scholarly journals High rates of biodeposition and N-excretion indicate strong functional effects of mussels (Bivalvia: Unionida) in certain anthropogenic tropical freshwater habitats

Hydrobiologia ◽  
2020 ◽  
Author(s):  
Alexandra Zieritz ◽  
Wei Ning Chan ◽  
Suzanne McGowan ◽  
Christopher Gibbins
Keyword(s):  
Freshwater Mussels ◽  
Rice Paddy ◽  
Ammonia Nitrogen ◽  
Nutrient Concentrations ◽  
Strong Increase ◽  
Considerable Proportion ◽  
Clearance Rates ◽  
Natural Diet ◽  
Functional Roles ◽  
Tropical Systems

AbstractThe functional roles of freshwater mussels (Unionida) in tropical systems are poorly understood. We quantified the effects of mussel filtration, excretion and deposition in three anthropogenic tropical systems, i.e. a man-made lake, abandoned mining pool and rice paddy channel. Sinanodonta cf. woodiana (non-native) was present at all three sites, whilst Pilsbryoconcha compressa (native) was present in the channel only. Clearance rates, biodeposition rates and effects on suspended algal pigment and dissolved nutrient concentrations were quantified in controlled, replicated experiments in laboratory tanks with water from original habitats. Clearance rates were generally low and did not explain the high biodeposition rates observed. A considerable proportion of the natural diet of these populations may therefore consist of material that was not available in tanks, i.e. benthic or deposited algae. Deposition rates in lake and channel populations exceeded published rates from temperate and Mediterranean habitats, presumably due to prevalence of non-palatable material and/or higher metabolic rates in tropical systems. The presence of S. cf. woodiana but not P. compressa led to a strong increase in total ammonia nitrogen concentrations and N:P ratios, exceeding estimations from other systems. This study suggests that freshwater mussels play different functional roles in anthropogenic tropical habitats than in temperate systems.

Algal flux affects the clearance rates of recently metamorphosed freshwater mussels

2016 ◽  
Vol 79 (1) ◽  
pp. 139-148 ◽  
Author(s):  
Rakesh Mistry ◽  
Josef D. Ackerman
Keyword(s):  
Freshwater Mussels ◽  
Clearance Rates

The Effects of Rainfall Patterns on Runoff, Sediment, and Nutrients Under Various Artificial Rainfall Experiments

2021 ◽  
Author(s):  
Hanna Mariana Henorman ◽  
Duratul Ain Tholibon ◽  
Masyitah Md Nu ◽  
Hamizah Mokhtar ◽  
Jamilah Abd Rahim ◽  
...  
Keyword(s):  
Overland Flow ◽  
Surface Characteristics ◽  
Ammonia Nitrogen ◽  
Mean Value ◽  
Nutrient Loss ◽  
Rainfall Pattern ◽  
Nutrient Concentrations ◽  
Affected Area ◽  
Rainfall Patterns ◽  
Runoff Sediment

Abstract Assessing the effects of rainfall patterns on runoff, sediment, nutrients under variation of rainfall pattern are significant in the quantification of sediment transported by overland flow. Previous experimental and field works studied that sediment transport is influenced by hydraulic properties of flow, physical properties of soil and surface characteristics. This study aims at determining the effect of rainfall patterns on surface runoff, sediment loss and nutrient loss. Experiments were carried out using four rainfall patterns, namely Pattern A (uniform-type: 8-8-8 l/min), Pattern B (increasing-type: 7-8-9 l/min), Pattern C (increasing-decreasing-type: 7-9-8 l/min) and Pattern D (decreasing-type: 9-8-7 l/min) with the changes of intensity every 30 minutes that gives total rainfall duration of 90 minutes for each pattern. The simulation was performed in three repetitions. The average total runoff produced was 668.65, 701.40, 699.10, and 722.63 liters, for rainfall patterns A, B, C, and D, respectively. The trend of runoff generated was influenced by the rainfall patterns, Pattern D generated the highest amount of runoff meanwhile Pattern A generated the lowest. For total suspended sediment concentrations, the mean value among every three repetitions of rainfall pattern resulted as 14,518.88, 13,732.73, 8,011.71 and 19,918.50 mg/l for patterns A, B, C, and D, respectively Pattern D contributed to the highest amount of sediment accumulated whereby Pattern C generated the lowest sediment despite the trend showed a different approach than the other 3 patterns. In nutrient concentrations, the determined total losses for ammonia nitrogen were 3.986, 2.891, 3.504, and 4.601g; nitrate nitrogen were 3.934, 2.665, 4.008, and 3.259g; phosphorus were 1.346, 0.222, 0.207, and 0.679g, for patterns A, B, C, and D, respectively. In general, rainfall pattern does have a significant impact on the trend of nutrient losses, where the trend shows that higher concentrations at the start and eventually lowered through the end, but Pattern D as compared to other patterns resulted in a more severe nutrient loss. For the affected area of the soil movement process, the calculated means of the affected area are 79.60, 68.70, 72.43, and 64.97% for patterns A, B, C, and D respectively. The lowest mean of the affected area is contributed by Pattern D and the highest by Pattern A.

scholarly journals Oceanic CO<sub>2</sub> outgassing and biological production hotspots induced by pre-industrial river loads of nutrients and carbon in a global modelling approach

2019 ◽  
Author(s):  
Fabrice Lacroix ◽  
Tatiana Ilyina ◽  
Jens Hartmann
Keyword(s):  
Net Primary Production ◽  
Co2 Flux ◽  
Ocean Model ◽  
Global Ocean ◽  
Nutrient Concentrations ◽  
Strong Increase ◽  
Tropical Atlantic ◽  
Nutrient Inputs ◽  
Dissolved Carbon

Abstract. Rivers are a major source of nutrients, carbon and alkalinity for the global ocean, where the delivered compounds strongly impact biogeochemical processes. In this study, we firstly estimate pre-industrial riverine fluxes of nutrients, carbon and alkalinity based on a hierarchy of weathering and land-ocean export models, while identifying regional hotspots of the land-ocean exports. Secondly, we implement the riverine loads into a global biogeochemical ocean model and describe their implications for oceanic nutrient concentrations, the net primary production (NPP) and CO2 fluxes globally, as well as in a regional shelf analysis. Thirdly, we quantify the terrestrial origins and the long-term oceanic fate of riverine carbon in the framework, while assessing the potential implementation of riverine carbon fluxes in a fully coupled land-atmosphere-ocean model. Our approach leads to annual pre-industrial riverine exports of 3.7 Tg P, 27 Tg N, 158 Tg Si and 603 Tg C, which were derived from weathering and non-weathering sources and were fractionated into organic and inorganic compounds. We thereby identify the tropical Atlantic catchments (20 % of global C), Arctic rivers (9 % of total C) and Southeast Asian rivers (15 % of total C) as dominant providers of carbon to the ocean. The riverine exports lead to a global oceanic source of CO2 to the atmosphere (231 Tg C yr−1), which is largely a result of a source from inorganic riverine carbon loads (183 Tg C yr−1), and from organic riverine carbon inputs (128 Tg C yr−1). Additionally, a sink of 80 Tg C yr−1 is caused by the enhancement of the biological carbon uptake by dissolved inorganic nutrient inputs, resulting alkalinity production and a slight model drift. While large outgassing fluxes are mostly found in proximity to major river mouths, substantial outgassing fluxes can also be observed further offshore, most prominently in the tropical Atlantic. Furthermore, we find evidence for the interhemispheric transfer of carbon in the model; we detect a stronger relative outgassing flux (49 % of global river induced outgassing) in the southern hemisphere in comparison to the hemisphere's relative riverine inputs (33 % of global river inputs), as well as an outgassing flux of 17 Tg C yr-1 in the Southern Ocean. Riverine exports lead to a strong increase in NPP in the tropical West Atlantic, Bay of Bengal and the East China Sea (166 %, 377 % and 71 % respectively). While the NPP is not strongly sensitive to riverine loads on the light limited Arctic shelves, the CO2 flux is strongly altered due to substantial dissolved carbon supplies to the region. While our study confirms that the ocean circulation is the main driver for open ocean biogeochemical distributions, it reveals the necessity to consider riverine exports for the representation of heterogeneous features of the coastal ocean, to represent riverine-induced carbon outgassing, as well as to consider the long-term volcanic CO2 flux to close the atmospheric carbon budget in a coupled land-ocean-atmosphere setting.

Phytoplankton composition in the subtropical coastal shelf environment of Cape Canaveral, Florida

2020 ◽  
Vol 96 (4) ◽  
pp. 593-616
Author(s):  
Mary C Tate ◽  
Edward J Phlips ◽  
Ben Stelling ◽  
Susan Badylak ◽  
Leslie Landauer ◽  
...  
Keyword(s):  
Sediment Surface ◽  
Nutrient Concentrations ◽  
Strong Increase ◽  
Nutrient Loads ◽  
Column Temperature ◽  
Surface Samples ◽  
Numerical Abundance ◽  
Bottom Waters ◽  
Negative Buoyancy ◽  
Regional Land

The abundance and composition of the phytoplankton community off the coast of Cape Canaveral, Florida was examined from Fall 2013 to Summer 2015. The region is a shallow shelf environment. Water samples were collected quarterly at 24 sites from the surface and bottom of the water column; temperature and nutrient concentrations were determined. Photoautotrophic picoplanktonic prokaryotes (PPP) were consistently important in terms of numerical abundance and biomass throughout the study. Among the cyanobacteria, a surface bloom of the nitrogen-fixing filamentous species Trichodesmium was observed in Fall 2013. Dinoflagellates and diatoms were also major contributors to phytoplankton biomass. Many of the dominant dinoflagellates were mixotrophic or heterotrophic species. Nanoplanktonic eukaryotic algae were also periodically an important group in terms of biomass, such as prasinophytes (Chlorophyta). No consistent and reoccurring spatial patterns were observed, likely due to the dynamic water circulation in the open Cape Canaveral shelf environment. Depth-related differences in biomass were observed for dinoflagellates and diatoms. Dinoflagellate biomass was on average higher in surface samples, related to their motility. Conversely, diatom biomass was on average higher in bottom waters, reflecting the negative buoyancy of most species and the potential for re-suspension of cells from the sediment surface. The strong increase in the importance of PPP biomass observed in year 2 of the study may reflect the influence of high rainfall resulting from El Niño conditions on nutrient loads from regional land masses, as indicated by increases in phosphorus concentrations.

What Determines The Migration Intentions Of University Students?

2014 ◽  
Vol 1 (1) ◽  
pp. 193-198
Author(s):  
Heiko Haase ◽  
Arndt Lautenschläger
Keyword(s):  
University Students ◽  
Career Choice ◽  
Cross Sectional Study ◽  
Demographic Characteristics ◽  
Migration Decision ◽  
Considerable Proportion ◽  
Sectional Study ◽  
Intention To Stay ◽  
Cross Sectional ◽  
The University

AbstractThe paper aims at exploring determinants of the university students' intentions to stay within their university region. At this, we presume that students' career choice motivations are related to their professional intentions, which again, along with demographic characteristics, affect their migration decision. Our analysis is based on a cross-sectional study of 2,353 students from three different higher education institutions, two of them located in Germany and one in Namibia. Results indicate that in Germany migration matters because a considerable proportion of students intend to leave the university region after graduation. At this, we found that the students' geographical provenance exerts the most significant effect on the intention to stay. Moreover, certain professional intentions were directly and some career choice motivations were indirectly linked with the intention to remain at the university location. We present several conclusions and implications.

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