Organic Nutrient Accumulation Research Articles

The key to dinoflagellate (Noctiluca scintillans) blooming and outcompeting diatoms in winter off Pakistan, northern Arabian Sea

The Arabian Sea is prone to large-scale algal blooms during winter monsoon annually. However, it is unclear why dinoflagellate, especially Noctiluca scintillans, replaced diatoms as the main bloom species. Based on in situ, remote sensing and numerical-model data off Pakistan, we found a stratified water with less salty, suitable temperature (~24 °C) and low-light conditions at the subsurface, as well as the organic nutrient accumulation and silicate limitation, were crucial for the growth of N. scintillans and outcompeting diatoms. The superposition of cyclonic eddy promoted N. scintillans pumping to surface and forming large-scale bloom. Subsequently, the shading effect of surface bloom caused the disappearance of subsurface chlorophyll maximum layer. This result suggests that the combined effects of nutrient structure and hydrodynamics play an important role in the prevalence of N. scintillans.

Evaluation of nutrient stoichiometric relationships among ecosystem compartments of a subtropical treatment wetland. Do we have \u201cRedfield wetlands\u201d?

BackgroundEvaluation of carbon (C), nitrogen (N), and phosphorus (P) ratios in aquatic and terrestrial ecosystems can advance our understanding of biological processes, nutrient cycling, and the fate of organic matter (OM) in these ecosystems. Eutrophication of aquatic ecosystems can change the accumulation and decomposition of OM which can alter biogeochemical cycling and alter the base of the aquatic food web. This study investigated nutrient stoichiometry within and among wetland ecosystem compartments (i.e., water column, flocculent, soil, and aboveground vegetation biomass) of two subtropical treatment wetlands with distinct vegetation communities. Two flow-ways (FWs) within the network of Everglades Stormwater Treatment Areas in south Florida (USA) were selected for this study. We evaluated nutrient stoichiometry of these to understand biogeochemical cycling and controls of nutrient removal in a treatment wetland within an ecological stoichiometry context.ResultsThis study demonstrates that C, N, and P stoichiometry can be highly variable among ecosystem compartments and between FWs. Power law slopes of C, N, and P within surface water floc, soil, and vegetation were significantly different between and along FWs.ConclusionsAssessment of wetland nutrient stoichiometry between and within ecosystem compartments suggests unconstrained stoichiometry related to P that conforms with the notion of P limitation in the ecosystem. Differences in N:P ratios between floc and soil suggest different pathways of organic nutrient accumulation and retention between FWs. Surface nutrient stoichiometry was highly variable and decoupled (or close to decoupled as indicated by < 25% explained variation between parameters), in particular with respect to P. We hypothesize that decoupling may be the imprint of variability in inflow nutrient stoichiometry. However, despite active biogeochemical cycles that could act to restore nutrient stoichiometry along the FW, there was little evidence that such balancing occurred, as the degree of stochiometric decoupling in the water column did change with distance downstream. This information is only the beginning of a larger journey to understand stoichiometric processes within wetland ecosystems and how they relate to ecosystem function.