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

Abstract

This work is a part of the Taiwan Cooperative Oceanic Fisheries Investigation, the first large scale hydrographic and plankton survey around Taiwan (21–26°N, 119–123°E). The present study examined the influence of hydrodynamic and biological variables driven by monsoon system on the siphonophore assemblages through an annual cycle in 2004. Calycophorans, namely Chelophyes appendiculata, Diphyes chamissonis, Lensia subtiloides, Bassia bassensis, and Muggiaea atlantica, were the most dominant siphonophore species. Maximum abundance of these dominant species generally occurred during the warm period (May and August), while M. atlantica had a significantly peak abundance in February. Although no apparently temporal difference in siphonophore abundance was observed in the study, siphonophore assemblage was more diverse in August than in other sampling times. Result of a cluster analysis indicated that assemblage structure of siphonophores in the waters around Taiwan varied at temporal and spatial scales during the sampling period. The intrusions of the Kuroshio Branch Current and China Coastal Current to the study area play an important role on the transportation of siphonophores. Also, the distribution of siphonophore assemblage was closely related to the hydrographic characteristics, with temperature, chlorophyll a concentration, and zooplankton abundance being the major environmental factors affecting the spatio-temporal variability of siphonophores. This study contributes substantially to the new knowledge of the siphonophore assemblage in the tropical-temperate waters of Taiwan.

18S rRNA gene sequences of leptocephalus gut contents, particulate organic matter, and biological oceanographic conditions in the western North Pacific

“…The seasonal distribution and abundance of siphonophores are primarily attributed to fluctuations in environmental factors that control the sexual cycle 33 , 34 , and in a favorable environment, siphonophores can rapidly reproduce asexually 35 – 37 . In the western North Pacific Ocean, spatiotemporal variation in siphonophore assemblages is closely related to temperature, salinity, chlorophyll concentration, and zooplankton abundance, which are strongly influenced by ocean currents 38 and seasonal monsoons 39 . For instance, in summer, the southwestern monsoon increases the species number and abundance of siphonophores, whereas in winter the northeast monsoon decreases species number and abundance 40 .…”

Siphonophores from surface waters of the Colombian Pacific Ocean

“…Otherwise the species observed here from the CPO have all been recorded previously in the Pacific Ocean (Alvariño, 1971; Pagès et al , 1990). Species such as A. eschscholtzii , Abylopsis tetragona , B. bassensis , C. appendiculata , C. contorta , E. spiralis , M. atlantica , S. chuni and S. quadrivalvis are widely distributed in tropical waters of the Eastern Pacific (Gasca & Suárez, 1992a, b) and the Caribbean (Gasca, 1999), further west in the tropical Pacific (Pagès et al , 1990; Lo et al , 2012, 2014; Hsieh et al , 2013) as well as cooler Chilean (Palma, 1999; Palma & Silva, 2004) and Peruvian (Ayón et al , 2008) waters. Most species of siphonophore have a near global distribution (Mackie et al , 1988), with all of the species found here reported from either the Atlantic (Pugh, 1999) or the Indian oceans (Daniel, 1974).…”

“…In waters of the Mediterranean Sea, Fernández de Puelles et al (2007) found a positive correlation between the abundance of Muggiaea , Lensia , Eudoxoides and Abylopsis , and abundance of copepods. In subtropical waters of Taiwan, Lo et al (2014) suggested that the abundance and distribution of siphonophores are related to zooplankton biomass.…”

“…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.…”

Shifts in the Assemblage of Summer Mesopelagic Fish Larvae in the Gaoping Waters of Southwestern Taiwan: A Comparison between El Niño Events and Regular Years

“…In contrast to the increase of upper layer nutrients levels through mixing, terrestrial outflow is the main source of nutrients in the Gaoping waters [33,34]. Plentiful nutrients have entrained higher phytoplankton production, which were the food resources for grazers such as copepods and their predators, such as gelatinous carnivores and fish larvae [61][62][63]. However, climateassociated fluctuations in the timing and amount of precipitation influence river discharge, which in turn affects the entrainment of nutrients and the magnitude of phytoplankton production [21,64].…”