The marine planktonic diatom Rhizosolenia robusta (Bacillariophyta): morphological studies support its transfer to a new genus, Calyptrella gen. nov.

The marine planktonic diatom Rhizosolenia robusta Norman is widely distributed in tropical and subtropical areas and occurs occasionally in more temperate ones. Traditionally it has been considered a species of the genus Rhizosolenia, but its taxonomic status has not been reviewed. The present study is based on light and electron microscopy of net plankton samples front several tropical and Subtropical locations. including Pacific and Atlantic coasts of Mexico and the Indian Ocean. Features unique for this species include Undulated and ribbed valves, the Structure Of the valve wall, the morphology of the process at the apex of each valve, the location and shape of the labiate structure, and the arrangement of the girdle hands. These features Support transfer to a new genus Calyptrella gen. nov. its Calyptrella robusta (Norman) Hernández-Becerril et Meave. Morphological variability includes Shape Of file cell and length of the external tube. The term 'calyptra' is reintroduced for it structure analogous to the process of Rhizosolenia sensu stricto. The morphology of the complex labiate structure-external tube is discussed, and the term 'conflatuportula' (United rimoportula) is proposed for this Structure. Further studies are necessary to decide whether Rhizosolenia firma Karsten belonggs to the new genus

Morphological study of the marine planktonic diatom Chaetoceros castracanei Karsten (Bacillariophyceae) from Antarctic waters, with a discussion on its possible taxonomic relationships

Phytoplankton samples were collected along the north coast of the Antarctic peninsula, the Weddell Sea and the Gerlache Strait, in different seasons in 1985, 1986, 1999, and 2000-2002. Chaetoceros castracanei Karsten, a fairly rare species was present in the sample

Occurrence of a subsurface anticyclonic eddy, fronts, and Trichodesmium spp.

Eddies and fronts created by geostrophic balance between counter-rotating currents are hydrodynamic processes that concentrate or dilute plankton and suspended material by physical processes of accumulation, retention, or dispersion. Over Campeche Canyon, in the southern Gulf of Mexico, observations revealed an anticyclonic eddy, a cyclonic current off the continental shelf, and an associated thermal front in their common boundary. Along this front there was high Trichodesmium spp. occurrence. Three water masses were found in the upper 120 m layer: Caribbean Tropical Surface Water (CTSW), Caribbean Subtropical Underwater (CSUW), and Gulf Common Water (GCW). The frontal zone between the warm core and cyclonic circulation was observed below the hot summertime mixed layer. The presence of Trichodesmium spp. was associated with the front, indicating its influence on the distribution of this diazotrophic cyanobacterium that enters the Campeche Canyon region via modified CTSW. The associated phytoplankton was dominated by tropical oceanic species of diatoms and dinoflagellates, especially species of Ceratium.

Marine planktonic dinoflagellates of the order dinophysiales (Dinophyta) from coasts of the tropical Mexican Pacific, including two new species of the genus Amphisolenia

Despite a recent revision of the dinoflagellates of the order Dinophysiales on Mexican coasts and a checklist of dinoflagellates from the Mexican Pacific, many records still need to be confirmed, for there are very few reliable illustrations and/or descriptions. In this paper, species composition and distribution of dinoflagellates belonging to the Dinophysiales, the product of the analysis of net phytoplankton material collected from coasts of the tropical Mexican Pacific (Jalisco to Chiapas) are presented. The material has been studied using light microscopy, although a few species were also studied by scanning electron microscopy (SEM). Forty-one species from five genera were identified, with two new records annotated for the Mexican Pacific: Amphisolenia thrinax and Metaphalacroma skogsbergii, and two new species of the genus Amphisolenia, Amphisolenia fusiformis sp. nov. and Amphisolenia michoacana sp. nov. Illustrations, dimensions and distribution data are provided for each species, and descriptions of the new species are also given. Amphisolenia palmata, A. rectangulata, A. truncata, Dinophysis apicata, D. hindmarchii, Histioneis biremis, H. crateriformis, H. pulchra, Ornithocercus cristatus, O. heteroporoides and O. orbiculatus arc illustrated for thefirst time in the waters of the Mexican Pacific. The number of species found in this study is relatively low. The species Dinophysis norvegica and D. sacculus, reported in previous papers, do not seem to occur in Mexican waters, as their distribution is rather limited to the Mediterranean Sea and the North Atlantic, respectively. Finally, the identity of certain species of Dinophysis and the nature of the new species described here are discussed

Nanoplankton fraction in the phytoplankton structure in the southern Gulf of Mexico (April 2000)

Phytoplankton, especially the nanoplankton fraction, and its possible relationships with the hydrographic conditions in the southern Gulf of Mexico were studied during an oceanographic cruise in April 2000. Hydrographic data and phytoplankton were analyzed. Phytoplankton species composition showed heterogeneity among stations. A total of 180 species were found: 114 diatoms, 32 dinoflagellates, 32 coccolithophores, and 2 silicoflagellates. Diversity indices were variable (0.96–5.12 bits ind–1). Phytoplankton was numerically dominated by coccolithophores or nanoplanktonic diatoms. Cell abundance was low to moderately high, ranging from 5.3 × 103 to 1.4 × 105 cells L–1. The most abundant, dominant species were nanoplanktonic forms: two coccolithophores, Emiliania huxleyi and Gephyrocapsa oceanica; the pennate diatoms Nitzschia bicapitata, N. bifurcata and N. leehyi; and centric diatoms of the genus Thalassiosira. The high subsurface abundance of coccolithophores at two stations was related to a thermal front in the Grijalva-Usumacinta river system.

Toxic and harmful marine phytoplankton and microalgae (HABs) in Mexican Coasts

Harmful Algal Blooms (HABs) are becoming an increasing problem to human health and environment (including effects on natural and cultured resources, tourism and ecosystems) all over the world. In Mexico a number of human fatalities and important economic losses have occurred in the last 30 years because of these events. There are about 70 species of planktonic and non-planktonic microalgae considered harmful in Mexican coasts. The most important toxin-producing species are the dinoflagellates Gymnodinium catenatuni and Pyrodinium bahamense var. compressum, in the Mexican Pacific, and Karenia brevis in the Gulf of Mexico, and consequently the poisonings documented in Mexico are Paralytic Shellfish Poisoning (PSP) and Neurotoxic Shellfish Poisoning (NSP). Although there is evidence that Amnesic Shellfish Poisoning (ASP), Diarrhetic Shellfish Poisoning (DSP) and Ciguatera Fish Poisoning (CFP) also occur in Mexico, these problems are reported less frequently. The type of phytoplankton and epiphytic microalgae, their toxins and harmful effects as well as current methodology used to study these phenomena are presented in this paper. As an experienced group of workers, we include descriptions of monitoring and mitigation programs, our proposals for collaborative projects and perspectives on future research