall and spring, suggesting no acclimation within season. Chemical oxygen demand measured in formalin-poisoned cores averaged 30% of TOD. Microalgal gross primary production (GROSS) was measured as oxygen production in light cores. Mean incubation temperature and sediment chlorophylla explained 56% of the variance. The linear relationship between GROSS and temperature had Q₁₀=2.0. When production was normalized to chlorophylla [GROSS(SP)], seasonal production-temperature curves were significantly different. The spring curve had Q₁₀=3.3; in the fall, production and temperature were not related. GROSS(SP)-light curves derived from Plexiglas shade experiments in the field were linear and not significantly different between fall and spring. Temperature alone was a better predictor of GROSS(SP) than light, even when P/I curves were adjusted for temperature. One can therefore model community respiration and photosynthesis at this site using daily averages in temperature, which are then summed over longer time scales to estimate monthly or seasonal rates.     

Sediment nutrient flux in a coastal lake impacted by diverted Mississippi River water

The internal nutrient load from bottom sediment to the water column of a Louisiana Barataria Basin lake (Lake Cataouatche) receiving diverted Mississippi River water was determined. Dissolved reactive phosphorus (DRP), ammonium (NH₄-N) and nitrate (NO₃-N) flux from sediment to water column were measured. The DRP flux averaged-0.22 mg m^-2 d^-1 under aerobic water column conditions, as compared with that 3.29 mg m^-2 d^-1 under anaerobic conditions. The average NH₄-N released under anaerobic conditions (1.42 mg m^-2 d^-1) was significantly greater than rates under aerobic conditions (-0.02 mg m^-2 d^-1), indicating a strong relationship between nutrient flux and oxygen availability in the water column. The average NO₃-N flux was 2.13 mg m^-2 d^-1 under aerobic conditions as compared with-0.24 mg m^-2 d^-1 under anaerobic conditions in the sediment-water column. When the water column maintained under anaerobic conditions was switched to aerobic conditions, the DRP, NH₄-N, and NO₃-N concentrations in overlying water decreased rapidly over a short period of time. The mean annual internal DRP and NH₄-N load from the sediment to the overlying water was estimated to be 69.26 and 29.9 tonnes (Mg) yr^-1 respectively, which represents a significant portion of the total nutrient load to the Lake. Results demonstrate that the internal flux of nutrients from sediments can contribute a significant portion of the total nutrient load to the water column and should be considered in decisions on impact of nutrient in diverted Mississippi River on water quality of Barataria Basin.     

A study on the landfill leachate and its impact on the groundwater quality of the greater area

Characterisation of the leachate originating from the Ano Liosia landfill (situated in Attica region, Greece) as well as assessment on the quality of the local aquifer were carried out. The experimental results showed that most of the parameters examined in the leachate samples such as colour, conductivity, TS, COD, NH₃–N, PO₄–P, SO₄ ^2–, Cl^–, K⁺, Fe and Pb were found in high levels. The organic load was quite high since the COD concentrations were in the range of 3250–6125mgL^–1. In addition, the low BOD/COD ratio (0.096–0.195), confirmed that the majority of this organic matter is not easily biodegradable. The groundwater near the landfill site was characterised as not potable and not suitable for irrigation water, since most of the physical and chemical parameters examined – such as colour, conductivity, DS, hardness, Cl^–, NH₃–N, COD, K⁺, Na⁺, Ca²⁺, Fe, Ni and Pb exceeded the permissible limits given by EE, EPA and the Greek Ministry of Agriculture. Furthermore, this study presents the application of the hydrologic evaluation of landfill performance (HELP) model for the determination of the yearly leakage from the base of the landfill after the final capping.     

Benthic community respiration in the N.W. Atlantic Ocean: in situ measurements from 40 to 5200 m

Benthic community respiration was measured in situ at 9 stations along the Gay Head-Bermuda transect from depths of 40 to 5200 m. Three methods were used; bell jar respirometers, grab respirometers, and free vehicle respirometers. Benthic community respiration rates spanned three orders of magnitude, decreasing from 21.5 ml O₂ m^-2 h^-1 at 40 m in November to 0.02 ml O₂ m^-2 h^-1 at 5200 m. Rates decreased two orders of magnitude between 40 and 1800 m and then significantly declined again between the continental rise (3650 m) and the abyssal plain stations. Predictive equations for benthic community respiration along the transect reflect a strong correlation with depth of water. Of lesser significance are the correlations with water temperature, dissolved oxygen, benthic animal biomass, surface primary productivity and sediment organic matter. Calculations show that annual benthic respiration can utilize 1 to 2% of the surface primary productivity. Of the 2 to 7% organic carbon fixed at the surface which supposedly reaches the bottom, only 15 to 29% is utilized by the benthic community at 2200, 3000, and 3650 m. The energy requirements of other biological components of deep-sea benthic communities, such as benthopelagic and macro-epibenthic animals, not included in these measurements, must also be considered in calculating a balance of carbon.Contribution from Scripps Institution of Oceanography.