Assessment of the trophic status in a tropical estuarine system

Abstract

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.

Descriptors: Water quality; Dissolved inorganic nutrients; Multivariate index; Environmental impacts

INTRODUCTION

Estuaries are complex and dynamic hydrological environments and are considered one of the most productive areas in the biosphere (Gattuso et al., 1998; Borges, 2011; Filho et al., 2020). This ecosystem is rich in organic matter, solutes, and nutrients, representing an important site for material exchange with the atmosphere, associated wetlands, and especially the ocean, due to the marine-freshwater interaction. Estuarine systems also provide a nursery for several organisms such as fish assemblages and thus represent an area of social importance, especially considering the local artisanal fisher population (Vasconcelos et al., 2011; Dantas et al., 2012; Whitfield, 2017).

Rising urbanization and land use are major threats to coastal environments worldwide (Hader et al., 2020). Estuaries have been directly affected by anthropogenic activities, including the release of fertilizer and untreated sewage (Alves et al., 2013; Cabral and Fonseca, 2019). These efuents are loaded with organic nutrients, especially nitrogen and phosphorus, and are generally associated with heavy metals and other potential pollutants (Clark et al., 2017; Zhang et al., 2017; Chen et al., 2021).

From the mid-twentieth century until recently, the loads of reactive nutrients of anthropogenic origin reaching estuarine systems increased significantly. For instance, nitrogen and phosphorus input increased from 34 Tg N yr^-1 to 64 Tg N yr^-1 and from 5 Tg P yr^-1 to 9 Tg P yr^-1 (Beusen et al., 2016; Malone and Newton, 2020), significantly impacting water quality and especially the eutrophication process (Guenther et al., 2014). Harmful algae bloom (HAB) triggered by an increased nutrient input is characteristic of this, causing dissolved oxygen depletion, creating dead zones that impact local biota through community phase shifts, and an increase in mortality of fishes, crustaceans, and several calcifying organisms (Barros et al., 2017; Lemasson et al., 2017; Morelli et al., 2018). Such impacts may be greater in regions highly influenced by seasonality, as is the case for tropical estuaries (Gaspar et al., 2018; Taillardat et al., 2020).

Estimates indicate long-term ecological and economic impacts for eutrophicated estuaries through the end of this century, with losses in excess of US$1 billion annually in several sectors such as recreational water use and fishing (Dodds et al., 2009; Schoen et al., 2017). Because of this, several modeling and multiparameter indices were designed to measure and determine the trophic status of coastal marine environments, as tools for water quality monitoring and improvement (Vollenweider et al., 1998; Vargas-Gonzáles et al., 2014).

In this study, we aimed to assess temporal and seasonal variations in the trophic status of the Formoso River Estuarine System (FRES), northeast Brazil, using TRIX as a multivariate index. We test the hypotheses that the system’s trophic status significantly increases during the rainy season, and that there has been an improvement in water quality over the years.

METHODS

Study area

The FRES is located in Northeastern Brazil (8º37’45.34’’S, 35º05’04.33’’W to 8º44’02.85’’S, 35º06’17.06’’W), state of Pernambuco. It is part of the Guadalupe Marine Protected Area (EPAG), which spans more than 120 km² and was created to protect and conserve the rich local biodiversity and water resources as well as to improve the quality of life of the local community, which relies mostly on subsistence fishing (Lima, 2016; Pinto, 2016).

The climate in the area is wet tropical, with a rainy and dry season spanning from March to August and September to February, respectively. Annual mean precipitation is 1977 mm, of which 76% occurs during the rainy season. The estuarine system is a 27.24 km² hydrographic basin (Lira et al., 1979; Silva et al., 2009). It is composed of three main coastal rivers: the Formoso River and Passos River in its upstream portion and the Ariquindá River as the main tributary in its downstream portion, resulting in a main channel 12km in extension (Figure 1) and a mean flow rate of 4.95 m³ s^-1, which significantly increases during the rainy season (Lira et al., 1979).

Figure 1
Study area and sampling strategy. Red plaid areas represent the main urban centers, the blue line is the EPAG boundaries, and black squares are the sampling stations and their respective numbers.

The lower estuary is mainly influenced by seawater and marine ecosystems such as reef barriers and seagrass meadows (Lima, 2016). In contrast, the upper and middle estuaries are characterized by high-density mangrove forests and sediments with more than 20% of organic matter (Lira et al. 1979; Silva et al., 2009), influenced by the urban zone of Rio Formoso city. This city has an area of 222,458 km² and population of over 23,500 inhabitants, for a demographic density of 97.39 inhabitants km^-2. Its nearly 5,000 households rely on farming and fishing activities as a main source of income (IBGE, 2010).

Sampling strategy and data compilation

Between 2017 and 2018, six campaigns were carried out in the FRES: three during the dry season (December 2017, September and December 2018) and three during the rainy season (May and July 2017, July 2018). Seven sampling stations were established along the FRES (Figure 1), with stations 1, 2, and 7 representing the upper estuary, stations 4, 5, 6 the middle estuary, and station 3 the lower estuary. Surface water samples were collected during low tide using a 2-L Niskin bottle to further analyze dissolved inorganic nutrients, dissolved oxygen (DO), and chlorophyll-a (Chl-a). In situ measurements of salinity in surface waters were obtained using an RBR® C.T.D.

A review of literature addressing the hydrology and phytoplankton biomass in the FRES was carried out to assess trophic status and its temporal variability. Only articles, dissertations, and doctorate theses with the same sampling strategy used in this study and all the necessary parameters to calculate the multivariate index of trophic status (TRIX) were included.

Chemical analyses and trophic status assessment

All dissolved inorganic nutrients were analyzed using spectrophotometric methods. Soluble reactive phosphorus (SRP) and reactive silicate (SRSi) were analyzed per Grasshof et al. (1983), with the formation of a blue complex due to the use of ascorbic acid (C₆H₆O₆) as a reducing reagent and analytical errors of 0.008 µmol L^-1 and 0.3 µmol L^-1, respectively. Nitrate (N-NO₃^-) and nitrite (N-NO₂^-) were analyzed as described by following the García-Robledo et al. (2014) sulfanilamide/N-(1-naphthyl)-ethylenediamine method, using vanadium III chloride (VCl₃) in the reduction of NO₃^- to NO₂^-. Ammonium (N-NH₃ + NH₄⁺) followed Bower and Holm-Hansen (1980), in which indophenol blue is produced through the reaction of N-NH₃ + NH₄⁺ with salicylate-hypochlorite, and dissolved inorganic nitrogen (DIN) values were obtained by adding the N-NO₃^-, N-NO₂^-, and N-NH₃ + NH₄⁺ concentrations, with a mean error of 0.02 µmol L^-1.

Chl-a is a direct indicator of phytoplankton biomass and was also analyzed through spectrophotometry according to UNESCO (1966). Dissolved oxygen (DO) was measured through the modified Winkler method (Strickland and Parsons, 1972), using manganese sulfate (MnSO₄) and potassium iodide (KI) to form a precipitate equivalent to the DO concentration, followed by a titration with sodium thiosulfate (Na₂S₂O₃). Its saturation (DO%) was calculated according to the UNESCO table (1973).

The TRIX index was originally used to assess the trophic status of the Adriatic Sea (Vollenweider et al., 1998). It has now been applied to several coastal ecosystems, including estuaries (e.g., Flores-Montes et al., 2011; Seisdedo et al., 2014; Vargas-Gonzáles et al., 2014; Sá et al., 2021; Silva et al., 2021). Here, this index was calculated according to the Vollenweider et al. (1998) equation, based on Chl-a, DO%, DIN, and SRP values:

(1) $TRIX=\left({\log }_{10}\left[Chl-1\times DO\%\times DIN\times SRP\right]+k\right)m$

In which Chl-a, DIN, and SRP are expressed in µg L¹ and k and m are constants to adjust the TRIX against a eutrophication scale of 0 to 10, with values of 1.5 and 1.2, respectively. The classification of the trophic status and water quality followed Vollenweider et al. (1998) (Table 1).

Table 1
TRIX classification, following Vollenweider et al. (1998).

TRIX	Trophic status	Water quality
0 ≤ 4	Oligotrophic	High
> 4 ≤ 5	Mesotrophic	Good
> 5 ≤ 6	Eutrophic	Bad
> 6	Hypereutrophic	Poor

Complementary data and statistics

Recent (2017 to 2018) and historical (1970 to 2018) rainfall data were obtained from the Pernambuco Water and Climate Agency (APAC). Because data were not normally distributed and lacked homoscedasticity, analyses were carried out using non-parametric tests. The Spearman test was used to investigate correlations between measured parameters, and a Kruskal-Wallis test was used to analyze seasonal and temporal differences. In all cases, a significance level of p < 0.05 was used. General mean distribution was presented when a parameter was not significantly different between seasons.

RESULTS

Rainfall

In 2017, rainfall patterns varied significantly between seasons (p < 0.05). The annual accumulation was 2,740 mm, with May, June, and July accounting for 66%, varying significantly (p < 0.05) from their respective historical means (Figure 2). During 2018, most of the months were below historical levels, and no significant seasonal differences were detected (p > 0.05), with an overall monthly mean of 144 ± 121 mm.

Figure 2
Monthly rainfall data from the Rio Formoso city meteorological station. Light and dark gray bars represent data from 2017 and 2018, respectively. Black bars represent the historical mean from 1970 to 2018.

Salinity and DO

In the FRES, salinity increased downstream across the entire sampling period (Figure 3a, b), exhibiting significant seasonal differences (p < 0.05). During the rainy season, values ranged from a mean 6 ± 5 g kg^-1 close to the Formoso River to 24 ± 8 g kg^-1 in the lower estuary (Figure 3a) and were negatively correlated with precipitation (rs = -0.47, p < 0.05). During the dry season, the distribution was homogenous throughout most of the FRES, with a lower mean of 12 ± 10 g kg^-1 recorded upstream (Figure 3b). DO was positively and significantly correlated with salinity (rs > 0.4, p < 0.05), with no intra-season variation, an overall minimum of 99 ± 48 µmol kg^-1, and a maximum of 219 ± 29 µmol kg^-1 (Figure 3c).

Figure 3
Mean salinity distribution in the FRES during the rainy (a) and dry (b) seasons, and overall DO (c).

Trophic status

Dissolved inorganic nutrients were negatively correlated with salinity (rs = < -0.5, p < 0.05). Their respective means are summarized in Table 2. DIN, SRP, and SRSi exhibited seasonal differences (p < 0.05) and a similar spatial distribution, with higher concentrations upstream during the rainy season, especially in July 2017, decreasing according to seawater influence (Table 2).

Table 2
Minimum, maximum, and mean concentrations of DIN, SRP and SRSi in the FRES, according to season and location.

Nutrient	Estuary	Season
		Dry			Rainy
		Min	Max	Mean	Min	Max	Mean
DIN (µmol L-1) n = 42	Upper	0.02	13.7	0.31	2.23	30.5	4.87
	Middle	0.03	1.21	0.18	1.32	27.1	6.25
	Lower	0.24	0.55	0.36	1.27	4.28	1.99
SRP (µmol L-1) n = 42	Upper	0.01	0.69	0.07	0.03	1.07	0.25
	Middle	0.01	0.42	0.06	0.02	0.74	0.17
	Lower	0.01	0.34	0.07	0.05	0.19	0.11
SRSi (µmol L-1) n = 42	Upper	1.4	176.8	23.58	7.42	158.0	50.66
	Middle	5.1	81.2	27.18	24.7	121.6	60.29
	Lower	12.5	27.6	21.04	21.3	53.4	30.11

For Chl-a, the highest mean of 7 ± 5 µg L^-1 was obtained next to the Formoso River, and the lowest of 3 ± 1 µg L^-1 was recorded downstream (Figure 4a), with a significant positive correlation with SRSi (rs > 0.3, p < 0.05) and no significant seasonal differences. Following this spatial distribution pattern, the TRIX index varied from a mean of 6 ± 0.2 to 5 ± 0.4 during the rainy season (Figure 4b), indicating a eutrophic status in most of the FRES, and from 6 ± 0.9 to 3 ± 0.8 in the dry season (Figure 4c). Both Chl-a and TRIX values were positively correlated with rainfall (rs > 0.4, p < 0.05) and negatively correlated with salinity (rs > 0.5, p < 0.05) during all sampled periods.

Figure 4
Overall mean Chl-a distribution (a) in the FRES, and seasonal TRIX mean during the rainy (b) and dry (c) seasons.

In addition to the data provided herein, an additional three studies (Silva et al., 2009 Grego, 2010; Lima, 2014) conducted in the FRES were identified, which allowed us to evaluate temporal TRIX variations (Figure 5). Significant temporal changes were observed (p < 0.05). In 2002, TRIX values ranged from 5 downstream to 6 upstream, with an overall mean of 6 ± 0.4. In the three years that followed, the TRIX decreased to 4.5 ± 0.5. No data is available between 2006 to 2013. In 2014, an overall mean of 4 ± 0.65 was reported, which increased to > 5 by 2017, followed by a decreasing trend (Figure 5).

Figure 5
Box plot of TRIX variation over time in the FRES. Horizontal lines represent TRIX values of 4, 5, and 6, corresponding to mesotrophic, eutrophic, and hypereutrophic conditions, respectively.

DISCUSSION

Seawater intrusion in an estuarine system is a determinant factor for local biotic and abiotic processes, acting mainly by diluting solutes, influencing biota distribution, oxygenating the water, and consequently regulating its quality (Santiago et al., 2010; Guenther et al. 2014; Lima, 2016). The FRES is classified as well-mixed, and its geomorphology results in euryhaline conditions throughout most of its extension, especially in periods of low river discharges (Lira et al., 1979; Batista and Flores-Montes, 2013), as in the dry season (Figure 3b).

Seasonality is an important factor for abiotic and biotic parameters in the FRES by regulating the distribution and abundance of phytoplankton and zooplankton, salinity, organic matter and nutrient concentrations in the water according to precipitation levels (Silva et al., 2009; Santos, 2016; Costa et al., 2018). During the rainy season, the influx of terrestrial nutrients and freshwater into coastal waters increases significantly due to an intensification in continental runoff resulting from precipitation, which lowers water salinity (Figure 3a), increases concentrations of dissolved inorganic nutrients in estuarine systems, and thus increases Chl-a levels (Cordeiro et al., 2018; Rubio-Cisneros et al., 2018; Silva et al., 2021). This process may be intensified by climatic events such as the El Niño-Southern Oscillation (ENSO), which can trigger temperature and precipitation anomalies (Sathicq et al., 2015; Andrade et al., 2016).

During 2017, a moderate La Niña was reported, which may have led to higher precipitation rates in northern and northeastern Brazil (Grimm, 2004; Andreoli and Kayano, 2007; Grimm and Tedeschi, 2009; Rodrigues et al., 2017). This could explain the precipitation above historical levels observed in May, June, and July 2017 (Figure 2) and the higher nutrient concentrations measured in the FRES during the same period (Pereira et al., 2013). Under these conditions, continental runoff increases significantly and ecological impacts can be seen, such as the reduction in copepods diversity and, consequently, the occurrence of zooplanktivorous fish. This may lead to an increase in local trophic status, affecting local water quality (Sahu et al., 2013; Andrade et al., 2016; Desmit et al., 2018).

In addition, non-naturals processes, such as the release of untreated efuents and nonpoint source pollution (excess fertilizers) in estuaries, also lead to water nutrient enrichment at a higher scale (Marreto et al., 2017; Dewi et al., 2018). The TRIX is a multivariate index commonly used worldwide to assess trophic status and water quality (Seisdedo et al., 2014; Vargas-Gonzáles et al., 2014; Sá et al., 2021; Silva et al., 2021). It showed that the FRES is under anthropogenic pressure, especially during the rainy season and near the Formoso River, where hypereutrophic conditions were recorded even disregarding dissolved organic fractions of phosphorus and nitrogen, which could further increase TRIX values by ± 0.4 points (Vollenweider et al., 1998).

Dissolved inorganic nutrients presented a typical distribution for tropical estuaries, with values decreasing according to seawater-freshwater mixing (Jales et al., 2012; Cordeiro et al., 2014; Anguiano-Cuevas et al., 2015). Silicious (Si) is one of the main compounds found in the continental crust, which is why the SRSi is the most abundant dissolved nutrient in estuaries. Its correlation with Chl-a indicates the predominance of diatoms that use silica (Si(OH)₄) to build cells walls, as noted in prior studies conducted in the FRES (Silva et al., 2009; Grego, 2010; Aquino et al., 2012; Lima, 2016).

Regarding DIN and SRP, concentrations were higher in the upper and middle portions of the FRES due to organic matter remineralization, which is more intense in regions surrounded by mangrove forests and sediments rich in organic carbon, mainly during rainy seasons (Chen et al., 2018; Taillardat et al., 2020). Moreover, the high TRIX values near the Formoso River were similar to those reported in extremely polluted estuaries (Flores-Montes et al., 2011; Batista and Flores-Montes et al., 2013; Guenther et al., 2014; Fang and Wang, 2020). This may reffect the proximity to several agriculture and aquaculture facilities, the urban center of Rio Formoso city, and the influence of a Sewage Treatment Station (STS).

Over 80% of the entire Rio Formoso city territory is occupied by farming, mainly sugarcane, fish, and shrimp, which are the most proftable locally (IBGE, 2010). The use and inadequate release of fertilizers are the main sources of anthropogenic nitrogen in estuaries, with a global input of 118 × 10⁹ kg N yr^-1 (Lu and Tian, 2017; Malone and Newton, 2020). In addition to the resuspended sediments, excess residual organic matter from farming and the use of pesticides significantly decrease water quality in the efuent-receiving ecosystem (Barraza-Guardado et al. 2014; Cabral and Fonseca, 2019). Adding to that is the fact that only 32% of the city’s sewage is properly treated (IBGE, 2010).

Urban growth and low sewage treatment rates are the second main sources of nitrogen and phosphorus input into the estuarine system (Beusen et al., 2016), increasing the local eutrophication status (Flores-Montes et al., 2011; Cordeiro et al., 2014; Monteiro et al., 2016; Sá et al., 2021). The STS next to Rio Formoso stores efuents in containment lagoons which overflow during extreme rainy seasons, such as during 2017 (Figure 3), carrying the sewage into the upper estuary (Melo, 2018). This has a direct effect on local organisms (Guenther et al., 2014; Araujo et al., 2016; Barroso et al., 2018) and can be associated with a reduced ichthyofaunal diversity, which is frequently reported by the local community (Barros et al., 2017; Lemasson et al., 2017).

The EPAG was created in 1997 with the primary aim of protecting and conserving natural systems essential to biodiversity, especially water resources. It classified the FRES as an integrated protected zone, where the release of untreated efuents is strictly prohibited. However, at the beginning of the 21st century, the STS in Rio Formoso city was not entirely effective, and domestic and industrial waste flowed directly into the estuarine system (Figure 5) (Paiva, 2012).

The high eutrophication status in the 2000s produced dead zones that resulted in a significant increase in the mortality of fishes and crustaceans and a strong media backlash (Paiva, 2012). As a result, in 2005, the STS started to use biological filters to reduce organic matter and nutrient excess, generating positive outcomes (Figure 5) such as reducing phytoplankton biomass by more than 90%, which then improved fishing activities (Paiva, 2012).

According to previous studies (Silva et al., 2009; Grego, 2010; Lima, 2016) and local residents (Melo, 2018), from 2014 to the present day the main causes behind decreases in water quality and declines in FRES fishing resources are the STS’s inadequate disposal of sewage and intensive farming. Nevertheless, compared to other tropical estuaries, the FRES is generally still in good condition, particularly during the dry season (Batista and Flores-Montes et al., 2013; Nascimento-Filho et al., 2013; Guenther et al., 2014).

CONCLUSIONS

We show that the FRES is a highly dynamic environment with two trophic status conditions, influenced by seasonal variations. During the dry season, the main channel of the estuary is mostly oligotrophic to mesotrophic. However, during the rainy season, almost all of the estuary is considered eutrophic with poor water quality, especially in the Formoso River, negatively impacting local subsistence activities.

Rainfall is a determinant factor for water quality and anthropogenic pressures, because agricultural and urbanization activities release untreated efuents into the Formoso River year round, albeit more intensely under high precipitation levels. By using a multivariate trophic index (TRIX), we observed that the local traditional community has faced worse scenarios over the past 20 years and might be forced to turn into complementary activities for additional income due to increasing pollution rates.

Integrated management of the EPAG, with the control and inspection of efuent release and treatments by farms and the STS, and a continuous water monitoring are important tools to improve water quality in the FRES. In addition, scientific research must be increasingly aligned with the local community’s needs with a view towards creating public policies that could improve the system’s conservation and protection.

ACKOWLEDGMENTS

We express our immense gratitude to this study’s funding agency, the Dean of Extension and Culture from the Federal University of Pernambuco - PROExC-UFPE (grants #260275.1413.249865.03032017 and #296013.1657.249865.02032028), which over the years has consistently fomented initiatives between universities and traditional communities. We also thank the fishers from Rio Formoso city, especially Mr. Neco, Mr. Chico, and Ms. Cícera, who welcomed us and brought us into their daily lives, bringing valuable learning and strengthening this knowledge partnership towards improving the Formoso River Estuarine System.

REFERENCES

• ALVES, G., FLORES-MONTES, M., GASPAR, F., GOMES, J. & FEITOSA, F. 2013. Eutrophication and water quality in a tropical Brazilian estuary. Journal of Coastal Research, 65(spe1), 7-12, DOI: https://doi.org/10.2112/SI65-002.1
  » https://doi.org/10.2112/SI65-002.1
• ANDRADE, M. P., MAGALHÃES, A., PEREIRA, L. C., FLORES-MONTES, M. J., PARDAL, E. C., ANDRADE, T. P. & COSTA, R. M. 2016. Effects of a La Niña event on hydrological patterns and copepod community structure in a shallow tropical estuary (Taperaçu, Northern Brazil). Journal of Marine Systems, 164, 128-143, DOI: https://doi.org/10.1016/j.jmarsys.2016.07.006
  » https://doi.org/10.1016/j.jmarsys.2016.07.006
• ANDREOLI, R. V. & KAYANO, M. T. 2007. A importância relativa do Atlântico Tropical Sul e Pacífico Leste na variabilidade de precipitação do Nordeste do Brasil. Revista Brasileira de Meteorologia, 22(1), 63-74, DOI: https://doi.org/10.1590/S0102-77862007000100007
  » https://doi.org/10.1590/S0102-77862007000100007
• ANGUIANO-CUEVAS, J. R., OLIVOS-ORTIZ, A., CERVANTES, O., AZUZ-ADEATH, I., RAMÍREZ-ÁLVAREZ, N. & RIVERA-RODRÍGUEZ, M. C. 2015. Evaluation of trophic state in the Palo Verde Estuary (Colima, México), action to regulating agricultural activities. Journal of Integrated Coastal Zone Management, 15(4), 507-522, DOI: https://doi.org/10.5894/rgci582
  » https://doi.org/10.5894/rgci582
• AQUINO, E. P., FIGUEIRÊDO, L. G. P., ANJOS, D. L., PASSAVANTE, J. Z. D. O. & SILVA-CUNHA, M. D. G. G. 2012. Biomassa ftoplanctônica e fatores ambientais em um estuário tropical do brasil. 2012. Tropical Oceanography Online, 40(1), 17-28, DOI: https://doi.org/10.5914/1679-3013.0061
  » https://doi.org/10.5914/1679-3013.0061
• ARAUJO, A. V., DIAS, C. O. & BONECKER, S. L. 2017. Differences in the structure of copepod assemblages in four tropical estuaries: importance of pollution and the estuary hydrodynamics. Marine Pollution Bulletin, 115(1-2), 412-420, DOI: https://doi.org/10.1016/j.marpolbul.2016.12.047
  » https://doi.org/10.1016/j.marpolbul.2016.12.047
• BARRAZA-GUARDADO, R. H., ENRÍQUEZ-OCANA, L. F., MARTÍNEZ-PORCHAS, M., MIRANDA-BAEZA, A. & PORCHAS-CORNEJO, M. A. 2014. Effect of shrimp farm efuent on water and sediment quality parameters of the coast of Sonora, Mexico. Ciencias Marinas, 40(4), 221-235, DOI: https://doi.org/10.7773/cm.v40i4.2424
  » https://doi.org/10.7773/cm.v40i4.2424
• BARROS, G. D., FONSECA, A. L. D. O., SANTOS, A. C. D., FONTES, M. L. S., VARELA, A. R. D. & FRANCO, D. 2017. Nutrient distribution in a shallow subtropical lagoon, south Brazil, subjected to seasonal hypoxic and anoxic events. Brazilian Journal of Oceanography, 65(2), 116-127, DOI: https://doi.org/10.1590/S1679-87592017101206502
  » https://doi.org/10.1590/S1679-87592017101206502
• BARROSO, M., SILVA, B. J., FLORES-MONTES, M. J. & SANTOS, P. J. P. 2018. Anthropogenic impacts on coral reef harpacticoid copepods. Diversity, 10(2), 32, DOI: https://doi.org/10.3390/d10020032
  » https://doi.org/10.3390/d10020032
• BATISTA, T. N. & FLORES-MONTES, M. J. 2013. Estado trófico dos estuários dos rios Ipojuca e Merepe – PE. Tropical Oceanography, 42(3), 22-30, DOI: https://doi.org/10.5914/tropocean.v42i3.5767
  » https://doi.org/10.5914/tropocean.v42i3.5767
• BEUSEN, A. H., BOUWMAN, A. F., VAN BEEK, L. P., MOGOLLÓN, J. M. & MIDDELBURG, J. J. 2016. Global riverine N and P transport to ocean increased during the 20th century despite increased retention along the aquatic continuum. Biogeosciences, 13(8), 2441-2451, DOI: https://doi.org/10.5194/bg-13-2441-2016
  » https://doi.org/10.5194/bg-13-2441-2016
• BORGES, A. V. 2010. Present day carbon dioxide fuxes in the coastal ocean and possible feedbacks under global change. In: DUARTE, P. & SANTANA-CASIANO, J. M. (eds.). Oceans and the Atmospheric Carbon Content. Berlim: Springer, pp. 47-77, DOI: https://doi.org/10.1007/978-90-481-9821-4_3
  » https://doi.org/10.1007/978-90-481-9821-4_3
• BOWER, C. E. & HOLM-HANSEN, T. 1980. A salicylate-hypochlorite method for determining ammonia in seawater. Canadian Journal of Fisheries and Aquatic Sciences, 37(5), 794-798, DOI: https://doi.org/10.1139/f80-106
  » https://doi.org/10.1139/f80-106
• CABRAL, A. & FONSECA, A. 2019. Coupled effects of anthropogenic nutrient sources and meteo-oceanographic events in the trophic state of a subtropical estuarine system. Estuarine, Coastal and Shelf Science, 225, 106228, DOI: https://doi.org/10.1016/j.ecss.2019.05.010
  » https://doi.org/10.1016/j.ecss.2019.05.010
• CHEN, C. Y., BUCKMAN, K. L., SHAW, A., CURTIS, A., TAYLOR, M., MONTESDEOCA, M. & DRISCOLL, C. 2021. The influence of nutrient loading on methylmercury availability in long island estuaries. Environmental Pollution, 268(Pt B), 115510, DOI: https://doi.org/10.1016/j.envpol.2020.115510
  » https://doi.org/10.1016/j.envpol.2020.115510
• CHEN, N., KROM, M. D., WU, Y., YU, D. & HONG, H. 2018. Storm induced estuarine turbidity maxima and controls on nutrient fuxes across river-estuary-coast continuum. Science of the Total Environment, 628, 1108-1120, DOI: https://doi.org/10.1016/j.scitotenv.2018.02.060
  » https://doi.org/10.1016/j.scitotenv.2018.02.060
• CLARK, F. C. M., BELL, M. D., BOYD, J. W., COMPTON, J. E., DAVIDSON, E. A., DAVIS, C., FENN, M. E., GEISER, L., JONES, L. & BLETT, T. F. 2017. Nitrogeninduced terrestrial eutrophication: cascading effects and impacts on ecosystem services. Ecosphere, 8(7), e01877, DOI: https://doi.org/10.1002/ecs2.1877
  » https://doi.org/10.1002/ecs2.1877
• CORDEIRO, I. A., FEITOSA, F. A. N., FLORES-MONTES, M. J. & SILVA, M. H. 2014. Distribuição sazonal e espacial da clorofla a e variáveis ambientais na Plataforma Continental de Pernambuco (Porto do Recife), Brasil. Tropical Oceanography, 42(1), 60-76, DOI: https://doi.org/10.5914/tropocean.v42i1.5803
  » https://doi.org/10.5914/tropocean.v42i1.5803
• CORDEIRO, I. A., FEITOSA, F. A. N., FLORES-MONTES, M. J., OTSUKA, A. Y. & SILVA, A. C. 2018. Environmental conditions of the Suape estuarine-port complex area (Pernambuco, Brazil): phytoplankton biomass and hydrological parameters. Journal of the Marine Biological Association of the United Kingdom, 99(2), 291-301, DOI: https://doi.org/10.1017/S0025315418000176
  » https://doi.org/10.1017/S0025315418000176
• COSTA, C. R., COSTA, M. F., DANTAS, D. V. & BARLETTA, M. 2018. Interannual and seasonal variations in estuarine water quality. Frontiers in Marine Science, 5, 301, DOI: https://doi.org/10.3389/fmars.2018.00301
  » https://doi.org/10.3389/fmars.2018.00301
• DANTAS, D. V., BARLETTA, M., LIMA, A. R. A., RAMOS, J. D. A. A., COSTA, M. F. & SAINT-PAUL, U. 2012. Nursery habitat shifts in an estuarine ecosystem: patterns of use by sympatric catfish species. Estuaries and Coasts, 35(2), 587-602, DOI: https://doi.org/10.1007/s12237-011-9452-0
  » https://doi.org/10.1007/s12237-011-9452-0
• DESMIT, X., THIEU, V., BILLEN, G., CAMPUZANO, F., DULIÈRE, V., GARNIER, J., LASSALETTA, L., MÉNESGUEN, A., NEVES, R., PINTO, L., SILVESTRE, M., SOBRINHO, J. L. & LACROIX, G. 2018. Reducing marine eutrophication may require a paradigmatic change. Science of the Total Environment, 635, 144-1446, DOI: https://doi.org/10.1016/j.scitotenv.2018.04.181
  » https://doi.org/10.1016/j.scitotenv.2018.04.181
• DEWI, N. N., SATYANTINI, W. H., SAHIDU, A. M., SARI, L. A. & MUKTI, A. T. 2018. Analysis of water quality on several waters affected by contamination in West Sumbawa Regency. IOP Conference Series: Earth and Environmental Science, 137, 012086, DOI: https://doi.org/10.1088/1755-1315/137/1/012086
  » https://doi.org/10.1088/1755-1315/137/1/012086
• DODDS, W. K., BOUSKA, W. W., EITZMANN, J. L., PILGER, T. J., PITTS, K. L., RILEY, A. J., SCHLOESSER, J. T. & THORNBRUGH, D. J. 2009. Eutrophication of US freshwaters: analysis of potential economic damages. Environmental Science & Technology, 43(1), 12-19, DOI: https://doi.org/10.1021/es801217q
  » https://doi.org/10.1021/es801217q
• FANG, T. H. & WANG, C. W. 2020. Dissolved and particulate phosphorus species partitioning and distribution in the Danshuei River Estuary, Northern Taiwan. Marine Pollution Bulletin, 151, 110839, DOI: https://doi.org/10.1016/j.marpolbul.2019.110839
  » https://doi.org/10.1016/j.marpolbul.2019.110839
• FILHO, F. J. P., MARINS, R. V., CHICHARO, L., SOUZA, R. B., SANTOS, G. V. & BRAZ, E. M. A. 2020. Evaluation of water quality and trophic state in the Parnaíba River Delta, northeast Brazil. Regional Studies in Marine Science, 34, 101025, DOI: https://doi.org/10.1016/j.rsma.2019.101025
  » https://doi.org/10.1016/j.rsma.2019.101025
• GARCÍA-ROBLEDO, E., CORZO, A. & PAPASPYROU, S. 2014. A fast and direct spectrophotometric method for the sequential determination of nitrate and nitrite at low concentrations in small volumes. Marine Chemistry, 162, 30-36, DOI: https://doi.org/10.1016/j.marchem.2014.03.002
  » https://doi.org/10.1016/j.marchem.2014.03.002
• GASPAR, F. L., PINHEIRO, B. R., NORIEGA, C. E. D., ARAUJO, M., LEFÈVRE, N. & FLORES-MONTES, M. J. 2018. Alkalinity, inorganic carbon and CO2 fux variability during extreme rainfall years (2010-2011) in two polluted tropical estuaries NE Brazil. Brazilian Journal of Oceanography, 66(1), 115-130, DOI: https://doi.org/10.1590/S1679-87592018149406601
  » https://doi.org/10.1590/S1679-87592018149406601
• GATTUSO, J. P., FRANKIGNOULLE, M. & WOLLAST, R. 1998. Carbon and carbonate metabolism in coastal aquatic ecosystems. Annual Review of Ecology and Systematics, 29(1), 405-434, DOI: https://doi.org/10.1146/annurev.ecolsys.29.1.405
  » https://doi.org/10.1146/annurev.ecolsys.29.1.405
• GRASSHOFF, K., KREMLING, K. & EHRHARDT, M. 1993. Methods of seawater analyses Weinheim: Wiley-VCH.
• GREGO, C. K. S. 2010. Estrutura e dinâmica do fitoplâncton no estuário do rio Ariquindá, Tamandaré, Pernambuco, Brasil [online]. DSc. Recife: UFPE (Universidade Federal de Pernambuco). Available at: https://repositorio.ufpe.br/handle/123456789/8313 [Accessed: 2019 July 27].
  » https://repositorio.ufpe.br/handle/123456789/8313
• GRIMM, A. M. 2004. How do La Niña events disturb the summer monsoon system in Brazil?. Climate Dynamics, 22(2), 123-138, DOI: https://doi.org/10.1007/s00382-003-0368-7
  » https://doi.org/10.1007/s00382-003-0368-7
• GRIMM, A. M. & TEDESCHI, R. G. 2009. ENSO and extreme rainfall events in South America. Journal of Climate, 22(7), 1589-1609, DOI: https://doi.org/10.1175/2008JCLI2429.1
  » https://doi.org/10.1175/2008JCLI2429.1
• GUENTHER, M., ARAÚJO, M., FLORES-MONTES, M., GONZALEZ-RODRIGUEZ, E. & NEUMANN-LEITÃO, S. 2014. Eutrophication effects on phytoplankton size-fractioned biomass and production at a tropical estuary. Marine Pollution Bulletin, 91(2), 537-547, DOI: https://doi.org/10.1016/j.marpolbul.2014.09.048
  » https://doi.org/10.1016/j.marpolbul.2014.09.048
• HÄDER, D. P., BANASZAK, A. T., VILLAFAÑE, V. E., NARVARTE, M. A., GONZÁLEZ, R. A. & HELBLING, E. W. 2020. Anthropogenic pollution of aquatic ecosystems: Emerging problems with global implications. Science of The Total Environment, 713, 136586, DOI: https://doi.org/10.1016/j.scitotenv.2020.136586
  » https://doi.org/10.1016/j.scitotenv.2020.136586
• IBGE (Instituto Brasileiro de Geografa e Estatística). 2010. Pesquisa cidades – Rio Formoso [online]. Rio de Janeiro: IBGE. Available at: https://cidades.ibge.gov.br/brasil/pe/rio-formoso [Accessed: 2020 May 8].
  » https://cidades.ibge.gov.br/brasil/pe/rio-formoso
• JALES, M. C., FEITOSA, F. A. N., KOENING, M. L., BASTOS, R. B. & MACHADO, R. C. A. 2012. O ecossistema recifal de Serrambi (Nordeste do Brasil): biomassa ftoplanctônica e parâmetros hidrológicos. Atlântica (Rio Grande), 34(2), 87-102.
• LEMASSON, A. J., FLETCHER, S., HALL-SPENCER, J. M. & KNIGHTS, A. M. 2017. Linking the biological impacts of ocean acidification on oysters to changes in ecosystem services: a review. Journal of Experimental Marine Biology and Ecology, 492, 49-62, DOI: https://doi.org/10.1016/j.jembe.2017.01.019
  » https://doi.org/10.1016/j.jembe.2017.01.019
• LIMA, A. N. 2016. Condições ambientais do estuário do rio Formoso (Tamandaré /Pernambuco/Brasil): biomassa ftoplanctônica e hidrologia [online]. MSc. Recife: UFPE (Universidade Federal de Pernambuco). Available at: https://repositorio.ufpe.br/handle/123456789/17883 [Accessed: 2019, July, 27].
  » https://repositorio.ufpe.br/handle/123456789/17883
• LIRA, L., ZAPATA, M. C. & FONSECA, V. G. 1979. Aspectos da dinâmica do estuário do Rio Formoso, PE. Cadernos Ômega da Universidade Federal de Pernambuco [online], 3(1-2), 133-156. Available at: https://hdl.handle.net/123456789/167 [Accessed: 2019, July, 27].
  » https://hdl.handle.net/123456789/167
• LU, C. & TIAN, H. 2017. Global nitrogen and phosphorus fertilizer use for agriculture production in the past half century: shifted hot spots and nutrient imbalance. Earth System Science Data, 9(1), 181-192, DOI: https://doi.org/10.5194/essd-9-181-2017
  » https://doi.org/10.5194/essd-9-181-2017
• MALONE, T. C. & NEWTON, A. 2020. The globalization of cultural eutrophication in the coastal ocean: causes and consequences. Frontiers in Marine Science, 7, 670, DOI: https://doi.org/10.3389/fmars.2020.00670
  » https://doi.org/10.3389/fmars.2020.00670
• MARRETO, R. N., BAUMGARTEN, M. D. G. Z. & WALL-NER-KERSANACH, M. 2017. Trophic quality of waters in the Patos Lagoon estuary: a comparison between its margins and the port channel located in Rio Grande, RS, Brazil. Acta Limnologica Brasiliensia, 29, e11, DOI: https://doi.org/10.1590/S2179-975X10716
  » https://doi.org/10.1590/S2179-975X10716
• MELO, P. W. 2018. Pesca artesanal: diversidade, ameaça e destino do pescado em Rio Formoso (PE) BSc. Recife: UFPE (Universidade Federal de Pernambuco).
• MONTEIRO, M. C., PEREIRA, L. C. C. & JIMÉNEZ, J. A. 2016. The trophic status of an Amazonian estuary under anthropogenic pressure (Brazil). Journal of Coastal Research, 75(spe1), 98-103, DOI: https://doi.org/10.2112/SI75-020.1
  » https://doi.org/10.2112/SI75-020.1
• MONTES, M. J. F, PAULO, J. G., NASCIMENTO-FILHO, G. A., GASPAR, F. L., FEITOSA, F. A. N., SANTOS-JÚNIOR, A. C., BATISTA, T. N. F., TRAVASSOS, R. K. & PITANGA, M. E. 2011. The trophic status of an urban estuarine complex in Northeast Brazil. Journal of Coastal Research, 64, 408-411.
• MORELLI, B., HAWKINS, T. R., NIBLICK, B., HENDERSON, A. D., GOLDEN, H. E., COMPTON, J. E., COOTER, E. J. & BARE, J. C. 2018. Critical review of eutrophication models for life cycle assessment. Environmental Science and Technology, 52(17), 9562-9578, DOI: https://doi.org/10.1021/acs.est.8b00967
  » https://doi.org/10.1021/acs.est.8b00967
• NASCIMENTO-FILHO, G. A., FLORES-MONTES, M. J., GASPAR, F. L., PAULO, J. G. & FEITOSA, F. A. N. 2013. Eutrophication and water quality in a tropical Brazilian estuary. Journal of Coastal Research, 65(spe1), 7-13, DOI: https://doi.org/10.2112/SI65-002.1
  » https://doi.org/10.2112/SI65-002.1
• PAIVA, M. V. C. 2012. Avaliação da comunidade ftoplanctônica e eficiência de um sistema de tratamento de esgotos no litoral de Pernambuco [online]. MSc. Recife: UFPE (Universidade Federal de Pernambuco). Available at: https://repositorio.ufpe.br/handle/123456789/10675 [Accessed: 2019, July, 27].
  » https://repositorio.ufpe.br/handle/123456789/10675
• PEREIRA, L. C. C., OLIVEIRA, S. M. O., COSTA, R. M., COSTA, K. G. & VILA-CONCEJO, A. 2013. What happens on an equatorial beach on the Amazon coast when La Niña occurs during the rainy season? Estuarine, Coastal and Shelf Science, 135, 116-127, DOI: https://doi.org/10.1016/j.ecss.2013.07.017
  » https://doi.org/10.1016/j.ecss.2013.07.017
• PINTO, M. F. 2016. Pesca artesanal no litoral pernambucano e cearense: implicações conservacionistas Dsc. Recife: UFPE (Universidade Federal Rural de Pernambuco).
• RODRIGUES, L., SOUZA, W. M., COSTA, V. S. O. & PEREIRA, M. L. T. 2017. Infuência dos eventos de El Niño e La Niña no regime de precipitação do Agreste de Pernambuco. Revista Brasileira de Geografa Física, 10(6), 1995-2009, DOI: https://doi.org/10.26848/rbgf.v10.6.p1995-2009
  » https://doi.org/10.26848/rbgf.v10.6.p1995-2009
• RUBIO-CISNEROS, N. T., HERRERA-SILVEIRA, J., MO-RALES-OJEDA, S., MORENO-BÁEZ, M., MONTERO, J. & PECH-CÁRDENAS, M. 2018. Water quality of inlets’ water bodies in a growing touristic barrier reef Island “Isla Holbox” at the Yucatan Peninsula. Regional Studies in Marine Science, 22, 112-124, DOI: https://doi.org/10.1016/j.rsma.2018.06.006
  » https://doi.org/10.1016/j.rsma.2018.06.006
• SÁ, A. K. D. D. S., CUTRIM, M. V. J., COSTA, D. S., CAVALCANTI, L. F., FERREIRA, F. S., OLIVEIRA, A. L. L. & SEREJO, J. H. F. 2021. Algal blooms and trophic state in a tropical estuary blocked by a dam (northeastern Brazil). Ocean and Coastal Research, 69, e21009, DOI: https://doi.org/10.1590/2675-2824069.20-006akddss
  » https://doi.org/10.1590/2675-2824069.20-006akddss
• SAHU, N., SINGH, R. B., KUMAR, P., SILVA, R. V. D. & BEHERA, S. K. 2013. La Niña impacts on Austral Summer extremely high-streamflow events of the Paranaíba River in Brazil. Advances in Meteorology, 2013, 461693, DOI: https://doi.org/10.1155/2013/461693
  » https://doi.org/10.1155/2013/461693
• SANTIAGO, M. F., SILVA-CUNHA, M. G. G., NEUMANN-LEITÃO, S., COSTA, K. M. P., PALMEIRA, G. C. B., NETO, F. F. P. & NUNES, F. 2010. Phytoplankton dynamics in a highly eutrophic estuary in tropical Brazil. Brazilian Journal of Oceanography, 58(3), 189-205.
• SANTOS, L. D. D. 2016. Dinâmica sedimentar e o comportamento sazonal da matéria orgânica no estuário do rio Formoso-PE [online]. MSc. Recife: UFPE (Universidade Federal de Pernambuco). Available at: https://repositorio.ufpe.br/handle/123456789/24254 [Accessed: 2019, July, 27].
  » https://repositorio.ufpe.br/handle/123456789/24254
• SATHICQ, M. B., BAUER, D. E. & GÓMEZ, N. 2015. Influence of El Niño Southern Oscillation phenomenon on coastal phytoplankton in a mixohaline ecosystem on the southeastern of South America: Río de la Plata estuar y. Marine Pollution Bulletin, 98(1-2), 26-33, DOI: https://doi.org/10.1016/j.marpolbul.2015.07.017
  » https://doi.org/10.1016/j.marpolbul.2015.07.017
• SCHOEN, M. E., XUE, X., WOOD, A., HAWKINS, T. R., GARLAND, J. & ASHBOLT, N. J. 2017. Cost, energy, global warming, eutrophication and local human health impacts of community water and sanitation service options. Water Research, 109, 186-195, DOI: https://doi.org/10.1016/j.watres.2016.11.044
  » https://doi.org/10.1016/j.watres.2016.11.044
• SEISDEDO, M., MOREIRA, A. R., COMAS, A. A. & ARENCIBIA, G. 2014. Analysis of tools for trophic status assessment of water in Cienfuegos bay, Cuba. Pan-American Journal of Aquatic Sciences, 9(2), 103-111.
• SILVA, B. J., IBÁNHEZ, J. S. P., PINHEIRO, B. R., LADLE, R. J., MALHADO, A. C., PINTO, T. K. & FLORES-MONTES, M. J. 2021. Seasonal influence of surface and underground continental runoff over a reef system in a tropical marine protected area. Journal of Marine Systems, 226, 103660, DOI: https://doi.org/10.1016/j.jmarsys.2021.103660
  » https://doi.org/10.1016/j.jmarsys.2021.103660
• SILVA, M. H., SILVA-CUNHA, M. G. G., PASSAVANTE, J. Z. O., GREGO, C. K. S. & MUNIZ, K. 2009. Estrutura sazonal e espacial do microftoplâncton no estuário tropical do rio Formoso, PE, Brasil. Acta Botanica Brasilica, 23(2), 355-368.
• STRICKLAND, J. D. & PARSONS, T. R. 1972. A practical handbook of seawater analysis. Bulletin of Fisheries Research, 167, 1-311.
• TAILLARDAT, P., MARCHAND, C., FRIESSA D. A., WIDORYB, D., DAVIDF, F., OHTEG, N., NAKAMURAH, T., VINHI, T. V., THANH-NHOJ, N. & ZIEGLER, A. D. 2020. Respective contribution of urban wastewater and mangroves on nutrient dynamics in a tropical estuary during the monsoon season. Marine Pollution Bulletin, 160, 111652, DOI: https://doi.org/10.1016/j.marpolbul.2020.111652
  » https://doi.org/10.1016/j.marpolbul.2020.111652
• UNESCO (United Nations Educational, Scientific and Cultural Organization). 1966. Determination of photosynthetic pigments in seawater. Monography on Oceanography Methodology, 69.
• UNESCO (United Nations Educational, Scientific and Cultural Organization). 1973. International Oceanographic Tables Volume 2. Oxygen Solubility in Sea Water Paris: UNESCO.
• VARGAS-GONZÁLEZ, H. H., ARREOLA-LIZÁRRAGA, J. A., MENDOZA-SALGADO, R. A., MÉNDEZ-RODRÍ-GUEZ, L. C., LECHUGA-DEVEZE, C. H., PADILLA-ARREDONDO, G. & CORDOBA-MATSON, M. 2014. Effects of sewage discharge on trophic state and water quality in a coastal ecosystem of the Gulf of California. The Scientific World Journal, 2014, 618054, DOI: https://doi.org/10.1155/2014/618054
  » https://doi.org/10.1155/2014/618054
• VASCONCELOS, R. P., REIS-SANTOS, P., COSTA, M. J. & CABRAL, H. N. 2011. Connectivity between estuaries and marine environment: Integrating metrics to assess estuarine nursery function. Ecological Indicators, 11(5), 1123-1133, DOI: https://doi.org/10.1016/j.ecolind.2010.12.012
  » https://doi.org/10.1016/j.ecolind.2010.12.012
• VOLLENWEIDER, R. A., GIOVANARDI, F., MON-TANARI, G. & RINALD, A. 1998. Characterization of the trophic conditions os marine coastal waters with special reference to the NW Adriatic Sea: proposal for a trophic scale, turbidity and generalized water quality index. Environmetrics, 9(3), 329-357, DOI: https://doi.org/10.1002/(SICI)1099-095X(199805/06)9:3<329::AID-ENV308>3.0.CO;2-9
  » https://doi.org/10.1002/(SICI)1099-095X(199805/06)9:3<329::AID-ENV308>3.0.CO;2-9
• WHITFIELD, A. K. 2017. The role of seagrass meadows, mangrove forests, salt marshes and reed beds as nursery areas and food sources for fishes in estuaries. Reviews in Fish Biology and Fisheries, 27(1), 75-110, DOI: https://doi.org/10.1007/s11160-016-9454-x
  » https://doi.org/10.1007/s11160-016-9454-x
• ZHANG, W., JIN, X., LIU, D., LANG, C. & SHAN, B. 2017. Temporal and spatial variation of nitrogen and phosphorus and eutrophication assessment for a typical arid river — Fuyang River in northern China. Journal of Environmental Sciences, 55, 41-48, DOI: https://doi.org/10.1016/j.jes.2016.07.004
  » https://doi.org/10.1016/j.jes.2016.07.004

Edited by

• Associate Editor: Carmen G. Castro

Publication Dates

• Publication in this collection
  19 Sept 2022
• Date of issue
  2022

History

• Received
  17 Jan 2021
• Accepted
  20 July 2022