Algalblooms are dense layers of cyanobacteria occurring on the surface of lakes and water bodies when there is an overabundance of nutrients (Phosphorus – P, and Nitrogen – N) on which algae depend for growth. It is a naturally occurring phenomenon resulting from the gradual accumulation of nutrients and organic matter from watersheds (Bath, 2017). However, excess nutrients may also originate from human induced activities such as agriculture (mostly from surface and subsurface water movement from fertilised soils and faulty manure storage), industrial and municipal waste water treatment plants, leaky home septic systems, run-off from lawns, and even atmospheric depositions. Hence, humans modified the natural frequency, extent, location, and potential toxicity of algalblooms. Nontoxic blooms hurt the environment and local economies, while toxic algalblooms, referred to as harmful algalblooms (HABs), are of particular relevance to humans because of their toxicity. Bright-green blooms occur in freshwater systems often as a result of cyanobacteria such as Microcystis. Red-tides or brownish blooms occur in brackish waters often as a result of harmful phytoplankton such as dinoflagellates of the genus Alexandrium and Karenia. HABs can produce dangerous toxins that can sicken or kill people and animals, create dead zones in the water (depleted in oxygen), raise treatment costs for drinking water (or provoke shutdowns), and hurt industries depending on clean water (EPA, 2018a).
The B-BLOOMS project associated Belgian research groups from three universities (Universities of Liège, Gent and Namur) having expertise in taxonomy and ecology of phytoplankton, as well as in molecular diversity of cyanobacteria. The first general objective of BBLOOMS was to document the extent, nature (genotypic diversity, identification of toxins), the phenology and ecology of nuisance blooms in Belgium. In other words, this two-year program was primarily proposed to make a first assessment of the extent of cyanobacterial blooms in Belgium and of the potential threat for the surface water resources. As cyanobacterial blooms are known to develop in specific environmental conditions (most blooms develop in stratified eutrophic “standing” water bodies), the project incorporated the development of predictive models: is it possible, from easily monitored environmental conditions, to predict where and when potentially toxic cyanobacteria blooms could occur, i.e. to set an early-warning system from environmental monitoring? Third, as the problem may well appear as being real, B-BLOOMS also puts an emphasis on the development of tools for detecting potentially harmful algalblooms in Belgian surface waters, which could be used later on to set up a country-wide monitoring network. Companies and agencies involved in the management and exploitation of freshwater resources were involved from the beginning, both in a user committee following the study and as members of a network (BLOOMNET) designed for sampling phytoplankton blooms in various freshwater bodies.
Despite the potential negative human health, ecological and economic impact, the ecology of harmful benthic dinoflagellate blooms remains largely unknown. This is probably due to the complex interactions among biotic and abiotic drivers that influence blooms, but also to the difficulty in quantifying cell abundance in a comparable way over large spatial and temporal scales. One of the recognized priorities for bHABs (benthic Harmful AlgalBlooms) assessment is developing and standardizing methods that can provide comparable data. In this context, the Benthic Dinoflagellates Integrator (BEDI), a new non-destructive quantification method for benthic dinoflagellate abundances, has been developed and tested within the present study. The rationale behind the BEDI standard assessment method is that mechanical resuspension of cells enables the quantification of abundances as cells per unit of seabed surface area (i.e. cells mm - 2 ) or as Potentially Resuspended cells per unit of volume (PRcells ml -1 ), by integrating both
surfaces covered with alga.
The reason why the regions of Brittany and Normandy are affected so severely are of two origins. Firstly there are geographical reasons. In large beaches, with a small slope, the effect of the waves (usually in combination with a small tidal current) might trap the algae close to the beach, where with a small water depth the algae will be in relatively warm water and have easy access to sunlight. Secondly there is the access to nutriments. The type of sediments and the proximity of these (i.e. in shallow water) can also increase the nutriments present in the water. Secondly during the summer the rivers have a smaller discharge, and therefore they reach the sea with a higher concentration of nutriments. Finally, with the human occupation along the coastline, rain water enters the ocean faster, and through human activity (such as agriculture) a higher dose of nutriments enters the water cycle. Further details on the reasons behind the increase of Ulva populations can be found in Inf’ODE (1999). Nonetheless these algae are not toxic in their natural form, but the amount that is deposited causes many problems. When deposited on the beach these algae will decompose, and because of the amount present, the fumes emitted from this decomposition prove to be hazardous. Furthermore the presence of these algalblooms in the water will partially block the access to sea water. This proves to be particularly cumbersome for harbours or industrial structures that requires readily available sea water in their manufacturing process.
Keywords Algal bloom . Coagulant . Magnetic separation . Adsorption . Coagulation
The frequent outbreaks of algalblooms in freshwater bodies are a global issue (Anderson 1997 ; Beth 1998 ; Mackenzie 1999 ; Rigby 2000 ; Ruiz et al. 2000 ; Vasconcelos and Pereira 2001 ). Algalblooms seriously damage the balance and stability of aquatic ecosystems, which negatively affect the water landscape and aqua- culture development. Blooms involving toxin-producing species can pose serious threats to animals and humans (Hoehn et al. 1990 ; Pouria et al. 1998 ; Codd 2000 ). Recent studies use physical, chemical, and ecological methods to control algalblooms to some extent (Lam et al. 1995 ; Anderson 1997 ; Datta and Jana 1998 ; Hejzlar et al. 1998 ; Nagasaki et al. 1999 ; Gao et al.
The Sentinel-3 OLCI is equipped with 21 spectral bands, including 7 narrow chlorophyll a bands. The advanced band configuration of OLCI makes it a valuable sensor for mapping algalblooms not only in water but also on ice (Wang et al., 2018). OLCI was designed based on the opto- mechanical and imaging design of the MEdium Resolu- tion Imaging Spectrometer (MERIS) onboard the European Space Agency (ESA)’s Envisat satellite, operational from March 2002 to April 2012, which collected data in 15 spec- tral bands between 390 and 1040 nm. MERIS features in par- ticular a 709 nm band where high levels of chlorophyll a produce a characteristic reflectance peak. MERIS data have been broadly used for atmospheric and oceanic studies, with the primary goal of measuring the concentration of chloro- phyll a and suspended sediments in oceans, coastal waters, and inland lakes (Gower et al., 2008; Palmer et al., 2015). Similar configurations of the chlorophyll-targeted bands in terms of wavelength and bandwidth between MERIS and OLCI (Fig. 1a) point to the potential of using MERIS data to reconstruct the spatial distribution of glacier algae prior to 2012. In this study, we make use of the capability of MERIS for detecting chlorophyll a to extend the quantification of glacier algae in southwestern Greenland back to the 2004– 2011 period, and further quantify the impact of glacier algalblooms on bare ice albedo by combining the time series data of MERIS and MODIS.
Harmful algalblooms (HABs) in aquatic ecosystems are of concern worldwide. This review deals with how jurisdictions around the world are addressing this water quality issue to inform recommendations regarding nutrient loading and HABs in Missisquoi Bay-Lake Champlain and Lake Memphremagog; transboundary lakes located in the USA and Canada that suffer from symptoms of eutrophication. A global scan of the literature resulted in the consideration of 12 case studies of large water bodies within large watersheds, excluding in-lake geoengineering approaches. Although all of the systems experience excessive nutrient loading, they vary in two key ways: sources of nutrients and manifestations of eutrophication ranging from HABs, to limited recreational uses, to the additional complexity of internal loadings and ﬁsh kills, up to drinking water shutdowns. The case studies were analyzed with respect to four categories of approaches, namely: (i) regulatory; (ii) incentive-based; (iii) risk mitigation; and (iv) outreach, engagement, and educational. We found that the management frameworks are based on integrated watershed management planning and national standards. National water quality standards, however, are not stringent enough to prevent HABs. Overall, identi ﬁed case studies did not successfully remediate HABs, they simply managed them.
1-To develop a cloud mask for water bodies (inland, coastal, and open ocean) based on a linear discriminant analysis algorithm using MODIS-D-250.
2-To establish a regional portray of algal bloom occurrence in Southern Quebec using a geospatial database describing bloom phenology (e.g. starting date, duration, intensity). 3-To develop a statistical model to evaluate the predisposition of lakes in developing algalblooms according to their physiographic and climatic characteristics.
1- From MODIS imagery to chlorophyll-a 2- Algal bloom portray in southern Quebec
Abstract. This paper describes the first use of aerial observations by a drone as an additional means for choosing sampling points during field studies of cyanobacterial harmful algalblooms (CyanoHABs) in selected Bulgarian waterbodies and the use of HPLC analysis of marker pigments for the fast determination of phytoplankton composition and biomass. The selection of waterbodies was based on the authors’ personal expertise and data collected over a 25-year period. In all sites chosen by drone, there were high levels of cyanobacteria and cyanotoxins were present: microcystins (MC-LR, MC-RR, MC-YR in Durankulak Lake and MC-LR and MC-RR in the Sinyata Reka Reservoir), cylindrospermopsin (in the Vaya Lake and in the Mandra Reservoir) and saxitoxins (in Durankulak Lake). The finding of cylindrospermopsin is the first in Bulgaria, the detection of saxitoxins is the first for Durankulak Lake and the microcystins records are the first for Sinyata Reka Reservoir. Considering the high total number of wetlands in Bulgaria, many of which are lowland, small and shallow and therefore vulnerable to CyanoHABs, we recommend further use of drones and HPLC in monitoring, which should speed up detection and reduce sampling efforts while enabling valuable information to be gathered.
18 the bivalve body. Thus, it can be speculated that the lower the filtration rate, the lower the level of parasite inside the host.
Bivalves have the ability to adapt filtration and ingestion rates (feeding activity) to plankton composition. Indeed, decreases in clearance and filtration rates of several bivalve species in the presence of toxic microalgae have been widely reported in the literature (e.g. Contreras et al., 2011; Hégaret et al., 2007c; Jauffrais et al., 2012; Lassus et al., 2007, 1999; Shumway, 1990). In oysters, reduction of A. minutum consumption seems to be mostly associated with algal BEC production, rather than to PST (Castrec et al., 2018). BECs irritate gills and, therefore, likely interfere with filtration or sorting functions and induce a protective behavioral response consisting of increased frequency of valve micro-closures (Castrec et al., 2018; Haberkorn et al., 2011; Tran et al., 2010). Conversely, contact with intracellular PSTs occurs mainly in the digestive organs after algal cell lysis. Pousse et al. (2018), however, demonstrated that a PST, non-BEC-producing strain of A. minutum also caused a decrease in feeding activity, thus suggesting the involvement of PST in filtration response. Furthermore, a recent study exposing mussels to Alexandrium spp. strains with different PST and BEC characteristics, also suggested that PSTs cause lower feeding activity (Bianchi et al., 2019). Such differences may, indeed, be caused by variability in both BEC and PST quality and quantity exposure in the two studies, or to different sensitivity of mussels and oysters.
This paper describes the design of experiments carried out in the East Johor Strait to study the dynamics of algalblooms. Physical and biogeochemical water column sampling were carried out using Acoustic Doppler Current Profilers (AD-CP) and a Conductivity, Temperature and Depth (CTD) probe that could measure various water quality parameters such as Turbidity, Salinity, pH level, Dissolved Oxygen (DO) and Chrolophyll-a concentration. Water samples from 1 m below the surface and 1 m above the channel floor were collected using Niskin Bottles. The water samples were sent to chemistry labs to test for the concentrations of various nutrients such as Ammonium, Nitrite, Nitrate and Phosphorus. Additional sampling was done using an Autonomous Underwater Vehicle (AUV) that was capable of measuring water quality parameters similiar to those measured by the CTD.
Now at CSIRO Land and Water, Environmental Remote Sensing Group, Australia.
Following validation activities and corresponding improvements in processing algorithms over the first few years of the MERIS mission, the algal1 and algal2 products are now considered as sufficiently mature for use in applications in Belgian waters. The utility of this product has been enhanced by the development of a number of multitemporal products including single point time series, multitemporal composites (monthly/3- monthly means) and annual products such as the mean and 90 percentile concentrations and the timing of the spring bloom. Marine management applications include: support for the assessment of eutrophication status in the context of the Oslo and Paris Convention for the Prevention of Marine Pollution (OSPAR), optimisation of seaborne monitoring, detection of harmful algalblooms and support for aquaculture. More generally, the MERIS data is used in support of marine science including the validation of ecosystem models and may be used in the future for the estimation of air-sea carbon fluxes. The current status of these applications is described together with an assessment of the remaining scientific challenges as well as the future possibilities.
For Peer Review
promised to reveal another level of complexity and importance in plant and algal physiology and development. The accessibility of Ultra Performance Liquid Chromatography-tandem Mass Spectrometry (UPLC-MS/MS), for example, has allowed the identification and quantification of not only major structural lipids but also of minor and transitory lipid-based signaling molecules. Matrix Assisted Laser
Microalgae are considered for their potential use as a feedstock, not only for biofuel production (Hu et al. (2008), Moheimani et al. (2015) ) but for a multitude of industries ranging from pharmaceutics to aquaculture (Benemann (1992), Borowitzka (1995) ). They can also contribute to recycle nitrogen and phosphorus within a wastewater treatment process. A keen interest in attached microalgae culture has been shown these past years. Flemming and Wingender (2010) define a biofilm as microorganisms that live in a self-produced matrix of extracellular polymeric substances (EPS). The latter are mainly polysaccharides, proteins, nucleic acids and lipids, all constitute a three dimensional polymer network that interconnects biofilm cells. The main advantage on using rotating algal biofilm (RAB) reactors is the reduced cost for harvesting, and the high productivity due to light dilution in time. In- deed, cells are never too long in sunlight, so that photo inhibition (damages due to excess of light energy), is mitigated. The time microalgae are exposed to light af- fect their growth, that is, after a longer exposition to high light intensity, the cells become photo-saturated and often inhibited. Photoinihibition is characterized by the denaturation of some key proteins contributing to the photosynthetic activity. RAB offer the possibility to regu- late light distribution through the biofilm by varying the rotational speed and therefore changing light exposure. The rotation also, allows the biofilm to be in permanent contact with the medium for the microalgae to survive and contribute to the biofilm formation. Christenson and Sims
Microalgae are microorganisms which have been only recently used for biotechnological applications, especially in the per- spective of biofuel production. Here we focus on the shape optimization and optimal control of an innovative process where the microalgae are fixed on a support. They are thus successively exposed to light and dark conditions. The resulting growth can be represented by a dynamical system describing the denaturation of key proteins due to an excess of light. A Partial Dif- ferential Equations (PDE) model of the Rotating Algal Biofilm (RAB) is then proposed, representing local microalgal growth submitted to the time varying light. An adjoint-based gradient method is proposed to identify the optimal (constant) process folding and the (time varying) velocity of the biofilm. When applied to a realistic case, the optimization points out a particular configuration which significantly increases the productivity compared to a base case where the biofilm is fixed.
Project-Teams ANGE and BIOCORE
Research Report n° 9250 — January 2019 — 22 pages
Abstract: Microalgae are microorganisms which have been only recently used for biotechnological
applications, especially in the perspective of biofuel production. Here we focus on the shape optimization and optimal control of an innovative process where the microalgae are fixed on a support. They are thus successively exposed to light and dark conditions. The resulting growth can be represented by a dynamical system describing the denaturation of key proteins due to an excess of light. A Partial Differential Equations (PDE) model of the Rotating Algal Biofilm (RAB) is then proposed, representing local microalgal growth submitted to the time varying light. An adjoint-based gradient method is proposed to identify the optimal (constant) process folding and the (time varying) velocity of the biofilm. When applied to a realistic case, the optimization points out a particular configuration which significantly increases the productivity compared to a base case where the biofilm is fixed.
Despite of these achievements, more efforts are still required to improve the simulation in terms of hydrodynamics, light attenuation or gas transfer in the algal bacterial system (Solimeno and García, 2017). Moreover, a guideline for selecting factors and framework in model construction simulating algal growth is also lacking (E. Lee et al., 2015). It was indicated that, the great variety of existing approaches with inadequate documentation usually lead to difficulty in assessment of simulation quality and comparability (Rieger et al., 2012). In addition, the lack of a standardized modeling procedure can cause inappropriate application of the model hence increasing the complexity, time consumption and the appreciation of modelers on the reliability of the models (Hauduc et al., 2009). Hence, it is necessary for a modeling project to respect standardized simulation protocol. These challenges were mostly addressed concerning ASM by the IWA Task Group on Good Modelling Practice (GMP) (Rieger et al., 2012). Therefore, in this study, the GMP Unified Protocol was chosen to follow due to its comprehensive coverage and dedication to wastewater treatment application. Based on the guideline, an insight into the model construction process as well as contribution of various sub-models on the results was aimed. As also suggested by the authors, instead of strictly following the protocol, adaptations were made from the original protocol in order to fit with HRAP system application (Rieger et al., 2012).
In the present study, we investigated the chronic effects of metals, combined to an increase in water temperature, on biofilm fatty acid composition and metal bioaccumulation. Studies have generally investigated the effects of temperature and metal exposure concentration separately or based on acute exposure and focused on organisms such as fishes and invertebrates or were conducted on monospecific algal cultures (e.g. Jiang and Gao (2004)). However, the interaction between these factors and the resulting multi-stress effects on biofilms at the base of aquatic food webs require additional investigation to more adequately quantify the response of the biota and to improve risk assessment for aquatic ecosystems. Our study provides evidence that an increase in temperature is accompanied by a decrease in the unsaturation degree in biofilm FA as a response to thermal stress. Nickel exposure also resulted in a decrease in PUFA, suggesting that the effects of these two stressors are additive. However, Ni bioaccumulation was similar for both tested temperatures.
[ 1 ] Frontal systems in the Southern Ocean are known
for their enhanced biological activity, with some tantalising suggestions that this enhancement may be intermittent. We have used frequent satellite ocean colour observations to investigate the Subtropical Convergence south of Africa. We demonstrate that the biological enhancement takes place as episodic chlorophyll bloom events with limited spatial and temporal scales. Most of the events appear in austral spring-summer. Two typical lifetimes, 8 – 24 and 40 – 60 days, emerge unambiguously during these seasons. A similar analysis has been carried out on modelled chlorophyll fields to investigate the physical-biogeochemical causes for such events. Strong and swift stratification, alleviating the light limitation on growth of phytoplankton, causes the appearance of a bloom. A mixed layer depth expansion subsequently leads to a rapid disappearance of the simulated event. Phytoplankton horizontal transport, either zonal or meridional, also plays a key role on the lifetime of the bloom events. Citation: Llido, J., V. Garc¸on, J. R. E. Lutjeharms, and J. Sudre (2005), Event-scale blooms drive enhanced primary productivity at the Subtropical Convergence, Geophys. Res. Lett., 32, L15611, doi:10.1029/2005GL022880.
Figure 8: Influence of carbonation on colonization rate (black dots: pH=9; white dots:pH=12) of CEMI
Moreover, colonization begins after 5 days for the carbonated samples whereas 10 days are necessary for the uncarbonated mortars. The half colonization time is of 12 days for carbonated mortar while uncarbonated mortars are colonized at 50% after approximately 30 days. A sharp drop is observed for uncarbonated CEMI samples of smooth surface which results from algal agglomerates detachment. The difference in colonization rate between rough and smooth surfaces is slight.