Spatial and Temporal Patterns in <Emphasis Type="Italic">Thalassia testudinum</Emphasis> Leaf Tissue Nutrients at the Chandeleur Islands,Louisiana, USA

Seagrasses are submerged marine plants that are anchored to the substrate and are therefore limited to assimilating nutrients from the surrounding water column or sediment, or by translocating nutrients from adjacent shoots through the belowground rhizome. As a result, seagrasses have been used as reliable ecosystem indicators of surrounding nutrient conditions. The Chandeleur Islands are a chain of barrier islands in the northern Gulf of Mexico that support the only marine seagrass beds in Louisiana, USA, and are the sole location of the seagrass Thalassia testudinum across nearly 1000 km of the coastline from west Florida to central Texas. Over the past 150 years, the land area of the Chandeleur Islands has decreased by over half, resulting in a decline of seagrass cover. The goals of this study were to characterize the status of a climax seagrass species at the Chandeleur Islands, T. testudinum, in terms of leaf nutrient (nitrogen [N] and phosphorus [P]) changes over time, from 1998 to 2015, and to assess potential drivers of leaf nutrient content. Thalassia testudinum leaf nutrients displayed considerable interannual variability in N and P content and molar ratios, which broadly mimicked patterns in annual average dissolved nutrient concentrations in the lower Mississippi River. Hydrological modeling demonstrated the potential for multiple scenarios that would deliver Mississippi River water, and thus nutrients, to T. testudinum at the Chandeleur Islands. Although coastal eutrophication is generally accepted as the proximate cause for seagrass loss globally, there is little evidence that nutrient input from the Mississippi River has driven the dramatic declines observed in seagrasses at the Chandeleur Islands. Rather, seagrass cover along the Chandeleur Islands appears to be strongly influenced by island geomorphological processes. Although variable over time, the often elevated nutrient levels of the climax seagrass species, T. testudinum, which are potentially driven by river-derived nutrient inputs, raises an important consideration of the potential loss of the ecosystem functions and services associated with these declining seagrass meadows.     

Fertilization Changes Seagrass Community Structure but not Blue Carbon Storage: Results from a 30-Year Field Experiment

Seagrass ecosystems are attracting attention as potentially important tools for carbon (C) sequestration, comparable to those terrestrial and aquatic ecosystems already incorporated into climate change mitigation frameworks. Despite the relatively low C stocks in living biomass, the soil organic carbon pools beneath seagrass meadows can be substantial. We tested the relationship between soil C storage and seagrass community biomass, productivity, and species composition by revisiting meadows experimentally altered by 30 years of consistent nutrient fertilization provided by roosting birds. While the benthos beneath experimental perches has maintained dense, Halodule wrightii-dominated communities compared to the sparse Thalassia testudinum-dominated communities at control sites, there were no significant differences in soil organic carbon stocks in the top 15 cm. Although there were differences in δ¹³C of the dominant seagrass species at control and treatment sites, there was no difference in soil δ¹³C between treatments. Averages for soil organic carbon content (2.57?±?0.08 %) and δ¹³C (?12.0?±?0.3?‰) were comparable to global averages for seagrass ecosystems; however, our findings question the relevance of local-scale seagrass species composition or density to soil organic carbon pools in some environmental contexts.     

Distribution of benthic foraminiferal assemblages in the transitional environment of the Djerba lagoon (Tunisia)

The eastern edge of the Djerba Island represents an important tourist pole. However, studies describing the environmental processes affecting this Island are scarce. Although never studied before, the peculiar Djerba lagoon is well known by the local population and by tourists. In July 2014, surface sediment and seawater samples were collected in this lagoon to measure grain size, organic matter content and living foraminiferal assemblages to describe environmental conditions. Seawater samples were also collected and the concentration of 17 chemical elements were measured by ICP-OES. The results show that a salinity gradient along the studied transect clearly impacts seagrass distribution, creating different environmental conditions inside the Djerba lagoon. Biotic and abiotic parameters reflect a transitional environment from hypersaline to normal marine conditions. Living benthic foraminifera show an adaptation to changing conditions within the different parts of the lagoon. In particular, the presence of Ammonia spp. and Haynesina depressula correlates with hypersaline waters, whilst Brizalina striatula characterizes the parts of the lagoon colonized by seagrass. Epifaunal species, such as Rosalina vilardeboana and Amphistegina spp. colonize hard substrata present at the transition between the lagoon and the open sea.     

Functional,Phylogenetic and Host-Geographic Signatures of <Emphasis Type="Italic">Labyrinthula</Emphasis> spp. Provide for Putative Species Delimitation and a Global-Scale View of Seagrass Wasting Disease

Seagrass meadows form ecologically and economically valuable coastal habitat on every continental margin except the Antarctic, but their areal extent is declining by approximately 2–5 % per year. Seagrass wasting disease is a contributing factor in these declines, with the protist Labyrinthula identified as the etiologic agent. To help elucidate the role of Labyrinthula spp. in global seagrass declines, we surveyed roughly one fourth of all seagrass species to identify Labyrinthula diversity at the strain and/or species level, combining results from culturing methods and two common nuclear DNA markers: the ITS and 18S regions of the ribosomal RNA gene complex. After assaying a subset of the resulting isolates (of which 170 were newly sequenced), we produced a cladogenic context for putative seagrass-pathogenic versus non-pathogenic Labyrinthula while also defining host and geographic ranges. Assays also suggest that pathogenicity is consistently high (when present; and, even when comparing susceptibility of US East- versus West Coast Zostera marina hosts) while virulence is variable, that some isolate-host combinations have the potential for host cross-infection, and that several modes of transmission can be effective. Taken together, these data provide additional means for delimiting putative species of Labyrinthula, suggesting at least five seagrass-pathogenic and perhaps ten or more non-pathogenic marine “species”, yielding a working definition for ecologists and epidemiologists attempting to reconcile the sundry data related to seagrass wasting disease.     

Isotopic and Elemental Composition of Marine Macrophytes as Biotracers of Nutrient Recycling Within a Coastal Lagoon in Baja California,Mexico

Nutrient sources of San Quintin Bay, a coastal lagoon affected by coastal upwelling off Baja California (Mexico), were traced using generalized additive (mixed) models (GAMM) to the stable nitrogen isotopic composition, C:N and N content of two co-occurring macrophytes (the macroalgae Ulva spp. and the seagrass Zostera marina). The geochemical tracers followed a spatial trend that partly responded to the long-term nutrient gradient from the ocean towards the interior of the bay. N content in Z. marina and Ulva spp. decreased linearly (while C:N increased) towards the middle section of the bay to concentration levels that indicate potential N limitation for growth. Concurrently midway into the bay (6–9 km), the δ¹⁵N of both macrophytes showed a gradual enrichment in ¹⁵N reflecting progressive denitrification. The spatial pattern of δ¹⁵N and the decrease in C:N of the macrophytes towards the innermost section of the bay indicated an additional nonoceanic source of dissolved nitrogen in this zone. The similarity of the δ¹⁵N pattern of Z. marina and Ulva spp. implies that their δ¹⁵N composition is mainly controlled by the availability of N, in spite of the physiological differences between taxa. A better fit of GAMM to N content and C:N was obtained for Z. marina than for Ulva spp. indicating that the former delineate more steadily and smoothly the influence of upwelling along the spatial gradient. Nonetheless, Ulva spp. may be analyzed in combination with Z. marina to characterize the environmental conditions at the time of sampling.     

Salinity Tolerance and Competition Drive Distributions of Native and Invasive Submerged Aquatic Vegetation in the Upper San Francisco Estuary

Both abiotic and biotic factors govern distributions of estuarine vegetation, and experiments can reveal effects of these drivers under current and future conditions. In upper San Francisco Estuary (SFE), increased salinity could result from sea level rise, levee failure, or water management. We used mesocosms to test salinity effects on, as well as competition between, the native Stuckenia pectinata (sago pondweed) and invasive Egeria densa (Brazilian waterweed), species with overlapping distributions at the freshwater transition in SFE. Grown alone at a salinity of 5, E. densa decreased fivefold in biomass relative to the freshwater treatment and decomposed within 3 weeks at higher salinities. In contrast, S. pectinata biomass accumulated greatly (~4× initial) at salinities of 0 and 5, doubled at 10, and was unchanged at 15. When grown together in freshwater, S. pectinata produced 75 % less biomass than in monoculture and significantly more nodal roots (suggesting increased nutrient foraging). At a salinity of 5, a decline in E. densa performance coincided with a doubling of S. pectinata shoot density. Additional experiments on E. densa showed elevated temperature (26 and 30 °C) suppressed growth especially at higher salinities (≥5). We conclude that salinity strongly influences distributions of both species and that competition from E. densa may impose limits on S. pectinata abundance in the fresher reaches of SFE. With a salinity increase of 5, S. pectinata is likely to maintain its current distribution while spreading up-estuary at the expense of E. densa, especially if increased temperature also reduces E. densa biomass.     

The Bloom-Forming Macroalgae, <Emphasis Type="Italic">Ulva</Emphasis>, Outcompetes the Seagrass, <Emphasis Type="Italic">Zostera marina</Emphasis>, Under High CO<Subscript>2</Subscript> Conditions

While multiple species of macroalgae and seagrass can benefit from elevated CO₂ concentrations, competition between such organisms may influence their ultimate responses. This study reports on experiments performed with a Northwest Atlantic species of the macroalgae, Ulva, and the seagrass, Zostera marina, grown under ambient and elevated levels of pCO₂, and subjected to competition with each other. When grown individually, elevated pCO₂ significantly increased growth rates and productivity of Ulva and Zostera, respectively, beyond control treatments (by threefold and 27%, respectively). For both primary producers, significant declines in tissue δ¹³C signatures suggested that increased growth and productivity were associated with a shift from use of HCO₃^? toward CO₂ use. When grown under higher pCO₂, Zostera experienced significant increases in leaf and rhizome carbon content as well as significant increases in leaf carbon-to-nitrogen ratios, while sediments within which high CO₂ Zostera were grown had a significantly higher organic carbon content. When grown in the presence of Ulva; however, above- and below-ground productivity and tissue nitrogen content of Zostera were significantly lower, revealing an antagonistic interaction between elevated CO₂ and the presence of Ulva. The presence of Zostera had no significant effect on the growth of Ulva. Collectively, this study demonstrates that while Ulva and Zostera can each individually benefit from elevated pCO₂ levels, the ability of Ulva to grow more rapidly and inhibit seagrass productivity under elevated pCO₂, coupled with accumulation of organic C in sediments, may offset the potential benefits for Zostera within high CO₂ environments.     

Adaptation of <Emphasis Type="Italic">Shigella flexneri</Emphasis> to starvation: morphology,outer membrane proteins and lipopolysaccharide changes

Lack of nutrients is a common challenge for enteric pathogens, like Shigella, when discharged in waters and soils by infected persons. These bacteria must evolve protective mechanisms to survive nutrient changing conditions. Many studies have demonstrated that bacterial starvation can affect cell morphology and surface properties such as lipopolysaccharide content. This study focuses on the morphological and physiological alterations of Shigella flexneri, a human pathogen, under nutrient starvation during 30 days. Our results showed that S. flexneri can survive under nutrient deficiency during 4 weeks. However, starved cells revealed several morphological changes indicating decrease of the size and change of the cell shape as observed by transmission electron microscopy. Furthermore, the outer membrane proteins and lipopolysaccharide profiles of starved cells revealed the disappearance, the appearance, and changes of the protein band levels. The survival and physiological adaptation of S. flexneri under nutrient limitation during 30 days may increase the risk of human and animal infections.     

Spatial and Temporal Variations in <Emphasis Type="Italic">Pyrodinium bahamense</Emphasis> Cyst Concentrations in the Sediments of Bioluminescent Mangrove Lagoon,St. Croix,USVI

Mangrove Lagoon, located on the island of St. Croix, US Virgin Islands (USVI), is one of few actively bioluminescent lagoons in a location experiencing significant anthropogenic impacts. The bioluminescence is due to an abundance of the dinoflagellate Pyrodinium bahamense in the water column. We recovered surface sediments and sediment cores from Mangrove Lagoon to analyze the spatial distribution and temporal variability of P. bahamense cysts in this system. Surface sediment P. bahamense cyst concentrations ranged from 0 to 466 cysts g^?1 dry sediment, with higher abundances associated with elevated surface water nutrient concentrations and a mixed terrestrial–marine organic matter source regime. In combination with available bioassay data, we hypothesize that phytoplankton utilize nutrients rapidly and subsequent decay of organic matter makes nutrients available for dinoflagellates at the sediment–water interface in the eastern and northern quadrants of the lagoon. However, the nutrients are rapidly exhausted during counterclockwise lagoon circulation resulting in the decline of primary productivity and dinoflagellate abundance in the western quadrants. Downcore profiles suggest that P. bahamense blooms have been occurring for decades, declining in recent years. No cysts were present in sediments predating dredging activities of the 1960s that created Mangrove Lagoon. Recent reductions in cyst abundance may be the result of limited primary productivity caused by restricted water exchange with Salt River Bay due to shallowing of a sill at the mouth of the lagoon. This research highlights the need for more comprehensive geochemical and fossil analyses to better understand long-term ecological variability and inform conservation efforts of these unique habitats.     

Permian Calcareous algae from the Khachik Formation at the Ali Bashi Mountains,NW of Iran

Micropaleontological investigations on Permian successions in the NW of Iran based on algae led to the determination of taxa belonging to some families such as Ungdarellaceae (Ungdarella uralica), Gymnocodiaceae (Gymnocodium bellerophontis and Permocalculus sp.), Dasycladales (Mizzia cf. M. yabei), and some microproblematics (Vermiporella nipponica and Pseudovermiporella sodalica). These investigations are mainly focused on the Khachik Formation at the Ali Bashi Mountains. According to the algal community, a lagoon environment is offered for the studied successions.     

Biogeochemistry of a River-Dominated Estuary Influenced by Drought and Storms

Increased frequency and severity of droughts, as well as growing human freshwater demands, in the Apalachicola-Chattahoochee-Flint River Basin are expected to lead to a long-term decrease in freshwater discharge to Apalachicola Bay (Florida). To date, no long-term studies have assessed how river discharge variability affects the Bay’s phytoplankton community. Here a 14-year time series was used to assess the influence of hydrologic variability on the biogeochemistry and phytoplankton biomass in Apalachicola Bay. Data were collected at 10 sites in the bay along the salinity gradient and include drought and storm periods. Riverine dissolved inorganic nitrogen and phosphate inputs were correlated to river discharge, but chlorophyll a (Chl a) was similar between periods of drought and average/above-average river discharge in most of the Bay. Results suggest that the potentially negative impact of decreased riverine nutrient input on Bay phytoplankton biomass is mitigated by the nutrient buffering capacity of the estuary. Additionally, increased light availability, longer residence time, and decreased grazing pressures may allow more Chl a biomass to accumulate during drought. In contrast to droughts, tropical cyclones and subsequent increases in river discharge increased flushing and reduced light penetration, leading to reduced Chl a in the Bay. Analysis of the time series revealed that Chl a concentrations in the Bay do not directly mirror the effect of riverine nutrient input, which is masked by multiple interacting mechanisms (i.e., nutrient loading and retention, grazing, flushing, light penetration) that need to be considered when projecting the response of Bay Chl a to changes in freshwater input.     

Seasonal variation in standing crop of the seagrassSyringodium filiforme and associated macrophytes in the Northern Indian River,Florida

Seasonal variation in the standing crop of the seagrassSyringodium filiforme and its associated macrophytes was studied in a northern basin of the Indian River, a large mesohaline lagoon in central Florida, near the northern distributional limit ofS. filiforme. The minimum standing crop occurred from February through April and the maximum in September. Two other seagrasses,Halodule wrightii andHalophila engelmannii, together with a drift algal community, occurred in the study quadrat, but were not major components of the macrophytic system. The formation of sizeable sandy patches within Indian River seagrass beds is partially due to the burrowing activities ofLimulus polyphemus. Thermal stresses associated with the northern geographicalS. filiforme range may contribute to this phenomenon by restricting annual production, hence limiting patch regrowth.     

Sulfate Reduction and Sulfur Cycles at Two Seagrass Beds Inhabited by Cold Affinity <Emphasis Type="Italic">Zostera marina</Emphasis> and Warm Affinity <Emphasis Type="Italic">Halophila nipponica</Emphasis> in Temperate Coastal Waters

To evaluate the impact of invading seagrass on biogeochemical processes associated with sulfur cycles, we investigated the geochemical properties and sulfate reduction rates (SRRs) in sediments inhabited by invasive warm affinity Halophila nipponica and indigenous cold affinity Zostera marina. A more positive relationship between SRR and below-ground biomass (BGB) was observed at the H. nipponica bed (SRR = 0.6809 × BGB ? 4.3162, r ² = 0.9878, p = 0.0006) than at the Z. marina bed (SRR = 0.3470 × BGB ? 4.0341, r ² = 0.7082, p = 0.0357). These results suggested that SR was more stimulated by the dissolved organic carbon (DOC) exuded from the roots of H. nipponica than by the DOC released from the roots of Z. marina. Despite the enhanced SR in spring-summer, the relatively lower proportion (average, 20%) of acid-volatile sulfur (AVS) in total reduced sulfur and the strong correlation between total oxalate-extractable Fe (Fe_(oxal)) and chromium-reducible sulfur (CRS = 0.2321 × total Fe_(oxal) + 1.8180, r ² = 0.3344, p = 0.0076) in the sediments suggested the rapid re-oxidation of sulfide and precipitation of sulfide with Fe. The turnover rate of the AVS at the H. nipponica bed (0.13 day^?1) was 2.5 times lower than that at the Z. marina bed (0.33 day^?1). Together with lower AVS turnover, the stronger correlation of SRR to BGB in the H. nipponica bed suggests that the extension of H. nipponica resulting from the warming of seawater might provoke more sulfide accumulation in coastal sediments.     

Representatives of genera <Emphasis Type="Italic">Malbosiceras</Emphasis> and <Emphasis Type="Italic">Pomeliceras</Emphasis> (Neocomitidae,Ammonoidea) from the Berriasian of the Crimean Mountains

The revised representatives of ammonite genera Malbosiceras and Pomeliceras from the Berriasian of the Crimean Mountains are classed with seven species, four of the first genus [M. malbosi (Pictet), M. chaperi (Pictet), M. broussei (Mazenot), M. pictetiforme Tavera] and three of the second one [P. aff. boisseti Nikolov, P. breveti (Pomel), P. (?) funduklense Lysenko et Arkadiev sp. nov.]. The identified species are described. The genus Mazenoticeras is considered as synonym of Malbosiceras. The above species prove that all the Berriasian zones (jacobi, occitanica and boissieri) are characteristic of corresponding deposits in the Crimean Mountains.     

Elastic behavior of vanadinite,Pb<Subscript>10</Subscript>(VO<Subscript>4</Subscript>)<Subscript>6</Subscript>Cl<Subscript>2</Subscript>, a microporous non-zeolitic mineral

The high-pressure behavior of a vanadinite (Pb₁₀(VO₄)₆Cl₂, a = b = 10.3254(5), c = 7.3450(4) Å, space group P6₃/m), a natural microporous mineral, has been investigated using in-situ HP-synchrotron X-ray powder diffraction up to 7.67 GPa with a diamond anvil cell under hydrostatic conditions. No phase transition has been observed within the pressure range investigated. Axial and volume isothermal Equations of State (EoS) of vanadinite were determined. Fitting the P–V data with a third-order Birch-Murnaghan (BM) EoS, using the data weighted by the uncertainties in P and V, we obtained: V ₀ = 681(1) Å³, K ₀ = 41(5) GPa, and K′ = 12.5(2.5). The evolution of the lattice constants with P shows a strong anisotropic compression pattern. The axial bulk moduli were calculated with a third-order “linearized” BM-EoS. The EoS parameters are: a ₀ = 10.3302(2) Å, K ₀(a) = 35(2) GPa and K′(a) = 10(1) for the a-axis; c ₀ = 7.3520(3) Å, K ₀(c) = 98(4) GPa, and K′(c) = 9(2) for the c-axis (K ₀(a):K ₀(c) = 1:2.80). Axial and volume Eulerian-finite strain (fe) at different normalized stress (Fe) were calculated. The weighted linear regression through the data points yields the following intercept values: Fe _a (0) = 35(2) GPa for the a-axis, Fe _c (0) = 98(4) GPa for the c-axis and Fe _V (0) = 45(2) GPa for the unit-cell volume. The slope of the regression lines gives rise to K′ values of 10(1) for the a-axis, 9(2) for the c-axis and 11(1) for the unit cell-volume. A comparison between the HP-elastic response of vanadinite and the iso-structural apatite is carried out. The possible reasons of the elastic anisotropy are discussed.     

Systematic paleontology,biostratigraphy, paleobiogeography of <Emphasis Type="Italic">Loftusia</Emphasis> (foraminifera) and <Emphasis Type="Italic">Rudist</Emphasis> assemblages in a regressive sequence in the Hekimhan-Malatya area (Eastern Anatolia) Turkey

The Maastrichtian regressive sequence of the Hekimhan-Malatya area in Eastern Turkey consists of dolomitic limestones, limestones and calcareous mudstones which are dominated by rudists and Loftusia (foraminifera) assemblages. Several Loftusia species indicating middle to late Maastrichtian age such as Loftusia anatolica Meriç, L. baykali Meriç, L. coxi Henson, L. harrisoni Cox, L. minor Cox and L. morgani Douvillé have been recorded. Other benthic foraminifers present include Orbitoides medius d’ Archiac, Omphalocyclus macroporus (Lamarck), Laffitteina conica Drooger, Laffitteina mengaudi (Astre) and Laffitteina oeztuerki Inan. The rudists are abundant in the dolomitic limestones in the study area. The genus Miseia Patrulius is dominant and represented by Miseia bilacunosa Özer and Miseia hekimhanensis Karacabey-Öztemür. The Loftusia species and the Rudists assemblage indicates middle to late Maastrichtian age for the formation. The paleobiogeographic distribution of the assemblage has been discussed taking this find into account.     

<Emphasis Type="Italic">Salpingoporella</Emphasis> (dasycladalean algae) species from the Lower Cretaceous carbonate facies of Kopet Dagh basin (NE Iran)

Salpingoporella species from algal bearing of Barremian-Aptian limestones in the Kopet Dagh basin (NE of Iran) are described. Different species (S. cemi, S. hasi, S. heraldica, S. hispanica, S. milovanovici, S. muehlmbergi, S. parapiriniae, S. piriniae, S. cf. biokovensis, S. steinhauseri, S. polygonalis) are investigated from different biometrical aspects such as depositional environments and biogeographical distribution as well as their systematic palaeontology from two formations (the Tirgan and Sarcheshmeh formations) in nine stratigraphic sections.     

Compressibility of strontium orthophosphate Sr<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript> at high pressure

High pressure in situ synchrotron X-ray diffraction experiment of strontium orthophosphate Sr₃(PO₄)₂ has been carried out to 20.0 GPa at room temperature using multianvil apparatus. Fitting a third-order Birch–Murnaghan equation of state to the P–V data yields a volume of V ₀ = 498.0 ± 0.1 Å³, an isothermal bulk modulus of K _T  = 89.5 ± 1.7 GPa, and first pressure derivative of K _T ′ = 6.57 ± 0.34. If K _T ′ is fixed at 4, K _T is obtained as 104.4 ± 1.2 GPa. Analysis of axial compressible modulus shows that the a-axis (K _a  = 79.6 ± 3.2 GPa) is more compressible than the c-axis (K _c  = 116.4 ± 4.3 GPa). Based on the high pressure Raman spectroscopic results, the mode Grüneisen parameters are determined and the average mode Grüneisen parameter of PO₄ vibrations of Sr₃(PO₄)₂ is calculated to be 0.30(2).     

The use of ultrasonic frequencies to control the bloom formation,regrowth, and eco-toxicity in <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis>

This study is focused on the use of ultrasound to disrupt Microcystis aeruginosa growth, with consideration for the gap between laboratory-scale experiment and field application. Laboratory-scale sonication systems with different frequencies (i.e., 20, 584, 869, and 1137 kHz) for 30 min at 10-min intervals were conducted to investigate their effectiveness at disrupting M. aeruginosa growth. The toxicological effect of sonicated M. aeruginosa including microcystin-LR was also evaluated using a Daphnia magna acute toxicity test. High frequencies, 869 and 1137 kHz, resulted in more than a 60% reduction of cells after 30 min of sonication. Low to middle frequencies, 20 and 584 kHz, only showed a 30% reduction of cells after 30 min of sonication. High frequencies also led to the inactivation of cell proliferation during M. aeruginosa regrowth, due to cellular destruction and finally cell death. However, the concentration of microcystin-LR and the potential adverse effects of M. aeruginosa on D. magna could not be controlled using ultrasonic frequencies. Therefore, our results suggest that ultrasonic frequencies between 869 and 1137 kHz are effective at controlling bloom formation in M. aeruginosa and the regrowth of M. aeruginosa after sonication, but not at controlling microcystin-LR concentrations and its adverse effects on D. magna. Consequently, a combined purification technology to reduce the cyanotoxins such as microcystin-LR, rather than ultrasonic frequency alone, will be needed to control M. aeruginosa growth and its toxicity levels in the aquatic environment.