Macromedusae of Southern Brazil: temporal variation, population structure and biochemical composition

Abstract The objectives of this study were to record the macromedusae species on the north coast of Santa Catarina, and to estimate their population dynamics and variations in their biochemical composition, based on the specimens obtained in the by-catch of artisanal shrimp fishing between January 2012 and October 2014. Cohort analysis was performed to evaluate the population dynamic of the most frequent species. Biochemical analyses of the umbrellas were conducted on their water, carbohydrate, protein, lipid, ash and metals contents. Six species of macromedusae were found: Chiropsalmus quadrumanus and Tamoya haplonema (Cubozoa); Olindias sambaquiensis and Rhacostoma atlanticum (Hydrozoa), and Chrysaora lactea and Lychnorhiza lucerna (Scyphozoa). The species with the highest occurrence, and typical of the region, were Olindias sambaquiensis and Rhacostoma atlanticum. These species showed high inter-year variability, the highest densities being observed between autumn and winter 2014, associated with a less severe winter and coastal water with higher salinity. The distribution of size classes of O. sambaquiensis suggests two well-defined cohorts in spring/summer and in autumn/winter. R. atlanticum showed continuous reproduction and inter-year variation but a high value for protein content related to the reproductive peak in autumn. However, the Cubozoa species showed higher organic matter and metal content than the other classes

Environmental patterns and biomass distribution of gelatinous macrozooplankton. Three study cases in the South-western Atlantic Ocean

Periodic swarms or blooms of gelatinous macrozooplankton have a negative effect on many human activities such as tourism, fisheries, and industry, but for several reasons (sampling procedures, underestimation of their real abundance, etc.), they have often been neglected in the local literature. The high spatial resolution exercise of the South-western Atlantic anchovy Engraulis anchoita Recruitment Project (SARP) was therefore also suitable for estimating standing stocks of jelly macrozooplankton, attempting to establish particular environmental patterns exerting control on the spatial distribution of these facultative carnivorous predators in coastal frontal environments. These studies were carried out through a sampling programme on board the German R/V Meteor in three different systems, convergence and divergent, in the South-western Atlantic Ocean: Region A (42°S) on the Argentine shelf, characterised by tidal mixing fronts; Region B (36°S), the freshwater outflow from Río de la Plata; and Region C (28°S), under upwelling events in subtropical waters on the Brazilian shelf. In general, a dominance of gelatinous macrozooplankton, compared with the other fraction of macrozooplankton and micronekton was observed. Mean standing stock of the gelatinous zooplankton was always greater than 50% of organic carbon (org. C) in every section analysed. The lobate ctenophore Mnemiopsis leidyi dominated the zooplankton biomass in Region A, Argentina. It represented 60% of total org. C and was more abundant at the stratified zone of the front. Ctenophores were also dominant in Region B, Río de la Plata, where the related species Mnemiopsis mccradyi and the cydippid ctenophore Pleurobrachia pileus comprised 81% of total org. C. Mnemiopsis was most common in areas of vertical thermal and saline stratification, while Pleurobrachia was dominant in the less stratified areas. Gelatinous zooplankton was also the principal component of the macrozooplankton biomass in Region C, Brazil. The hydromedusae Rhacostoma atlantica and Olindias sambaquiensis dominated both the total and gelatinous biomass (68% and 7% of total org. C), being always more abundant under lower thermal stratification. It was found that, both in convergent and divergent local systems, gelatinous plankton tended to aggregate in areas where the presence of isolines outcropping to the surface (associated with production processes) was observed. These results are discussed in the context of existing hypotheses regarding ecosystem production and food webs.No disponibl

Las medusas Scyphozoa de la Bahía Blanca, Argentina

Juvenils and adults of Chrysaora láctea, Aurelia aurita and Drymonema gorgo were found in Blanca Bay during summer and efirae of the two first occurred from October to January. These species are commonly found in Brazilian waters. Their occurrence in higher latitudes may be either due to the influence of warm waters coming from north or to the heating of local waters which could main tain their populations temporarily during spring and summer. In this period C. láctea and A. aurita may reproduce as it is suggested by the occurrence of their efirae in the surveyed area

Digenean metacercaria (Trematoda, Digenea, Lepocreadiidae) parasitizing "coelenterates" (Cnidaria, Scyphozoa and Ctenophora) from Southeastern Brazil

Metacercaria specimens of the genus Opechona (Trematoda: Digenea: Lepocreadiidae) are described parasitizing "coelenterates" (scyphomedusae and ctenophores) from Southeastern Brazil (São Paulo state). The worms are compared to other Opechona species occurring on the Brazilian coast, but no association has been made because only adult forms of these species have been described. Suppositions as to the possible transference of the parasites are made.<br>Exemplares de metacercárias do gênero Opechona (Trematoda: Digenea: Lepocreadiidae) são descritos parasitando "celenterados" (cifomedusas e ctenóforos) no sudeste do Brasil (estado de São Paulo). Os vermes foram comparados a outras espécies de Opechona ocorrentes no litoral brasileiro, porém nenhuma associação foi realizada devido às demais espécies terem sido descritas a partir de exemplares adultos. São apresentadas suposições sobre as possíveis formas de transferência dos parasitas

Recurrent jellyfish blooms are a consequence of global oscillations

A perceived recent increase in global jellyfish abundance has been portrayed as a symptom of degraded oceans. This perception is based primarily on a few case studies and anecdotal evidence, but a formal analysis of global temporal trends in jellyfish populations has been missing. Here, we analyze all available long-term datasets on changes in jellyfish abundance across multiple coastal stations, using linear and logistic mixed models and effect-size analysis to show that there is no robust evidence for a global increase in jellyfish. Although there has been a small linear increase in jellyfish since the 1970s, this trend was unsubstantiated by effect-size analysis that showed no difference in the proportion of increasing vs. decreasing jellyfish populations over all time periods examined. Rather, the strongest nonrandom trend indicated jellyfish populations undergo larger, worldwide oscillations with an approximate 20-y periodicity, including a rising phase during the 1990s that contributed to the perception of a global increase in jellyfish abundance. Sustained monitoring is required over the next decade to elucidate with statistical confidence whether the weak increasing linear trend in jellyfish after 1970 is an actual shift in the baseline or part of an oscillation. Irrespective of the nature of increase, given the potential damage posed by jellyfish blooms to fisheries, tourism, and other human industries, our findings foretell recurrent phases of rise and fall in jellyfish populations that society should be prepared to face