High Turbidity Levels Research Articles

Comparative limnology of natural and man-made tropical lakes

This paper assessed and compared physicochemical profiles and biodiversity indices of two shallow lakes namely the natural Bera Lake and Bukit Merah reservoir in Peninsular Malaysia. Variations in relation to hydro-meteorological variables, including rainfall, wind speed and air temperature were also measured during the field sampling. The results showed clear distinctions between natural and man-made lakes in terms of physical and chemical properties of lake waters and their relationships to the hydro-meteorological dynamic. Persistent oxygen and temperature differences between the epilimnion and hypolimnion were clearly detected in Bukit Merah reservoir under low winds and strong heat. Oxycline also persist during flooding or high turbidity levels indicating their enriched bottom waters. On the other hand, the natural Bera lake showed temporary stratification during the dry season with low winds but the water columns were thoroughly mixed during the wet season when the water temperature was lower and wind speed was higher. Plankton diversity in Bera lake was significantly higher (p < 0.05) than the Bukit Merah reservoir, probably due to the much longer history of the natural lake compared to the man-made one. Due to the longer residence time of the reservoir compared to the natural lake, the former tends to be more vulnerable to eutrophication if subjected to uncontrolled nutrient enrichment.

Environmental constraint of intraguild predation: Inorganic turbidity modulates omnivory in fairy shrimps

Abstract Omnivory is widespread in food webs, with an important stabilising effect. The strength of omnivorous trophic interactions may change considerably with changes in the local environment. Shallow temporary waters are often characterised by high levels of inorganic turbidity that may directly limit the food uptake of filter‐feeding organisms, but there is little evidence on how it might affect omnivorous species. Anostracans are key species of temporary waters and recent evidence suggests that these organisms are omnivorous consumers of both phyto‐ and zooplankton. Using Branchinecta orientalis as a model species, our aim was to test how turbidity affects the feeding of an omnivorous anostracan. To do this, we used short‐term feeding experiments and stable isotope analyses, with animals collected from soda pans in eastern Austria. In the feeding experiments, algae and zooplankton were offered as food either separately or in combination. The prey type treatments were crossed with turbidity levels in a factorial design. There was a pronounced decrease in the ingested algal biomass with increasing turbidity. Conversely, ingestion rates on zooplankton were less affected by turbidity. Stable isotope analyses from field material supported our experimental results by showing a positive relationship of the trophic position of anostracans and the trophic niche of the communities with turbidity. Our results show that turbidity modulates the intraguild trophic relationship between anostracans and their prey by shifting the diet of anostracans from more herbivorous in transparent to more carnivorous in turbid waters. Thus, inorganic turbidity might also have a community‐shaping role in plankton communities of temporary waters through altering trophic relationships.

Effect of Extreme Weather Events on the Sedimentation of the Bay of Samaná, Dominican Republic (1900–2016)

The Bay of Saman&amp;aacute;, formed by tectonism and sedimentation, is delimited to the north by the peninsula of the same name, to the south by the north slope of the Eastern Mountain Range and Los Haitises National Park, to the east by the Atlantic Ocean, and to the west by the ancient Gran Estero, today the Lower Yuna. There follows a process of continuous degradation by the existing tectonic forces and the sediment contributions by the Yuna, Yab&amp;oacute;n, and La Yeguada rivers to the south as well as by the landslides of the mountainous area of the Saman&amp;aacute; Peninsula, during periods of storms and hurricanes. The coastal area of Saman&amp;aacute; Bay has altered by 2.17 km2 at the mouth of the Yuna River from 2003&amp;ndash;2015. The high turbidity level has affected coral reefs and marine species.&amp;nbsp; The&amp;nbsp; mangroves&amp;nbsp; are&amp;nbsp; lost&amp;nbsp; faster&amp;nbsp; than&amp;nbsp; they&amp;nbsp; are&amp;nbsp; regenerated&amp;nbsp; by&amp;nbsp; the&amp;nbsp; coastline&amp;rsquo;s change. Variations in the elemental compositions of calcium and iron show the terrigenous influence on the dynamics of the bay during Extreme Weather Events (EWP) in the river basins that flow into it. Abrupt changes in the rainfall regime produced an equal change in the estuary sedimentation regime, according to the 210Pb. In the 2007&amp;ndash;2016 period, a column of sediment that reached 38 cm and a 12 cm to 8.4 km column were deposited 4 km southeast of the municipality of S&amp;aacute;nchez and east of the mouth of the Yuna River. The Sedimentary Accumulation Rate is very high, and&#x0D; the content of heavy metals exceeds the threshold values of Table SQuirt.

Densities of reef-associated fish and corals on offshore platforms in the Gulf of Mexico

The northern Gulf of Mexico possesses 1320 offshore oil/gas platforms, currently being removed at a rapid rate. Thirteen species of scleractinian corals inhabit these structures, and a positive association is known to exist between reef-associated fishes and coral. Here, we studied 22 platforms on the Mississippi River delta, an area devoid of natural reefs. We quantified the abundance of reef-associated fishes on platforms occurring in 19–334 m depths. We recorded 18 reef-associated fish species, most commonly Stegastes leucostictus (Muller and Troschel, 1848), Stegastes partitus (Poey, 1868), Abudefduf saxatilis (Linnaeus, 1758), Abudefduf taurus (Muller and Troschel, 1848), and Chromis multilineata (Guichenot, 1853). In water depths ≥25 m, average fish densities ranged from 1.0 to 15.3 m–2. No reef-associated fishes were observed on structures in 66 m depth, the fish densities dropped to zero. Average coral densities per platform in waters >30 m deep ranged from 0.4 to 173.0 colonies m–2. Individual sample densities ranged from 0 to 945.0 colonies m–2. There was a significant positive correlation between average reef-associated fish density and bottom water depth. There was also a positive correlation between average fish density and average coral density. The data indicated that coral and fish densities were lower in inshore waters. These waters are generally characterized by low salinity, low winter seawater temperatures, high turbidity, and high nutrient levels. Our data showed that the fish community is linked to the coral community, as is known to occur on natural reefs. We believe that these numerous organisms add environmental value to the platforms.

English

Dodowa serves as a major peri-urban community close to the Accra Metropolis with increasing population, urbanization and settlements. Lack of access to basic infrastructural facilities including water and sanitation has hampered the development of the community. Dodowa has irregular access to pipe-borne water therefore the community resorts to other means of getting potable water. It is against this background that this study was conceived to assess the quality of drinking water sources in the community. Groundwater (Hand-Dug-Wells), stored water from pipes and mobile tanker water services were sampled to ascertain their quality since they were the major sources of water supply in the community. In all, 100 samples were collected for four months, 8 hand dug wells and 2 boreholes were sampled for groundwater, 10 stored water in either poly tanks or concrete tanks and then 5 mobile tanker water services were also sampled and physico-chemical and bacteriological parameters were assessed. The sources of water were also assessed to ascertain their quality. The available water sources in the Dodowa township could not be considered potable especially the groundwater which had high levels of turbidity, total dissolved solids (TDS), chloride, sodium and iron and therefore needs treatment before use. All the water sources had coliform bacteria which could cause water borne disease such as cholera, typhoid, dysentery and diarrhea thus unsafe for drinking without treatment. Key words: Physico-chemical, microbiological, groundwater, potable water, water quality, Dodowa, coliform bacteria.

Coupled effects of anthropogenic nutrient sources and meteo-oceanographic events in the trophic state of a subtropical estuarine system

This study investigated how the biogeochemical processes and water quality of Madre's Estuarine System (MES) are influenced by different environmental conditions and nutrient runoff from a poor-regulated watershed. We applied the Land-Ocean Interactions in the Coastal Zone (LOICZ) model to estimated water and nutrient fluxes and the net ecosystem metabolism. The closest region to agriculture, the inner estuary, showed hypoxic and anoxic conditions, nutrients maxima in the bottom waters and organic enrichment in the sediment. In contrast, lower nutrients concentrations and oxic waters were found in the middle estuary, where autotrophic conditions predominated. The system's trophic state was directly correlated with the volume of precipitation, wind intensity and depth. The water column was oligotrophic and predominantly composed by freshwater during rainfall events. Southerly winds forced the intrusion of coastal waters into the estuary, increasing water column stratification, both physical and chemical, and the trophic state. This study demonstrated that nutrient runoff from the irrigate rice culture and untreated sewage are boosting symptoms of eutrophication. Also, the high turbidity levels might be replacing phytoplankton species by an opportunistic macrophyte. The low water residence time was an important mechanism to improve the water quality, exporting elevated nutrients loads to the continental shelf.

Estimated light compensation depth explains growth of Stuckenia pectinata in Te Waihora

Loss of a long-term stable submerged macrophyte community reverses shallow lakes from a clear into a turbid water state. Stuckenia pectinata densely colonised the marginal area of a shallow coastal lagoon Te Waihora (Lake Ellesmere) before its removal by the 1968 “Wahine” storm. This study aims to understand the current light availability for S. pectinata growth in Te Waihora with high turbidity and water level fluctuations. In a greenhouse experiment, acclimations in S. pectinata to lower light intensities involved elongation in stems and leaves, and an increase in photosynthetic efficiency per unit dry weight for both leaves and stems. However, these acclimations did not reduce the daily compensation irradiance (under which daily net photosynthesis equals zero) that was identified at 8.8 ± 0.9 μmol photons m−2 s-1. Subsequently, we estimated light compensation depth (LCD), based on the derived daily compensation irradiance, incident irradiance at the water surface, and light attenuation coefficients for the lake. In areas shallower than LCD, there is no light limitation for the growth of S. pectinata. The LCD ranged from 0.23 to 0.54 m and well explained the growth range of S. pectinata in Te Waihora during the 2016–2017 ecological survey. The estimated LCD also suggests low turbidity levels in early spring are critical for the growth of S. pectinata with the current water level fluctuation regimes. LCD is a useful parameter for understanding the growth of submerged macrophytes in shallow turbid lakes from the perspective of light availability.

Evaluation of the raw water quality: physicochemical and toxicological approaches.

Environmental degradation has increased, mainly as a result of anthropogenic effects arising from population, industrial and agricultural growth. Water pollution is a problem that affects health, safety and welfare of the whole biota which shares the same environment. In Goiânia and metropolitan region, the main water body is the Meia Ponte River that is used for the abstraction of water, disposal of treated wastewater and effluents. In addition, this river receives wastewater from urban and rural areas. The aim in this present study was to evaluate the quality of raw water by some physical, chemical and toxicological tests. The physicochemical results found high levels of turbidity, conductivity, aluminum, phosphorus and metal iron, manganese, copper and lithium when compared to the standards of the Brazilian legislation. The values found of toxicity demonstrated a high degree of cytotoxicity and genotoxicity. Therefore, it was concluded that the Meia Ponte River has been undergoing constant environmental degradation, causing the poor quality of its waters. Thus, measures for the prevention and recovery should be adopted for the maintenance of the Meia Ponte River.

Modeling the remote-sensing reflectance of highly turbid waters.

In ocean-color remote sensing, subsurface remote-sensing reflectance (r r s ) of optically deep waters can be linked to its absorption (a) and backscattering coefficients (b b ) by various models. The use of such models allows for quick calculations r r s from such coefficients, eliminating the need to solve the radiative transfer equation. In particular, r r s can be expressed as a function of bb/(a+bb). HydroLight and Monte Carlo simulations showed that commonly used models underestimate r r s in waters with high suspended sediment loads. Monte Carlo simulations confirmed that this issue is due to a sharp increase in multiple scattering events at high turbidity levels. A quartic polynomial model is derived relating r r s and inherent optical properties (IOPs) for waters of any turbidity, to avoid significant errors in waters of high turbidity.

Physiochemical Analysis of Community Water Supply in Kathmandu Valley

This study was carried out to assess groundwater quality of the Kathmandu Valley, Nepal, because Safe drinking water is a basic need of all humans and to protect the human health, community water suppl y must be reliable, adequate and readily accessible to all segments of the consumers. For this the groundwater samples from eight different regions of the valley were collected during months of Jun-Jul in the year 2018. Th ese collected groundwater samples were analyzed various physio-chemical parameters such as temperature, colour, turbidity, pH, electric conductivity (EC), total alkalinity, phenolphthalein alkalinity, total hardness, iron, chloride,Nitrate and total ammonia using the procedure outlined in the standard methods. Results showed that the water quality status was found to vary from place to place. High levels of turbidity, total alkalinity, total hardness, iron and total ammonia were found in the groundwater of many sites. The results were compared with WHO water quality guideline and National Drinking Water Quality Standard (NDWQS) of Nepal.

Assessment of Physico-Chemical Parameters and Their Pollution Implications on the Major Dams in Ekiti State

The study was aimed at assessing the Physico-chemical parameters namely, temperature, electrical conductivity (EC), pH, turbidity, total alkalinity (TA), total hardness (TH), total dissolved solids (TDS), dissolved oxygen (DO2); total solids (TS), total suspended solids (TSS) colour, potassium, Zinc, Copper, total Iron, BOD, COD etc. in three dams in Ekiti State, South-West Nigeria. The seasonal variations in the physicochemical parameters of water of the dams were studied from November, 2017 to October, 2018. Water samples were collected from the dams on monthly basis and analyzed for 26 water physico-chemical parameters by using standard methods. The standards for the drinking water recommended by the Indian Council of Medical Research (ICMR), World Health Organization (WHO), Nigerian Industrial Standard (NIS), National Environmental Standards and Regulations Enforcement Agency (NESREA) and Bureau of Indian standards (BIS) were used in this study. The comparison of the physico-chemical parameters values with the standard values of WHO guidelines and other international standards revealed the high level of BOD, COD, turbidity, DO2, pH, colour, K, Fe, Mn, Cu, Zn, Pb and Cd in the water content. There were significant differences (p > 0.05) between the seasons (dry and wet) values of some of the physicochemical parameters in Egbe dam, Ureje dam and Ero dam. pH, DO2, TSS, EC, TDS and TS had higher values in the rainy season while Temperature, BOD, COD, NO3, Alkalinity, NO2 and PO4 had higher values during the dry season in the dams with few exemptions. The accumulation of these parameters in high values may render the dams’ water unsuitable for drinking. In this study, it was observed that most of the physico-chemical parameters except metals were higher in Ureje dam than Egbe dam and Ero dam. This might be due to population increase, indiscriminate dumping of refuse around the dam, urbanization, domestic effluents and other attendant problems of the State capital where the dam is located and thus indicate that Ureje dam was more contaminated than Egbe and Ero dams in terms of anthropogenic contamination. Conclusively, the water from Egbe, Ureje and Ero dams may support fish production but is not fit for domestic and drinking purpose without adequate treatment.

Water quality and anthropogenic impact in the watersheds of service reservoirs in the Brazilian semi-arid region

The semi-arid region of Brazil is characterised by the irregular temporal and spatial distribution of the rainfall, which together with anthropogenic action causes degradation of the water quality. The aim of this study was to evaluate water quality in surface reservoirs in the Brazilian semi-arid region due to rainfall variability and the degree of anthropisation of the watersheds. Water samples were collected at the Oros, Trussu and Muquem reservoirs during August and December of 2012, April, October and December of 2013, and March and June of 2014 (dry and rainy periods). The following limnological attributes were analysed: electrical conductivity, pH, turbidity, transparency and chlorophyll-a, with the results evaluated using box plots, and the mean values compared by Student’s t-test. Anthropogenic data from the watersheds contributing to the reservoirs were used to correlate limnological attributes with the condition of the watersheds during the dry period of 2013. The rainfall was not sufficient to significantly improve the water quality of the reservoirs, and in the Oros Reservoir high levels of chlorophyll-a and turbidity occurred during both periods. Anthropisation of these areas has a direct influence on the water quality of the surface reservoirs of the Upper Jaguaribe, showing a correlation with the attributes of water quality, especially with pH. Total degradation of the surface waters of the Upper Jaguaribe Basin due to land use in the watersheds is just a matter of time.

Evaluación de la calidad de agua de ríos de colombia usando parámetros físicoquímicos y biológicos

Se analizaron las características físicas, químicas y microbiológicas (coliformes totales, coliformes fecales y macroinvertebrados acuáticos) de diversos ríos de Colombia y se determinó el índice de calidad de agua (IQA) de los ríos estudiados. Se encontraron altos niveles de turbiedad y sólidos disueltos totales (SDT) sugiriendo que el agua de los ríos de Colombia no posee condiciones óptimas para el crecimiento y la reproducción de diversos organismos acuáticos. Además, se encontraron altos niveles de coliformes fecales, asociado con la existencia de vertimientos de aguas residuales, indicando que gran parte del agua de los ríos de Colombia, no es apta para consumo humano. Además el índice de BMWP/Col. correspondió a aguas ligeramente contaminadas y el Índice de calidad de agua (IQA) sugirió un recurso hídrico altamente contaminado, existiendo congruencia entre los dos índices anteriormente mencionados y algunas variables fisicoquímicas y biológicas, que presentaron valores superiores a los permisibles establecidos por la normatividad Colombiana

Biotreatment of petroleum refinery wastewater in vertical surface-flow constructed wetland vegetated with Eichhornia crassipes: lab-scale experimental and kinetic modelling

ABSTRACTThe objectives of this study were to evaluate the potential of vertical surface flow constructed wetland (VSF-CW) vegetated with Eichhornia crassipes to treat petroleum refinery secondary wastewater under tropical conditions. Also, to provide a comparative evaluation of biotreatment kinetic models (traditional first order and other alternative kinetic models) proposed to describe the removal kinetics of organics (biochemical oxygen demand (BOD) and chemical oxygen demand (COD)), nitrate-nitrogen and total petroleum hydrocarbons (TPH) in wetland systems. The refinery secondary wastewater was characterized and treated in five VSF-CWs. Eichhornia crassipes were planted in three VSF-CWs and the remaining two VSF-CWs served as the unvegetated control. The wastewater relatively had high levels of turbidity (18.30 ± 3.88 NTU), BOD (20.40 ± 2.20 mg/L), COD (86 ± 6.0 mg/L), TPH (16.6 ± 1.76 mg/L), oil and grease (18.4 ± 2.00 mg/L), heavy metals (Cadmium (0.034 ± 0.01 mg/L), Lead (0.12 ± 0.05 mg/L), Chromium (0.47 ± 0.01 mg/L), Iron (1.54 ± 0.25 mg/L) and Nickel (0.09 ± 0.01 mg/L)) and Chloride (1412 ± 9.6 mg/L). The vegetated VSF-CWs significantly performed better than the unvegetated control and resulted in the removal efficiencies of 91.5% turbidity, 94.6% BOD5, 80.2% COD, 92.6% TPH, 90.4% oil and grease, 94% cadmium, 92.5% lead, 93% chromium, 94.8% iron, 92.2% nickel, and 57.7% chloride. The results suggested that the proposed kinetic models were applicable for understanding the removal mechanisms of organics, nitrate-nitrogen and hydrocarbons in VSF-CW systems. Thus, Eichhornia crassipes planted VSF-CW has the potential of treating refinery secondary wastewater to discharge permissible limits.

Domination of mesophotic ecosystems in the Wakatobi Marine National Park (Indonesia) by sponges, soft corals and other non-hard coral species

AbstractMesophotic ecosystems have been relatively poorly studied in the Indo-Pacific and in particular within the Coral Triangle region. Here we used a mini-ROV to explore the changes in major benthic groups at two sites (~200 m apart) in the Wakatobi Marine National Park, SE Sulawesi, Indonesia spanning shallow water coral reefs (5 m) to deeper water mesophotic ecosystems (80 m). We found very similar patterns at both sites where coral cover peaked at 15 m, declined rapidly by 30 m, and was virtually absent at 50 m. As coral declined there was a marked increase in sponges, soft corals and other encrusting organisms (including ascidians, bryozoans, tubeworms, gorgonians and molluscs). Importantly, our results differ from most previous studies in other geographic locations where hard corals extend much deeper. It is unclear what drives this difference but it may be related to higher levels of turbidity and therefore reduced light penetration in the Wakatobi compared with other areas, which limits the vertical extent of coral development.

A Novel System for Water Disinfection with UV Radiation

We present a novel system for water disinfection with ultra-violet (UV) radiation. In this system, the UV lamps do not come into contact with the water and hence remain free of fouling. The system incorporates a diffusor and a nozzle, with stationary guide vanes built into each. Their combined purpose is to reduce the hydraulic losses while imparting a strong swirl component to the flow. The swirl significantly enhances turbulent mixing processes and provides a self-cleansing mechanism that renders the system tolerant to high levels of turbidity and scaling. The hydrodynamic performance of the system was optimized using Computational Fluid Dynamics, while the manufacture of its key components was accomplished using advanced mechanical design software and three-dimensional (3D) printing. Biodosimetry testing with the bacteriophage MS2 indicated the delivery of a UV dose of 215.6 mJ/cm2. This produced a 6.9 log10 reduction of E. coli and 7.12 log10 reduction of MS2. Assessment of the system with hard water containing high Ca, Mg, and Fe concentrations, and with water with turbidity of 18 NTU indicated that the log10 removal of E. coli remained above 5.

DEB parameter estimation for Saccostrea cucullata (Born), an intertidal rock oyster in the Northern Bay of Bengal

Dynamic Energy Budget (DEB) models describe the energy flow in organisms focusing on food assimilation and utilization for maintenance, growth and reproduction. In this paper, specific DEB parameters were obtained for the intertidal rock oyster Saccostrea cucullata, which has culture potential and important ecological functions in estuarine and coastal ecosystems along the Bay of Bengal, Bangladesh. Oyster samples were collected from natural oyster beds and used in a starvation experiment for 20 weeks in the laboratory. A sub-sample of starved oyster was used to record respiration rates and depletion of reserves was recorded by fortnightly measurements of flesh weight. Simultaneously, a group of oysters was used for physiological experiments and growth measurements, required for DEB parameter estimation. Consequently, Arrhenius temperature related parameters (i.e. TA, TL, TH, TAL, and TAH), shape coefficient (δM), volume specific maintenance rate (ṖM) and volume specific cost for structure ([EG]) were estimated using data from the respiration and starvation experiments. An iterative co-variation method was used to estimate the specific DEB parameters using the results of the physiological experiments, field observations and additional literature information. Estimated Arrhenius temperature was 5640 K, which applies between 297 and 305 K. Shape coefficient (δM = 0.159) was low, compared to other oyster species that characterized the morphology of the oyster. Volume specific maintenance rate (ṖM) was equivalent to 17.99 J cm−3 day−1, while 2377 J cm−3 was estimated as the volume specific cost for structure ([EG]). These efforts provide opportunities to apply the DEB model for better understanding the energetics of bivalves under sub-tropical conditions. It is concluded that the hydrometeorological aspects, i.e. a monsoon regime and high turbidity levels, are quite different from temperate regions and drives the physiological traits of shellfish organisms.

The performance of sludge blanket clarifier against conventional settler under high water turbidity conditions

Abstract The performance of a sludge blanket clarifier was evaluated and compared to conventional settlers under high levels of turbidity and algae in the field and experimentally. Field data of sludge blanket and conventional clarifier operation were observed simultaneously for the treatment of highly turbid water. In addition, a comparison was carried out on turbidity removal efficiency, algae removal, and sludge accumulation pattern. Finally, these systems were simulated in the laboratory and operated to treat turbid water with high levels of turbidity and algae up to 80 NTU and 109cells/l respectively. Field data confirmed that the sludge blanket clarifier equipped with upper sludge cones has a high removal efficiency of turbidity and algae, ease of use and has insignificant sludge accumulation compared to the conventional settler. Further, laboratory experiments have confirmed that sludge blanket clarifier is also very effective for the treatment of high algae concentrations up to 109cells/l, with a short retention time, compared to a conventional settler, which was not effective under these conditions.

Variations of Bacterial Community Composition and Functions in an Estuary Reservoir during Spring and Summer Alternation.

In this study, we focused on the dynamics of bacterial community composition in a large reservoir in the Yangtze estuary during spring and summer seasons, especially the variations of functional mechanisms of microbial community during the seasonal alternation between spring and summer. Both 16S rRNA gene sequencing and shotgun metagenomic sequencing technology were used for these purposes. The results indicated that obvious variations of bacterial community structures were found at different sites. Particle-associated bacterial taxa exhibited higher abundance at the inlet site, which was closer to the Yangtze River with a high level of turbidity. In other sites, Synechococcus, as the most dominant cyanobacterial species, revealed high abundance driven by increased temperature. Moreover, some heterotrophic bacterial taxa revealed high abundance following the increased Synechococcus in summer, which indicated potential correlations about carbon source utilization between these microorganisms. In addition, the shotgun metagenomic data indicated during the period of seasonal alternation between spring and summer, the carbohydrate transport and metabolism, energy production and conversion, translation/ribosomal biogenesis, and cell wall/membrane/envelope biogenesis were significantly enhanced at the exit site. However, the course of cell cycle control/division was more active at the internal site.

Melting of clean and debris‐rich ice differentially affect nutrients, dissolved organic matter and bacteria respiration in the early ontogeny of the newly formed proglacial Ventisquero Negro Lake (Patagonia Argentina)

Abstract Climate change affects glaciers all over the world causing glacial recession with the formation of new lakes. Glaciers of Mount Tronador (41° S, Patagonia, Argentina) underwent an increase of more than 200 m in the equilibrium‐line altitude (ELA), from 1994 to 2016. The proglacial Lake Ventisquero Negro showed a continuous increase in lake surface area since 2009, when a glacial outburst flood (GLOF) occurred. The Ventisquero Negro glacier is a debris‐covered glacier located below the timberline; thus, the lake receives meltwater from both clean and debris‐rich ice. This study analyses the proglacial lake after the GLOF event, particularly the nutrient content, dissolved organic matter and bacterial respiration. Our main hypothesis was that the melting of debris‐rich and clean ice would differentially affect nutrient inputs and bacterial respiration in the early ontogeny of the lake. Sampling was conducted in austral spring–summer seasons (2012 to 2016) following the GLOF event. We carried out bacterial respiration experiments with lake water and two treatments enriched with clean or debris‐rich ice from the glacier. Additionally, we carried out an another enrichment experiment with phosphate‐P and glucose‐C alone or in combination. The lake exhibited high turbidity levels due to a high concentration of suspended solids. Vertical light profiles showed that almost the entire water column was aphotic. Phosphorus (P) concentration was high and was positively related to total suspended solids. Accordingly, P concentration was higher in debris‐rich than in clean ice. However, the dissolved organic carbon concentrations in the lake were found to remain relatively constant through time (less than 50 μmol/L). Analysing fluorescent excitation–emission matrices, we determined that the dissolved organic matter is very simple with only two peaks, one corresponding to protein‐like compounds (C1) and the other to humic‐like compounds (C2), coming from clean ice and debris‐rich ice, respectively. C1 was present in all samples, while C2 was comparatively more important during summer, coinciding with higher temperatures and melting. This study supports the hypothesis that melting of clean and debris‐rich ice would affect DOM and P input at early stages of a proglacial lake formed by the recession of a debris‐covered glacier. Bacterial respiration was observed to be positively affected by debris‐rich ice melting and to be P limited. Thus, P is a major controlling factor for carbon dynamics in a newly formed proglacial lake.