Ecological studies on high-rate biological filters with special reference to microbial biosynthesis and nitrification

Pilot scale studies of high rate filtration were initiated to assess its potential as either a primary 'roughing' filter to alleviate the seasonal overloading of low rate filters on Hereford sewage treatment works - caused by wastes from cider production - or as a two stage high rate process to provide complete sewage treatment. Four mineral and four plastic primary filter media and two plastic secondary filter media were studied. The hydraulic loading applied to the primary plastic media (11.2 m3 /m3 .d) was twice that applied to the mineral media. The plastic media removed an average around 66 percent and the mineral media around 73 percent of the BOD applied when the 90 percentile BOD concentration was 563 mg/1. At a hydraulic loading of 4 m3 /m3 .d the secondary filters removed most of the POD from partially settled primary filter effluents, with one secondary effluent satisfying a 25 mg/1 BOD and 30 mg/1 SS standard. No significant degree of nitrification was achieved. Fungi dominated the biological film of the primary filters, with invertebrate grazers having little influence on film levels. Ponding did not arise, and modular media supported lower film levels than random-fill types. Secondary filter film levels were low, being dominated by bacteria. The biological loading applied to the filters was related to sludge dewaterability, with the most readily conditionable sludges produced by filters supporting heavy film. Sludges produced by random-fill media could be dewatered as readily as those produced by low rate filters treating the same sewage. Laboratory scale studies showed a relationship between log effluent BOD and nitrification achieved by biological filters. This relationship and the relationship between BOD load applied and removed observed in all filter media could he used to optimise operating conditions required in biological filters to achieve given effluent BOD and ammoniacal nitrogen standards.

The influence of environment on foliose lichen growth and its biological significance

Radial growth and growth in mass of lichens is influenced by climatic and microclimatic factors and also by substratum factors such as rock and bark texture, chemistry, and nutrient enrichment. Seasonal fluctuations in growth, as measured by radial growth rate (RaGR) per month, often correlate best with average or total rainfall, the number of rain days, or rainfall in a specific season. Temperature is also considered to be an important climatic factor in some studies. Interactions between microclimatic factors and especially light intensity, temperature, and moisture are the most important in determining local annual growth rates. The physical and chemical nature of the substratum has a profound influence on the growth of foliose lichens. Hence, the effects of texture, porosity, rate of drying, and the physical changes of the substratum on growth are likely to influence lichen distributions. Bird droppings may influence growth and survival by smothering the thalli, altering the pH, or adding inhibitory and stimulatory compounds. Nitrogen and phosphate availability may also influence growth. Chemical factors may also have an important influence on lichens of maritime rocks, the effect of salinity and calcium ions being of particular importance. Zinc, copper, and mercury may also be important in lichen growth as they have been shown to affect the chlorophyll content of lichen algae. Effects of environmental factors on growth influence the competitive ability of lichens thus influencing their ecology and distribution.

Carbon and nitrogen stable isotopic patterns in South Florida coastal ecosystems: Modern and paleoceanographic perspectives

Long term management plans for restoration of natural flow conditions through the Everglades increase the importance of understanding potential nutrient impacts of increased freshwater delivery on coastal biogeochemistry. The present study sought to increase understanding of the coastal marine system of South Florida under modern conditions and through the anthropogenic changes in the last century, on scales ranging from individual nutrient cycle processes to seasonal patterns in organic material (OM) under varying hydrodynamic regime, to century scale analysis of sedimentary records. In all applications, carbon and nitrogen stable isotopic compositions of OM were examined as natural recorders of change and nutrient cycling in the coastal system. ^ High spatial and temporal variability in stable isotopic compositions were observed on all time scales. During a transient phytoplankton bloom, δ 15N values suggested nitrogen fixation as a nutrient source supporting enhanced productivity. Seasonally, particulate organic material (POM) from ten sites along the Florida Reef Tract and in Florida Bay demonstrated variable fluctuations dependent on hydrodynamic setting. Three separate intra-annual patterns were observed, yet statistical differences were observed between groupings of Florida Bay and Atlantic Ocean sites. The POM δ 15N values ranged on a quarterly basis by 7‰, while δ 13C varied by 22‰. From a sediment history perspective, four cores collected from Florida Bay further demonstrated the spatial and temporal variability of the system in isotopic composition of bulk OM over time. Source inputs of OM varied with location, with terrestrial inputs dominating proximal to Everglades freshwater discharge, seagrasses dominating in open estuary cores, and a marine mixture of phytoplankton and seagrass in a core from the boundary zone between Florida Bay and the Gulf of Mexico. Significant shifts in OM geochemistry were observed coincident with anthropogenic events of the 20th century, including railroad and road construction in the Florida Keys and Everglades, and also the extensive drainage changes in Everglades hydrology. The sediment record also preserved evidence of the major hurricanes of the last century, with excursions in geochemical composition coincident with Category 4-5 storms. ^

Intra- and interannual variability in seagrass carbon and nitrogen stable isotopes from south Florida, a preliminary study

δ13C and δ15N values were determined for the seagrassThalassia testudinum at four permanent seagrass monitoring stations in southFlorida, USA, through a quarterly sampling program over 3-years (1996–1998). All sites are seagrass beds with water depths of less than 6 m. Two sites are located on the Florida Bay side of the Florida Keys, and the other two sites are on the Atlantic side. The data analyzed over the 3 year study period display unique patterns associated with seasonal changes in primary productivity and potentially changes in the N and C pools. The mean carbon and nitrogenisotope values of T. testudinum from all four stations vary from −7.2 to −10.4‰ and 1.1 to 2.2‰, respectively. However, certain stations displayed anomalously depleted nitrogenisotope values (as low as −1.2‰). These values may indicate that biogeochemical processes like N fixation, ammonification and denitrification cause temporal changes in the isotopic composition of the source DIN. Both δ13C and δ15N values displayed seasonal enrichment-depletion patterns, with maximum enrichment occurring during the summer to early fall. The intra-annual variations of δ13C values from the different stations ranged from about 1 to 3.5‰; whereas variations in δ15N ranged from about 1 to 4.9‰. Certain sites showed a positive relationship between isotope values and productivity. These data indicate δ13C values display a high degree of seasonal variability as related to changes in productivity. δ15N values show clear intra-annual variations, but the observed changes do not necessarily follow a distinct seasonal cycle, indicating that changes in DIN will need further investigation.

Biogeochemistry of Nitrogen Across the Everglades Landscape

Compared to phosphorus (P), nitrogen (N) has received little attention across the Everglades landscape. Despite this lack of attention, N plays important roles in many Everglades systems, including being a significant pollutant in Florida Bay and the Gulf of Mexico, the limiting nutrient in highly P-impacted areas, and an important substrate for microbial metabolism. Storage and transport of N throughout the Everglades is dominated by organic forms, including peat soils and dissolved organic N in the water column. In general, N sources are highest in the northern areas; however, atmospheric deposition and active N2 fixation by the periphyton components are a significant N source throughout most systems. Many of the processes involved in the wetland N cycle remain unmeasured for most of the Everglades systems. In particular, the lack of in situ rates for N2 fixation and denitrification prevent the construction of system-level budgets, especially for the Southern mangrove systems where N export into Florida Bay is critical. There is also the potential for several novel N processes (e.g., Anammox) with an as yet undetermined importance for nitrogen cycling and function of the Everglades ecosystem. Phosphorus loading alters the N cycle by stimulating organic N mineralization with resulting flux of ammonium and DON, and at elevated P concentrations, by increasing rates of N2 fixation and N assimilation. Restoration of hydrology has a potential for significantly impacting N cycling in the Everglades both in terms of affecting N transport, but also by altering aerobic-anaerobic transitions at the soil-water interface or in areas with seasonal drawdowns (e.g., marl prairies). Based on the authors’ understanding of N processes, much more research is necessary to adequately predict potential impacts from hydrologic restoration, as well as the function of Everglades systems as sinks, sources, and transformers of N in the South Florida landscape.

Biogeochemical Contributions of Tree Islands to Everglades Wetland Landscape Nitrogen Cycling During Seasonal Inundation

In the Florida Everglades, tree islands are conspicuous heterogeneous elements in the herbaceous wetland landscape. We characterized the biogeochemical role of a seasonally flooded tree island during wet season inundation, specifically examining hydrologically mediated flows of nitrogen (N) and N retention by the tree island. We estimated ecosystem N standing stocks and fluxes, soil and litter N transformation rates, and hydrologic fluxes of N to quantify the net ecosystem N mass flux. Results showed that hydrologic sources of N were dominated by surface water loads of nitrate (NO3) and ammonium (NH4). Nitrate immobilization by soils and surficial leaf litter was an important sink for surface water dissolved inorganic N (DIN). We estimated that the net annual DIN retention by a seasonally flooded tree island was 20.5 ± 5.0 g m−2 during wet season inundation. Based on the estimated tree island surface water DIN loading rate, a seasonally flooded tree island retained 76% of imported DIN. As such, seasonally flooded tree islands have the potential to retain 55% of DIN entering the marsh landscape via upstream canal overland flow in the wet season. By increasing reactive surface area and DOC availability, we suggest that tree islands promote convergence of elements that enhance DIN retention. Tree islands of this region are thus important components of landscape-scale restoration efforts that seek to reduce sources of anthropogenic DIN to downstream estuaries.

Patterns of phosphorus, nitrogen and δ15N along a peat development gradient in a coastal mire, Panama

Differentiation of limiting nutrients within small spatial scales has been observed in coastal mangrove forests, but research on other tropical peatlands suggests it is a more widespread phenomenon. In the Changuinola mire of coastal Panama, oligotrophy was hypothesized to increase along a gradient of peat development (peat doming). Nutrient and carbon concentration of leaf tissue, soil, and soil porewater were characterised over a successive sequence of plant communities along the gradient. Soil phosphorus (P) and nitrogen (N) concentrations decreased from 1200 μg P g−1 and 27 mg N g−1 to 377 μg P g−1 and 22 mg N g−1 within 2.7 km into the mire interior. These changes coincided with an increase in soil and average leaf N:P molar ratios from 52–128 and 24–41, respectively. Soil P was strongly related to leaf P and soil N:P to foliar N:P. There was a wide range in δ15N values for canopy (4.0 to −9.4‰), Campnosperma panamense (4.0 to −7.8‰) and understorey (4.8 to −3.1‰) species. Foliar δ15N values of canopy species were strongly related to soil N:P, soil P and leaf P. The depleted foliar δ15N values appeared to be an effect of both the N atmospheric source and P limitation. Here, P limitation is likely associated with ombrotrophic conditions that developed as hydrologic inputs became dominated by precipitation.

The Importance of Dissimilatory Nitrate Reduction to Ammonium (DNRA) in the Nitrogen Cycle of Coastal Ecosystems

Until recently, it was believed that biological assimilation and gaseous nitrogen (N) loss through denitrification were the two major fates of nitrate entering or produced within most coastal ecosystems. Denitrification is often viewed as an important ecosystem service that removes reactive N from the ecosystem. However, there is a competing nitrate reduction process, dissimilatory nitrate reduction to ammonium (DNRA), that conserves N within the ecosystem. The recent application of nitrogen stable isotopes as tracers has generated growing evidence that DNRA is a major nitrogen pathway that cannot be ignored. Measurements comparing the importance of denitrification vs. DNRA in 55 coastal sites found that DNRA accounted for more than 30% of the nitrate reduction at 26 sites. DNRA was the dominant pathway at more than one-third of the sites. Understanding what controls the relative importance of denitrification and DNRA, and how the balance changes with increased nitrogen loading, is of critical importance for predicting eutrophication trajectories. Recent improvements in methods for assessing rates of DNRA have helped refine our understanding of the rates and controls of this process, but accurate measurements in vegetated sediment still remain a challenge.

Seawater carbonate chemistry and diatom Phaeodactylum tricornutum (CCMA 106) biological processes during experiments, 2010

CO2/pH perturbation experiments were carried out under two different pCO2 levels (39.3 and 101.3 Pa) to evaluate effects of CO2-induced ocean acidification on the marine diatom Phaeodactylum tricornutum. After acclimation (>20 generations) to ambient and elevated CO2 conditions (with corresponding pH values of 8.15 and 7.80, respectively), growth and photosynthetic carbon fixation rates of high CO2 grown cells were enhanced by 5% and 12%, respectively, and dark respiration stimulated by 34% compared to cells grown at ambient CO2. The half saturation constant (Km) for carbon fixation (dissolved inorganic carbon, DIC) increased by 20% under the low pH and high CO2 condition, reflecting a decreased affinity for HCO3- or/and CO2 and down-regulated carbon concentrating mechanism (CCM). In the high CO2 grown cells, the electron transport rate from photosystem II (PSII) was photoinhibited to a greater extent at high levels of photosynthetically active radiation, while non-photochemical quenching was reduced compared to low CO2 grown cells. This was probably due to the down-regulation of CCM, which serves as a sink for excessive energy. The balance between these positive and negative effects on diatom productivity will be a key factor in determining the net effect of rising atmospheric CO2 on ocean primary production.

Seawater carbonate chemistry and particulate organic particles during a semicontinuous batch culture experiment with Trichodesmium IMS101, 2007

Diazotrophic (N2-fixing) cyanobacteria provide the biological source of new nitrogen for large parts of the ocean. However, little is known about their sensitivity to global change. Here we show that the single most important nitrogen fixer in today's ocean, Trichodesmium, is strongly affected by changes in CO2 concentrations. Cell division rate doubled with rising CO2 (glacial to projected year 2100 levels) prompting lower carbon, nitrogen and phosphorus cellular contents, and reduced cell dimensions. N2 fixation rates per unit of phosphorus utilization as well as C:P and N:P ratios more than doubled at high CO2, with no change in C:N ratios. This could enhance the productivity of N-limited oligotrophic oceans, drive some of these areas into P limitation, and increase biological carbon sequestration in the ocean. The observed CO2 sensitivity of Trichodesmium could thereby provide a strong negative feedback to atmospheric CO2 increase.

Seawater carbonate chemistry and biological processes during experiments with Coccolithus braarudii, 2011

Ocean acidification and associated shifts in carbonate chemistry speciation induced by increasing levels of atmospheric carbon dioxide (CO2) have the potential to impact marine biota in various ways. The process of biogenic calcification, for instance, is usually shown to be negatively affected. In coccolithophores, an important group of pelagic calcifiers, changes in cellular calcification rates in response to changing ocean carbonate chemistry appear to differ among species. By applying a wider CO2 range we show that a species previously reported insensitive to seawater acidification, Coccolithusbraarudii, responds both in terms of calcification and photosynthesis, although at higher levels of CO2. Thus, observed differences between species seem to be related to individual sensitivities while the underlying mechanisms could be the same. On this basis we develop a conceptual model of coccolithophorid calcification and photosynthesis in response to CO2-induced changes in seawater carbonate chemistry speciation.