The geographical distribution of the green benthic seaweeds from the Mexican coasts of the Gulf of Mexico and the Caribbean Sea was analyzed by means of a data bank that includes 98 taxonomic publications that appeared in the 1846 - 2000 period, based on Jaccard’s index. In total, 169 species with 49 genera were recorded, with the highest species richness corresponding to Cladophora (26 species) and Caulerpa (16). Over 70.8% of all the phycoflora was confirmed based on 69 species collected by the authors in 25 localities (40.8%), and 30% through consultation of the MEXU, ENCB and DUKE herbaria. The phycological classification scheme of marine environments included 17 habitats in five coastal types where algae develop on different substrates: hard (62.5%), soft (48.4%), animal (36.8%), plant (30%), floating (11%), and artificial (12.2%). The distinction between two provinces along the Mexican coasts of the Atlantic Ocean Basin was confirmed: one corresponding to a rich tropical phycoflora along the southern coast, from Quintana Roo to Veracruz (Caribbean Province), and the other extending along the subtropical waters and being poor in species (Carolinean Province). Cabo Rojo is the boundary between the tropical and the subtropical coasts of Mexico.

Halymenia floresii is an edible species consumed in some Asian markets. In the Yucatan peninsula coast of Mexico, H. floresii dominates rocky substrata between 3 and 40 m where it grows up to 50 cm high. After analyzing the seasonal pattern of pigment content on H. floresii, we evaluate if and how the spectral composition of light affects growth and pigment dynamics under laboratory cultivation. Unialgal cultures were exposed to white, blue, red and green light in a 3-week experiment. Green light resulted in the highest algal growth rates. Synthesis of chlorophyll a, α-carotene and lutein, but not of β-carotene, was induced by white or green light. Phycocyanin synthesis was stimulated by blue light and phycoerythrin synthesis by blue or red light. Light quality treatments may be used to manipulate pigment composition in Halymenia floresii cultures.

The Veracruz Reef System National Park (PNSAV) is located in the central region of Veracruz, off the coast of the municipalities of Veracruz, Boca del Río and Antón Lizardo. It is a complex and important system within the Gulf of Mexico, since it has been declared a biosphere reserve by UNESCO, a Ramsar wetland and an essential component of the southwestern Gulf of Mexico Reef Corridor. Lobophora contains 28 currently recognized species and has a pantropical distribution that includes the Atlantic, Pacific, and Indian Oceans in both hemispheres. Recently, some species have been identified from Western Atlantic Ocean, mainly in the Caribbean Sea. However, very little is known about Lobophora species diversity on the Mexican coast. In this study, morphological and molecular analyses (MAAT) using cytochrome c oxidase 3 (COX3) sequences as a barcode gene were used to study Lobophora spp. The results indicate that there are two species on the Mexican coasts, Lobophora declerckii and L. variegata. Lobophora declerckii represents a new record for the southwest of the Gulf of Mexico and, the presence of L. variegata was confirmed for the Mexican Caribbean.

Resumen. El fitoplancton de aguas continentales esta representado por 15 000 especies en el mundo. En México se registraron 1 025 especies, casi el 6.8% de las algas continentales a nivel mundial y el 33.8% de las algas continentales de México. Estuvo representado principalmente por las clases Bacillariophyceae (31.9%), Cyanophyceae (18.24%) y Chlorophyceae (17.4%). La mayoría de las especies son cosmopolitas, otras tienen afinidades tropicales y neárticas. Las regiones central y S-SE son las mejor representadas (> 100), no así la región N-NE con pocos taxa (< 2). Ocho estados del norte y 4 del S-SE permanecen sin estudios o registros. En México el descubrimiento de nuevas especies fue realizado por europeos y americanos, los científicos mexicanos comenzaron a describir especies en 1933, pero es hasta finales del siglo XX y principios del XXI que se describen un mayor número. La falta del conocimiento de las algas fitoplanctónicas de México, el bajo nivel de endemismo y la perturbación de los ambientes acuáticos ponen en riesgo la sobrevivencia de esta importante comunidad. Diversas especies fitoplanctónicas han sido utilizadas como suplementos alimenticios, antioxidantes, o para bio-remediación y biocombustibles; sin embargo, su producción en México es aún muy limitada.

New records of subtidal benthic marine algae from the State of Veracruz, the southern Gulf of Mexico, are presented, which include 7 species and 2 forms. The material was collected from 6 sampling forays at 4 locations between October 2013 and September 2017. The collection sites included the "Ana Elena" and "Riva Palacio" shipwrecks and some poorly explored reefs in the State of Veracruz, Mexico. The morphological characteristics of Hypoglossum simulans, Halymenia hancockii, Dictyota humifusa, Caulerpa sertularioides f. longiseta, Avrainvillea levis f. translucens, Udotea caribaea, U. dixonii, U. unistratea, and Anadyomene saldanhae are described. Information about the habitats and geographic distributions of these taxa is provided.