Comparative Study of Physical Factors and Microbial Diversity of Four Man-Made Extreme Ecosystems

Environmental changes associated with drying climate are expected to affect functional groups of pro- and microeukaryotes differently in temporary saline waters

Temporary ponds are among the most sensitive aquatic habitats to climate change. Their microbial communities have crucial roles in food webs and biogeochemical cycling, yet how their communities are assembled along environmental gradients is still understudied. This study aimed to reveal the environmental drivers of diversity (OTU-based richness, evenness, and phylogenetic diversity) and community composition from a network of saline temporary ponds, soda pans, in two consecutive spring seasons characterized by contrasting weather conditions. We used DNA-based molecular methods to investigate microbial community composition. We tested the effect of environmental variables on the diversity of prokaryotic (Bacteria, Cyanobacteria) and microeukaryotic functional groups (ciliates, heterotrophic flagellates and nanoflagellates, fungi, phytoplankton) within and across the years. Conductivity and the concentration of total suspended solids and phosphorus were the most important environmental variables affecting diversity patterns in all functional groups. Environmental conditions were harsher and they also had a stronger impact on community composition in the dry spring. Our results imply that these conditions, which are becoming more frequent with climate change, have a negative effect on microbial diversity in temporary saline ponds. This eventually might translate into community-level shifts across trophic groups with changing local conditions with implications for ecosystem functioning.

Molecular characterization of leaf spot caused by Alternaria alternata on buttonwood (Conocarpus erectus L.) and determination of pathogenicity by a novel disease rating scale

The buttonwood (Conocarpus erectus L.) is a mangrove shrub belonging to Combretaceae family. It mostly grows on the shorelines of tropical and subtropicalregions in the world. It was introduced to Lasbela University of Water, Agriculture & Marine Sciences (LUWMS), Uthal, Baluchistan as an ornamental plant as it grows well under harsh, temperate and saline conditions. During a routine survey, typical leaf spot symptoms were observed on the leaves of buttonwood plants. A disease severity scale for alternaria leaf spot of buttonwood was developed for the first time through this study. Disease severity according to the scale was 38.97%. The microscopic characterizations was accomplished for the identification of Alternaria alternata and Koch’s postulates were employed to determine the pathogenicity. For molecular identification, 650 bp internal transcribed spacer (ITS) regions (ITS1, 5.8s and ITS2) were amplified from three representative isolates (LUAWMS1, LUAWMS2 and LUAWMS3) through polymerase chain reaction (PCR). The nucleotide sequences from ITS regions of the isolates were submitted to NCBI with GenBank accession numbers MW585375, MW585376 and MW585377, respectively. The phylogenetic tree of 22 A. alternata isolates was computed and representative isolates exhibited 99.98% genetic similarity with mangroves ecosystem isolates. This study reports the incidence of alternaria leaf spot of buttonwood at LUWMS for the first time. It is suspected that the disease may spread further. Therefore, effective management strategies should be opted to halt the further spread of the disease.