RESUMEN
A twenty-four month long observational study conducted in an Asia's largest brackish water ecosystem, Chilika Lagoon, India, aimed to unravel dissolved organic matter (DOM) dynamics in this tropical brackish water ecosystem. The study assessed the interplay between allochthonous and autochthonous DOM sources during lean and active flow periods based on regional rainfall. Dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) fluxes were analyzed, considering catchment runoff, phytoplankton production, benthic-pelagic interactions, and sea-lagoon exchanges as contributors. Contrary to conventional thinking, the study found autochthonous processes to be more significant than conservative mixing in shaping DOM dynamics. It introduced a novel conceptual model illustrating the multifaceted origins of DOM, encompassing catchment runoff, phytoplankton, benthic-pelagic interactions, bacterial activity, and sea-lagoon exchanges. These findings underscore the importance of holistic management strategies for Chilika Lagoon to preserve its ecological health, given its vital role in global carbon cycling, fisheries, and aquaculture.
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Materia Orgánica Disuelta , Ecosistema , Fitoplancton , Aguas Salinas , AsiaRESUMEN
To understand the impact of seasonal variability on plankton food web composition in tropical coastal waters, samples were collected from three locations along Tuticorin coastal waters during postmonsoon, summer, and northeast (NE) monsoon seasons. During the NE monsoon, the total suspended matter (TSM) and nutrient concentrations were relatively higher, whereas salinity and plankton (phytoplankton and zooplankton) abundances were lower. Cluster analysis also revealed that the NE monsoon formed into a separate cluster because of the lower phytoplankton abundance caused by higher loads of TSM; this arrests light penetration, thereby resulting in a decrease in plankton abundance. The increase in zooplankton biomass coincided with the decrease in diatoms (pâ¯<â¯0.05), and the increase in cyanobacteria may reflect that grazers food choice has a significant impact on the base of the food web composition. The present study states that the phytoplankton biomass was greatly influenced by seasonality and associated changes rather than the huge supply of nutrient loads.
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Cadena Alimentaria , Plancton/fisiología , Agua de Mar/análisis , Animales , Acuicultura , Biomasa , Análisis por Conglomerados , Cianobacterias , Diatomeas , Ambiente , Monitoreo del Ambiente/métodos , India , Residuos Industriales , Fitoplancton/fisiología , Salinidad , Estaciones del Año , Agua de Mar/microbiología , Zooplancton/fisiologíaRESUMEN
Bioavailable dissolved organic carbon (BDOC), nitrogen (BDON) and their degradation rate constants were measured for the Chilika Lagoon, India. Long-term laboratory incubation experiments (90â¯days) were conducted at a constant temperature (25⯰C) to quantify the bioavailable dissolved organic matter (DOM) and the possible degradation rate coefficients. The results showed that 41⯱â¯12% of dissolved organic carbon (DOC) and 47⯱â¯17% of dissolved organic nitrogen (DON) were BDOC and BDON respectively, with their stoichiometry found to be higher than the Redfield ratio. A first order exponential non-linear fitting routine was used to estimate pool sizes. The degradation rate constant (k) for the BDOC varied from 0.127-0.329â¯d-1 and BDON from 0.043-0.306â¯d-1 during the study period. Half-lives of the BDOC and BDON ranged from 2.1-5.4 and 2.2-15.9â¯days, respectively. Overall, the results showed that a fraction of the labile DON was transported from the lagoon to the adjacent coastal sea.
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Carbono/farmacocinética , Nitrógeno/farmacocinética , Aguas Salinas/química , Disponibilidad Biológica , Carbono/análisis , India , Nitrógeno/análisis , Ríos , Aguas Salinas/análisis , Análisis Espacio-Temporal , Clima TropicalRESUMEN
The impact of seasonal coastal upwelling on the dynamics of dissolved inorganic carbon (DIC) and sea-air fluxes of CO2 along the coastal waters of Kochi was investigated during 2015, as a part of Ecosystem Modelling Project. The surface water pCO2 varied from 396 to 630µatm during the study period. Significant inter-seasonal variations were found in the distribution of physico-chemical variables and surface pCO2. An increase of 102.1µatm of pCO2 was noticed over a two-decade period with a rate of 5.3µatmy-1. There was an agreement between the fluxes of CO2 and net ecosystem production (NEP) with respect to the trophic status while NEP was higher than CO2 fluxes by a factor of 3.9. The annual net ecosystem exchange (NEE) was estimated to be 15.02mmolCm-2d-1 indicating that the coastal waters of Kochi are highly heterotrophic in nature.