Cyanea (jellyfish)

About: Cyanea (jellyfish) is a research topic. Over the lifetime, 133 publications have been published within this topic receiving 3167 citations.

Interannual variability in abundance of North Sea jellyfish and links to the North Atlantic Oscillation

Abstract: Pronounced interannual variability in the abundance of medusae of the jellyfish species Aurelia aurita, Cyanea lamarckii, and Cyanea capillata (Phylum Cnidaria, Class Scyphozoa) in the North Sea was evident in data arising from the International Council for the Exploration of the Seas International 0-group Gadoid Surveys between 1971 and 1986. Possible climatic forcing of jellyfish abundance, via the North Atlantic Oscillation (NAO), was investigated with data on medusae from four areas of the North Sea (east of Scotland, north of Scotland, east of Shetland, and west of northern Denmark). There were significant inverse relationships between medusa abundance and the NAO Index (December‐March) in two regions: west of northern Denmark (A. aurita r 2 5 0.70, P 5 0.003, n 5 10; C. lamarckii r 2 5 0.74, P 5 0.002, n 5 10) and east of Scotland (A. aurita r 2 5 0.53, P 5 0.008, n 5 12). Fluctuations in the abundance of A. aurita and C. lamarckii medusae might be linked to hydroclimatic changes induced through atmospheric effects (as encapsulated in the NAO Index) on wind stress, temperature, and currents. These fundamental hydroclimatic changes alter the timing of spring phytoplankton blooms and zooplankton community composition. Predation by an abundance of medusae on zooplankton and ichthyoplankton could affect the North Sea ecosystem through top-down and bottom-up mechanisms. Because the NAO is presently in a high phase, climatic conditions could be serving to depress the abundance of medusae: a future reversal of the NAO might favor jellyfish and weaken the persistence or recovery of fisheries.

Extension of methods for jellyfish and ctenophore trophic ecology to large-scale research

Abstract: Science has rapidly expanded its frontiers with new technologies in the 20th Century. Oceanography now is studied routinely by satellite. Predictive models are on global scales. At the same time, blooms of jellyfish and ctenophores have become problematic, especially after 1980. Although we have learned a great deal about gelatinous zooplankton ecology in the 20th Century on local scales, we generally have not scaled-up to estimate the extent, the causes, or effects of large blooms. In this age of global science, research on gelatinous zooplankton needs to utilize large-scale approaches and predictive equations. Some current techniques enable jellyfish populations (aerial, towed cameras), feeding (metabolic rates, stable isotopes), and dynamics (predictive modeling) to be studied over large spatial and temporal scales. I use examples of scyphomedusae (Aurelia spp., Cyanea capillata, Chrysaoraquinquecirrha) and Mnemiopsis leidyi ctenophores, for which considerable data exist, to explore expanding from local to global scales of jellyfish trophic ecology. Regression analyses showed that feeding rates of Aurelia spp. (FR in copepods eaten medusa−1 d−1) generally could be estimated ±50% from in situ data on medusa wet weight (WW) and copepod density; temperature was not a significant factor. FR of C. capillata and C.quinquecirrha were similar to those of Aurelia spp.; the combined scyphomedusa regression underestimated measured FR of C.quinquecirrha and Aurelia spp. by 50% and 180%, respectively, and overestimated measured FR of C. capillata by 25%. Clearance rates (CR in liters cleared of copepods ctenophore−1 d−1) of M. leidyi were reduced in small containers (≤20 l), and a ratio of container-volume to ctenophore-volume of at least 2,500:1 is recommended for feeding experiments. Clearance rates were significantly related to ctenophore WW, but not to prey density or temperature, and estimated rates within 10–159%. Respiration rates of medusae and ctenophores were similar across habitats with greatly ambient different temperatures (10–30°C), and can be predicted from regressions using only mass. These regressions may permit estimation of feeding effects of gelatinous predators without exhaustive collection of feeding data in situ. I recommend that data on feeding and metabolism of jellyfish and ctenophores be entered in a database to allow generalized predictive relationships to be developed to promote inclusion of these important predators in ecosystem studies and models.

Substrate choice and settlement preferences of planula larvae of five Scyphozoa (Cnidaria) from German Bight, North Sea

Abstract: The settlement behaviour of planula larvae and their development to young polyps was investigated in laboratory experiments in five scyphozoan species [Aurelia aurita (L.), Cyanea capillata (L.), Cyanea lamarckii Peron and Leseur, Chrysaora hysoscella (L.), and Rhizostoma octopus (L.)]. The undersides of settling plates were strongly preferred for settlement. Shells, the only natural substrate type offered, were less attractive than artificial substrates (concrete, machined wood, polyethylene, and glass). The advantages of colonization of substrate undersides for survival and reproduction of polyps are discussed. It is supposed that the increase of artificial substrates in our seas, due to marine litter pollution and submarine building activities, enlarge the areas of distribution of scyphozoan polyps, in coastal as well as in off-shore regions. Subsequent increases in ephyra production by polyps are probably one reason for the increase in mass occurrences of jellyfish recognized worldwide during the last few decades. It is suggested that the early developmental stages in the cnidarian life cycle, the planula larvae, and the polyps, play the key role in the development of jellyfish outbursts.