Structure and succession dynamics of a Neotropical freshwater periphyton community, with emphasis on ciliates and their association with bacterial taxa

Periphyton communities in freshwater systems play an essential role in biogeochemical processes, but knowledge of their structure and dynamics lags far behind other environments. We used eDNA metabarcoding of 16S and 18S rRNA markers to investigate the formation and establishment of a periphytic community, in addition to morphology-based analyses of its most abundant group (peritrich ciliates). We sampled two nearby sites within a large Neotropical lake at four time points, aiming to assess whether periphyton establishment can be replicated on this local scale. Producers and denitrifiers were abundant in the community, illustrating the relevant role of biofilms in freshwater nutrient recycling. Among microeukaryotes, peritrich ciliates dominated the community, with genera Epistylis and Vorticella being the most abundant and showing a clear succession at both sites. Other ciliates were identified and, in some cases, their occurrence was strongly related to bacterial abundance. The structure and succession dynamics of both prokaryotic and eukaryotic components of periphyton differed between the two sites, in spite of their adjacent locations and similar abiotic properties, indicating that the establishment of these communities can vary even on a local scale within a lake ecosystem.

Communities of T4-like bacteriophages associated with bacteria in Lake Baikal: diversity and biogeography

Lake Baikal phage communities are important for lake ecosystem functioning. Here we describe the diversity of T4-bacteriophage associated with the bacterial fraction of filtered water samples collected from the pelagic zone, coastal zone and shallow bays. Although the study of the diversity of phages for the g23 gene has been carried out at Lake Baikal for more than ten years, shallow bays that comprise a significant part of the lake’s area have been neglected, and this gene has not previously been studied in the bacterial fraction. Phage communities were probed using amplicon sequencing methods targeting the gene of major capsid protein (g23) and compared phylogenetically across sample locations and with sequences previously retrieved from non-bacterial fractions (<0.2 um) and biofilms (non-fractionated). In this study, we examined six water samples, in which 24 to 74 viral OTUs were obtained. The sequences from shallow bays largely differed from those in the pelagic and coastal samples and formed individual subcluster in the UPGMA tree that was obtained from the comparison of phylogenetic distances of g23 sequence sets from various ecosystems, reflecting differences in viral communities depending on the productivity of various sites of Lake Baikal. According to the RefSeq database, from 58.3 to 73% of sequences of each sample had cultivated closest relatives belonging to cyanophages. In this study, for phylogenetic analysis, we chose the closest relatives not only from the RefSeq and GenBank NR databases but also from two marine and one freshwater viromes: eutrophic Osaka Bay (Japan), oligotrophic area of the Pacific Ocean (Station ALOHA) and mesotrophic and ancient Lake Biwa (Japan), which allowed us to more fully compare the diversity of marine and freshwater phages. The identity with marine sequences at the amino acid level ranged from 35 to 80%, and with the sequences from the viral fraction and bacterial one from Lake Biwa—from 35.3 to 98% and from 33.9 to 89.1%, respectively. Therefore, the sequences from marine viromes had a greater difference than those from freshwater viromes, which may indicate a close relationship between freshwater viruses and differences from marine viruses.

Contribution of invasive bivalves (Dreissena spp.) to element distribution: phase interaction, regional and seasonal comparison in a large shallow lake

After introduction, the invasive bivalve dreissenids became key species in the biota of Lake Balaton, the largest shallow lake in Central Europe. The contribution of dreissenid soft tissue and shell, as biotic phases, in element distribution and its interaction with the water and upper sediment phases were examined in two basins with different trophic conditions in spring and autumn. Six metals (Ba, Cu, Fe, Mn, Pb, Zn) were detected in all investigated phases. In general, metals were abundant in the water and soft tissue in the eastern basin in spring, and in the sediment and shells in the western basin in autumn. This might be associated with the more urbanized surroundings in the eastern, and the enhanced organic matter production in the western basin. High relative shares of Ba, Cu, Mn, and Pb were associated with the water and shell samples, whereas high shares of Fe and Zn were noted in the soft mussel tissue and sediments. Results suggest that dynamics of metal uptake by dreissenids depend on the seasonal change in metabolic activity. Shell metal content is less changeable; shells might absorb metals from both the soft tissue and water phases. Metallothionein peptides, the scavengers of intracellular metals, were determined to be biomarkers of the bulk contaminants rather than only metals. The present study shows that invasive bivalves, with high abundance, filtering activity, and storing capacity can significantly contribute to element distribution in the shoreline of a shallow lake ecosystem.

Critical Transitions in Lake Ecosystem State May Be Driven by Coupled Feedback Mechanisms: A Case Study from Lake Erhai, China

Critical transitions between ecosystem states can be triggered by relatively small external forces or internal perturbations and may show time-lagged or hysteretic recovery. Understanding the precise mechanisms of a transition is important for ecosystem management, but it is hampered by a lack of information about the preceding interactions and associated feedback between different components in an ecosystem. This paper employs a range of data, including paleolimnological, environmental monitoring and documentary sources from lake Erhai and its catchment, to investigate the ecosystem structure and dynamics across multiple trophic levels through the process of eutrophication. A long-term perspective shows the growth and decline of two distinct, but coupled, positive feedback loops: a macrophyte-loop and a phosphorus-recycling-loop. The macrophyte-loop became weaker, and the phosphorus-recycling-loop became stronger during the process of lake eutrophication, indicating that the critical transition was propelled by the interaction of two positive feedback loops with different strengths. For lake restoration, future weakening of the phosphorus-recycling loop or a reduction in external pressures is expected to trigger macrophyte growth and eventually produce clear water conditions, but the speed of recovery will probably depend on the rates of feedback loops and the strength of their coupling.

Levantamento Florístico da Área de Proteção Ambiental (APA) da Lagoa da Maraponga, Fortaleza, Ceará, Brasil

A Área de Proteção Ambiental (APA) da Lagoa da Maraponga é uma unidade de conservação municipal localizada no bairro Maraponga, município de Fortaleza, estado do Ceará. Composto predominantemente por um ecossistema lacustre, no qual se destaca a Lagoa da Maraponga, com área de 31 hectares, ameaçada pela ação antrópica, fazendo com que a conservação se torne uma prioridade. Objetivou-se fazer o levantamento florístico da APA da Lagoa da Maraponga e elaborar um guia de campo. Foram realizadas coletas botânicas, observações de campo, fotografias e identificações das espécies. Registraram-se 98 espécies pertencentes a 82 gêneros e 37 famílias botânicas. As famílias mais representativas foram Fabaceae (18 spp.), Malvaceae (13 spp.), Asteraceae (dez spp.), Rubiaceae (cinco spp.), Arecaceae, Convolvulaceae e Solanaceae (quatro spp., cada). Constatou-se que o hábito das espécies tem como predomínio o porte herbáceo (41 spp.), seguido de espécies subarbustivas (19 spp.), arbóreas (17 spp.), arbustivas (dez spp.), trepadeiras (sete spp.) e palmeiras (quatro spp.). Conclui-se que esta área tem demonstrado que mesmo com a interferência humana e o grande avanço da urbanização em seus arredores, a flora local apresenta elevada riqueza de espécies nativas que precisa ser conservada, mantida e reconhecida por políticas públicas e pela sociedade, as quais podem ser auxiliadas pelo guia de campo elaborado. Floristic Survey of the Environmental Protection Area (EPA) of Maraponga Lagoon, Fortaleza, Ceará, Brazil A B S T R A C TThe Maraponga Lagoon Environmental Protection Area (EPA) is a municipal conservation unit located in the Maraponga neighborhood, in the municipality of Fortaleza, state of Ceará. Composed predominantly of a lake ecosystem, in which the Maraponga Lagoon stands out, with an area of 31 hectares, threatened by anthropic action, prioritizing conservation. The objective was to carry out the floristic survey of the EPA of Maraponga Lagoon and to prepare a field guide. Botanical collections, field observations, photographs and species identification were carried out. A total of 98 species belonging to 82 genera and 37 botanical families were registered. The most representative families were Fabaceae (18 spp.), Malvaceae (13 spp.), Asteraceae (ten spp.), Rubiaceae (five spp.), Arecaceae, Convolvulaceae and Solanaceae (four spp., each). It was found that the habit of the species predominates the herbaceous size (41 spp.), followed by sub-shrubs (19 spp.), trees (17 spp.), shrubs (ten spp.), climbing plants (seven spp.) and palm trees (four spp.). It’s concluded that this area has shown that even with human interference and the great advance of urbanization in its surroundings, the local flora has a high number of native species that need to be conserved, maintained and recognized by public policies and society, which can be assisted by the field guide prepared.Keywords: Urban biodiversity, conservation, vegetable diversity, richness, conservation unit.

Natural and anthropogenic changes threatening the ecological and limnological integrity of Lake Baringo, Kenya: A Review

Lakes are characterized by dynamic responses to ecological and limnologic disturbances that occur within a constrained timeframe. Some endorheic lakes in the Kenyan Rift valley are presently regarded as environmental hotspots because of complex changes that are revealed through multiple proxies; changing lake levels and surface area, turbidity and sedimentation, proliferation of macrophytes and loss of aquatic biodiversity. Lake Baringo is characterized by widespread catchment degradation accompanied by high levels of turbidity during erratic and decline of native fishery based on Oreochromis niloticus baringoensis. A careful analysis implicates potential natural factors such as catchment topography and increasing anthropogenic pressure as the main causes of lake ecosystem degradation. This paper recommends several strategies for restoration of Lake Baringo based on an integrated multi-faceted approach which combines catchment rehabilitation, pollution control and provision of alternative livelihoods such as agriculture to the riparian communities.