Stable Isotope Biogeochemistry of South Florida Coastal Marine Ecosystems

Southeast Florida’s continual urban expansion will potentially increase anthropogenic pollution in adjacent coastal marine systems. Furthermore, increased nutrient loads could have detrimental effects on the already threatened Florida Reef Tract. The present study uses a stable isotopic approach to determine the sources and the impact of nutrients on the Florida Reef Tract. δ13C and δ15N analysis of macroalgae, sponges, and sediment were analyzed in order to determine nutrient inputs in this region. While δ13C data did not display any significant trends spatially, δ15N values of the majority of biota exhibited a strong East to West gradient with more enriched values close to shore. Relative enrichment in δ15N values were measured for sediments sampled along the Florida Reef Tract in comparison to a pristine Marquesas Keys sediment core. The δ15N data also implies that shoreline anthropogenic nutrients have more nutrient loading implications on reefs than major point sources.

A comunidade zooplanctônica como bioindicadora do estado trófico de reservatórios da região semiárida tropical

E utrophication in continental aquatic ecosystems and the following deterioration of water quality are some of the greatest problems to be solved in this century. Due to their own peculiarities reservoirs from semi - arid regions constitute a great challenge to water management because of their greater vulnerability to eutrophication process. I dentification of biolo gical community components that may be used as bioindicators is important to allow an early detection of adverse changes, and also to provide subsidies for management and conservation actions. The aim of the present study is to evaluate the potential of zo oplankton community as bioindicator of the trophic state of two reservoirs belonging to the Piranhas - Açu basin, RN, Brazil: Boqueirão de Parelhas and Passagem das Traíras. Monthly sampling s of both systems were carried out in both systems during the period of January to December. Measurements were performed for temperature, pH, dissolved oxygen and water electrical conductivity besides water samples collection for nutrients, suspended solids, chlorophyll - a and zooplankton analyses. T axonomic composition of zooplankton , density and biomass were analysed. Trophic state index, ABC curves , W statistic and the Calanoida: Cyclopoida ratio were also obtained. The results evidenced that Boqueirão de Parelhas reservoir was a mesotrophic sy stem, and Passagem das Traíras r eservoir was eutrophic. In both reservoirs zooplankton community had low species richness, mostly constituted by tolerant species which have wide geographical distribution, as well the dominance of the rotifers Brachionus havanaensis , B. calyciflo rus and Keratella tropica ; of the calanoid copepods Notodiaptomus cearensis and N. iheringi ; cyclopoid copepod Thermocyclops decipiens, and of the cladocerans Ceriodaphnia cornuta and Diaphanosoma spinulosum . Among the biological indices the ABC curves fo r the zooplankton community indicated a moderate dis turbance in both reservoirs, th e Calanoida: Cyclopoida ration indicated not impacted environments , e xcept during the end of the study to the reservoir Passagem das Traíras . It was concluded that the indices used are good indicators of disturbance and alteration in the community, however they are not good indicators for monitoring the trophic state of the studied reservoirs due to the simultaneous occurrence of other factors selecting species, as the c oncentration of ions and high turbidity, which are part of the reservoir characteristics of semiarid.

Influência de eventos hidrológicos extremos na qualidade da água de reservatórios na região tropical semiárida

Reservoirs are artificial ecosystems, intermediate between rivers and lakes, with diferent morphological and hydrological characteristics that can provide many important benefits to society. However, the use of this water for human consumption, watering livestock, leisure, irrigated agricultural production and pisciculture development, directly influence the increase loading of nutrients to aquatic environments and contribute to acceleration of eutrophication. Furthermore, global climate models are predicting a higher occurrence of extreme events such as floods and severe droughts, which will create hydrological stresses in lakes. In the semiarid northeast we can see the occurrence of these events, the drought of the years 2012, 2013 and 2014 was the worst drought in 60 years, according to the National Water Agency (ANA). Thus, this study aimed to evaluate the quality of the semiarid tropical water sources, identifying temporal patterns in periods with extreme hydrological events (floods and severe droughts). The study results showed that Gargalheiras and Cruzeta reservoirs presented significative changes in the limnological variables between rain and severe drought periods, with better appearance and in the most of the water quality variables in the rainy season and higher nutrientes concentrations and high electrical conductivity values in severe season, indicating decay of its quality. However, we found diferent behaviors between the reservoirs in severe drought. While Gargalheiras showed a typical behavior of the region, with high concentrations of algal biomass, indicating the worsening eutrophication, Cruzeta demonstrated a colapse in the total phytoplankton biomass, evidenced by the decrease in chla concentrations. This fact occurred because the low depth and proximity with the sediment facilited the inorganic solids resuspension and, consequently, resulted in turbid water column and light by limitation. In addition, the different behaviors between the reservoirs indicate that the responses of these environments problems such as extreme events must take into account factors such the region climate, size, depth of the reservoir and the basin characteristics.

Qualidade da água de um reservatório e do solo da zona ripária sob diferentes usos na região semiárida do Rio Grande do Norte

Reservoirs are artificial ecosystems intermediate between rivers and lakes widely used in the Brazilian semiarid region as a way to provide water supply due to the said region’s water scarcity. The use of water from these supply sources for multiple uses, along with occupation and utilization of its riparian zone without proper management, directly influences the increased nutrient flow into aquatic environments, there with contributing to the acceleration of eutrophication. The semi-arid region is characterized by peculiar weather conditions, such as severe evaporation, high temperatures with little variation throughout the year and long water residence time, making it susceptible to prolonged drought occurrence, which tends to concentrate the nutrients in reservoirs, which favors the development of eutrophic conditions. Moreover, it is common soil use and occupation by carrying out activities with potential environmental impact on natural resources such as agriculture, livestock farming and lack of sanitation. The aim of this study is both to evaluate the water quality of the Cruzeta Reservoir, located in the semiarid region of Rio Grande do Norte, during a prolonged drought period, and assess the quality of its riparian zone soil under different uses, by monitoring physical-chemical variables. Along the prolonged drought, high levels of turbidity, suspended solids, nutrients and chlorophyll a were verified as present, therefore featuring low water quality. In the riparian zone of Cruzeta Reservoir, the areas under use of agriculture and livestock farming appeared as one of the main diffuse sources of nutrients to the said reservoir, featuring the highest levels of phosphorus and nitrogen in the soil, originated from decomposition of animal excreta and from the use of fertilizers, creating a tendency to increased eutrophication of such water supply source. The indicators of water and soil quality are useful for monitoring and evaluating the conservation status of natural resources, allowing the control and mitigation of the reservoir eutrophication process. This study confirmed the hypothesis that the reduction of water level, resulting from prolonged drought event, aggravates the symptoms of eutrophication; and also that using the soil under severalways modifies the physic chemical properties of the soil, having livestock farming and agriculture as the usages with greatest potential towards yielding P and N to the aquatic environment.

Effects of introduced moose (Alces alces) on vegetation composition, nutrient dynamics, and decomposition rates in boreal forest ecosystems in Newfoundland, Canada

Globally, consumers affect ecosystem processes including nutrient dynamics. Herbivores have been known to slow nutrient flow in boreal forest ecosystems. I examined the effects of introduced moose on disturbed forests of Newfoundland, Canada by conducting a field experiment during August - November 2014 in 20 paired moose exclosure-control plots. I tested whether moose browsing directly and indirectly affected forests by measuring plant species composition, litter quality and quantity, soil quality, and decomposition rates in areas moose exclosure-control plots. I analyzed moose effects using linear mixed effects models and found evidence indicating that moose reduce plant height and litter biomass affecting the availability of carbon, nitrogen, and phosphorus. However, plant diversity, soil quality, and litter decomposition did not differ between moose exclosures and controls. Moose in Newfoundland directly influence plant regeneration and litter biomass while indirect effects on soil ecosystems may be limited by time, disturbance, and climate.

Extrinsic forcing of plant ecosystems in a large igneous province : The Columbia River flood basalt province, Washington State, USA

Peer reviewed

Company Management Approaches — Stewardship or Agency: Which Promotes Better Security in Cloud Ecosystems?

Postprint

Assistant Professor and FCE Co-PI, John Kominoski and collaborators, Chris McVoy and Jim Brock, are investigating the foundational role of floc in the structural and functional attributes of the ridge and slough ecosystems of the Central Everglades.

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Red mangrove juvenile mangroves and mangrove peat soils at the wetland mesocosm facility. Plants were exposed to phosphorus addition and defolitation, mimicing effects of marine storms on coastal mangrove ecosystems.

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Carbon and Nitrogen Stable Isotopic Patterns in South Florida Coastal Ecosystems: Modern and Paleoceanographic Perspectives

Long term management plans for restoration of natural flow conditions through the Everglades increase the importance of understanding potential nutrient impacts of increased freshwater delivery on coastal biogeochemistry. The present study sought to increase understanding of the coastal marine system of South Florida under modern conditions and through the anthropogenic changes in the last century, on scales ranging from individual nutrient cycle processes to seasonal patterns in organic material (OM) under varying hydrodynamic regime, to century scale analysis of sedimentary records. In all applications, carbon and nitrogen stable isotopic compositions of OM were examined as natural recorders of change and nutrient cycling in the coastal system. High spatial and temporal variability in stable isotopic compositions were observed on all time scales. During a transient phytoplankton bloom, ä15N values suggested nitrogen fixation as a nutrient source supporting enhanced productivity. Seasonally, particulate organic material (POM) from ten sites along the Florida Reef Tract and in Florida Bay demonstrated variable fluctuations dependent on hydrodynamic setting. Three separate intra-annual patterns were observed, yet statistical differences were observed between groupings of Florida Bay and Atlantic Ocean sites. The POM ä15N values ranged on a quarterly basis by 7‰, while ä13C varied by 22‰. From a sediment history perspective, four cores collected from Florida Bay further demonstrated the spatial and temporal variability of the system in isotopic composition of bulk OM over time. Source inputs of OM varied with location, with terrestrial inputs dominating proximal to Everglades freshwater discharge, seagrasses dominating in open estuary cores, and a marine mixture of phytoplankton and seagrass in a core from the boundary zone between Florida Bay and the Gulf of Mexico. Significant shifts in OM geochemistry were observed coincident with anthropogenic events of the 20th century, including railroad and road construction in the Florida Keys and Everglades, and also the extensive drainage changes in Everglades hydrology. The sediment record also preserved evidence of the major hurricanes of the last century, with excursions in geochemical composition coincident with Category 4-5 storms.

Human-driven Benthic Jellyfish Blooms: Causes and Consequences for Coastal Marine Ecosystems

Coastal marine ecosystems are among the most impacted globally, attributable to individual and cumulative effects of human disturbance. Anthropogenic nutrient loading is one stressor that commonly affects nearshore ecosystems, including seagrass beds, and has positive and negative effects on the structure and function of coastal systems. An additional, previously unexplored mechanistic pathway through which nutrients may indirectly influence nearshore systems is by driving blooms of benthic jellyfish. My dissertation research, conducted on Abaco Island, Bahamas, focused on elucidating the role that benthic jellyfish have in structuring systems in which they are common (i.e., seagrass beds), and explored mechanistic processes that may drive blooms of this taxa. To establish that human disturbances (e.g., elevated nutrient availability) may drive increased abundance and size of benthic jellyfish, Cassiopea spp., I conducted surveys in human-impacted and unimpacted coastal sites. Jellyfish were more abundant (and larger) from human-impacted areas, positively correlated to elevated nutrient availability. In order to elucidate mechanisms linking Cassiopea spp. with elevated nutrients, I evaluated whether zooxanthellae from Cassiopea were higher from human-disturbed systems, and whether Cassiopea exhibited increased size following nutrient input. I demonstrated that zooxanthellae population densities were elevated in human-impacted sites, and that nutrients led to positive jellyfish growth. As heightened densities of Cassiopea jellyfish may exert top-down and bottom-up controls on flora and fauna in impacted seagrass beds, I sought to examine ecological responses to Cassiopea. I evaluated whether there was a relationship between high Cassiopea densities and lower benthic fauna abundance and diversity in shallow seagrass beds. I found that Cassiopea have subtle effects on benthic fauna. However, through an experiment conducted in a seagrass bed in which nutrients and Cassiopea were added, I demonstrated that Cassiopea can result in seagrass habitat modification, with negative consequences for benthic fauna. My dissertation research demonstrates that increased human-driven benthic jellyfish densities may have indirect and direct effects on flora and fauna of coastal marine systems. This knowledge will advance our understanding of how human disturbances shift species interactions in coastal ecosystems, and will be critical for effective management of jellyfish blooms.

(Table 1) Methane concentrations, MOX rates and MOB abundance in arctic aquatic ecosystems of the Lena Delta, Northeast Siberia

Large amounts of organic carbon are stored in Arctic permafrost environments, and microbial activity can potentially mineralize this carbon into methane, a potent greenhouse gas. In this study, we assessed the methane budget, the bacterial methane oxidation (MOX) and the underlying environmental controls of arctic lake systems, which represent substantial sources of methane. Five lake systems located on Samoylov Island (Lena Delta, Siberia) and the connected river sites were analyzed using radiotracers to estimate the MOX rates, and molecular biology methods to characterize the abundance and the community composition of methane-oxidizing bacteria (MOB). In contrast to the river, the lake systems had high variation in the methane concentrations, the abundance and composition of the MOB communities, and consequently, the MOX rates. The highest methane concentrations and the highest MOX rates were detected in the lake outlets and in a lake complex in a floodplain area. Though, in all aquatic systems we detected both, Type I and II MOB, in lake systems we observed a higher diversity including MOB, typical of the soil environments. The inoculation of soil MOB into the aquatic systems, resulting from permafrost thawing, might be an additional factor controlling the MOB community composition and potentially methanotrophic capacity.

Biogeochemical data from terrestrial and aquatic ecosystems in a periglacial catchment, West Greenland

Global warming is expected to be most pronounced in the Arctic where permafrost thaw and release of old carbon may provide an important feedback mechanism to the climate system. To better understand and predict climate effects and feedbacks on the cycling of elements within and between ecosystems in northern latitude landscapes, a thorough understanding of the processes related to transport and cycling of elements is required. A fundamental requirement to reach a better process understanding is to have access to high-quality empirical data on chemical concentrations and biotic properties for a wide range of ecosystem domains and functional units (abiotic and biotic pools). The aim of this study is therefore to make one of the most extensive field data sets from a periglacial catchment readily available that can be used both to describe present-day periglacial processes and to improve predictions of the future. Here we present the sampling and analytical methods, field and laboratory equipment and the resulting biogeochemical data from a state-of-the-art whole-ecosystem investigation of the terrestrial and aquatic parts of a lake catchment in the Kangerlussuaq region, West Greenland. This data set allows for the calculation of whole-ecosystem mass balance budgets for a long list of elements, including carbon, nutrients and major and trace metals.