Seasonal occurrence of anoxygenic photosynthesis in Tillari and Selaulim reservoirs, Western India

Abstract

<jats:p>Abstract. Phytoplankton and bacterial pigment compositions were determined by high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) in two freshwater reservoirs (Tillari Dam and Selaulim Dam), which are located at the foothills of the Western Ghats in India. These reservoirs experience anoxia in the hypolimnion during summer. Water samples were collected from both reservoirs during anoxic periods while one of them (Tillari Reservoir) was also sampled in winter, when convective mixing results in well-oxygenated conditions throughout the water column. During the period of anoxia (summer), bacteriochlorophyll (BChl) e isomers and isorenieratene, characteristic of brown sulfur bacteria, were dominant in the anoxic (sulfidic) layer of the Tillari Reservoir under low light intensities. The winter observations showed the dominance of small cells of Chlorophyll b-containing green algae and cyanobacteria, with minor presence of fucoxanthin-containing diatoms and peridinin-containing dinoflagellates. Using total BChl e concentration observed in June, the standing stock of brown sulfur bacteria carbon in the anoxic compartment of Tillari Reservoir was estimated to be 2.27 gC m−2, which is much higher than the similar estimate for carbon derived from oxygenic photosynthesis (0.82 gC m−2. The Selaulim Reservoir also displayed similar characteristics with the presence of BChl e isomers and isorenieratene in the anoxic hypolimnion during summer. Although sulfidic conditions prevailed in the water column below the thermocline, the occurrence of photo-autotrophic bacteria was restricted only to mid-depths (maximal concentration of BChl e isomers was detected at 0.2% of the surface incident light). This shows that the vertical distribution of photo-autotrophic sulfur bacteria is primarily controlled by light penetration in the water column where the presence of H2S provides a suitable biogeochemical environment for them to flourish.</jats:p>

Carotenoid biomarkers in Namibian shelf sediments: Anoxygenic photosynthesis during sulfide eruptions in the Benguela Upwelling System

“…These remnants of algal and cyanobacterial pigments were the only compounds that could be positively identified in the analyses of tetrapyrroles and intact carotenoids. The analyses of pigments in the reference microbial mat, sediment, and biomass samples verified the effectiveness of the analytical protocol, which was based on previously published methods (78)(79)(80) and shown to be able to identify bacterial and algal carotenoids, as well as chlorophylls and a variety of their degradation products. Thus, HPLC-MS analysis of intact pigments and their polar degradation products in the free (i.e., nonsulfur-bound) lipid extracts revealed only pigments diagnostic for oxygenic photosynthesis in the BUS, while failing to provide evidence of anoxygenic photosynthetic GSB or PSB.…”

Unexpectedly high bacteriochlorophyll a concentrations in neotropical tank bromeliads

“…The diversity of their lifestyles allows APB to occupy a broad range of environments (e.g., Csotonyi et al ., ; Medová et al ., ; Atamna‐Ismaeel et al ., ). Owing to their presence in both oxic and anoxic layers of marine and inland waters (e.g., Kolber et al ., ; Koblížek et al ., ; Mašín et al ., ; Kurian et al ., ), APB are expected to have a significant impact on the overall ecology of these systems. However, their contribution to the global carbon and energy flows of aquatic systems is often limited compared to that of oxygenic photosynthesis because (i) APB form dense accumulations only in peculiar sulfidic layers (Overmann and Garcia‐Pichel, ), (ii) the BChl concentrations are usually low in ocean (e.g., from 0.5 to 50 ng l −1 ; Jiao et al ., ) and lake (e.g., from 0 to 40 ng l −1 , Mašín et al ., ) surface waters, and (iii) except in discrete layers of aquatic systems (Overmann et al ., ), the contribution of BChl to total photosynthetic pigments is low (from 0.1 to 10%; Goericke, ; Koblížek et al ., ; Jiao et al ., ; Fauteux et al ., ).…”

Variations of Colored Dissolved Organic Matter in the Mandovi Estuary, Goa, During Spring Inter-Monsoon: A Comparison With COVID-19 Outbreak Imposed Lockdown Period

“…Phytoplankton pigments were analyzed by filtering 1 L of water onto GF/F filters (0.7 µm) under dark and cold conditions. The samples were extracted in 3 mL methanol and analyzed on a HPLC 1200 series (Agilent Technologies) as detailed in Kurian et al (2012). Chlorophyll a is usually used as a proxy for phytoplankton biomass, while accessory pigments are specific to phytoplankton groups and give information on the community composition (Gieskes et al, 1988;Mackey et al, 1996;Jeffrey et al, 1997;Prézelin et al, 2000).…”