Particular structure of an epiphytic diatom assemblage living on Ploclamium cartilagineum (Lamoroux) Dixon (Rhodophyceae: Gigartinales).

Abstract

This is the first record of an epiphytic diatom assemblage of Ploclamium cartilagineum. Fifteen years ago observations on a specimen of P. cartilagineum revealed that large diatom of certain taxa occurred abundantly on its branches, and suggested also that it may harbor a particular diatom assemblage. Thus, we set out objective into identifying all the diatom taxa in the assemblage represented on the same P. cartilagineum specimen, and to determine their proportional abundances. Overall 46 taxa of epiphytic diatoms were identified. The diatom assemblage was characterized by abundant large forms such as Gephyria media, and Hyalodiscus punctatus a new record for the region, and the small form Cocconeis californica. Also include is, Grammatophora macilenta a new record for the region. Hitherto rare taxa in the region were very common such as Rhabdonema adriaticum, Campylopyxys garkeana, and Melosira polaris/Melosira sol. Although the estimated species richness and diversity values are high as in other assemblages of benthic diatoms, its basic structure (floristics) in which large forms rival the smaller forms in number, makes this assemblage particular. Estructura particular de una asociación de diatomeas epifitas sobre Ploclamium cartilagineum (Lamoroux) Dixon (Rhodophyceae: Gigartinales) Se presenta el primer registro de diatomeas epifitas de Ploclamium cartilagineum. Hace quince años se observó que sobre las ramas de un espécimen de P. cartilagineum habitaban abundantes taxa de diatomeas de gran tamaño, lo que sugirió que hospedaba una asociación particular de diatomeas. Bajo el objetivo de identificar todos los taxa representados de diatomeas en el mismo espécimen y determinar sus abundancias proporcionales en la asociación, se identificaron 46 taxa, de las cuales dos formas grandes resultaron abundantes: Gephyria media, y Hyalodiscus punctatus un nuevo registro para la región; así como Cocconeis californica, una forma pequeña. Asimismo, se agregó un nuevo registro para la región con Grammatophora macilenta. Varios taxa considerados raros hasta antes de este estudio fueron muy comunes, como Rhabdonema adriaticum, Campylopyxys garkeana, y Melosira polaris/Melosira sol, entre otros. Aunque la riqueza y diversidad de especies fueron elevadas (típicas) como en otros hábitats bentónicos, su estructura básica (florística) en donde formas grandes son tan abundantes como las pequeñas define una asociación particular.

Uncommon species diversity values in epiphytic diatom assemblages of the kelp Eisenia arborea

“…The observed species richness was approximately half of what has been recorded in similar floristic studies for either a single or for multiple macroalgae species (Siqueiros Beltrones, 2002;Siqueiros Beltrones and Hernández Almeida, 2006;Argumedo Hernández and Siqueiros Beltrones, 2008). In contrast, the floristic study mentioned earlier of a single specimen of P. cartilagineum showed it to be heavily epiphytized by many of the 42 taxa recorded, and coupled to a much higher value of diversity (H´= 3.52), a low dominance and a high equitability, indicating that the environment provided by the host is very favorable (Siqueiros Beltrones and Argumedo Hernández, 2014a). Meanwhile, the low values of diversity observed for the diatom assemblages on E. arborea blades resemble those observed in diatom assemblages from extreme environments (Siqueiros Beltrones, 2002).…”

“…In fact, much of the interest in the study of M. pyrifera focuses on its role as food for abalone. As with other macroalgae, epiphytic diatoms are considered to be enriching their food value (Siqueiros Beltrones and Argumedo Hernández, 2005;Siqueiros Beltrones and Argumedo Hernández, 2014a), inasmuch as many epiphytic diatoms have been observed within the gut contents of juveniles and adults of abalone collected in the wild (Siqueiros Beltrones, 2002;. Thus our intention to determine what diatom taxa would be found on other macroalgae, such as E. arborea, which represents the ecological alternative for M. pyrifera in the region.…”

“…However, a high number of diatom taxa has also been recorded living on a single species of macroalgae, such as in the giant kelp Macrocystis pyrifera L. (C. Agardh) where the number of diatom species surpassed 170 taxa for several sampling dates (Siqueiros Beltrones et al, 2002;Siqueiros Beltrones and Argumedo-Hernández, 2005;Argumedo-Hernández and Siqueiros Beltrones, 2008). Moreover, in a recent study where a single specimen of the rhodophyte Ploclamiun cartilagineum (Lamoroux) Dixon was examined, as many as 42 diatom taxa were recorded (Siqueiros Beltrones and Argumedo-Hernández, 2014a).…”