Tropical Coastal Lagoon Research Articles

Influence of habitat structure and environmental regime on spatial distribution patterns of macroinvertebrate assemblages associated with seagrass beds in a southern Gulf of Mexico coastal lagoon

Seagrass meadows are important for their ecological functions and ecosystem services, including habitat and shelter for a high diversity of species. The present study aims to assess the spatial distribution patterns of macroinvertebrate assemblages associated with Thalassia testudinum beds in a tropical coastal lagoon of the southern Gulf of Mexico. Environmental variables and core samples were taken from three shallow beds with different degrees of exposure to wind-driven waves: protected, exposed and semi-exposed. A total of 40 benthic macroinvertebrate species were recorded, molluscs being the most important group in terms of diversity and abundance. The highest species richness was recorded at the semi-exposed site (31 species), while the highest abundance was at the exposed site (5207 ind. m−2). Despite inter-site variations in environmental variables and physical descriptors of seagrass (seagrass biomass, shoot density, leaf length), the species richness and abundance of macroinvertebrates correlated only with seagrass biomass. Multivariate analyses showed a clear separation of macroinvertebrate assemblages into two main groups according to the degree of exposure of the sites as exposed/semi-exposed or protected. It was also determined that seagrass biomass, hydrodynamism, sedimentation/resuspension rates and the proportion of coarse particles in the sediment appear to be the variables that best explain the differences between sites. These findings support the importance of including sites with different degrees of exposure in assessing the biodiversity of seagrass beds at the landscape scale, because species composition, species richness and the abundance of associated fauna may vary considerably between sites within the same coastal region according to a combination of biotic and abiotic factors.

Thermal Impact from a Thermoelectric Power Plant on a Tropical Coastal Lagoon

Tropical coastal areas are sensitive ecosystems to climate change, mainly due to sea level rise and increasing water temperatures. Furthermore, they may be subject to numerous stresses, including heat releases from energy production. The Urias coastal lagoon (SE Gulf of California), a subtropical tidal estuary, receives cooling water releases from a thermoelectric power plant, urban and industrial wastes, and shrimp farm discharges. In order to evaluate the plant thermal impact, we measured synchronous temperature time series close to and far from the plant. Furthermore, in order to discriminate the thermal pollution impact from natural variability, we used a high-resolution hydrodynamic model forced by, amongst others, cooling water release as a continuous flow (7.78 m3 s−1) at 6 °C overheating temperature. Model results and field data indicated that the main thermal impact was temporally restricted to the warmest months, spatially restricted to the surface layers (above 0.6 m) and distributed along the shoreline within ∼100 m of the release point. The methodology and results of this study can be extrapolated to tropical coastal lagoons that receive heat discharges.

Integrating fishermen knowledge and scientific analysis to assess changes in fish diversity and food web structure

In this paper the Ecosystem Approach to Fisheries (EAF) and the Fishermen Knowledge Approach (FKA) were applied to understand changes in a tropical coastal lagoon. Then, the fishermen experience-based knowledge, literature information and data sampling were combined aiming to understand biodiversity loss and food web changing in their fishing environment exposed to the introduction of an invasive fish species. Fishermen indicated the changes in fish species composition and simplification in trophic web, confirming biological data. However they do not attributed changes to the species introduction (our ecological hypothesis previously assumed), but to the sequential construction of bridges that interrupted water flow between the lagoon and the ocean (their environmental hypothesis). This assertion fitted to Ecopath model simulations outputs in which exotic species removal from the ecosystem does not recovery fish composition or the trophic web complexity. Fishermen recalled as larger as smaller species, the matching between food web described by fishermen and the food web from literature and the justification for biodiversity loss presented by fishermen, broadened the confidence on their role as experts. This approach merged the historical views of fishermen and provided evidence on the value of complement scientific data with experts consulting.

Spatiotemporal variations of zooplankton community in a shallow tropical brackish lagoon (Sontecomapan, Veracruz, Mexico)

We studied the relationships between zooplankton distribution and environmental and trophic factors (abiotic variables, nutrients, bacterial biomass, and chlorophyll pigments) from three sampling surveys carried out during the three hydrological seasons (rainy, dry, and norte) in a tropical coastal lagoon connected to the sea. Twenty eight (28) of the 54 taxa recorded were identified to species level, of which 3 genera of Cladocera were observed for the first time in the lagoon. Season-specific differences were highly significant. The overall zooplankton abundance was significantly higher during the dry season (157,000 ind.m−3) than those during the rainy and norte surveys (means of 11,600 and 16,700 ind.m−3 respectively). Copepoda (mostly nauplii) was the most abundant group (>83%) of total zooplankton abundance. Multivariate (coinertia) and multilinear regression analyses showed that transparency, salinity, temperature, pH, and food availability (Chl a, b, and c) were the main determinants of zooplankton abundance, composition, and diversity, explaining the seasonal differences. The relatively low zooplankton density in the lagoon compared to other eutrophic lagoons is attributed to the combined effects of high water exchanges, low depth, and high transparency, which favor instability and vulnerability to UV effects and/or to visual predation.

Nuevo registro de Lagodon rhomboides (Pisciformes: Sparidae) como hospedero de Cymothoa excisa (Isopoda: Cymothoidae) en la costa noroeste de la península de Yucatán

This study reports for the first time the pinfish, Lagodon rhomboides, as a host of the isopod Cymothoa excisa, and shows the influence of parasitism in the morphometric growth of the pinfish obtained from La Carbonera, a tropical coastal lagoon on the northwestern coast of the Yucatán Peninsula, Mexico. A total of 448 pinfish were collected between April 2009 and March 2010. Twenty-eight individuals were found to host the parasite, with a prevalence of 6.2%. Additionally, we obtained the length-weight relationships (W=a Ltb) between individuals with parasites (a=0.0005; b=2.31) and those without (a=0.00003; b=2.91). Parameters a and b differed between groups (p<0.05). The population of L. rhomboides is affected by the presence of the isopod parasite, C. excisa; differences in the length-weight relationship indicates that C. excisa is a risk factor for this and other fish species in the study area.

In Situ Response of Phytoplankton to Nutrient Additions in a Tropical Coastal Lagoon, (La Mancha, Veracruz, Mexico)

An experimental in situ microcosm study was conducted in the tropical lagoon La Mancha (Gulf of Mexico) to determine whether or not nutrient limitation occurs and to examine the direct effect of an inorganic nutrient pulse on the phytoplankton community structure. The phytoplankton community response to the addition of four treatments with different combinations of nitrogen (N), phosphorus (P), and silica (Si) (+N-NH4 +, +P-PO4 −, +Si-SO3, and N:P16) showed that phytoplankton was N-limited as indicated by an increase in phytoplankton biomass (i.e., chlorophyll a) (range, 8–34 mg m−3) during the dry season in two consecutive years (2006 and 2007). Picophytoplankton abundance significantly increased in the +N treatment (145.46 103 cells L−1), while microphytoplankton reached a maximum abundance (68.38 103 cells L−1) in the N:P16 treatment. Phytoplankton composition changed from a community initially dominated by dinoflagellates (e.g., Prorocentrum spp.) to another dominated by diatoms (Thalassiosira and Nitzschia longissima) in the N:P16 treatment. The +N treatment significantly increased Synechococcus sp. growth rates (1.3 divisions per day) (picocyanobacteria). Biomarker pigments measured in the experimental microcosms confirmed observed changes in phytoplankton groups. Our results reveal that La Mancha lagoon is a N-limited coastal system during the dry season and provides evidence of the temporal species successional patterns and mechanisms regulating the phytoplankton community response to nutrient enrichment pulses in this already eutrophic coastal lagoon.

Length-weight relationships and growth parameters of two endemic fish species (Floridichthys polyommusHubbs, 1936 andFundulus persimilisMiller, 1955) from the Yucatan Peninsula, Mexico

This study reports length-weight relationships and growth parameters for Floridichthys polyommus Hubbs, 1936 and Fundulus persimilis Miller, 1955 from La Carbonera, a karstic tropical coastal lagoon on the northwestern coast of the Yucatan Peninsula, Mexico. Specimens were collected between April 2009 and March 2010. The resulting length-weight relationship for F. polyommus was: W = 0.0180 Lt3.37 and W = 0.0142 Lt3.35 for F. persimilis. This study presents the first estimation for both species of the von Bertalanffy growth model parameters, the growth performance index, the L50, and is the first report of the length-weight relationship for F. persimilis.

The negative effects of temperature increase on bacterial respiration are independent of changes in community composition

Temporal changes in environmental conditions and in bacterial community composition (BCC) regulate bacterial processes and ecosystem services. An increase in temperature accelerates bacterial processes in polar or temperate regions, but this relationship has not been documented for the tropics. Here, we tested the interactive effects of changing the BCC and increasing the water temperature on tropical bacterial respiration (BR). The BCC was manipulated through successional changes of the bacterial community in a filtered water sample from a tropical coastal lagoon. Four succession incubation periods (120, 240, 288 and 336 h) and four different water temperatures (23, 28, 33 and 38(o)C) were tested in a full-factorial design microcosm experiment. Both the BCC and the temperature had significant individual, but not interactive, effects on BR. Temperature increasing consistently decreased BR, while there was no clear pattern of successional effects on BR observed. No BCC tested was able to diminish the negative effects of temperature increases on BR. Our results suggest that the effects of an increasing temperature can negatively affect BR, even in tropical ecosystems with different BCC.

Consequences of sea level and climate changes on the morphodynamics of a tropical coastal lagoon during Holocene: An evolutionary model

Vembanad Lagoon is the largest backwater system in the southwestern coast of India, and it is one of the wetlands of international importance, as defined by the Ramsar Convention. The coastal area encompassing the Vembanad Lagoon comprises a spectrum of barrier islands, ridges and swales, lagoons, and flood plains. The lagoon and its adjoining coastal lands are known for economically viable deposits of ilmenite rich beach placers, lime shells, and high purity silica sands. The sedimentological, palynological, and geochronological studies reveal that the sea level and climate changes have brought significant modifications in the geomorphic settings of the system. The depositional regimes and the evolutionary phases showed marked differences in the northern and southern reaches of the Lagoon. The geomorphological settings, occurrence of a suite of major heavy minerals (sillimanite + opaque) and predominance of marine elements in the palynological assemblage in the southern reach of the lagoon are indicative of barrier spit development, which is further influenced by reworked Neogene sediments with characteristic sillimanite–opaque heavy mineral suite of khondalitic affinity. The northern half evolved during the transgressive–regressive events of Early–Middle Holocene from a sheltered coastal water body surrounded by thick coastal vegetation. The opaque–inosilicate dominant heavy mineral suite in the northern sector indicates contribution of sediments from charnokitic source rocks in the area north of the Achankovil Shear Zone. The proposed four stage evolutionary model of the Vembanad Lagoon indicates that it evolved from an embayment of the Arabian Sea by the progradation and development of a barrier spit during transgressive–regressive cycles under heavy rainfall events of the Holocene.

Temporal variation, growth and natural mortality of two species of mojarras (Perciformes: Gerreidae) from a tropical coastal lagoon: La Carbonera, Yucatan, Mexico

This study reports seasonal variation, growth parameters and natural mortality for Eucinostomus gula and Eucinostomus argenteus inhabiting La Carbonera, a tropical coastal lagoon on the northwestern coast of theYucatan Peninsula, Mexico. Specimens were collected between April 2009 and March 2010. A total of 2700organisms of E. gula (&gt; 80% in rainy season ) and 1577 organisms of E. argenteus (&gt;50% in dry season)were collected during the study period. Length-weight relationship (LWR) obtained was W = 8.323E-03Lt2.92 in E. argenteus and W = 7.314E-03 Lt2.92 in E. gula. Growth parameters of von Bertalanffy growthfunction (VBGF) by length frequency analysis were in E. argenteus: L∞ = 13.65 cm, k = 0.54 year-1 and t0= - 0.37 years; and in E. gula: L∞ = 12.60 cm, k = 0.68 year-1 and t0 = - 0.28 years. Additionally, estimatednatural mortality in E. gula was 1.50 year-1 and in E. argenteus was 1.9 year-1. This study presents the firstestimation for both species of model parameters, growth performance index and mortality for the Yucatan Peninsula, which is relevant for the proper implementation of conservation measures for E. gula and E. argenteus in an important coastal zone of the Yucatan Peninsula.Se reportan la variación temporal, los parámetros de crecimiento y la mortalidad natural para Eucinostomus gula y Eucinostomus argenteus que habitan en la laguna costera tropical La Carbonera, al noroeste de la península de Yucatán, México. Los especímenes fueron recolectados entre abril de 2009 a marzo de 2010. Un total de 2 700 organismos de E. gula (&gt; 80% en la estación lluviosa) y 1 577 organismos de E. argenteus (&gt; 50% en la estación seca) fueron recolectados durante el período de estudio. Se determinó la relación peso-longitud (RPL) como: P = 8.323E-03 Lt 2.92 en E. argenteus y P = 7.314E-03 Lt2.92 en E. gula. Para E. argenteus, los parámetros de crecimiento de la ecuación de crecimiento de von Bertalanffy (ECVB) fueron: L∞ = 13.65 cm, k = 0.54 año-1 y t0 = - 0.37 años; mientras que para E. gula fueron: L∞ = 12.60 cm, k = 0.68 año-1 y t0 = - 0.28 años. La mortalidad natural en E. gula fue 1.50 año-1 y en E. argenteus fue 1.9 año-1. Este estudio presenta la primera estimación para ambas especies de los modelos de crecimiento, el índice del desempeño de crecimiento y la mortalidad natural para la península de Yucatán, lo que es relevante para la adecuada implementación de medidas de conservación de E. gula y E. argenteus en una valiosa zona costera de la península de Yucatán.

Temporal variation, growth and natural mortality of two species of mojarras (Perciformes: Gerreidae) from a tropical coastal lagoon: La Carbonera, Yucatan, Mexico

This study reports seasonal variation, growth parameters and natural mortality for Eucinostomus gula and Eucinostomus argenteus inhabiting La Carbonera, a tropical coastal lagoon on the northwestern coast of theYucatan Peninsula, Mexico. Specimens were collected between April 2009 and March 2010. A total of 2700organisms of E. gula (&gt; 80% in rainy season ) and 1577 organisms of E. argenteus (&gt;50% in dry season)were collected during the study period. Length-weight relationship (LWR) obtained was W = 8.323E-03Lt2.92 in E. argenteus and W = 7.314E-03 Lt2.92 in E. gula. Growth parameters of von Bertalanffy growthfunction (VBGF) by length frequency analysis were in E. argenteus: L∞ = 13.65 cm, k = 0.54 year-1 and t0= - 0.37 years; and in E. gula: L∞ = 12.60 cm, k = 0.68 year-1 and t0 = - 0.28 years. Additionally, estimatednatural mortality in E. gula was 1.50 year-1 and in E. argenteus was 1.9 year-1. This study presents the firstestimation for both species of model parameters, growth performance index and mortality for the Yucatan Peninsula, which is relevant for the proper implementation of conservation measures for E. gula and E. argenteus in an important coastal zone of the Yucatan Peninsula.Se reportan la variación temporal, los parámetros de crecimiento y la mortalidad natural para Eucinostomus gula y Eucinostomus argenteus que habitan en la laguna costera tropical La Carbonera, al noroeste de la península de Yucatán, México. Los especímenes fueron recolectados entre abril de 2009 a marzo de 2010. Un total de 2 700 organismos de E. gula (&gt; 80% en la estación lluviosa) y 1 577 organismos de E. argenteus (&gt; 50% en la estación seca) fueron recolectados durante el período de estudio. Se determinó la relación peso-longitud (RPL) como: P = 8.323E-03 Lt 2.92 en E. argenteus y P = 7.314E-03 Lt2.92 en E. gula. Para E. argenteus, los parámetros de crecimiento de la ecuación de crecimiento de von Bertalanffy (ECVB) fueron: L∞ = 13.65 cm, k = 0.54 año-1 y t0 = - 0.37 años; mientras que para E. gula fueron: L∞ = 12.60 cm, k = 0.68 año-1 y t0 = - 0.28 años. La mortalidad natural en E. gula fue 1.50 año-1 y en E. argenteus fue 1.9 año-1. Este estudio presenta la primera estimación para ambas especies de los modelos de crecimiento, el índice del desempeño de crecimiento y la mortalidad natural para la península de Yucatán, lo que es relevante para la adecuada implementación de medidas de conservación de E. gula y E. argenteus en una valiosa zona costera de la península de Yucatán.

Long-term vegetation changes in a tropical coastal lagoon system after interventions in the hydrological conditions

Over a period of 44 years, we observed the vegetation changes in the western part of the lagoon system of the Ciénaga Grande de Santa Marta, which is situated on the Caribbean coast of Colombia and is separated from the sea by a sandy barrier. Since the construction of the Barranquilla-Ciénaga Road between 1956 and 1960, the lagoon system has been exposed to different interventions in its hydrological make-up, as well as changes to the vegetation. During the time of our investigations, four periods with different plant cover were distinguished. In 1965, the road was bordered by dense mangrove forests. The low surface water salinity and the presence of freshwater plants indicated the influence of the Magdalena River. At the beginning of the seventies, the second period was marked by a decrease in the freshwater in-flow from the river, which led to an increase in salinity and a gradual decay of vegetation. In 1988, the areas formerly covered by mangroves had converted into salt flats. The third period began with the reconstruction of several channels (1995–1998) which renewed the freshwater in-flow from the river to the lagoons. The subsequent vegetation development was characterized by the establishment of Typha domingensis Pers. In 1999, a year with an unusually high amount of rainfall, this species covered most of the former mangrove area in the western part of the lagoon system. The very low surface water salinity favored its spread. The last period began in 2001/2002, when growth conditions for T. domingensis became unfavorable due to an increase in salinity. Instead, conditions for mangrove regeneration improved. This process was slower than expected and is still ongoing. The striking vegetation changes indicate the sensitivity of the coastal lagoon system to hydrological variability.

Length-weight relationship, parameters of growth and mortality for the hardhead halfbeak Chriodorus atherinoides Goode &amp; Bean, 1882 (Beloniformes: Hemiramphidae) from Yucatan Peninsula, Mexico

Summary This study reports length–weight relationships and growth parameters for Chriodorus atherinoides from La Carbonera, a karstic tropical coastal lagoon on the northwestern coast of the Yucatan Peninsula, Mexico. A total of 667 specimens were collected between April 2009 and March 2010. The length-weight relationship obtained was W = 0.0034Lt3.22. This study presents the first estimation of the model parameters of the von Bertalanffy growth equation (L∞ = 27.30 cm, k = 0.76 year−1 and t0 = −0.178 years), the instantaneous total mortality (2.51 year−1) and the maximum length record (26.0 cm total length), which is greater than previously recorded.

Magnitude and variability of methane production and concentration in tropical coastal lagoons sediments

AIM: Coastal wetlands are potential zones for methane (CH4) production. The present study aims to evaluate the spatial variation of CH4 production and concentration in ten tropical coastal lagoons, the influence of aquatic macrophytes on the sediment CH4 concentration and how the magnitude of these potential CH4 production rates compare to those in other ecosystems. METHODS: Sediments were sampled in ten coastal lagoons, with one site in the limnetic region and another site in aquatic macrophyte stands when they were present in the littoral region. We measured the CH4 production as a potential rate, and CH4 concentration was directly measured from sediment samples. RESULTS: The highest potential CH4 production (PMP) rates were found in alkaline and hypersaline lagoons. However, Cabiúnas, which is a freshwater lagoon densely colonized by aquatic macrophytes, also exhibited a high PMP rate. We also observed that the sediment CH4 concentration in the littoral region was higher than in the limnetic region in all of the investigated lagoons except Paulista, which presented the opposite pattern. The PMP rates observed in the studied lagoons were low compared to other aquatic ecosystems. CONCLUSION: Our results suggest that the sediments of saline lagoons are important CH4 production sites, and in general, aquatic macrophytes have a positive influence on methanogenesis, which was evident based on the CH4 concentrations present in the sediments of these lagoons. Further studies should focus on the processes underlying the CH4 patterns observed in the tropical coastal lagoons, especially concerning the coupling between CH4 production and concentration.

Effects of food web structure and resource subsidies on the patterns and mechanisms of temporal coherence in a tropical coastal lagoon: an experimental mesocosm approach

AIM: The study of the patterns and mechanisms of temporal coherence of ecological variables among lakes has become an important area of limnology. However, no study to date has experimentally tested whether and how resource subsidies and food web configuration affect the patterns and mechanisms of temporal coherence of limnological variables. We conducted a field mesocosm experiment to test the following hypotheses: (i) nutrient enrichment would reduce the temporal coherence of system variables; (ii) fish predation would enhance the temporal coherence of system variables; and (iii) the strength of temporal coherence decreases from physical (water transparency), to chemical (dissolved oxygen concentration [DO]) to biological variables (total zooplankton biomass). METHODS: For 11 weeks, we manipulated fish presence and nutrient (N and P) concentration in a 2 × 2 factorial design in sixteen within-lake enclosures installed in a tropical coastal lagoon. Coherence was estimated by pair-to-pair Pearson's moment correlations of the temporal trajectories of each response variable among enclosures of the same treatment. RESULTS: Fish presence only enhanced the temporal coherence of zooplankton biomass, whereas contrary to our expectations, nutrient addition enhanced the temporal coherence of [DO]. The strength of the individual effects of fish and nutrients on temporal coherence was affected by variable identity, but this variation did not occur in a consistent pattern across variables. However, the interactive effects of fish and nutrients on the temporal coherence of the three variables monitored were not statistically significant. CONCLUSIONS: Our results indicate that local factors, such as fish presence and nutrient availability, may affect the temporal coherence of several system variables, but these effects are better predicted by the strength of direct interactions between the local factor and the variable than by the identity of the variable itself. We conclude that eutrophication and overfishing may alter the coupling of spatial and temporal dynamics of some ecosystem variables.

The role played by aquatic macrophytes regarding CO2 balance in a tropical coastal lagoon (Cabiúnas Lagoon, Macaé, RJ)

AIM: Carbon dioxide (CO2) is an important atmospheric trace gas that is involved in both the biological carbon cycle and global warming. Inland waters - mainly lakes - contribute to C cycling and have been considered a large source of atmospheric CO2. However, scientific studies usually neglect lake morphometry and the presence of aquatic macrophytes in littoral zones, which have a great potential for CO2 absorption and for C storage. This study aimed to evaluate the importance of the littoral region on the CO2 balance in the Cabiunas Lagoon, while also considering the contribution of the limnetic region and of Typha domingensis and Eichhornia azurea, prominent species in the area. METHODS: CO2 flux was estimated by a linear integration of CO2 concentrations measured in the internal atmospheric of a single-component static closed chambers at the studied sites. The distribution of macrophyte stands throughout lagoon surface was taken into account to evaluate the effects of macrophytes on CO2 supersaturation. Other factors were also measured throughout the sampling process to evaluate their relationship with CO2 flux data by means of Akaike model selection criterion. The area covered by aquatic macrophytes at the Cabiunas lagoon was estimated by profiles and transects. RESULTS AND DISCUSSION: CO2 flux through the water surface ranged from - 7.39 to 17.56 mgCO2m - 2h - 1. An emission pattern predominated, suggesting that water columns are CO2 supersaturated at all sampling sites. Rates were similar among all the sampling sites, suggesting that aquatic macrophytes do not influence CO2 saturation in the water column at Cabiunas lagoon. On the other hand, CO2 fluxes from macrophyte tissues showed a clear assimilation pattern. Influxes were higher in T. domingensis ( - 229.1 ± 320.9 mg CO2.m - 2.h - 1) than in E. azurea stands ( - 43.8 ± 39.5 mg CO2.m - 2.h - 1). Once these macrophytes covered a considerable area of the lagoon and CO2 absorption strongly overwhelmed the emission processes, then we were able to extrapolate data from the total estimated area of the evaluated sites (75% of the Cabiunas lagoon), which resulted in a net influx of 46.6 mg CO2.m - 2.h - 1. The strong Typha domingensis contribution to CO2 absorption and other C cycling processes indicate that it is one of the most important species to Carbon cycling in the studied ecosystem. Thus, it is worth considering C cycling in lake littoral zones as a key process when estimating C balance in shallow aquatic ecosystems.

Regulation of bacterioplankton density and biomass in tropical shallow coastal lagoons

AIM: Estimating bacterioplankton density and biomass and their regulating factors is important in order to evaluate aquatic systems' carrying capacity, regarding bacterial growth and the stock of matter in the bacterial community, which can be consumed by higher trophic levels. We aim to evaluate the limnological factors which regulate - in space and time - the bacterioplankton dynamics (abundance and biomass) in five tropical coastal lagoons in the state of Rio de Janeiro, Brazil. METHOD: The current study was carried out at the following lagoons: Imboassica, Cabiúnas, Comprida, Carapebus and Garças. They differ in morphology and in their main limnological factors. The limnological variables as well as bacterioplankton abundance and biomass were monthly sampled for 14 months. Model selection analyses were performed in order to evaluate the main variables regulating the bacterioplankton's dynamics in these lagoons. RESULT: The salt concentration and the "space" factor (i.e. different lagoons) explained great part of the bacterial density and biomass variance in the studied tropical coastal lagoons. When the lagoons were analyzed separately, salinity still explained great part of the variation of bacterial density and biomass in the Imboassica and Garças lagoons. On the other hand, phosphorus concentration was the main factor explaining the variance of bacterial density and biomass in the distrophic Cabiúnas, Comprida and Carapebus lagoons. There was a strong correlation between bacterial density and biomass (r² = 0.70, p < 0.05), indicating that bacterial biomass variations are highly dependent on bacterial density variations. CONCLUSION: (i) Different limnological variables regulate the bacterial density and biomass in the studied coastal lagoons, (ii) salt and phosphorus concentrations greatly explained the variation of bacterial density and biomass in the saline and distrophic lagoons, respectively, and (iii) N-nitrate and chlorophyll-a concentrations, water color and mean depth are important factors to explain bacterial density and biomass variance in some specific lagoons.

&lt;b&gt;Effects of intensive fish-farming and domestic wastewater on the periphytic algal community in a tropical coastal lagoon (Juara, Brazil)&lt;/b&gt; - doi: 10.4025/actascibiolsci.v35i3.17094

This study aimed at evaluating the effects of the intensive fish-farming and the domestic wastewater on the structure of the phycoperiphyton community. Three experimental supports containing artificial substrate were assembled in two sampling sites: IF – region with intensive fish-farming and DW – near the domestic wastewater discharge. Samplings were carried out after the 21st, 26th and 31st day of colonization. The abiotic variables evaluated were: transparency, electrical conductivity, pH, turbidity, total suspended solids, alkalinity, dissolved oxygen, water temperature and nutrients. Phycoperiphyton was examined with regard to density, richness, abundance, dominance, diversity and eveness. Nutrients (total nitrogen, nitrate, ammonia nitrogen, orthophosphate and silicate) were different among the sampling sites. Although the total density, richness, diversity and evenness of phycoperiphyton were not affected by the different impacts, the density by class had differences between the sampling sites, with Bacillariophyceae presenting higher density at IF and Cyanophyceae and Coscinodiscophyceae at DW. Four taxa have been associated with the impact by domestic wastewater, and four, to the intensive fish-farming. The density by class of phycoperiphyton was the best attribute to evaluate the effects of human activity.

Nitrogen and phosphorus resorption efficiency, and N : P ratios in natural populations of Typha domingensis Pers. in a coastal tropical lagoon

AIM: We studied nitrogen (N) and phosphorus (P) resorption patterns in Typha domingensis Pers. in a tropical coastal lagoon during different seasons of throughout one year. METHODS: Resorption of N and P is uttered as resorption efficiency (NRE and PRE, respectively), which may be used as an indicator of a nutrient limitation. Higher resorption efficiency values might indicate limitation of a certain element for the growth of aquatic macrophytes. RESULTS: N was inferred to be less limiting than P for the growth of T. domingensis in Campelo Lagoon, since N content varied less than P content and resorption efficiency of N was lower than that of P and, concomitantly, low resorption efficiency of this element. However, T. domingensis of Campelo Lagoon frequently utilized P that was already present in its tissues, contributing to the longer residence time of this element in system. Green leaves of T. domingensis showed N : P ratio, ranging 49-96, corroborating the inference of P limitation. CONCLUSIONS: N : P ratio and resorption efficiency indicate P limitation by T. domingensis in Campelo Lagoon.

Ecosystem functioning: The basis for restoration and management of a tropical coastal lagoon, Pacific coast of Mexico

Tropical coastal lagoons (TCL) are among the most productive coastal ecosystems, and they provide a wide range of ecosystem goods and services that support productive economic activities. The objective of this paper is to present a comprehensive review of the ecosystem dynamics in Paraman Lagoon, a wave-dominated, meso-tidal coastal lagoon with an ephemeral inlet on the Pacific coast of Mexico. A conceptual model is used to describe the seasonal environmental cycle for the lagoon, which is characterized by three periods: Period 1 - disconnected from the sea, evaporation is much higher than freshwater input and salinity can exceed 75psu; Period 2 - disconnected from the sea, freshwater input is much higher than evaporation and salinity drops to as low as 5psu; and Period 3 - the inlet is open connecting the lagoon with the ocean resulting in optimal estuarine conditions and moderate salinities between 15 to 25psu. Hydrology and salinity regime in the lagoon are largely controlled by the amount of freshwater discharge that changes the spatial and temporal distribution of environmental parameters. This information is used to develop a conceptual model of the functioning of the lagoon that can be used to aid in decision-making about the restoration and management of the lagoon