Mass spectroscopy reveals compositional differences in copepodamides from limnic and marine copepods.

Marine copepods, the most abundant animals in the global ocean, imprint their surrounding waters with chemical cues, called copepodamides. Copepodamides induce defensive traits such as toxin production, bioluminescence, and colony size plasticity in a variety of marine phytoplankton. The role of copepodamides in freshwater ecosystems is, however, unknown. Here we report the consistent presence of copepodamides in copepods from six Swedish freshwater lakes. Copepodamide concentrations in freshwater copepods are similar to those of marine copepods, around 0.1 ppt of dry mass in millimetre sized individuals. The composition substantially overlaps with marine copepodamides but is also distinctly different. Marine copepods commonly contain both subgroups of copepodamides, the copepodamides (CA) and the dihydro-copepodamides (dhCA), whereas freshwater copepods are dominated by the dhCAs. Taxonomic groups had consistent copepodamide profiles across sampling sites and timepoints, supporting the presence of species-specific copepodamide signatures. We describe 10 new copepodamide structures, four of which were found exclusively in freshwater copepods. The presence of copepodamides in limnic copepods also warrants studies into their potential function as predator alarm cues in freshwater systems.

Composition, abundance and distribution of macrozooplankton in Culebra Bay, Gulf of Papagayo, Pacific coast of Costa Rica and its value as bioindicator of pollution

La abundancia, distribución y composición del macrozooplancton fue estudiada en bahía Culebra Costa Rica (10º 38’ N and 85º 40’ W) en cuatro estaciones durante la época seca (Febrero-Mayo) y lluviosa (Setiembre – Noviembre) del año 2000. Las muestras fueron colectadas en intervalos de dos semanas usando una red de 500µm de poro y 0.50-m de diámetro. Copépodos (23-31%) y ostrácodos (20-34%) fueron predominantes através del año, seguidos por los cladóceros (2.5-14%), zoea (6.6-9.5%), y sifonóforos (2.5-7.2%). Altas densidades de zooplancton fueron obtenidas en Febrero y Marzo, con un pico el 18 de Marzo. Las más bajas densidades fueron observadas el 3 de Septiembre y 5 de Noviembre. Se observaron diferencias significativas en las abundancias en cada estación para los copépodos de la especie Acartia tonsa, los grupos Ctenophora, medusae, Ostracoda, zoea y Amphipoda. Comparando las estaciones seca y lluviosa, significativamente más altas densidades fueron obtenidas en todas las estaciones en la época seca; durante la época lluviosa los ostrácodos dominaron las áreas externas. La abundancia y distribución del macrozooplancton son influenciadas por el afloramiento, el cual ocurre durante la época seca en Bahía Culebra

The abundance, distribution and composition of the macrozooplankton of Culebra Bay, Costa Rica (10º 38’ N - 85º 40’ W) were studied at four stations throughout the dry (February - May) and rainy (September - November) seasons of 2000. The samples were collected at two-week intervals using a 500µm mesh net with a 0.5 m diameter opening. Copepods (23-31%) and ostracods (20-34%) were predominant throughout the year, followed by cladocerans (2.5-14%), zoea (6.6-9.5%), and siphonophores (2.5-7.2%). High densities of zooplankton were obtained in February and March with peak abundance on March 18. The lowest densities were observed on September 3 and November 5. Significant differences in abundances at each station were observed for the groups Acartia tonsa (Copepoda), Ctenophora, Medusae, Ostracoda, Zoea, and Amphipoda. Comparison of the dry and rainy seasons revealed significantly higher zooplankton abundance in the dry season and copepod domination of all stations; during the rainy season ostracods dominated the off-shore areas. Zooplankton abundance and distribution are influenced by upwelling, which occurs during the dry season in Culebra Bay