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The European Water Framework Directive implements the policies to achieve a good ecological status of all European waterbodies. To determine the ecological potential in freshwater environments, abiotic (morphology, physical and chemical variables) and biotics (algae, fishes, etc.) metrics are used. Despite their importance in trophic web, zooplankton was not included as one of the Biological Quality Elements (BQE) to determine the water quality. In the present research, we studied the zooplankton species that can be considered as indicators of trophic status and ecological potential for more than 60 water reservoirs. The data were obtained from more of 300 samples collected during 10 years from reservoirs at Ebro River watershed, which is the largest basin in Spain. According to their physicochemical and biological elements, the trophic status and ecological potential of these reservoirs were established. More than 150 zooplankton species were identified during the study. The results from this research indicate that species that are related with low water quality are: Acanthocyclops americanus, Ceriodaphnia spp., Daphnia cucullata, Daphnia párvula, Diaphanosoma brachyurum, Brachionus angularis, Keratella cochlearis and Phompolyx sulcata. An indicator of moderate quality was Bosmina longirostris, while Daphnia longispina, Ascomorpha ovalis and Ascomorpha saltans were considered as indicators of good water quality. The data obtained suggest that zooplankton species can be used as a valuable tool to determine the water quality status and should be considered, in a near future, as one more of the BQE within the WFD metrics.

In Ant-gardens, ants build nests with organic materials and take specific seeds of some species of epiphytes which germinate. In this mutualistic interaction, a variety of other epiphytes could colonize the nests and develop, but it doesn't happen. We assume that there is chemical allelopathy with epiphytes inhibiting the germination and growth of other species of epiphytes, and with ants cutting off non-mutualistic epiphyte species. To investigate this, we performed chemical and prune tests which determine the composition of the epiphyte species of Ant-Gardens of parabiotic ants, Camponotus femoratus (Fabricius, 1804) and Crematogaster levior Longino, 2003. For the chemical allelopathic test, we administered the extract of the stem and leaves of Peperomia macrostachya (Vahl) A. Dietr. and Codonanthe calcarata (Miq.) Hanst. (the most common species in parabiotic AGs) in different concentrations. For the prune test, we used seedlings of the mutualistic plant Peperomia macrostachya and non-mutualistic plant Cucumis sativus as a control, then we inspected the nests to evaluate the ants pruning the seedlings. In the chemical allelopathy tests, the species Codonanthe calcarata decreased the germination speed indexes in relation to the control (distilled water). On the contrary, the length and weight of the seedlings were positively influenced by epiphyte extract. In the prune test, most of the plants pruned were non-mutualistic. The results of the chemical allelopathy and prune experiments showed that both mutualistic epiphytes and ants play a decisive role in the composition of epiphytes in Ant-Gardens.

The regime of frequent small disturbances, such as the formation of tree‐fall gaps, is an important mechanism maintaining the diversity in tropical forests. Occurring primarily in forest gaps, or in riparian vegetation, ant gardens (hereafter AGs) are mutualistic associations involving several epiphytic plant species and ants. In the Amazon rainforest, a widespread AGs association is assembled by two aggressive species of parabiotic ants (Camponotus femoratus and Crematogaster levior). Working together, these ants aggressively monopolize food resources and attack any intruder on the AGs. Here, we demonstrated the extended protective effect of parabiotic ants on the leaf herbivory of neighboring plants, contrasting plants with and without extrafloral nectaries (hereafter EFNs). We performed the fieldwork in South Amazonia where we found 33 forest gaps, 16 with and 17 without AGs. Independently of the presence of AGs, plants possessing EFNs have less area removed by herbivores and fewer leaves with herbivore marks than those without EFNs. This decrease in herbivory was remarkable on EFN‐plants growing in gaps that also harbor AGs. Additional manipulative experiments confirmed this pattern: The AG‐ants were more efficient than no‐AG ants in removing live termite baits placed on EFN‐plants, but few attacks were observed on plants without EFNs. Thus, AG‐ants can extend their role in defending ant gardens from other plants growing in the same area, particularly those with EFNs. This extension of the mutualism benefits can affect the dynamics of the ecological succession and coevolutionary process in the Amazon forest. Abstract in Portuguese is available with online material

Camponotus femoratus (Fabricius, 1804) and Crematogaster levior Longino, 2003 are Amazonian ants that jointly live in a parabiotic association in arboreal nests that are known as Ant‐Gardens (AGs). Both species are locally abundant and aggressive, which forage on the ground and on the vegetation. We evaluated, with extensive sampling, the effect of Ca. femoratus and Cr. levior on the ground and the understory dwelling of ant assemblages in the southern Amazon using pit‐fall traps, beating‐tray sampling, and baiting. We found that Ca. femoratus and Cr. levior caused a decrease in both the abundance and the species richness of the ground ants, changing the assemblage composition, and causing a nestedness pattern. Yet, AG ants seem to not promote significant changes in the assemblage of ants in the understory, with the exception of canopy openness and region, indicating a spatial resource partitioning. Our results showed that the frequency of these parabiotic AG ant pairs can modify the regional assemblage of the ground‐dwelling ants. As ants are ecological engineers and interact with numerous organisms in tropical habitats, the effect of the parabiotic ants can be extended to other organisms that inhabit the gaps along succession.

Entre as interações mutualísticas envolvendo formigas e plantas, o exemplo mais complexo conhecido chama-se jardins de formigas. Nesta interação, as formigas constroem o ninho na vegetação, plantam sementes de epífitas e as protegem, quando crescem. Em troca, as epífitas controlam a umidade do ninho, oferecem estrutura para o seu crescimento e alimento para as formigas. Neste artigo, contextualizamos e situamos o leitor quanto à interação mutulística denominada de jardins de formigas, compilamos informações disponíveis na literatura e trazemos dados de pesquisas ainda não publicadas, mas em andamento, sobre este assunto.

This study compares the morphological characteristics of the dinoflagellate Ceratium furcoides from three Ebro basin reser¬voirs (Spain) and from six reservoirs at São Paulo state (Brazil) with the aim to identify the distinct morphotypes of Ceratium furcoides in Spain and Brazil. We studied the physical and chemical variables to determine the trophic state of each reservoir. Unlike Ceratium hirundinella, Ceratium furcoides is not a frequent species within the plankton community at Ebro Basin reservoirs, however, this species has been responsible of one monospecific bloom at El Val reservoir. Nevertheless, both Ce-ratium species are considered invasive in South America. Ceratium furcoides has displaced C. hirundinella at São Paulo state reservoirs, reaching high densities, to the extent of forming monospecific blooms. Morphometric analysis was performed by optic and electronic microscopy (DIC and SEM respectively). The analysis shows significant differences in: i) total cell length, ii) horns length and iii) presence or absence of a fourth horn. While the microscopic study allows differentiating morphotypes according to the reservoir typology, a deeper study using molecular genetic techniques on the different populations of C. fur¬coides would allow to know better the relationship between the dinoflagellate dynamics and the reservoirs trophic states.

Farmers in the Brazilian Cerrado are increasing grain production by cultivating second crops during the same crop growing season. The release of PlanetScope (PS) satellite images represents an innovative opportunity to monitor double cropping production. In this study, we analyzed the potential of six PS monthly mosaics from the 2021/2022 crop growing season to discriminate double cropping areas in the municipality of Goiatuba, Goiás State, Brazil. The four multispectral bands of the PS images were converted into normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), green–red normalized difference index (GRNDI), and textural features derived from the gray-level co-occurrence matrix (GLCM). The ten most important combinations of these attributes were used to map double cropping systems and other land use and land cover classes (cultivated pasture, sugarcane, and native vegetation) of the municipality through the Random Forest classifier. Training and validation samples were obtained from field campaigns conducted in October 2021 and April 2022. PS mosaic from February 2022 was the most relevant data. The overall accuracy and Kappa index of the final map were 92.2% and 0.892, respectively, with an accuracy confidence of 81%. This approach can be expanded for mapping and monitoring other agricultural frontiers in the Cerrado biome.

Landscape is an ecological category represented by a complex system formed by interactions between society and nature. Spatial patterns of different land uses present in a landscape reveal past and present processes responsible for its dynamics and organisation. Measuring the complexity of these patterns (in the sense of their spatial heterogeneity) allows us to evaluate the integrity and resilience of these complex environmental systems. Here, we show how landscape metrics based on information entropy can be applied to evaluate the complexity (in the sense of spatial heterogeneity) of patches patterns, as well as their transition zones, present in a Cerrado conservation area and its surroundings, located in south-eastern Brazil. The analysis in this study aimed to elucidate how changes in land use and the consequent fragmentation affect the complexity of the landscape. The scripts CompPlex HeROI and CompPlex Janus were created to allow calculation of information entropy (He), variability (He/Hmax), and López-Ruiz, Mancini, and Calbet (LMC) and Shiner, Davison, and Landsberg (SDL) measures. CompPlex HeROI enabled the calculation of these measures for different regions of interest (ROIs) selected in a satellite image of the study area, followed by comparison of the complexity of their patterns, in addition to enabling the generation of complexity signatures for each ROI. CompPlex Janus made it possible to spatialise the results for these four measures in landscape complexity maps. As expected, both for the complexity patterns evaluated by CompPlex HeROI and the complexity maps generated by CompPlex Janus, the areas with vegetation located in a region of intermediate spatial heterogeneity had lower values for the He and He/Hmax measures and higher values for the LMC and SDL measurements. So, these landscape metrics were able to capture the behaviour of the patterns of different types of land use present in the study area, bringing together uses linked to vegetation with increased canopy coverage and differentiating them from urban areas and transition areas that mix different uses. Thus, the algorithms implemented in these scripts were demonstrated to be robust and capable of measuring the variability in information levels from the landscape, not only in terms of spatial datasets but also spectrally. The automation of measurement calculations, owing to informational entropy provided by these scripts, allows a quick assessment of the complexity of patterns present in a landscape, and thus, generates indicators of landscape integrity and resilience. Made available in DSpace on 2022-03-10T02:04:24Z (GMT). No. of bitstreams: 1 Vicente-Metrics-based-2021.pdf: 5683385 bytes, checksum: 8074bc1ec4d7d71f333451ba168a4c0f (MD5) Previous issue date: 2022

espanolLa laguna costera de la Albufera de Valencia es uno de los mayores lagos oligohalinos de la Peninsula Iberica. Fuertemente contaminada y amenazada por planeamientos de desarrollo urbanistico, fue finalmente protegida como Parque Natural en 1986, con el fin de preservar la cubeta y sus ambientes aledanos, los cuales consisten fundamentalmente en arrozales y un bosque sobre la barra arenosa costera. Los planes de restauracion se centran en recuperar la calidad del agua y la cobertura de macrofitos sumergidos que ocupaban la mayor parte de la laguna en los anos 50. Hasta la publicacion de algunos trabajos recientes, se conocia bien poco de la historia paleoambiental esta zona humeda. Con el fin de mejorar esta falta de conoci-miento, estudiamos la evolucion de la laguna durante el Holoceno mediante analisis sedimentologicos, geoquimicos y de microfosiles (foraminiferos, diatomeas, ostracodos y restos polinicos) de cuatro registros. Dos de ellos fueron obtenidos en la barra arenosa, y otros dos del centro del lago. En combinacion con trabajos anteriores, nuestros nuevos resultados muestran que la laguna permanecio como un ambiente salobre durante la mayor parte de su historia desde 8700 cal BP, con presencia frecuente de taxones dulceacuicolas acompanantes entre los 7000 y 3400 cal BP. A pesar de la incerteza de la cronologia, se observan algunos episodios de reduccion de abundancia de microfosiles acuaticos que parecen corresponderse con los eventos de aridez Bond 5 (8.2 ky BP) y Menorca 7 (7.5-7.2 ky BP), este ultimo coincidiendo con un cambio notable de dominancia de vegetacion arborea a herbacea. El cambio mayor en el sistema acuatico consistio en una transformacion drastica a principios del s. XIX de una laguna salobre a una oligohalina, producida por un control antropogenico de la hidrologia, asociado a la expansion del cultivo del arroz. Mas tarde, entre 1960 y 1970 aproximadamente, el incremento poblacional y los impactos asociados de la agricultura, las aguas residuales y los efluentes industriales provocaron un proceso extraordinario de eutrofi-zacion que conllevaria una fuerte reduccion de la vegetacion sumergida y las comunidades de invertebrados, promoviendo la dominancia del fitoplancton de un sistema que paso a un estado de alta turbidez. Aunque nuestro estudio con multiples indica-dores haya aumentado nuestro conocimiento de la historia de la laguna, con la ayuda de evidencias documentales, un mayor esfuerzo de investigacion paleoecologica en diferentes zonas del humedal ayudaria a definir las causas de una dinamica temporal heterogenea en este extenso y complejo humedal. A pesar de esta necesidad de nuevas investigaciones, actualmente existe una prioridad para los gestores y la sociedad, de trabajar en esfuerzos de restauracion que lleven a la zona humeda de a Albufera hacia uno de los estados previos menos impactados de este ecosistema ampliamente sobreexplotado y desatendido EnglishThe Albufera de Valencia coastal lagoon is one of the largest oligohaline lagoons in the Iberian Peninsula. Highly polluted and threatened by plans for urban development, it has been protected as a Natural Park since 1986 to preserve its environment and surroundings, mostly consisting of ricefields and a forested coastal sand bar. Restoration plans focus on recovering the water quality and submerged macrophyte cover that occupied most of the lagoon in the 1950’s. Until recent studies, little was known about the wetland’s palaeoenvironmental history. To improve this knowledge, we analysed the Holocene evolution of the lagoon based on sedimentology, geochemistry and microfossils (foraminifera, diatoms, ostracods and pollen remains) from four cores. Two were collected in the sand bar, and two from the central lagoon. In combination with previous work, our new data show that the lagoon remained brackish for most of its history since 8700 cal BP, with the frequent presence of accompanying freshwater taxa from 7000 to 3400 cal BP. Notwithstanding chronological uncertainties, some episodes of decline in the abundance of microfossils seem to match aridity events Bond 5 (8.2 ky BP) and Minorca 7 (7.5-7.2 ky BP), the latter marking the switch from a dominance of arboreal vegetation to grasses. The most important change in the water body consisted of a sharp change at the beginning of the 19th century from a brackish to an oligohaline lagoon, driven by anthropogenic hydrological control associated with the expansion of ricefields. Later on, by the 1960-1970’s, the growing population impacts of agricultural, wastewater and industrial effluents launched a major eutrophication process that would eventually sharply reduce the benthic vegetation and invertebrate communities and promote the phytoplankton dominance of the ecosystem in a turbid state. Although our multiproxy study has increased understanding of the lagoon’s history, somewhat supported by documentary evidence, further palaeoecological research in different parts of the wetland would help define the causes of heterogeneous timing of changes in this large, shallow, complex system. Notwithstanding the need for further research, there is a clear priority for managers and the society to work on restoration efforts to drive the Albufera wetland towards one of the previous, less impacted, states of this worn-out and neglected ecosystem.

espanolBrachionus havanaensis se distribuye predominantemente en las regiones Neartica y Neotropical. Ahora se encuentra incluso en las regiones Paleartica y Oriental. Durante el verano de 2015, encontramos altas densidades (> 500 ind./l) de esta especie y bajas abundancias de Brachionus angularis en la laguna de la Albufera, donde la cianobacteria (Microcystis aeruginosa) fue dominante en la comunidad de fitoplancton. Nuestra hipotesis fue que la cianobacteria era toxica para B. angularis pero no para B. havanaensis, por lo que este ultimo superaria al primero en presencia de dicha cianobacteria. Para probar la hipotesis, realizamos experimentos de competencia entre estas dos especies de rotiferos (B. angularis y B. havanaensis) que coexisten en la laguna de la Albufera de Valencia utilizando como alimento el alga verde (Nannochloropsis oculata) y colonias sonicadas de M. aeruginosa (celulas individuales) por separado y juntas (en relacion 1:1 basada en biomasa). Los experimentos de competencia basados en el seguimiento del crecimiento poblacional mostraron que en los controles B. havanaensis conseguia un mayor crecimiento poblacional que B. angularis cuando lo hacian separadamente. Sin embargo, cultivandolos ambos juntos, B. havanaensis tuvo una reduccion del crecimiento poblacional (casi 50 %), con respecto a B. angularis, en ausencia de Microcystis en la dieta. Esta reduccion del crecimiento fue mayor que en el tratamiento de B. havanaensis individualmente, cuando se cultivo con una dieta mixta de Microcystis y Nannochloropsis oculata. Brachionus havanaensis en todos los tratamientos (solos o en presencia de B. angularis) murio completamente cuando se cultivo en 100 % de M. aeruginosa. Las tasas de crecimiento poblacional de B. angularis, solos o en competencia con B. havanaensis, fueron similares cuando se excluyo a Microcystis de la dieta. Sin embargo, el cultivo solo con Microcystis o junto con Nannochloropsis fue altamente perjudicial para el crecimiento poblacional de B. angularis. Nuestros resultados mostraron el diferente resultado de los experimentos de competencia entre estos dos rotiferos en funcion de la presencia o ausencia de cianobacterias toxicas en la dieta. Nuestro estudio tambien mostro que una dieta exclusiva de esta cianobacteria era toxica para ambas especies de rotiferos EnglishBrachionus havanaensis is predominantly distributed in the Nearctic and Neotropical regions. It is now found even in the Palearctic and Oriental regions. During the summer of 2015 we found high densities (> 500 ind./l) of this species and low numbers of Brachionus angularis in Lake Albufera where the cyanobacterium (Microcystis aeruginosa) was dominant in the phytoplankton community. We hypothesized that the cyanobacterium was toxic to B. angularis but not to B. havanaensis hence the latter would outcompete the former in the presence of this cyanobacterium. To test the hypothesis, we conducted competition experiments between two coexisting rotifer species (B. angularis and B. havanaensis) from the Lake Albufera of Valencia using as food the green alga (Nannochloropsis oculata) and sonicated colonies of M. aeruginosa (single cells), separately and together (1:1 ratio based on biomass). The competition experiments using the population growth approach showed that B. havanaensis in controls had higher population abundances than B. angularis. However, when grown both together, B. havanaensis had a reduced population growth (nearly 50 %) in relation to B. angularis, in the absence of Microcystis in the diet. This reduced growth was more than that in the treatment of B. havanaensis alone when grown on a mixed diet of Microcystis and Nannochloropsis oculata. Brachionus havanaensis in all treatments (alone or in the presence of B. angularis) died completely when cultured on 100 % M. aeruginosa. The population growth rates of B. angularis, alone or in competition with B. havanaensis, were similar when Microcystis was excluded from the diet. However, Microcystis alone or together with Nannochloropsis was highly detrimental for the population growth of B. angularis. Our results showed the differences in the competitive outcome between the rotifers depending on the presence or absence of toxic cyanobacteria in the diet. Our study also showed that an exclusive diet of this cyanobacterium was toxic to both rotifers.

Ants, an ecologically successful and numerically dominant group of animals, play key ecological roles as soil engineers, predators, nutrient recyclers, and regulators of plant growth and reproduction in most terrestrial ecosystems. Further, ants are widely used as bioindicators of the ecological impact of land use. We gathered information of ant species in the Atlantic Forest of South America. The ATLANTIC ANTS data set-which is part of the ATLANTIC SERIES data papers-is a compilation of ant records from collections (18,713 records), unpublished data (29,651 records), and published sources (106,910 records; 1059 references), including papers, theses, dissertations, and book chapters published from 1886 to 2020. In total, the data set contains 153,818 ant records from 7,636 study locations in the Atlantic Forest, representing 10 subfamilies, 99 genera, 1,114 ant species identified with updated taxonomic certainty, and 2,235 morphospecies codes. Our data set reflects the heterogeneity in ant records, which include ants sampled at the beginning of the taxonomic history of myrmecology (the nineteenth and twentieth centuries) and more recent ant surveys designed to address specific questions in ecology and biology. The data set can be used by researchers to develop strategies to deal with different macroecological and regional-wide questions, focusing on assemblages, species occurrences and distribution patterns. Furthermore, the data can be used to assess the consequences of changes in land use in the Atlantic Forest on different ecological processes. No copyright restrictions apply to the use of this data set, but we request that authors cite this data paper when using these data in publications or teaching events.

Mar Menor is a Mediterranean Coastal lagoon with high environmental and social value, but has suffered important episodes of contamination in recent years due to heavy rains, sediment dragging and polluting substances mainly from agriculture as well as the entry of mining waste, causing an increase in eutrophication. Water quality variables such as chlorophyll-a concentration [Chl-a] and turbidity, can be studied through its optical properties by remote sensing techniques. In this work, a methodology is proposed for monitoring [Chl-a] and the turbidity of the Mar Menor using Sentinel-2 images. For this purpose, an extensive database of both variables was used consisting of data taken on different dates between 2016 and 2019 at 12 points of Mar Menor. The images were atmospherically corrected using Case 2 Regional Coast Color Processor (C2RCC) version for turbid waters (C2X) to obtain the water surface reflectance. Then several arithmetic relations between database and reflectance bands used in the bibliography for [Chl-a] and turbidity were analyzed. Comparing the results of each one of these relations with the in situ data, decided that the best index for [Chl-a] estimation is the relation (R560 + R705)/ (R560 + R665) with an RMSE = 2.6 mg/m3 and a NRMSE = 9.1 % and for turbidity R705*R705/R490 with an RMSE = 1.5 NTU and a NRMSE= 10.9 %. Finally, by applying these relationships on different dates, thematic maps of [Chl-a] and turbidity of Mar Menor were obtained. One of these images was some days after September 2019 torrential rains, in which a considerable [Chl-a] and turbidity increase was observed

Ants inhabit and exploit the most varied habitats from the underground to the forest canopy. However, studies on the diversity of arboreal ants are less frequent in the Amazon. In this paper we list arboreal ant species sampled in understory along four transects in a forest remnant in a South Amazonian landscape. The list includes 32 species, of which three (9 %) are new records for the state of Mato Grosso, Brazil, one of these species being sampled for the first time in Brazil. Las hormigas habitan y explotan los hábitats más variados desde el subsuelo hasta el dosel del bosque. Sin embargo, los estudios sobre la diversidad de hormigas de la vegetación son menos frecuentes en el Amazonas. En este artículo enumeramos las especies de hormigas recogidas en el sotobosque de un remanente de bosque en un paisaje del sur de la Amazonia. La lista incluye 32 especies, de las cuales tres (9 %) son nuevos registros para el estado de Mato Grosso, Brasil, siendo una de estas especies muestreadas por primera vez en Brasil.

The Phytoplankton Reservoir Trophic Index (PRTI), based on the relative abundance of phytoplankton in reservoirs, was applied to 62 reservoirs, all in the territorial division of the Ebro River Basin, Spain. We compared the results of the PRTI to the Carlson Trophic State Index (TSI), based on the concentration of chlorophyll a in an integrated water sample through the photic depth. The PRTI allows assessment of the trophic status of different reservoirs based on phytoplankton densities from an aliquot of a vertically integrated sample. The occurrence of each phytoplankton species in relation to eutrophication was derived from a canonical correspondence analysis between the phytoplankton species and 8 physicochemical variables. The PRTI is used in this study to classify reservoirs into 5 ecological status categories according to the European Water Framework Directive. This methodology has been applied annually from 2006 to 2017 for ecological quality assessments of reservoirs in Spain. The PRTI seems to be a valid index to determine the trophic status of reservoirs and extends information beyond that reported in the TSI.

Strumigenys fairchildi Brown, 1961 is recorded for the first time in Brazil. This ant species was previously known only from a few specimens collected in Costa Rica, Panama and Ecuador. The worker S. fairchildi was collected at the Parque Estadual do Cristalino, a continuous area of Amazon tropical rain forest protected for biodiversity conservation in the municipality of Novo Mundo, Mato Grosso state. In addition, we present a distribution map and high-resolution images of the worker. © 2016 Check List and Authors.

In shallow hypertrophic lakes where light availability restricts the growth of macrophytes and benthic phytoplankton, pelagic phytoplankton modulates importantly ecosystem production and the energy transfer to heterotrophic bacteria. Diel and seasonal variations in primary production (PP) were studied in the hypertrophic Albufera de Valencia (Spain). Additionally, the relationship between PP and heterotrophic bacterial production (BP) was assessed. PP was extremely high, exceeding most values reported for hypertrophic lakes to date. PP displayed marked diurnal variations defined by the solar radiation curve. Likewise, PP changed importantly across seasons. Minimum PP coincided with maximum water transparency and short water residence times in winter, whereas maximum PP was observed in late spring associated with high chlorophyll a. The spring PP maximum contrasted with the summer maximum often observed in hypertrophic lakes. When compared to spring PP values, summer PP values were lower as a result of strong nitrogen limitation. In contrast to PP, BP remained fairly constant across seasons. Nonetheless, there was a joint diminution during increased water transparency followed by an increase in early spring. Phytoplankton was always the most relevant input to particulate carbon production, but the BP/PP ratio showed clear seasonal variations. The BP/PP ratio was minimum in spring, low in summer and highest in winter. The extracellular dissolved organic carbon released by phytoplankton was sufficient to meet bacterial carbon demand in all experimental dates, suggesting that allochthonous carbon sources play a minor role in sustaining BP, though they cannot be excluded. However, we hypothesize that high availability of dissolved organic carbon might explain the lack of coupling observed between BP and PP.

Although several studies have shown that ants can recognize chemical cues from their host plants in ant-plant systems, it is poorly demonstrated in ant gardens (AGs). In this interaction, ant species constantly interact with various epiphyte species. Therefore, it is possible to expect a convergence of chemical signals released by plants that could be acting to ensure that ants are able to recognize and defend epiphyte species frequently associated with AGs. In this study, it was hypothesized that ants recognize and differentiate among chemical stimuli released by AG epiphytes and non-AG epiphytes. We experimentally simulated leaf herbivore damage on three epiphyte species restricted to AGs and a locally abundant understory herb, Piper hispidum, in order to quantify the number of recruited Camponotus femoratus (Fabricius) defenders. When exposed to the AG epiphytes Peperomia macrostachya and Codonanthe uleana leaves, it was observed that the recruitment of C. femoratus workers was, on average, respectively 556% and 246% higher than control. However, the number of ants recruited by the AG epiphyte Markea longiflora or by the non-AG plant did not differ from paper pieces. This indicated that ants could discern between chemicals released by different plants, suggesting that ants can select better plants. These results can be explained by evolutionary process acting on both ants' capability in discerning plants' chemical compounds (innate attraction) or by ants' learning based on the epiphyte frequency in AGs (individual experience). To disentangle an innate behavior, a product of classical coevolutionary process, from an ant's learned behavior, is a complicated but important subject to understand in the evolution of ant-plant mutualisms.

Lakes represent a considerable natural source of methane to the atmosphere compared to their small global surface area. Methanotrophs in sediments and in the water column largely control methane fluxes from these systems, yet the diversity, electron accepting capacity, and nutrient requirements of these microorganisms have only been partially identified. Here, we investigated the role of electron acceptors alternative to oxygen and sulfate in microbial methane oxidation at the oxycline and in anoxic waters of the ferruginous meromictic Lake La Cruz, Spain. Active methane turnover in a zone extending well below the oxycline was evidenced by stable carbon isotope-based rate measurements. We observed a strong methane oxidation potential throughout the anoxic water column, which did not vary substantially from that at the oxic/anoxic interface. Both in the redox-transition and anoxic zones, only aerobic methane-oxidizing bacteria (MOB) were detected by fluorescence in situ hybridization and sequencing techniques, suggesting a close coupling of cryptic photosynthetic oxygen production and aerobic methane turnover. Additions of nitrate, nitrite and to a lesser degree iron and manganese oxides also stimulated bacterial methane consumption. We could not confirm a direct link between the reduction of these compounds and methane oxidation and we cannot exclude the contribution of unknown anaerobic methanotrophs. Nevertheless, our findings from Lake La Cruz support recent laboratory evidence that aerobic methanotrophs may be able to utilize alternative terminal electron acceptors under oxygen limitation. ISSN:1664-302X

The Brazilian Cerrado is a vegetation mosaic composed of different physiognomies. Discussions remain open regarding the factors and processes responsible for the dynamic and spatial organization of the Cerrado - in its different physiognomies. The contributions of the complexity paradigm in this context are still less exploited, despite its great potential for explanations and predictions presented in previous diverse dynamic systems of complex behavior researches, a category in which the Cerrado can be included. This article has the intention of contributing to the construction of this new perspective, discussing - from theoretical concepts - the paradigm of complexity for the understanding of the organization and the dynamics of the Cerrado.

In this study we present a new record of a plant-animal interaction: the mutualistic relationship between the specialist plant-ant Myrcidris epicharis Ward, 1990 (Pseudomyrmecinae) and its myrmecophyte host Myrcia madida McVaugh (Myrtaceae). We observed more than 50 individuals of M. madida occupied by M. epicharis in islands and margins of the Juruena River, in Cotriguaçu, Mato Grosso, Brazil (Meridional Amazon). We discuss a possible distribution of this symbiotic interaction throughout all the riparian forest of the Amazon River basin and its consequence to coevolution of the system.

Hydroclimatic variability is expected to be affected by global warming in the Mediterranean region where climate, fire and human activities are known to be interdependent. The latter is examined here for the past millennium by studying paleoenvironmental indicators from a sedimentary sequence at Lagunillo del Tejo (Cuenca, central Spain). Inferred changes in fire activity and lake levels are based on records of macrocharcoals and plant/algal macrofossils, respectively, and are compared with independent information on climate change and socio-economical transformations from historical and meteorological records. The results show that there is an obvious climatic forcing behind the lake-level changes recorded at Lagunillo del Tejo, and a good correlation between the periods of high fire activity/frequent fires and low lake level/drought conditions. The reconstructed fire regime may therefore be natural (climate-induced), but can also be explained by important socio-economical events/changes, including wars and the introduction of the Transhumance practices (ad 1273). There is a good chronological agreement between lowest fire activity and high lake levels ( c. ad 1600–1800), concurrent with the late ‘Little Ice Age’ (LIA) and the collapse of the Transhumance system. We propose that periods of drought favored both natural and human-induced fires during the ‘Medieval Climatic Anomaly’ (around ad 1200), at the start of the LIA (around ad 1400), in the middle of the LIA (sixteenth century) and during the entire nineteenth century. This record is an example of long-term interplay between climate changes and human activities and its impact on environmental changes such as fire regimes.

The anthropogenic impact on wetlands has increased during the last centuries when infrastructures such as canals or dams, have proliferated. In this article, we have used cladoceran sub-fossils to investigate the effects of a canal on lake El Tobar (Spain). The canal has been transferring water from a reservoir, built in another valley, into this lake since its construction in the mid-1960s. Cladoceran remains were analyzed in two sediment profiles from each of the two sub-basins of the lake. The sedimentary sequences showed that the mentioned human activity provoked a clear shift in the cladoceran community. A PCA was performed with samples from both sub-basins to detect the direction and nature of the changes. Before water transference, the phytophilous chydorid community, represented by Acroperus angustatus in one sub-basin and by both A. angustatus and Graptoleberis testudinaria in the other sub-basin, were well developed. After the construction of the canal and the inflow of additional yet different water from the reservoir, the proportion of chydorids relative to total cladoceran diminished considerably; this was mainly due to the invasion of Bosmina longirostris. These results indicate that the hydrological alteration caused a shift from an oligotrophic, shallower lake with a rich plant-associated cladoceran community to a more eutrophic lake with a predominant planktonic cladoceran community; and that cladoceran remains are a powerful tool to detect hydrological changes and eutrophication.

The state of Mato Grosso is the 3rd largest Brazilian state, is covered with three major Brazilian biomes, including the Pantanal, Cerrado, and Amazonia. To date, 449 ant species are recorded in literature for the state. In the present work, we documented the ants sampled along a fragmented landscape, in the municipality of Juara, in the Cerrado-Amazon transition zone in the state of Mato Grosso, Brazil. The ant species were captured with Pitfall traps installed in 20 trails with 10 traps in each (totaling 200). Our results show 151 species, belonging to 43 genera and eight subfamilies, of which 28 species were recorded for the first time in the state and five species recorded for the first time in Brazil. Most genera collected were Pheidole Westwood, 1839 (45 species) followed by Crematogaster Lund, 1831 (11 species). By highlighting species recorded for the first time in state of Mato Grosso and Brazil, we hope to encourage new discoveries and increase the general knowledge of the ant fauna of different biomes in the region.

Lagunillo del Tejo is a small groundwater-fed sinkhole lake in the karst region of the Iberian Range (central-eastern Spain), which undergoes significant lake level fluctuation in response to rainfall variability. The aim of this study is to understand the record of water level fluctuations in Lagunillo del Tejo over the last two-and-a-half centuries. This information could be used in future studies to interpret longer sedimentary sequences. We analysed photosynthetic pigments, diatoms and cladoceran remains in sediment sequences recovered from the deepest part of the lake. The paleoecological proxies traced two different communities which have switched their prevalence during the past: (1) a planktonic community of algae, including diatoms, chlorophytes, cryptophytes and cyanobacteria, and phototrophic bacteria associated with higher lake level and water column seasonal stratification; (2) a littoral community with the higher levels of macrophyte pigments and associated epiphytic diatoms and chydorids, all of which indicate lower lake level. The levels of coherence between different proxies, each having an independent mechanistic link to lake-level variability, enhance the reliability of palaeolimnological inferences. The high-resolution stratigraphical data from the upper part of the core was compared with lake-level inferences from instrumental rainfall series (1859–2005) to establish the correspondence between Lagunillo del Tejo sediment sequences and climate record.

Two Cyclotella species were found during the electron microscopic investigation of core samples from Lake La Cruz. Cyclotella distinguenda Hustedt was subdominant in the layers 80-110 cms and C. delicatula Hustedt was frequent and abundant in the layers 20-180 cms. SEM studies revealed an interesting variation in their valve structure elements. Analyses of the morphological characteristics of these species on the basis of SEM micrographs (55 photos were taken from C. distinguenda and 95 from C. delicatula) was made it possible to complete their description. In this paper, the similarities and differences between Cyclotella distinguenda, C. delicatula and related taxa (Cyclotella azigzensis Flower, Gasse et Hakansson, C. costei Druart et Straub, C. cyclopuncta Hakansson et Carter, C. granulata Kulumbaeva et Genkal, C. plitvicensis Hustedt, C. wuethrichiana Druart et Straub) are discussed.

A mesocosm experiment was conducted “in situ” in a Chara dominated shallow lake near Valencia (Spain) to study top–down and bottom–up effects on rotifers by means of nutrient and fish additions. Both processes were important in determining rotifer abundance, biomass and diversity. A total of 36 mesocoms were established with triplicate treatment combinations of three fish levels (from no fish to 45 individuals of Gambusia holbrooki males) and four nutrient enrichment levels (from no additions to 10 mg l−1 nitrate-N and 1 mg l−1 phosphate-P). The main effect was a notable increase of planktonic and plant associated rotifers densities with fish. Rotifers benefited from mosquitofish predation on microcrustaceans and chironomids. The results showed a marked negative relationship between rotifer and cyclopoid abundances, indicating the importance of the predatory pressure of cyclopoids on rotifers. Effects on rotifer diversity were also evident, in general rotifer diversity decreased with nutrients and increased with fish. The effects of nutrients analysed at species level showed two contrasting density responses: an increase or a decrease with nutrients, which levelled off at high nutrient concentrations. High-level nutrient additions (from 5 mg l−1 nitrate-N and 0.5 mg l−1 phosphate-P) induced a switch to a turbid state with macrophyte disappearance. Most planktonic rotifer species, as well as plant associated ones, diminished when the turbid state was well established, especially in the mesocosms without fish. In the turbid mesocosms, relative abundance of plant-associated rotifers (as a whole) was higher than that of planktonic rotifers. The changes in rotifer species composition after the switch from a clear to a turbid water state are also described. Species of the genus Anuraeopsis, Trichocerca and Hexarthra, dominant in the clear water state, practically disappeared in the turbid water state, in which Proalides tentaculatus and Lecane nana were the main species.

Gnamptogenys vriesi Brandao & Lattke is a rare ant originally described based on a worker and on a gyne collected in Morona Santiago province, in Ecuador. After the original description, few specimens of this species were collected in Ecuadorian territory. In this paper we reported the first record for Brazil, which resulted in a significant extension on the knowledge of the distribution of this species, which was currently considered to be restricted to Ecuador. In addition, we also provided images and a distribution map for this species.

Summary 1. In view of the paucity of data on the response of warm shallow lakes to reductions in nutrient loading, this paper presents a long-term limnological data set to document changes in the food-web of a shallow Mediterranean lake (Lake Albufera, Valencia, Spain) that has experienced reductions in phosphorus (P) (77%) and nitrogen (N) (24%) loading following sewage diversion. 2. Nine years after sewage diversion, P concentration in the lake was reduced by 30% but remained high (TP = 0.34 mg L−1), although the mean water retention time in the lake was only 0.1 years. Nitrate concentrations did not significantly change, probably because the lake continued to receive untreated effluents from ricefields. 3. Chlorophyll a concentration was reduced by half (annual mean of 180 μg L−1). Cyanobacteria abundance remained high but its composition changed towards smaller species, both filamentous and chroococcal forms. 4. Cladocera abundance increased and reached peaks twice a year (December to March and July to September). After nutrient reduction, short-term clear-water phases (up to 5 weeks) occurred during February to March in several years, concomitant with annual flushing of the lake and lower fish densities. The abundance of Cladocera in winter contrasted with the spring peaks observed in northern restored shallow lakes. The zooplankton to phytoplankton biomass ratio remained lower than in northern temperate shallow lakes, probably because of fish predation on zooplankton. 5. Improvement of the water quality of Lake Albufera remained insufficient to counteract littoral reed regression or improve underwater light allowing submerged plants re-colonise the lake. 6. Sewage diversion from Lake Albufera impacted the food web through the plankton, but higher trophic levels, such as fish and waterfowl, were affected to a lesser degree. Although the fish species present in the lake are mainly omnivorous, long-term data on commercial fish captures indicated that fish communities changed in response to nutrient level and trophic structure as has been observed in restored shallow lakes at northern latitudes. 7. Phosphorus concentrations produced similar phytoplankton biomass in Lake Albufera as in more northern shallow lakes with abundant planktivorous fish and small zooplankton. However, in Lake Albufera, high average concentrations were maintained throughout the year. Overall, results suggest that nutrient control may be a greater priority in eutrophicated warm shallow lakes than in similar lakes at higher latitudes.

Summary 1. Nutrient and fish manipulations in mesocosms were carried out on food-web interactions in a Mediterranean shallow lake in south-east Spain. Nutrients controlled biomass of phytoplankton and periphyton, while zooplankton, regulated by planktivorous fish, influenced the relative percentages of the dominant phytoplankton species. 2. Phytoplankton species diversity decreased with increasing nutrient concentration and planktivorous fish density. Cyanobacteria grew well in both turbid and clear-water states. 3. Planktivorous fish increased concentrations of soluble reactive phosphorus (SRP). Larger zooplankters (mostly Ceriodaphnia and copepods) were significantly reduced when fish were present, whereas rotifers increased, after fish removal of cyclopoid predators and other filter feeders (cladocerans, nauplii). The greatest biomass and diversity of zooplankton was found at intermediate nutrient levels, in mesocosms without fish and in the presence of macrophytes. 4. Water level decrease improved underwater light conditions and favoured macrophyte persistence. Submerged macrophytes (Chara spp.) outcompeted algae up to an experimental nutrient loading equivalent to added concentrations of 0.06 mg L−1 PO4-P and 0.6 mg L−1 NO3-N, above which an exponential increase in periphyton biomass and algal turbidity caused characean biomass to decline. 5. Declining water levels during summer favoured plant-associated rotifer species and chroococcal cyanobacteria. High densities of chroococcal cyanobacteria were related to intermediate nutrient enrichment and the presence of small zooplankton taxa, while filamentous cyanobacteria were relatively more abundant in fishless mesocosms, in which Crustacea were more abundant, and favoured by dim underwater light. 6. Benthic macroinvertebrates increased significantly at intermediate nutrient levels but there was no relationship with planktivorous fish density. 7. The thresholds of nutrient loading and in-lake P required to avoid a turbid state and maintain submerged macrophytes were lower than those reported from temperate shallow lakes. Mediterranean shallow lakes may remain turbid with little control of zooplankton on algal biomass, as observed in tropical and subtropical lakes. Nutrient loading control and macrophyte conservation appear to be especially important in these systems to maintain high water quality.

1. The impacts of nutrients (phosphorus and nitrogen) and planktivorous fish on phytoplankton composition and biomass were studied in six shallow, macrophyte-dominated lakes across Europe using mesocosm experiments. 2. Phytoplankton biomass was more influenced by nutrients than by densities of planktivorous fish. Nutrient addition resulted in increased algal biomass at all locations. In some experiments, a decrease was noted at the highest nutrient loadings, corresponding to added concentrations of 1 mg L1 P and 10 mg L1 N. 3. Chlorophyll a was a more precise parameter to quantify phytoplankton biomass than algal biovolume, with lower within-treatment variability. 4. Higher densities of planktivorous fish shifted phytoplankton composition toward smaller algae (GALD

The abundance, vertical distribution and temporal development of picocyanobacterial (Pcy) populations in the meromictic Lake La Cruz (Cuenca, Spain) was studied in the context of the physical, chemical, and biological characteristics of the lake. Pcy developed dense populations through the oxic waters in spring, but a strong decrease in Pcy abundance in the epilimnion occurred in late spring and early summer linked to nitrogen exhaustion in epilimnetic waters. The highest abundance (up to 7 x 10 6 cells per ml) was found in summer in the bottom part of the thermocline. This abundance is among the highest reported so far for oligotrophic and mesotrophic lakes. The higher phycoerythrin content in deep Pcy cells allows these cyanobacteria to efficiently harvest the predominant yellow-green light available in the metalimnion, where nutrient availability during stratification is higher than in the epilimnion. Sinking losses were important for the Pcy population of Lake La Cruz in mid-summer, when Pcy settling strongly increased linked to a whiting event caused by calcium carbonate precipitation. although Pcy settling was much lower during the rest of the year.

In a limnological survey including 45 lakes and ponds from central-eastern Spain, we studied the main factors associated with the abundance of autotrophic pico-plankton (APP), mostly formed by unicellular picocyanobacteria (APP-Pcy). The study covers a wide range of trophic conditions, salinity, water flow regimes and lake typologies. Phycoerythrin (PE)-rich picocyanobacteria (PE-APP) were abundant in the metalimnion and upper hypolimnion of deep stratified lakes, exhibiting low nutrient availability in the epilimnion. Among these lakes, higher PE-APP abundances were found in lakes with higher retention time during periods of stability, whereas lakes with low retention time lacked conspicuous Pcy populations. They usually formed deep chlorophyll maxima in the nutrient-richer metalimnetic layers, especially when epilimnetic nutrient exhaustion occurred during stratification. The ratios of PE with respect to other photosynthetic pigments in deep lakes usually increased with depth. In these lakes, the available light is selectively enriched in the yellow-green range as depth increases, and these wavelengths can be selectively harvested by PE. Phycocyanin (PC)-rich APP without PE, mostly unicellular rod-shaped cyanobacteria, were only abundant in some hypertrophic shallow lakes, although in many lakes with highly eutrophic conditions their presence was very low or undetectable.

An in vitro nutrient addition bioassay was performed to test the relative inorganic nitrogen (N) and phosphorus (P) limitation of phytoplankton in a Spanish karst lake (El Tejo) during the last part of the stratification period, when nutrient limitation is most pronounced. Nutrient deficiency was tested in samples from three different layers of the lake: the epilimnion, metalimnion and oxic hypolimnion. Nitrogen additions, either without or combined with P, increased phytoplankton growth in all three strata, compared with controls or P treatments. This showed that N was the nutrient limiting phytoplankton growth in late summer-early fall. Since both hypolimnetic diffusion and groundwater fluxes of N-rich waters into the lake are much reduced during summer, N becomes the limiting nutrient as stratification advances. We suggest that in this Mediterranean area with low atmospheric deposition of anthropogenic N and in lakes relatively free of surface run-off, nutrient supply by atmospheric deposition might be a key factor in controlling nutrient deficiency for phytoplankton growth.

1. The European Water Framework Directive requires the determination of ecological status in European fresh and saline waters. This is to be through the establishment of a typology of surface water bodies, the determination of reference (high status) conditions in each element (ecotype) of the typology and of lower grades of status (good, moderate, poor and bad) for each ecotype. It then requires classification of the status of the water bodies and their restoration to at least 'good status' in a specified period. 2. Though there are many methods for assessing water quality, none has the scope of that defined in the Directive. The provisions of the Directive require a wide range of variables to be measured and give only general guidance as to how systems of classification should be established. This raises issues of comparability across States and of the costs of making the determinations. 3. Using expert workshops and subsequent field testing, a practicable pan-European typology and classification system has been developed for shallow lakes, which can easily be extended to all lakes. It is parsimonious in its choice of determinands, but based on current limnological understanding and therefore as cost-effective as possible. 4. A core typology is described, which can be expanded easily in particular States to meet local conditions. The core includes 48 ecotypes across the entire European climate gradient and incorporates climate, lake area, geology of the catchment and conductivity. 5. The classification system is founded on a liberal interpretation of Annexes in the Directive and uses variables that are inexpensive to measure and ecologically relevant. The need for taxonomic expertise is minimized. 6. The scheme has been through eight iterations, two of which were tested in the field on tranches of 66 lakes. The final version, Version 8, is offered for operational testing and further refinement by statutory authorities.

The seasonal features of the water chemistry in the saline shallow lakes Laguna de Manjavacas and Laguna del Pueblo (Castilla – La Mancha, Central Spain) were studied during 1990–1991 and in 1997. These lakes were both affected by sewage inputs driving them to a high trophic status. However, whereas sewage inputs entered Laguna del Pueblo directly, wastewater reached Laguna de Manjavacas after running for 8 km through a small riverbed, where natural processes caused partial mineralisation of organic matter. Moreover, water quality was further improved before entering the main water body of Laguna de Manjavacas, since water crossed through a wetland and high amounts of organic matter and inorganic nutrients were retained there. Anyway, in both lakes spatial heterogeneity was mainly associated with the distance to sewage inputs, and this was also reflected by the sediment chemistry. The patterns of water evaporation and precipitation-dissolution of salts strongly determined the salinity of their waters. During the warmest period (which coincided with the main drought period) water losses by evaporation increased water salinity, whereas a higher dilution was found during the cold rainy period. However, the relatively higher amount of low-salinity sewage inputs in Laguna del Pueblo allowed this lake to maintain its hyposaline characteristics. In contrast, Laguna de Manjavacas shifts from hyposaline to hypersaline following the seasonal cycle with different rain and temperature regimes, as the relative importance of the permanent wastewater inputs was lower here than in Laguna del Pueblo. Inorganic nutrient dynamics was determined in both lakes both by the sewage supply and by consumption by phytoplankton, with soluble P depletion following algal blooms.

Eutrophication in coastal wetlands has increased greatly because of human impact, reducing water quality and affecting aquatic plants. The aim of the present study was to investigate the eutrophication of Mediterranean wetlands and their possible recovery. An in situ mesocosm nutrient enrichment experiment was performed in a coastal shallow lake from eastern Spain, holding dense Chara meadows. In this lake, 36 mesocosms were installed and fertilised weekly with four levels of N and P addition over an 8-week period from June to August. Mesocosms fertilised with the two higher levels (N:P ≥5:0.5mgL–1) shifted to turbid status with macrophyte loss before Week 4. Saturation concentrations were similar under these two conditions, with averages ~1.0mgL–1 total particulate P and 700µgL–1chlorophyll-a reached in the last 3 weeks. After 5 weeks of the experiment, macrophytes were removed from the mesocosms without nutrient addition and those fertilised with 1:0.1mgL–1 N:P. Macrophyte removal resulted in a release of phosphate and ammonium from sediments, enhancing eutrophication. Three months after stopping nutrient addition, high nutrient and chlorophyll concentrations persisted in the highly fertilised mesocosms, but decreased in the low fertilised mesocoms, which shows that restoration of eutrophic Mediterranean shallow lakes depends to a great extent on previous external loads.

Lake Arcas exhibits a thermal stratification from April to October. A sulfide-rich anoxic hypolimnion is then formed between the deeper part of the thermocline and the lake bottom, and high population densities of phototrophic microorganisms are found at the oxic-anoxic interface. Chromatium weissei, a large rod, 8 × 4 μm in size, was the dominant phototrophic bacterium, reaching densities of up to 1.84 × 106 cells ml-1. Other phototrophic sulfur bacteria, such as Amoebobacter cf. purpureus, Thiocapsa sp., and Pelodictyon clathratiforme were also present in the anoxic hypolimnion, but their cell size and population densities were much lower. Net growth rates (0.125 to —0.123 d-1) and frequency of dividing cells, indicated that C. weissei grew most rapidly in the upper part of the phototrophic bacterial layer. The highest growth rates were found during the first half of the stratification period, with a marked decrease in population density as mixing approached. Our results suggest that purple sulfur bacteria in Lake Arcas are light limited, even though they possess okenone, which can efficiently harvest light at the wavelengths penetrating to the chemocline. High rates of carbon photoassimilation by phototrophic bacteria were measured (up to 200 mg C m-3 h-1), but because of the narrow depth range in which anoxygenic photosynthesis occur, bacterial contribution to overall primary production during summer was estimated to be only 12—13%.

The seasonal population dynamics of phototrophic sulphur bacteria and their vertical stratification in Lake La Cruz were studied over two consecutive summers. Development of purple sulphur bacteria occurred just below the oxic-anoxic boundary (the plate located at 14-15 m depth). The principal constituent was a species of Amoebobacter, containing okenone as its main carotenoid and which reached maximal densities at the end of summer (2.2 × 10 6 cells/ml and BChl.-a concentrations of 111 μg/l in September 1987). Green phototrophic bacteria developed below the Amoebobacter layer at a mean depth of 16 m. Pelodictyon clathratiforme was the dominant species, reaching maximal cell concentrations of 3.1 × 10 6 cells/ml and BChl.-d concentrations of 362 μg/l, also in September. Growth of these purple and green sulphur bacteria was light-limited, and sulphide was also present in very low concentrations owing to the low sulphate content of the lake. The two thermal stratification periods under study differed noticeably as a consequence of altered meteorological conditions and structural differences in the water column, with a shallower oxic-anoxic boundary and a major development of algal populations in the upper oxic layer during the second period. This reduced the light available to deep phototrophic bacteria, which were unable to attain the biomass achieved in the earlier period. The monimolimnion of Lake La Cruz acts as a refuge for phototrophic bacteria during the mixing period and this is considered to be a key factor in understanding the ecology of these microorganisms.

In a three-year field survey which included some ecophysiological studies, the ecology of a deep living Oscillatoria (= Planktothrix) cf. ornata population at the chemocline and in the hypolimnion of the sulphate-rich karstic Lake Arcas was studied. This cyanobacterium, together with the phototrophic sulphur bacterium, Chromatium weissei, develops dense populations in the anoxic waters of the lake during the summer stratification (maximal cyanobacterial population densities were around 1,300 filaments/ml), both being absent from the water column during the mixing period. O. cf. ornata from Lake Arcas shows several adaptative features which help to explain the development of these dense populations. Phycoerythrin, the main light-harvesting accessory pigment, allows this cyanobacterium to collect efficiently the yellow-green light reaching the chemocline, which can only be used via photosystem II. Oxygen-evolving photosynthesis in this species is sulphide-resistant, it can be sustained at the sulphide concentrations found at the chemocline of the lake. In addition, buoyancy regulation mediated by gas-vesicle formation and carbohydrate accumulation substantially overcomes sinking losses in the population.

Ants are ecologically dominant and have been used as valuable bio-indicators of environmental change or disturbance being used in monitoring inventories. However, the majority of inventories has concentrated in ground-dwelling ant fauna disregarding the arboreal fauna. This paper aimed to list the ant species collected both on the ground and in the vegetation of the Parque Estadual do Cristalino, an important protected site in the center of the southern Amazon. Moreover, we compared the composition of the ground dwelling and vegetation foraging ants. Was sampled 203 species distributed among 23 genera and eight subfamilies, wherein 35 species had not yet been reported in the literature for Mato Grosso State. As expected, the abundance and richness of ants was higher on the ground than in the understory. Also, the ant assemblages composition was different between these habitats (with only 20% occurring in both). It indicate that complementary methods which include arboreal and terrestrial ants are indicated for efficient inventory. This study provides an inventory of the arboreal and ground ant fauna contributing to the knowledge and conservation of ant fauna of the Amazonian.