Long-term changes in the planktonic cnidarian community in a mesoscale area of the NW Mediterranean

Abstract

In the present work, possible long-term changes in the planktonic cnidarian community were investigated by analyzing (1) species and community spatial distribution patterns, (2) variations in abundance and (3) changes in species richness during three mesoscale surveys representative of the climatic and anthropogenic changes that have occurred during the last three decades (years: 1983, 2004 and 2011) in the NW Mediterranean. These surveys were conducted during the summer (June) along the Catalan coast. All surveys covered the same area, used the same sampling methodology, and taxonomic identification was conducted by the same team of experts. An increase in the abundance of total cnidaria was found from 1983 to 2011. The siphonophore Muggiaea atlantica and the hydromedusa Aglaura hemistoma were the most abundant species, while Muggiaea kochii presented the largest abundance increment over time. Temperature was the main environmental parameter driving significant differences in the cnidarian community composition, abundance and spatial distribution patterns among the surveys. Our results suggest that in the current climate change scenario, warm-water species abundances will be positively favored, and the community will suffer changes in their latitudinal distribution patterns. We consider it extremely important to study and monitor gelatinous zooplankton in mesoscale spatial areas to understand not only long-term changes in abundances but also changes in their spatial distributions since spatial changes are sensitive indicators of climate change.

Macroscale abundance patterns of hydromedusae in the temperate Southwestern Atlantic (27°–56° S)

“…Considering that our study area is mostly coastal, it is not surprising that the highest diversities were found in coastal environments and, consequently, were mainly associated with the contribution of meroplanktonic hydromedusan species (particularly those belonging to Anthoathecata and Leptothecata orders) [38]. This result is in accordance with hydromedusan patterns observed in coastal ecosystems at different latitudes worldwide [10,41,45,85–89]. The hydrological dynamics and geomorphology of coastal environments would favor the development of hydromedusan species with benthic phases because costs are usually associated to retentive processes, which may favor reproductive encounters, and provide a wide offer of substrata, which enhances the probability of polyp settlement and success (see [66,90]).…”

“…tetraphylla in El Rincón region and massive accumulations in recent years reveal that its abundance distribution is expanding southwards [50]. Changes in the latitudinal distribution and abundance patterns of the species are one of the signals of climate warming, and warm-water species abundances would be positively favored [10,19,51,52]. Indeed, rising temperatures and drier conditions have been recorded in the Bahía Blanca Estuary affecting the plankton communities (i.e., producing changes in phenology and composition) via alterations of the water chemistry and predator-prey interactions [53,54].…”

Changes in the spawning habitat of two small pelagic fish in the Northwestern Mediterranean

“…In addition to trophic limitation of fish larvae, changes in plankton composition and abundance may have important effects on the condition of juvenile and adult fishes, determining demographic parameters such as reproduction, growth, and mortality, and these changes have been proposed as important drivers of small pelagic population variability in the NW Mediterranean (Brosset et al, ; Coll et al, ; Saraux et al, ). Another indirect factor related to changing plankton dynamics is the increasing abundance and changes in gelatinous plankton composition that have been recorded in the NW Mediterranean (Guerrero, Gili, Grinyó, Raya, & Sabatés, ; Molinero et al, ). Jellyfish, specifically scyphozoan medusae, may negatively affect pelagic fish due to competition for food or through direct predation on their fish eggs and larvae (Purcell & Arai, ).…”

Mediterráneo: realidad y retos de nuestro entorno natural

“…Spatiotemporal changes in egg and larval abundance can be a sensitive indicator of environmental change. The predicted increase in water temperatures, lower wind stress and precipitation, and the consequently higher stratification have reported to drive changes in the composition and phenology of planktonic communities (moLInero et al, 2005; and to increase the population size of gelatinous carnivores (moLInero, 2008;guerrero et al, 2018). Jellyfish, specifically scyphozoan medusae, may negatively affect fish due to competition for food or through direct predation on their fish eggs and larvae (purceLL & araI, 2001).…”