Biology subjects

Osborne, T. Z.

Publications and source records attributed to Osborne, T. Z..

3 recordsLinked to original sources

bioRxiv2017

Stoichiometric relationships amongst ecosystem compartments of a subtropical treatment wetland

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 aquatic ecosystems. Eutrophication of aquatic ecosystems can disrupt the accumulation and decomposition of OM which serves as the base of the aquatic food web, and is central to the effectiveness of a treatment wetland. This study investigated nutrient stoichiometry within and between wetland ecosystem compartments (i.e. water column, vegetation, flocculent and soil) of two treatment flow-ways (FWs) in the Everglades Stormwater Treatment Areas located in south Florida (USA). These FWs include an emergent aquatic vegetation cell dominated by Typha spp.(cattail) and a submerged aquatic vegetation cell composed of species such as Chara spp. (muskgrass) and Potamogeton spp. (pondweed). The primary objective of this evaluation was to determine if nutrient stoichiometry is consistent within and between ecosystems and compartments to understand biogeochemical cycling and controls of nutrient removal within a treatment wetland ecosystem.\n\nResultsThis study demonstrates that C, N, and P stoichiometry can be highly variable among ecosystem compartments and between differing wetland ecosystems. Generally, total P declined along the length of each treatment FW in all ecosystem compartments, whereas trends in total N and C trends were more variable. These changes in C and nutrient concentrations result in variable nutrient stoichiometry along treatment FWs signaling potential changes in absolute and relative nutrient availability and biogeochemical processes.\n\nConclusionsAssessment of wetland nutrient stoichiometry between and within ecosystem compartments suggest decoupling of C:N:P relationships likely as a consequence of differential external nutrient supply, differences in primary producer communities and differential decomposition of organic matter. However, stoichiometry varies often monotonous along the flow paths, likely exhibiting a response to nutrient loading. Differences in C:N:P ratios in primary producers, light availability, microbial immobilization in the early stage of decomposition as well as nutrient mining during decomposition of OM are likely feedback mechanisms that lead to deviations from fixed stoichiometry, which in turn may have considerable influence on nutrient removal rates. This information could be used to further understand water treatment performance with respect to stoichiometric processes and OM decomposition.

ecology↗

bioRxiv2017

Carbon pool trends and dynamics within a subtropical peatland during long-term restoration

BackgroundThe Florida Everglades has undergone significant ecological change spanning the continuum of disturbance to restoration. While the restoration effort is not complete and the ecosystem continues to experience short duration perturbations, a better understanding of long-term C dynamics of the Everglades is needed to facilitate new restoration efforts. This study evaluated temporal trends of different aquatic carbon (C) pools of the northern Everglades Protection Area over a 20-year period to gauge historic C cycling patterns. Dissolved inorganic C (DIC), dissolved organic C (DOC), particulate organic C (POC), and surface water carbon dioxide (pCO2(aq)) were investigated between May 1, 1994 and April 30, 2015.\n\nResultsAnnual mean concentrations of DIC, DOC, POC, and pCO2(aq) significantly decreased through time or remained constant across the Water Conservation Areas (WCAs). Overall, the magnitude of the different C pools in the water column significantly differed between regions. Outgassing of CO2 was dynamic across the Everglades ranging from 420 to 2001 kg CO2 yr-1. Overall the historic trend in CO2 flux from the marsh declined across our study area while pCO2(aq) largely remained somewhat constant with the exception of Water Conservation Area 2 which experienced significant declines in pCO2(aq). Particulate OC concentrations were consistent between WCAs, but a significantly decreasing trend in annual POC concentrations were observed.\n\nConclusionsHydrologic condition and nutrient inputs significantly influenced the balance, speciation, and flux of C pools across WCAs suggesting a subsidy-stress response in C dynamics relative to landscape scale responses in nutrient availability. The interplay between nutrient inputs and hydrologic condition exert a driving force on the balance between DIC and DOC production via the metabolism of organic matter which forms the base of the aquatic foodweb. Along the restoration trajectory as water quality and hydrology continues to improve it is expected that C pools will respond accordingly.

ecology↗

bioRxiv2017

From lake to estuary, the tale of two waters. A study of aquatic continuum biogeochemistry

The balance of fresh and saline water is essential to estuarine ecosystem function. Along the fresh-brackish-saline water gradient within the C-43 canal/Caloosahatchee River estuary (CRE) the quantity, timing and distribution of water and associated water quality significantly influences ecosystem function. Long-term trends of water quality and quantity were assessed from Lake Okeechobee to the CRE between May 1978 to April 2016. Significant changes to monthly flow volumes were detected between the lake and the estuary which correspond to changes in upstream management. and climatic events. Across the 37-year period total phosphorus (TP) flow-weighted mean (FWM) concentration significantly increased at the lake, meanwhile total nitrogen (TN) FMW concentrations significantly declined at both the lake and estuary headwaters. Between May 1999 and April 2016, TN, TP and total organic carbon (TOC), ortho-P and ammonium conditions were assessed within the estuary at several monitoring locations. Generally nutrient concentrations decreased from upstream to downstream with shifts in TN:TP from values >20 in the freshwater portion, ~20 in the estuarine portion and <20 in the marine portion indicating a spatial shift in nutrient limitations along the continuum. Aquatic productivity analysis suggests that the estuary is net heterotrophic with productivity being negatively influenced by TP, TN and TOC likely due to a combination of effects including shading by high color dissolved organic matter. We conclude that rainfall patterns, land use and the resulting discharges of run-off drives the ecology of the C-43/CRE aquatic continuum and associated biogeochemistry rather than water management associated with Lake Okeechobee.

ecology↗