scholarly journals Diatom-inferred aquatic impacts of the mid-Holocene eruption of Mount Mazama, Oregon, USA

2018 ◽  
Vol 91 (1) ◽  
pp. 163-178 ◽  
Author(s):  
Joanne Egan ◽  
Timothy E.H. Allott ◽  
Jeffrey J. Blackford

AbstractHigh-resolution diatom stratigraphies from mid-Holocene sediments taken from fringe and central locations in Moss Lake, a small lake in the foothills of the Cascade Range, Washington, have been analyzed to investigate the impacts (and duration) of tephra deposition on the aquatic ecosystem. Up to 50 mm of tephra was deposited from the climactic eruption of Mount Mazama 7958–7795 cal yr BP, with coincident changes in the aquatic ecosystem. The diatom response from both cores indicates a change in habitat type following blanket tephra deposition, with a decline in tychoplanktonic Fragilaria brevistriata and Staurosira venter and epiphytic diatom taxa indicating a reduction in aquatic macrophyte abundance. Additionally, the central core shows an increase in tychoplanktonic Aulacoseira taxa, interpreted as a response to increased silica availability following tephra deposition. Partial redundancy analysis, however, provides only limited evidence of direct effects from the tephra deposition, and only from the central core, but significant effects from underlying environmental changes associated with climatic and lake development processes. The analyses highlight the importance of duplicate analyses (fringe and central cores) and vigorous statistical analyses for the robust evaluation of aquatic ecosystem change.

Oecologia ◽  
2021 ◽  
Author(s):  
Jörg Bendix ◽  
Nicolay Aguire ◽  
Erwin Beck ◽  
Achim Bräuning ◽  
Roland Brandl ◽  
...  

AbstractTropical mountain ecosystems are threatened by climate and land-use changes. Their diversity and complexity make projections how they respond to environmental changes challenging. A suitable way are trait-based approaches, by distinguishing between response traits that determine the resistance of species to environmental changes and effect traits that are relevant for species' interactions, biotic processes, and ecosystem functions. The combination of those approaches with land surface models (LSM) linking the functional community composition to ecosystem functions provides new ways to project the response of ecosystems to environmental changes. With the interdisciplinary project RESPECT, we propose a research framework that uses a trait-based response-effect-framework (REF) to quantify relationships between abiotic conditions, the diversity of functional traits in communities, and associated biotic processes, informing a biodiversity-LSM. We apply the framework to a megadiverse tropical mountain forest. We use a plot design along an elevation and a land-use gradient to collect data on abiotic drivers, functional traits, and biotic processes. We integrate these data to build the biodiversity-LSM and illustrate how to test the model. REF results show that aboveground biomass production is not directly related to changing climatic conditions, but indirectly through associated changes in functional traits. Herbivory is directly related to changing abiotic conditions. The biodiversity-LSM informed by local functional trait and soil data improved the simulation of biomass production substantially. We conclude that local data, also derived from previous projects (platform Ecuador), are key elements of the research framework. We specify essential datasets to apply this framework to other mountain ecosystems.


2014 ◽  
Vol 86 (4) ◽  
pp. 1735-1747 ◽  
Author(s):  
ANA EMILIA SIEGLOCH ◽  
MARCIA SURIANO ◽  
MARCIA SPIES ◽  
ALAÍDE FONSECA-GESSNER

The aim of this study was to test the effect of agricultural and forestry land use on the structure of mayfly assemblages in low-order streams. Twenty-nine headwater streams were investigated in the state of São Paulo. We analyzed 15 streams in pristine areas (mixed tropical rainforest, semideciduous forest and dense tropical rainforest), and 14 streams covered with sugarcane, eucalyptus and pasture. Mayfly richness obtained by rarefaction curves was higher in pristine areas (21 genera), especially in mixed and semideciduous forest when compared to land use (9 genera), where values were particularly low in sugarcane plantation (3 genera). The non-metric multidimensional scaling (NMDS) ordination showed clear difference in mayfly assemblages between land uses and pristine areas, supported by analysis of similarity (R=0.67, p=0.001). In partial redundancy analysis (pRDA), the environmental descriptors that best explained differences in assemblage structure were Riparian, Channel and Environmental Inventory (RCE) index score, percentage of fine sediment stream substrate, water pH and land elevation. Our results show that agricultural and forestry land use has a strong negative effect on the structure of mayfly assemblages. These results also support the use of mayflies as environmental indicators, as some genera were sensitive to changes in land use, while others responded to naturally occurring changes in the study area.


2011 ◽  
Vol 45 (3) ◽  
pp. 339-352 ◽  
Author(s):  
Minna Väliranta ◽  
Jan Weckström ◽  
Susanna Siitonen ◽  
Heikki Seppä ◽  
Jyri Alkio ◽  
...  

2019 ◽  
Author(s):  
Gregory J. Barord ◽  
Rebecca L. Swanson ◽  
Peter D. Ward

AbstractThe nautiloid lineage extends back nearly 500 million years but today, is represented by only two living genera, Nautilus and Allonautilus. Behavioral observations of these living nautiluses have improved our understanding of how nautiloids, and ammonoids, behaved and interacted in their environment. These behaviors may also help to inform conservation practices. Here, we describe feeding and mating behaviors in wild nautiluses not reported from any other population. In Palau, Nautilus belauensis was observed actively preying on a large, living crab (Chaceon sp.) and performing courtship-like behaviors prior to mating. These behaviors occurred across multiple nights and from different nautiluses, suggesting that the behaviors are characteristic of at least a subset of the population, if not the entire population. Perhaps the behaviors exhibited by the Palauan nautiluses are an outlier and simply a localized characteristic of a far-removed population. Or, perhaps these apparent abnormal behaviors of Palauan nautiluses are what all nautiluses across the Indo-Pacific should be exhibiting. If the latter explanation is correct, we can start to address the potential causes of the behavioral differences, such as population size, habitat type, and prey availability. In either case, this apparent behavioral plasticity may have also been a reason that the nautiloid lineage has been able to survive throughout millions of years of environmental changes. Today, these behavioral observations could prove to be a valuable conservation tool to protect species and environments, especially in the deep-sea ecosystem the nautiluses inhabit.


2020 ◽  
Vol 21 (2) ◽  
Author(s):  
MOHAMMAD LIWA ILHAMDI ◽  
AGIL AL IDRUS ◽  
DIDIK SANTOSO ◽  
Gito Hadiprayitno

Abstract. Ilhamdi ML, Al Idrus A, Santoso D, Hadiprayitno G. 2020. Short Communication: Community structure and diversity of Odonata in Suranadi Natural Park, West Lombok Indonesia. Biodiversitas 21: 718-723. Odonata is an order of insects. The life cycle of this order is dependent on freshwater habitat. Sensitivity to environmental changes causes odonates to be important bioindicators of ecosystem change. The importance of the ecological role of odonates is not followed by adequate scientific information on Odonata communities, especially in the Suranadi Natural Park (SNP). The study aimed to monitor the existence and community structure of Odonata in the SNP area every six months in period. The data collection technique was using a survey method by following the transect line, namely the waterway transect line (WTL), plantation border transect (PT) and settlement border transect (ST). Data collection was done 4 times from April to May 2019, once every 2 weeks. The sampling was done twice in the morning from 08.00 to 11.00 AM and in the afternoon from 03.00 to 05.00 PM. Data were analyzed using the relative frequency equation and Diversity Index. The results showed that there were 16 species of odonates consisting of the family Libellulidae (11 species), Platycnemididae (1 species), Chlorocyphidae (1 species), and Coegrinidae (3 species). Orthetrum sabina, Neurothemis ramburii, Diplacodes trivialis, Gynacantha subinterrupta, Copera marginipes, and Pantala flavescens, are species that are present in all of each observation sites. The waterway transect has the highest diversity index (2.027), followed by settlement transect (1.367), and the lowest is plantation transect (1.131).


2021 ◽  
Author(s):  
Chris D Thomas ◽  
Jane K Hill ◽  
Caroline Ward ◽  
Jack H Hatfield

SummaryWe propose an approach to conservation centred on achieving positive future trajectories of dynamic change, applied to all locations and species, and based on societal inclusiveness. Strategies to facilitate change. We take an Anthropocene perspective, in which human society and biodiversity have been inextricably linked for over 10,000 years, and continuing biodiversity change is inevitable. The challenge is to identify circumstances under which change is acceptable or beneficial, without being tied to specific historic baselines. We outline a Resist-Accept-Facilitate (RAF) framework that could be applied to all conservation activities, from high-level planning and measurement (indicators) through to practical land and species management, to ensure that the facilitation of future biodiversity benefits receives as much attention as the resistance of change.Everywhere is important. Different places are important for different things, such as particular species or ecosystem services, and people vary in how they value these features. We suggest a perspective whereby we evaluate what every area is most important for, and what they could be most important for in future by considering possible trajectories of biodiversity and ecosystem change. We propose zoning any region of interest, such as the UK, and applying the RAF framework in an inclusive manner to develop conservation strategies that are appropriate in each location and zone. This RAF approach will reconcile different conservation philosophies (such as traditional management, land-sharing/sparing, rewilding, novel ecosystems, ecosystem services, human wellbeing) because different conservation outcomes will emerge in different zones.Enabling species to move. Genes and species undertake changes to their abundances and distributions in response to climatic and other environmental changes. We suggest that trans situ conservation be developed as a complement to traditional in situ (sites in the wild) and ex situ (in captivity) conservation. Trans situ conservation primarily involves Accept and Facilitate interventions within the RAF framework. It requires consideration of the connectedness and permeability of regions (facilitating colonisation for a majority of species and genes) and the value of new populations of colonising species and novel communities that arise from species range shifts. Trans situ conservation also considers the potential to translocate (assisted colonisation) species and genes that are unable to shift their distributions without direct intervention, highlighting the transnational needs of globally-threatened species rather than locally-rare ones whose future is secure elsewhere.For everyone. The justification for conservation commonly focuses attention on the benefits that individuals and society derive from the natural world, yet the benefits are not shared equitably. The RAF approach asks people from a wide range of backgrounds ‘what they want’ from local landscapes so as to inform the development of more inclusive approaches to conservation both now and in the future. We identify ways in which the processes of conservation could incorporate an increased diversity of perspectives, whilst continuing to be informed by data and professional expertise.


2003 ◽  
Vol 60 (6) ◽  
pp. 721-730 ◽  
Author(s):  
Kyle D Zimmer ◽  
Mark A Hanson ◽  
Malcolm G Butler

Phytoplankton abundance and nutrient concentrations in shallow-water ecosystems are influenced by submerged macrophytes, zooplankton, and fish, but few studies have simultaneously assessed the influence of all three variables. We sampled 18 semipermanent prairie wetlands for 5 years to assess influences of minnows, submersed macrophytes, cladocerans, and drainage history on phytoplankton abundance and concentrations of nitrogen (N) and phosphorus (P). Our macrophyte data reflect the abundance of three distinct species assemblages (Chara, Potamogeton, and Myriophyllum assemblages) typical of these wetlands. Partial redundancy analysis showed only the Chara and Potamogeton assemblages and fish to be significantly related to algal abundance, N, and P. Macrophytes and fish together explained 40% of the total variance, but the Chara assemblage explained threefold, and the Potamogeton assemblage twofold, more variance than did presence/absence of fish. However, relationships with N and P differed for the two groups of macrophytes: P showed a strong negative relationship with both plant assemblages, and N showed a weak negative relationship with Chara but no relationship with Potamogetons. Our results indicate that phytoplankton and nutrient concentrations in prairie wetlands are strongly influenced by submersed macrophytes, although influences may depend on plant community composition.


2010 ◽  
Vol 26 (4) ◽  
pp. 423-432 ◽  
Author(s):  
Tiago da Silveira Vasconcelos ◽  
Tiago Gomes dos Santos ◽  
Célio Fernando Baptista Haddad ◽  
Denise de Cerqueira Rossa-Feres

Abstract:Because anuran species are highly dependent on environmental variables, we hypothesized that anuran species richness and the number of reproductive modes from different Brazilian localities vary according to climatic and altitudinal variables. Published data were compiled from 36 Brazilian localities and climatic and altitudinal data were extracted from an available database. A partial redundancy analysis (pRDA) showed that 23.5% of the data set's variation was explained by climatic and altitudinal data, while the remaining 76.5% remained unexplained. This analysis suggests that other factors not analysed herein may also be important for predicting anuran species richness and the number of reproductive modes in Brazil. Altitude and total annual rainfall were positively correlated with anuran species richness and the number of reproductive modes, and total annual rainfall was strongly associated with these two biotic variables in the triplot of pRDA. The positive association of total annual rainfall and the negative association of the concentration of annual rainfall were already expected based on physiological and reproductive requirements of anurans. On the other hand, temperature was not associated with richness or the number of reproductive modes.


2018 ◽  
Author(s):  
Sara F. Paver ◽  
Daniel J. Muratore ◽  
Ryan J. Newton ◽  
Maureen L. Coleman

AbstractMarine and freshwater microbial communities are phylogenetically distinct and transitions between habitat types are thought to be infrequent. We compared the phylogenetic diversity of marine and freshwater microorganisms and identified specific lineages exhibiting notably high or low similarity between marine and freshwater ecosystems using a meta-analysis of 16S rRNA gene tag-sequencing datasets. As expected, marine and freshwater microbial communities differed in the relative abundance of major phyla and contained habitat-specific lineages; at the same time, however, many shared taxa were observed in both environments. Betaproteobacteria and Alphaproteobacteria sequences had the highest similarity between marine and freshwater sample pairs. Gammaproteobacteria and Alphaproteobacteria contained the highest number of Minimum Entropy Decomposition nodes shared by marine and freshwater samples. Shared nodes included lineages of the abundant alphaproteobacterial group SAR11 that have not previously been reported in 16S rRNA gene surveys of freshwater lakes. Our results suggest that shared taxa are numerous, but tend to occur sporadically and at low relative abundance in one habitat type, leading to an underestimation of transition frequency between marine and freshwater habitats. Lineages with a high degree of shared taxa or habitat-specific diversification represent targets for genome-scale investigations into microbial adaptations and evolutionary innovations. Rare taxa with abundances near or below detection, including lineages that appear to have crossed the salty divide relatively recently, may have novel adaptations enabling them to exploit opportunities for niche expansion when environments are disturbed or conditions change.ImportanceThe distribution of microbial diversity across environments yields insight into processes that create and maintain this diversity as well as potential to infer how communities will respond to future environmental changes. We integrated datasets from dozens of freshwater lake and marine samples to compare diversity across open water habitats differing in salinity. Our novel combination of sequence-based approaches revealed phyla and proteobacterial classes inferred to include more or less recent transitions across habitat types as well as specific lineages that are shared by marine and freshwater environments at the level of 16S rRNA sequence types. Our findings contribute to understanding the ecological and evolutionary controls on microbial distributions, and open up new questions regarding the plasticity and adaptability of particular lineages.


2021 ◽  
Vol 8 ◽  
Author(s):  
Peter M. Almond ◽  
Katrin Linse ◽  
Simon Dreutter ◽  
Susie M. Grant ◽  
Huw J. Griffiths ◽  
...  

Habitat heterogeneity is important for maintaining high levels of benthic biodiversity. The Prince Gustav Channel, on the Eastern Antarctic Peninsula, is characterized by an array of habitat types, ranging from flat, mud-dominated sheltered bays to steep and rocky exposed slopes. The channel has undergone dramatic environmental changes in recent decades, with the southern end of the channel permanently covered by the Prince Gustav Ice Shelf until it completely collapsed in 1995. Until now the marine benthic fauna of the Prince Gustav Channel has remained unstudied. A shallow underwater camera system and Agassiz trawl were deployed at different locations across the channel to collect information on habitat type and heterogeneity, benthic community composition and macrofaunal biomass. The texture of the seafloor was found to have a significant influence on the benthos, with hard substrates supporting higher abundances and diversity. Suspension and filter feeding organisms, including porifera, crinoids, and anthozoans, were strongly associated with hard substrates, with the same being true for deposit feeders, such as holothurians, and soft sediments. Habitat heterogeneity was high across the Prince Gustav Channel, particularly on a local scale, and this was significant in determining patterns of benthic composition and abundance. Other physical variables including depth and seafloor gradient played significant, interactive roles in determining composition potentially mediated through other processes. Sites that were once covered by the Prince Gustav Ice Shelf held distinct and unique communities, suggesting that the legacy of the ice shelf collapse may still be reflected in the benthos. Biomass estimations suggest that critical thresholds of vulnerable marine ecosystem indicator taxa, as defined by the Commission for the Conservation of Antarctic Marine Living Resources, have been met at multiple locations within the Prince Gustav Channel, which has implications for the future establishment of no take zones and marine protected areas within the region.


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