Variability in the phytoplankton community of Kavaratti reef ecosystem (northern Indian Ocean) during peak and waning periods of El Niño 2016

El Niño, an interannual climate event characterized by elevated oceanic temperature, is a prime threat for coral reef ecosystems worldwide, owing to their thermal threshold sensitivity. Phytoplankton plays a crucial role in the sustenance of reef trophodynamics. The cell size of the phytoplankton forms the “master morphological trait” with implications for growth, resource acquisition, and adaptability to nutrients. In the context of a strong El Niño prediction for 2015–2016, the present study was undertaken to evaluate the variations in the size-structured phytoplankton of Kavaratti reef waters, a major coral atoll along the southeast coast of India. The present study witnessed a remarkable change in the physicochemical environment of the reef water and massive coral bleaching with the progression of El Niño 2015–2016 from its peak to waning phase. The fluctuations observed in sea surface temperature, pH, and nutrient concentration of the reef water with the El Niño progression resulted in a remarkable shift in phytoplankton size structure, abundance, and community composition of the reef waters. Though low nutrient concentration of the waning phase resulted in lower phytoplankton biomass and abundance, the diazotroph Trichodesmium erythraeum predominated the reef waters, owing to its capability of the atmospheric nitrogen fixation and dissolved organic phosphate utilization.     

Short-term variability of water quality and its implications on phytoplankton production in a tropical estuary (Cochin backwaters—India)

Changes in the phytoplankton biomass (chlorophyll a), production rate, and species composition were studied over two seasons using the time series measurements in the northern limb of the Cochin estuary in relation to the prevailing hydrological conditions. The present study showed the significant seasonal variation in water temperature (F = 69.4, P < 0.01), salinity (F = 341.93, P < 0.01), dissolved inorganic phosphorous (F = 17.71, P < 0.01), and silica (F = 898.1, P < 0.01) compared to nitrogen (F = 1.646, P > 0.05). The uneven input of ammonia (3.4–224.8 μM) from upstream (Periyar River) leads to the inconsistency in the N/P ratio (range 6.8–262). A distinct seasonality was observed in Si/N (F = 382.9, P < 0.01) and Si/P (F = 290.3, P < 0.01) ratios compared to the N/P ratio (F = 1.646, P > 0.05). The substantial increase in chlorophyll a (average, 34.8 ± 10 mg m^???3) and primary production (average, 1,304 ± 694 mg C m^???3 day^???1) indicated the mesotrophic condition of the study area during the premonsoon (PRM) and it was attributed to the large increase in the population of nanoplankton (size < 20 μ ) such as Skeletonema costatum, Thalassiosira subtilis, Nitzschia closterium, and Navicula directa. In contrast, during the post monsoon (PM), low chlorophyll a concentration (average, 9.3 ± 9.2 mg m^???3) and primary production (average, 124 ± 219 mg C m^???3 day^???1) showed heterotrophic condition. It can be stated that favorable environmental conditions (optimum nutrients and light intensity) prevailing during the PRM have enhanced the abundance of the nanoplankton community in the estuary, whereas during the PM, the light limitation due to high turbidity can reduce the nanoplankton growth and abundance, even though high nutrient level exists.     

Pollution control and inputs to production

The primary concern of this paper is to identify the inputs required for air, water, and solid waste pollution abatement in the United States. Industry level data on pollution abatement expenditures in 1976 are decomposed into expenditures on various intermediate inputs and on two primary inputs—labor and capital. The 1971 input-output table is adjusted to reflect the input needs of pollution abatement technology. This revised direct input coefficients matrix is used to derive the gross output and primary input requirements of the 1971 final bill of goods.     

Leaf surface chemicals stimulating oviposition byPieris rapae (Lepidoptera: Pieridae) on cabbage

Summary The chemical stimulation of oviposition byPieris rapae on cabbage was investigated by leaf washing and extraction. Isolation of the stimulant by various chromatographic techniques was monitored by a bioassay using Sieva bean as a surrogate host plant. Cold water, chloroform, or chloroform followed by cold water washes failed to release the stimulant from leaf surfaces. Boiling water or chloroform followed by methanol was required. The most active stimulatory compound was identified as 3-indolylmethyl glucosinolate (glucobrassicin). Other glucosinolates were identified as sinigrin, which was only slightly active, and glucoiberin, which was completely inactive as a stimulant. The significance of the selective response ofP. rapae andP. brassicae to different glucosinolates and the implications of the binding of polar allelochemicals to leaf surfaces is discussed with respect to host utilization and perception mechanisms of pierids.     

Oviposition stimulants for the pipevine swallowtail butterfly,Battus philenor (Papilionidae), from anAristolochia host plant: Synergism between inositols,aristolochic acids and a monogalactosyl diglyceride

Aristolochia macrophylla (Lam.) is a major host of the pipevine swallowtail butterfly,Battus philenor (L.), in the eastern United States. The female butterflies use a synergistic mixture of inositols, acids and a lipid as oviposition cues in recognizing this plant on contact. The acids and lipid, all isolated from the Et₂O-CHCl₃ fraction of an alcoholic extract of fresh foliage, were identified as aristolochic acid I (1), aristolochic acid II (2) and 1,2-[di(9Z,12Z,15Z)-octadeca-9, 12, 15-trienoyl]-3-galactosyl-sn-glycerol (3). Identifications were facilitated by UV, MS (EI and FAB) and NMR (1D and 2D) spectral techniques and by analysis of the hydrolysis products of 3. The active inositols were identified as D-(+)-pinitol, reported previously, and sequoyitol. Though this is apparently the first report of oviposition responses to a diacyl glycerol glycoside by a phytophagous insect, responses to aristolochic acids and sequoyitol have been reported previously for anAristolochia-feeding swallowtail of a different genus in Japan. This indicates substantial evolutionary conservatism in chemical oviposition cues within the tribe Troidini.     

Effects of population and population pressure on forest resources and their conservation: a modeling study

In this paper, a nonlinear mathematical model is proposed and analyzed to study the depletion of forest resources caused by population and the corresponding population pressure. It is assumed that the cumulative density of forest resources and the density of populations follow logistic models with prey–predator type nonlinear interaction terms. It is considered that the carrying capacity of forest resources decreases by population pressure, the main focus of this paper. A conservation model is also proposed to control the population pressure by providing some economic incentives to people, the amount of which is assumed to be proportional to the population pressure. The model is analyzed by using stability theory of differential equations and numerical simulation. The model analysis shows that as the density of population or population pressure increases, the cumulative density of forest resources decreases, and the resources may become extinct if the population pressure becomes too large. It is also noted that by controlling the population pressure, using some economic incentives, the density of forest resources can be maintained at an equilibrium level, which is population density dependent. The simulation analysis of the model confirms analytical results.     

Improving the redox performance of photocatalytic materials by cascade-type charge transfer: a review

Environmental and energy crises are a major threat to the sustainable growth of the human society, calling for greener technologies such as photocatalysis. Photocatalysis is a solar-driven approach that converts photon energy into chemical energy, yet the conversion efficacy of classical photocatalysis is usually restricted and controlled by the charge carrier’s separation and migration. Enhanced conversion requires suppressed recombination rate and superior redox abilities. From this aspect, the manipulation of heterojunction allows to overcome the drawback of classical photocatalysis. The cascade mechanism follows a dual direct charge migration route, resulting in enhanced redox abilities and efficient mineralization of pollutants. Here, we review photocatalytic material aspects in improving redox ability by cascade charge transfer. We describe the mechanisms and applications of three cascade systems: two type-II cascade systems, mediator-based cascade systems, and dual direct Z-scheme. We highlight the superiority of the direct dual cascade route with a prolonged lifetime of carriers, higher quantum yield, and enhanced redox abilities. Applications to carbon dioxide reduction, hydrogen production by water splitting and pollutant degradation are discussed.

     

Role of environmental lead in the occurrence of anemia in Indian children: a systematic review and meta-analysis

Environmental Science and Pollution Research - Exposure to lead among children, as well as adults, is a major global health issue. With diverse routes of exposure (e.g., food, air, and water)...