Celestun Lagoon Research Articles

Relationship of litterfall anomalies with climatic anomalies in a mangrove swamp of the Yucatan Peninsula, Mexico.

Among the set of phenological traits featuring mangrove ecosystems, litterfall production stands out with marked intra-annual and longer-term variation. Furthermore, mangrove forests resilience is one of the most important ecological attribute, reconciling the juxtaposed terrestrial and marine environment such transitional systems occupy. However, world's mangroves are nowadays facing recurrent climatic events, reflected in anomalies depicted by major drivers, including temperature and precipitation. This physical-environmental setting may either constrain or favor overall forest productivity. A combination of time series analysis (spectral density and cross-correlation techniques) and statistical model fitting (General additive model) was implemented to explore trends in total litterfall of a well-developed mangrove forest in southeastern Gulf of Mexico (Celestun Lagoon, SE Mexico) and potential association with the varying behavior of temperature (°C) and precipitation (mm month-1), highlighting their anomalies. The results are consistent with a synchronous response between litterfall production and climatic variables (mean monthly temperature and total monthly precipitation). Concurrent peak litterfall production in Celestun lagoon with high temperatures and precipitation occurred during June and October, featuring a two-month time lag for the response time. More than half of the litterfall anomalies (53.5%) could be reflecting either multiple sources of climatic anomalies (maximum, minimum, and monthly average temperature and monthly total precipitation) or single point events (cyclone landfall). This relationship dynamics showed an interannual persistence (1999-2010). The structure portrayed by the litterfall time-series was not unequivocally related to climatic anomalies. Arguably, climatic anomalies behave with different intensities and even may exhibit complex interactions among them. The study of anomalies provides a baseline for a better grasp of: i) mangrove anomalies responses and ii) their vulnerability to these extremes.

Spatial-temporal Variations of Discarded Ichthyofauna from a Small-scale Shrimp Fishery: Influence of Ecological Patterns in a Yucatan Coastal Lagoon

Sauz-Sánchez, J.J.; López-Rocha, J.A.; Arceo-Carranza, D., and Poot-López, G.R., 2022. Spatial-temporal variations of discarded ichthyofauna from a small-scale shrimp fishery: Influence of ecological patterns in a Yucatan coastal lagoon. Journal of Coastal Research, 38(4), 860–869. Coconut Creek (Florida), ISSN 0749-0208. Spatial-temporal variations of discarded catches associated with a shrimp-small scale fishery from the Celestun lagoon, Yucatan, Mexico, were analyzed throughout seasonal and spatial (inner, middle, and external estuarine zones) physicochemical gradients to observe the influence of ecological patterns on discarded ichthyofauna. Differences in abundance, biomass, composition, and physicochemical variables between seasons and among zones were tested using a two-way ANOVA and an analysis of dissimilarity, respectively. The best subset of environmental variables (BIOENV) function was used to observe the influence of physicochemical gradients on the discarded fish community. A total of 1611 individuals belonging to 36 species of discarded fish were identified, with mostly an abundance of juveniles occurring for the following species: Achirus lineatus, Archosargus probatocephalus, Cynoscion nebulosus, Eucinostomus gula, Floridichthys polyommus, Lagodon rhomboides, Lucania parva, Mayaheros urophthalmus, and Sphoeroides testudineus. Hence, the data shows a strong selection pressure on juvenile fish. Significant differences in abundance, species composition, and physicochemical variables were observed between seasons and zones. Results from the BIOENV indicated that temperature, salinity, and pH gradients, generated by underground freshwater discharges, influenced the spatial-temporal variations of discarded ichthyofauna from the Celestun lagoon. Furthermore, reproductive seasons, and capabilities to tolerate salinity concentrations also spatially structures a discarded fish community. The results showed the ecological complexity in which fish discards occur, in addition, suggesting measures to reduce discards by including ecological and social aspects to maintain the sustainability of this artisanal shrimp fishery.

Sedimentation as a Support Ecosystem Service in Different Ecological Types of Mangroves

Mangrove vegetation is strongly dependent on the climate, the physicochemical variables of the sediment, and the hydrological dynamics. These drivers regulate the distribution of different mangrove ecotypes and their ecosystem services, so the net sediment accumulation rates in different mangrove ecotypes in Celestun Lagoon, a karstic zone in the NW Yucatan Peninsula, SE Mexico, were estimated. The measurements considering mangrove ecotypes and their spatial variability concerning the lagoon's salinity gradient (inner, middle, and outer lagoon zones) in three climate seasons (dry, rain, and “nortes”) were realized. We registered the structural variables of the forest, interstitial water physicochemical characteristics, and sediment variables that could influence the net sediment deposition. Fringe mangroves are exposed to low hydrodynamism and show the highest sedimentation rate (3.37 ± 0.49 kg m−2 year−1) compared to basin (1.68 ± 0.22 kg m−2 year−1), dwarf (1.27 ± 0.27 kg m−2 year−1), and “peten” (0.52 ± 0.12 kg m−2 year−1) mangroves. The highest sedimentation rate was recorded in the rainy season (0.24 ± 0.08 kg m−2 month−1), while spatially, the highest value was registered in the outer zone (0.44 ± 0.09 kg m−2 month−1). If the extension of each mangrove ecotype is considered, dwarf mangroves have the highest annual sediment accumulation (1,465 t year−1 in 14,706 ha). The structural, physicochemical, and sediment variables of the sites by mangrove ecotype show that dwarf mangroves represent a distinct group from those formed by fringe, basin, and peten mangroves. However, the sedimentation is high in fringe mangroves at the front of the lagoon and diminishes inland where peten mangroves exist. The differences are given by tree density, but salinity, as a proxy variable of the freshwater influence, significantly influences the sedimentation rate. These results indicate that mangroves in karstic environments can have critical roles in confronting climate change, considering water and sediment flows are the basis of sediment accumulation. According to their hydrogeomorphological drivers, conserving, managing, and restoring the mosaic of mangrove ecotypes improves ecosystem services, including mitigation and adaptation to climate change.

Late Holocene environmental change in Celestun Lagoon, Yucatan, Mexico

Epikarst estuary response to hydroclimate change remains poorly understood, despite the well-studied link between climate and karst groundwater aquifers. The influence of sea-level rise and coastal geomorphic change on these estuaries obscures climate signals, thus requiring careful development of paleoenvironmental histories to interpret the paleoclimate archives. We used foraminifera assemblages, carbon stable isotope ratios (δ13C) and carbon:nitrogen (C:N) mass ratios of organic matter in sediment cores to infer environmental changes over the past 5300 years in Celestun Lagoon, Yucatan, Mexico. Specimens (> 125 µm) from modern core top sediments revealed three assemblages: (1) a brackish mangrove assemblage of agglutinated Miliammina and Ammotium taxa and hyaline Haynesina (2) an inner-shelf marine assemblage of Bolivina, Hanzawaia, and Rosalina, and (3) a brackish assemblage dominated by Ammonia and Elphidium. Assemblages changed along the lagoon channel in response to changes in salinity and vegetation, i.e. seagrass and mangrove. In addition to these three foraminifera assemblages, lagoon sediments deposited since 5300 cal yr BP are comprised of two more assemblages, defined by Archaias and Laevipeneroplis, which indicate marine Thalassia seagrasses, and Trichohyalus, which indicates restricted inland mangrove ponds. Our data suggest that Celestun Lagoon displayed four phases of development: (1) an inland mangrove pond (5300 BP) (2) a shallow unprotected coastline with marine seagrass and barrier island initiation (4900 BP) (3) a protected brackish lagoon (3000 BP), and (4) a protected lagoon surrounded by mangroves (1700 BP). Stratigraphic (temporal) changes in core assemblages resemble spatial differences in communities across the modern lagoon, from the southern marine sector to the northern brackish region. Similar temporal patterns have been reported from other Yucatan Peninsula lagoons and from cenotes (Nichupte, Aktun Ha), suggesting a regional coastal response to sea level rise and climate change, including geomorphic controls (longshore drift) on lagoon salinity, as observed today. Holocene barrier island development progressively protected the northwest Yucatan Peninsula coastline, reducing mixing between seawater and rain-fed submarine groundwater discharge. Superimposed on this geomorphic signal, assemblage changes that are observed reflect the most severe regional wet and dry climate episodes, which coincide with paleoclimate records from lowland lake archives (Chichancanab, Salpeten). Our results emphasize the need to consider coastal geomorphic evolution when using epikarst estuary and lagoon sediment archives for paleoclimate reconstruction and provide evidence of hydroclimate changes on the Yucatan Peninsula.

An abnormal rostrum in a wild subadult shrimp Farfantepenaeus duorarum (Burkenroad, 1939) (Decapoda, Penaeidae) from the southern Gulf of Mexico

Abstract An abnormal bifid rostrum is reported for the first time for a wild-caught subadult female (carapace length = 22.5 mm) of the pink shrimp Farfantepenaeus duorarum (Burkenroad, 1939) from Celestun lagoon, Yucatan, southern Gulf of Mexico. A review of registers on morphological abnormalities in shrimps of the family Penaeidae is provided.

Sea level rise sedimentary record and organic carbon fluxes in a low-lying tropical coastal ecosystem

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±0.1mmyr−1 in ≈1941 to 2.9±1.2mmyr−1 in 2012. These accretion rates were similar to eustatic sea level rise, and mean acceleration ranged from 0.037–0.22mmyr−2, implying a SLR by 2100 ranging from 14 to 86cm. The one-century (1917–2013) organic carbon stock in sediments was calculated to be 10.1±0.2MgCha−1. During the same period, the organic carbon flux, corrected for organic carbon degradation, increased from 7±3gCm−2yr−1 to 73±26gCm−2yr−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.

Partitioning the relative contributions of organic matter and mineral sediment to accretion rates in carbonate platform mangrove soils

In coming decades, the global rate of sea-level rise (SLR) is projected to accelerate beyond rates observed over the past several millennia when mangrove wetlands have expanded in tropical, sub-tropical and temperate regions. There is substantial uncertainty about how distinct mangrove ecotypes inhabiting a wide range of geomorphic settings will respond to SLR acceleration, including the thresholds at which they will submerge permanently. In this study, the relative contributions of soil organic and inorganic matter (SOM and SIM) to 210Pb-derived accretion rates were examined at 23 mangrove sites in southwest Florida, USA and the Yucatan Peninsula in Mexico. These sites are situated atop carbonate platforms where there is wide variation in the availability of SIM (generally marine marl). To account for this variability, research sites were classified by SIM presence based on the SOM content (%) estimated using loss-on-ignition: organic sites (SOM>70%), intermediate sites (SOM=40–70%) and mineral sites (SOM<40%).SOM accumulation rates were largely the same in the three soil classes during the past century (p<0.05); however, SIM accumulation rates in the intermediate and mineral sites were approximately 5 and 20 times greater, respectively, than rates in the organic sites. Despite this substantial difference in total mass accumulation rates, accretion rates were not statistically different between soil classes (p<0.05). Our analysis revealed that the rate of SOM accumulation is the best predictor of accretion rates, while the rate of SIM accumulation primarily predicts soil dry bulk density. These findings indicate that SOM and SIM do not contribute additively to soil volume. This is contrary to findings from North American coastal wetlands broadly, suggesting a unique characteristic of carbonate platform mangrove soils that lack a regular, substantive supply of terrigenous SIM.Overall, accretion rates in the FL sites and a Yucatan site on the Caribbean Sea are maintaining pace with regional rates of SLR over the past 100-year and 50-year timespans, whereas the sites in Celestun Lagoon, MX (located on the Gulf of Mexico) exhibit an accretion deficit. Estimates of regional SLR rates range from 4.6 to 12.2mmyr−1 by the year 2060. Based on accretion rates observed in the past century, some of these sites may be able to keep pace with the lower SLR estimate, but there is no evidence that any of these sites can match the higher rate.

Diversity of Vibrio spp in Karstic Coastal Marshes in the Yucatan Peninsula.

Coastal bodies of water formed by the combination of seawater, underground rivers and rainwater comprise the systems with the greatest solar energy flow and biomass production on the planet. These characteristics make them reservoirs for a large number species, mainly microorganisms. Bacteria of the genus Vibrio are natural inhabitants of these environments and their presence is determined by variations in the nutrient, temperature and salinity cycles generated by the seasonal hydrologic behavior of these lagoon systems. This study determined the diversity of the genus Vibrio in 4 coastal bodies of water on the Yucatan Peninsula (Celestun Lagoon, Chelem Lagoon, Rosada Lagoon and Sabancuy Estuary). Using the molecular technique of 454 pyrosequencing, DNA extracted from water samples was analyzed and 32,807 reads were obtained belonging to over 20 culturable species of the genus Vibrio and related genera. OTU (operational taxonomic unit) richness and Chao2 and Shannon Weaver diversity indices were obtained with the database from this technique. Physicochemical and environmental parameters were determined and correlated with Vibrio diversity measured in OTUs.

Hydrologic Dynamics of a Subtropical Estuary Using Geochemical Tracers, Celestún, Yucatan, Mexico

Oxygen isotopes and strontium concentrations were used as geochemical tracers to discern the sources of water to Celestun Lagoon, a small subtropical estuary on the western side of the Yucatan Peninsula of Mexico. Celestun Lagoon is underlain by karstified limestone with numerous locations where groundwater is observed discharging directly to the lagoon. In this study, samples of groundwater, lagoon surface water, and seawater (SW) were collected in April 2008 and June 2009 and analyzed for salinity, stable isotopes of oxygen, and strontium (Sr2+) concentrations. These geochemical tracers were used in two tertiary mixing models to calculate the relative ratio inputs of fresh groundwater, brackish groundwater, and SW to the lagoon. Two sources of groundwater were found to contribute to the surface water in the lagoon; one fresh and the other brackish with an average salinity of 19 psu. The fresh groundwater had an oxygen isotopic signature (δ18O) and strontium concentration (Sr2+) of δ18O = -3.30‰ and Sr2+ = 0.03 mmol/l, respectively. The brackish groundwater observed in the northern end of the lagoon add a dissimilar oxygen isotopic signature and Sr2+ concentration of δ18O = 3.01‰ and Sr2+ = 0.12 mmol/l, respectively. Local SW had an isotopic oxygen signature and Sr2+ concentration between the two fresher sources (δ18O = 1.40‰, Sr2+ = 0.09 mmol/l). The lagoonwide results of the two tracer mixing models (δ18O and Sr2+) agreed well (within 5 %) and indicated a ratio of brackish groundwater–fresh groundwater– SW of 31 %–26 %–43 % (±5 %) for the Sr2+ model and 35 %–25 %–40 % (± 5 %) for the δ18O model. Brackish groundwater is dominant in the northern portion of the lagoon, while SW dominates the southern portion. Fresh groundwater discharge is a significant contributor of water along the entire eastern boundary of the lagoon where mangrove forests are the dominant vegetation.

Thermohaline processes in a tropical coastal zone

The detailed thermohaline structure of the northern Yucatan coastal zone was obtained for the first time in order to gain an insight into the interactions between various processes in this complex tropical environment of extreme evaporation and high precipitation rates. From the continent, it has water exchange with numerous coastal lagoons (ranging from brackish to hypersaline) and receives intense submarine groundwater discharges (SGD). In the summer of 2006 a high-resolution (500m cross-shore and 5km along-shore) oceanographic campaign was performed starting at Holbox Island down to the mouth of Celestun Lagoon. CTD profiles were measured at 1020 stations along 69 coastal cross-shore transects. Additionally, CTD data from 2 wider surveys, covering the continental shelf (Campeche Bank) and the southern Gulf of Mexico respectively were used to complement the results. From the thermohaline properties, two main water masses were identified: (a) the Caribbean Subtropical Underwater (CSUW), upwelled from the Caribbean, which was observed at the bottom very close to the coast in more than 260km (from the upwelling region near Cape Catoche to approximately 89.5 W during the summer of 2006) and (b) the second dominant group was a mass of warm hypersaline water which originates in Yucatan due to the high temperature and evaporation rates. We call this water mass the Yucatan Sea Water (YSW) after finding evidence of its presence in various field campaigns both in the Yucatan Sea and further to the west in the southern Gulf of Mexico. All the water masses present in the Yucatan coastal zone showed pronounced variations with important dilution and salinisation effects. The permeable karstic geology of the region prevents the continental water from discharging into the ocean through surface rivers and instead the rainfall permeates directly to the aquifer and travels through caves and fractures towards the sea. Three main regions showed evidence of continental discharges from the coast: the central eastern region (~21.6 N, 87.75 W), around Dzilam Bravo (~21.4 N, 89 W) and, to a lesser degree, the western region of the coast (~21.1 N, 90.3 W). The latter two regions are the eastern and western intersections of the Chicxulub crater ring with the coast respectively.

Day and night trophic variations of dominant fish species in a lagoon influenced by freshwater seeps

The aim of this study was to determine the trophic structure and nycthemeral variations in the diet of dominant fish species (Ariopsis felis, Bairdiella chrysoura, Micropogonias undulatus, Eucinostomus gula, Eucinostomus argenteus, Lagodon rhomboides and Sphoeroides testudineus) in Celestun Lagoon, a biosphere reserve located in the southern Gulf of Mexico, and influenced by freshwater seeps. A total of 1473 stomachs were analysed and nine trophic groups were recorded. Bray-Curtis analyses with analyses of similarity (ANOSIM) statistical tests were used to determine two groups of feeding guilds: zoobenthivores and omnivores, with significant differences between time and habitat. The relationships between fish feeding habits, size class and environmental variables were investigated using canonical correspondence analysis (CCA). Most of the species showed a low niche breadth with high specialization towards amphipod consumption, with the exception of L. rhomboides (0·60), which indicated generalist feeding. This study in a protected area is an important source of information for drawing up conservation policies in relation to the management of aquatic resources, and will aid in the establishment of priority areas for conservation.

Spatial structuring of submerged aquatic vegetation in an estuarine habitat of the Gulf of Mexico

Seasonal changes in spatial structure of biomass of submerged aquatic vegetation (SAV) and environmental variables were evaluated in Celestun Lagoon, an estuarine habitat in Mexico. Geostatistical techniques were used to evaluate spatial autocorrelation and to predict the spatial distribution by kriging. The relative contribution of 11 environmental variables in explaining the spatial structure of biomass of SAV was evaluated by canonical correspondence analysis. Spatial partitioning between species of SAV was evident: the seagrasses Halodule wrightii and Ruppia maritima dominated the seaward and central zones of the lagoon, respectively, whereas the green alga Chara fibrosa was constrained to the inner zone. The spatial structure and seasonal variability of SAV biomass were best explained by organic carbon in the sediments, salinity and total suspended solids in the water column. Analysis at different spatial scales allowed identifying the importance of spatial structure in biotic and abiotic variables of this estuarine habitat.

Length-weight relationships for selected fish species from a coastal lagoon influenced by freshwater seeps: Yucatan peninsula, Mexico

Summary The present work analyzes the relationship between length and weight for 28 fish species belonging to 16 families in Celestun lagoon, a natural marine reserve located in southeast Mexico that is influenced by freshwater seeps. With interrupted periods, a total of 14 846 specimens were collected from 1990 to 2006. The most abundant species were Eucinostomus argenteus, Eucinostomus gula, Anchoa mitchilli and Lagodon rhomboides. Exponents varied around b = 3.17 at P < 0.001, indicating a preference for isometric relationships. This study presents the first estimation of LWR for four species (Menidia colei, Lucania parva, Floridichthys polyommus, Garmanella pulchra) and the maximum length record for F. polyommus (19.5 cm standard length) that is greater than previously recorded.

Influencia del hábitat en las asociaciones nictimerales de peces en una laguna costera tropical

The abundance and turnover of fish species inhabiting Celestun lagoon were evaluated according to daynight cycles, as well as habitat type. Bimonthly sampling was done at 4 sites of the lagoon, 2 at the mouth and 2 at the inner zone. The sites for each zone include bottoms with and without submerged aquatic vegetation (VAS, FSV). At each site hydrologic parameters were registered to determine their relationship with fish community structure. Fish specimens were collected using a beach seine (15 ×1.5 m, 2.5cm mesh) at day (10:00-13:00), twilight (18:00-21:00) and night (02:00-05:00). Multivariate non-parametric (NPMANOVA, NMDS, betadisper) statistics were used for the analysis. Difference in fish species were found between habitats with VAS and FSV (F=2.6108, p=0.0114). The betadisper test indicated that species rate of replacement is low between habitats and during day-night cycles. Fish assemblages between habitats are more dynamic than day-night cycles, due to seagrass meadows that host great numbers of species providing protection and food availability.

Discards from the artisanal shrimp fishery in a tropical coastal lagoon of Mexico: spatio‐temporal patterns and fishing gear effects

Abstract Variability in community (richness, diversity and evenness) and population (size structure) attributes of discards was evaluated in a shrimp fishery in Celestun Lagoon, Mexico, in different climatic seasons and hydrological zones. Sampling was conducted using two bottom nets with different mesh size codends: 1.3 cm (used in the fishery) and 2.5 cm. Although the shrimp:discard ratio was 1:1 in both cases, total biomass and abundance with the 1.3‐cm mesh size were, respectively, 4.6 and 1.8 times higher than with the 2.5‐cm mesh size. This result was consistent in time and space. Discards were dominated by fishes [60% in 1.3‐cm mesh size and 96% in 2.5‐cm mesh size, mainly Cichlasoma urophthalmus (Günther), Eucinostomus gula (Quoy &amp; Gaimard) and Lucania parva (Baird &amp; Girard)] and shellfishes (40% in 1.3‐cm mesh size and 4% in 2.5‐cm mesh size, mainly Palaemonetes spp. and Callinectes spp.). The highest discards were registered the nortes season with both mesh sizes. The 1.3‐cm mesh size retained significantly smaller sizes than the 2.5‐cm mesh size in six of the eight most important species. An increase in mesh size, together with a fishery closure during the nortes season, are suggested to mitigate the impact of the fishery on the discarded fauna.

Assessing patterns of ichthyofauna discarded by an artisanal shrimp fishery through selectivity experiments in a coastal lagoon

We evaluated spatio-temporal effects of fishing gear selectivity on the ichthyofauna discarded by the artisanal shrimp fishery in Celestun Lagoon (Mexico). Selectivity experiments, based on the covered codend method, were carried out in different zones (seaward, middle, inner) and climatic seasons (Nortes, Dry, Rainy) using two bottom nets with different mesh size codends: 13 mm (MS13: currently used in the fishery) and 25 mm (MS25). The number of fish species retained with MS13 was higher than with MS25, and the abundance, biomass and proportion retained of fish discards were significantly higher with MS13 for all seasons and zones. Additionally, community indices (species richness, diversity and evenness) calculated for the ichthyofauna retained by the MS13 codend were significantly the highest. The length of 50% retention was at least 2 times larger with MS25 than with MS13 for the 5 most abundant fish species in the catches. We conclude that an increase in mesh size would reduce substantially the impact on the ichthyofauna discarded by the artisanal shrimp fishery in this coastal lagoon.

Temporal trends in benthic macrofauna composition in response to seasonal variation in a tropical coastal lagoon, Celestun, Gulf of Mexico

Aquatic habitats in some tropical coastal environments can change seasonally, causing changes in the community structure of the benthic macrofauna. A tropical coastal lagoon, the Celestun lagoon, on the north-west Yucatan peninsula, was sampled seasonally and faunal, water and sediment data were compared with conditions during the 1994–1995 weather cycle across a grid of 12 sites distributed along the lagoon’s salinity gradient. Habitat variation was expressed as physical factors associated with the water column (e.g. salinity) and bottom sediments (e.g. interstitial salinity, texture), whereas the benthic community response was assessed through changes in species composition, diversity and dominance. Taxonomic dominance varied according to changes in seasonal habitat characteristics. During the season of strong northerly winds (‘nortes’), molluscs dominated and polychaetes almost disappeared. Polychaetes then recovered during the dry season, becoming as common as crustaceans and molluscs. Finally, during the rainy season, polychaetes became the dominant group and molluscs declined. A conceptual model summarising the community structure changes associated with key physical and biotic factors is proposed. The results indicate that the benthic community of the Celestun lagoon is a resilient one, largely driven by natural weather variability in this tropical ecosystem to a greater extent than previously suggested.

Benthic community response to habitat variation: A case of study from a natural protected area, the Celestun coastal lagoon

Little information currently exists on spatial and temporal benthic community variations in tropical coastal lagoons. Here, the benthic community response to habitat variation in the Celestun coastal lagoon, northwest Yucatan peninsula, was seasonally examined during the 1994–1995 climatic cycle into a grid of 12 sampling sites distributed along the salinity gradient of the lagoon. Habitat variation was assessed through physical factors associated both to the water column (e.g. salinity) and the bottom sediment (e.g. sand, silt and clay fractions). The benthic community response was assessed through species diversity measures and abundance. Under the influence of climatic seasonality, variations in habitat conditions followed by changes in the benthic community characteristics were expected. Results from two-way ANOVAs showed that for the period of study, Celestun lagoon was more heterogeneous along the spatial axis of variability than along the temporal one. Multiple regression analysis showed that salinity was spatially the main factor influencing the benthic community characteristics. Temporally, the sediment characteristics were observed to exert significant effects on the species diversity characteristics but not on abundance. Other variables assessed (dissolved oxygen, pH, temperature and water column transparency) exhibited no significant covariance with species diversity and abundance. Since generated from historical data, these results have the potential to be useful as a benchmark to the establishment of monitoring programs in the light of the increasing anthropogenic pressure on the natural resources of the lagoon and surrounding coastal area.

Effects of a fishing gear on an artisanal multispecific penaeid fishery in a coastal lagoon of Mexico: mesh size, selectivity and management implications

Abstract The spatiotemporal effects of a bottom net used in an artisanal multispecific penaeid fishery at Celestun Lagoon, Mexico, were evaluated. Selectivity experiments, based on the covered codend method, were carried out with two bottom nets operating simultaneously but using different mesh size codends: 13 mm (MS13: currently used in the fishery) and 25 mm (MS25). Length at 50% retention, L50, was twice as high with MS25 (15.34 mm carapace length, CL) than with MS13 (6.95 mm CL); this global pattern was recurrent for all species, seasons and hydrological zones. These differences in selectivity determined that MS13 mainly retained recruits and juveniles, whereas MS25 mainly retained sub‐adults. However, smaller shrimps were caught by both mesh sizes during the ‘nortes’ season (November to February) and at the outer zones of the lagoon. Thus, an increase in mesh size from 13 to 25 mm, together with fishery closures within specific area–season windows, is suggested to reduce risks of overfishing of these shrimp populations.

Growth and mortality of transient shrimp populations (Farfantepenaeus spp.) in a coastal lagoon of Mexico: role of the environment and density-dependence

Abstract The influence of environmental (temperature, salinity, aquatic vegetation) and density-dependent (abundance of recruits) factors on growth and mortality of four Farfantepenaeus species were evaluated during their period of estuarine residence, through a 2-year field study at Celestun lagoon, Mexico. Growth rates of the three most abundant species (F. brasiliensis, F. duorarum, F. notialis) were positively related with temperature and aquatic vegetation biomass, whereas some significant relationships between environmental factors and mortality rates were also demonstrated. Our results suggest that density-dependent processes regulate growth and mortality in these shrimp populations. Density-dependent mortality was also suggested by a strong compensatory relationship between recruits and juveniles. We conclude that population dynamics of Farfantepenaeus shrimps during their estuarine phase seem to be driven by the combined forces of density-dependent and environmental factors operating together.