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Species of the dinoflagellate genus Alexandrium are marine and planktonic forms, widely distributed, and some are recognized to form harmful algal blooms and to produce saxitoxins causing Paralytic Shellfish Poisoning in humans, and other toxins. We studied the species composition of Alexandrium in tropical and subtropical coastal areas of the Mexican Pacific: from the southern Gulf of California to the Gulf of Tehuantepec. Eleven Alexandrium species were identified, described, and illustrated using light microscopy, and occasionally scanning electron microscopy for certain species. Additionally, the genetic characterization of seven strains and four species, was performed, using sequences of the D1/D2 LSU rDNA and ITS regions. We identified the species (morphospecies): Alexandrium affine, A. gaarderae, A. globosum, A. leei, A. margalefii, A. minutum, A. monilatum, A. pseudogonyaulax, A. tamarense, A. tamiyavanichii, and A. tropicale. Of these, A. affine, A. leei, A. minutum, A. monilatum, A. pseudogonyaulax, A. tamarense and A. tamiyavanichii have been widely recognized as harmful algae. Alexandrium gaarderae, A. globosum and A. tropicale are new records for the Mexican Pacific. This is the first morphological documentation of A. pseudogonyaulax. Future studies of the genus might increase its species richness if more cultures are established and metabarcoding approach is used. [ABSTRACT FROM AUTHOR]

The major histocompatibility complex (MHC) enables vertebrates to cope with pathogens and maintain healthy populations, thus making it a unique set of loci for addressing ecology and evolutionary biology questions. The aim of our study was to examine the variability of Heermann's Gull MHC class II (MHCIIB) and compare these loci with other Charadriiformes. Fifty-nine MHCIIB haplotypes were recovered from sixty-eight Heermann's Gulls by cloning, of them, twelve were identified as putative true alleles, forty-five as unique alleles, and two as pseudogenes. Intra and interspecific relationships indicated at least two loci in Heermann's Gull MHCIIB and trans-species polymorphism among Charadriiformes (coinciding with the documented evidence of two ancient avian MHCIIB lineages, except in the Charadriidae family). Additionally, sites under diversifying selection revealed a better match with peptide-binding sites inferred in birds than those described in humans. Despite the negative anthropogenic activity reported on Isla Rasa, Heermann's Gull showed MHCIIB variability consistent with population expansion, possibly due to a sudden growth following conservation efforts. Duplication must play an essential role in shaping Charadriiformes MHCIIB variability, buffering selective pressures through balancing selection. These findings suggest that MHC copy number and protected islands can contribute to seabird conservation. [ABSTRACT FROM AUTHOR]

An Alexandrium affine strain (AAJQ-1) from San José Island, Gulf of California was characterized for growth and toxicology. Fivefold of f/2 + Se cultures were incubated for 34 days in a temperature gradient (21–29 °C). Aliquots were collected every third day for cell counting, toxin determination, and nutrient analyses. In this study ELISA method was used to evaluate the PSP toxin production due to the lower detection limit than the HPLC method. The highest cell density (6724 cells mL−1) and growth rate (0.22 day−1) were obtained at 27 °C and they were related to temperature in all treatments. Cell density showed negative correlation with nitrate at temperatures ≥23 °C, and with orthophosphate 27 °C, furthermore, these correlations promote the toxin production (0.05–0.45 fmol STX cell−1); beyond that nitrite at high temperature seems to promote toxin production, which has not been sufficiently documented. [Display omitted] • Low growth rates for an A. affine strain isolated from the Mexican Pacific Ocean. • Highest population growth was promoted at warm temperatures (≥25 °C). • Very low ELISA PSP toxin detection from 0.05 to 0.45 fmol PSP cell−1. • Maximum PSP toxin production occurs in the stationary phase at 21 °C. • Negative correlation between nitrate and temperatures above 23 °C. [ABSTRACT FROM AUTHOR]

Population genetic structure can aide in developing conservation and management strategies by characterizing populations on local and regional scales. The Elegant Tern (Thalasseus elegans) has a restricted breeding range, with a majority of its nesting population historically found on Isla Rasa, Gulf of California, Mexico. Since the late 1950s, increased frequency of low marine productivity due to warm oceanographic anomalies, such as El Niño events, have caused northward expansion of Elegant Tern breeding colonies into southern California, USA. To test the hypothesis that high gene flow occurs between Gulf of California and southern California Elegant Tern breeding colonies, restriction-site associated DNA sequencing was used to analyze 5,510 single nucleotide polymorphisms from 69 Elegant Terns sampled across four known breeding sites: Isla Rasa, Mexico (n = 30), San Diego National Wildlife Refuge, USA (n = 17), Bolsa Chica Ecological Reserve, USA (n = 11), and Port of Los Angeles, USA (n = 11). Analyses revealed little population subdivision, with non-significant genetic differentiation (FST) among sites and no geographic association of individuals, but there was subtle clustering of individuals by breeding site. These results suggest a strong degree of gene flow among the Gulf of California and southern California nesting colonies and indicate that Elegant Terns have a fluid breeding distribution and move readily among nesting sites. [ABSTRACT FROM AUTHOR]

Alexandrium tamiyavanichii is a marine dinoflagellate known to produce Paralytic Shellfish Poisoning (PSP) toxin. Thus, a strain was isolated from La Paz Bay, Baja California Sur, Mexico and used to explore whether stress conditions, such as phosphorus limitation (PL) and nitrogen enrichment (NE) modulate population growth and PSP toxin production in the GSe medium. Growth kinetics showed that the PL treatment produced a 3.4-fold increase in cell density versus control at day 30 of the culture cycle. The highest PSP concentration was found in the control culture (309 fmol cell−1) on day 21. Saxitoxin (STX) was the main analog in all the treatments (> 40 % mol). In conclusion, PL and NE treatments promoted growth kinetics in the species studied but did not affect the PSP toxin production. For the first time, the present research describes A. tamiyavanichii high toxicity strain isolated from Mexican coasts relative to the South-Atlantic strains. [Display omitted] • First report of PSP toxins from an A. tamiyavanichii strain in the Gulf of California. • Phosphorus limitation promoted the growth in this A. tamiyavanichii strain at 24 °C. • Nitrogen enrichment and phosphorus limitation did not promoted toxin production. • Highest PSP toxin concentration was found in GSe medium as the control condition. [ABSTRACT FROM AUTHOR]

Ocean warming events are becoming more frequent, with potential consequences for birds that use marine resources. We analyzed the annual population growth of Heermann's Gulls (Larus heermanni) through matrix-based demographic models under normal and high sea surface temperature (SST) conditions. Under stable, normal conditions, predicted population growth was ∼4%, with survival of fledglings and juveniles contributing to population growth. Under high SST conditions, predicted population growth dropped to −15% and adult survival became the key factor determining species fitness. Simulations showed a declining growth rate as the frequency of warm SST anomalies increased. Heermann's Gulls can resist oceanographic anomalies of up to 1 event every 5 yr without seriously compromising their population growth rate or their individual fitness, but populations may decline rapidly if the frequency of warm-phase anomalies continues to increase, as it has done during the last decade. [ABSTRACT FROM AUTHOR]

Coastal lagoons are subject to anthropogenic sources of pollution that contribute to the deterioration of water quality and eventually to accelerating the natural eutrophication processes. The purpose of this research was to identify the spatial distribution and seasonal variation of the trophic state of the Bahía Santa María-La Reforma lagoon system and drains during four seasons, in relation to the discharge of effluents into the lagoon from the economic activities carried out by the population. Surface water samples were collected and temperature, salinity, dissolved oxygen, chlorophyll a and nutrients concentration were measured and analysed to estimate the trophic index for the lagoon system. The trophic state in the mouths and within the lagoon system gradually changes from hypereutrophic conditions in the dry season, to mesotrophic during the rainy season with intermediate conditions during the transition seasons. However, the drains maintain hypereutrophic conditions regardless of the seasonal variation. The discharge of nutrients from economic activities such as agriculture and aquaculture, modify the trophic state in Bahía Santa María-La Reforma lagoon system, whereby some factors, including geomorphology, the presence of two mouths that connect with the sea and the tides, determine its hydrodynamics. [Display omitted] • A seasonal transition of TRIX was observed at the sampling stations within the SMLRB lagoon system. • The trophic state in dry season was hypertrophic while in the rainy season it was mesotrophic. • The rainy season and the rainy-dry transition showed the highest variability in all variables. • Drains with hypertrophic condition that did not show seasonal variation. • The factors that predict the trophic state in SMLRB are nutrients, chlorophyll α , and salinity. [ABSTRACT FROM AUTHOR]

The article offers information on the marine species condition at Upper Gulf of California. Topics discussed include concern for extinction of vaquita porpoise, most endangered marine mammal of Mexico; reduction of freshwater flow into the Upper Gulf of California (UGC) due to damming and diversion of the Colorado River, cause decline in vaquita; and collaborative efforts required among fishermen, the seafood supply chain, and environmental and fisheries agencies for conservative solution.

The highly productive Gulf of California exhibits high biodiversity and an abundance of small pelagic, schooling fishes, important both to the ecosystem and to fisheries. These fishes show wide fluctuations in abundance due to oceanographic–atmospheric phenomena such as El Niño-Southern Oscillation, constituting a problem for effective fisheries management. In this work we propose several parameters in the diet of three seabird species as useful predictors of the eventual commercial catch per unit effort (CPUE) of Pacific sardine ( Sardinops sagax ) and northern anchovy ( Engraulis mordax ) in the Midriff Island Region of the Gulf of California. We found that seabirds are sensitive to fluctuations in the abundances of these fishes, their proportions in the diet becoming suitable predictors of future commercial CPUE. The precision of our prediction is high because the birds feed on pre-recruit fish, and the time between the sampling of the diets and the initiation of the fishing season is short, minimizing stochastic effects on recruitment and subsequent abundance due to environmental fluctuations. [ABSTRACT FROM AUTHOR]

Isla Rasa in the Gulf of California has been recognized as an important seabird breeding island for more than 150 y. Yet during most of this period, the island suffered human disturbances that severely reduced seabird nesting success. Today, nearly two decades after disturbances ended, Isla Rasa supports about 90% of the global populations of Heermann's gulls ( Larus heermanni) and elegant terns ( Thalasseus elegans), plus smaller populations of other species. However, the recently available 1856 journals of Italian naturalist Federico Craveri, and the oral traditions of the Comcaac (Seri people), suggest that the array of nesting species has changed. Apparently, California brown pelicans ( Pelecanus occidentalis californicus) abandoned Isla Rasa as a breeding site at the onset of disturbances, and terns first colonized it around 1920. [ABSTRACT FROM AUTHOR]

The article offers a comparison of presumed Elegant and Cabot's Tern hybrids' external characteristics with those of their presumed parental species. The very high proportion of hybridization of North American and European tern species is discussed wherein 44 percent have been reported to hybridize compared with the 10 percent of all bird species. A table shows the anatomical characteristics of 15 presumed Thalasseus (T.) elegans and T. acuflavida hybrids on Isla Rasa, Gulf of California, Mexico. The possible contribution of Cabot's and Elegant Tern on the hybrids' characteristics such as bill length, bill depth, and leg color are estimated.