Electro-flocculation of aquaculture wastewater microalgal communities reduces nutrient loading.

Land-based aquaculture provides dietary protein to the world's population in a sustainable way, but issues related to release of nitrogen rich wastewater limits its expansion. Sedimentation of naturally occurring microalgae that assimilate excess nitrogen, is slow and land intensive. Electro-flocculation, used in wastewater treatment processes, is a potential alternative for aquaculture. Trials of different electro-flocculation configurations applied to three prawn farm pondwater samples containing varying microalgal assemblages are reported. In 64 % of trials, electro-flocculation reduced total nitrogen (TN) and dissolved inorganic nitrogen (DIN) loads within regulatory limits.TN was reduced up to 83.2 % (10.93 to 1.83 mg.L-1) within 20 mins in stationary water, and DIN to 90.6 % (3.19 to 0.30 mg.L-1) in 102 mins trials in flowing water. Bellerochea andGloeocapsa spp. were dominant in wastewater. The role of microalgal community composition on flocculation is discussed, including evidence Bellerocheapromotes flocculation. This study confirmed electro-flocculation quickly reduces TN and DIN.

Comprehensive analysis of spatial distribution of microplastics in Rawal Lake, Pakistan using trawl net and sieve sampling methods.

Occurrence of microplastics (MPs) in freshwater environments, particularly reservoir and lakes, is an emerging concern. There are limited studies in Pakistan on microplastic pollution in the lacustrine environments and those that exist do not provide sufficient information on the spatial distribution of MPs in offshore surface water. The aims of this study were to determine microplastic abundance in Rawal Lake, Pakistan and to ascertain if sampling methodology influences microplastic counts. Surface water samples were collected from 10 sites; 5 tributaries, 2 human settlement and 3 fishing and boating areas using two different sampling techniques: 100 µm mesh trawl and 20 L sample through a 45 µm mesh sieve. A significant difference was observed in the abundance of MPs across two methods with the sieve method yielding 2.8 ± 1.44 particles/L and trawl yielding 0.025 ± 0.024 particles/L. Tributaries and boating/fishing area had higher microplastic abundance than the residential area regardless of sampling method. Filaments were the dominant shape of MPs in both type of samples followed by fragments in trawl samples and films in sieved samples. Microbeads were only detected in trawl samples. MPs within size range 0.1-0.9 mm were mostly fragments (82%). MPs were diverse in colors with white/transparent and black MPs common. Polypropylene was the main type of microplastic in Rawal Lake (40-74%). Scanning Electron Microscopy (SEM) of MPs showed cracks, roughness and striations on the particles. Energy Dispersive Spectroscopy (EDS) detected heavy metals (Fe, Cu, Ni, Pb, Zn, Co and Cr) in MPs. Findings suggest that microplastic pollution in Rawal Lake may pose great risk to aquatic and human life through leaching of inherent/adsorbed heavy metals and therefore requires future investigation.

The abundance of microplastics in cnidaria and ctenophora in the North Sea.

Microplastic (MP) ingestion has been widely recorded in aquatic organisms, but few studies focus on cnidarians and ctenophores, which form a significant contribution to marine trophic interactions. Scyphozoans (Cyanea capillata, C. lamarckii and Aurelia aurita), hydrozoan (Cosmetira pilosella) and ctenophores (Beroe cucumis and Pleurobrachia bachei) collected opportunistically from Orkney, Shetland and the North Sea were thermally disintegrated, with a subsample of ingested plastics analysed using FTIR. A total of 1,986 MPs were counted (94% fibres), the majority (84.4%) in the four cnidarian species. Highest MP concentrations were recorded in B. cucumis (0.956 ml-1), whilst C. pilosella yielded the lowest (0.014 ml-1). The main polymers in digestate were PET and PP, with 27% discounted as non-plastics. In feeding trials, A. aurita ingested a greater quantity of PET fibres (60-80%), compared to nylon (0%) and HDPE fibres (0%). This study demonstrates cnidarians and ctenophores, a largely overlooked group, are a potential route for MPs entry into food webs.

Microplastic accumulation in a Zostera marina L. bed at Deerness Sound, Orkney, Scotland.

Seagrasses have global distribution and are highly productive and economically valuable habitats. They are sensitive and vulnerable to a range of human-induced pressures, including ongoing exposure to marine litter, such as microplastic particles (<5 mm). In this study, a Zostera marina bed in Deerness Sound, Orkney was selected to determine whether microplastics accumulate in seagrass beds and adhere to seagrass blades. Sediment, seagrass blade, biota and seawater samples were collected. 280 microplastic particles (0.04 to 3.95 mm (mean = 0.95 mm ±â€¯0.05 SE)) were observed in 94% of samples collected (n = 111). These were visually categorised into type (fibre, flake, fragment) and colour, and 50 were successfully identified as plastic using ATR-FTIR. Fibres contributed >50% of the total microplastics observed across all samples. This is the first known study on Z. marina to describe microplastic loading within a seagrass bed and to identify microplastic adherence to seagrass blades.

An investigation into ciguatoxin bioaccumulation in sharks.

Ciguatoxins (CTXs) produced by benthic Gambierdiscus dinoflagellates, readily biotransform and bioaccumulate in food chains ultimately bioconcentrating in high-order, carnivorous marine species. Certain shark species, often feeding at, or near the top of the food-chain have the ability to bioaccumulate a suite of toxins, from both anthropogenic and algal sources. As such, these apex predators are likely sinks for CTXs. This assumption, in conjunction with anecdotal knowledge of poisoning incidents, several non-specific feeding trials whereby various terrestrial animals were fed suspect fish flesh, and a single incident in Madagascar in 1994, have resulted in the widespread acceptance that sharks may accumulate CTXs. This prompted a study to investigate original claims within the literature, as well as investigate CTX bioaccumulation in the muscle and liver of 22 individual sharks from nine species, across four locations along the east coast of Australia. Utilizing an updated ciguatoxin extraction method with HPLC-MS/MS, we were unable to detect P-CTX-1, P-CTX-2 or P-CTX-3, the three primary CTX congeners, in muscle or liver samples. We propose four theories to address this finding: (1) to date, methods have been optimized for teleost species and may not be appropriate for elasmobranchs, or the CTXs may be below the limit of detection; (2) CTX may be biotransformed into elasmobranch-specific congeners as a result of unique metabolic properties; (3) 22 individuals may be an inadequate sample size given the rare occurrence of high-order ciguatoxic organisms and potential for CTX depuration; and (4) the ephemeral nature and inconsistent toxin profiles of Gambierdiscus blooms may have undermined our classifications of certain areas as CTX hotspots. These results, in combination with the lack of clarity within the literature, suggest that ciguatoxin bioaccumulation in sharks remains elusive, and warrants further investigation to determine the dynamics of toxin production, accumulation and transformation throughout the entire food-web.

An updated ciguatoxin extraction method and silica cleanup for use with HPLC-MS/MS for the analysis of P-CTX-1, PCTX-2 and P-CTX-3.

Ciguatera fish poisoning is a debilitating human neuro-intoxication caused by consumption of tropical marine organisms, contaminated with bioaccumulated ciguatoxins (CTXs). The growing number of cases coupled with the high toxicity of CTXs makes their reliable detection and quantification of paramount importance. Three commonly occurring ciguatoxins, P-CTX-1, 2 and 3 from five different ciguatoxic Spanish mackerel (Scomberomorus commerson), were used to assess the effectiveness of different extraction techniques: homogenization (high powered blending vs. ultrasonication); C-18 column sizes (500 mg vs. 900 mg); and a novel HILIC SPE cleanup. Despite minor differences, blending and sonication proved equally effective. Larger 900 mg columns offered a greater extraction efficiency, increasing detected P-CTX-1 by 37% (P < 0.001). The newly adapted cleanup was highly effective at reducing co-eluting phospholipids thereby reducing matrix effects and increasing detectable CTXs by HPLC-MS/MS. Silica cleanup extraction efficiencies were also compared between the highly effective and validated ciguatoxin rapid extraction method (CREM) and current best practice extraction method employed by Queensland Health (QH). Overall, the QH protocol proved more effective, especially when paired with the newly adapted cleanup, as this increased the amount of extracted P-CTX-1 by 46% (P < 0.01), P-CTX-2 by 10% and P-CTX-3 by 71% (P = 0.001). This study suggests the QH protocol utilizing a 900 mg C-18 column and newly adapted HILIC SPE cleanup was most effective at extracting P-CTX-1, -2, -3. Specifically P-CTX-1, the primary ciguatoxin congener of concern due to its extremely high potency and an ability to cause CFP at 0.1 µg/kg following consumption of carnivorous fish flesh. Despite being more time intensive (an additional 85 min per batch of 12 samples), this will be especially effective for assessing lower toxin burdens, which may be near the limit of detection.

Ecology- and bioassay-guided drug discovery for treatments of tropical parasitic disease: 5alpha,8alpha-epidioxycholest-6-en-3beta-ol isolated from the mollusk Dolabrifera dolabrifera shows significant activity against Leishmania donovani.

An ecology- and bioassay-guided search employed to discover compounds with activity against tropical parasitic diseases and cancer from the opisthobranch mollusk, Dolabrifera dolabrifera, led to the discovery of antileishmanial properties in the known compound, 5alpha,8alpha-epidioxycholest-6-en-3beta-ol (1). Compound 1 was identified through nuclear magnetic resonance spectroscopy (1H, 13C) and mass spectrometry. The compound was concentrated in the digestive gland of D. dolabrifera, but was not detected in other body parts, fecal matter or mucus. Compound 1 showed an IC50 of 4.9 microM towards the amastigote form of Leishmania donovani compared with an IC50 of 281 microM towards the control Vero cell line, a 57.3-fold difference, and demonstrated no measurable activity against Plasmodium falciparum, Trypanosoma cruzi, and the breast cancer cell line, MCF-7.

The fate of Lyngbya majuscula toxins in three potential consumers.

Blooms of Lyngbya majuscula have been reported with increasing frequency and severity in the last decade in Moreton Bay, Australia. A number of grazers have been observed feeding upon this toxic cyanobacterium. Differences in sequestration of toxic compounds from L. majuscula were investigated in two anaspideans, Stylocheilus striatus, Bursatella leachii, and the cephalaspidean Diniatys dentifer. Species fed a monospecific diet of L. majuscula had different toxin distribution in their tissues and excretions. A high concentration of lyngbyatoxin-a was observed in the body of S. striatus (3.94 mg/kg(-1)) compared to bodily secretions (ink 0.12 mg/kg(-1); fecal matter 0.56 mg/kg(-1); eggs 0.05 mg/kg(-1)). In contrast, B. leachii secreted greater concentrations of lyngbyatoxin-a (ink 5.41 mg/kg(-1); fecal matter 6.71 mg/kg(-1)) than that stored in the body (2.24 mg/kg(-1)). The major internal repository of lyngbyatoxin-a and debromoaplysiatoxin was the digestive gland for both S. striatus (6.31 +/- 0.31 mg/kg(-1)) and B. leachii (156.39 +/- 46.92 mg/kg(-1)). D. dentifer showed high variability in the distribution of sequestered compounds. Lyngbyatoxin-a was detected in the digestive gland (3.56 +/- 3.56 mg/kg(-1)) but not in the head and foot, while debromoaplysiatoxin was detected in the head and foot (133.73 +/- 129.82 mg/kg(-1)) but not in the digestive gland. The concentrations of sequestered secondary metabolites in these animals did not correspond to the concentrations found in L. majuscula used as food for these experiments, suggesting it may have been from previous dietary exposure. Trophic transfer of debromoaplysiatoxin from L. majuscula into S. striatus is well established; however, a lack of knowledge exists for other grazers. The high levels of secondary metabolites observed in both the anaspidean and the cephalapsidean species suggest that these toxins may bioaccumulate through marine food chains.