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

Abstract

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.

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

“…Few studies have been conducted on the planktonic communities of Campeche Canyon. Hernández-Becerril et al (2008) observed a predominance of the coccolithophore Emiliania huxleyi and the diatom Nitzschia bifurcata. In summer, most of the zooplankton biomass occurs below the thermocline, in the upper 60 m layer (Mojica-Ramírez 2003).…”

“…Existen pocos estudios concernientes a las comunidades planctónicas sobre el Cañón de Campeche. Hernández-Becerril et al (2008) encontraron una predominancia del cocolitofórido Emiliania huxleyi y de la diatomea Nitzschia bifurcata. En verano la mayor cantidad de biomasa zooplanctónica se encuentra debajo de la termoclina, en la capa superior de 60 m de profundidad (Mojica-Ramírez 2003), mientras que en invierno, durante la temporada de tormentas invernales localmente conocidas como "Nortes", las comunidades de zooplancton estuvieron dominadas por copépodos y la mayor abundancia de zooplancton se encuentra en torno a la termoclina, esto como resultado del incremento del espesor de la capa de mezcla (Ramírez-Cruz 2005).…”

Spatial distribution of living coccolithophores in the southwestern Gulf of Mexico

“…Studies from the southern and southwestern GoM have also been conducted on various ecological aspects of phytoplankton and primary productivity (e.g. Okolodkov, 2003;Hernández-Becerril et al, 2008). Many of these studies have traditionally considered the microplankton fraction, especially large diatoms and dinoflagellates, as the main contributors to primary production (e.g.…”

“…Many of these studies have traditionally considered the microplankton fraction, especially large diatoms and dinoflagellates, as the main contributors to primary production (e.g. Hernández-Becerril & Flores, 1998;Licea et al 2004, Hernández-Becerril et al, 2008.…”

“…Furthermore, coccolithophores were also found to play an important role in the structure of the phytoplankton communities in the southern GoM (Bay of Campeche). The highest phytoplankton abundance was dominated mainly by the species E. huxleyi and G. oceanica and was associated with a thermal front in the coastal shelf zone (Hernández-Becerril et al, 2008).…”