Van Dorn Bottle Research Articles

Analysis of the physico-chemical relationship between losses of water, soil and soil nutrients in the water of the Farinha River – MA

Brazil has a vast reserve of water resources, but pollution from various sources and the effects of climate change have triggered a crisis in this sector. The as-sessment of water quality indices plays a crucial role in monitoring and unders-tanding this issue, and the country has established its own standards and moni-toring requirements to guarantee water quality. In addition, the physical-chemical relationship plays a fundamental role in the conservation of both soil and water. In this context, a study was carried out in the Farinha river basin, located in Maranhão, in the Cerrado biome, over an area of 55,338.12 hecta-res. Data was collected at ten different points along the river during the rainy and dry seasons. A Van Dorn bottle was used to collect water samples at vari-ous depths, which were analysed for pH, dissolved oxygen, electrical conducti-vity and temperature. Nutrients such as potassium, calcium, magnesium, sodi-um, silicon, nitrate and total phosphorus were quantified using filtration and spectroscopy techniques. The data obtained was tabulated and subjected to analysis of variance, with the means analysed using the Tukey test. This study reveals significant seasonal variations in the physico-chemical parameters of the water in the Farinha River in Maranhão, impacting aquatic life and water quality. This highlights the importance of continuous monitoring and manage-ment of these resources.

Algal Blooms and their Importance in Xochimilco and San Gregorio Atlapulco, Mexico

Algal blooms refer to the massive development of photosynthetic microorganisms in aquatic environments. Microalgae are an important source of food for the primary consumers of these ecosystems, purify water, capture atmospheric CO2 and from them a large number of products for industrial use are obtained; however, in Mexico its study is still incipient, especially with regard to blooms of freshwater species. This paper presents the results obtained from the most abundant and important algal blooms of the Ejidos de Xochimilco and San Gregorio Atlapulco Protected Natural Area. 12 samplings were carried out between the years 2012 to 2022. The samples were collected with 54 μm mesh aperture trawl and van Dorn bottle and were fixed with 4% final formalin and 1% lugol, respectively. 17 algal blooms were recorded, among the Cyanoprokaryotes are: Anabaenopsis circularis, Limnospira maxima, Microcystis aeruginosa, Planktothrix agardhii; among the Chlorophytes Monoraphidium convolutum, Ankistrodesmus falcatus, Closterium acutum, Lemmermannia tetrapedia; among the Euglenophytes Euglena viridis y Phacus pleuronectes and between the Diatoms Cocconeis placentula var. placentula, Stephanocyclus meneghinianus, Epithemia turgida var. turgida, Gomphonema olivaceum, Gomphonema parvulum var. capitata, Hantzschia amphioxys y Craticula cuspidata. Of these species, Limnospira maxima has very high nutritional value, Anabaenopsis circularis, Microcystis aeruginosa y Planktothrix agardhii are potentially toxic or carcinogenic. It should be noted that all the registered species presented great spatiotemporal variations, for the above and given their great importance, it is necessary to expand their knowledge and carry out constant monitoring, as a tool for their understanding, use and management.

Using Pollution Index to determine water quality in Banda Aceh waters, Indonesia

The northern waters of Banda Aceh are connected with the Indian Ocean, the Andaman Sea, and the Malacca Strait, thus making the study of water quality parameters in this region is important for enviromental management. In this study, water quality parameters are measured spatially and then continued with assessing the pollution index. The results can be helpful for development planning and coastal pollution mitigation in Banda Aceh. The data was collected from 21 seawater samples from 11 stations representing the water of Banda Aceh on 10-11 September 2019. VanDorn bottles were used to store the seawater samples for laboratory analysis. Several parameters such as temperature, salinity, and pH were measured in situ, while other parameters were tested in the laboratory. Most heavy metal parameters showed values below the minimal and maximal value limit detection of the instrument, indicating a small potential for heavy metal contamination. However, the pollution index (PI) indicates the potential for water pollution dominated by nitrate and phosphate with a value that exceeds the water quality standard. The indications are shown from the high aquaculture and anthropogenic activities around the coast of Banda Aceh.

Spatio-temporal sublittoral macrobenthic distribution and dominant species in Guanabara Bay, Rio de Janeiro, Brazil.

Soft-bottom macrobenthic invertebrates are sensitive to natural or anthropogenic changes in aquatic ecosystems. The distribution patterns of sublittoral macrobenthic species in Guanabara Bay were studied from 2005 to 2007. Samples were collected at ten stations during six surveys throughout the rainfall regime (dry, early and late rainy). Ten replicates were collected at each station by Gravity corer or skin diving. Van Dorn bottles (bottom water) and by Ekman sediment sampler (granulometry) provided material for abiotic data. Stations were grouped into sectors (Entrance, Intermediary and Inner) based on abiotic data and location. The Redundancy Analysis (RDA) and Parsimonious RDA for all years and each annual cycle showed indicator taxa with high dominance in each sector. PERMANOVA indicated a regular seasonality between the surveys for the first annual cycle (p <0.05), and an atypical pattern for the second (p> 0.05), possibly due the low rainfall observed during this period. The mosaic of soft-bottom substrates infers structural variables, and patterns of temporal distribution were basically influenced by parameters those indicating pollution and the SACW (South Atlantic Central Water) intrusion, as well as ecological attributes among species, such as: predation, competition. The Ervilia concentrica and Cypridinidae could be used as indicators for anthropic and natural impacts in the Guanabara Bay for the Entrance sector, while Cyprideis salebrosa and Cyprideis sp. for the Intermediary sector and Heleobia australis for the Inner sector.

Improving estimation of phytoplankton abundance and distribution in ballast water discharges

With the International Maritime Organization’s (IMO) International Convention for the Control and Management of Ships’ Ballast Water and Sediments now in force, determining abundance and distribution of phytoplankton inside ballast tanks is critical for successful ballast water management, particularly when assessing compliance. The relationship between the abundance and distribution of cells was examined to obtain the best representative sample of the entire phytoplankton community in ballast tanks, comparing three ballast water sampling techniques including in-line, in-tank, and Van Dorn bottle methods. Lloyd’s index, Dy, and Gini index were applied to compare methods of sample collection and determine representativeness of samples and performance of sampling methods. Phytoplankton abundance trends from live microscopy counts using fluorescein diacetate (FDA) were also compared to those using a FlowCAM on preserved samples. The phytoplankton community showed a patchy distribution inside the ballast tank and this trend was observed across all voyages. The estimated marginal mean analysis showed that in hypothetical conditions (e.g., 702 m3 of water in ballast tank and phytoplankton whole-tank abundance of 19,522 cells), the difference among the three methods was small. Conversely, statistical analysis performed on empiric abundances using a negative binomial regression model determined that the volume discharged during sampling of ballast water has an effect on the number of cells collected on a given voyage. Results of this study also confirmed that the in-line method may be a better method at collecting phytoplankton samples from ballast tanks than the in-tank or Van Dorn method, regardless of the time at which samples are collected. Finally, the number of living cells and the number of preserved cells showed similar trends for most of the voyages, despite fewer samples analyzed using FDA.

Phytoplankton Dynamics of Mokolo and Mopa Ponds in Bertoua City (East-Cameroon)

This study aims to improve the understanding of algal community’s dynamics in response to different environmental factors in two dam ponds (Mokolo and Mopa) in the city of Bertoua (East-Cameroon). Physicochemical and biological analyzes were carried out monthly by direct sampling at the surface and using Van Dorn bottle at 1 m depth. The organisms were collected using transparent glass vials of about 500 ml and fixed with 2.5 ml of a lugol solution, then analyzed using the Utermohl method. Physicochemical analyzes show low transparency (75 cm) of the ponds despite their shallow depth (≤150 cm), high levels of dissolved oxygen (>60%), BOD5 (>30 mg/L) and chlorophyll “a” (>30 μg/L). These data made it possible to categorize the Mokolo and Mopa ponds as hypereutrophic with nitrogen as the limiting factor for eutrophication. Biological data show quite diversified ponds with 138 species identified in Mokolo Pond and strongly dominated by Diatoms with 2951 ind. representing 46% of the total abundance. In Mopa Pond, 147 species were identified, mainly represented by Chlorophyceae with 3629 ind. representing 52% of the total abundance. Azpeitia africana (Mokolo) and Eresmophaera gigas (Mopa) were the most represented taxa during the study. This study will have deduced that the structure and dynamics of algal communities are under the control of different factors or processes that interact simultaneously, namely ascending factors or bottom-up corresponding to nutrient resources and sunlight and descending factors or top-down that are exerted by grazing and active physiological substances produced by other algae that are known to influence phytoplankton.

Distribuição do Fitoplâncton no Entorno da Reserva Biológica Marinha do Arvoredo

O fitoplâncton constitui um dos principais componentes dos sistemas aquáticos marinhos e sua distribuição é influenciada por vários fatores ambientais, tais como, nutrientes e luz, além de temperatura, turbidez e oxigênio dissolvido. O ambiente marinho da plataforma de Santa Catarina é um sistema subtropical, oligotrófico. Massas de água de origem oceânica modificam as condições oceanográficas da região (ACAS, APP, e aporte continental por PRT e CN) Apesar da importância biológica dessa região, estudos sobre a distribuição e ecologia do fitoplâncton são escassos. Diante disso, o objetivo do presente estudo é avaliar a distribuição do fitoplanctônica no entorno da Reserva Biológica Marinha do Arvoredo, ao longo de três anos consecutivos. O presente estudo é baseado no projeto MAArE. Coletas foram realizadas entre os anos de 2014 a 2016, em seis estações de amostragem e em três profundidades. Parâmetros físicos foram obtidos in situ e químicos coletados em garrafas Van Dorn para análise dos nutrientes inorgânicos em suspensão. Amostras para análise quantitativa do fitoplâncton, coletados em garrafa Van Dorn e acondicionadas em frasco de 250 mL, preservadas em solução de água do mar-formaldeído a 4%. A identificação e contagem dos organismos foi realizada em microscópio ótico invertido Olympus®, modelo CKX41, segundo o método clássico de Utermöhl. Altas densidades celulares foram associadas as altas concentrações de Silicato. Durante o verão, nas estações costeiras, a fertilização por este nutriente está sob influência continental e intrusão da ACAS nas estações mais profundas e no inverno pelo intrusão APP.

Microplastics in oysters (Crassostrea gigas) and water at the Bahía Blanca Estuary (Southwestern Atlantic): An emerging issue of global concern

Detection of microplastics (MPs) in biotic and abiotic matrices is relevant to evaluate how marine ecosystem’s exposure to these pollutants is of emerging environmental concern and at risk of loss of functionality and biodiversity. The presence of MPs was studied for the first time in the gut of benthic oysters (Crassostrea gigas) and in the water column in a eutrophic estuary under high anthropogenic pressure, in the southwestern Atlantic. Significant abundances of small plastic debris were found at all the sampling stations- mainly fibers, fragments, pellets, and beads. MPs were categorized and counted according to type, color, and size. Microfibers presented the highest percentage of abundance in the water column (98% with Van Dorn bottles and 72.73 % with a 60μm plankton net) as well as in oysters (91%). In water collected with Van Dorn bottles, the total MP concentrations ranged from 5900 to 782,000 particles/m3 and from 42.6 to 113.6 particles/m3 in samples collected with a 60μm plankton net. The widespread presence of fibers in all the assessed components could be related to the intense harbor activities in the area, such as the use of ropes for the mooring of boats and from fishing nets, as well as from domestic and industrial effluents. The presence of MPs in both the pelagic and benthic realms may imply risk for the animals that inhabit the estuary, and for human wellbeing, with respect to the potential transfer of MPs through the food web, affecting the provisioning of ecosystem services.

Assessment of heavy metals in the surface sediments and sediment-water interface of Lake Cajititlán, Mexico.

Lake Cajititlán is an endorheic tropical lake located in the state of Jalisco, Mexico, which has suffered the consequences of high levels of eutrophication. This study assessed the presence of heavy metals and metalloids in Lake Cajititlán to ascertain possible risks to its aquatic biota and the environment. Eleven monitoring sites were selected throughout the lake; from each site, one sample was taken from the sediments and another from the sediment-water interface by using an Ekman dredger and a Van Dorn bottle, respectively. The measured metals in each sample were As, Cd, Cr, Hg, Pb, Zn, Cu, Ni, Fe, Mn, and Al. The results showed the following sequence of heavy metal concentrations Al > Fe > Mn > Zn > Cu > Cr, wherein Al had the highest average concentration and Cr had the lowest. As, Cd, Hg, and Pb were practically undetectable. Because the predominant rock in the lake basin is volcanic tuff and the soil is vertisol, the high quantities of Al and Fe suggest the weathering of the basin's minerals. The analyses of the sediment-water samples contained small amounts of dissolved Al, Fe, and Mn. According to the Håkanson equations with Hg, Cd, As, Cu, Pb, Cr, and Zn, the calculations of the contamination degree and ecological risk revealed that the presence of metals and metalloids does not present a potential risk to the aquatic biota; nonetheless, the water is not suitable for local human consumption due to an unrelated factor associated with nutrient and bacteriological contamination. The results show that heavy metals in the sediments were dispersed throughout the lake mostly because of the weathering of minerals from the local basin and not because of the punctual discharges of the pollutants from the municipal wastewater treatment plants (WWTPs). However, to ensure that the small amounts of dissolved metals (Al, Fe, and Mn) do not affect the aquatic biota, the fish species and phytoplankton need to be internally analyzed.

Marine microalgae on the southern coast of Bahia, Brazil: composition and new records of phytoplankton species

Abstract The phytoplankton community is the first link in the aquatic trophic chain and knowledge of its composition is an important tool for ecological characterization; including as potential indicator of anthropic impacts. The southern coast of Bahia is one of the best preserved parts of the Brazilian coast, however, little is known about its biodiversity, especially on marine phycoflora. With the objective of characterizing the composition of microphytoplankton (&gt; 20 µm) in this region, samples were collected by a horizontal dredger using a plankton net (20 µm mesh size) to study the community composition. Water samples were taken from the subsurface using a Van Dorn bottle in order to analyze phytoplanktonic cell concentration. A total of 149 taxa were identified, distributed in the following phyla: Bacillariophyta, Miozoa, Cyanobacteria, Euglenophyta, Haptophyta, and Ochrophyta. Diatoms (63%) and dinoflagellates (26%) were the most representative groups in the specific composition. 43 new taxonomic occurrences were recorded for the coasts of Bahia, Northeastern Brazilian coast, and Brazilian coast.

Estimation of Suspended Sediment Concentration by Using Mobile ADCP Instrument

The measurement of suspended sediment concentration (SSC) by using Acoustic Doppler Current Profiler (ADCP) instrument still not widely used in Indonesia. The application of this technology uses sound wave by four direction transducers placed in the vessel, and this ADCP measured the intensity of backscatter from sediment particles. This study is equipped with RD Instruments WorkHorse Mariner 307.2 kHz ADCP, and the water sample collected from Lembeh Strait, North Sulawesi by using van Dorn bottle sampler. Beyond the experimental purpose of this installation, the interest in having wide area data at different tidal condition is that it provides the possibility of determining the effect of tidal to the SSC. The losses of sound signal were corrected to get more accurate results. Simple linear regression analysis performed to obtain the estimates of the SSC. Estimation of SSC of ADCP measurement was then compared with SSC on water analysis in the laboratory, and the result showed that insignificantly different by statistical analysis. From this research, it showed that the concentration of suspended sediment ranged between 60-73 mg L−1 on location near the Port of Bitung, and 50-62 mg L−1 at a location away from the port. The result also observed that the highest concentration is in the region below the water column, and tidal condition was affected the condition of SSC. Based on all analysis, the mobile ADCP can provide a suitable measurement of suspended sediment concentration.

Seasonal variation of the phytoplankton community in tuna farms in Bahia de La Paz, southern Gulf of California, Mexico

The phytoplankton community of tuna farms in Bahia de La Paz, southern Baja California, Mexico was studied. Samples were taken from tuna farms near San Juan de la Costa, Rancheros del Mar and from a station in El Mogote, away from the influence of these farms. Water samples were collected monthly (June 2006-May 2007) with a van Dorn bottle at different depths in San Juan de la Costa (0, 25 and 50 m), Rancheros del Mar (0, 15 and 30 m) and El Mogote (0 m) to measure temperature, dissolved oxygen, inorganic nutrients, and chlorophyll-a and to determine phytoplankton composition and abundance. The index of simple dominance, Shannon-Weaver diversity, and Pielou evenness were estimated. The water column was stratified from June to September (~27.5°C) and mixed from October to May (~18.5°C). Nutrient concentrations at the three sampling sites did not increase significantly. Nanophytoplankton dominated, followed by microplanktonic diatoms, and the highest diatom abundance occurred during the warm period. The phytoplankton community was more diverse in San Juan de la Costa than in Rancheros del Mar. In the latter, a superficial bloom of the cyanobacterium Trichodesmium erythraeum (1630×103 cel L -1 ) occurred in September, and in San Juan de la Costa the diatom Pseudo-nitzschia fraudulenta reached the highest abundance (183.8×103 cel L -1 ) in July.

Planktonic algal blooms from 2000 to 2015 in Acapulco Bay, Guerrero, Mexico

Background and Aims: Harmful algal blooms (HABs) affect the marine ecosystem in multiple ways. The objective was to document the species that produced blooms in Acapulco Bay over a 15-year period (2000-2015) and analyze the presence of these events with El Niño-Southern Oscillation (ENSO).Methods: Thirty-five collections, made during the years 2000, 2002-2004, 2006-2011, 2013-2015, were undertaken with phytoplankton nets and Van Dorn bottle, yielding 526 samples, of which 423 were quantified using the Utermöhl method. The relationship of HAB with ENSO was made with standardized values of Multivariate ENSO Index (MEI) and the significance was evaluated with the method quadrant sums of Olmstead-Tukey.Key results: Using data of cell density and high relative abundance (&gt;60%), 53 blooms were recorded, most of them occurring during the rainy season (June-October) and dry-cold season (November-March), plus 37 blooms reported by other authors. These 90 blooms were composed of 40 taxa: 21 diatoms and 19 dinoflagellates, the former mostly innocuous. Sixty-seven blooms had species reported as noxious, of which 11 species commonly produce toxic HAB. Toxic taxa are Pseudo-nitzschia spp. (four taxa), and seven dinoflagellates.Conclusions: Abundance analyses of Pyrodinium bahamense var. compressum and Gymnodinium catenatum against values of MEI showed a clear tendency to produce HAB in La Niña conditions. Both taxa, producers of saxitoxins, cause paralytic shellfish poisoning (PSP) and coexist in Acapulco; therefore, they present a risk to human health. Another noxious 52 taxa found in Acapulco were currently considered potential HABs, because they have been recorded at low densities. Given the sharp differences in density values of bloom-forming species found in this work compared to those reported by other authors on similar dates, it is important to perform calibration tests to rule out possible errors in cell counts.

Hidrodinâmica e composição sedimentar do córrego Jacobina, município de Cáceres, MT, Pantanal

Este estudo objetivou avaliar a influência da geologia e do uso e ocupação da terra na composição granulométrica do sedimento da bacia do córrego Jacobina, em Cáceres-MT, Pantanal. Para tanto, a área foi dividida em três compartimentos considerando a geomorfologia local onde, uma coleta de sedimento de fundo e água para análise do sedimento em suspensão foi realizada nos períodos de cheia (Fevereiro/2015) e de seca (Julho/2015). O sedimento de fundo foi coletado através de uma draga do tipo Petersen e a água através de uma garrafa de Van Dorn. Dados relativos à profundidade e largura do canal, velocidade do fluxo da água e altura do barranco também foram mensurados. Os resultados demonstraram que o córrego Jacobina sedimenta partículas de granulometria mais grossa como areia grossa e média no fundo e o material mais fino tende a manter-se em suspensão nas seções 1 e 2. Na seção 3, o material depositado no fundo é de granulometria mais fina como areia fina e silte. Com relação às variáveis hidrodinâmicas a largura e a profundidade do canal diminuíram da estação chuvosa para a estação seca, diminuindo assim a velocidade do fluxo das águas e a vazão. Os dados demonstraram que o tipo e quantidade de sedimentos encontrados nas seções de coleta podem ser influenciados pelo material geológico e o tipo de uso da terra no entorno da bacia.

Hidrodinâmica e transporte de sedimentos na bacia do rio Branco, afluente do rio Paraguai, Pantanal Mato-grossensse

Estudos sobre a hidrodinâmica e o transporte de sedimentos possibilitam compreender como ocorrem as pressões no meio e a relação entre os elementos ambientais. O objetivo da pesquisa foi analisar as variáveis hidrodinâmicas e transporte de sedimentos na bacia hidrográfica do Rio Branco, afluente do Pantanal mato-grossense. Foram selecionadas dezesseis seções para obtenção de informações da hidrodinâmica e do transporte de sedimentos. Com o intuito de obter a batimetria, utilizou-se o ecobatímetro. A verificação da velocidade do fluxo foi realizada com o uso do molinete fluviométrico. A fim de coletar os sedimentos suspensos, usou-se a garrafa de Van Dorn; para os sedimentos de fundo, utilizou-se a draga Van Veen. O fracionamento das amostras de sedimentos de fundo foi realizado através do método da pipeta, com dispersão total e peneiramento. A vazão dos canais variou entre 0,005 e 4,861m³/s no período de estiagem e de 0,11 a 126,42 m³/s no período chuvoso. Os sedimentos transportados em suspensão mantiveram-se entre 12 e 288mg/L-1. A carga sólida em suspensão ficou entre 0,02 e 3.146 t/dia-1. Na composição granulométrica de sedimentos de fundo, predominaram as frações de areia fina. Através desse estudo foi possível observar o comportamento hídrico e a disposição de sedimentos entre os períodos de cheia e estiagem.

Extreme droughts drive tropical semi-arid eutrophic reservoirs towards CO2 sub-saturation

Abstract Aim: This study aimed to evaluate the carbon dioxide (CO2) dynamics in tropical semi-arid reservoirs during a prolonged drought period as well as to test if the trophic state affects the CO2 saturation. Methods This study was performed in four reservoirs located in the tropical semi-arid region in the northeast of Brazil. All samplings were performed between 9 and 12 am using a Van Dorn Bottle. Samples for partial pressure of carbon dioxide (pCO2 ) measurements were taken in the sub-surface as well as samples for total phosphorus and chlorophyll-a. Correlation analysis and linear regression were used to detect relations among the calculated pCO2, water volume and chlorophyll-a. Results The water level reduction due to atypical droughts caused chlorophyll-a concentrations to increase, which in turn, led to CO2 reduction in the water. However, CO2 concentrations were very variable and an alternation between CO2 sub-saturation and super-saturation conditions was observed. This paper showed that water volume and chlorophyll-a were important regulators of CO2 in the water, as well as important carbon balance predictors in the tropical semiarid reservoirs. Conclusions The results of this paper indicate that the eutrophication allied to drastic water level reductions lead to a tendency of autotrophic metabolism of these systems.

Composición del Fitoplancton en el embalse Los Laureles, Francisco Morazán, Honduras

El Embalse Los Laureles es un ecosistema artificial creado para abastecimiento de agua potable. Se estudiaron los parámetros físicos (temperatura, conductividad, turbidez y disco Secchi), químicos (pH, oxígeno disuelto,) y biológicos (clorofila a), con el objetivo de determinar la composición (abundancia y diversidad) del fitoplancton durante marzo-agosto 2014. Se obtuvieron muestras biológicas en tres puntos del embalse que comprenden cortina, centro y cola con 100 mL, utilizando red de arrastre a nivel sub superficial 20 – 30 cm de profundidad durante dos minutos para análisis cualitativo y con botella de Van Dorn a profundidad Secchi para análisis cuantitativo. Los perfiles clinógrados de oxígeno, turbidez elevada en el hipolimnion, baja transparencia de Secchi persistentes en todos los muestreos, 21 taxa identificadas, de las cuales 7 pertenecen a las Cianofíceas, 5 a las Bacillariophyceas y 9 a las Clorofíceas. Durante el tiempo de muestreo, las Cianofíceas se encontraron en un 67 %, las Bacillariophyceas en un 26% y Clorofíceas en un 7%, estos factores indican características de cuerpos de agua eutróficos. Sin embargo, para obtener resultados con mayor grado de confiabilidad, se recomienda realizar los muestreos físicos, químicos, biológicos y de productividad por lo menos cada quince días durante la época seca y lluviosa, aumentando los muestreos cuando se sospecha de floraciones algales, ya que estas relaciones son más precisas cuando los estudios se realizan por ciclos anuales, para identificar patrones de variación y tendencias que ayuden a prevenir y corregir este problema.Revista Portal de la Ciencia, No.11, diciembre 2016, p.90-104

Phytoplankton functional groups in a tropical reservoir in the Brazilian semiarid region

Phytoplankton functional groups structure and species abundance vary according to environmental conditions. The present study investigated the natural and anthropogenic stressors that affect phytoplankton functional group biomass in a Brazilian semiarid region reservoir (Argemiro de Figueiredo reservoir). Sampling occurred between August 2007 and July 2009 on a bi-monthly basis for the first year, and in a monthly basis for the last two years. There were three collection points (PC: river confluence; PNC: near the cages; PD: dam site). The water environment analysis of abiotic variables included: temperature, transparency, coefficient of vertical light attenuation, dissolved oxygen, pH, electrical conductivity, alkalinity, dissolved inorganic nitrogen, and reactive soluble phosphorus. Phytoplankton samples were collected into a Van Dorn bottle, and were then preserved in acetic lugol and were quantified using an inverted microscope to determine phytoplankton density and biomass; the identified species were assembled in functional groups. The data were explored by canonical correspondence analysis. Individual analyses were made to test the temporal and spatial variability of the data and the factors that interfered most with the biotic and abiotic variables. Functional groups S1, SN, and K, consisting of filamentous Planktothrix agardhii (Gomont) Anagnostidis &amp; Komárek, Cylindrospermopsis raciborskii (Woloszynska) Seenaya &amp; Subba Raju, and the coccoid Aphanocapsa incerta (Lemmermann) Cronberg &amp; Komárek, respectively, dominated the dry months when the water was warm, turbid, and alkaline. The overflow reservoir served as a natural disturbance reducing the phytoplankton biomass to less than 50 % and the dominance of cyanobacteria, promoting the domain of functional groups F, M, MP, Lo, and X2. The nutrient inputs from intensive fish farming, associated with a low local depth (Zmax = 7.7 m) close to the cages (PNC), resulted in a significant human disturbance that increased the prevalence of functional groups S1, SN, and K, which are composed primarily of cyanobacteria. We concluded that, in reservoirs, overflow events are natural disturbances that have the ability to reduce phytoplankton biomass and alter the structure of local communities, and that intensive fish farming is an anthropogenic disturbance that increases the availability of nutrients and stimulates an increase in biomass of the functional groups that include cyanobacteria. Furthermore, the functional groups of phytoplankton were reliable control of environmental conditions in the reservoirs of tropical semiarid regions.

Co-occurrence of Cylindrospermopsis raciborskii (Woloszynska) Seenaya &amp; Subba Raju and Microcystis panniformis Komárek et al. in Mundaú reservoir, a semiarid Brazilian ecosystem

Abstract The influence of temperature and nutrients on the co-occurrence of Cylindrospermopsis raciborskii and Microcystis panniformis in Mundaú reservoir was investigated. Samples were collected bimonthly from September 2008 to March 2009 with a Van Dorn bottle at two depths (surface and bottom) (n = 16). Water temperature was greater than 22.50 °C; pH values ranged from 6.09 to 8.42; and nitrogen-phosphorus ratios were low (0.11-1.46). The low N:P ratios indicated high phosphorus input, and an eutrophic to hypereutrophic condition in the reservoir. A significant positive correlation of spatial and temporal distribution of C. raciborskii with M. panniformis was observed. Canonical correlation analysis (CCA) results revealed significant association of the biomass of most cyanobacterial species with temperature and nutrients concentration. However, these factors did not explain the co-occurrence of C. raciborskii and M. panniformis. On the other hand, morphological and physiological adaptations such as the possession of aerotopes and production of mucilage, and co-operation between the two species permitted niche overlap, and consequently the co-occurrence of C. raciborskii and M. panniformis in Mundaú reservoir.

Microalgas del Área Natural Protegida Ejidos de Xochimilco y San Gregorio Atlapulco, México

En México la mayor parte de los escasos los trabajos de las espe­cies microscópicas, pese a que poseen una gran importancia ecológica, económica y propie­daes de interés para el sector salud. En la zona de estudio, Área Natural Protegida Ejidos de Xo­chimilco y San Gregorio Atlapul­co, Ciudad de México, este es­quema se repite, encontrándose pocos trabajos sobre las microal­gas de los canales de Xochimilco y ninguno sobre San Gregorio Atlapulco. El objetivo del pre­sente trabajo fue elaborar un in­ventario de las microalgas de los canales de estas dos áreas. Para el caso de Xochimilco, se hizo una revisión bibliográfica exhaustiva, que abarcó de enero de 1933 a diciembre de 2014. Para el caso de San Gregorio Atlapulco, de­bido a que no había estudios previos, se realizó un muestreo en enero del 2013 en 17 estacio­nes distribuidas en toda la zona, con una red de arrastre de aber­tura de malla de 54 μm y con una botella van Dorn. Las muestras se preservaron con formalina al 4 % y con lugol al 1% respectiva­mente, obteniendo un total de 34 muestras. Se generó un listado de 370 especies de microalgas para toda el Área Natural Protegida, de las cuales, 36 % pertenecieron a Clorofitas; 24 % a Euglenofitas; 24 % a Diatomeas, 12 % a Ciano­procariotas, 3 % a Dinoflagelados y 1 % a Cromofitas, con 27 nuevos registros para San Gregorio Atlapul­co. Entre las especies registradas, Microcystis aeruginosa y Peridinium willei forman florecimientos algales tóxicos, por lo que se hace necesa­rio monitorear estos ecosistemas para prevenir sus efectos noci­vos, además de continuar con los estudios ficoflorísticos de la región. Archivo XML (SciELO)