Tropical Coastal Lagoon Research Articles

Effects of recent urbanization on carbon and nitrogen burial rates of sedimentary records in a tropical coastal lagoon (Brazil)

Land use and land cover changes (LULCC) are a global environmental issue that has impacted biogeochemical cycles worldwide. Sedimentary records can demonstrate the effects of LULCC on aquatic ecosystems, where the recent urbanization has been linked to changes in carbon and nitrogen burial. In this study, we reconstructed long-term LULCC and sedimentary records of carbon (C), nitrogen (N), phosphorus (P), and sediment burial rates in a eutrophic tropical coastal lagoon affected by recent urban expansion. Based on analyses of 30 years of satellite imagery and sedimentary records from 1932 to 2013, we revealed that urban expansion over low-productivity agricultural-pasture areas increased siltation and C, N, P concentrations and fluxes in the coastal lagoon. Large temporal variability of such parameters revealed not only the effects of LULCC on the lagoon's burial rates, but also the influence of artificial sand barrier openings, which connect the studied lagoon to the sea, reducing C, N, P, and particle deposition in the sediment. Our results support multi-proxy methods to assess the relationships between recent urbanization, rising C, N, and P burial rates, and the eutrophication process. We highlight that artificial sandbar openings, the current eutrophication management strategy for coastal lagoons, are ineffective in reducing the eutrophication state, even in the recent scenario of decreasing C, N, and P burial rates.

Carbon and nitrogen sources in tropical coastal lagoon food webs under variable hydrological conditions

Whilst the impact of continental and marine nutrient sources on the ecological functioning of coastal food webs is well investigated in temperate regions, tropical ecosystems remain less well understood, in particular coastal lagoons. In this study, the sources of carbon and nitrogen in a coastal lagoon system in the southeast of Madagascar are traced using stable isotopes of carbon (δ13C) and nitrogen (δ15N). Three interconnected coastal lagoons with different degree of river influence and eutrophication are investigated. Their food webs are assessed with respect to spatial and seasonal (wet and dry seasons) variations in lagoon water conditions, as well as with respect to the sources of nutrients and organic matters. Results show that river input is the main source of NO3−, and that NO3− supply is significantly higher during the wet season. In contrast, NH4+ is produced internally in the lagoon, and concentrations are higher during the dry season. A lower δ13C value observed in particulate organic matter (POM; proxy of phytoplankton) indicates terrestrial-riverine carbon inputs, which generally have low δ13C values. During the dry season, exceptionally high δ15N values of lagoon POM suggest the uptake of newly produced lagoon water NH4+ and/or the 15N enrichment of lagoon POM pool due to mineralization, resulting in 15N enrichment in consumers. Moreover, δ13C and δ15N values of consumers (fishes and invertebrates) reflect predominantly those of lagoon POM and sediment organic matter (SOM), suggesting that consumers primarily depend on lagoon POM and SOM as sources of carbon and nitrogen. The δ15N values in consumers further indicate that some species feed on more than one trophic level, suggesting flexible foraging strategy of consumers as a function of food source availability. This study demonstrates the roles of both river inflow and sediment in supplying carbon and nitrogen to a coastal lagoon food web, documenting the ecological implications of seasonal variations in lagoon hydrological conditions.

Potentially pathogenic bacteria in the plastisphere from water, sediments, and commercial fish in a tropical coastal lagoon: An assessment and management proposal

Microplastics in aquatic ecosystems harbor numerous microorganisms, including pathogenic species. The ingestion of these microplastics by commercial fish poses a threat to the ecosystem and human livelihood. Coastal lagoons are highly vulnerable to microplastic and microbiological pollution, yet limited understanding of the risks complicates management. Here, we present the main bacterial groups, including potentially pathogenic species, identified on microplastics in waters, sediments, and commercial fish from Ciénaga Grande de Santa Marta (CGSM), the largest coastal lagoon in Colombia. DNA metabarcoding allowed identifying 1760 bacterial genera on microplastics, with Aeromonas and Acinetobacter as the most frequent and present in all three matrices. The greatest bacterial richness and diversity were recorded on microplastics from sediments, followed by waters and fish. Biochemical analyses yielded 19 species of potentially pathogenic culturable bacteria on microplastics. Aeromonas caviae was the most frequent and, along with Pantoea sp., was found on microplastics in all three matrices. Enterobacter roggenkampii and Pseudomonas fluorescens were also found on microplastics from waters and fish. We propose management strategies for an Early Warning System against microbiological and microplastic pollution risks in coastal lagoons, illustrated by CGSM. This includes forming inter-institutional alliances for research and monitoring, accompanied by strengthening governance and health infrastructures.

Eastern oyster (Crassostrea virginica) nursery production in tropical coastal lagoons in Yucatán, Mexico: nonlinear regression modeling and relationships with environmental variables

Eastern oyster (Crassostrea virginica) nursery production in tropical coastal lagoons in Yucatán, Mexico: nonlinear regression modeling and relationships with environmental variables

Microprotozooplankton as eutrophication bioindicator for tropical coastal lagoons

Microprotozooplankton as eutrophication bioindicator for tropical coastal lagoons

Stochastic modeling of eastern oyster (Crassostrea virginica) production in a Mexican tropical coastal lagoon using alternative stocking density management schemes

A stochastic model was developed to analyze Crassostrea virginica production when cultivated at three stocking densities, defined as the area occupation (50, 75, and 100%) in Nestier-type trays, using juvenile oysters with an initial size (height) of 29.40 ± 0.18 mm. A 25-week grow-out was first conducted in the Rio Lagartos lagoon, showing that final oyster size was inversely related to density (P < 0.05), ranging from 61.87 mm (100% density) to 68.00 mm (50% density). At the same time, mortality was negligible (lower than 1.0%). The environmental conditions in the lagoon were stable, and the oyster growth rate positively correlated with water temperature and pH. Low pH was associated with slow oyster growth, possibly as an adverse effect of acidic conditions on the oyster shell formation. The model indicated that, for an initial 100,000 oyster population, the maximum production (oyster dozens) is obtained after 20 weeks (8310 at 50% density) and 25 weeks (8250 at 75%, and 6670 at 100% density). There was a 100% probability of oysters reaching a minimum commercial size (MCS) of 60.00 mm when using the 50 and 75% densities and 80.6% when using 100%. The model estimated that, for the maximum density, extending the grow-out up to 32 weeks would allow reaching MCS with 100% probability, although this should be experimentally confirmed. The random variability of oyster production in 50 and 75% densities was minimal, while at 100% density, it was extremely high. A sensitivity analysis indicated that for 50 and 75% densities, the main stochastic elements influencing production, are related to oyster mortality, while at 100% density, they are related to oyster growth.

Site selection for farming the oyster Saccostrea cucullata in a tropical coastal lagoon

This study investigates the influence of variable environmental conditions on the growth of the natural rock oyster (hooded oyster) Saccostrea cucullata in the river-fed Ambinanibe coastal lagoon (Madagascar), with the objective to establish sites with optimal growth conditions for aquaculture purposes. Specimen marked with manganese were placed in cages over an approximately one-year period. The cages were installed at four sites i.e. one at the river mouth, two sites within the main lagoon and one site in an adjacent connected lagoon, which is out of river influence and considered as the control site. Multiple mark and recapture experiments were used to investigate the variations in growth rate and condition index (tissue weight/shell weight). The results show that the species overall exhibits a fast growth rate at a young age, with a gradual growth reduction with age. The hinge growth rate shows important spatial and seasonal variations in the lagoon. Oysters from the site located at the river mouth have the highest hinge growth rate (20.5 ± 13.6 µm d−1) and condition index (4.5 ± 2.8 %) while those from the control site out of river and ocean influences exhibit the lowest hinge growth rate (7.7 ± 4.2 µm d−1) and condition index (0.7 ± 0.6 %), suggesting that river freshwater inflow provides suitable environmental conditions for oyster growth and a profitable oyster farming is thus feasible. River inflow is an important external source of nutrients, providing thus a significant food source (phytoplankton), as well as suitable temperature and salinity conditions for S. cucullata in this lagoon. Overall, our results show that oyster market size (shell length: 40 mm) in Madagascar can be reached faster at the river-influenced site (in 8 months) in comparison with the other sites (in 1 – 1.2 years), indicating that the river-impacted site is well suitable for oyster farming.

Inter-annual and seasonal variations of the metazoan parasite communities of the blue sea catfish Ariopsis guatemalensis (Siluriformes: Ariidae), in a tropical coastal lagoon

Parasitological studies of long-term inter-annual variations provide more precise and reliable information about the biological structure of fish parasite communities, and constitute a reference data base for future studies. A total of 1103 blue sea catfish Ariopsis guatemalensis from a tropical eutrophic coastal lagoon were examined for parasites over a 22-year period (from May 2000 to October 2022), to test the hypothesis that parasite communities of this host, should exhibit greater variations in their structure and species composition mainly over long-term periods. Three species of monoxenous (single-host life cycle), and nine of heteroxenous (multi-host life cycle) parasites were identified. The results indicated that parasite species composition of this catfish has remained stable over a 22-years period. However, the community structure has registered notable changes over periods of several years, mainly due to the replacement of the numerically dominant species. Temporal variations in the infection dynamics of component parasite species, were possibly caused by a combination of biotic and abiotic factors, influenced by the seasonal dry/rainy cycle, which can affect the availability of intermediate host populations, as well as the feeding and reproductive behavior of the host.

Impact of mangrove on tidal propagation in a tropical coastal lagoon

Impact of mangrove on tidal propagation in a tropical coastal lagoon

WITHDRAWN: Marine intrusions drive short-term and long lasting changes on limnological dynamics along the water column of a tropical coastal lagoon

WITHDRAWN: Marine intrusions drive short-term and long lasting changes on limnological dynamics along the water column of a tropical coastal lagoon

Ontogenetic changes in green turtle (Chelonia mydas) diet and home range in a tropical lagoon

Ontogenetic changes in habitat and diet are widespread among marine species. Most species of sea turtles are characterized by extreme ontogenetic changes in habitat use and diet, with large changes occurring in early developmental stages (e.g., neonates to juveniles). Changes can continue even after recruitment to shallow coastal habitats. In places where substantial transitions in habitat occur across short distances, it is possible that the distances of developmental movements from one habitat to another could be short. We investigated ontogenetic changes in home range size, home range location and diet of Chelonia mydas in a tropical coastal lagoon in north-western Australia by combining acoustic telemetry with stable isotope analysis. There was a substantial (but nonlinear) increase in home-range size (kernel utilization distribution: KUD) with length, and an increase in the average distance of the center of home ranges from shore with length: larger turtles tended to occupy larger areas further from the shore. These patterns were accompanied by complex nonlinear changes in δ13C, δ15N and δ34S of red blood cells and nails; changes were rapid from 36 cm (the length of the smallest individual captured) to 50 cm, before reversing more gradually with increasing size. δ15N and δ34S (but not δ13C) of red blood cells and nails increased monotonically with KUD and distance from shore. Seagrass was likely an important food for all sizes, macroalgae was potentially important for small (< 60 cm CCL) individuals, and the proportion of scyphozoan jellyfish in diet increased monotonically with size. The combination of acoustic telemetry and stable isotope analysis revealed ontogenetic shifts in use of space and diet across short distances in a tropical coastal lagoon.

Assessing stability of tidal inlet in a tropical coastal lagoon

Assessing stability of tidal inlet in a tropical coastal lagoon

Phosphorus spatial distribution and mass balance in the Itaipu lagoon (Rio de Janeiro, Brazil)

The degradation of tropical coastal lagoon systems in urban areas of the least developed countries has been associated with an increase in impermeable areas and poor domestic sewage treatment, increasing land-based runoff of nutrients and suspended solids from catchments. This study aimed to assess the biogeochemical changes caused by human interventions through the analysis of the spatial distribution of sedimentary phosphorus (P) and its mass balance in the Itaipu lagoon, located on the east coast of the state of Rio de Janeiro. Human intervention in the Itaipu lagoon system has caused severe imbalances in biogeochemical cycles over the past decades. Watercourses have been channeled to normalize the hydrological regime and increase hydraulic energy, improving sediment transport capacity. In this context, the increase in runoff from the coastal urban basin into the Itaipu lagoon has buried an increasing amount of phosphorus in the sediment. Recently, a regional increase in storm events caused a series of landslides and floods, which have been reported as possible consequences of global climate change. In recent decades, the synergy between landslides and river channeling has increased TP loads, accelerating phosphorus settling and changing P spatial distribution in surface sediments. This has accelerated siltation of the lagoon with an accumulation of nutrients and organic matter, leading in some cases to sediment anoxia. The lagoon has undergone strong eutrophication, changing its trophic state from meso- to hypertrophic in less than 30 years, even though P loads are not as high as in other coastal lagoons. Our findings confirm that human intervention impacts nutrient loads, which in turn disrupt the balance of biogeochemical cycles, compromising coastal water resources. This leads to the collapse of ecosystem services, another step towards degrading planetary boundaries.

Coastal micro-phytoplankton community changes during the toxigenic Alexandrium minutum blooms in a semi-enclosed tropical coastal lagoon (Malaysia, South China Sea)

Estuarine lagoons often experience eutrophication due to anthropogenic activities in proximity and poor water exchange. Deterioration of water quality in the lagoon has driven the shifts in micro-phytoplankton communities that often form coastal harmful algal blooms (HABs). This study investigated changes in the micro-phytoplankton community in a tropical semi-enclosed lagoon, Geting Lagoon, for two consecutive years during the study periods of 2014/2015 (September 2014–March 2015) and 2015/2016 (August 2015–March 2016). A total of 38 phytoplankton taxa were identified throughout the sampling periods, with 17 taxa of harmful algae identified microscopically. The diatoms Skeletonema costatum and Chaetoceros were predominant in the lagoon. The lagoon was significantly enriched in macronutrients, and high overall nitrogen and phosphorous concentrations likely supported substantial phytoplankton blooms in the lagoon throughout the studied periods. It was observed that with similar temperatures and nutrient availability between the 2014/2015 and 2015/2016 periods, the density of A. minutum in 2014/2015 did not reach as high as in those of the 2015/2016 period, in which higher precipitations, streamflow, and decreased in salinity stratification index had prevented the development of A. minutum bloom. The findings of this study revealed that the coastal micro-phytoplankton community was dependent on the interplay of environmental variables and unique strategic adaptations of the functional types in the assemblages. This study provides valuable insights into the phytoplankton community dynamics in a tropical eutrophic lagoon.

Co-occurrence patterns and environmental factors associated with rapid onset of Microcystis aeruginosa bloom in a tropical coastal lagoon

The environmental factors contributing to the Microcystis aeruginosa bloom (hereafter referred to as Microcystis bloom) are still debatable as they vary with season and geographic settings. We examined the environmental factors that triggered Microcystis bloom outbreak in India's largest brackish water coastal lagoon, Chilika. The warmer water temperature (25.31–32.48 °C), higher dissolved inorganic nitrogen (DIN) loading (10.15–13.53 μmol L−1), strong P−limitation (N:P ratio 138.47–246.86), higher water transparency (46.62–73.38 cm), and low-salinity (5.45–9.15) exerted a strong positive influence on blooming process. During the bloom outbreak, M. aeruginosa proliferated, replaced diatoms, and constituted 70–88% of the total phytoplankton population. The abundances of M. aeruginosa increased from 0.89 × 104 cells L−1 in September to 1.85 × 104 cells L−1 in November and reduced drastically during bloom collapse (6.22 × 103 cells L−1) by the late November of year 2017. The decrease in M. aeruginosa during bloom collapse was associated with a decline in DIN loading (2.97 μmol L−1) and N:P ratio (73.95). Sentinel-3 OLCI-based satellite monitoring corroborated the field observations showing Cyanophyta Index (CI) > 0.01 in September, indicative of intense bloom and CI < 0.0001 during late November, suggesting bloom collapse. The presence of M. aeruginosa altered the phytoplankton community composition. Furthermore, co-occurrence network indicated that bloom resulted in a less stable community with low diversity, inter-connectedness, and prominence of a negative association between phytoplankton taxa. Variance partitioning analysis revealed that TSM (16.63%), salinity (6.99%), DIN (5.21%), and transparency (5.15%) were the most influential environmental factors controlling the phytoplankton composition. This study provides new insight into the phytoplankton co-occurrences and combination of environmental factors triggering the rapid onset of Microcystis bloom and influencing the phytoplankton composition dynamics of a large coastal lagoon. These findings would be valuable for future bloom forecast modeling and aid in the management of the lagoon.

Terrestrial or oceanic forcing? Water level variations in coastal lagoons constrained by river inflow and ocean tides

The study concerns the water level (WL) evolution in lagoons under the influence of tides and river fluxes. We derive new approximate analytical solutions of the Stigebrandt (1980) equations and apply them to the Nokoué Lagoon (Benin), a large tropical coastal lagoon fed by substantial river input. We show the solutions accurately predict the mean WL and tide amplitude. In particular the nonlinear combination of the spring-neap tidal cycle and river inflow gives rise to a strong fortnightly variation of the mean WL. The analytical solutions are used to explain this phenomenon. We also calculate the phase shift between the ocean and the lagoon tides and the asymmetry of the ebb and flood tide duration in the lagoon. The asymmetry first increases with the river flux but reduces above a critical flux before becoming symmetric again at river flood peaks.Finally, the analytical solutions are inverted to estimate the net river fluxes entering the Nokoué Lagoon, where no observations are available for rivers but for which we have high frequency observations of the lagoon water level for 2 years. The model is calibrated using few available flux observations in the channel connecting the lagoon to the ocean. Realistic river fluxes are estimated. We subsequently calculate the lagoon WL variations using the simplified model forced with the recalculated river fluxes and tidal forcing from an ocean tide model. The solution accurately represents the observations over the 2 year time period of the study. We conclude that this simple model is able to represent the complex interaction of tides and river fluxes, and its influence on the low frequency WL variations of coastal lagoons.

Estuarine fishes feeding on benthic invertebrates and small fishes: Evidence of fine resource partitioning in a tropical coastal lagoon

The main goal of the present study was to carry out an integrated analysis of the feeding habits of a set of species which use the same general food source (benthic invertebrates and small fishes) in a coastal lagoon of the Mexican Pacific. The specific objectives were to explore the patterns of diet overlap among the 12 species included; to relate the differences in diet composition with differences in species morphology and to measure the predator-prey size relationship across the whole set of species. Original primary data on diet composition were obtained from former research whose results were already published in five separated papers dealing with different species or groups of species. Data included information on stomach content (percentage weight) from a total of 2138 individuals pertaining to 12 species (nine of them further split in size groups) and 3953 pairs of prey's size vs predator's size measurements. Eight prey categories made 74% of all food consumed, namely non-identified fishes, penaeids, gobiids, polychaeta, alpheids, upogebiids and engraulids. Using a combination of diet overlap testing based on a null model approach, multivariate methods and regression analyses (linear and quantile), it is concluded that the existence of a relatively homogenous functional group of 12 fish species consuming invertebrates and small fishes is not a realistic assumption. Indeed, several species-size group subsets are clearly identifiable based on the percentage of different prey categories in their diets. The most plausible explanation for the observed patterns of diet composition are the differences in morphological characteristics of the species involved. Other factors allowing the sharing of food resources are the ontogenic change in the size of main prey consumed, notable differences in the abundance of fish species with higher diet overlap values and, perhaps, a high abundance of food resources.

Spatial-Temporal Distribution of Prorocentrum concavum Population in Relation to Environmental Factors in Xincun Bay, a Tropical Coastal Lagoon in China

A harmful benthic Prorocentrum concavum bloom was recorded in August 2018 in Xincun Bay, China, which is the location of a national seagrass nature reserve. Annual ecological surveys have been conducted to study the population dynamics of P. concavum in the benthic community and water column. Seasonal variations in benthic P. concavum abundance were found and the abundances on seagrass and macroalgae in the wet season were 2.5 and 2.82 times higher, respectively, than those in the dry season, although the differences were not statistically significant. The abundance of P. concavum in the water column differed significantly between seasons. The maximum abundances of benthic and planktonic P. concavum were (1.7 ± 0.59) × 106 cells (100 cm2)−1 on Thalassia hemperichii in July and 2.0 × 104 ± 4.7 × 103 cells L−1 in June, respectively. High spatial heterogeneity in P. concavum abundance was observed among five sampling sites. Abundances were significantly higher in seagrass beds than those in macroalgae beds, mangroves, and coral reefs. The abundance of P. concavum at site A (in a seagrass bed and close to a cage-culture area) was 5.6 times higher than that at site D (seagrass bed and distant from the cage-culture area). Planktonic P. concavum showed a similar spatial distribution and presented a maximum density at site A. Moreover, the abundance of benthic P. concavum also showed heterogeneity on host substrates, and the abundance on T. hemperichii was significantly higher than that on sediment. Based on a Spearman’s test, temperature, dissolved organic phosphorus, and dissolved organic nitrogen were the three important factors driving the spatiotemporal distribution of benthic P. concavum in Xincun Bay. Planktonic P. concavum were derived from cells on the substrates and were influenced by concentrations of dissolved oxygen. In conclusion, seagrass beds may be a reservoir of harmful benthic algal blooms in Xincun Bay and the dense cage-culture area provides sufficient organic nutrients for the growth and reproduction of benthic dinoflagellates.

Monitoring of benthic eukaryotic communities in two tropical coastal lagoons through eDNA metabarcoding: a spatial and temporal approximation

Tropical coastal lagoons are important ecosystems that support high levels of biodiversity and provide several goods and services. Monitoring of benthic biodiversity and detection of harmful or invasive species is crucial, particularly in relation to seasonal and spatial variation of environmental conditions. In this study, eDNA metabarcoding was used in two tropical coastal lagoons, Chacahua (CH) and Corralero (C) (Southern Mexican Pacific), to describe the benthic biodiversity and its spatial–temporal dynamics. The distribution of benthic diversity within the lagoons showed a very particular pattern evidencing a transition from freshwater to seawater. Although the two lagoon systems are similar in terms of the species composition of metazoans and microeukaryotes, our findings indicate that they are different in taxa richness and structure, resulting in regional partitioning of the diversity with salinity as the driving factor of community composition in CH. Harmful, invasive, non-indigenous species, bioindicators and species of commercial importance were detected, demonstrating the reach of this technique for biodiversity monitoring along with the continued efforts of building species reference libraries.

Comparison of Phenolic and Flavonoid Content and Antioxidant and Chelating Activities of Rhizophora mangle in Different Anthropogenically-Polluted Coastal Lagoons

The production of total phenolic content (TPC) and total flavonoid content (TFC), antioxidant (AA), and copper chelating (CACu+) activities of Rhizophora mangle from three coastal lagoons under different grades of anthropogenic pollution and pollutant presence were analyzed. R. mangle is a mangrove plant that inhabits tropical coastal lagoons and shows the ability to accumulate pollutants in their tissues and respond to environmental stressors via the production of secondary metabolites AA and CACu+ activities. In total, 108 samples (June 2010 to August 2011) of leaves, barks, and the roots of R. mangle from Magdalena Bay (MBAY), Navachiste Lagoon (NLAG), and Terminos Lagoon (TLAG) (Mexico) were collected. Folin-Ciocalteu colorimetric, aluminum chloride colorimetric, ABTS∙+ discoloration, and pyrocatechol-violet methods calculated TPC, TFC, AA, and, CACu+, respectively. Atomic absorption spectrometry, gas chromatography, and Walkley–Black methods were used to calculate the metal content, organochlorine pesticides (OCPs), and organic matter (OM) in sediments. One-way ANOVA and post hoc Tukey’s, Scheffé’s, and Bonferroni and Holm multiple comparisons were used to determine significance, and Pearson’s test was applied to determine the coefficient of correlations. Significant differences among the lagoons of TPC, TFC, AA, and Cu+CA activities of Rhizophora mangle are explained by their different grades and type of anthropogenic pollution. A significant increase in the TPC and TFC in bark implies a response to the metal and OCPs pollution in surrounding sediments. Significant AA and Cu+CA activities responded to combat environmental stress conditions caused by the OCP and trace metal concentrations in surrounding sediments. Strong and positive correlations among OCP and trace metal were found and related to the constant pesticide residues input. However, OCP concentrations in the surrounding sediments of R. mangle trees did not influence the phenolic production of AA or the Cu+ CA. R. mangle is affected by the type of anthropogenic pollutants and was reflected in the bio-compounds production, antioxidant, and chelating activities related to the concentration of the metals in sediments.