Estuaries are complex systems where environmental fluctuations occur over distinct timescales due to local meteorological and large-scale climatic factors. Consequently, studies with low temporal resolution and taxonomic coverage may fail to detect isotopic variations in basal sources, providing biased interpretations of isotope mixing models. We investigated the seasonal and El Niño Southern Oscillation (ENSO)-driven interannual variations in δ13C, δ15N and C:N values among distinct basal sources and their implications for mixing models interpretation in a subtropical estuary. δ13C variations among sources differed in their magnitude and timescales, being large enough to confound source-specific values. Macroalgae and POM δ13C varied seasonally, whereas ENSO effects prevailed for C3 and C4 salt marsh plants, highlighting the contrasting influence of local versus remote environmental drivers on short- and long-lived primary producers, respectively. Peaks of δ15N were detected for all sources during short-term anthropogenic nutrient inputs. Isotope mixing model comparisons showed that overlooking isotopic variations in basal sources under distinct ENSO conditions can cause misinterpretation of local trophic interactions and nutrient cycling. The present study contributes to design appropriate sampling delineations in highly variable aquatic environments, emphasizing the importance of comprehensive, long-term monitoring of estuarine primary producers to encompass environmental drivers of stable isotopic variations.
相似文献Cultivation of spirulina at commercial-scales relies on analytical grade–based media, which are expensive and so are the product.
PurposeThis study assessed the biomass, proximate composition, and other useful compounds in Spirulina (Arthrospira fusiformis) produced with a cost-effective culture medium (LCMA), and the results were compared with those from a standard Zarrouk medium–grown spirulina.
MethodsThe LCMA medium was formulated by using a commercial NPK10-20-20 fertilizer as a source of the three major nutrients for spirulina growth, and other three ingredients from Zarrouk medium. The experiment was conducted for 28 days in the glass aquaria under indoor conditions. Standard analytical methods were applied for the determination of proximate composition, chlorophyll, minerals, and vitamins in the spirulina biomass.
ResultThe LCMA medium showed the best growth conditions by accumulating higher chlorophyll content (0.99 ± 0.02%) and dry weight (0.75 ± 0.01 g/100 ml) as well as attaining higher optical density (2.06 at day 15) earlier than the Zarrouk medium. The results of the proximate analysis for spirulina cultured in the LCMA medium were of good quality, with the protein contributing more than 50% of its dry matter. It was further noticed that the LCMA was an ideal medium for optimization of vitamins and some minerals since it recorded a significant amount of most of the analyzed vitamins together with the minerals sodium and potassium compared with the Zarrouk medium.
ConclusionIt is suggested that LCMA medium could be used as the alternative and cheap medium for maximization of biomass and production of useful biochemical compounds in spirulina species.
相似文献