Siphonophores off a riverine system in the southern Gulf of Mexico: factors affecting their distribution and spatial niche breadth and overlap

Abstract

Environmental factors determining the spatial pattern of the whole siphonophore community, as well as the hydrological occurrence ranges, small-scale vertical distribution, and spatial niche breadth and overlap of 23 siphonophore species collected off a riverine system in the southern Gulf of Mexico were analysed. A total of 149 zooplankton samples were collected in different strata of the water column (from 0 to 100 m) over a grid of 23 oceanographic stations during low (April) and high (October) rainy periods. Temperature and salinity measurements were taken with a CTD probe. Considering both seasons, salinity fluctuated between 30.7 and 37.0, and temperature between 18.2 and 29.0°C. Under these conditions, the hydrological occurrence ranges of species were analysed. Data on siphonophore biovolumes in the upper 30-m layer were subjected to a regression tree (RT) analysis taking the zooplankton biomass, the distance to the shore, the temperature, and the salinity as predictable variables. Results of the RT analysis showed that the distance from the shore, food availability, and temperature were among the most important factors affecting siphonophore spatial distribution. Food availability had a positive influence on the siphonophores distribution, whereas temperatures higher than 28.1°C seemed to depress most siphonophore populations. Diphyes dispar moderately dominated the community and represented 30% of the total biovolume. The calycophorans Abylopsis tetragona, A. eschscholtzi, Diphyes bojani, and Chelophyes appendiculata were the most generalist species as revealed by their niche breadth values, and Enneagonum hyalinum endured the widest salinity conditions (30.7-37.0) and was mainly distributed in coastal waters. The second most abundant species, the physonect Agalma okeni, exhibited a low mean niche overlap value with the calycophoran species. We hypothesise that differences in diet composition between physonects and calycophorans are the main cause of those low niche overlap values.

Hydrographic Processes Driven by Seasonal Monsoon System Affect Siphonophore Assemblages in Tropical-Subtropical Waters (Western North Pacific Ocean)

“…The high abundance of these dominant species is in agreement with reports from several adjacent areas, including the western waters of the TS [60], the ECS [18], and the Yangtze River Estuary and its adjacent waters [61]. Dominance of these species also was reported from other tropic-subtropical regions such as the Bay of Villefranche (northwestern Mediterranean) [27], [63], the east coast of South Africa [64], and the Gulf of Mexico [26], [30].…”

Environmental forcing on jellyfish communities in a small temperate estuary

“…They are widespread in the oceans and the majority of the species are mainly referred as truly oceanic (Pugh, 1999), however, its presence has already been detected also in coastal, bays and estuarine waters (e.g. Byrne, 1995;Molinero et al, 2005;Sanvicente-Añorve et al, 2009).…”

“…A number of environmental cues have been linked to the release of medusae by benthic life-history stages of cnidarians however, temperature has the greatest support in the literature (e.g. Carré and Carré, 1990;Ballard and Myers, 2000;Sanvicente-Añorve et al, 2009). According to Brodeur et al (1999), an increase in food or temperature could enable greater spring survival of young medusa, faster individual growth rates and overall jellyfish biomass.…”

Siphonophores from surface waters of the Colombian Pacific Ocean

“…In the Pacific Ocean, there are many studies on the composition and distribution of siphonophores in temperate waters (Palma, 1973; 1999; Pagès et al , 1990; Gasca & Suárez, 1992a, b; Palma & Rosales, 1995; Gasca, 2002; Palma & Apablaza, 2004; Palma & Silva, 2004; Apablaza & Palma, 2006; Palma et al , 2007; Sanvicente-Añorve et al , 2007, 2009; Lo et al , 2012; 2013, 2014; Gamero-Mora et al , 2015), but comparatively few from equatorial and tropical waters. Bigelow (1911) identified 40 siphonophores from samples collected during the Albatross expedition in October 1904 to March 1905, but few samples were collected from the Eastern Tropical Pacific.…”