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The present study provides evidence that large dams that trap riverine sediment, decrease significantly SPM within estuaries, making them less turbid and less of a particulate trap for phosphorus adsorption. The study gives science-based insights for a future integrated estuarine water management in the Yangtze (Changjiang) Estuary. The hindsight focuses on the evolution and fate of riverine dissolved inorganic phosphorus (DIP) in the Yangtze Estuary from 1999 to 2010. A significant correlation between phosphorus and suspended particulate matter (SPM) was established. This shows that, in the past decade, the estuary has changed from being a source of DIP to being a sink, and from a heterotrophic system to an autotrophic system. The ecosystem shift may be explained by the combined impact of the construction of dams that retain SPM but not nutrients, and to increasing nutrient fluxes to the estuary due to increasing usage of fertilizer and sewage. The foresight study is based on likely future scenarios for 2050. These are estimated using historical data and the stratified and a muddy-LOICZ model, which takes stratification and adsorption–desorption of phosphorus into account. We forecast that in 2050 the effective DIP inflow into the Yangtze Estuary will increase by a factor of 1.5 if the SPM remains at the current annual average of 700 mg L −1 , and by a factor of 3.3 if the SPM decreases to 200 mg L −1 as a result of the dams, which will further degrade the estuary. [ABSTRACT FROM AUTHOR]

Abstract: Dramatic loss of life and economic losses in coastal zones have focused attention on natural and man-made hazards. The paper starts with a review of the coastal vulnerability terminology. Coastal zones are then presented as complex, socio-ecological systems. Four main coastal hotspots of vulnerability; namely Arctic coasts, small islands, river-mouth systems and urban coasts (including megacities) are analysed to demonstrate the complexity of coastal vulnerability. A DPSIR framework is used to explore the causes and consequences of coastal vulnerability. The paper then focuses in particular on societal, as well as floods, storm-surges and tsunamis to technological and engineering solutions. These include raising awareness, advancing forecasting, enhancing preparedness and improving governance. [Copyright &y& Elsevier]

Abstract: The paper gives an overview of some of the large, shallow, semi-enclosed coastal systems (SECS) in Europe, These SECS are important both from the ecological and the economic perspective (socio-ecological systems) and provide many valuable ecosystem goods and services. Although some of the systems are transitional waters under the Water Framework Directive, this is not the case for all of the systems. The paper adopts a Driver-Pressure-State-Impact-Response approach to analyse the ecological status, vulnerability and future perspectives of these systems in the context of global change. [Copyright &y& Elsevier]

Abstract: Coastal shallow lagoons are important ecosystems in terms of their high ecological relevance. They act as buffers of the land–sea interface, providing valuable ecosystem services such as nutrient recycling, decomposition of organic matter and removal of pollutants. Lagoons are regions of restricted exchange, subject to anthropogenic pressures that result in problems such as eutrophication. Because they are shallow, submerged primary producers play a prominent role in lagoon system metabolism. Furthermore, coastal lagoons are particularly vulnerable to global climate change and may act as ‘sentinel systems’. Sea level rise already threatens to overwhelm some lagoons, such as Venice and Moroccan lagoons. Recent observations and studies have shown that a global climate change, especially the warming of the climate system and the sea level rise is unequivocal (IPCC, 2007). Therefore, the dCSTT-MPB model, which deals with nitrogen and chlorophyll concentrations in the water column and within the sediments, was used to explore a range of scenarios that aimed at representing these changes. The tendency of the light limitation due to the sea level rise is the potential degradation of the microphytobenthos community. This reduction would lead to stronger nitrogen fluxes from pore water to the water column, increasing significantly the nitrogen concentrations. No increase in the phytoplankton community was found because it is mainly influenced by the resuspension of microphytobenthos. High nitrogen concentration may be the first indication of an eutrophication event. Nonetheless, nitrogen may be exported to the sea and cause problems in the adjacent coastal waters. The increase in temperature did not lead to significant differences. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to elaborate on the role of coastal megacities in environmental degradation and their contribution to global climate change. Although only less than 4 percent of the total world’s population resides in coastal megacities, their impact on environment is significant due to their rapid development, high population densities and high consumption rate of their residents. This study was carried out by implementing a Drivers-Pressures-States-Impacts-Responses (DPSIR) framework. This analytical framework was chosen because of its potential to link the existing data, gathered from various previous studies, in causal relationship. In this text, coastal megacities have been defined as cities exceeding 10 million inhabitants, situated in "near-coastal zone". Their high rates of the consumption of food, water, space and energy were observed and linked to the high performance rates of related economic activities (industry, transportation, power generation, agriculture and water extraction). In many of the studied coastal megacities, deteriorated quality of air and water was perceived, which can, in combination with global warming, lead to health problems and economic and social disturbance among residents. The extent of problems varied between developing and developed countries, showing higher rates of population growth and certain harmful emissions in megacities of developing countries, as well as more problems regarding food and water shortages, sanitation, and health care support. Although certain projections predict slowdown of growth in most coastal megacities, their future impact on environment is still unclear due to the uncertainties regarding future climate change and trajectories of consumption patterns. [Copyright &y& Elsevier]

Abstract: Human intervention has resulted in a number of global and river syndromes that are mirrored by coastal syndromes caused by erosion, subsidence, salinization of aquifers, urbanization, eutrophication, invasive species and over exploitation of natural resources. These problems are now global, with few coastal zones remaining unaffected and pristine. However, the problems are particularly severe at “hotspots” in the coastal zone. These include river-mouth systems where fluxes of water, sediment, fertilizers and contaminants are focused; urbanized coasts and megacities where vulnerable populations are concentrated; Arctic coasts where the effects of climate change are accelerating a fundamental state change; and, at low lying coasts that are at risk of flooding, storm surges, sea-level rise and subsidence such as Micronesian island states where managed realignment and setback is not an option. A range of societal responses and appropriate governance frameworks will be necessary to treat the coastal syndromes. [Copyright &y& Elsevier]

Abstract: Microphytobenthos (MPB) are an important, yet highly variable, component of productive shallow systems and intertidal areas. Samples were collected from Ria Formosa, Portugal, to assess the temporal and spatial variability of microphytobenthic chlorophyll in two types of intertidal sediment: mud and sand. Chlorophyll pigments were measured spectrophotometrically after freeze-drying and extraction into an acetone–water mixture. Time-series of superficial chlorophyll measured at two sites during 2006–2007 showed no obvious seasonal peaks. A truncated Fourier series was fitted to the time-series data. Seasonality was very weak: only 5% of the estimated total variance could be explained by annual cycle components up to 3year−1, while 25% was explained by waves with periods from 14 to 91days. The residual error of the Fourier series was partitioned into within-day variance (61%) and other components (9%). The within-day variation was made up of roughly equal contributions from: (i) variability associated with sampling within-sites; and (ii) differences between-sites. There were no significant correlations between MPB chlorophyll and tidal range, wind speed, solar irradiance, water temperature and salinity and water nutrient concentrations. Sediment type was once more confirmed to be a key factor to MPB spatial variability. These results are discussed in relation to processes controlling the distribution of benthic microalgae in Ria Formosa, and their implications considered in relation to on-going work to understand and model the role of microphytobenthos in eutrophication in such water bodies. [Copyright &y& Elsevier]

Abstract: The dynamics between nutrients, the microplankton assemblage and physical factors were evaluated in the Ria Formosa (S. Portugal) coastal lagoon. Water samples were collected from Ramalhete and Ponte within the lagoon and compared with the conditions at Barra, an oceanic inlet. The two lagoon stations represent the boundary conditions of two different water bodies that have been registered as intercalibration sites for the European Water Framework Directive. Sampling coincided with high and low water conditions, at the summer and winter solstice, and at the spring and autumn equinox between June 2001 and July 2002. Chlorophyll a values, with a maximum of 5.1μgl−1 during growing season, were lower than those reported for similar systems. The maximal winter values of 5.99μM for total inorganic nitrogen, 0.53μM for phosphate, and 6.34μM for silicate, were also lower than previously reported for this area. Microplankton peaked during the summer solstices of June 2001 and July 2002, with maximal abundances of 12×105 cellsl−1 and 7×105 cellsl−1 for total microplankton, respectively: these communities were dominated by diatoms. At the autumn and spring equinox (September 2001 and April 2002), the maximal abundances were 4.9×105 cellsl−1 and 2.6×105 cellsl−1 total microplankton, respectively: these communities were more evenly distributed between diatoms, dinoflagellates, nanoflagellates and ciliates. At the winter solstice (December 2001), the microplankton were at their lowest with a maximal abundance of 1.0×105 cellsl−1: these communities were dominated by small organisms, particularly nanoflagellates. The oceanic microplankton community at the Barra inlet was generally less numerous and differed in composition from the lagoonal communities at Ramalhete and Ponte. Multivariate analysis clustered the microplankton assemblage according to season. Changes in the microplankton community were related mainly to variations in temperature, solar radiation and salinity, and to the availability of the reduced forms of nitrogen. The differences between the parameters observed at the entrance of the lagoon during the summer solstice of 2001 and 2002 may be due, respectively, to the colder upwelled water during 2001 and the much warmer water observed in 2002. Nutrient enrichment was possible both from coastal waters and from internal lagoonal processes. Consequent accumulation of biomass may occur in inner regions where water circulation is restricted, which may lead to episodes of water quality degradation. This study does not alter the boundary conditions for Ramalhete and Ponte registered at the European Commission, respectively, as ‘good/moderate’ and ‘high/good’. [Copyright &y& Elsevier]

Abstract: Historical data from the Ria Formosa lagoon are classified according to the EEA 2001 guidelines to provide a frame of reference to evaluate the effect of management during the implementation of the environmental legislative Directives. Water samples from the Ria Formosa lagoon were significantly enriched in nitrogen (NH4+ NO2- and NO3-) with respect to the adjacent coastal waters indicating that inputs from sewage, agricultural runoff and benthic fluxes were not fully assimilated within the lagoon. Tidal flushing was insufficient in the inner areas of the lagoon to remove or effectively dilute these inputs. Enrichment was most severe close to the urban centres of Faro and Olhão, as well as in the Gilão Estuary and the shallow extremities. Dissolved oxygen undersaturation (mean 75% during daylight hours) was associated with the area close to the sewage outlets of Faro. In the shallow west end of the lagoon during summer, dissolved oxygen supersaturation reached 140% during the day but fell to 50% at night. Classification using the EEA (2001) guidelines suggests the system is “poor” or “bad” with respect to phosphate concentrations for the majority of the year and “poor” in nitrogen contamination during the autumn rainy period. Due to the high overall nitrogen load in the lagoon, there is a net export to the coastal waters, especially during November and December, and phosphate only becomes limiting briefly during the spring bloom (April). Therefore, substantial phytoplankton populations may be supported year-round in the lagoon. The consequences of water quality deterioration in the Ria Formosa would negatively affect the lagoon as a regional resource, important for its ecological, economic and recreational value. The industries most affected would be tourism, fisheries and aquaculture. Management options include Urban Waste Water Treatment, dredging, artificial inlets, limits on urban development and changes in agricultural practices. [Copyright &y& Elsevier]

In a recent study of the mesotidal Ria Formosa, a coastal lagoon in southern Portugal, water temperature in the channels ranged from 12 °C in winter to 27 °C in summer and salinity from 13 to 36.5, although much higher values were observed in saltpans. Conditions in the Ria Formosa were not homogeneous despite a large tidal exchange of water; the inner channels of the Ria Formosa were brackish in winter but hypersaline in summer. Water in inner areas of lagoon had significantly different temperature and salinity characteristics compared to the inflowing coastal water, both in winter and in summer. Areas with these differences in temperature and salinity were detectable both at low water and at high water neaps. Deterioration of water quality is therefore more probable in these areas. The waters went through a complex heating and cooling cycle in summer with diurnal difference of ∼6 °C and 2 in temperature and salinity, respectively. The lack of freshwater input and high insolation meant the outflowing water of the lagoon was more saline that the inflowing coastal waters. In summer, the temperature controlled density with the least dense waters also being the most saline, whereas in winter salinity was the major density controlling parameter. The effects of these freshwater inputs were localised to the vicinity of the Gila˜o River. No evidence was found of persistent or widespread temperature or salinity stratification in the Ria Formosa and so this shallow lagoon appears to be vertically well mixed. Vertical mixing does not allow a dense, stagnant, bottom layer of water to form that would aggravate a deterioration of water quality. The net effect of these processes is a parcel of water that moves through the lagoon with minimal dilution and potentially receiving waste discharges. [Copyright &y& Elsevier]

Natural and anthropogenic pressures drive coastal eutrophication worldwide, depending on the system's physical and biogeochemical dynamics in multiple spatial and temporal scales. Understanding the complexity of this process is essential to support management efforts and sustainability. Nutrients load to the Bay of Santa Catarina Island (BSCI), an important area for mollusc aquaculture, fisheries and tourism in Brazil, were assessed to identify the pressures of the eutrophication process. An updated Driver-Pressure-State-Impact-Response framework was used to facilitate the understanding of the relationship between human activities and impacts on human welfare. Pressures from runoff and effluents from combined sources resulted in inputs of 1998 t N.year−1 and 155 t P.year−1 to the system. The watersheds were characterized as meso-active to eury-active for both N and P yields. In addition to the local anthropogenic pressures, meso-scale events, such as the seasonal influence of the Plata Plume River, act as an external source of nutrients, sometimes associated with harmful algae bloom events. The results show that eutrophication and its symptoms could impact 85% of the ecosystem services of the region. Management of eutrophication at BSCI requires integrated actions between the nine municipalities of the watershed, but there are obstacles in environmental legislation and political interest to promote it. This study provides the scientific basis for stakeholders and decision-makers to establish priorities and actions in coastal municipalities to minimize eutrophication. Image 1 • Exogenous (Plata river plume) and endogenous pressures fuel the eutrophication. • Eutrophication symptoms potentially affect 85% of the ecosystem services. • Sustainability of marine resources (SDG 14.1) in BSCI is unlikely to be achieved by 2030. • Mitigation of endogenous pressure requires multi-level approach. [ABSTRACT FROM AUTHOR]

Abstract: Shallow coastal lagoons, especially the ones with clear waters and lighted substrata, are likely to have large microphytobenthos (MPB) communities. MPB is an important component of these systems, representing up to 99% of the chlorophyll concentration when compared to phytoplankton. It is therefore expected that MPB resuspension play a key role in the dynamics of phytoplankton due to the tide and wind action. Water samples were collected twice per month inside and outside Ria Formosa lagoon (Portugal), for nutrients and chlorophyll a (chl a). Sediment samples were also collected for MPB chl a. Chl a was also analysed in water and sediment samples from Venice lagoon (Italy), at least once per month. A truncated Fourier series was fitted to the data to investigate the seasonal and high-frequency components of the time-series. In the Ria Formosa, the best significant fit for MPB was obtained considering the sum of 26 wave-pairs (sin and cosine), which explained 31% of the variability. The seasonal cycle (1–3 waves) explained approximately 5% of the total variability. Within-day variability which includes spatial heterogeneity explained 61% of the variability. The best fit for phytoplankton inside Ria Formosa was obtained considering the sum of 23 wave-pairs. Outside the lagoon the best fit was obtained using only the sum of 16 wave-pairs. For both cases, the sum of waves explained more than 64% of the variability and the seasonal cycle explained more than 31% of the variability. It is expected that primary producers in the water column have a strong seasonal factor due to the direct effect of the solar cycle, which is the case of other clear waters. In the Venice lagoon, which is microtidal, the best fit for MPB was obtained using 10 wave-pairs. However, the best fit for phytoplankton was obtained with only 3 wave-pairs, indicating the importance of the seasonal cycle. Significant relationships were found between phytoplankton inside and outside the Ria Formosa, as well as between microphytobenthos and phytoplankton in the lagoons of Venice and Ria Formosa. These results suggest the influence of MPB resuspension in the phytoplankton community of shallow coastal lagoons and the importance of phytoplankton exportation to the coastal zone. [Copyright &y& Elsevier]

Abstract: Generally the waters of the Ria Formosa Lagoon, Portugal have a short residence time, in the order of 0.5 days (Tett, P., Gilpin, L., Svendsen, H., Erlandsson, C.P., Larsson, U., Kratzer, S., Fouilland, E., Janzen, C., Lee, J., Grenz, C., Newton, A., Ferreira, J.G., Fernandes, T., Scory, S., 2003. Eutrophication and some European waters of restricted exchange. Continental Shelf Research 23, 1635–1671). This estimation is based on the measurements of currents and the modelling of water exchange at the outlets to the ocean. However, observations of the temperature and salinity in the inner channels imply that residence time is greater in these regions of the lagoon. To resolve this apparent contradiction, spatial measurements of the temperature and salinity were made with a meter for conductivity, temperature and depth along the principal channels of the western portion of the lagoon, with a sampling frequency of two per second. Evaporation rates of 5.4mmday−1 were measured in a salt extraction pond adjacent to the lagoon and used to determine the residence time through salinity differences with the incoming seawater. In June 2004, the water flooding in from the ocean had an average salinity of 36.07 which contrasted with a maximum of 37.82 at mid ebb on a spring tide, corresponding to a residence time of >7 days; the mean residence time was 2.4 days. As the tide flooded into the channels, the existing water was advected back into the lagoon. Although there was a small amount of mixing with water from another inlet, the water body from the inner lagoon essentially remained distinct with respect to temperature and salinity characteristics. The residence time of the water was further prolonged at the junction between the main channels, where distinct boundaries were observed between the different water masses. As the water ebbed out, the shallow Western Channel was essentially isolated from the rest of the outer lagoon, and the water from this channel was forced down the Ramalhete Channel, from where it was unable to exit the lagoon in one tidal cycle due to the extensive path length of ∼14km to the sea. Although the overall exchange rate of water is short in the outer lagoon, this study emphasizes that management models should take into account additional complexities that might arise from the much longer exchange rates of the inner lagoon. For example, the principal sewage discharge for the urban area of Faro is into the section of the Ramalhete Channel where efficient flushing is impeded by the relatively high residence times of the water body in this channel. The implementation of the techniques used for this study are a quick and relatively cost effective approach to testing assumptions about water quality and exchange in shallow coastal systems. [Copyright &y& Elsevier]

Abstract: The yield of chlorophyll from dissolved inorganic nitrogen (DIN) has been shown to be a potentially useful parameter for predicting eutrophication, particularly, in the northerly, coastal waters of the North East Atlantic (NEA). This study investigates whether this parameter might also be appropriate for the southerly, coastal waters of the NEA. Nitrogen enrichment experiments were carried out using microcosms to determine the microplanktonic yield of chlorophyll from DIN in waters from the Ria Formosa (April 2002) and from Sagres (September 2002) on the south coast of Portugal. Continuous culture techniques enabled experiments to be run for 7 days after enrichment so that changes in the cumulative yield over time could be calculated. Yields from the Sagres experiment were consistently higher than those from the Ria Formosa experiment, with respective maximum yields of 4.7 and 2.1 μg chl (μmol N)-1, and respective steady-state yields of 3.1 and 0.9 μg chl (μmol N)-1. In addition, regressions carried out on historical data sets from the two study sites showed poor correlation between chlorophyll and nitrate. Other differences between the microcosm experiments at the two sites, included: background concentrations of DIN, silicate and phosphate that were, respectively, 5.6 μM, 8.1 μM, and 0.3 μM higher in the Ria; chlorophyll concentrations at Sagres that were double those of the Ria; accumulation of particulate nitrogen that was both more rapid and more substantial at Sagres; a different community structure for the diatoms at the two sites; more numerous autotrophic dinoflagellates, flagellates and cyanobacteria, as well as more numerous protozoan grazers, at Sagres. These differences may explain why the yield of chlorophyll from DIN at Sagres is one of the highest reported in the literature. This yield parameter requires further study under a range of seasonal conditions and with a range of microplankton communities before it could be considered useful for predicting eutrophication throughout the coastal waters of the NEA. [Copyright &y& Elsevier]

Upwelling events off the Southwest coast of Portugal can trigger phytoplankton blooms that are important for the fisheries and aquaculture sectors in this region. However, climate change scenarios forecast fluctuations in the intensity and frequency of upwelling events, thereby potentially impacting these sectors. Shifts in the phytoplankton community were analysed from the end of 2008 until the beginning of 2012 by examining the bio-optical properties of the water column, namely the absorption coefficients for phytoplankton, non-algal particles and coloured dissolved organic matter (CDOM). The phytoplankton community was assessed by microscopy, with counts from an inverted microscope, and by chemotaxonomic methodologies, using pigment concentrations determined by High-Performance Liquid Chromatography (HPLC). Results both from microscopy and from chemotaxonomic methods showed a shift from diatom dominance related to bloom conditions matching upwelling events, to small flagellate dominance related to no-bloom conditions matching relaxation of upwelling. During bloom conditions, light absorption from phytoplankton increased markedly, while non-algal particles and CDOM absorption remained relatively constant. The dynamics of CDOM in the study area was attributed to coastal influences rather than from phytoplankton origin. Changes in phytoplankton biomass and consequent alterations in phytoplankton absorption coefficients were attributed to upwelling regimes in the area. Bio-optical parameters can contribute to environmental monitoring of coastal and oceanic waters, which in the case of the European Union, involves the implementation of the Water Framework, Marine Strategy Framework and Marine Spatial Planning Directives. [ABSTRACT FROM AUTHOR]

Abstract: In the present study the annual variability of the physico-chemical parameters of four coastal lagoons subjected to intense human activity was characterised. The trophic state indices (TSI) of Carlson (1977) and the water quality index TRIX of Vollenweider et al. (1998) were tested and compared with the water quality categories proposed by the European Environmental Agency (2009). All the parameters were sampled monthly from May 2004 to July 2005. There were important differences in the annual variability of the physico-chemical parameters between the lagoons, reflecting the importance of human-induced pressures and the heterogeneity of these environments. The lagoons were in a eutrophic/hypereutrophic state most of the year. Trophic state indices classified the lagoons in a bad or poor trophic state most of the year, and they were not able to discriminate the effect of secondary variables such as freshwater releases, ground waters fluxes or water renewal. Nitrogen was the limiting factor in the lagoon with a higher exchange rate with the sea, while phosphorous was the limiting factor in the other lagoons, due to the high nitrogen external loads and the poor water renewal. The need for developing indices specifically designed for coastal lagoons in order to asses their trophic state is discussed. [Copyright &y& Elsevier]

Abstract: Shallow coastal lagoons in southern Portugal, such as the Ria Formosa and Alvor, are considered to be highly important both ecologically and economically. Given the impact of phytoplankton in the ecosystem productivity, it is important to understand its dynamics and to consider them for the assessment of ecosystem health. All available phytoplankton data (chlorophyll a; selected species composition and abundance) within the period from 1967 to 2011 were compiled within the framework of a project to implement the Water Framework Directive. Chlorophyll a (chl a) measurements in Ria Formosa from 1967 to 1968, 1985 to 1986, 1991 to 1992, 2006 to 2008, and 2010 show similar monthly averages with some exceptions. In the 80''s the monthly averages were less than half of what was observed in the 60''s. In the 90''s, the chl a concentrations increased significantly and in the period from 2006 to 2010, chl a concentrations ranged between the values found in the 80''s. The decrease in chl a concentrations during the 80''s is likely to be associated with a peak in shellfish production. Shellfish production was recorded to have decreased from 1990 onwards. Chl concentrations in Ria de Alvor are found to vary within the same range as in Ria Formosa. However, data are limited and does not allow a detailed historical comparison. During the most important chl a peaks, the phytoplankton community was characterized by coastal species, such as Pseudo-nitzschia sp., which may be associated with upwelling events. This was found in Ria Formosa both in the 90''s and from 2000 onwards, as well as in the most recent data from Ria de Alvor. This clearly indicates the influence of the coastal dynamics in these lagoons. High chl outside the lagoon confirmed the influence of coastal waters. In addition, high chl concentrations were also observed at inner parts of the lagoon but not outside, suggesting the existence of an interior maximum. The community was mainly characterized by the existence of low salinity tolerant species, such as Kryptoperidinium foliaceum. Over the time intervals in this study, the 90th percentile values of chlorophyll a concentrations were 3.0 in Ria Formosa and 2.6 mg m−3 in the Ria de Alvor. In a five-fold classification of ecological quality from High to Bad, we propose chlorophyll a concentrations of 5.3 mg m−3 as a reference value, 8 mg m−3 for the boundary High/Good, and 12 mg m−3 for the boundary Good/Moderate. According to this, all water bodies were considered as in High status. [Copyright &y& Elsevier]

Nutrient inputs and biogeochemical cycles in estuaries are strongly influenced by river discharge and suspended particulate matter (SPM). We evaluated temporal differences in nutrient bioavailability and net ecosystem productivity (NEP) and analyzed the effect of SPM on nutrient availability and estuary NEP in the mouth of the Magdalena River, Colombia. In this study, we used the stratified Muddy LOICZ model. Calculated water residence times in the estuary were low (~0.9–2.1 days), as were proportions of dissolved nitrogen (DIN) and phosphorus (DIP) forms (~10–30%) in the total nutrient pool. Dissolved nutrient proportions displayed differences between seasons (transition period [June 2018] and wet [November 2018]), and between the upper and lower, density-stratified water layers. Nutrient adsorption and desorption, associated with SPM in the estuary, determined bioavailable nutrient concentrations. When SPM was incorporated in the Muddy LOICZ model, the output indicated that NEP in the estuary was positive, i.e. gross primary productivity exceeded community respiration (autotrophic), and that there was net retention of nitrogen and phosphorus in the estuary. Primary producers in the autotrophic ecosystem fix sufficient carbon to supply higher trophic levels. Prevalence of fine sediment with high organic matter (OM) content in the Magdalena River, along with turbulence that results in vertical water column mixing, suggest conditions conducive to flocculation. This investigation highlights the importance of the Magdalena River mouth in the transport and processing of sediments and nutrients being discharged to the Caribbean Sea. • Dissolved nutrient distributions was studied in a tropical and turbid estuary. • River discharge determines the nutrient composition in Bocas de Ceniza Estuary. • Kd indicated low fractions (~10–30%) of dissolved nutrients. • When SPM was incorporated, the estuary shifted from heterotrophic to autotrophic. • We highlight the importance of the Magdalena River mouth in buffering nutrient. [ABSTRACT FROM AUTHOR]