Chlorophyll-a Levels Research Articles

Ecological correlates of blue whale movement behavior and its predictability in the California Current Ecosystem during the summer-fall feeding season

BackgroundSpecies distribution models have shown that blue whales (Balaenoptera musculus) occur seasonally in high densities in the most biologically productive regions of the California Current Ecosystem (CCE). Satellite telemetry studies have additionally shown that blue whales in the CCE regularly switch between behavioral states consistent with area-restricted searching (ARS) and transiting, indicative of foraging in and moving among prey patches, respectively. However, the relationship between the environmental correlates that serve as a proxy of prey relative to blue whale movement behavior has not been quantitatively assessed.MethodsWe investigated the association between blue whale behavioral state and environmental predictors in the coastal environments of the CCE using a long-term satellite tracking data set (72 tagged whales; summer-fall months 1998–2008), and predicted the likelihood of ARS behavior at tracked locations using nonparametric multiplicative regression models. The models were built using data from years of cool, productive conditions and validated against years of warm, low-productivity conditions.ResultsThe best model contained four predictors: chlorophyll-a, sea surface temperature, and seafloor aspect and depth. This model estimated highest ARS likelihood (> 0.8) in areas with high chlorophyll-a levels (> 0.65 mg/m3), intermediate sea surface temperatures (11.6-17.5 °C), and shallow depths (< 850 m). Overall, the model correctly predicted behavioral state throughout the coastal environments of the CCE, while the validation indicated an ecosystem-wide reduction in ARS likelihood during warm years, especially in the southern portion. For comparison, a spatial coordinates model (longitude × latitude) performed slightly better than the environmental model during warm years, providing further evidence that blue whales exhibit strong foraging site fidelity, even when conditions are not conducive to successful foraging.ConclusionsWe showed that blue whale behavioral state in the CCE was predictable from environmental correlates and that ARS behavior was most prevalent in regions of known high whale density, likely reflecting where large prey aggregations consistently develop in summer-fall. Our models of whale movement behavior enhanced our understanding of species distribution by further indicating where foraging was more likely, which could be of value in the identification of key regions of importance for endangered species in management considerations. The models also provided evidence that decadal-scale environmental fluctuations can drive shifts in the distribution and foraging success of this blue whale population.

Monitoring Coastal Lagoon Water Quality through Remote Sensing: The Mar Menor as a Case Study

The Mar Menor is a hypersaline coastal lagoon located in the southeast of Spain. This fragile ecosystem is suffering several human pressures, such as nutrient and sediment inputs from agriculture and other activities and decreases in salinity. Therefore, the development of an operational system to monitor its evolution is crucial to know the cause-effect relationships and preserve the natural system. The evolution and variability of the turbidity and chlorophyll-a levels in the Mar Menor water body were studied here through the joint use of remote sensing techniques and in situ data. The research was undertaken using Operational Land Imager (OLI) images on Landsat 8 and two SPOT images, because cloudy weather prevented the use of OLI images alone. This provided the information needed to perform a time series analysis of the lagoon. We also analyzed the processes that occur in the salt lagoon, characterizing the different spatio-temporal patterns of biophysical parameters. Special attention was given to the role of turbidity and chlorophyll-a levels in the Mar Menor ecosystem with regard to the programs of integral management of this natural space that receives maximum environmental protection. The objective of the work has been fulfilled by answering the questions of the managers: when did the water quality in the Mar Menor begin to change? What is happening in the lagoon? Is remote sensing useful for monitoring the water quality in the Mar Menor? The answers to these questions have allowed the generation of a methodology and monitoring system to track the water quality in the Mar Menor in real-time and space. The tracking system using satellite images is open to the incorporation of images provided by new multispectral sensors.

Chlorophyll-a, and Sea Surface Temperature (SST) as proxies for Climate Changes: Case Study in Batu Ampar waters, Riau Islands

The condition of Indonesian oceanography is largely determined by the development of the Monsoon Wind and the Indonesian Cross Flow (ARLINDO). The development of marine remote sensing technology that is so fast, able to make it easier to map the condition of waters in Indonesia in an actual way easily and cheaply. This can make it easier to obtain information about climate change approaches to the physical oceanography conditions in Indonesian waters. The purpose of this research is to study the changes of the physical oceanography parameters resulting from climate changes. Based on the results of the research that for the highest Sea Surface Temperature (SST) exist in 2013 (above 30,75 °C). It has increased from the previous year i.e. in 2012 with an increase of SST value of 30 o C. In 2013 SST is spread high on the Batu Ampar Permit - Harbor Bay ferry port. Analyzing the value of chlorophyll-a, sea surface temperature, and sea level to see global climate change in the waters of Batu Ampar. The analysis shows the highest sea level with an elevation of 3.1 meters, with sea surface temperature in the range of 29,5 °C - 29,75 °C, at the time of recording 00:05-02:55 (August 1, 2017 - September 1, 2017). The results of the analysis obtained from the oceanographic conditions in the waters of Batu Ampar did not experience a fluctuating change in global climate change in the waters. The annual SST interval spacing interval of 0.5-0.75 °C and the changing phase relationship could have an impact on subsequent climate change and sea level rise to be concrete evidence. Reduced levels of chlorophyll-a each year will have an impact on the heat of the sea level, thus rising sea levels and indicating a climate with hot temperatures (ice at the poles melt).

DETERMINATION OF SOME MACRO ELEMENT CONCENTRATIONS AND CHLOROPHYLL-A DISTRIBUTION IN A SHALLOW LAKE WETLAND (GÖKÇEADA SALT LAKE LAGOON, ÇANAKKALE/TURKEY)

In this study, the macro element concentrations and chlorophyll-a distribution in the Gökçeada Salt Lake Lagoon which is in the category of Shallow Lake Wetland in Gökçeada (Canakkale) were evaluated. For this purpose, some macro elements (Nitrite, Nitrate, Sulfate, Phosphate, Calcium, Magnesium, Potassium, and Phosphorus) and chlorophyll-a levels as well as water temperature and dissolved oxygen values were measured in 2016 as seasonally (January, May, August, November) from three stations. During the autumn season, nitrite, nitrate, phosphate and sulfate values measured as 5.65 ppm; 16.9 ppm; 77 ppm; and 8547 ppm, respectively. As a result, the macro element concentrations deposited in the sediment and the chlorophyll-a amounts of the lake was signed to the ecological conditions are very suitable for the development of eutrophication. In the end of the study, some suggestions were done to protect the ecosystem balance.

Excess nutrient loads to Lake Taihu: Opportunities for nutrient reduction

Intensive agriculture and rapid urbanization have increased nutrient inputs to Lake Taihu in recent decades. This resulted in eutrophication. We aim to better understand the sources of river export of total dissolved nitrogen (TDN) and phosphorus (TDP) to Lake Taihu in relation to critical nutrient loads. We implemented the MARINA-Lake (Model to Assess River Inputs of Nutrients to seAs) model for Lake Taihu. The MARINA-Lake model quantifies river export of dissolved inorganic and organic N and P to the lake by source from sub-basins. Results from the PCLake model are used to identify to what extent river export of nutrients exceeds critical loads. We calculate that rivers exported 61 kton of TDN and 2 kton of TDP to Lake Taihu in 2012. More than half of these nutrients were from human activities (e.g., agriculture, urbanization) in Sub-basins I (north) and IV (south). Most of the nutrients were in dissolved inorganic forms. Diffuse sources contributed 90% to river export of TDN with a relatively large share of synthetic fertilizers. Point sources contributed 52% to river export of TDP with a relatively large share of sewage systems. The relative shares of diffuse and point sources varied greatly among nutrient forms and sub-basins. To meet critical loads, river export of TDN and TDP needs to be reduced by 46–92%, depending on the desired level of chlorophyll-a. There are different opportunities to meet the critical loads. Reducing N inputs from synthetic fertilizers and P from sewage systems may be sufficient to meet the least strict critical loads. A combination of reductions in diffuse and point sources is needed to meet the most strict critical loads. Combining improved nutrient use efficiencies and best available technologies in wastewater treatment may be an effective opportunity. Our study can support the formulation of effective solutions for lake restoration.

Zooplankton Taxonomic and Trophic Community Structure Across Biogeochemical Regions in the Eastern South Pacific

Biochemical conditions and taxonomic composition of size-fractioned mesozooplankton were studied after a cruise conducted in September 2015 between the Chilean coast (70°W) and Easter Island (110°W) within the central south Pacific gyre. Taxonomy was assessed with an automated method based on image analysis and biochemical conditions assessed by analyses of C and N contents and stable isotope composition. Based on surface Chlorophyll-a levels, four regions were distinguished across the zonal gradient: eutrophic (Chilean upwelling zone), mesotrophic (Coastal Transition Zone), oligotrophic (open ocean water) and ultraoligotrophic (central south Pacific gyre). The zones had marked differences in temperature, oxygen, salinity and Chlorophyll-a, and they also exhibited significant differences in zooplankton composition, C/N ratios and13C and 15Nfor all size fractions of zooplankton. Variability in the sources of C and N, linked to biogeochemical processes, such as new production and denitrification in the upwelling zone, potential diazotrophy, highly regenerated C and N and extreme oligotrophy (N-deficiency) in oceanic areas, are suggested as the key drivers of these differences. Our findings also suggest a strong coupling between taxonomic and size zooplankton-diversity and the sources of nutrients that fuel phytoplankton, the major food source for zooplankton. Although multiple factors and processes can modulate C and N and their isotopes composition of zooplankton biomass, our study shows that changes in community structure are linked to different biogeochemical regions across the zonal gradient, providing the basis for ecological zonation associated with nutrient utilization at lower trophic levels.

Trophic dynamics (Dissolved Inorganic Nitrogen-DIN and Dissolved Inorganic Phosphorus-DIP) in tropical urban estuarine systems during periods of high and low river discharge rates.

This paper focused on the use of the biogeochemical LOICZ (Land Ocean Interactions in the Coastal Zone) to investigate the dynamics of DIN and DIP nutrients among three highly urbanized tropical estuaries (Barra das Jangadas (BJ), Recife (RE) and Timbó (TB)), located in the northeastern region of Brazil. The input data were obtained through in situ measurements (2007) and governmental agency databases (2001-2007). The balances of the non-conservative elements showed that the RE and TB systems alternated between sources and sinks during the observation periods (0.2-0.8 mmoles DIP m-2 d-1 and 0.1-10 mmoles DIN m-2 d-1). The metabolism rates in the systems indicated that the BJ system was autotrophic during the two observation periods (10-26 mmoles C m-2 d-1), while the RE system was heterotrophic (9-12 mmoles C m-2 d-1). The river discharge rates observed during the period 2001-2007 showed averages ranging from 9.4±3.8 to 18.4±7.7 m3s-1. Measurements of the trophic status in the RE system during 2007 characterized the system as eutrophic, thereby demonstrating high levels of chlorophyll-a and inorganic nutrients. The applications of balance sheets modeling proved to be very useful toward understanding the dynamics of estuarine systems dominated by large urban centers.

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.

Phytoplankton Productivity and Hydrology in an Impacted Estuarine Complex in Northeastern Brazil

The aim of the current study was to evaluate the productive capacity of the phytoplankton community and other environmental variables in the estuarine area of Suape; while considering the constant morphological, sedimentological and hydrological changes, the site has been facing due to the implementation and expansion of an industrial and port complex. The study comprised 6 campaigns: 3 in the dry season and 3 in the rainy season. Water samples were collected from the surface layer of the internal and external portions of the estuarine bay during low spring tides. The salinity ranged from 32.20 to 37.10, the water temperature ranged from 26.60°C to 29.40°C, and the oxygen saturation rate ranged from 58.5% to 114.5%. There was significant seasonal variation. The nitrite concentration was higher during the rainy season, whereas the ammonia concentration was higher during the dry season; the higher ammonia concentration helped increase chlorophyll-a levels and rates of primary productivity, which ranged from 0.02 - 2.45 mg·m−3 and from 0.34 to 4.32 mg·C·m−3·h−1, respectively. Chlorophyll-a < 20 μm was the fraction of biomass most commonly present in the estuarine ecosystem, accounting for 88.6% of the chlorophyll-a-containing biomass, and this reflected the low nutrient content in the water and indicated that the area was free from eutrophication processes. The decrease of rainfall during the sampling months and the anthropogenic changes in the environment led to reduced continental contributions, increased marine interference, nutrient dilution and loss of phytoplankton production capacity in Suape Bay, which severely damaged other trophic links in the ecosystem.

Hindcasting eutrophication and changes in temperature and storage volume in a semi-arid reservoir: a multi-decadal Landsat-based assessment.

In situ monitoring of freshwater systems is often constrained by cost and accessibility, particularly in developing countries and in remote areas. Satellite remote sensing is therefore increasingly being integrated with existing in situ water quality monitoring programs. In this study, we use the Landsat TM/ETM+ image record collected between 1984 and 2015 to track temporal changes in trophic status, chlorophyll-a levels, algal bloom incidences, water clarity, water temperature, and reservoir water volume in a poorly monitored hypereutrophic semi-arid reservoir. Historical reservoir water quality data are inferred from calibrated Landsat-based empirical algorithms. The results show that, although the reservoir has existed in a eutrophic to hypereutrophic state over the past 30years, its water quality has significantly deteriorated in the most recent decade. Mean summer chlorophyll-a concentrations were found to have increased by around 163% between 1984 and 2015, while water clarity dropped by more than 58% over the same period. Statistically significant changes in surface water temperatures were also apparent for the month of August, with a cumulative increase of 1.24°C over the 31-year study period. The rise in temperature appears to correlate with the incidence of Microcystis blooms observed in the reservoir over the past decade. On the other hand, the water volume in the reservoir was found to have been fairly stable over time, likely as a result of adaptive reservoir management. This study demonstrates the strength of using Landsat data to hindcast and quantify changes in water quality and quantity in poorly monitored freshwater systems.

Investigating the quality of stored drinking water from the Harare water distribution system, Zimbabwe

Abstract This study investigated the effects of different storage conditions (refrigerator, cupboard and sunlight) on the quality of drinking water collected from the distribution system. The study was carried out in the period June–July 2017 and focussed on selected suburbs of Harare. Sampling sites on the distribution system were grouped into three zones (1, 2 and 3) depending on the proximity to the treatment plant, whether there was further chlorination or not and the water flow path. Three water samples were collected in opaque 5 L containers from one site (tap) in each zone and stored under the three storage conditions and periodically analysed for pH, free residual chlorine, temperature and chlorophyll-a. The pH of stored water increased with storage time for all storage conditions and in all zones. The residual chlorine decreased with time in all zones and under all storage conditions. The chlorophyll-a levels also decreased with time under all storage conditions. Refrigerator samples showed the slowest deterioration of water quality and sunlight the highest. Although the pH of stored water increased with time, it remained within both SAZ and WHO guideline values. Household disinfection of stored water is recommended generally after 1 week of storage.

Seasonal water quality and trophic status of shallow lentic waters and their association with water levels

Extreme hydro-climatic changes associated with floods and drought greatly influence the ecosystem dynamic of tropical lakes in Malaysia, resulting in negative impacts on their water quality and trophic status. This study examined the seasonal changes in water quality and trophic state connected to hydro-ecological changes in a natural lake and two reservoirs. Water levels in the three water bodies varied with changes in rainfall regime, and water regulation for irrigation or water supply. Multivariate analysis of variance showed a significant relationship between season and temperature, pH, conductivity, total nitrogen and chlorophyll-a (p < 0.05). Drought events and the associated period of low water levels were characterized by high temperature, conductivity and chlorophyll-a levels in these shallow lakes, which probably led to high photosynthetic rates with concomitant increase in dissolved oxygen and pH and decrease in total nitrogen concentration. Elevated chlorophyll-a and total phosphorus concentrations were also associated with drought events and the decrease in water level in Bukit Merah Reservoir, possibly due to the release of phosphorus from internal loading resulting from sediment re-suspension by wind. Salinity increase in Durian Tunggal Reservoir during dry season was possibly due to seawater intrusion into river. During the rainy season, transparency in Bera Lake and Bukit Merah Reservoir was strongly influenced by the influxes of the main river that transported elevated levels of suspended solids and nutrients.

Relationship among physicochemical conditions, chlorophyll-a concentration, and water level in a tropical river–floodplain system

The free-flowing Usumacinta River maintains an average annual water-level fluctuation of 6.7 m. This study evaluated relationships between 14 physicochemical and biological variables and key factors in four water-level conditions in a river–floodplain system. The analysis incorporated intra-annual variation in all variables, with each selected in accordance with multiple statistical and physicochemical criteria. Possible correlations were examined as a function of various physicochemical and biological factors at each water level. Within the study area, defined by a temporal gradient in principal component 1, the yearly river overflow above the bankfull stage is characterized by water with a low level of total suspended solids. Data on riverine wetlands suggest that seasonal changes are key to determining intra- and inter-annual chlorophyll-a levels and water clarity. However, opposite trends are observed for high and low water-level conditions. Nutrient enrichment cannot be taken as the key physicochemical factor of water level, under either water-level conditions, due to the lack of a temporal gradient in principal component 2 and the high biochemical variability of nitrate and orthophosphate levels. In conclusion, the hypothesis was accepted for the production of phytoplankton biomass and light attenuation at low and high water levels, as both were dependent on intra-annual changes. The increases in chlorophyll-a related to the minimal variability at the lowest water level open the opportunity to gauge this relationship as a possible environmental predictor for river–floodplain systems.

Distribution of 210Pb and 210Po in the Arctic water column during the 2007 sea-ice minimum: Particle export in the ice-covered basins

210Pb and 210Po are naturally occurring radionuclides that are commonly used as a proxy for particle and carbon export. In this study, the distribution of the 210Po/210Pb pair was investigated in the water column of the Barents, Kara and Laptev Seas and the Nansen, Amundsen and Makarov Basins in order to understand the particle dynamics in the Arctic Ocean during the 2007 sea-ice minimum (August–September). Minimum activities of total 210Pb and 210Po were found in the upper and lower haloclines (approx. 60–130 m), which are partly attributed to particle scavenging over the shelves, boundary current transport and subsequent advection of the water with low 210Pb and 210Po activities into the central Arctic. Widespread and substantial (> 50%) deficits of 210Po with respect to 210Pb were detected from surface waters to 200 m on the shelves, but also in the basins. This was particularly important in the Makarov Basin where, despite very low chlorophyll-a levels, estimates of annual new primary production were three times higher than in the Eurasian Basin. In the Nansen, Amundsen and Makarov Basins, estimates of annual new primary production correlated with the deficits of 210Po in the upper 200 m of the water column, suggesting that in situ production and subsequent export of biogenic material were the mechanisms that controlled the removal of 210Po in the central Arctic. Unlike 210Po, 234Th deficits measured during the same expedition were found to be very small and not significant below 25 m in the basins (Cai et al., 2010), which indicates, given the shorter half-life of 234Th, that particle export fluxes in the central Arctic would have been higher before July–August in 2007 than later in the season.

Foraging behaviour and habitat use by Indian Yellow-nosed Albatrosses (Thalassarche carteri) breeding at Prince Edward Island

ABSTRACTDemographic parameters of wild animals are often closely associated with their foraging distribution and behaviour, and understanding these attributes can assist in identifying causes of population changes. The Indian Yellow-nosed Albatross (Thalassarche carteri) is endangered but little information is available on its at-sea distribution and behaviour. It breeds only in French (Iles Amsterdam, St Paul, Kerguelen and Crozet) and South African (Prince Edward Island, PEI) territories in the south-west Indian Ocean, with PEI supporting about 20% of the global population. This study aimed to investigate the at-sea distributions of adult Indian Yellow-nosed Albatrosses provisioning chicks at PEI and to compare them with distributions of Yellow-nosed Albatrosses breeding at other localities. Using satellite transmitters, we identified two areas that were particularly favoured for foraging. Parents whose partners were brooding small chicks frequently moved north-east of PEI to shallow, productive waters where cold, nutrient-rich water upwells and results in enhanced levels of chlorophyll-a. By contrast, parents with older chicks that could be left unattended often foraged along the Agulhas Bank where eddies and shear forces promote vertical mixing. The at-sea distribution of birds breeding at PEI was located between those reported for Indian Yellow-nosed Albatrosses breeding at Ile Amsterdam and Atlantic Yellow-nosed Albatrosses (T. chlororhynchos) breeding at Gough Island, so that birds from these localities may face different threats at sea. Our study is the first to highlight key feeding areas for Indian Yellow-nosed Albatrosses from PEI and to demonstrate partitioning of foraging grounds by Yellow-nosed Albatrosses from different localities.

Differential bioaccumulation of mercury by zooplankton taxa in a mercury-contaminated reservoir Guizhou China

Mercury (Hg) contamination in aquatic systems remains a global concern with the biomagnification of methylmercury (MeHg) through primary consumers (zooplankton) to fish and humans. In this study, total mercury (THg) and MeHg concentrations were analyzed in zooplankton collected from Baihua reservoir (Guizhou Province, China). Our results demonstrated that THg and MeHg concentrations were strongly correlated to zooplankton community and biomass composition. The THg concentration was significantly higher in micro-zooplankton compared to meso-zooplankton and macro-zooplankton, and MeHg concentration increased significantly as body size increased. Hg increases in zooplankton were influenced by the numbers of calanoid copepods and Daphnia present relative to phytoplankton and zooplankton biomass. Many zooplankton taxa in the three size-fractions were affected by THg exposure. The biomasses of Bosmina longirostris, Thermocyclops brevifurcatus, Asplanchna priodonta and Cyclops vicinus vicinus were positively correlated with Hg accumulation, while Daphnia hyalina, and Phyllodiaptomus tunguidus had a negative association. THg and MeHg bioaccumulation factors were correlated with phosphorus and total nitrogen concentration, zooplankton biomass, and chlorophyll-a concentration. Phosphorus loading was associated with increased THg and MeHg accumulation in the zooplankton highlighting biomagification with eutrophication. Chlorophyll-a levels were not correlated to THg and MeHg accumulation in zooplankton when phytoplankton densities were >107 cells L−1 and chlorophyll-a concentrations <9 μgL−1. This finding contradicts the idea of MeHg biodilution with increased algae biomass. However, changes in the phytoplankton species and biomass altered the availability of food for zooplankton, particularly micro-zooplankton and macro-zooplankton. Ultimately, the bioaccumulation of MeHg and THg across lower trophic levels was based more on the availability of preferred food resources than on total biological productivity.

Mesopelagic Prokaryotes Alter Surface Phytoplankton Production during Simulated Deep Mixing Experiments in Eastern Mediterranean Sea Waters

Mesopelagic prokaryotes (archaea and bacteria), which are transported together with nutrient-rich intermediate-water to the surface layer by deep convection in the oceans (e.g., winter mixing, upwelling systems), can interact with surface microbial populations. This interaction can potentially affect production rates and biomass of surface microbial populations, and thus play an important role in the marine carbon cycle and oceanic carbon sequestration. The Eastern Mediterranean Sea (EMS) is one of the most oligotrophic and warm systems in the world’s oceans, with usually very shallow winter mixing (<200 m) and lack of large-size spring algal blooms. In this study, we collected seawater (0-1500 m) in 9 different cruises at the open EMS during both the stratified and the mixed seasons. We show that the EMS is a highly oligotrophic regime, resulting in low autotrophic biomass and primary productivity and relatively high heterotrophic prokaryotic biomass and production. Further, we simulated deep water mixing in on-board microcosms using Levantine surface (LSW, ~0.5 m) and intermediate (LIW, ~400 m) waters at a 9:1 ratio, respectively and examined the responses of the microbial populations to such a scenario. We hypothesized that the LIW, being nutrient-rich (e.g., N, P) and a ‘hot-spot’ for microbial activity (due to the warm conditions that prevail in these depths), may supply the LSW with not only key-limiting nutrients but also with viable and active heterotrophic prokaryotes that can interact with the ambient surface microbial population. Indeed, we show that LIW heterotrophic prokaryotes negatively affected the surface phytoplankton populations, resulting in lower chlorophyll-a levels and primary production rates. This may be due to out-competition of phytoplankton by LIW populations for resources and/or by a phytoplankton cell lysis via viral infection. Our results suggest that phytoplankton in the EMS may not likely form blooms, even after exceptionally deep winter mixing, and therefore have a very small overall effect on the vertical flux of organic matter to the deep sea.

Identifying Distribution of Chlorophyll-a Concentration Using Landsat 8 OLI on Marine Waters Area of Cirebon

Phytoplankton is a microscopic plant that has a function to produces oxygen and organic substances. It also plays a role as a main producer in the food chain of a marine ecosystem. Chlorophyll-a is a colour pigment most common in phytoplankton species, so that the concentration level of chlorophyll-a can be used as an indicator of the abundance of phytoplankton cells, and as a reference for predicting organic potency in the aquatic area. This research discusses about the spatial and temporal distribution of chlorophyll-a and its correlation with salinity and total suspended solid (TSS), in the seawaters of Cirebon, West Java. The goal of this research is to be a source of information for fishermen, and other stakeholders whose related subjects in the field of marine and fisheries to predict fertile water regions and can also be used as an indicator in discovering potential areas to catch pelagic fish in Cirebon seawaters. Chlorophyll-a concentration, salinity, and TSS are identified using remote sensing data such as Landsat-8 OLI multi temporal images according to dry and wet month parameters in the 2014-2015. The results of the processed image are then validated between in-situ measurements in the field and remote sensing imagery at the same time. This research utilizes descriptive analysis, and statistics with spatial approach. The results of the research show that temporally, chlorophyll-a levels have a tendency to be higher in wet months compared to dry months, while chlorophyll-a is higher in areas near the coastline compared to open sea areas. The distribution of chlorophyll-a concentration is affected by salinity and TSS distribution, where salinity has the negative relationship and TSS has the positive relationship with chlorophyll-a distribution.

The establishment of season-specific eutrophication assessment standards for a water-supply reservoir located in Northeast China based on chlorophyll-a levels

Eutrophication has become the primary problem facing most surface water bodies worldwide, especially when the water body serves as a water supply source. Substantial efforts have been made to prevent and control eutrophication from decades ago. Among them, the establishment of eutrophication assessment standards was rather essential. However, until now, there is no authoritative standard established for the assessment of eutrophication level in developing countries such as in China. For water bodies located in the Northeast China, the level of chlorophyll-a (Chl-a), which is proportional to phytoplankton biomass, tends to be subjected to evident seasonal variations as the phytoplankton biomass and species composition are greatly impacted by the seasonally alternated climate, hydrology and pollutants source, which in turn complicated the eutrophication problem. The establishment of season-specific eutrophication assessment standards was thus extremely significant for water bodies located in regions with large air temperature variations. In this study, water quality parameters were detected over five consecutive years (2011–2015) to assess the seasonal trophic state of a water-supply reservoir located in Northeast China. Bivariate and multiple regression were performed between Chl-a and other water quality parameters in different seasons. The trophic state of each season was evaluated by the comprehensive trophic level index and the season-specific eutrophication assessment standards were established. The results showed that phosphorus was the predominant limiting nutrient of eutrophication and the Chl-a levels were seasonally different. The reservoir was generally in a light-eutrophic state. Mesotrophic assessment standards were established for spring, summer and autumn and light-eutrophic assessment standards for autumn based on the water quality data collected. As the predominant nutrient, the concentrations of total phosphorus for the mesotrophic state for spring, summer and autumn were 0.044, 0.028 and 0.038mg/L, respectively. Moreover, as shown by the mesotrophic and light-eutrophic standards of the autumn, the discrepancy of different parameters between the standards of different trophic level was were not necessarily varied in the same trend. In conclusion, the establishment of season-specific eutrophication standards for water bodies located in regions with large air temperature variations was significant for scientific trophic state evaluation and effective eutrophication control.

Water and sediment quality in Cartagena Bay, Colombia: Seasonal variability and potential impacts of pollution

Cartagena Bay, one of the Caribbean's hot spots of pollution, is an estuarine system connected to the Caribbean Sea by two straits. Large freshwater discharges from the Dique Canal into the south of the bay produce estuarine conditions strongly related to the seasonal variability of runoff from the Magdalena River watershed. The bay's seasonal conditions may be characterized by three seasons: strong winds/low runoff (Jan.–April), weak winds/intermediate runoff (May–Aug.), and weak winds/high runoff (Sept.–Dec.). This coastal zone is known to be impacted by land-based sources of pollution, including continental runoff, industrial effluents and domestic wastewater. However, previous studies have not sufficiently ascertained the spatio-temporal extent of this pollution. This study addresses the following research question: What is the current extent of water and sediment pollution in Cartagena Bay and which factors control its seasonal variability? Monthly seawater samples (Sept.2014–Aug.2015) were taken from surface and bottom depths at 16 stations in and around Cartagena Bay and analyzed for physical, chemical, and biological parameters. Surface sediments were sampled from the bay's bottom every three months and analyzed for various trace metals. Seasonal variability was observed in nearly all of the water quality parameters, with higher concentrations usually coinciding with the high runoff season. Potential pollution impacts are shown by wet-season averages of total suspended solids (45.0 ± 89.5 mg/l), turbidity (26.1 ± 59.7 NTU), biological oxygen demand (1.20 ± 0.91 mg/l), chlorophyll-a (2.47 ± 2.17 μg/l), nitrate (171.1 ± 112.6 μg/l), phosphate (43.1 ± 63.5 μg/l), total phosphorus (85.3 ± 77.2 μg/l), phenol (2.9 ± 17.4 mg/l), faecal coliforms (798 ± 714 MPN/100 ml) and enterococci (32 ± 30 CFU/100 ml) in excess of recommended threshold values for marine conservation and recreational adequacy. The bay's hypoxic conditions are evident with low dissolved oxygen concentrations (<4 mg/l) found at bottom depths during the wet season, moderate concentrations in the windy season, and low concentrations approaching surface waters during the transitional season, showing a seasonality related to the variability of water circulation and vertical stratification. Lower chlorophyll-a levels found in the water column during the wet season suggest that primary productivity in this eutrophic system is not limited by nutrients, which are abundant due to land-based effluents, but rather by water transparency which is significantly reduced during the wet season due to large sediment loads discharged from the Dique Canal. Sediments from the bay's bottom were found to have concentrations of mercury, cadmium, chromium, copper and nickel in excess of the Threshold Effects Levels (TEL) used as an indicator of potential impacts on marine life.