Biogenic habitat structure provided by temperate macroalgae change along a latitudinal gradient in ocean climate

[EN] Global warming is affecting all major ecosystems, including temperate reefs where canopy-forming seaweeds provide biogenic habitat. In contrast to the rapidly growing recognition of how climate affects the performance and distribution of individuals and populations, relatively little is known about possible links between climate and biogenic habitat structure. We examined the relationship between several ocean temperature characteristics, expressed on time-scales of days, months and years, on habitat patch characteristics on 24 subtidal temperate reefs along a latitudinal gradient (Western Australia; ca 34 to 27º S). Significant climate related variation in habitat structure was observed, even though the landscape cover of kelp and fucalean canopies did not change across the climate gradient: monospecific patches of kelp became increasingly dominant in warmer climates, at the expense of mixed kelp-fucalean canopies. The decline in mixed canopies was associated with an increase in the abundance of Sargassum spp., replacing a more diverse canopy assemblage of Scytothalia doryocarpa and several other large fucoids. There were no observed differences in the proportion of open gaps or gap characteristics. These habitat changes were closely related to patterns in minimum temperatures and temperature thresholds (days > 20 °C), presumably because temperate algae require cool periods for successful reproduction and recruitment (even if the adults can survive warmer temperatures). Although the observed habitat variation may appear subtle, similar structural differences have been linked to a range of effects on canopy-associated organisms through the provision of habitat and ecosystem engineering. Consequently, our study suggests that the magnitude of projected temperature increase is likely to cause changes in habitat structure and thereby indirectly affect numerous habitat-dependent plants and animals

Efecto de los misidáceos en la calidad de la puesta en el caballito de mar, Hippocampus hippocampus (Linnaeus, 1758)

[EN]The importance of a suitable feeding in reproduction and spawning quality of teleost fish has been recognized as one of the major ?bottlenecks? in new aquaculture species like seahorses. Mysidacea species has been described as one of the main food for temperate seahorse species (Hippocampus hippocampus and H. guttulatus) in the wild. On the other hand, Artemia has been employed usually as marine food for rearing fish, including seahorses. The aim of this work is to study the effect of two different live preys (Artemia vs Mysis) in spawning quality of H. hippocampus broodstock. The animals were fed two times per day, six times per week. Spawning episodes and larvae quality was recorded. Seahorse fed on mysis showed significantly better results (p<0.05) than Artemia treatment, regarding spawning events, number of offspring?s and size. This fact showed the high potential of mysis as live prey for seahorses or other ornamental species.

Reproductive biology of the sea cucumber Holothuria sanctori (Echinodermata: Holothuroidea)

[EN] The reproductive biology of the sea cucumber Holothuria sanctori was studied over 24 months (February 2009 to January 2011) at Gran Canaria through the gonad index and a combination of macro- and microscopic analysis of the gonads. Holothuria sanctori showed a 1:1 sex ratio and a seasonal reproductive cycle with a summer spawning: the mean gonad index showed a maximum (3.99±0.02) in summer (June-July) and a minimum (0.05±0.04) between late autumn (November) and early spring (March). Females had significantly wider gonad tubules than males. First maturity occurred at a size of 201 to 210 mm, a gutted body weight of 101 to 110 g and a total weight of 176 to 200 g. Holothuria sanctori shows a typical temperate species reproduction pattern. These results could be useful for managing current extractions of H. sanctori in the Mediterranean and in case a specific fishery is started in the eastern Atlantic region.