Organic carbon sources and their transfer in a gulf of Mexico coral reef ecosystem

Coral reefs face unprecedented threats throughout most of their range. Poorly planned coastal development has contributed increased nutrients and sewage contamination to coastal waters, smothering some corals and contributing to overgrowth by macroalgae. My approach to assessing the degree to which coral reef ecosystems have been influenced by terrestrial and anthropogenic organic carbon inputs is through the use of carbon (C) and nitrogen (N) stable isotopes and lipid biomarkers in a marine protected area, the Coral Reef System of Veracruz: Parque Nacional Sistema Arrecifal Veracruzano (PNSAV) in the southwest Gulf of Mexico. Firstly, I used a C and N stable isotope mixing model and a calculated fatty acid (FA) retention factor to reveal the primary producer sources that fuel the coral reef food web. Secondly, I used lipid classes, FA and sterol biomarkers to determine production of terrestrial and marine biogenic material of nutritional quality to pelagic and benthic organisms. Finally, I used coprostanol to determine pollutant loading from sewage in the suspended particulate matter. Results indicate that phytoplankton is the major source of essential metabolite FA for marine fish and that dietary energy from terrestrial sources such as mangroves are transferred to juvenile fish, while seagrass non-essential FA are transferred to the entire food web mainly in the rainy season. Sea urchins may be the main consumers of brown macroalgae, especially in the dry season, while surgeon fish prefer red algae in both dry and rainy seasons. C and N isotopic values and the ratio C:N suggest that fertilizer is the principal source of nitrogen to macroalgae. Thus nitrogen supply also favored phytoplankton and seagrass growth leading to a better nutritional condition and high retention of organic carbon in the food web members during the rainy season when river influence increases. However, the great star coral Montastrea cavernosa nutritional condition decreased significantly in the rainy season. The nearest river to the PNSAV was polluted in the dry season; however, a dilution effect was detected in the rainy season, when some coral reefs were contaminated. In 2013, a new treatment plant started working in the area. I would suggest monitoring δ¹⁵N and the C: N ratio in macroalgae as indicators of the nitrogen input and coprostanol as an indicator of human feces pollution in order to verify the efficiency of the new treatment plant as part of the management program of the PNSAV

Composición química y precursores de ácidos vaccénico y ruménico en especies forrajeras en Baja California Sur, México

Los rumiantes pequeños que pastorean la vegetación nativa seleccionan su dieta a partir de una amplia variedad de especies vegetales, que difieren en su contenido y disponibilidad de nutrientes durante el año, y son fuente importante de nutrientes. El objetivo del estudio fue determinar y comparar la composición bioquímica de especies forrajeras asociadas al agostadero de Baja California Sur. Las especies evaluadas fueron huizache, mezquite, palo fierro, palo verde y vinorama, así como alfalfa henificada. Se cuantificó el contenido de materia seca, proteína cruda, lípidos totales, fibra cruda, cenizas, extracto libre de nitrógeno y energía bruta, así como la concentración de ácido linoléico, ácido A-linolénico y ácidos grasos poliinsaturados ARA, EPA y DHA. Los resultados muestran que el palo verde y el mezquite presentaron un contenido mayor de proteína cruda. El huizache mostró la concentración mayor de lípidostotales, seguido de palo verde y mezquite. Huizache y alfalfa henificada presentaron las concentraciones mayores de ácido linoleico; mientras que palo verde alcanzó los niveles más altos de ácido alfa linolénico, seguido por palo fierro y alfalfa henificada. Palo verde, palo fierro y alfalfa henificada obtuvieron concentraciones mayores de ácidos grasos poliinsaturados. El uso de los forrajes de agostadero en la alimentación de los rumiantes es una alternativa que podrá modificar las proporciones de los ácidos grasos de la leche dado el contenido del ácido oleico, linoléico y linolénico, precursores del ácido vaccénico y ruménico y ácidos grasos poliinsaturados de la serie omega 3 como el EPA y el DHA

Evaluation of growth, cell size and biomass of Isochrysis aff. galbana (T-ISO) with two LED regimes

In contrast to crops, there are fewer studies using LED-based light with green microalgae and none cultivating the microalga Isochrysis aff. galbana (T-ISO) even though of its importance in marine aquaculture. The objective was to evaluate of white and red LEDs as an alternative source of light to cultivate I. aff. galbana (T-ISO). In order to carry this out white and red LEDs were used with a laboratory built Erlenmeyer-type photobioreactor to determine productivity, cell number and size and biomass composition. Results were compared with standard fluorescent lights of the same light intensity. The culture system consisted of 3 flasks for applying red LEDs and three for white LEDs and 3 control group flasks illuminated with the normal fluorescent lighting at the similar light intensity of ~60 mM m–2 s–1. It was found that the population cell density did not significantly increase with either red LEDs or white LEDs (p > 0.05), if at all. Standard fluorescent lighting (control group) showed significant increases in population cell number (p < 0.05). Through microscopic observation cell size was found to be smaller for white LEDS and even smaller for red LEDs compared to fluorescent lighting. Biochemical composition of proteins, carbohydrates and lipids was similar for all light regimes. The authors suggest that the unexpected non-growth I. aff. galbana (T-ISO), a haptophyte microalga, with white and red LEDs is possibly due to fact that to initiate cell growth this microalgae requires other wavelengths (possibly green) besides red and blue, to allow other pigments, probably fucoxanthin, to capture ligh

Effects of the "EL Niño" event on the recruitment of benthic invertebrates in Bahía Tortugas, Baja California Sur

Se realizó una evaluación de los efectos del Niño (1997-98) sobre el reclutamiento de invertebrados bentónicos y macroalgas en dos arrecifes rocosos de Bahía Tortugas, en la costa del Pacífico central de la península de Baja California. Para cuantificar el impacto de este evento, se midieron los cambios en densidad ocurridos en juveniles de abulón (Haliotis fulgens y H. corrugata), de macroalgas laminariales (Macrocystis pyrifera y Eisenia arborea), y en el asentamiento de postlarvas puerulus de langosta (Panulirus interruptus), antes, durante y después de El Niño. El efecto del Niño tuvo un impacto diferente para cada especie: los bancos de sargazo fueron eliminados desde principios del otoño de 1997, recuperándose parcialmente un año después, y completamente hacia el invierno de 1999. La densidad de los juveniles de abulón de 1 año de edad mostró una drástica reducción en otoño de 1997, pero fue recuperándose lentamente de 1998 a 1999. Durante este último período, el grupo de 1 año de edad mostró una alta variación en su longitud de concha, lo cual sugiere un efecto indirecto de El Niño al alterar la base alimentaria de los juveniles de abulón. Por el contrario, la densidad en los asentamientos de puerulus y juveniles de langosta se estimuló positivamente durante El Niño, observándose los máximos asentamientos coincidentes con las máximas anomalías de temperatura y nivel medio del mar. Se concluye que la comunidad bentónica de esta región costera muestra una gran resistencia al cambio y que sus poblaciones están adaptadas para recobrar su condición normal uno y medio o dos años después de ocurrido el evento. doi: https://doi.org/10.22201/igeof.00167169p.2003.42.3.92

Effect of diatom and dinoflagellate diets on egg production and ingestion rate of Centropages furcatus (Copepoda: Calanoida) from subtropical bay (Bahía de la Paz, Gulf of California)

This study experimentally determined the role of local diatom and dinoflagellate diets and their fatty acid composition on the survival, in gestion, and egg production rates of the copepod Centropages furcatus from Bahía de La Paz. The fatty acid profiles of the diatoms Odontella longicruris and Chaetoceros sp., and of the dinoflagellates Scripp siella sp., Gyrod nium sp., and Prorocentrum m cans were deterined. After in cubating at 24 °C in darkness during 24 h, survival within all phytoplankton diets was &gt; 90%. Dinoflagellate diets providedhig her egg production (&gt;25 eggs fe ma le-1 day-1) than diatom diets (&lt;10 eggs female-1 day-1). No significant differences were observed in the in gestion rates when feddinoflagellates or diatoms, which varied between 400 and 900 ng C copepod-1 h-1. Hig her egg production with dinoflagella te diets suggests better food quality, which may be attributed to hig her proportions of the fatty acids 18:4 (n-3) and 22:6 (n-3). These results suggest that when C. fulcatus predominantly graze on dinoflagellates egg production will increase. Hig her abundances of dinoflagellatesin the La Paz bay could be cou pled with hig her egg production of the copepod C. furcatus