Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Background. Within any given taxocenosis of benthic diatoms (BDT), the distribution of the taxa relative abundances renders them as very abundant, common, uncommon, and rare taxa. This structure is considered when estimating species diversity using Shannon’s index (H’) based on information theory. Thus, because this distribution also occurs within the taxonomic hierarchy of BDT, i.e., genera with a high number of species-infraspecies (SS) or species singletons, estimating species diversity (H’) using the genus/SS ratio instead of relative abundances, represents an alternative measure of diversity but resorting to a much smaller data matrix. Hence, the diversity index designated H’G/SS is proposed here. Objective. In this essay, we sought to gather evidence that combining information on the genus-level taxa and their included SS provides a reliable estimation of taxonomic diversity for BDT. Hence, we tested the hypothesis that the estimated H’G/SS for the floristic of BDT in a particular locality would be as high as the highest value using diatom relative abundances. Method. To test the above, floristic and species diversity (H’) data from several studies of BDT along Mexican shores were analyzed quantitatively under the premise that diversity estimates based on relative abundances of species (H’) or the H’G/SS index would be equivalent. Results. Statistical tests supported our hypothesis showing no significant differences between the original values of H’ and those using H’G/SS. Conclusions. This diversity estimation using H’G/SS for BDT represents a reliable, quicker, and more comprehensive approach and another parameter that can be used for further conservationist, ecological, and biogeographical purposes.

Background. After its transfaunation from the Atlantic Ocean has been reported, the protozoan Perkinsus marinus has expanded its list of hosts in several species of mollusks in the Pacific Ocean, both in cultivation and in wild populations. Goals. The presence of this parasite was evaluated in the horsemussel Modiolus capax, in the southwestern Gulf of California. Methods. 60 mussels were collected per annual season for one year (summer, autumn, winter 2019-spring 2020, N = 240), in the mining port of Santa Rosalía (SR), Baja California Sur, Mexico. Thioglycollate staining was used to detect presumptive hypnospores and the polymerase chain reaction (PCR) technique for its confirmation. The prevalence, parasite load and intensity of infection were obtained in each sampling. Results. Presumptive hypnospores of the parasite were detected with thioglycollate staining in almost 20% of the samples analyzed, of which only 5% were positive for confirmation with PCR. Neither the prevalence (6.66-33.33%) nor the parasite load (˂ 2.75 hypnospores/g) showed a tendency to increase with time; the intensity of infection ranged from negative to light. Salinity showed correlation with parasite load (r = 0.99, p = 0.002). Conclusions. The results suggest that M. capax in SR presented low susceptibility to the parasite, so its health is not compromised when hosting P. marinus. Although it is the first report of the protozoan in this mussel, continuous monitoring is recommended to know not only the health status of the bivalve in the region, but also of the other species of mollusks that inhabit there.

Background. A recent interest has emerged for studying benthic marine diatoms (BMD) whose environment is influenced by potentially toxic elements (PTE), mainly metals that can alter their taxocoenoses parameters and cause deformities in the diatom frustules. Objective. To explore which particular characteristics may represent a response by BMD to PTE in environments polluted by mining residues, using the typical structure of the diatom taxocoenoses as reference, i.e., floristics, species richness, and diversity and dominance, as well as frequency of deformed frustules. Methods. Rock and sediment samples were taken in May 2015 and January 2016 at Santa Rosalía, BCS, a beach contaminated by mining waste. Results. Between 1 and 7.6% of deformed valves per site were recorded. This frequency of deformed frustules suggests the impact of contamination by EPT in the area. Diversity values of H´ between 1.1 and 4.3 were recorded, which are within the typical intervals of diversity for uncontaminated sites, although EPT concentrations such as Cu 3760 mg kg-1, Zn 2294 mg kg-1, Ni 401 mg kg-1, Pb 216 mg kg-1, recorded in the area exceed the mid-range effect values, indicating that 50% of the biota present would be affected. Conclusions. The high abundance of certain diatom taxa may indicate their ability to resist or tolerate PTE, while those exhibiting deformed frustules could be considered sensitive taxa

Background. The structure of benthic diatom assemblages (BDA) is related to the type of substrate where they flourish. Goals. assess the degree of variation shown by BDA growing on live and non-living substrata from a tropical coastal lagoon (Terminos lagoon). We tested the hypothesis that substrate influence would deem significantly distinct BDA. Methods. diatom samples were collected from live and non-living substrata from four sites within Terminos lagoon, México, where physicochemical variables were also measured. Diatom taxa were identified, and their relative abundances were estimated and used to compute community parameters (species diversity, equitability, dominance), along with the indicator value (IndVal). Also, similarity between the BDA from the four sites was measured and values were then compared using ANOSIM. Results. Although the IndVal showed a clear separation based on the dominant/constant taxa, ANOSIM indicated that differences between the sites were not significant. This may be related to the characteristic patchy distribution of BDA along environmental gradients. Conclusions. in coastal ecosystems the structure of BDA could be mainly influenced by environmental variables.

Background. Chichancanab Lake is one of the most important freshwater ecosystems located in the center of Yucatan peninsula (Mexico) as it is a primary hydrological ecoregion and habitat for endemic fauna species. However, its diversity of freshwater algae is poorly known, including cyanobacteria, a group that is of interest for its potential function as an indicator. Objective. Document the diversity of the cyanobacteria present in this site. Methods. Three samplings were carried out in different seasons of the year. The collection of freshwater algae was carried out directly. The samples were analyzed by light microscopy and diagnostic characteristics were collected depending on the taxa. Species were identified with specialized literature, in some cases the nomenclature was updated, and a review of its regional diversity was carried out. Results. In this study, 29 species of cyanobacteria belonging to different orders are reported, of which Synechococcales and the families Merismopediaceae (Synechococcales) and Oscillatoriaceae (Oscillatoriales) stand out. We report 18 new records for Quintana Roo, of which 11 are for Yucatan Peninsula: Synechococcus ambiguus, Eucapsis aphanocapsoides, E. parallelepippedon, Romeria hieroglyphica, Jaaginema subtilissimum, Komvophoron minimum, Planktolyngbya limnetica, Schizothrix tenuis, Spirulina nordstedtii, Phormidium californicum y P. lucidum. The ecological conditions of the site are similar to other tropical water bodies in different Caribbean countries and share at least 31.4% of morphospecies. Conclusions. A greater diversity of cyanobacteria than previously reported in the literature was found. This work intends to lay the foundations for the knowledge of freshwater algae in the lagoon and be a reference for future taxonomic, ecological, and applied works that start from this place.

Background: In La Paz Bay macroalgae blooms have an important presence. Goal: Analyze the relationship of the most abundant macroalgae in algal blooms with environmental variability in a subtropical bay over two years. Methods: Temperature, salinity, nutrients (DIN, NT, PO4 -3 and PT) and macroalgae samples were taken every three months, during 2010 and 2011, at four sites with conspicuous growth of macroalgae. Total and mean biomass (wet weight) of important species was estimated by placing three transects perpendicular to the coast, divided into five equidistant points each. At each point four quadrants (0.25 m2 ) were placed randomly and macroalgae were manually collected. Statistical analyzes were performed to estimate significant differences between years, months and sites of the environmental variables, nutrients, and biomass. A principal component analysis was performed, to observe the relationship between biomass and environmental variables and nutrients. Results: Nine macroalgae species, plus one cyanoprokaryonte showed a biomass greater than 1 g m-2. Acanthophora spicifera, Caulerpa verticillata and Spyridia filamentosa were the most abundant species. A. spicifera and G. vermiculophylla were related with nutrient concentrations, and salinity. While Ulva ohnoi showed that it was not related either to environmental or nutrient concentrations. Conclusion: The bloom forming macroalgae A. spicifera, C. verticillata and S. filamentosa are consistent with genera previously reported as bloom-formers in nutrient-rich coastal waters.

Background. The interest in studying seaweed polysaccharides as plant growth biostimulants is recent and has generally focused on seaweed liquid extracts for compounds content that have positive effect on plant development. Within these compounds are the carbohydrates such as alginate and fucoidan, among others. Goals. To evaluate the effect of crude fucoidan and alginate on seed germination and their growth-stimulating activity on seedling of mung bean (Vigna radiata). Methods. Fucoidan and alginate from Eisenia arborea and Sargassum horridum at six different doses (0.6, 1.2, 2.5, 5, 10, and 20 mg m‒1 ) were evaluated on seed germination and seedling growth of mung bean. Results. Alginate from both algae species in this study did not show a significant effect on mung bean growth. Fucoidan from S. horridum produced the significant effect on mung bean growth by increasing root length (16.2%) and seedling total length (11.9%) at a concentration of 0.6 mg mL‒1 and an increase in the dry weight of the seedling (31%) at a concentration of 20 mg mL‒1 . While fucoidan from E. arborea had the higher effect on shoot growth (10.5%) and total length (10.7%), compared to the control when applied at a concentration of 10 mg mL‒1 . Conclusions. Overall, this study showed that fucoidan from both S. horridum and E. arborea can stimulate seedling growth and increase the germination percentage of mung bean seeds compared to the control.

Background. In Mexico, few studies have been carried out on epibiosis. Epizoic diatoms are used as biological indicators of ecosystems due to their apparent epibiont specificity with host animals. Little is known about this specificity in the planktonic larval phases. There have been no studies focused on epizoic diatoms on the marine gastropod Aliger gigas larval shells. Goals. The objective of this work was to determine the species composition of epizoic diatoms in the larvae of A. gigas in the Xel-Há cove, the Mexican Caribbean. Methods. Mollusk egg masses were collected from their natural environment, and the larvae were cultured in seawater filtered through a 5 µm mesh under controlled conditions and fed with the eustigmatophycean alga Nannochloropsis oculata (1000 cells/ml). Shell surface of 60 larvae aged between 2 and 42 days was analyzed using scanning electronic microscopy. A relative abundance index was calculated to quantify diatoms. Results. In total, 83% of the examined larvae carried diatoms. Twenty-four diatom species were found: 68% were mobile, 24% were erect sessile and 8% were adnate species. Conclusions. The highest richness and abundance of epizoic diatoms in the A. gigas larvae were observed on bigger shells due to a larger available colonization area and a more stable substrate.

Background. The macroalgae of the tropical Mexican Pacific have been studied and results published in numerous texts since the 1940s. Nevertheless, there is no compilation of records of macroalgae from reef communities, nor have specific inventories of reef macroalgae been prepared. Objective. To integrate the knowledge generated on the tropical Mexican Pacific coral reef macroalgae. Carry out an integration of the knowledge generated on reef macroalgae and make inventories of these macroalgae in the reefs of Guerrero and Oaxaca in the Mexican tropical Pacific. Methods. Sørensen›s similarity analysis and Non-Metric Multidimensional Scaling (NDMS) analysis were applied to data of algal composition from different coral reefs to determine their distribution patterns. The ANOSIM analysis method was applied to demonstrate the significant differences between groups. Results. The total number of macroalgal species was 144, 100 Rhodophyta, 32 Chlorophyta and 12 Ochrophyta-Phaeopyceae; 75 were exclusive to Guerrero, 24 to Oaxaca, and the number of shared species was 45. El Zacatoso, Guerrero, had 92 species and was the locality with the greatest specific richness. The Sørensen Index indicated a similarity of more than 50% among most localities, but with a clear separation between the communities of Guerrero and Oaxaca. Four groups were formed by localities’ species with the NMDS analysis without seasonal effect (rainy and dry), ANOSIM shows significant differences among the localities of each group. Conclusion. This work represents the first inventory of the reef-inhabiting macroalgae of Guerrero and Oaxaca, the only states in the Mexican tropical Pacific with specific systematic reports on this type of coral reef algae. This study provides baseline information to develop a regional monitoring program, a diagnosis of the degree of disturbance of coral reefs and generate conservation strategies and plans for these ecosystems.