Benthic metabolism as an indicator of stream ecosystem health

We tested direct and indirect measures of benthic metabolism as indicators of stream ecosystem health across a known agricultural land-use disturbance gradient in southeast Queensland, Australia. Gross primary production (GPP) and respiration (R-24) in benthic chambers in cobble and sediment habitats, algal biomass (as chlorophyll a) from cobbles and sediment cores, algal biomass accrual on artificial substrates and stable carbon isotope ratios of aquatic plants and benthic sediments were measured at 53 stream sites, ranging from undisturbed subtropical rainforest to catchments where improved pasture and intensive cropping are major land-uses. Rates of benthic GPP and R-24 varied by more than two orders of magnitude across the study gradient. Generalised linear regression modelling explained 80% or more of the variation in these two indicators when sediment and cobble substrate dominated sites were considered separately, and both catchment and reach scale descriptors of the disturbance gradient were important in explaining this variation. Model fits were poor for net daily benthic metabolism (NDM) and production to respiration ratio (P/R). Algal biomass accrual on artificial substrate and stable carbon isotope ratios of aquatic plants and benthic sediment were the best of the indirect indicators, with regression model R-2 values of 50% or greater. Model fits were poor for algal biomass on natural substrates for cobble sites and all sites. None of these indirect measures of benthic metabolism was a good surrogate for measured GPP. Direct measures of benthic metabolism, GPP and R-24, and several indirect measures were good indicators of stream ecosystem health and are recommended in assessing process-related responses to riparian and catchment land use change and the success of ecosystem rehabilitation actions.

Phototrophic microendoliths bloom during coral "white syndrome"

Following rapid lesion progression of white syndrome in tabular Acropora spp., the white bare skeleton gradually changes to green, a result of endolithic algae blooms (primarily Ostreobium spp.). Endolithic algal biomass and chlorophyll concentration were found to be an order of magnitude higher in the green zone compared with healthy appearing parts of each colony. Chl b to Chl a ratio increased from 1:1.6 in the healthy area to 1:2 and 1:3.5 in the white exposed skeleton and green zones, respectively. These observations together with pulse amplitude modulated (PAM) fluorometry suggest photoacclimation of the endoliths in the green zone. Histopathological microscopy revealed that the endolithic algal filaments penetrate the coral tissue. This study highlights the interaction of endolithic algae with both the skeleton and host tissue. This may have a critical role in the processes that accompany the post-disease state in reef-building corals.

Drifting blooms of the endemic filamentous brown alga Hincksia sordida at Noosa on the subtropical east Australian coast

Since 2002, the usually uncommon endemic filamentous brown alga Hincksia sordida (Harvey) Silva (Ectocarpales, Phaeophyta) has formed nuisance blooms annually during spring/early summer at Main Beach, Noosa on the subtropical east Australian coast. The Hincksia bloom coincides with the normally intensive recreational use of the popular bathing beach by the local population and tourists. The alga forms dense accumulations in the surf zone at Main Beach, giving the seawater a distinct brown coloration and deterring swimmers from entering the water. Decomposing algae stranded by receding tides emit a nauseating sulphurous stench which hangs over the beach. The stranded algal biomass is removed from the beach by bulldozers. During blooms, the usually crowded Main Beach is deserted, bathers preferring to use the many unaffected beaches on the Sunshine Coast to the south of Main Beach. The bloom worsens with north-easterly winds and is cleared from Noosa by south easterly winds, observations which have prompted the untenable proposal by local authorities that the bloom is forming offshore of Fraser Island in the South Pacific Ocean. The Noosa River estuarine system/Laguna Bay is the more probable source of the bloom and the nutrient inputs into this system must be substantial to generate the high bloom biomass. Current mitigation procedures of removing the blooming alga off the beach with bulldozers treat the symptom, not the cause and are proving ineffective. Environmental management must be based on science and the Noosa bloom would benefit greatly from the accurate ecological data on which to base management options. (c) 2006 Elsevier Ltd. All rights reserved.

Pryolytic and kinetic study of Chlorella Vulgaris under isothermal and non-isothermal conditions

Algae are a new potential biomass for energy production but there is limited information on their pyrolysis and kinetics. The main aim of this thesis is to investigate the pyrolytic behaviour and kinetics of Chlorella vulgaris, a green microalga. Under pyrolysis conditions, these microalgae show their comparable capabilities to terrestrial biomass for energy and chemicals production. Also, the evidence from a preliminary pyrolysis by the intermediate pilot-scale reactor supports the applicability of these microalgae in the existing pyrolysis reactor. Thermal decomposition of Chlorella vulgaris occurs in a wide range of temperature (200-550°C) with multi-step reactions. To evaluate the kinetic parameters of their pyrolysis process, two approaches which are isothermal and non-isothermal experiments are applied in this work. New developed Pyrolysis-Mass Spectrometry (Py-MS) technique has the potential for isothermal measurements with a short run time and small sample size requirement. The equipment and procedure are assessed by the kinetic evaluation of thermal decomposition of polyethylene and lignocellulosic derived materials (cellulose, hemicellulose, and lignin). In the case of non-isothermal experiment, Thermogravimetry- Mass Spectrometry (TG-MS) technique is used in this work. Evolved gas analysis provides the information on the evolution of volatiles and these data lead to a multi-component model. Triplet kinetic values (apparent activation energy, pre-exponential factor, and apparent reaction order) from isothermal experiment are 57 (kJ/mol), 5.32 (logA, min-1), 1.21-1.45; 9 (kJ/mol), 1.75 (logA, min-1), 1.45 and 40 (kJ/mol), 3.88 (logA, min-1), 1.45- 1.15 for low, middle and high temperature region, respectively. The kinetic parameters from non-isothermal experiment are varied depending on the different fractions in algal biomass when the range of apparent activation energies are 73-207 (kJ/mol); pre-exponential factor are 5-16 (logA, min-1); and apparent reaction orders are 1.32–2.00. The kinetic procedures reported in this thesis are able to be applied to other kinds of biomass and algae for future works.

Intermediate pyrolysis and product identification by TGA and Py-GC/MS of green microalgae and their extracted protein and lipid components

The thermo-chemical conversion of green microalgae Chlamydomonas reinhardtii wild type (CCAP 11/32C), its cell wall deficient mutant C. reinhardtii CW15 (CCAP 11/32CW15) and Chlorella vulgaris (CCAP 211/11B) as well as their proteins and lipids was studied under conditions of intermediate pyrolysis. The microalgae were characterised for ultimate and gross chemical composition, lipid composition and extracted products were analysed by Thermogravimetric analysis (TG/DTG) and Pyrolysis-gaschromatography/mass-spectrometry (Py-GC/MS). Proteins accounted for almost 50% and lipids 16-22 % of dry weight of cells with little difference in the lipid compositions between the C. reinhardtii wild type and the cell wall mutant. During TGA analysis, each biomass exhibited three stages of decomposition, namely dehydration, devolatilization and decomposition of carbonaceous solids. Py-GC/MS analysis revealed significant protein derived compounds from all algae including toluene, phenol, 4-methylphenol, 1H-indole, 1H-indole-3methyl. Lipid pyrolysis products derived from C. reinhardtii wild type and C. reinhardtii CW15 were almost identical and reflected the close similarity of the fatty acid profiles of both strains. Major products identified were phytol and phytol derivatives formed from the terpenoid chain of chlorophyll, benzoic acid alkyl ester derivative, benzenedicarboxylic acid alkyl ester derivative and squalene. In addition, octadecanoic acid octyl ester, hexadecanoic acid methyl ester and hydrocarbons including heptadecane, 1-nonadecene and heneicosane were detected from C. vulgaris pyrolysed lipids. These results contrast sharply with the types of pyrolytic products obtained from terrestrial lignocellulosic feedstocks and reveal that intermediate pyrolysis of algal biomass generates a range of useful products with wide ranging applications including bio fuels.

Variable responses within epiphytic and benthic microalgal communities to nutrient enrichment

We examined the spatial extent of nitrogen (N) and phosphorus (P) limitation of each of the major benthic primary producer groups in Florida Bay (seagrass, epiphytes, macroalgae, and benthic microalgae) and characterized the shifts in primary producer community composition following nutrient enrichment. We established 24 permanent 0.25-m2 study plots at each of six sites across Florida Bay and added N and P to the sediments in a factorial design for 18 mo. Tissue nutrient content of the turtlegrass Thalassia testudinum revealed a spatial pattern in P limitation, from severe limitation in the eastern bay (N:P > 96:1), moderate limitation in two intermediate sites (approximately 63:1), and balanced with N availability in the western bay (approximately 31:1). P addition increased T. testudinum cover by 50-75% and short-shoot productivity by up to 100%, but only at the severely P-limited sites. At sites with an ambient N:P ratio suggesting moderate P limitation, few seagrass responses to nutrients occurred. Where ambient T. testudinum tissue N:P ratios indicated N and P availability was balanced, seagrass was not affected by nutrient addition but was strongly influenced by disturbance (currents, erosion). Macroalgal and epiphytic and benthic microalgal biomass were variable between sites and treatments. In general, there was no algal overgrowth of the seagrass in enriched conditions, possibly due to the strength of seasonal influences on algal biomass or regulation by grazers. N addition had little effect on any benthic primary producers throughout the bay. The Florida Bay benthic primary producer community was P limited, but P-induced alterations of community structure were not uniform among primary producers or across Florida Bay and did not always agree with expected patterns of nutrient limitation based on stoichiometric predictions from field assays of T. testudinum tissue N:P ratios.

Comparative study of periphyton community structure in long and short-hydroperiod Everglades marshes

The Florida Everglades is a mosaic of short and long-hydroperiod marshes that differ in the depth, duration, and timing of inundation. Algae are important primary producers in widespread Everglades’ periphyton mats, but relationships of algal production and community structure to hydrologic variability are poorly understood. We quantified differences in algal biomass and community structure between periphyton mats in 5 short and 6 long-hydroperiod marshes in Everglades National Park (ENP) in October 2000. We related differences to water depth and total phosphorus (TP) concentration in the water, periphyton and soils. Long and short-hydroperiod marshes differed in water depth (73 cm vs. 13 cm), periphyton TP concentrations (172μg g−1 vs. 107 μg g−1, respectively) and soil TP (284 μg g−1 vs. 145 μg g−1). Periphyton was abundant in both marshes, with short-hydroperiod sites having greater biomass than long-hydroperiod sites (2936 vs. 575 grams ash-free dry mass m−2). A total of 156 algal taxa were identified and separated into diatom (68 species from 21 genera) and “soft algae” (88 non-diatom species from 47 genera) categories for further analyses. Although diatom total abundance was greater in long-hydroperiod mats, diatom species richness was significantly greater in short- hydroperiod periphyton mats (62 vs. 47 diatom taxa). Soft algal species richness was greater in long-hydroperiod sites (81 vs. 67 soft algae taxa). Relative abundances of individual taxa were significantly different among the two site types, with soft algal distributions being driven by water depth, and diatom distributions by water depth and TP concentration in the water and periphyton. Periphyton communities differ between short and long-hydroperiod marshes, but because they share many taxa, alterations in hydroperiod could rapidly

Exploring the Use of Everglades Agricultural Area Canal Water as Base Medium for the Mass Production of Algae for Biofuels

Freshwater use is a major concern in the mass production of algae for biofuels. This project examined the use of canal water obtained from the Everglades Agricultural Area as a base medium for the mass production of algae. This water is not suitable for human consumption, and it is currently used for crop irrigation. A variety of canals were found to be suitable for water collection. Comparison of two methods for algal production showed no significant difference in biomass accumulation. It was discovered that synthetic reticulated foam can be used for algal biomass collection and harvest, and there is potential for its application in large-scale operations. Finally, it was determined that high alkaline conditions may help limit contaminants and competing organisms in growing algae cultures.

Influência de eventos hidrológicos extremos na qualidade da água de reservatórios na região tropical semiárida

Reservoirs are artificial ecosystems, intermediate between rivers and lakes, with diferent morphological and hydrological characteristics that can provide many important benefits to society. However, the use of this water for human consumption, watering livestock, leisure, irrigated agricultural production and pisciculture development, directly influence the increase loading of nutrients to aquatic environments and contribute to acceleration of eutrophication. Furthermore, global climate models are predicting a higher occurrence of extreme events such as floods and severe droughts, which will create hydrological stresses in lakes. In the semiarid northeast we can see the occurrence of these events, the drought of the years 2012, 2013 and 2014 was the worst drought in 60 years, according to the National Water Agency (ANA). Thus, this study aimed to evaluate the quality of the semiarid tropical water sources, identifying temporal patterns in periods with extreme hydrological events (floods and severe droughts). The study results showed that Gargalheiras and Cruzeta reservoirs presented significative changes in the limnological variables between rain and severe drought periods, with better appearance and in the most of the water quality variables in the rainy season and higher nutrientes concentrations and high electrical conductivity values in severe season, indicating decay of its quality. However, we found diferent behaviors between the reservoirs in severe drought. While Gargalheiras showed a typical behavior of the region, with high concentrations of algal biomass, indicating the worsening eutrophication, Cruzeta demonstrated a colapse in the total phytoplankton biomass, evidenced by the decrease in chla concentrations. This fact occurred because the low depth and proximity with the sediment facilited the inorganic solids resuspension and, consequently, resulted in turbid water column and light by limitation. In addition, the different behaviors between the reservoirs indicate that the responses of these environments problems such as extreme events must take into account factors such the region climate, size, depth of the reservoir and the basin characteristics.

Influência da seca extrema na dinâmica fitoplanctônica de um reservatório da região tropical semiárida: uma abordagem morfofuncional

Droughts are climatic phenomena whose frequency has increased in the last decades and also compromised drinkable water supplies in semiarid regions. The lack of rain combined with high evaporation rates promotes a significant reduction of the volume of reservoirs in these regions. Shallower conditions favors nutrients concentration and phytoplankton overgrowth, including potentially toxic cyanobacteria blooming. Therefore, there is a tendency to the intensification of eutrophication in those reservoirs during drought periods. Phytoplankton can respond quickly to environmental conditions related to light and nutrient availability by changes in algal biomass and composition, therefore it is considered a good predictor of environmental variables. Two functional approaches - Reynolds’s Functional Groups (FG) and Kruk’s Morphologically Based Functional Groups (MBFG) - were used to assess which environmental variables were responsible for phytoplankton dynamics, in addition to compare which functional approach explains environmental changes better. This study highlights that the reduction of 90% in the volume of a tropical reservoir of Brazilian semi-arid region, as well as light limitation and nutrient increase, can promote phytoplankton overgrowth. Multivariate analyses using both functional approaches indicated a clear separation between high volumes and low volumes conditions, showing that light and nutrient availability were the main variables that better explained the combination of functional groups. The composition of phytoplankton assemblage changed from species of meso-eutrophic habitats (FG: F and J; MBFG: VI), to organisms of eutrophic and turbid environments (FG: SN and M; MBFG: VIII and VII) during shallower conditions. Both ecological approaches described properly the phytoplankton dynamics according to light and trophic state alterations related to the water volume reduction, therefore they can be considered as equivalent approaches for using in similar environments.

Adição de policloreto de alumínio e remoção de peixes bentívoros como técnicas de restauração de lagos rasos do semiárido brasileiro

Eutrophication is the most common cause of water quality degradation in the world. This process occurs by excessive nutrients inputs, nitrogen and phosphorus, to the aquatic systems resulting in algal and cyanobacterial blooms. In shallow lakes these effects are pronounced due to the higher interaction of the lake with watershed, air and sediment. There are innumerous restoration techniques of eutrophied lakes with a range of successful results but there is only one case of successful lake restoration in Brazil: Paranoá Lake in Brasília city. The Brazilian semiarid region has many artificial lakes, named açudes, which are mostly eutrophic and shallow lakes. The eutrophication in these lakes is reported and the phytoplankton community is dominated by potentially toxic cyanobacteria species, mainly Cylindrospermopsis raciborskii. The aim of this thesis is to test techniques for water quality management which can be easily applied in Brazilian semiarid lakes. Results from a laboratory experiment suggest that the addition of a phosphorus sorbent clay associated with an aluminium based coagulant is an effective technique in removing soluble reactive phosphorus and reducing C. raciborskii growth rate – cyanobacteria potentially toxic dominant in reservoirs of Brazilian semiarid – but this effect is dependent on the biomass in the application moment. Results from a field experiment in mesocosm in a eutrophied lake showed that the addition of aluminium based coagulant and removal of benthivorous fish is more efficient in removing total phosphorus and chlorophyll-a from water column than the isolated application of one of the techniques. Lastly, laboratory tests showed that aluminium based coagulant exhibited good performance in removing turbidity and total phosphorus from water of six reservoirs but the efficiency was reduced by algal biomass and pH. The results of this study showed that the improvement in water quality of eutrophied reservoirs in semiarid region is possible through internal loading control by phosphorus precipitation and inactivation in sediments or inhibition of phosphorus release by benthivorous fishes, and also that these results show are additives in water quality improvement.

Adição de policloreto de alumínio e remoção de peixes bentívoros como técnicas de restauração de lagos rasos do semiárido brasileiro

Eutrophication is the most common cause of water quality degradation in the world. This process occurs by excessive nutrients inputs, nitrogen and phosphorus, to the aquatic systems resulting in algal and cyanobacterial blooms. In shallow lakes these effects are pronounced due to the higher interaction of the lake with watershed, air and sediment. There are innumerous restoration techniques of eutrophied lakes with a range of successful results but there is only one case of successful lake restoration in Brazil: Paranoá Lake in Brasília city. The Brazilian semiarid region has many artificial lakes, named açudes, which are mostly eutrophic and shallow lakes. The eutrophication in these lakes is reported and the phytoplankton community is dominated by potentially toxic cyanobacteria species, mainly Cylindrospermopsis raciborskii. The aim of this thesis is to test techniques for water quality management which can be easily applied in Brazilian semiarid lakes. Results from a laboratory experiment suggest that the addition of a phosphorus sorbent clay associated with an aluminium based coagulant is an effective technique in removing soluble reactive phosphorus and reducing C. raciborskii growth rate – cyanobacteria potentially toxic dominant in reservoirs of Brazilian semiarid – but this effect is dependent on the biomass in the application moment. Results from a field experiment in mesocosm in a eutrophied lake showed that the addition of aluminium based coagulant and removal of benthivorous fish is more efficient in removing total phosphorus and chlorophyll-a from water column than the isolated application of one of the techniques. Lastly, laboratory tests showed that aluminium based coagulant exhibited good performance in removing turbidity and total phosphorus from water of six reservoirs but the efficiency was reduced by algal biomass and pH. The results of this study showed that the improvement in water quality of eutrophied reservoirs in semiarid region is possible through internal loading control by phosphorus precipitation and inactivation in sediments or inhibition of phosphorus release by benthivorous fishes, and also that these results show are additives in water quality improvement.

Radionuclides measured on 27 water bottle profiles during POLARSTERN cruise ANT-XXIV/3

As part of the GEOTRACES Polarstern expedition ANT XXIV/3 (ZERO and DRAKE) we have measured the vertical distribution of 234Th on sections through the Antarctic Circumpolar Current along the zero meridian and in Drake Passage and on an EW section through the Weddell Sea. Steady state export fluxes of 234Th from the upper 100m, derived from the depletion of 234Th with respect to its parent 238U, ranged from 621±105 dpm/m**2/d to 1773±90 dpm/m**2/d. This 234Th flux was converted into an export flux of organic carbon ranging from 3.1-13.2 mmolC/m**2/d (2.1-9.0 mmolC/m**2/d) using POC/234Th ratio of bulk (respectively >50 µm) suspended particles at the export depth (100 m). Non-steady state fluxes assuming zero flux under ice cover were up to 23% higher. In addition, particulate and dissolved 234Th were measured underway in high resolution in the surface water with a semi-automated procedure. Particulate 234Th in surface waters is inversely correlated with light transmission and pCO2 and positively with fluorescence and optical backscatter and is interpreted as a proxy for algal biomass. High resolution underway mapping of particulate and dissolved 234Th in surface water shows clearly where trace elements are absorbed by plankton and where they are exported to depth. Quantitative determination of the export flux requires the full 234Th profile since surface depletion and export flux become decoupled through changes in wind mixed layer depth and in contribution to export from subsurface layers. In a zone of very low algal abundance (54-58 °S at the zero meridian), confirmed by satellite Chl-a data, the lowest carbon export of the ACC was observed, allowing Fe and Mn to maintain their highest surface concentrations (Klunder et al., this issue, Middag et al., this issue). An ice-edge bloom that had developed in Dec/Jan in the zone 60-65 °S as studied during the previous leg (Strass et al., in prep) had caused a high export flux at 64.5 °S when we visited the area two months later (Feb/March). The ice-edge bloom had then shifted south to 65-69 °S evident from uptake of CO2 and dissolved Fe, Mn and 234Th, without causing export yet. In this way, the parallel analysis of 234Th can help to explain the scavenging behaviour of other trace elements.

Evaluating the spatial transferability and temporal repeatability of remote-sensing-based lake water quality retrieval algorithms at the European scale: a meta-analysis approach

Many studies have shown the considerable potential for the application of remote-sensing-based methods for deriving estimates of lake water quality. However, the reliable application of these methods across time and space is complicated by the diversity of lake types, sensor configuration, and the multitude of different algorithms proposed. This study tested one operational and 46 empirical algorithms sourced from the peer-reviewed literature that have individually shown potential for estimating lake water quality properties in the form of chlorophyll-a (algal biomass) and Secchi disc depth (SDD) (water transparency) in independent studies. Nearly half (19) of the algorithms were unsuitable for use with the remote-sensing data available for this study. The remaining 28 were assessed using the Terra/Aqua satellite archive to identify the best performing algorithms in terms of accuracy and transferability within the period 2001–2004 in four test lakes, namely Vänern, Vättern, Geneva, and Balaton. These lakes represent the broad continuum of large European lake types, varying in terms of eco-region (latitude/longitude and altitude), morphology, mixing regime, and trophic status. All algorithms were tested for each lake separately and combined to assess the degree of their applicability in ecologically different sites. None of the algorithms assessed in this study exhibited promise when all four lakes were combined into a single data set and most algorithms performed poorly even for specific lake types. A chlorophyll-a retrieval algorithm originally developed for eutrophic lakes showed the most promising results (R2 = 0.59) in oligotrophic lakes. Two SDD retrieval algorithms, one originally developed for turbid lakes and the other for lakes with various characteristics, exhibited promising results in relatively less turbid lakes (R2 = 0.62 and 0.76, respectively). The results presented here highlight the complexity associated with remotely sensed lake water quality estimates and the high degree of uncertainty due to various limitations, including the lake water optical properties and the choice of methods.

Microbial community composition of sandy intertidal sediments of Sylt-Rømø Basin, Wadden Sea

Molecular biological methods were used to investigate the microbial diversity and community structure in intertidal sandy sediments near the island of Sylt (Wadden Sea) at a site which was characterized for transport and mineralization rates in de Beer et al., (2005, hdl:10013/epic.21375). The sampling was performed during low tide in the middle of the flat, approximately 40 m in the offshore direction from the high water line on October 6, 1999, March 7, 2000, and July 5, 2000. Two parallel cores were collected from each season for molecular analyses. Within 2 h after sampling the sediment cores were sub-sampled and fixed in formaldehyde for FISH analysis. The cells were hybridized, stained with 4',6'-diamidino-2-phenylindole (DAPI) and microscopically counted as described previously [55]. Details of probes and formamide concentrations which were used are shown in further details. Counts are reported as means calculated from 10-15 randomly chosen microscopic fields corresponding to 700-1000 DAPI-stained cells. Values were corrected for the signals counted with the probe NON338. Fluorescence in situ hybridization (FISH)with group-specific rRNA-targeted oligonucleotide probes were used to characterize the microbial community structure over depth (0-12 cm) and seasons (March, July, October). We found high abundances of bacteria with total cell numbers up to 3×109 cells ml-1 and a clear seasonal variation, with higher values in July and October versus March. The microbial community was dominated by members of the Planctomycetes, the Cytophaga/Flavobacterium group, Gammaproteobacteria, and bacteria of the Desulfosarcina/Desulfococcus group. The high abundance (1.5×10**7 - 1.8×10**8 cells/ml accounting for 3-19% of all cells) of presumably aerobic heterotrophic polymer-degrading planctomycetes is in line with the high permeability, deep oxygen penetration, and the high rates of aerobic mineralization of algal biomass measured in the sandy sediments by de Beer et al., (2005, hdl:10013/epic.21375). The high and stable abundance of members of the Desulfosarcina/Desulfococcus group, both over depth and season, suggests that these bacteria may play a more important role than previously assumed based on low sulfate reduction rates in parallel cores de Beer et al., (2005).