Alfonso Corzo

• PhD
• Professor (Full) at Universidad de Cádiz

Epipelic, biofilm-forming diatoms are key drivers of the primary production of mudflats. Such primary production is strongly affected by the vertical migration of diatoms, which is modulated by diurnal photoperiods, tidal cycles, and photoprotection mechanisms. However, the role of vertical migration in the radiative energy budget (REB) of microphy...

The biogeochemical role of the sediments in the Guadalquivir River estuary, a vital region in the SW Iberian Peninsula, has been considerably neglected. The benthic microalgae (microphytobenthos, MPB) inhabiting the sediment surface could contribute to the autochthonous primary production and influence nutrient recycling in this hyper-turbid and hy...

Niche selection and microbial dispersal are key factors that shape microbial communities. However, their relative significance varies across different environments and spatiotemporal scales. While most studies focus on the impact of these forces on community composition, few consider other structural levels such as the physiological stage of the mi...

Estuarine systems are highly productive ecosystems with diverse fish communities that provide valuable ecosystem services. The structure and ecology of fish communities in the estuarine systems of the Mesoamerican Barrier Reef System region (MBRS) is largely unknown. Here, the fish communities and their relationship with environmental variables wer...

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 o...

Microphytobenthos (MPB) provides important ecosystem functions and services, contributing significantly to the total primary production in shallow coastal ecosystems. However, determining the factors that regulate the seasonal changes of MPB and its distribution patterns at larger scales is hindered by the considerable spatial and temporal variabil...

This study examines long-term burial rates of organic carbon (OC), organic nitrogen (ON), and total sulphur (TS) in a tidal-dominated coastal wetland with a high spatial heterogeneity and habitat diversity, and long history of human impacts, Cádiz Bay (SW Spain). Using replicate sediment cores, we quantified fluxes of these elements over a transect...

Temporarily open-closed estuaries and estuarine lagoons are among the most complex aquatic ecosystems, prone to undergo rapid changes in response to global change and other anthropogenic impacts. Nonetheless, studies on the factors that control annual cycles of phytoplanktonic biomass and primary production in such systems, especially tropical ones...

Microphytobenthos (MPB), the photosynthetic primary producing component of microbenthos, shows variable patterns in its biomass distribution along the intertidal gradient as a result of the interactions of factors such as light, tides, temperature, and grazing pressure. These patterns have been studied more extensively in northern European estuarie...

The interactions between phytoplankton, bacteria and resources, irradiance, and nutrients, leading to the formation of deep chlorophyll maxima (DCMs), are little understood in acid lakes. In “El Sancho” reservoir (Iberian Pyritic belt, Huelva, Spain), an acid mine drainage impacted waterbody (pH 3.5–4.0), a strong DCM forms in the metalimnion durin...

Wetlands and shallow aquatic environments are areas of high ecological value that offer important ecosystem services. Their low thermal inertia, due to their shallowness, makes them highly vulnerable to climatic variations. The ongoing anthropogenic production and liberation of greenhouse gases (GHG) such as CO2, CH4, or N2O results in climate chan...

La conservación de lagunas mareales y estuarios pasa por una delimitación espacial de las comunidades dominantes así como por una adecuada caracterización de su funcionamiento trófico. En el caso de las áreas intermareales, tradicionalmente se ha venido discriminando entre fondos de macrófitos marinos y fondos desnudos o colonizados por microfitobe...

Diel primary production patterns of intertidal microphytobenthos (MPB) have been attributed to short-term physiological changes in the photosynthetic apparatus or to diel changes in the photoautotrophic biomass in the sediment photic layer due to vertical migration. Diel changes in primary production and vertical migration are entrained by external...

Tropical estuaries are very little studied compared to temperate ones, despite their generally high primary production rate and hence potential contribution to global carbon and nitrogen budgets. The Gulf of Nicoya (northwest Costa Rica Pacific coast) is one of the most productive estuaries worldwide. However, how changes in benthopelagic coupling...

Irradiance and temperature variations during tidal cycles modulate microphytobenthic primary production potentially by changing the radiative energy balance of photosynthetic mats between immersion and emersion and thus sediment daily net metabolism. To test the effect of tidal stages on the radiative energy budget, we used microsensor measurements...

Three iron oxides-rich microsphere types (Type I to III) were detected in an Holocene 17 m-thick stratigraphic succession located in the Iberian Range (NE Spain). Lithofacies features indicate that the studied materials were generated in an alluvial-dominated setting, with a channeled area fringed by floodplain zones. During high water levels and h...

The interactions between phytoplankton, bacteria and nutrients leading to the formation of deep chlorophyll maximum (DCM) in acid lakes are little understood. Here, we studied the Sancho reservoir (Iberian Pyritic belt, Huelva, Spain), an acid mine drainage impacted water body (pH 3.5 - 4.0), where a strong DCM forms during the stratification perio...

Primary production of microphytobenthos (MPB) contributes significantly to the total production in shallow coastal environments. MPB is a diverse community in which diatoms are usually the main microalgal group. Diatoms require N, P and other nutrients as with other autotrophs, but in addition require silicate to create their outer cell wall. There...

Redox transitions induced by seasonal changes in water column O2 concentration can have important effects on solutes exchange across the sediment–water interface in systems polluted with acid mine drainage (AMD), thus influencing natural attenuation and bioremediation processes. The effect of such transitions was studied in a mesocosm experiment wi...

Microphytobenthos (MPB) plays a key role in the cycling of carbon and nitrogen in shallow estuaries and intertidal areas, contributing up to 50% of primary production. In the inner Cadiz Bay, the intertidal zone covers ~60% of its surface. Therefore, it is important to study the spatial and seasonal variability of microphytobenthic net primary prod...

Self-shading is widely known for primary producers, but it has been not addressed in detail for microphytoben-thos (MPB). Upper layers of MPB biomass limit light availability to the layers below, reducing the thickness of the photic layer within the sediment (zphot) and likely limiting MPB primary production and growth. To test this hypothesis, we...

Irradiance and temperature changes during tidal cycles affect microphytobenthic primary production potentially changing the radiative energy balance in the photosynthetic biofilm between immersion and emersion. To test this hypothesis, we estimated for the first time the radiative energy budget in a photosynthetic microbial mat during immersion and...

Greenhouse gas production in coastal sediments is closely associated with the early diagenesis processes of organic matter and nutrients. Discharges from anthropogenic activities, particularly agriculture, fish farming and waste-water treatment plants supply large amounts of organic matter and inorganic nutrients that affect mineralization processe...

Size structure of phytoplankton determines to a large degree the trophic interactions in oceanic and coastal waters and eventually the destiny of its biomass. Although, tropical estuarine systems are some of the most productive systems worldwide compared to temperate systems, little is known about phytoplankton biomass size fractions, their contrib...

Intertidal areas support extensive diatom-rich biofilms. Such microphytobenthic (MPB) diatoms exude large quantities of extracellular polymeric substances (EPS) comprising polysaccharides, glycoproteins and other biopolymers, which represent a substantial carbon pool. However, degradation rates of different EPS components, and how they shape hetero...

El método semi-implícito de Crank-Nicolson ha sido históricamente empleado para aproximar numéricamente ecuaciones de tipo parabólico (ley de Fourier del calor, segunda ley de Fick de la difusión), dada la estabilidad y convergencia de sus soluciones, su menor margen de error y el bajo coste computacional que requiere. Sus aplicaciones hoy en día s...

In this study, we reconstruct the recent environmental evolution of the inner Cadiz Bay using sedimentary records reaching back as far as AD 1700. We report lithological descriptions of the sediments and extensive mineralogical and geochemical analyses. An extraction technique that identifies different Fe phases provides an assessment of diagenetic...

The study of inorganic nutrients dynamics in shallow sediments usually focuses on two main pools: porewater (PW) nutrients and exchangeable (EX) ammonium and phosphate. Recently, it has been found that microphytobenthos (MPB) and other microorganisms can accumulate large amounts of nutrients intracellularly (IC), highlighting the biogeochemical imp...

Nitrate decreases sulfide release in wastewater treatment plants (WWTP), but little is known on how it affects the microzonation and kinetics of related microbial processes within the biofilm. The effect of nitrate addition on these properties for sulfate reduction, sulfide oxidation, and oxygen respiration were studied with the use of microelectro...

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The Telecommunications Marine Laboratory (TML) of the University of Cádiz takes part in a research project to study the intertidal sediments of the Bay of Cádiz. The collection of samples from the seabed and the transmission of data to the surface are performed by a Mini Profiler with four channels (MP4), which is supplied by UNISENSE. Each channel...

Tempisque River runoff affect abundance and taxonomic composition of microplankton. • Five microplankton assemblages associated with a seasonal and river–marine gradient. • 146 microplanktonic taxa were identified, 52 of which were new citations in the area. • Phytoplankton were mainly limited by light rather than nutrients. • From ecotone model at...

The “El Sancho” reservoir (Iberian Pyritic belt, Huelva, Spain) is an acid mine drainage impacted monomictic water body (pH 3.5-4.0). During the stratification period, a deep chlorophyll maximum (DCM) develops around 22 m depth, immediately below the thermocline and at an in situ irradiance < 8 µmol m-2 s-1. In 2013, the DCM showed maximum chloroph...

Extracellular polymeric substances (EPS) excreted by microphytobenthos, comprising primarily of diatoms, are important in stabilization of intertidal sediments and as a carbon source for heterotrophic organisms. However, the degradation rates of the different forms of EPS and how they shape the heterotrophic community in the sediment are not well u...

Reservoirs are one of the primary water supply sources. Knowledge of the metal fluxes at the water–sediment interfaces of reservoirs is essential for predicting their ecological quality. Redox oscillations in the water column are promoted by stratification; turnover events may significantly alter metal cycling, especially in reservoirs impacted by...

Nitrate addition stimulated sulfide oxidation by increasing the activity of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB), decreasing the concentration of dissolved H2S in the water phase and, consequently, its release to the atmosphere of a pilot-scale anaerobic bioreactor. The effect of four different concentrations of nitrate (0.12, 0.24,...

The temporal and vertical variability of live intertidal benthic foraminifera was studied in parallel to environmental variables such as porewater and overlying water nutrients, salinity, temperature, sedimentary pigments and organic carbon. About 80% of benthic foraminifera were concentrated in the upper 0-4 mm sediment layer, which was also the m...

Water reservoirs are a main source of water supply, and knowledge of the metal fluxes at the water-sediment interface is essential to predict their ecological quality. Moreover, redox oscillations promoted by turnover events may significantly alter metal cycling, especially if the reservoir is impacted by acid mine drainage (AMD). Under controlled...

Macroalgal accumulation and decomposition in shallow water environments typically result in an increase in the organic matter content of the sediment, affecting both benthic metabolism and nutrient dynamics. The present study investigates how a pulse addition of Ulva detritus to estuarine sediment influences the micro-distribution of O2, NO3- and N...

The Sancho Reservoir (SW Spain) is a monomictic water reservoir affected by acid mine drainage. It has a pH of ~4, with high sulfate (200 ppm) and heavy metal concentrations in the water column. The reservoir develops reducing conditions at the bottom during the stratification period. A laboratory experiment was carried out to study the effect of t...

Macroalgae blooms, a frequent consequence of eutrophication in coastal areas, affect the photosynthetic activity of sediments dominated by microphytobenthos (MPB). Light spectra, steady-state (after 1 h) microprofiles of O2 , gross photosynthesis (Pg ), community respiration in light (RL ) and net community photosynthesis (Pn ) were measured in dia...

The Sancho Reservoir (SW Spain) is a monomictic water reservoir affected by acid mine drainage. It has a pH of ~4, with high sulfate (200 ppm) and heavy metal concentrations in the water column. The reservoir develops reducing conditions at the bottom during the stratification period. A laboratory experiment was carried out to study the effect of t...

Complex microbial communities exhibit a large diversity, hampering differentiation by DNA fingerprinting. Herein, differential display-denaturing gradient gel electrophoresis is proposed. By adding a nucleotide to the 3′ ends of PCR primers, 16 primer pairs and fingerprints were generated per community. Complexity reduction in each partial fingerpr...

ABSTRACT: Freezing is a common treatment for the preservation of sediment samples. To test the role of microphytobenthos (MPB) abundance in the release of intracellular nutrients to the pore water due to cell breakage after freezing, referred to as freeze-lysable inorganic nutrients (FL-IN), parallel extractions were carried out from intertidal sed...

In this work, the influence of the biofilms in the corrosion process of different alloys of stainless steel was studied in two sampling points in a wastewater treatment plant during 4 years. The physicochemical microenvironment within the biofilms was characterized through O₂, H₂S and pH microelectrodes. Corrosion rates were q...

Biofilm formation is a critical process in the treatment of wastewaters. A highly diverse number of microorganisms constitute these biofilms. The ability of microorganisms to generate specific microenvironments in these biofilms allows their development under adequate conditions ensuring the efficient processing of wastes. In spite of the importanc...

In this paper, we analyze the pattern of distribution of three populations of picoplanktonic autotrophs measured using flow cytometry. Prochlorococcus sp., Synechococcus sp. and eukaryotic picoplankton were investigated at 58 stations to the south of the Iberian Peninsula including the northeastern Gulf of Cádiz, Strait of Gibraltar and northwester...

ABSTRACT: Eutrophication in coastal areas promotes blooms of green macroalgae that accumulate on the sediment, affecting the exchange of mass and energy at the sediment–water interface. The effects of macroalgal blooms on the microbenthic net metabolism and on the carbon and nitrogen contents of the sediment were studied during an in situ experimen...

Protoplasts were isolated from Ulva rigida C. Agardh (Chlorophyta) and two species of Rhodophyta, Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Folvik and Gracilaria tenuistipitata Chang et Xia var. liui with minor modifications (the inclusion of 0.01% agarase in the set of cell-wall-degrading enzymes for the two red algae). Flow cytometric...