The use of soil biostructures created by soil fauna ecosystem engineers fed with different organic matterials as inoculum source of arbuscular mycorrhiza fungi on cocoa seedling

<p><span lang="IN">Soil fauna as ecosystem engineers </span><span>have the ability to </span><span lang="IN">creat</span><span>e </span><span lang="IN">soil biostructure</span><span>s, with the capacity to </span><span lang="IN">sav</span><span>e</span><span lang="IN"> arbuscular mycorrhizal fungi (AMF) spores. </span><span>This study therefore aims to </span><span lang="IN">investigate the </span><span>AMF </span><span lang="IN">spore density in the biostructures created by cooperation between earthworms and ants with a different organic matter composition</span><span>,</span><span lang="IN"> and to analyze the </span><span>biostructures’ </span><span lang="IN">potential as a source of </span><span>AMF </span><span lang="IN">inoculum on cocoa seedlings. </span><span>In the first experiment, a </span><span lang="IN">combination of earthworms and ants composition</span><span>, as well as a </span><span lang="IN">mixture of <em>G. sepium</em> leaf (GLP), cocoa shell bean (CSB), and sago dregs (SD)</span><span>,</span><span lang="IN"> was tested</span><span>. Meanwhile, </span><span lang="IN">in the </span><span>second</span><span lang="IN"> experiment</span><span>, t</span><span lang="IN">he</span><span> effect of</span><span lang="IN"> biostructures on cocoa seedlings grown </span><span>i</span><span lang="IN">n unsterile soil</span><span>,was </span><span lang="IN">examined</span><span>. According to the results, the highest</span><span lang="IN"> AMF spore </span><span>density was obtained using </span><span lang="IN">20 earthworms+10 ants with 50%GLP+50%CSB + 0%SD treatment</span><span>. Furthermore, the t</span><span lang="IN">otal AMF spores </span><span>were </span><span lang="IN">positively correlated</span><span> with the total P value, but negatively correlated </span><span lang="IN">with </span><span>the </span><span lang="IN">C/N ratio</span><span>. Therefore, bi</span><span lang="IN">ostructure application increased AMF spores number in rhizosphere and </span><span>the cocoa seedling’s </span><span lang="IN">root infection</span><span>. Furthermore, </span><span lang="IN">biostructure</span><span>s</span><span lang="IN"> resulting from the collaborative activity </span><span>between</span><span lang="IN"> different soil fauna ecosystem engineers </span><span>were able to transmit </span><span lang="IN">AMF spore</span><span>s </span><span lang="IN">to </span><span>infected </span><span lang="IN">plant root</span><span>s</span><span lang="IN"> growing </span><span>i</span><span lang="IN">n non-sterile soil.</span></p>

Protozoa populations are ecosystem engineers that shape prokaryotic community structure and function of the rumen microbial ecosystem

Unicellular eukaryotes are an integral part of many microbial ecosystems where they interact with their surrounding prokaryotic community—either as predators or as mutualists. Within the rumen, one of the most complex host-associated microbial habitats, ciliate protozoa represent the main micro-eukaryotes, accounting for up to 50% of the microbial biomass. Nonetheless, the extent of the ecological effect of protozoa on the microbial community and on the rumen metabolic output remains largely understudied. To assess the role of protozoa on the rumen ecosystem, we established an in-vitro system in which distinct protozoa sub-communities were introduced to the native rumen prokaryotic community. We show that the different protozoa communities exert a strong and differential impact on the composition of the prokaryotic community, as well as its function including methane production. Furthermore, the presence of protozoa increases prokaryotic diversity with a differential effect on specific bacterial populations such as Gammaproteobacteria, Prevotella and Treponema. Our results suggest that protozoa contribute to the maintenance of prokaryotic diversity in the rumen possibly by mitigating the effect of competitive exclusion between bacterial taxa. Our findings put forward the rumen protozoa populations as potentially important ecosystem engineers for future microbiome modulation strategies.

Can Plants Be Engineers?

When we think of engineers, we think of making a machine, like a car. Are there engineers for ecosystems? When an organism can make big changes to its environment, we call it an ecosystem engineer. In aquatic ecosystems like the San Francisco Estuary, underwater plants can be important ecosystem engineers because they can change water flow and water clarity. In the Estuary, a plant called Brazilian waterweed, which was introduced by humans, is one of the most important ecosystem engineers. With its leaves and stems, this plant traps tiny particles floating in the water, making the water clearer. Clearer water has made it easier for more plants to grow and these changes helped some non-native fish species to increase in number, while some native species declined. Introduction of Brazilian waterweed has led to an entirely different ecosystem, which has also affected how people use and take care of the Estuary.

The role of ecosystem engineers in shaping the diversity and function of arid soil bacterial communities

Ecosystem engineers (EEs) are present in every environment and are known to strongly influence ecological processes and thus shape the distribution of species and resources. In this study, we assessed the direct and indirect effect of two EEs (perennial shrubs and ant nests), individually and combined, on the composition and function of arid soil bacterial communities. To that end, topsoil samples were collected in the Negev desert highlands during the dry season from four patch types: (1) barren soil; (2) under shrubs; (3) near ant nests; or (4) near ant nests situated under shrubs. The bacterial community composition and potential functionality were evaluated in the soil samples (14 replicates per patch type) using 16S rRNA gene amplicon sequencing together with physico-chemical measures of the soil. We have found that the EEs affected the community composition differently. Barren patches supported a soil microbiome, dominated by Rubrobacter and Proteobacteria, while in EE patches Deinococcus-Thermus dominated. The presence of the EEs similarly enhanced the abundance of phototrophic, nitrogen cycle, and stress-related genes. In addition, the soil characteristics were altered only when both EEs were combined. Our results suggest that arid landscapes foster unique communities selected by patches created by each EE(s), solo or in combination. Although the communities' composition differs, they support similar potential functions that may have a role in surviving the harsh arid conditions. The combined effect of the EEs on soil microbial communities is a good example of the hard-to-predict non-additive features of arid ecosystems that merit further research.

A Hotspot in the Romanian Black Sea: Eelgrass Beds Drive Local Biodiversity in Surrounding Bare Sediments

Ecosystem engineers create habitat and provide conditions otherwise unavailable for the development of diverse communities. In marine soft-bottoms in particular, the biodiversity sustained by a matrix of relatively uniform sediments can be drastically enhanced by the presence of ecosystem engineers such as seagrasses. Unfortunately, the influence of seagrass meadows on the diversity of surrounding sediments is often unrecognized in spite of its importance, especially in coastlines exposed to multiple sources of pollution. This study examined composition and diversity associated with a bed of Zostera noltei Hornemann, 1832, and its surrounding bare sediments in a highly urbanized coastal area of the Romanian Black Sea. Dissimilarity levels were quantified and key species driving the differences between uniform (bare) and complex (eelgrass) sedimentary habitats were identified. 48 taxa were collected and counted, with epifaunal and infaunal species each accounting for nearly half of that diversity. Abundance, richness and diversity were strikingly higher in eelgrass-associated sediments, a difference driven primarily by various species of snails, crustaceans, polychaetes and bivalves. Between-habitat differences remained significant even after the removal of epifaunal species and each dataset undergoing strong data transformation. These results suggest that even small eelgrass beds, located in the vicinity of multiple sources of stress, can act as hotspots and make a substantial contribution to local benthic diversity.