TRIX Index Research Articles

Environmental DNA metabarcoding reveals diverse phytoplankton assemblages and potentially harmful algal distribution along the urban coasts of Türkiye

Marine phytoplankton are widely used to monitor the state of the water column due to their rapid changes in response to environmental conditions. In this study, we aimed to investigate the coastal phytoplankton assemblages, including bloom-forming species using high-throughput sequencing of 18S rRNA genes targeting the V4 region and their relationship with environmental variables along the Istanbul coasts of the Sea of Marmara. A total of 118 genera belonging to six phyla were detected. Among them, Dinoflagellata (36) and Bacillariophyta (26) were represented with the highest number of genera. According to the relative abundance of DNA reads, the most abundant taxa were Dinoflagellata_phylum (18.1%), Emiliania (8.4%), Biecheleria (8.4), and Noctiluca (8.1%). The ANOSIM test showed that there was a significant temporal difference in the assemblages, while the driving environmental factors were pH, water temperature, and salinity. According to the TRIX index, the trophic state of the coasts was highly mesotrophic and eutrophic. In addition, 45 bloom-forming and HAB taxa were detected and two species of Noctiluca and Emiliania, which frequently cause blooms in the area, were recorded in high abundance. Our results provide insight into the phytoplankton assemblages along the urbanized coastlines by analysing the V4 region of 18S rRNA. This data can support future studies that use both traditional methods and metabarcoding, employing various primers and targeting different genes and regions.

Trophic status of a coastal lagoon - marine harbor system: Potential outwelling rates to the Mesoamerican Barrier Reef southern region

Eutrophication is still a serious problem in many coastal areas, including the tropics, where river discharges of nutrients is usually high. The ecological stability and ecosystem services of the Mesoamerican Barrier Reef System (MBRS), the world's second-largest coral reef system, suffer a generalized impact by riverine discharge of sediment and organic and inorganic nutrients, which may lead to coastal eutrophication and a coral-macroalgal phase shift. However, few data exist on the MRBS coastal zone status, particularly in Honduras. Here, two in situ sampling campaigns were carried out (May 2017 and January 2018) in the Alvarado Lagoon and Puerto Cortés Bay (Honduras). Measurements included water column nutrients, chlorophyll-a (Chla), particulate organic and inorganic matter and net community metabolism, completed with satellite images analysis. The lagoon and bay environments are ecologically different systems and present different sensitivities to seasonal changes in precipitation as shown by the multivariate analysis. Nonetheless, net community production and respiration rates were neither different spatially, nor seasonally. In addition, both environments were highly eutrophic as shown by the TRIX index. Thus, the Puerto Cortés system represents an important source of dissolved nutrients and particulate matter to the coastal zone. Even though offshore, water quality, based on estimated outwelling rates from the Puerto Cortés system to the coastal waters of the southern MRBS region, improved considerably, concentrations of Chla and nutrients remained higher than those typically measured in non-polluted coral reefs in the Caribbean region and the suggested threshold values. In situ monitoring and assessment of these aspects are crucial to evaluate the ecological functioning of and threats on the MBRS, and elaborate and implement adequate policies for integrated management given its regional and global importance.

Assessment of the trophic status in a tropical estuarine system

Estuaries are extremely valuable ecosystems and have been affected by several anthropogenic activities from urban growth and industrial development, such as the release of untreated efuents which decrease water quality. This study aimed to evaluate the seasonal and temporal trophic status variation in the Formoso River Estuarine System (FRES), a tropical estuary. Three campaigns were carried out in each season (rainy and dry), during which surface water was sampled for abiotic parameter analyses. The TRIX index was used for trophic status assessment. For the temporal evaluation, a review of literature addressing the matter in the study area was conducted. Between 2017 and 2018, the TRIX index varied from a mean of 6 ± 0.2 upstream to 5 ± 0.4 downstream during the rainy season, indicating eutrophic conditions throughout most of the FRES extension, especially near the Formoso River, and from 6 ± 1 to 3 ± 0.8 during the dry season. Temporal analyses showed that in 2002 the overall mean TRIX index was 5.72 ± 0.4, decreasing in 2005 and 2014, and followed by an upwards trend. We conclude that the FRES is impacted by the release of untreated efuents such as sewage and fertilizers from the city of Rio Formoso and from various agricultural activities, which are more intense during the rainy season. Nevertheless, over time there were more critical scenarios pertaining to the trophic status. The present diagnosis reinforces the importance of public sanitation policies in estuarine regions and spatial planning instruments for pollution control in fishery areas.

Environmental assessment of three different sites in shallow environments of La Paz Bay (Gulf of California) using the TRIX index and macroalgae biomass. Part I

Coastal areas are of particular ecological and economic importance as they provide direct and indirect goods and services to society, both biological indicators and water quality assessment are of importance when monitoring these environments. Hydrographical parameters, nutrients, chlorophyll-a, and macroalgae biomass were measured, and the TRIX index was obtained, at three sites of La Paz Bay subjected to different types of anthropogenic influence: San Juan de la Costa (SJC), Casa del Marino (CM), and El Tecolote (TE), during two months of 2017 and four months of 2018. Also, macroalgae blooms at these sites were monitored by sampling the biomass of key species. Temperature showed the typical seasonal variation, from 21 °C in winter to 28 °C in summer, while salinity showed little variation (35–37 psu). Chlorophyll-a varied in parallel with changes in water temperature (0.3–2.4 μg L−1), while nutrients varied depending on the season and site. The TRIX index showed significant differences between seasons, with the highest values in the warmer months (6.0) and the lowest in November (2.7); the sites studied ranged from mesotrophic to oligotrophic. Four macroalgae species accounted for over 60% of the biomass during the sampling period: Ulva ohnoi (16.1 kg), Spyridia filamentosa (6.5 kg), Acanthophora spicifera (4.2 kg), and Ulva sp. 1 (2.7 kg). Ulva, Gracilaria, and Hypnea species showed a positive significant correlation with nutrients and the TRIX index. A high macroalgae biomass may be related to a mesotrophic state, showing its value for determining the health status of coastal ecosystems and issuing proper management recommendations.

Effects of Nutrient Management Scenarios on Marine Eutrophication Indicators: A Pan-European, Multi-Model Assessment in Support of the Marine Strategy Framework Directive

A novel pan-European marine model ensemble was established, covering nearly all seas under the regulation of the Marine Strategy Framework Directive (MSFD), with the aim of providing a consistent assessment of the potential impacts of riverine nutrient reduction scenarios on marine eutrophication indicators. For each sea region, up to five coupled biogeochemical models from institutes all over Europe were brought together for the first time. All model systems followed a harmonised scenario approach and ran two simulations, which varied only in the riverine nutrient inputs. The load reductions were evaluated with the catchment model GREEN and represented the impacts due to improved management of agriculture and wastewater treatment in all European river systems. The model ensemble, comprising 15 members, was used to assess changes to the core eutrophication indicators as defined within MSFD Descriptor 5. In nearly all marine regions, riverine load reductions led to reduced nutrient concentrations in the marine environment. However, regionally the nutrient input reductions led to an increase in the non-limiting nutrient in the water, especially in the case of phosphate concentrations in the Black Sea. Further core eutrophication indicators, such as chlorophyll-a, bottom oxygen and the Trophic Index TRIX, improved nearly everywhere, but the changes were less pronounced than for the inorganic nutrients. The model ensemble displayed strong consistency and robustness, as most if not all models indicated improvements in the same areas. There were substantial differences between the individual seas in the speed of response to the reduced nutrient loads. In the North Sea ensemble, a stable plateau was reached after only three years, while the simulation period of eight years was too short to obtain steady model results in the Baltic Sea. The ensemble exercise confirmed the importance of improved management of agriculture and wastewater treatments in the river catchments to reduce marine eutrophication. Several shortcomings were identified, the outcome of different approaches to compute the mean change was estimated and potential improvements are discussed to enhance policy support. Applying a model ensemble enabled us to obtain highly robust and consistent model results, substantially decreasing uncertainties in the scenario outcome.

Water quality influence the phytoplankton and bacteria abundance: a comparison between shallow freshwater and saltwater ponds

Study for understanding the role of various water quality parameters on phytoplankton and bacteria density in shallow freshwater and saltwater ponds is lacking. Therefore, the present study was conducted to understand the difference in influence of various water quality parameters on phytoplankton and bacteria density in freshwater and saltwater ponds. A series of water quality parameters, phytoplankton biomass (as indexed by chlorophyll-a), the density of bacteria and trophic state (as indexed by TRIX index) were determined monthly in two freshwater and two saltwater ponds located in Kuantan, Pahang, Malaysia. Apart from pond type and temporal effects, multivariate ordinations were performed using two different datasets: water quality, and phytoplankton and benthic macroinvertebrates. Water temperature, salinity, and the concentration of TSS and ammonia were significantly (p 0.05) throughout the study period in both freshwater and saltwater ponds. All ponds under study are oligotrophic. In all ponds, the water quality dataset explained the overall variation in phytoplankton and bacteria abundance quite well. Phytoplankton biomass in freshwater ponds is greatly related with phosphate and slightly related with ammonia and water depth. In saltwater ponds, nitrogenous nutrients (nitrate and ammonia) were strong predictors of phytoplankton biomass and stronger than salinity, TSS and pH. Turbidity was the strongest predictor of bacteria density in freshwater and saltwater ponds. It had strong negative influences on bacteria density in freshwater ponds whereas, it had strong negative influences on bacteria density in saltwater ponds. The results of this study support and emphasize the importance for developing appropriate programs for the monitoring and conservation of various freshwater and saltwater ponds.

Reflectance spectra classification for the rapid assessment of water ecological quality in Mediterranean ports

Summary Ports are open systems with direct connection to the sea, therefore any potential impact on port waters may have implications for the health of adjacent marine ecosystems. European WFD addressed ports in the category of Heavily Modified Water Bodies (HMWBs) and promoted implementation of protocols to monitor and improve their ecological status. TRIX index, which incorporates the main variables involved in the trophism of marine ecosystems (Nitrogen, Phosphorus, Chlorophyll a, Dissolved Oxygen), is widely utilized in European coastal areas to evaluate trophic status. The relationships between the variables involved in TRIX computation, particularly Chlorophyll a concentration, and water spectral reflectance provides an alternative method to evaluate the quality and ecological status of the port water. Hyperspectral (380–710 nm) water reflectance data were recorded by a portable radiometric system in five ports from the Western and Eastern Mediterranean Basin. The spectral distance between samples was measured by two metrics using both the original and reduced spectra and was implemented within a hierarchical clustering algorithm. The four spectral classes that emerged from this operation were statistically analysed versus standard water quality descriptors and phytoplankton community features to evaluate the ecological significance of the information obtained. The results indicated a substantial coherence of different indicators with more than 60% of the total TRIX variability is accounted for by the proposed classification of reflectance spectra. This classification is therefore proposed as a promising Rapid Assessment Technique of ports water ecological quality, which can serve as an effective monitoring tool for sustainable management of ports.

Tropic Status Assesment in Segara Anakan Lagoon, Indonesia : Experience in Applying the Trophic Index Trix

Segara Anakan is a large lagoon, located along the southern coast on western part of Central Java, Indonesia 108° 46’−109° 05’E; 7° 34’−7° 48’S. It has an important ecosystem role as a nursery ground, so that it is important to have further study of the primary productivity. The human activities around the area and natural factors sedimentation has changed the inrush input to the lagoon. Feared, it will influence the change in tropic status of the lagoon, and will cause the average degradation of the primary productivity value. The aim of the research is to explore the study of the primary productivity in Segara Anakan lagoon (SAL) with tropic status assesment. Index TRIX has been used for evaluating long-term trend and spatial trophic pattern in the lagoon with linear combination of the log of 4 state variables: chlorophyll-a, aD%O, macronutrient : Total Nitrogen (TN) and Total phospat (TP). The main objective of this study is to estimating tropic status with spatio-temporal approach. The spatial approach is done on 7 stations (S) with representations: (S) natural factors and (S) the presence of anthropogenic activities. The temporal approach (time series) for a year refers to the monsoon wind pattern (west, transition I, east and transition II) season. The results of laboratory tests are discussed descriptively. Index TRIX assesment in SAL shows that point values, exceeding 6 TRIX units are typical of highly productive coastal waters, where the effects of eutrophication determine frequent episodes of anoxia in bottom waters and indicated by high Habs phytoplankton. The effects of highest rainfall at transition II season, anthropogenic pressure, aquatic hydrodynamics are thought to cause in the increasing of SAL macronutrients which trigger eutrophication of waters. Management and lagoon management strategies are required by the local government, stakeholders and communities to prevent the phenomenon of eutrophication of the lagoon.

Assessing multimetric trophic state variability during an ENSO event in a large estuary (Río de la Plata, South America)

During the “El Niño”- Southern Oscillation (ENSO) event 2009–2010, trophic state uni (TSI’s) and multimetric (TRIX’s) indexes were determined in the north coast of the Río de la Plata (RdlP). The relationships of such indexes with the hydrological, physical and chemical parameters were explored to identify climatic variability or anthropogenic effects on the eutrophication process. Eleven oceanographic sampling campaigns at 25 stations were conducted along the north coast of RdlP from 2009 to 2011. Temperature, salinity and oxygen saturation, water transparency (Secchi depth), chlorophyll (Chl a) content and total nutrient concentrations (total nitrogen and phosphorous) were determined. Trophic indexes (TSI Chl a, TSI TP, TRIX NP-Voll. and TRIX NP-Mvdeo.) were quantified and the RdlP flow was measured. RdlP flow showed significant differences between ENSO phases, with higher values during “El Niño” (EN), negative and significant correlations with salinity, Secchi depth and positive with total nutrients. The trophic status indexes showed spatial and temporal variability and associations with flow, physical and chemical parameters. Trophic state indexes showed spatial and temporal heterogeneity and were strongly associated to environmental conditions (hydrological and seasonal oscillations) during the study period but also to the anthropogenic factors affecting the north coast of RdlP. The system has been classified as mesotrophic to hypertrophic, depending on the selected indicator. According to these results, we suggest the use of a multimetric trophic state indicator, i.e., the TRIX index, as explains better the causes and effects of the eutrophication processes. To implement the TRIX index, (TRIX NP-Mvdeo.) we suggest researchers to consider a large number of local records (Chl a, nutrients, oxygen) at seasonal scales. This index is adapted to the environmental conditions of the study zone and complemented with other community structure indexes, and should be used for eutrophication assessment programs in the north coast of RdlP.

Distributions of dissolved inorganic nitrogen to estimate trophic state in Jakarta Bay

Jakarta Bay is a coastal area that receives a lot of organic material input from rivers in Jakarta. The organic material is decomposed into nutrients and has implications for increasing the trophic state of Jakarta Bay. The aims of this study are to analyze the spatial distribution of dissolved inorganic nitrogen (DIN) and to estimate the trophic state of Jakarta Bay. The study was conducted from July to October 2017. Spasio-temporal distribution analysis of nitrogen was carried out with ArcGIS 10.4.2. Estimation of trophic state used TRIX Index. Ammonia and DIN distribution tends to be higher in the river mouth and in the middle of the bay, nitrite was higher in the eastern part of the bay and river mouth, while nitrates tend to be higher in the eastern part of the bay to the middle waters. Trophic state of Jakarta Bay can be divided into three trophic status, hypertrophic in coastal area, eutrophic in the middle of the bay, and mesotrophic in the high seas.

Long-Term Dynamic in Nutrients, Chlorophyll a, and Water Quality Parameters in a Coastal Lagoon During a Process of Eutrophication for Decades, a Sudden Break and a Relatively Rapid Recovery

Coastal lagoons are considered among the marine habitats with the highest biological productivity, and support a great variety of human activities and pressures that make them especially vulnerable to trophic imbalances. While dystrophic crises are common in many lagoons, others like the Mar Menor show homeostatic mechanisms, high resilience, and clear waters. This paper analyses the water column descriptors dynamic during the last 22 years in this coastal lagoon, in the context of a eutrophication process produced by an increase in nutrient inputs, mainly derived from agriculture. Despite water column nitrate concentration increased by one order of magnitude, the lagoon maintained homeostatic regulation for two decades, keeping the water transparency and relatively low levels of nutrients and chlorophyll a (Prebreak phase), followed by a sudden change of state in 2016 with an abrupt increase in average nutrients and chlorophyll a concentration and loss of water transparency (Break phase), and a relatively rapid recovery after the reduction of nutrient discharges (Recovery phase). The activation of the regulation mechanisms seems to manifest through an ammonium production in the water column, as a consequence of the activity in the trophic web. The low correlation between chlorophyll a and nutrients concentration, mainly at small spatio-temporal scales, is in disagreement with eutrophication traditional models, and suggests a rapid response of primary producers to nutrient inputs and a zooplankton control in the short-term, which in turn is controlled by the rest of the trophic web components. Homeostatic properties that in the Mar Menor lagoon have provided resistance to eutrophication are based on several mechanisms: channeling its production toward the benthic system (maintaining high biomasses of primary producers, filter feeders, and detritivores), a top-down control of the pelagic trophic web exerted by ichthyoplankton and jellyfish, and exporting surplus production outside the system. Resilience of the system would be based on the high turnover in the species composition related to the restricted connectivity to the sea, the spatio-temporal variability of the environmental conditions, and the multiplicity of spatial–temporal scales involved in lagoon processes. TRIX index was sensitive to the trophic and water quality changes. However, in our study, its current score does not allow to anticipate or alert the eutrophication risk and the trophic breakpoint of the system.

POTENTIAL ENVIRONMENTAL IMPACTS OF TUNA CAGE FARMING IN THE AEGEAN SEA

The present study aimed to investigate the potential impacts of Atlantic Bluefin Tuna ( Thunnus thynnus ) farming in offshore cage systems in the Aegean Sea (Sigacik Bay-Izmir, Turkey), in respect to physico-chemical water quality parameters, nutrient loads, chlorophyll- a , total suspended solids, zooplankton groups, and TRIX index calculations for the potentially affected cage farm area and an unaffected reference site. Concentrations of physico-chemical variables (temperature, salinity, dissolved oxygen, pH) in the study carried out in May and August 2018, were within the acceptable limits for marine aquaculture in terms of water quality characteristics. The concentrations of PO 4 -P, NH 4 -N, and NO 2 -N showed no temporal or spatial changes, and were recorded below 0.01 mg/L (<0.01) for PO 4 -P and NH 4 -N, whereas lower than 0.005 mg/L (<0.005) for NO 2 -N values in both cage and reference stations in May and August 2018 periods. Results showed low levels of TSS (0.33-11.87 mg/L), both in the cage farm area and the reference site, remaining below the general quality criteria of 30 mg/L for marine environment. No eutrophication risk (TRIX index, T<4 ) was observed around the Tuna Cage Farm Site in Sigacik Bay, according to the legislations enacted for “Sensitive Areas of Enclosed Bays where fish farms are not allowed”. Based on these findings, demonstrating highly interactive trophic level variability, it can be concluded that the impacts of the Tuna Cage Farm were not significant, possibly due to the consistent movement of the water in currents in the study area.

Trophic state of an urban coastal lagoon (northern Brazil), seasonal variation of the phytoplankton community and environmental variables

Jansen Lagoon is an urban coastal area formed by damming the Ana Jansen Creek, which is located in the northwest of São Luis Island (northern Brazil) and is influenced by semidiurnal macro-tides. This study aimed to characterize the seasonal variation of the phytoplankton communities and its relationship with environmental variables to determine the trophic conditions in the Jansen Lagoon. Samples were collected bimonthly in five fixed sites in 2011 and 2012 to analyze biological and physicochemical data. A total of 55 taxa were identified including Bacillariophyta (25), Cyanobacteria (17), Chlorophyta (5), Charophyta (2), Euglenophyta (4) and Miozoa (2). The Closterium setaceum, Pleurosigma elongatum e Oscillatoria sp3 occurrence had a positive correlation with the higher rainfall period, increase in dissolved oxygen concentrations and nutrients (DIP and NO2−) and elevated trophic levels (TRIX). Cyclotella stelligera and Microcystis aeruginosa were strongly correlated with chlorophyll a concentration (microphytoplankton) under turbidity and wind speed influence. The trophic state of Jansen Lagoon ranged from eutrophic to hypereutrophic according to the TRIX index, and this poor water quality is explained by an intense eutrophication process in the rainy season due to elevated nutrient availability. Hence, to change the scenario presented in this study the reduction of point and non-point sources is necessary to slow down the eutrophication and growth of algal blooms in Jansen Lagoon.

SỬ DỤNG CÁC CHỈ SỐ ĐỂ ĐÁNH GIÁ CHẤT LƯỢNG NƯỚC VÀ PHÂN LOẠI MỨC ĐỘ PHÚ DƯỠNG CỦA VÙNG NƯỚC VEN BIỂN QUẢNG NINH - HẢI PHÒNG

With the fast economic growth and the loose management of pollutants discharged into the sea, the Quang Ninh - Hai Phong coastal water faces the risk of contamination of toxic subtances; and the eutrophication can occur. Therefore, coastal water quality was monitored at Tra Co, Cua Luc and Do Son in 2015. The results showed that sea water had the higher concentration of nitrate and 4.4’DDD compared to limit values. RQ coefficient of coastal areas was medium (0.25 &lt; 0.562 &lt; 0.75), hence “environmental safety”. According to the SWQI index, the water quality in three stations was good and not polluted. In terms of eutrophication level classification according to OECD (1982), the water body of all stations was mesotrophic. According to classification by TRIX index, only water body of Do Son station was in a state of eutrophication, that of the remaining stations was mesotrophic.

Assessment of the Trophic Status of the South Lagoon of Tunis (Tunisia, Mediterranean Sea): Geochemical and Statistical Approaches

The trophic status assessment of the South Lagoon of Tunis, a shallow Mediterranean coastal area after its restoration, is addressed herein with respect to its various environmental settings which are taken as indicators of water quality. The lagoon had, in the past, witnessed severe environmental quality issues. To resolve these problems, a large restoration project of the lagoon was undertaken which consisted of dredging the bottom sediments removing areas of water stagnation and improving water circulation. After this restoration work, the lagoon morphology has radically changed. In this paper, we attempt to evaluate the lagoon water’s trophic state to analyze the eutrophication risk after almost 16 years. In order to achieve these purposes, two water quality monitoring campaigns were conducted (July 2013 and February 2014). Natural and anthropogenic factors controlling the nutrient content of the lagoon water have been assessed through both geochemical methods and multivariate statistical tools. The results show that the nutrients are from external sources due to the discharge of municipal and industrial wastewater from the surrounding city of the catchment in the lagoon’s south side. According to the TRIX index, the lagoon remains eutrophic presenting a “poor” water quality, notwithstanding the engineering project due to the high level of nutrients.

Trophic Status of the Dniester Delta Lakes in 2006-2017

Purpose. Assessment of trophic status of the Dniester deltaic part lakes (Bile, Svine, Tudorovo and Putrino) in 2006-2017. Methods. Determination of hydrological, hydrochemical and hydrobiological characteristics of the lakes aquatic environment has been performed using standard methodologies. Three indicators of eutrophication have been used: chlorophyll a concentration, number of bacterioplankton, trophic indices TSI and TRIX. Results. Peculiarities of physicochemical characteristics of water in the Dniester deltaic lakes have been analysed. Increased nutrients concentration has been revealed in all the lakes during past 12 years. The lowest oxygen content and oxygen saturation was established in water of the Putrino Lake, where at the same time the highest concentrations of total nitrogen and phosphorus were observed. Analysis of long-term changes of chlorophyll a and bacterioplankton has been done. Based on the lakes integrated study in summer time of 2006-2017, assessment of water trophic state has been for the first time performed for each deltaic lake. Statistical interrelations between trophic state indicators and physicochemical characteristics of the lakes have been revealed. Conclusions. It was established that the assessment of four deltaic lakes trophic status based on chlorophyll a, bacterioplankton and TSI trophic index practically coincided and evidenced increased of the lakes’ trophic status and decrease of water quality in 2012-2017 compared with previous years. All the eutrophication indicators in water of the lakes Svine, Tudorovo and Putrino during six last years corresponded to hypertrophic status, while in the Bile Lake most of eutrophication indicators were lower and corresponded to eutrophic status. Trophic index TRIX, which was developed for seawater assessment, practically always showed somewhat higher trophic status of the lakes than other indicators.

A new technique for rapid assessment of eutrophication status of coastal waters using a support vector machine

There is an urgent need to develop efficient evaluation tools that use easily measured variables to make rapid and timely eutrophication assessments, which are important for marine health management, and to implement eutrophication monitoring programs. In this study, an approach for rapidly assessing the eutrophication status of coastal waters with three easily measured parameters (turbidity, chlorophyll a and dissolved oxygen) was developed by the grid search (GS) optimized support vector machine (SVM), with trophic index TRIX classification results as the reference. With the optimized penalty parameter C =64 and the kernel parameter γ =1, the classification accuracy rates reached 89.3% for the training data, 88.3% for the cross-validation, and 88.5% for the validation dataset. Because the developed approach only used three easy-to-measure variables, its application could facilitate the rapid assessment of the eutrophication status of coastal waters, resulting in potential cost savings in marine monitoring programs and assisting in the provision of timely advice for marine management.

Real-time eutrophication status evaluation of coastal waters using support vector machine with grid search algorithm

The development of techniques for real-time monitoring of the eutrophication status of coastal waters is of great importance for realizing potential cost savings in coastal monitoring programs and providing timely advice for marine health management. In this study, a GS optimized SVM was proposed to model relationships between 6 easily measured parameters (DO, Chl-a, C1, C2, C3 and C4) and the TRIX index for rapidly assessing marine eutrophication states of coastal waters. The good predictive performance of the developed method was indicated by the R2 between the measured and predicted values (0.92 for the training dataset and 0.91 for the validation dataset) at a 95% confidence level. The classification accuracy of the eutrophication status was 86.5% for the training dataset and 85.6% for the validation dataset. The results indicated that it is feasible to develop an SVM technique for timely evaluation of the eutrophication status by easily measured parameters.

Space time evolution of the trophic state of a subtropical lagoon: Lagoa da Conceição, Florianópolis Island of Santa Catarina, Brazil

ABSTRACT High levels of eutrophication in coastal lagoons due to human activity have been documented worldwide. Among the main impacts observed are anoxia, hypoxia, toxic algal blooms, fish kills, loss of biodiversity and loss of bathing. This study aimed to evaluate the evolution of the trophic state of Lagoa da Conceição, a subtropical lagoon located in an urbanized watershed on the island of Santa Catarina - Brazil. Spatio temporal patterns of stratification and eutrophication were investigated to understand the main biochemical changes over time. The water quality data were obtained from field campaigns supplemented with literature of the last 15 years. The vertical structure of the water column and the trophic state were evaluated by the stratification index and the TRIX index, respectively. Analyses of variance were performed in order to identify possible temporal variations in vertical stratification and trophic level. Eutrophication effects on biogeochemical cycles were verified through a multi-dimensional cluster analysis (MDS) and correlations between variables related to physical, chemical and biological processes were verified by principal component analysis (PCA). The results showed that the water column is homogeneous in all regions except in the central region of the lagoon, and the highest ammonia concentrations and lowest dissolved oxygen concentrations with periods of anoxia are observed in bottom waters. The study looked at the high trophic level of the lagoon and its inability to process the biogeochemical changes imposed by urban development.

Evaluation of Water Variables in No-Take Zone of Ustica Marine Protected Area (Southern Tyrrhenian Sea)

ABSTRACT In this research, the seasonal fluctuations of the main water variables in the no-take area (A zone) of the Ustica MPA were investigated. This study aims to monitor the water quality of the Ustica MPA, to analyze all the hydrological parameters useful to the physical-chemical characterization of water and to use TRIX index to characterize the trophic level of the coastal marine area. The final results shown that Ustica is an area of relevant environmental and ecological value and is a good example of a Marine Protected Area, which is not excessively affected by the human presence even during the touristic season. This study represents the first records based on well-organized protocol in order to assess water column characteristics of the studied area. This paper could be used as a reference document for future studies regarding the same or similar areas.