scholarly journals Variability in the Structure of Phytoplankton Assemblages in relation to Human Disturbance in Southern Coast of Tunisia

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Lotfi Mabrouk ◽  
Lamia Dammak ◽  
Asma Hamza ◽  
Mabrouka Mahfoudhi ◽  
Med-Najmeddine Bradai
Keyword(s):  
Human Disturbance ◽  
Sampling Design ◽  
Scuba Diving ◽  
Industrial Effluents ◽  
Southern Coast ◽  
Phytoplankton Assemblage ◽  
Phytoplankton Assemblages ◽  
P Limitation ◽  
Hierarchical Sampling ◽  
The Impact

We investigated the impact of industrial effluents on phytoplankton assemblage in southern Tunisia (Skhira). We specifically addressed changes in microalgae composition caused by this anthropogenic interference. A hierarchical sampling design was used to compare planktonic microalgae structure between one disturbed station and one control station. Samples were collected by scuba diving at 5 m depth in August 2012. A total of 76 microalgae taxa were identified. Dinoflagellates abundance was low in the disturbed station, especially Gonyaulacales and Prorocentrales due to P-limitation, whereas diatoms and cyanobacteria abundance were low in control station which is characterized by Si-limitation.

Assessment of Phytoplankton Nutrient Limitation in Productive Waters: Application of Dilution Bioassays

1993 ◽  
Vol 50 (10) ◽  
pp. 2208-2221 ◽  
Author(s):  
Hunter J. Carrick ◽  
Claire L. Schelske ◽  
Frederick J. Aldridge ◽  
Michael F. Coveney
Keyword(s):  
Large Fraction ◽  
Nutrient Concentrations ◽  
Nutrient Loads ◽  
Nutrient Reduction ◽  
High Concentration ◽  
Phytoplankton Assemblages ◽  
Lake Apopka ◽  
P Limitation ◽  
Management Scheme ◽  
Total P

Excessive nutrient loads to aquatic systems can complicate otherwise predictable relationships between nutrient concentrations and phytoplankton biomass. We conducted six bioassays on surface phytoplankton assemblages collected from productive Lake Apopka, Florida, to measure the effect of nutrient reduction on phytoplankton growth and nutritional state. Lake water was mixed with one of three diluents to create a gradient of ambient nutrient concentrations; nitrogen (N) and phosphorus (P) limitation at each level of dilution was evaluated in a 2 × 2 factorial design. While the addition of N clearly increased the growth of phytoplankton in undiluted Lake Apopka water, the phytoplankton became more P limited with the reduction of particles (30–60% dilution). Regression of algal yields onto total P concentrations from our bottle experiments indicated that an 8 μg∙L−1 change in P leads to only a 1 μg∙L−1 change in chlorophyll yield, probably due to the high concentration of P in the lake. Because dilution influences factors in addition to ambient nutrient concentrations, results obtained with the technique must be carefully evaluated. Despite this, reduction of particles to improve water quality may, in concept, be a reasonable management scheme in lakes where a large fraction of the nutrients is particulate.

Changes in escape behaviour of black iguanas (Ctenosaura similis) over an anthropogenic disturbance gradient

Behaviour ◽  
2021 ◽  
pp. 1-21
Author(s):  
Pooja Panwar ◽  
Pilar Angélica Gómez-Ruiz ◽  
Matthew N. Zipple ◽  
Luis Sandoval
Keyword(s):  
Human Disturbance ◽  
Protected Area ◽  
Anthropogenic Disturbance ◽  
Escape Behaviour ◽  
Human Presence ◽  
Disturbed Areas ◽  
Disturbance Gradient ◽  
The Impact ◽  
Ctenosaura Similis ◽  
Flight Initiation

Abstract Studies on the impact of human activity on animal behaviour are critical for understanding the extent to which humans affect ecological dynamics. Previous studies have found that human presence alters antipredator behaviours, which can be measured by flight initiation distance (FID). We investigated escape behaviour of 96 black iguanas (Ctenosaura similis) across a gradient of human disturbance in six sites inside a protected area in Costa Rica. We used a field experiment to test for effect of human disturbance on FID. We found that individuals from higher disturbance sites had shorter FIDs, meaning that black iguanas from disturbed areas allow closer approaches. This finding is consistent with the prediction that some animals become more habituated to human presence as the degree of human disturbance increases. We propose that black iguanas’ ability to alter their behaviour in response to humans’ presence could make them especially adept at invading new environments.

scholarly journals Two High-Nutrient Low-Chlorophyll phytoplankton assemblages: the tropical central Pacific and the offshore Perú-Chile Current

2007 ◽  
Vol 4 (6) ◽  
pp. 1101-1113 ◽  
Author(s):  
F. Gómez ◽  
H. Claustre ◽  
P. Raimbault ◽  
S. Souissi
Keyword(s):  
A Priori ◽  
Austral Summer ◽  
Centric Diatom ◽  
Phytoplankton Assemblage ◽  
Central Pacific ◽  
Phytoplankton Assemblages ◽  
Southern Limit ◽  
Marquesas Islands ◽  
Acid Ratio ◽  
High Nutrient

Abstract. The phytoplankton (>15 μm) composition and abundance was investigated along a ~8000 km transect between the Marquesas Islands Archipelago and the Chilean coasts off Concepción. In the southern limit of the central Equatorial Pacific (at 8° S, 141° W), in High-Nutrient Low-Chlorophyll (HNLC) warm waters, the microphytoplankton assemblage was dominated by the lightly silicified diatoms Pseudo-nitzschia delicatissima and Rhizosolenia bergonii. The morphology of these species, a small pennate diatom that exhibited a tendency to form "ball of needles" clusters and large centric diatom (>500 μm long), are interpreted as two anti-grazing strategies in an environment dominated by small micrograzers. Surprisingly, this a priori typical HNLC phytoplankton assemblage was also found in the temperate offshore waters of the Perú-Chile Current between 2000 and 600 km off Chile. This observation suggests that a common set of environmental factors (obviously other than temperature and salinity) are responsible for the establishment and maintaining of this distinctive phytoplankton in these geographically and hydrologically distant regions. Both regions are characterized by a surface nitrate-silicic acid ratio ranging from 1–3. Occasionally Rhizosolenia bergonii showed frustules anomalously fragmented, likely the result of extreme weakly silicified phytoplankton. We suggest that silicon deficiency may be responsible of the occurrence of HNLC phytoplankton assemblage in the tropical central Pacific as well as the offshore Perú-Chile Current during the austral summer.

scholarly journals Palaeoenvironmental dynamics of Holocene shoreface bryoliths from the southern coast of Brazil

The Holocene ◽  
2019 ◽  
Vol 29 (4) ◽  
pp. 662-675 ◽  
Author(s):  
Frederico Tapajós de Souza Tâmega ◽  
Paula Spotorno-Oliveira ◽  
Paula Dentzien-Dias ◽  
Francisco Sekiguchi Buchmann ◽  
Leandro Manzoni Vieira ◽  
...  
Keyword(s):  
Human Disturbance ◽  
Rio Grande ◽  
Coralline Algae ◽  
Southern Coast ◽  
Rio Grande Do Sul ◽  
Benthic Habitats ◽  
Free Living ◽  
Storm Waves ◽  
Water Carbonate ◽  
Shallow Water Carbonate

Beds of free-living coated nodules (coralline algae, bryozoans, acervulinid foraminifera) create shallow-water carbonate biogenic benthic habitats, which are sensitive to human disturbance and slow to recover. Holocene bryoliths, ranging from sub-spheroidal, sub-discoidal to sub-ellipsoidal in shape, were found scattered in the foredunes in ca. 30-km stretch along the Hermenegildo and Concheiros do Albardão beaches on the southernmost coast of Brazil (Santa Vitória do Palmar municipality, Rio Grande do Sul State). The dominating bryozoan species forming the bryolith is Biflustra holocenica Vieira, Spotorno-Oliveira and Tâmega sp. nov. The inner bryolith arrangement, generally asymmetrical, shows multilamellar and circumrotatory growth of colonies that envelop the bivalve Ostrea puelchana. Bryozoans and subordinate corals characterize the outer bryolith surfaces. The ichnogenera Gastrochaenolites (made by the boring bivalve Lithophaga patagonica) and Caulostrepsis occur throughout the bryoliths, from the inner part up to the outer surface. The studied bryoliths, originated in a shoreface setting at ca. 7910–7620 cal. yr BP and during subsequent storm waves, were resedimented onto the foreshore and foredunes (to ca. 5700 cal. yr BP) where the bryoliths were finally fossilized.

scholarly journals Future Climate Change Will Have a Positive Effect on Populus davidiana in China

Forests ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 1120 ◽  
Author(s):  
Jie Li ◽  
Guan Liu ◽  
Qi Lu ◽  
Yanru Zhang ◽  
Guoqing Li ◽  
...  
Keyword(s):  
Climate Change ◽  
Human Disturbance ◽  
Vulnerability Index ◽  
Future Climate ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
Degree Of Protection ◽  
Populus Davidiana ◽  
The Impact ◽  
Degree Of Fragmentation

Since climate change significantly affects global biodiversity, a reasonable assessment of the vulnerability of species in response to climate change is crucial for conservation. Most existing methods estimate the impact of climate change on the vulnerability of species by projecting the change of a species’ distribution range. This single-component evaluation ignores the impact of other components on vulnerability. In this study, Populus davidiana (David’s aspen), a tree species widely used in afforestation projects, was selected as the research subject under four future climate change scenarios (representative concentration pathway (RCP)2.6, RCP4.5, RCP6.0, and RCP8.5). Exposure components of range change as well as the degree of fragmentation, degree of human disturbance, and degree of protection were considered simultaneously. Then, a multicomponent vulnerability index was established to assess the effect of future climate change on the vulnerability of P. davidiana in China. The results show that the distribution range of P. davidiana will expand to the northwest of China under future climate change scenarios, which will lead to an increased degree of protection and a decreased degree of human disturbance, and hardly any change in the degree of fragmentation. The multicomponent vulnerability index values of P. davidiana under the four emission scenarios are all positive by 2070, ranging from 14.05 to 38.18, which fully indicates that future climate change will be conducive to the survival of P. davidiana. This study provides a reference for the development of conservation strategies for the species as well as a methodological case study for multicomponent assessment of species vulnerability to future climate change.

scholarly journals TOURISM AND URBANIZATION: ENVIRONMENTAL PROBLEMS OF THE ARARUAMA LAGOON, STATE OF RIO DE JANEIRO, BRAZIL

2016 ◽  
Vol 19 (4) ◽  
pp. 59-80 ◽  
Author(s):  
THAYSE CRISTINA PEREIRA BERTUCCI ◽  
◽  
EDSON PEREIRA SILVA ◽  
AGUINALDO NEPOMUCENO MARQUES JR. ◽  
CASSIANO MONTEIRO NETO ◽  
...  
Keyword(s):  
Political Ecology ◽  
Rio De Janeiro ◽  
Secondary Data ◽  
Industrial Effluents ◽  
Negative Effects ◽  
The Sustainable Development ◽  
Scenic Beauty ◽  
Appropriate Treatment ◽  
Development Processes ◽  
The Impact

Abstract The Araruama Lagoon (Rio de Janeiro) is known for its scenic beauty and natural resources, factors that have led to the economic expansion of the region. In recent decades, tourism and property speculation have been key to the urban development of the municipalities surrounding this Lagoon. Using secondary data and a theoretical framework based on Political Ecology and Critical Environmental Education, this article seeks to analyze the correlations between the development processes of the towns surrounding the Lagoon and the impact of these processes on the environmental quality of its ecosystem. In recent years, the evolution of parameters studied revealed that the imbalance in terms of the sustainable development of the region has damaged the health of this body of water. Large quantities of fresh water, as well as domestic and industrial effluents discharged without appropriate treatment in the Lagoon, have overloaded the ecological system, with negative effects for the entire economy in the surrounding area.

scholarly journals Proximate and ultimate controls on carbon and nutrient dynamics of small agricultural catchments

2016 ◽  
Vol 13 (6) ◽  
pp. 1863-1875 ◽  
Author(s):  
Zahra Thomas ◽  
Benjamin W. Abbott ◽  
Olivier Troccaz ◽  
Jacques Baudry ◽  
Gilles Pinay
Keyword(s):  
Water Quality ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Water Chemistry ◽  
Human Disturbance ◽  
Nutrient Dynamics ◽  
Agricultural Activity ◽  
Agricultural Catchments ◽  
The Impact ◽  
The Relationship

Abstract. Direct and indirect effects from human activity have dramatically increased nutrient loading to aquatic inland and estuarine ecosystems. Despite an abundance of studies investigating the impact of agricultural activity on water quality, our understanding of what determines the capacity of a watershed to remove or retain nutrients remains limited. The goal of this study was to identify proximate and ultimate controls on dissolved organic carbon and nutrient dynamics in small agricultural catchments by investigating the relationship between catchment characteristics, stream discharge, and water chemistry. We analyzed a 5-year, high-frequency water chemistry data set from three catchments in western France ranging from 2.3 to 10.8 km2. The relationship between hydrology and solute concentrations differed between the three catchments and was associated with hedgerow density, agricultural activity, and geology. The catchment with thicker soil and higher surface roughness had relatively invariant carbon and nutrient chemistry across hydrologic conditions, indicating high resilience to human disturbance. Conversely, the catchments with smoother, thinner soils responded to both intra- and interannual hydrologic variation with high concentrations of phosphate (PO43−) and ammonium (NH4+) in streams during low flow conditions and strong increases in dissolved organic carbon (DOC), sediment, and particulate organic matter during high flows. Despite contrasting agricultural activity between catchments, the physical context (geology, topography, and land-use configuration) appeared to be the most important determinant of catchment solute dynamics based on principle components analysis. The influence of geology and accompanying topographic and geomorphological factors on water quality was both direct and indirect because the distribution of agricultural activity in these catchments is largely a consequence of the geologic and topographic context. This link between inherent catchment buffering capacity and the probability of human disturbance provides a useful perspective for evaluating vulnerability of aquatic ecosystems and for managing systems to maintain agricultural production while minimizing leakage of nutrients.

Effect of phosphorus limitation on microbial floc structure and gene expression in activated sludge

2006 ◽  
Vol 54 (1) ◽  
pp. 247-255 ◽  
Author(s):  
J.R. Liu ◽  
C.T. Liu ◽  
E.A. Edwards ◽  
S.N. Liss
Keyword(s):  
Gene Expression ◽  
Activated Sludge ◽  
Extracellular Polymeric Substances ◽  
Morphological Changes ◽  
Cell Structure ◽  
Operating Conditions ◽  
P Limitation ◽  
Floc Structure ◽  
The Impact ◽  
Log Ratio

The effect of limiting phosphorus (P) in activated sludge was investigated in laboratory-scale sequencing batch reactors (SBRs). Correlative microscopy revealed that P-limitation (COD:N:P=100:5:0.05) leads to morphological changes in floc structure and the composition of extracellular polymeric substances (EPS). This was found to be accompanied by expression of quorum-sensing in an acyl homoserine lactone bioassay. Differential gene expression in relation to P-limitation was examined in a global profile using the Affymetrix™ Escherichia coli antisense genomic microarray. Three separate experiments were conducted where the impact of P-limitation was examined under batch conditions and in SBRs at stable operating conditions and within 3–7 days following a down-shift in P. Significant changes in open reading frames (ORF) and intergenic regions based on the E. coli microarray were observed. Several genes associated with cell structure, including slt, wbbH, fimH, amB, rfaJ and slp were found to be expressed. Quorum regulated genes were also found to be expressed including psiF which is known to be induced by P-starvation (92% confidence level; 1.45 log ratio).

Identification of inhibitory effects of industrial effluents on nitrification

2009 ◽  
Vol 59 (4) ◽  
pp. 797-803 ◽  
Author(s):  
A. Žgajnar Gotvajn ◽  
J. Zagorc-Končan
Keyword(s):  
Oxygen Consumption ◽  
Activated Sludge ◽  
Landfill Leachate ◽  
Industrial Effluents ◽  
Tannery Effluent ◽  
Ammonium Oxidation ◽  
Pharmaceutical Wastewater ◽  
Heterotrophic Microorganisms ◽  
Nitrification Process ◽  
The Impact

The aim of our work was to determine the extent of inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation (ISO 8192 2007) for various wastewaters. We have selected several types of wastewaters different in their origin and composition: pharmaceutical wastewater, tannery wastewater and municipal landfill leachate. To confirm results of toxicity testing, additional ready biodegradability assessment test with measurement of oxygen consumption was accomplished to indicate the impact of effluents to nitrification process. Pharmaceutical wastewater was toxic to activated sludge, but it inhibited heterotrophic microorganisms much more than nitrifying ones. Biodegradability testing confirmed low impact to nitrification by high, non-suppressed oxygen consumption for nitrification process. Tannery effluent inhibited nitrification significantly (180 min EC50 was 57 vol.%), but it did not affect heterotrophic microorganisms. Landfill leachate was very toxic to heterotrophic microorganisms (180 min EC50 was 3 vol.%), while it inhibited nitrification less (180 min EC50 was 24 vol.%). Presented research confirmed that the investigated experimental method is a reliable one for detection of occurrence of substances inhibiting nitrification in different industrial effluents. With regular monitoring of inhibitory impact biological treatment process upsets could be avoided and treatment optimised.

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