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The marine N cycle is driven mainly by microorganisms whose distribution can be shaped by mesoscale eddies. Recently, eddies containing oxygen minimum zones (OMZs) have been recognised as N-loss hotspots, complicating even more the calculations of the marine N budgets. As a contribution to this understanding, we investigated the effect of a cyclonic eddy confined in an oxygen-depleted basin on the distribution of the N-cycling communities. We measured hydrographic properties of the water column, nutrient concentrations, and the abundance of key genes involved in the processes of nitrification (archaeal and bacterial amoA), denitrification (nirS and nirK), dissimilatory nitrate reduction to ammonia (DNRA; nrfA) and anammox (hzo) within the eddy. Our results indicated that the cyclonic circulation affected the distribution of nutrients and the abundance of amoA and nirS genes, whereas oxygen influenced the distribution of nirK, nrfA, and hzo genes. Additionally, the aerobic ammonium oxidation by archaea seems to be an important source of nitrite, which might fuel denitrifier, DNRA, and anammox communities in this basin. These findings along with the high N deficit in the OMZ suggest the existence of an active N cycling that might enhance the N-loss in this oxygen-depleted basin.

Coastal lagoons are highly sensitive ecosystems from the ecological point of view. Water samples to assess physicochemical parameters, as well as sediments to measure trace metals (Cd, Cr, Cu, Ni, ...

The Ring of Cenotes (RC) extends along the edge of the Chicxulub crater, in the limestone platform of the Yucatan Peninsula (YP), where groundwater shows two preferential flow paths toward the coast near Celestun and Dzilam Bravo towns. The objectives of this study were to describe the regional hydrogeochemical evolution of the groundwater in the RC, and its association with the dissolution/precipitation of the minerals present along its pathway to the ocean. These objectives results were obtained by: a) characterizing groundwater hydrogeochemistry, b) calculating calcite, dolomite, and gypsum saturation indexes in the study area, and c) developing a hydrogeochemical model using PHREEQC (U. S. Geological Survey) inverse modelling approach. The model predictions confirmed that there are two evolution pathways of the groundwater consistent with the preferential flow paths suggested in a previous regionalization of the RC. On the western path, where groundwater flows towards Celestun, marine intrusion influences the hydrogeochemical processes and represents a risk for the freshwater. On the eastern path, where groundwater flows toward Dzilam Bravo, rainfall has an important effect on the hydrogeochemical processes, evidenced by a higher concentration in sulfates during droughts than during rainy periods. Then, monitoring of marine intrusion and phases dissolution in the RC is highly recommended

Coralline algae are worldwide carbonate builders, considered to be foundational species and biodiversity hotspots. Coralline habitats face increasing pressure from human activities and effects related to Global Change, yet their ecological properties and adaptive responses remain poorly understood. The relationships of the algal microbiota with the mineral bioconstructions, as well as plasticity and resilience of coralline holobionts in a changing environment, are of particular interest. In the Gulf of California, Neogoniolithon trichotomum (Rhodophyta) is the main carbonate builder in tidal pools. We performed a multi-disciplinary assessment of the N. trichotomum microstructure using XRD, SEM microscopy and SR-FTIR spectromicroscopy. In the algal perithallus, magnesium-calcite and aragonite were spatially segregated and embedded in a polysaccharide matrix (rich in sulfated polysaccharides). Mg-calcites (18-19mol%Mg) were the main mineral components of the thallus overall, followed by iron carbonates related to dolomite (ankerite) and siderite. Minerals of late evaporitic sequences (sylvite and bischofite) were also present, suggesting potential halophilic microenvironments within the algal thalli. The diverse set of abundant halophilic, halotolerant and oligotrophic taxa, whose abundance increase in the summer, further suggests this condition. We created an integrated model, based on environmental parameters and the microbiota distribution, that identified temperature and nutrient availability (particularly nitrate and silicate) as the main parameters related to specific taxa patterns. Among these, Hahella, Granulossicoccus, Ferrimonas, Spongiibacteraceae and cyanobacterial Xenococcaceae and Nostocaceae change significantly between seasons. These bacterial components might play relevant roles in algal plasticity and adaptive responses to a changing environment. This study contributes to the understanding of the interplay of the prokaryotic microbiota with the mineral microenvironments of coralline algae. Because of their carbonates with potential resistance to dissolution in a higher pCO2 world and their seasonally dynamic bacteria, coralline algae are relevant targets to study coastal resilience and carbonated systems responses to changing environments.

Considerable variability in methane production and emissions has been reported in mangroves, explained by methane inhibition and oxidation. In this study, soil pore waters were collected from mangrove forests located in the Gulf of California (Mexico) exposed to shrimp farm disturbance. The δ13C of dissolved inorganic carbon (DIC) and CH4 were analyzed along with the δ13C of the soil organic matter to assess the proportion of CO2 derived from methanogenesis, its main pathway, and the fraction of methane oxidized. We performed slurry incubation experiments to fit the isotope–mass balance approach. Very low stoichiometric ratios of CH4/CO2 were measured in pore waters, but isotope mass balances revealed that 30–70% of the total CO2 measured was produced by methanogenesis. Mangrove soils receiving effluent discharges shifted the main methanogenesis pathway to CO2 reduction because of an increase in refractory organic matter. Isotope–mass balances of incubations indicated that methane was mainly oxidized by anaerobic oxidation of methane (AOM) coupled to sulfate reduction, and the increase in recalcitrant organic matter should fuel AOM as humus serves as a terminal electron acceptor. Since methanogenesis in mangrove soils is strongly controlled by the oxygen supply provided by mangrove roots, conservation of the forest plays a crucial role in mitigating greenhouse gas emissions., CONACyT: PROFAPI, Spanish Ministry of Science and Innovation (Grant: CGL2014-54502) and CSIC (Grant: I-COOP+2020–COOPA20433) funded this research.

The identification and quantification of global change, including climate change, requires long time series of key variables. In this work, the fundamentals and operation of low-cost long-term coastal observatories are described, and preliminary data are shown. The vision is to offer a scientific platform of physicochemical data for at least the next 100 years, what requires establishing sustainable strategies, training human resources, strong institutional support, and long-term funding sources. The network formally operates since 2013 and has generated more than 6 million data points, continuously growing, of which >1.5 million data points are permanently stored and available through a public access web platform. The strategies and methodologies are described and, in the Mazatlan observatory, data recovery and basic statistics of eight environmental variables are presented. During 2015, an extreme El Nino year, marine temperatures increased from the bay to the middle Urias coastal lagoon, were h...

Sea level rise, one of the most evident effects of recent climate change, is already impacting coastal ecosystems. Because of its low relief, population increase and economic development during the last century, the Celestun lagoon is highly vulnerable to global change, including sea level rise. Here, we study a sediment core from a tropical saltmarsh to evaluate the impact of sea level rise on sediment accretion and carbon fluxes. Some geochemical indicators in a 210Pb dated sediment core showed clear signals of marine influence. This was reflected on increased accretion rates, from 0.3 ± 0.1 mm yr− 1 in ≈ 1941 to 2.9 ± 1.2 mm yr− 1 in 2012. These accretion rates were similar to eustatic sea level rise, and mean acceleration ranged from 0.037–0.22 mm yr− 2, implying a SLR by 2100 ranging from 14 to 86 cm. The one-century (1917–2013) organic carbon stock in sediments was calculated to be 10.1 ± 0.2 Mg C ha− 1. During the same period, the organic carbon flux, corrected for organic carbon degradation, increased from 7 ± 3 g C m− 2 yr− 1 to 73 ± 26 g C m− 2 yr− 1, attributed to the impact of sea level rise in this ecosystem. This work shows that tropical saltmarshes may provide useful information on sea level rise, and the presented methodology may be used where instrumental records do not exist or they are too short.

Nutrient and chlorophyll-a distributions in the Bay of La Paz, Gulf of California, Mexico were analyzed during the late spring of 2004 to assess their relations to hydrography and circulation patterns. The results show the presence of both Gulf of California Water and Subtropical Subsurface Water. Water circulation was dominated by wind stress driven cyclonic circulation along f / H contours ( f is planetary vorticity and H is depth), and upwelling resulting from the divergence shows a vertical velocity of ∼0.4 m d−1. Nutrient concentrations were higher in the center of the cyclonic pattern, where a rise in the nutricline contributed nutrients to the euphotic layer as a result of Ekman pumping. The vertical section showed the presence of a chlorophyll-a maximum at the thermocline shoaling to a depth of only 12 m. Along the surface, two peaks of chlorophyll-a were observed, one at Boca Grande and another off San Juan de la Costa, associated with upwelling and mixing derived from current interactions with abrupt topographies. The chlorophyll-a maximum increased from 0.8 mg m−3 in the external part of the cyclonic pattern to 2.0 mg m−3 in its center. The vertically integrated chlorophyll-a concentrations followed a similar pattern, rising from 10 to 20 mg m−2 and reaching their highest values in the center of the cyclonic circulation pattern. A schematic model was developed to describe processes that occur in late spring: the wind stress driven cyclonic structure promotes upward nutrient flux, which in turn drives an enhancement of chlorophyll-a. Upwelling was found to be the main mechanism of fertilization responsible for the enhancement of productivity levels by means of nutrient transport into the euphotic zone during spring. Other chlorophyll enhancement areas point to the occurrence of additional fertilization processes that may derive from interactions between cyclonic circulation patterns and the topography off of San Juan de la Costa, where phosphate mining occurs.

The restoration of mangroves has gained prominence in recent decades. Hydrological rehabilitation has been undertaken to connect impaired mangroves with the sea, lagoons or estuaries. Because mangrove hydrodynamics occurs on the surface and interstitial spaces in the sediment, we propose to determine the hydrological flow paths to restore the hydrological regimes of the impaired mangroves. The hydrological flow paths were determined through a micro basin analysis based on microtopographic data to generate a digital elevation model. Applying this methodological approach, the hydrology of an impaired area on a barrier island in the Gulf of Mexico was restored by excavating, desilting or clearing the channels on the identified hydrological flow paths. This area was compared to one in which impaired mangroves were reconnected to the marine lagoon but disregarding the flow paths. Data collected in both areas were evaluated by flood level analysis, using two methods: (i) a simple linear regression model (SLRM) and (ii) spectral analysis (SA), also known as dominant frequency analysis. The results suggest that restoration based on the hydrological flow paths was more effective than the direct opening to the nearest main water body without accounting for the microtopography. In both areas, soil salinity and sulfides decreased after hydrological reconnection. However, a greater efficiency in the investment of time and human resources was achieved when preferential flow paths were identified and taken into account. The methodological procedures described in this study are of universal application to other mangrove restoration programs.

Los manglares de Laguna de Términos, Campeche han sido afectados por la pérdida de la conexión hidrológica durante el paso de tormentas y huracanes. El objetivo de este trabajo fue evaluar la regeneración natural del manglar en un área degradada, después de haber implementado acciones de restauración hidrológica. Se establecieron tres sitios de muestreo con diferentes tiempos de restauración (1 año - 3 años) y un sitio de manglar natural conservado como referencia. El muestreo se realizó en los años 2014 a 2015. Se evaluó densidad, altura, sobrevivencia y tasa de crecimiento de las plántulas, así como las características ambientales. La relación entre la vegetación y las características ambientales se realizaron mediante regresiones lineales simples y un análisis de escalamiento multidimensional. Para determinar la dispersión de propágulos respecto a los manglares naturales, se generó un modelo lineal mixto de la densidad de propágulos vs. la distancia y el tiempo de restauración. Los resultados demostraron que la distancia respecto a los manglares naturales afectó la densidad de los propágulos. La concentración de fosfato se relacionó con la sobrevivencia de las plántulas; mientras que la concentración de amonioy la concentración de sulfuro se relacionaron negativamente con la densidad de las plántulas. Las acciones de restauración hidrológica influyeron en el establecimiento y desarrollo de la vegetación de manglar; por lo tanto, las zonas de manglar natural y la restauración hidrológica facilitaron la dispersión de los propágulos hacia las zonas degradadas, resaltando la importancia de contemplar estas áreas naturales dentro de los proyectos de restauración.

Marine zooplankton play a pivotal position in the pelagic ecosystem and, as one of their principal members, copepods represent by far the most significant direct link between phytoplankton and the higher trophic levels. In this study, observational evidence of the effect of a mesoscale cyclonic eddy on the abundance of copepods (adult calanoids, adult cyclopoids and all copepodite stages) in the Bay of La Paz, southern Gulf of California, a region recognized as exhibiting high biodiversity, is presented. During a multidisciplinary research cruise in February 2006, high-resolution hydrographic profiles were obtained from a grid of stations throughout the bay, and oblique zooplankton hauls were made in its north-central portion. The results showed the presence of a mature mesoscale cyclonic eddy, which extended to 110 m depth and 30 km diameter, reaching a surface azimuthal velocity of 20 cm s–1 at its periphery. Below the mixed layer at 50 m depth this eddy induced a cold-core water dome (~16.25 °C) at its center. Within this cold water dome, nutrients concentrations were much higher than outside the eddy. Nitrate reached up to 15 μM, soluble reactive phosphorous (SRP) up to 1.6 μM, and soluble reactive silicate (SRSi) up to 30 μM within the eddy. The total abundance of the organisms analyzed varied according to group: the calanoid copepods reached values of 8112 ind 100 m–3, the cyclopoid copepods of 4281 ind 100 m–3, and the highest abundance was recorded by all copepodite stages, of 32,076 ind 100 m–3. The influence of the cyclonic structure on copepod abundance was to induce the formation of a circular shape around the eddy periphery, which could be called a ‘copepod belt shape’. We suggest that several mechanisms induce this aggregation, including: 1) the affinity of these organisms for waters with a favorable temperature, and 2) the availability of food (phytoplankton) generated by the presence of the cyclonic eddy and the sub-mesoscale processes there, as well as by the presence of a bathymetric sill. These results represent the first observational report on the influence of a mesoscale cyclonic eddy in the Bay of La Paz on zooplankton organisms in winter, which should contribute to a better understanding of the dynamics of this highly productive area.

For decades, La Redonda lagoon was an excellent location for fishing the largemouth bass (Micopterus salmoides, Lacepède) in Cuba. There are indications that the species disappeared from the lagoon in 2009. Three water surveys were carried out in 2013 and 2014. Physicochemical parameters, including nutrients, were measured in all surveys. Chlorophyllaand water transparency were only measured in November 2013. Results showed that this lagoon is a fresh to brackish water system, with common salinization episodes. There were some hypoxic conditions, but mean dissolved oxygen value was above 5.0 ± 2.8 mg L−1for the entire survey period. The trophic state was evaluated as oligotrophic and Nitrogen and Phosphorus were limiting in most of the survey sites. The Habitat Suitability Index model (HSI) for largemouth bass had a mean value of 0.63 ± 0.02 (moderate degree of suitability). All results showed that bass recovery could be possible in La Redonda lagoon, but management criteria are necessary. The largemouth bass recovery could help to increase visitations of American anglers to this place and a portion of the revenue could be used to conduct environmental monitoring and studies of the largemouth bass ecology in Cuba.

Stable isotopes of nitrogen ( δ 15 N) have been widely used around the world to evaluate the impact of anthropogenic activities on marine ecosystems; however, in the Caribbean Sea countries, such as Mexico and Cuba, they are rarely used. Inputs of nutrients related to urban development and tourist activities along the coasts of the Caribbean Sea have the potential to deteriorate their fragile marine ecosystems. The use of isotopic tools and elemental analysis in sentinel organisms would be useful to provide evidence of the impact generated by anthropogenic nutrients. Measurements of δ 15 N ( ‰ ), carbon and nitrogen content, and C:N ratios, were conducted in different sentinel groups (macroalgae, seagrasses, gorgonians, and corals) collected in five marine ecosystems with different nearby coastal development pressure in both countries. The selected ecosystems, ordered according to the level of coastal areas development (low to high), were: Jardines de la Reina (JR), Gulf of Ana Maria (GAM), Cayo Coco (CC), and Laguna Larga (LL) in Cuba, and Puerto Morelos (PM) in Mexico. Results evidenced that the majority of sentinels inhabiting near the most developed coastal areas, in terms of population and tourism, showed higher N contents, lower C:N ratios and higher values of δ 15 N (e.g., PM and LL) than those near less developed coastal ecosystems (e.g., GAM and JR). Land-based nutrients from municipal wastewater constitute the primary source of N pollution. Because eutrophication represents a significant threat to the integrity of valuable coastal ecosystems, there is an urgent need to accelerate progress in wastewater treatment systems, in terms of capacity and efficiency, to significantly reduce nutrient inputs to coastal ecosystems. Otherwise, more negative changes and deteriorations to the health of coastal ecosystems, including coral reefs, are expected along the Mexican Caribbean and numerous key points of Cuba and other Caribbean countries.

The petrochemical industry and urban activities are widely recognized worldwide as a source of pollution to mangrove environments. They can supply pollutants such as trace elements that can modify the ecosystem structure and associated services, as well as human populations. Through geochemical data, multivariate statistical analysis and pollution indices such as the enrichment factor (EF), geo-accumulation index (Igeo), adverse effect index (AEI) and the pollution load index (PLI), we evaluated the factors that control trace element distribution, punctual sources and determined the pollution level of sediments and their potential biological impact in the mangrove ecosystem of Isla del Carmen, Mexico. The factor and cluster analysis highlighted that the distribution of trace elements is influenced by the mineralogy, texture as well as urban derived sources. The pollution indices showed values in the punctual sources from the urban area of EF > 10, Igeo > 3, AEI > 3, PLI > 1 by Cu, Zn and Pb. Finally, the results revealed that mangroves from Isla del Carmen has a major influence from urban activities and natural sources rather than oil industry and also indicate a degraded environment as a result of anthropogenic activities that could have knock-on effect for human health if polluted marine organisms derived from the urban mangroves are consumed. Capsule abstract Surface sediments show the influence of point sources on selected trace element concentrations correlated with human activities within the mangroves of Isla del Carmen, Mexico.

Marine picophytoplankton has become an important issue to understand the global ecology of phototrophic forms, due to its wide distribution and contribution to biomass and productivity. We studied the abundance, distribution and signature pigments of the prokaryote picophytoplankters Prochlorococcus and Synechococcus during an oceanographic cruise (26 April to 7 May, 2011) in the central Mexican Pacific, a relatively poorly-known oxygen minimum zone (OMZ), and the effect of three environmental gradients. Prochlorococcus and Synechococcus abundances were comparable with those found in other tropical areas (0.17 to 30.37 X 104 cells mL-1, and 0.9 to 30.97 X 104 cells mL-1, respectively). Prochlorococcus abundances reached highest numbers in deeper waters, often coinciding with the second deep in situ fluorescence (and chlorophyll α) maxima, at oceanic stations, below the nitratecline, whereas Synechococcus abundances were higher at subsurface waters and its concentration maxima usually coincided with the subsurface in situ fluorescence maxima, with slightly higher abundances in coastal stations. Statistical analyses support significantly these results. Distribution of divinyl-chlorophyll α was erratic along the water column and occasionally coincided with the deep in situ fluorescence maxima, whereas the distribution of zeaxanthin usually followed that of chlorophyll α and the abundances of Synechococcus, and peaked together. These results are similar to those previously found in the study area and in more temperate zones, and also to the general trend in OMZ, but confirm that the second deep chlorophyll α maxima are attributed to high Prochlorococcus densities. We additionally found the abundance and distribution of Prochlorococcus and Synechococcus strongly driven by the environmental gradients observed. Resumo O picophytoplankton marinho tornou-se uma questão importante para compreender a ecologia global das formas fototróficas, devido à sua ampla distribuição e contribuição para a biomassa e a produtividade. Estudamos os pigmentos de abundância, distribuição e assinatura do picofitoplâncton procarionte Prochlorococcus e Synechococcus durante um cruzeiro oceanográfico no Pacífico central mexicano, uma zona mínima de oxigênio relativamente poco conhecida (OMZ) e o efeito de três gradientes ambientais. As abundâncias de Prochlorococcus e Synechococcus foram comparáveis às encontradas em outras áreas tropicais (0.17 to 30.37 X 104 células mL-1, e 0.9 to 30.97 X 104 células mL-1, respectivamente). As abundâncias de Prochlorococcus atingiram o maior número em águas mais profundas, coincidindo frequentemente com a segunda intensidade de fluorescência in situ profunda (e clorofila a), em estações oceânicas, abaixo da nitratoclina, enquanto as abundâncias de Synechococcus foram maiores nas águas de subsuperficie e sua concentração máxima geralmente coincidiu com os máximos de subsuperficie de fluorescência in situ, com abundâncias ligeiramente mais altas nas estações costeiras. As análises estatísticas suportam significativamente esses resultados. A distribuição da divinil-clorofila a foi errática ao longo da coluna de água e coincidiu ocasionalmente com os máximos de fluorescência in situ profundos, enquanto que a distribuição da zeaxantina seguiu geralmente a da clorofila a e as abundâncias de Synechococcus e atingiu o pico. Estes resultados são semelhantes aos encontrados anteriormente na área de estudo e em zonas mais temperadas, e também à tendência geral na OMZ, mas confirmam que a clorofila profunda a maxima é atribuída a altas densidades de Prochlorococcus. Além disso, encontramos a abundância e distribuição de Prochlorococcus e Synechococcus fortemente conduzida pelos gradientes ambientais observados.

Recent eustatic sea level rise (SLR) is one of the most striking manifestations of recent climate change as it directly impacts coastal activities and ecosystems. Although global SLR is well-known, local values differ due to vertical land motion, and changes in atmospheric pressure, ocean currents and temperatures. Although a reliable estimation of local SLR trends is needed to assess coastal zone vulnerabilities and plan adaptation strategies, instrumental records are usually short or sparse, especially in developing countries. Here we show that 210Pb-dated sedimentary records from mangrove saltmarshes can provide useful decadal records of local SLR trends. We quantified sediment accretion rates in sediment cores from remote mangrove saltmarshes of the Yucatan Peninsula. Best SLR records were observed for cores collected near mean sea level (MSL). During most of the XX century the SLR rate ranged from 1-2 mm yr-1, increased to a maximum of 4.5 ± 0.6 mm yr-1 and the acceleration was 0.13 mm yr-2. Assuming either a constant SLR rate or acceleration, by the end of this century MSL level will be 39 cm or 91 cm above the present value. Both coastal infrastructures and ecosystems will be negatively affected by SLR and society will need to adapt relatively fast to the new conditions.

Long-term and seasonal changes in production and respiration were surveyed in the Valle de Bravo reservoir, Mexico, in a period during which high water-level fluctuations occurred (2006–2015). We assessed the community metabolism through oxygen dynamics in this monomictic water-body affected by strong diurnal winds. The multiple-year data series allowed relationships with some environmental drivers to be identified, revealing that water level-fluctuations strongly influenced gross primary production and respiratory rates. Production and respiration changed mainly vertically, clearly in relation to light availability. Gross primary production ranged from 0.15 to 1.26 gO2 m−2 h−1, respiration rate from −0.13 to −0.83 gO2 m−2 h−1 and net primary production from −0.36 to 0.66 gO2 m−2 h −1 within the production layer, which had a mean depth of 5.9 m during the stratification periods and of 6.8 m during the circulations. The greater depth of the mixing layer allowed the consumption of oxygen below the production layer even during the stratifications, when it averaged 10.1 m. Respiration below the production layer ranged from −0.23 to −1.38 gO2 m−2 h−1. Vertically integrated metabolic rates (per unit area) showed their greatest variations at the intra-annual scale (stratification-circulation). Gross primary production and Secchi depth decreased as the mean water level decreased between stratification periods. VB is a highly productive ecosystem; its gross primary production averaged 3.60 gC m−2 d−1 during the 10 years sampled, a rate similar to that of hypertrophic systems. About 45% of this production, an annual average net carbon production of 599 g C m−2 year−1, was exported to the hypolimnion, but on the average 58% of this net production was recycled through respiration below the production layer. Overall, only 19% of the carbon fixed in VB is buried in the sediments. Total ecosystem respiration rates averaged −6.89 gC m−2 d−1 during 2006–2015, doubling the gross production rates. The reservoir as a whole exhibited a net heterotrophic balance continuously during the decade sampled, which means it has likely been a net carbon source, potentially releasing an average of 3.29 gC m−2 d−1 to the atmosphere. These results are in accordance with recent findings that tropical eutrophic aquatic ecosystems can be stronger carbon sources than would be extrapolated from temperate systems, and can help guide future reassessments on the contribution of tropical lakes and reservoirs to carbon cycles at the global scale. Respiration was positively correlated with temperature both for the stratification periods and among the circulations, suggesting that the contribution of C to the atmosphere may increase as the reservoirs and lakes warm up owing to climate change and as their water level is reduced through intensification of their use as water sources.