Increase In Algal Biomass Research Articles

Combined Earth observations reveal the sequence of conditions leading to a large algal bloom in Lake Geneva

Freshwater algae exhibit complex dynamics, particularly in meso-oligotrophic lakes with sudden and dramatic increases in algal biomass following long periods of low background concentration. While the fundamental prerequisites for algal blooms, namely light and nutrient availability, are well-known, their specific causation involves an intricate chain of conditions. Here we examine a recent massive Uroglena bloom in Lake Geneva (Switzerland/France). We show that a certain sequence of meteorological conditions triggered this specific algal bloom event: heavy rainfall promoting excessive organic matter and nutrients loading, followed by wind-induced coastal upwelling, and a prolonged period of warm, calm weather. The combination of satellite remote sensing, in-situ measurements, ad-hoc biogeochemical analyses, and three-dimensional modeling proved invaluable in unraveling the complex dynamics of algal blooms highlighting the substantial role of littoral-pelagic connectivities in large low-nutrient lakes. These findings underscore the advantages of state-of-the-art multidisciplinary approaches for an improved understanding of dynamic systems as a whole.

Regime shift in microalgal dynamics: Impact of water level changes on planktonic and benthic algal biomass

Whole-lake microalgal biomass surveys were carried out in Lake Balaton to investigate the seasonal, spatial, and temporal changes of benthic algae, as well as to identify the drivers of the phytobenthos. Phytobenthos was controlled mainly by light: the highest benthic algal biomass was in the shallow littoral region characterized by large grain size (sand) with good light availability but lower nutrient content in the sediment. During the investigated period, phytoplankton biomass showed a significant decrease in almost the entire lake. At the same time, the biomass of benthic algae increased significantly in the eastern areas, increasing the contribution of total lake microalgae biomass (from 20 % to 27 %). Benthic algal biomass increase can be explained by the better light supply, owing to the artificially maintained high water level which greatly mitigates water mixing. The decrease in planktonic algal biomass could be attributed to increased zooplankton grazing, which is otherwise negatively affected by mixing. As a result of the high water level, the trophic structure of the lake has been rearranged in recent decades with a shift from the planktonic life form to the benthic one while the nutrient supply has largely remained unchanged.

Efeitos das mudanças na estequiometria de N e P sobre a clorofila-a do epipélon e do fitoplâncton em condição eutrófica

ABSTRACT Nitrogen and phosphorus are essential elements for the growth and performance of organisms, and the environmental N:P ratio can determine the biomass and structure of algal communities. We investigated the effects in the N:P molar ratio changes on epipelon and phytoplankton chlorophyll-a under eutrophic conditions. An enrichment experiment was performed in open-bottom mesocosms to simulate P limitation, N limitation, and good N and P availability. Under eutrophic conditions, the combined availability of N and P enhanced phytoplankton bloom, while an increase in P limitation resulted in the loss of phytoplankton biomass. Under conditions of high P limitation, there was significantly loss of epipelon biomass. No change in the N:P ratio led to a significant increase in algal biomass in the epipelon. In conclusion, changes in the N:P molar ratio can affect the growth of phytoplankton and epipelic algae under eutrophic conditions. Our results suggest that photosynthetic biomass increase in the epipelon depends on an optimal relationship between light and P.

Exploring the functional connectivity between the Kis-Balaton Water Protection System and Lake Balaton using satellite data

Lake Balaton, a shallow polymictic freshwater lake in Central Europe, became eutrophic in the 1970s. To retain the inorganic nutrients from the main tributary River Zala, a semi-artificial system called the Kis-Balaton Water Protection System (KBWPS) was constructed in the early 1980s. In 2015, the system was reconstructed and modernised, thus offering the opportunity to evaluate the effectiveness of the functional connection between the KBWPS and Lake Balaton over the past 20 years and to compare its impact before and after the reconstruction. To this end, time series data of algal biomass in Lake Balaton between 1999 and 2019 based on Landsat 7 satellite data were analysed. Over the last 20 years, the algal biomass in Lake Balaton showed an increasing trend (0.009 ± 0.011% increase per year), with territorial specificities also observed. No change was noted in the western part, while an increase was recorded in the eastern part of the lake. A significant difference in the rate of algal biomass accumulation was noticed before (annual increase of 0.008 ± 0.019%) and after (0.240 ± 0.306% per year) the KBWPS reconstruction. Given that the largest increase in algal biomass after reconstruction was observed in the outermost KBWPS basin of Lake Balaton, it appears that mesoscale environmental, water balance, or other factors affecting the lake are playing a role in this increase, rather than the KBWPS reconstruction. This research highlights the potential to study aquatic ecosystems using Earth observation techniques, and how mesoscale factors such as changes in the local climate regime or shifts in lake management can greatly impact the trophic state of a large shallow lake. Effectively identifying these factors is crucial in maintaining the proper status of aquatic ecosystems.

Combinatory effects of microplastics and emerging contaminants on alga Chlamydomonas reinhardtii

In oceans today, there is much concern about the effects of microplastics (MPs) and other emerging contaminants (ECs). Here, the authors investigated the combinatory effects of the MPs poly(vinyl chloride) (PVC) and acrylates/C10–30 alkyl acrylates cross-polymer (AC) (which are commonly found in face wash), together with 2-phenoxyethanol (an EC commonly used in soaps). The model photosynthetic unicellular alga Chlamydomonas reinhardtii was used to study the potential of these pollutants to initiate algal blooms. It was shown that AC alone resulted in a greater decline in algal biomass as compared with PVC in the short term (14 days). While algal cultures exposed to PVC registered the highest increase in concentrations of the chlorophyll a pigment, it was the combinatory effects of each MP and 2-phenoxyethanol that were the most pronounced in terms of the large increase in algal biomass and the formation of extracellular polymeric substances. Proliferative growths of C. reinhardtii after prolonged exposure to AC–EC contaminants show potential for initiating algal blooms in aquatic environments. Hence, AC should be considered for regulation of waste water removal into water bodies, and other combinations of MPs and ECs should also be investigated.

Sources and degradation of organic matter and its relation to trophic status in the core sediments of a tropical mangrove ecosystem along the Southwest coast of India

Present study has been designed to reveal the organic matter sources (algal vs. terrestrial), trophic status, the role of diagenesis and the applicability of biogeochemical indicators in a highly urbanized tropical mangrove forest. This has been achieved through a multiproxy approach by investigating the downcore distribution of bulk elemental properties (Total organic carbon (TOC%), total nitrogen (TN%)), biochemical composition, phytopigments and total hydrolysable amino acids (THAA). Both cores have a strong increase in algal biomass in the upper more fine grained part while core C2 has higher land plant fraction in its lower part compared to C1. The THAA profile decreased downcore ranging from 6.07 to 602.93 μmol g−1, contributing 7–53% THAA-N and 6–23% THAA-C to the sediments. Amino acids namely, serine (Ser) and tyrosine (Tyr) suggesting the contribution of fresh plankton organic matter likely by bacterial activity, while valine (Val), phenylalanine (Phe), isoleucine (Iso) and leucine (Lue) indicated more land plant derived organic matter. The surface dominance of proteins (PRT) and phaeophytin (Phaeo) pigment supporting the change from a more land plant derived organic matter to a more aquatic/marine driven productivity in the upper core sediments. Biochemical ratio (PRT/CHO >1), biopolymeric carbon (BPC), algal contribution to BPC (AL%-BPC) and degradation index (DI) indicated eutrophication related with the increase in algal organic matter. Based on mol%, amino acids viz., glycine (Gly) and alanine (Ala) were significantly enriched in downcore diagenetically reworked sediments indicating the growth of bacterial colonies and the selective preservation of bacterial biomass. Organic matter transformation from labile form into refractory character and vice versa through bacterial reworking, plays a major role in the development from oligotrophy to hypertrophy in the Cochin lagoon. The increasing urbanization have caused anthropogenic induced change in sediment composition, and recent eutrophication changed a more land plant dominated aquatic system to enhanced algal productivity.

Phytoplanktonic response to simulated volcanic and desert dust deposition events in the South Indian and Southern Oceans

AbstractContrasting concentrations of macronutrients and micronutrients induce different nutrient limitations of the oceanic productivity and shape the composition of the phytoplankton communities of the South Indian Ocean and Indian sector of the Southern Ocean. o assess the phytoplankton response to nutrient release by desert dust and volcanic ash aerosols in these distinct biogeochemical regions, we conducted microcosm incubation experiments. A dry or wet deposition of either dust from Patagonia or ash from the Icelandic volcano Eyjafjallajökull or dissolved nutrients (Si, Fe, N and/or P) were added to trace metal clean incubations of surface seawater collected from five stations. These deposition experiments enabled the measurement of the biological response along with solubility calculations of nutrients. Both types of aerosols alleviated the iron deficiency occurring in the Southern Ocean during austral summer and resulted in a 24–110% enhancement of the primary production, depending on the station. The release of dissolved silicon may also have contributed to this response, although to a lesser extent, whereas neither the dust nor the ash relieved the nitrogen limitation in the low‐nutrient and low‐chlorophyll area. Diatom growth was responsible for 40% to 100% of the algal biomass increase within the responding stations, depending on the region and aerosol type. The high particle concentrations that are characteristic of ash deposition following volcanic eruptions may be of equal or higher importance to phytoplankton compared to desert dust, despite ashes' lower nutrient solubility to the ocean.

Spatial and temporal variation of physico-chemical parameters of water and its impact on algal distribution in the Oualidia lagoon (Atlantic coast of Morocco)

The Oualidia lagoon is a restricted lagoon exposed to various sources of pollution, that have a negative impact on the quality of its water. Since 2015, a high increase of algal biomass was clearly observed. Therefore, this study was carried out in order to highlight the relationship between the trophic quality of the water and the appearance of algae. The study of spatiotemporal variation of physicochemical parameters (Temperature, pH, Salinity, Dissolved oxygen, Nitrate (NO3) and Orthophosphate (PO4)) and the spatial distribution of algae was conducted between March 2019 and February 2020. The results showed a significant spatial and seasonal variation (p<0.01) of the studied physicochemical parameters with the presence of upstream–downstream gradients for most of the parameters. 39 species of algae were identified in all the lagoon and during the whole study cycle. The distribution of algae was highly affected by the concentration of nutrients along the lagoon and also by the variation of physical factors such as stream, the downstream is rich in algal species, while the upstream has a limited biodiversity (around 6 species) with a high abundance of species.

Impacts of the Floc and Sink technique on the phytoplankton community: A morpho-functional approach in eutrophic reservoir water

The Floc and Sink technique promotes, through the application of coagulants and clays, the removal of phosphorus and algal biomass from the water column by flocculation and sedimentation. Although it is a promising technique for mitigating harmful cyanobacterial blooms, little is known about the impacts on other phytoplankton species as well as it is not known how species with mechanisms of resistance to sedimentation respond to the application of these products. In this study, a laboratory experiment was carried out with water from a eutrophic reservoir to assess the impact of applying aluminum-based coagulants, aluminum sulfate and polyaluminium chloride, and chitosan, alone and combined with lanthanum modified bentonite and natural bentonite on the phytoplankton community, in a functional approach based on morphology (Morphology-Based Functional Groups – MBFG, Kruk et al., 2010 and Reynolds et al., 2014), with an emphasis on the characteristics that provide resistance to sedimentation. We tested two hypotheses: phytoplankton species with adaptive mechanisms that provide buoyancy to cells are more resistant to the removal from the water column by coagulants and clays; and coagulants based on metals and modified clays are more efficient in sedimentation of microalgal cells compared to natural products, regardless of the presence of an adaptive mechanism of resistance to sedimentation. Our results showed that aluminum sulfate and polyaluminium chloride alone or combined with lanthanum modified bentonite and natural bentonite effectively sedimented the cells, regardless of the presence of buoyancy mechanisms. In contrast, the natural coagulant chitosan alone or combined with lanthanum modified bentonite and natural bentonite removed only those species that were small-celled or small colonial without specialized structures or with the presence of spines, arms and siliceous exoskeleton. In the case of species with aerotopes and flagella, the removal was not effective and still caused an increase in algal biomass due to the formation of suspended cell aggregates on the surface of the water column of the experimental units. Therefore, we concluded that the Floc and Sink technique has an impact on the phytoplankton community because it removes from the water column species that are not the target of coagulants and clays, but that are considered important sources of energy in freshwater trophic webs. This result differs according to the type of product used as well as it is related to the morphological adaptations that favor the buoyancy of cells in the water column. Species with aerotopes and flagella are more resistant to sedimentation and may make the use of products applied in the Floc and Sink technique unfeasible. Nevertheless, these results represent only an immediate effect of the technique on the phytoplankton community, thus requiring a longer time scale evaluation to determine the algae that can effectively recover water column. Therefore, we also emphasize that algae of nutritional value can recover over time and make the long-term application of the technique acceptable.

The shift from macrophytic to algal particulate organic matter favours dissimilatory nitrate reduction to ammonium over denitrification in a eutrophic lake

Abstract In eutrophic lakes, the shift from a macrophyte‐dominated state to an algae‐dominated state changes the particulate organic matter (POM) sources, which in turn alters organic matter quality that is released and that sinks to the benthos. However, the influences of this shift on denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are unclear in eutrophic lakes. Here, we elucidated how various POM sources influenced these nitrate reduction pathways in a eutrophic lake. The lake sediments from August were incubated under algae, macrophyte, and soil treatments in aquarium tanks. Potential denitrification and DNRA rates and related functional gene abundances were measured periodically. Meanwhile, the n‐alkanes composition of POM and fluorescence excitation‐emission matrices of dissolved organic matter were measured before and during incubations, respectively, to aid in the analysis of the potential mechanisms by which organic matter quality affect nitrate reduction. The results indicated that algal detritus was more labile and decomposed faster than other POM, coupled with higher DNRA rates and nrfA gene abundances. Macrophyte treatments resulted in nitrate accumulation and the increase of gene abundances related to denitrification, but no increase in denitrification rates was observed. In soil treatments, nitrate reduction processes were not significantly influenced by the addition of POM. Overall, compared with other sources, algae‐derived POM can produce high‐quality organic carbon, low dissolved oxygen and nitrate concentrations, which is more conducive to DNRA than denitrification. A loss of macrophytes and increase in algal biomass will induce changes in autochthonous POM quality and potentially drive nitrogen recycling in eutrophic lakes.

Ecology and climate sensitivity of a groundwater-fed lake on subtropical North Stradbroke Island (Minjerribah), Queensland, Australia over the last 7500 years

Lake sediments are important archives of past climate variability and lake responses to climate. In order to accurately infer past climates, it is necessary to understand, and account for, the ecological processes that affect the record of indicators preserved in lake sediment. This is particularly the case with respect to the concentration of carbon and nitrogen (TOC, TN, and calculated C:N), and the stable isotope composition of organic matter preserved in lake sediments. These are common, yet ambiguous, tracers of environmental change. Ideally, palaeoenvironmental reconstructions using the concentration and isotope composition of organic matter should be grounded in a detailed understanding of the sources of the organic material. This study documents the history and evolution of Blue Lake, an environmentally and culturally important oligotrophic, groundwater window lake on North Stradbroke Island, Queensland, Australia. We utilise organic matter δ13C, TOC, TN, and C:N from a 2.4 m sediment core with a basal age of 7.5 cal kyr BP, to investigate changing organic matter sources as a measure of the climate sensitivity of Blue Lake. This interpretation is supported by data from contemporary algae, aquatic and terrestrial plants, and catchment soils. We show that lake nutrient dynamics drove an increase in algal biomass at 4.2 cal kyr BP. This change coincides with a widely documented intensification of the El Niño-Southern Oscillation, which we infer to have influenced lake nutrient concentrations by reducing groundwater throughflow. Climatic changes resulted in marked changes in lake primary productivity, despite relatively little turnover of the lake diatom flora and catchment vegetation. This suggests that south-east Queensland dune lakes are sensitive to climate changes and helps to refine past and future palaeoclimate research using sediments from these lakes. It also indicates that increased nutrient concentrations in Blue Lake may result from projected changes in 21st Century climate.

ВЛИЯНИЕ САЛИЦИЛОВОЙ КИСЛОТЫ НА ПРОДУКЦИОННЫЕ ХАРАКТЕРИСТИКИ И БИОХИМИЧЕСКИЕ ПОКАЗАТЕЛИ TETRASELMIS SUECICA В НАКОПИТЕЛЬНОЙ КУЛЬТУРЕ

The article considers the use of salicylic acid as a stimulator of microalgae growth. The influence of a wide range of salicylic acid concentrations on the growth dynamics of Tetra-selmis suecica in enrichment culture has been evaluated. Cultivation was carried out in monoculture. An increase in algal biomass was measured by the increasing number of cells counted in each experiment in three Goryaev chambers under a light microscope. The duration of the experiments was 14 days. It is shown that salicylic acid in concentrations of 0.4-1.9 • 10–5 M inhibits the growth of algae. The growth of the control culture has two pronounced peak numbers on 4th and 12th days of the experiment. The introduction of salicylic acid in concentrations of 0.44-1.9 • 10–5 M was accompanied by a change of the growth curves: the maximum number of cells was observed on 12th day of the experiment. A higher concentration of phytohormone (3.75.• 10–5 M) provided an increase in crop density by 414% over 14 days of the experiment. The growth of T. suecica culture in the control group was 332%. The values of the specific growth rate of T. suecica were calculated for different periods of cultivation. After 14 days of the experiment, the biochemical composition of the microalgae biomass was evaluated, which showed stimulation with salicylic acid at a con-centration of 3.75 • 10–5 M carbohydrate accumulation. The high concentration of phytohormone suppressed the accumulation of protein, lipids and chlorophyll in the culture and stimulated the accumulation of carbohydrates. It has been suggested that a possible mechanism for the multidirectional action of salicylic acid is its effect on synthesis and catabolism through inhibition of the synthesis and metabolism of endogenous plant hormones.

The Contribution Ratio of Autotrophic and Heterotrophic Metabolism during a Mixotrophic Culture of Chlorella sorokiniana.

The contribution ratio of autotrophic and heterotrophic metabolism in the mixotrophic culture of Chlorella sorokiniana (C. sorokiniana) was investigated. At the early stage of mixotrophic growth (day 0–1), autotrophy contributed over 70% of the total metabolism; however, heterotrophy contributed more than autotrophy after day 1 due to the rapid increase in cell density, which had a shading effect in the photo-bioreactor. Heterotrophy continued to have a higher contribution until the available organic carbon was depleted at which point autotrophy became dominant again. Overall, the increase in algal biomass and light conditions in the photo-bioreactor are important factors in determining the contribution of autotrophy and heterotrophy during a mixotrophic culture.

Impacts of inter-basin water transfer on the water quality of receiving reservoirs in a tropical semi-arid region

Inter-basin water transfer (IBWT) involves the transport of water from one geographically distinct basin to another to balance the distribution of water resources. Although the socio-economic benefits of implementing these projects are well recognized, little is known about the subsequent effects on the water quality of the receiving systems. We evaluated the effects of an IBWT on the water quality of three receiving reservoirs of an intermittent river in a semi-arid region. We compared the similarity among the reservoirs before and after the IBWT to assess how the reservoirs responded to the introduction of water. Although the last two reservoirs that have received water have become similar in terms of physical and chemical characteristics and algal biomass (chlorophyll-a), the first reservoir has not. The IBWT resulted in an improvement in the water quality of the first reservoir but a decrease in the water quality of the two successive reservoirs, along with a significant increase in algal biomass. Long river sections located upstream that were dry at the time of IBWT probably contributed nutrients to the water as it moved downstream and into the reservoirs. Significant differences in the water quality were observed for different sampling months after the IBWT, but not for different sampling depths. Before the IBWT, the predictor variables for algal biomass were basically transparency and non-algal turbidity, with which it established a positive relationship. After IBWT, however, algal biomass also showed a positive relationship with pH and temperature. We conclude that IBWT affects the water quality of receiving reservoirs and that the responses are reservoir specific. IBWT also increases the complexity of the correlations of physical and chemical variables with algal biomass.

Carbon subsidies shift a northern peatland biofilm community towards heterotrophy in low but not high nutrient conditions

Abstract Producer–decomposer interactions within aquatic biofilms can range from mutualistic associations to competition depending on available resources. The outcomes of such interactions have implications for biogeochemical cycling and, as such, may be especially important in northern peatlands, which are a global carbon sink and are expected to experience changes in resource availability with climate change. The purpose of this study was to evaluate the effects of nutrients and organic carbon on the relative proportion of primary producers (microalgae) and heterotrophic decomposers (bacteria and fungi) during aquatic biofilm development in a boreal peatland. Given that decomposers are often better competitors for nutrients than primary producers in aquatic ecosystems, we predicted that labile carbon subsidies would shift the biofilm composition towards heterotrophy owing to the ability of decomposers to outcompete primary producers for available nutrients in the absence of carbon limitation. We manipulated nutrients (nitrate and phosphate) and organic carbon (glucose) in a full factorial design using nutrient‐diffusing substrates in an Alaskan fen. Heterotrophic bacteria were limited by organic carbon and algae were limited by inorganic nutrients. However, the outcomes of competitive interactions depended on background nutrient levels. Heterotrophic bacteria were able to outcompete algae for available nutrients when organic carbon was elevated and nutrient levels remained low, but not when organic carbon and nutrients were both elevated through enrichment. Fungal biomass was significantly lower in the presence of glucose alone, possibly owing to antagonistic interactions with heterotrophic bacteria. In contrast to bacteria, fungi were stimulated along with algae following nutrient enrichment. The decoupling of algae and heterotrophic bacteria in the presence of glucose alone shifted the biofilm trophic status towards heterotrophy. This effect was overturned when nutrients were enriched along with glucose, owing to a subsequent increase in algal biomass in the absence of nutrient limitation. By measuring individual components of the biofilm and obtaining data on the trophic status, we have begun to establish a link between resource availability and biofilm formation in northern peatlands. Our results show that labile carbon subsidies from outside sources have the potential to disrupt microbial coupling and shift the metabolic balance in favour of heterotrophy. The extent to which this occurs in the future will probably depend on the timing and composition of bioavailable nutrients delivered to surface waters with environmental change (e.g. permafrost thaw).

High-Efficiency Ukrainian Strains of Microalgae for Biodiesel Fuel Production (Overview)

Background: In Ukraine, the research works focused on the study of green microalgae as an alternative source of feedstock for biodiesel production started in 2009. The screening of the Ukrainian Microalgae Culture Collection (IBASU-A) revealed a number of promising strains of species belonging to Chlorella, Chloroidium, Desmodesmus, and Parachlorella (Chlorellaceae and Scenedesmaceae) genera. The main criteria for strain selection were: accumulation of a significant volume of lipids, high kinetic characteristics (specific growth rate and productivity), resistance to stresses and biological contaminations. Some novel algal strains with relevant properties and optimized to the local climatic conditions were also isolated from different regions of Ukraine. Biotechnological studies showed a rather high potential of many of them, especially those of species from Tetradesmus and Desmodesmus (Scenedesmaceae) genera. Recently, some strains of species belonging to Monoraphidium, Raphidocelis, and Selenastrum (Selenastraceae) genera have also been isolated and the search for strains with a high biomass production continued. Objective: Moving from an overview of the oleaginous high-efficiency strains present in the largest algal collection in Ukraine (IBASU-A) and a critical analysis of problems related to biodiesel fuel production by microalgae, here we report preliminary data on biomass productivity, lipid amount and fatty acid profiles of some Ukrainian strains of Selenastraceae family. Methods: Traditional techniques were used for the isolation of new strains. The study of growth characteristics was carried out under intensive conditions and the daily increase of algal biomass was determined by the gravimetrical method. The data obtained on growth characteristics were compared with those of the well-known producers of biomass. The fatty acid composition in the most promising strains was determined by the gas-liquid chromatography. Results: Three new algal strains, M. minutum IBASU-A 574, Monoraphidium sp. IBASU-A 377 and Raphidocelis subcapitata IBASU-A 358, of Selenastraceae, adapted to regional climatic conditions, were isolated from different regions of Ukraine. They showed a higher efficiency in biodiesel production with respect to strains of Chlorellaceae and Scenedesmaceae earlier investigated. The biomass productivity of M. minutum IBASU-A 574, Monoraphidium sp. IBASU-A 377 and Raphidocelis subcapitata IBASU-A 358 was 1.84, 0.84 and 1.32 g DW L-1·day-1, while the lipid contents were 33.65%, 29.43% and 23.14%, respectively. Their fatty acid profiles included mainly C16:0, C18:2 and C18:3, all of interest for biodiesel production. Conclusion: The Ukrainian Microalgae Culture Collection has been supplemented with strains of species from family Selenastraceae showing high-efficiency for biodiesel production and adaptation to local environmental conditions.

Carbon limitation in hypereutrophic, periphytic algal wastewater treatment systems.

Global eutrophication degrades water quality in freshwater ecosystems and limits the availability of freshwater for human consumption. While current wastewater treatment facilities (WWTF) remove pathogens and pollutants, many US WWTF continue to discharge nutrients that contribute to eutrophication. Traditional nutrient removal technologies can effectively reduce eutrophication risk, but can have unintended negative consequences on human and environmental health. Alternatives, such as algae-based treatment systems, improve the sustainability of the nutrient recovery process by producing biomass that can be converted to biofuel. However, research is needed to increase the productivity of algal treatment systems to improve their economic viability. Because algae in wastewater treatment systems are grown in wastewater rich in nutrients, the algae could become limited by dissolved inorganic carbon. This hypothesis was tested in 1.2 m long recirculating floways (n = 8 for each treatment/control) by quantifying algal dry mass and wastewater nutrient concentrations in 3 independent experiments: (1) carbon dioxide gas infused vs air infused control; (2) hydrochloric acid acidified vs neutralized solution control vs no chemical addition control; and (3) sodium bicarbonate addition vs no chemical control. Results showed increases in algal biomass after 18 days in wastewater augmented with dissolved inorganic carbon (carbon dioxide or sodium bicarbonate). In contrast, maintaining wastewater at near neutral pH with hydrochloric acid reduced algal productivity relative to controls. Nutrient reductions generally paralleled algal biomass increases except in the bicarbonate addition experiment. These findings provide evidence for the importance of carbon limitation in algal wastewater treatment floways. These results could help explain why carbon dioxide infusions stimulate algae in treatment systems. Furthermore, these results suggest that algae in nutrient enriched, sun-exposed streams (e.g., agricultural ditches or urbanized streams) may become carbon limited during peak periods of productivity. These findings could have important implications for ecosystems undergoing eutrophication as atmospheric carbon dioxide concentrations continue to rise.

Using plug-flow column reactor data to constrain calcic mineral weathering rates from watershed mass-balance methods: Lithogenic apatite dissolution and phosphorus fluxes into the Loch Vale Watershed ecosystem, Colorado, USA

Sources of phosphorus (P5+) to ecosystems can be very difficult to identify and quantify due to P5+ being monoisotopic. Previous field-based, watershed mass-balance calculations of the lithogenic P5+ flux in the alpine/subalpine Loch Vale watershed (LVW) of Colorado, USA suggested that weathering was controlled by one of three acid-weathering scenarios: (1) All minerals experience only carbonic acid weathering; (2) all minerals experience both carbonic acid and sulfuric acid weathering; and (3) only silicate minerals experience sulfuric acid weathering. We used a plug-flow column reactor to provide additional constraints that strongly indicate scenario (1) (carbonic acid-only weathering) explains the stream chemistry at the LVW outlet (1984–2008 period of sampling). Therefore, sulfuric acid generated by pyrite oxidation in the LVW is not significantly involved in chemical weathering reactions. In the column reactor, calcite dissolution by carbonic acid seemed to suppress apatite dissolution with the likelihood of this suppression confirmed by thermodynamic modeling and comparison to kinetic data. The comparability between column reactor and watershed-scale data likely reflects the LVW landscape being dominated by relatively high rates of mechanical weathering. The lithogenic P5+ flux from the LVW is solely attributable to apatite (Ca5(PO4)3(OH,F,Cl)) dissolution and is ~47 mol ha−1 yr−1, ~18 times greater than the modeled global average. The relatively high solubility of apatite in the Loch Vale watershed likely results from substantial quantities of radionuclides hosted as substituted elements in the crystal lattice, which may cause loss of crystallinity due to self-irradiation. Aeolian inputs to landscapes may supplement any P5+ from primary phosphate mineral dissolution. These natural sources of P5+ are likely contributing to the increases in algal biomass observed today.

Temporal variations of Halodule wrightii meadows and associated fauna near their southern distribution limit in the southwestern Atlantic

AbstractHalodule wrightiimeadows in Southern Brazil have been regressing in an unsheltered area of the subtropical Paranaguá Bay, near their southern limit in the SW Atlantic, since 2006. To identify early indicators of regression events, we assessed variations in plant and macrobenthic structure in two local meadows under unsheltered and protected conditions. Differences between sites increased after an epiphytic overgrowth of the algaHincksia mitchelliaeat the unsheltered site. Seagrass growth was suppressed and the numbers of burrowing and opportunistic benthic species increased with the increase of algal biomass. In the protected meadow, seagrass biomass and number of leaves changed seasonally, but macrobenthic abundance and species richness remained stable. Ecosystem changes were evident when the unsheltered meadow was already collapsing. The number of leaves per shoot, the horizontal internode length, the abundance and structure of the macrofaunal associations, and the host-epiphyte surface interactions, were the first variables to reflect the early stages of seagrass regression. Our results suggest that the persistence ofH. wrightiimeadows at their southern distribution limit in the SW Atlantic will be affected by local hydrodynamics and their ability to compete with ephemeral macroalgal species under stress conditions.

Overfishing and the ecological impacts of extirpating large parrotfish from Caribbean coral reefs

AbstractThe unique traits of large animals often allow them to fulfill functional roles in ecosystems that small animals cannot. However, large animals are also at greater risk from human activities. Thus, it is critical to understand how losing large animals impacts ecosystem function. In the oceans, selective fishing for large animals alters the demographics and size structure of numerous species. While the community‐wide impacts of losing large animals are a major theme in terrestrial research, the ecological consequences of removing large animals from marine ecosystems remain understudied. Here, we combine survey data from 282 sites across the Caribbean with a field experiment to investigate how altering the size structure of parrotfish populations impacts coral reef communities. We show that Caribbean‐wide, parrotfish populations are skewed toward smaller individuals, with fishes &lt;11 cm in length comprising nearly 70% of the population in the most heavily fished locations vs. ~25% at minimally fished sites. Despite these differences in size structure, sites had similar overall parrotfish biomass. As a result, algal cover was unrelated to parrotfish biomass and instead, was negatively correlated with the density of large parrotfishes. To mechanistically explore how large parrotfishes shape benthic communities, we manipulated fishes’ access to the benthos to create three distinct fish communities with different size structure. We found that excluding large or large and medium‐sized parrotfishes did not alter overall parrotfish grazing rates but caused respective 4‐ and 10‐fold increases in algal biomass. Unexpectedly, branching corals benefited from excluding large parrotfishes whereas the growth of mounding coral species was impaired. Similarly, removing large parrotfishes led to unexpected increases in coral recruitment that were absent when both large and medium bodied fishes were excluded. Our data highlight the unique roles of large parrotfishes in driving benthic dynamics on coral reefs and suggests that diversity of size is an important component of how herbivore diversity impacts ecosystem function on reefs. This study adds to a growing body of literature revealing the ecological ramifications of removing large animals from ecosystems and sheds new light on how fishing down the size structure of parrotfish populations alters functional diversity to reshape benthic reef communities.