Integrating resilience with functional ecosystem measures: A novel paradigm for management decisions under multiple-stressor interplay in freshwater ecosystems.

Moving beyond monitoring the state of water quality to understanding how the sensitive ecosystems "respond" to complex interplay of climatic and anthropogenic perturbations, and eventually the mechanisms that underpin alterations leading to transitional shifts is crucial for managing freshwater resources. The multiple disturbance dynamics-a single disturbance as opposed to multiple disturbances for recovery and other atrocities-alter aquatic ecosystem in multiple ways, yet the global models lack representation of key processes and feedbacks, impeding potential management decisions. Here, the procedure we have embarked for what is known about the biogeochemical and ecological functions in freshwaters in context of ecosystem resilience, feedbacks, stressors synergies, and compensatory dynamics, is highly relevant for process-based ecosystem models and for developing a novel paradigm toward potential management decisions. This review advocates the need for a more aggressive approach with improved understanding of changes in key ecosystem processes and mechanistic links thereof, regulating resilience and compensatory dynamics concordant with climate and anthropogenic perturbations across a wide range of spatio-temporal scales. This has relevance contexting climate change and anthropogenic pressures for developing proactive and adaptive management strategies for safeguarding freshwater resources and services they provide.

Review of Indian Allacta Saussure amp; Zehntner, 1895 (Blattodea: Ectobiidae: Pseudophyllodromiinae), with description of three new species.

The known species of Allacta Saussure Zehntner, 1895 in India are reviewed. Three new species, A. jcenpro sp. nov., A. vellimalai sp. nov., and A. kollimalai sp. nov., are described. All are placed under hamifera species group. The new species can be differentiated from other members of hamifera species group by the pronotal and facial markings, the structure of the male genitalia and other morphological characters. Additional reports to A. kalakadensis Prabakaran Senraj 2019 and A. figurata (Walker, 1871) are provided. A key to the known species of Indian Allacta is provided.

River ecosystem resilience risk index: A tool to quantitatively characterize resilience and critical transitions in human-impacted large rivers.

Riverine ecosystems can have tipping points at which the system shifts abruptly to alternate states, although quantitative characterization is extremely difficult. Here we show, through critical analysis of two different reach scale (25 m and 50 m) studies conducted downstream of two point sources, two tributaries (main stem and confluences) and a 630 km segment of the Ganga River, that human-driven benthic hypoxia/anoxia generates positive feedbacks that propels the system towards a contrasting state. Considering three positive feedbacks-denitrification, sediment-P- and metal-release as level determinants and extracellular enzymes (ß-D-glucosidase, protease, alkaline phosphatase and FDAase) as response determinants, we constructed a 'river ecosystem resilience risk index (RERRI)' to quantitatively characterize tipping points in large rivers. The dynamic fit intersect models indicated that the RERRI<4 represents a normal state, 4-18 a transition where recovery is possible, and >18 an overstepped condition where recovery is not possible. The resilience risk index, developed for the first time for a lotic ecosystem, can be a useful tool for understanding the tipping points and for adaptive and transformative management of large rivers.

Parapsilorhynchus alluriensis, a new species of cyprinid fish (Teleostei: Cyprinidae) from the Eastern Ghats, of India.

A new species of cyprinid fish, Parapsilorhynchus alluriensis, is described from the Alluri Hills of Andhra Pradesh State, India. It is distinguished from its congeners by the combination of the following characters: A poorly-developed callous pad present behind lower lip; head deep (depth at occiput 47.3-72.3% head length, HL); body stout and deep (depth at dorsal fin origin 17.3-21.7 % standard length, SL); gape width 27.3-32.8% HL; inter-orbital space 33.9-43.2% HL; lower lip rounded; mouth opening situated very close to the anterior tip of snout; upper lip concealed by a poorly-developed rostral fold which is slightly fringed; minute papillae on rostral fold; 3 simple pectoral-fin rays; 33-34 lateral-line scales. A partial phylogeny based on the DNA Barcode COI gene suggests a sister-group relationship between the new species and P. prateri. Till date, the genus consists of four species from the Western Ghats, three from the Eastern Ghats, including the species described herein totaling it to seven from the peninsular India.

Benthic hypoxia in anthropogenically-impacted rivers provides positive feedback enhancing the level of bioavailable metals at sediment-water interface.

We investigated the effect of hypoxic-anoxic range of dissolved oxygen (DO) on metal release/bioavailability at sediment-water interface (SWI) in the Ganga River. Here, we consider eight sites in the main river stem along 518 km; sixty sites downstream two point sources and two tributary confluences covering 630 km; and an incubation experiment to verify these results. We found higher concentrations of metals and bioavailable fractions at SWI at two locations of main stem and up to 700 m, 1000 m, 400 m and 500 m downstream Assi drain, Wazidpur drain, Ramganga confluence and Varuna confluence respectively where DO at SWI (DOsw) was <2.0 mgL-1. The incubation experiment did show higher levels of metal- and P-release and bioavailability under anoxic-hypoxic range of DO. The risk assessment code and eutrophication index indicated high to very high risks of contaminated river sediment and water to aquatic environment at sites with hypoxic-anoxic range of DOsw. Further, the principal component analyses separated metals and bioavailable fractions opposite to FDAase indicating greater risk at these locations. The study, which forms the first report on benthic hypoxia/anoxia-driven metal release, potential bioavailability and risk to the Ganga River ecosystem will help understanding how human-driven perturbations influence geochemical cycling of metals and ecosystem responses in large rivers.

Hypoxia and associated feedbacks at sediment-water interface as an early warning signal of resilience shift in an anthropogenically impacted river.

Multiple human perturbations in the large rivers often cause habitat fragmentation creating patches of unpredictable structural and functional attributes. The resilience has been largely neglected in riverine studies, despite its pivotal importance in ecosystem recovery. We expect that a shift in sub-habitat conditions along a river transect subjected to frequent oxygen fluctuation and release of carbon, nutrients and other substances generate feedbacks to overstep the resilience and constrain ecosystem recovery. Because dissolved oxygen (DO) plays a regulatory role in ecosystem structure and functioning and feedbacks the denitrification and sediment-P release, we consider the mechanistic links among DOsw, denitrification and sediment-P release to identify resilience level and to construct a dynamic fit model to uncover the level of resilience and critical transitions in the river. We investigated 180 sites downstream two point sources and two tributaries, each with a 1.4 km river segment, covering 630 km length of the Ganga River. The dynamic fit model intersecting the DOsw at <1.5 mg L-1, sediment-P release >7.03 mg m-2 d-1 and denitrification rate >1.0 mg N m-2 hr-1 at 25 m reach downstream point sources indicated a threat to natural/self-recovery of the Ganga River. The non-metric multidimensional scaling (NMDS) and neighbor-joining analysis indicated that locations up to 700 m downstream Wazidpur drain have overstepped the ecosystem resilience. We found almost similar results downstream Assi drain and study confluences. Our explicit incorporation of DOsw, sediment-P release, and denitrification in an organized framework provides key insights to detect resilience and critical transitions in an anthropogenically impacted river ecosystem. Given the importance of the Ganga River for national water security and supply across several major states in India, research on the factors and status of resilience underpinning its recovery should be high on our national agenda.

An ecological response index for simultaneous prediction of eutrophication and metal pollution in large rivers.

The ecological responses of riverine ecosystems are strongly influenced by anthropogenic perturbations. However, high-resolution quantitative shifts in the 'ecosystem responses' to multiple human pressures in riverine ecosystems are not well understood. Given that, in most of the anthropogenically impacted rivers, eutrophy and metal pollution occur simultaneously, we explored FDAase activity, microbial quotient, and a sum of six heavy metals in an empirical relationship to develop an 'ecological response index' (ERI). The FDAase, a measure of fluorescein diacetate hydrolytic activity, and microbial quotient, the proportion of microbial biomass-C to the total organic carbon (Cmic/TOC) were used to address 'ecosystem responses' to C-eutrophy and metal pollution. We analyzed 1404 water samples and 2808 sediment samples collected from the land-water interface (LWI) and riverbed sediment (50 m reach) of 24 sites along a 528 km main stem and from 30 sites downstream two point sources of the Ganga River. The index was compare to Carlson's trophic state index (TSI) to quantify eutrophy and Håkanson's risk index (RI) and modified ecological risk index (MRI) for metal pollution. The ERI showed strong correlation with TSI (R2 = 0.70-0.97; p < 0.001), RI (R2 = 0.76-0.94; p < 0.001) and MRI (R2 = 0.76-0.96; p < 0.001). The ERI developed here is the first 'response index' against multiple human pressures, able to quantitatively predict C-eutrophication and metal pollution simultaneously in large rivers.

Investigations on peculiarities of land-water interface and its use as a stable testbed for accurately predicting changes in ecosystem responses to human perturbations: A sub-watershed scale study with the Ganga River.

In lotic systems, the hydrologic forcing together with structural and functional complexities make it difficult to predict how the river ecosystem will respond to human perturbations. We conducted two sets of studies selecting two segments; a 518 km main river stem, and two point source trajectories at the Ganga River during summer low flow of three consecutive years (2016-2018). The objective was to test if the land-water interface (LWI) of the river serves as a stable testbed for predicting human control on water quality and ecosystem responses. Samples were collected from LWI and complementary locations (50 m reach) from 8 selected sites of the main stem and 15 equidistant locations downstream each point source. Concentrations of carbon, nutrients and heavy metals at LWI varied in concordance with their concentrations in river water and riverbed sediment. Also, the microbial biomass (C, N, and P), activities and extracellular enzymes at LWI showed synchrony with their respective counterparts in riverbed sediment. We found strong positive correlations (p < 0.05-0.001) between these variables at LWI and their counterparts in water/riverbed sediment along the main stem and point source downstream. Our study establishes the credential of LWI for more accurately predicting changes in ecosystem responses to human perturbations. The study will facilitate accurate upscaling intercomparability across varied environmental control on the headwater streams-to-estuaries continuum.

Anthropogenically enhanced sediment oxygen demand creates mosaic of oxygen deficient zones in the Ganga River: Implications for river health.

Dissolved oxygen (DO) plays a major role in sustaining aquatic communities; its concentration and regulatory determinants are considered a key node predicting eutrophy, ecosystem health, and biogeochemical feedbacks. Here we report the status of dissolved oxygen deficit (DOD; hypoxia), and its mechanistic links with sediment oxygen demand (SOD) in the Ganga River. We conducted two independent but interlinked studies during summer low flows of three consecutive years (2016-2018) considering: 1) a 518 km middle segment of the Ganga River between Kanpur upstream and Varanasi downstream; and 2) trajectory analyses downstream two point sources, one flushing industrial effluents (Wazidpur drain) and the other with urban sewage (Assi drain). The concentration of DO at sediment-water interface (DOsw) did appear < 2.0 mg L-1 (hypoxia) at Jjmu; and up to 600 m and 800 m downstream Assi and Wazidpur drain respectively. The DOD at sediment-water interface (DODsw) was highest at Jjmu and did not show a significant decrease up to 300 m downstream to point sources. The SOD which varied between 2.03 and 13.16 (main river stem); 4.39 and 16.81 (Wazidpur drain); and between 2.00 and 13.50 g O2 m-2 d-1 (Assi drain), was found to be a major contributor of DOD. Principal component analysis (PCA) and non-metric multi-dimensional scaling (NMDS) separated DO and alkaline phosphatase (AP) opposite to oxygen-consuming processes and sediment-P release. Using a dynamic fit model, we tested the dependence of sediment-P release on DOsw and DODsw. A large increase in the sediment-P release with increasing DODsw and decreasing DOsw indicated that the system may compromise its resilience in long-term future in terms of self-fertilization and P-eutrophy if the similar magnitude of anthropogenic pressure is continued. The study advances our understanding towards DOD associated habitat fragmentation, ecosystem resilience and niche opportunities useful for recovery and management of the Ganga River.

Impact of heavy metal on activity of some microbial enzymes in the riverbed sediments: Ecotoxicological implications in the Ganga River (India).

We studied the extracellular enzyme activity (EEA) in the riverbed sediment along a 518km gradient of the Ganga River receiving carbon and nutrient load from varied human sources. Also, we tested, together with substrate-driven stimulation, if the heavy metal accumulated in the sediment inhibits enzyme activities. Because pristine values are not available, we considered Dev Prayag, a least polluted site located 624km upstream to main study stretch, as a reference site. There were distinct increases in enzyme activities in the sediment along the study gradient from Dev Prayag, however, between-site differences were in concordance with sediment carbon(C), nitrogen (N) and phosphorus (P). Fluorescein diacetate hydrolysis (FDAase), ß-glucosidase (Glu) and protease activities showed positive correlation with C, N and P while alkaline phosphatase was found negatively correlated with P. Enzyme activities were found negatively correlated with heavy metal, although ecological risk index (ERi) varied with site and metal species. Dynamic fit curves showed significant positive correlation between heavy metal and microbial metabolic quotient (qCO2) indicating a decrease in microbial activity in response to increasing heavy metal concentrations. This study forms the first report linking microbial enzyme activities to regional scale sediment heavy metal accumulation in the Ganga River, suggests that the microbial enzyme activities in the riverbed sediment were well associated with the proportion of C, N and P and appeared to be a sensitive indicator of C, N and P accumulation in the river. Heavy metal accumulated in the sediment inhibits enzyme activities, although C rich sediment showed relatively low toxicity due probably to reduced bioavailability of the metal. The study has relevance from ecotoxicological as well as from biomonitoring perspectives.

The protein inhibitor of nNOS (PIN/DLC1/LC8) binding does not inhibit the NADPH-dependent heme reduction in nNOS, a key step in NO synthesis.

The neuronal nitric oxide synthase (nNOS) is an essential enzyme involved in the synthesis of nitric oxide (NO), a potent neurotransmitter. Although previous studies have indicated that the dynein light chain 1 (DLC1) binding to nNOS could inhibit the NO synthesis, the claim is challenged by contradicting reports. Thus, the mechanism of nNOS regulation remained unclear. nNOS has a heme-bearing, Cytochrome P450 core, and the functional enzyme is a dimer. The electron flow from NADPH to Flavin, and finally to the heme of the paired nNOS subunit within a dimer, is facilitated upon calmodulin (CaM) binding. Here, we show that DLC1 binding to nNOS-CaM complex does not affect the electron transport from the reductase to the oxygenase domain. Therefore, it cannot inhibit the rate of NADPH-dependent heme reduction in nNOS, which results in l-Arginine oxidation. Also, the NO release activity does not decrease with increasing DLC1 concentration in the reaction mix, which further confirmed that DLC1 does not inhibit nNOS activity. These findings suggest that the DLC1 binding may have other implications for the nNOS function in the cell.

Molecular view of an electron transfer process essential for iron-sulfur protein biogenesis.

Biogenesis of iron-sulfur cluster proteins is a highly regulated process that requires complex protein machineries. In the cytosolic iron-sulfur protein assembly machinery, two human key proteins--NADPH-dependent diflavin oxidoreductase 1 (Ndor1) and anamorsin--form a stable complex in vivo that was proposed to provide electrons for assembling cytosolic iron-sulfur cluster proteins. The Ndor1-anamorsin interaction was also suggested to be implicated in the regulation of cell survival/death mechanisms. In the present work we unravel the molecular basis of recognition between Ndor1 and anamorsin and of the electron transfer process. This is based on the structural characterization of the two partner proteins, the investigation of the electron transfer process, and the identification of those protein regions involved in complex formation and those involved in electron transfer. We found that an unstructured region of anamorsin is essential for the formation of a specific and stable protein complex with Ndor1, whereas the C-terminal region of anamorsin, containing the [2Fe-2S] redox center, transiently interacts through complementary charged residues with the FMN-binding site region of Ndor1 to perform electron transfer. Our results propose a molecular model of the electron transfer process that is crucial for understanding the functional role of this interaction in human cells.

Structural characterization of CHCHD5 and CHCHD7: two atypical human twin CX9C proteins.

Twin CX(9)C proteins constitute a large protein family among all eukaryotes; are putative substrates of the mitochondrial Mia40-dependent import machinery; contain a coiled coil-helix-coiled coil-helix (CHCH) fold stabilized by two disulfide bonds as exemplified by three structures available for this family. However, they considerably differ at the primary sequence level and this prevents an accurate prediction of their structural models. With the aim of expanding structural information on CHCH proteins, here we structurally characterized human CHCHD5 and CHCHD7. While CHCHD5 has two weakly interacting CHCH domains which sample a range of limited conformations as a consequence of hydrophobic interactions, CHCHD7 has a third helix hydrophobically interacting with an extension of helix α2, which is part of the CHCH domain. Upon reduction of the disulfide bonds both proteins become unstructured exposing hydrophobic patches, with the result of protein aggregation/precipitation. These results suggest a model where the molecular interactions guiding the protein recognition between Mia40 and the disulfide-reduced CHCHD5 and CHCHD7 substrates occurs in vivo when the latter proteins are partially embedded in the protein import pore of the outer membrane of mitochondria.

Copper exposure effects on yeast mitochondrial proteome.

Mitochondria play an important role on the entire cellular copper homeostatic mechanisms. Alteration of cellular copper levels may thus influence mitochondrial proteome and its investigation represents an important contribution to the general understanding of copper-related cellular effects. In these study we have performed an organelle targeted proteomic investigation focusing our attention on the effect of non-lethal 1mM copper concentration on Saccharomyces cerevisiae mitochondrial proteome. Functional copper effects on yeast mitochondrial proteome were evaluated by using both 2D electrophoresis (2-DE) and liquid chromatography coupled with tandem mass spectrometry. Proteomic data have been then analyzed by different unsupervised meta-analysis approaches that highlight the impairment of mitochondrial functions and the activation of oxidative stress response. Interestingly, our data have shown that stress response generated by 1mM copper treatment determines the activation of S. cerevisiae survival pathway. To investigate these findings we have treated yeast cells responsiveness to copper with hydrogen peroxide and observed a protective role of this metal. These results are suggestive of a copper role in the protection from oxidative stress possibly due to the activation of mechanisms involved in cellular survival and growth.