Search

Water temperature directly affects life cycles, reproductive periods, and metabolism of organisms living the oceans, especially in the surface zones. Due to the ocean warming, changes in water stratification and primary productivity are affecting trophic chains in sensitive world areas, such as the Mediterranean Sea. Benthic and pelagic cnidarians exhibit complex responses to climatic conditions. For example, the structure and phenology of the Mediterranean hydrozoan community displayed marked changes in species composition, bathymetric distribution, and reproductive timing over the last decades. The regional species pool remained stable in terms of species numbers but not in terms of species identity. When the Scyphozoa group is considered, we observe that Pelagia noctiluca (among the most abundant jellyfish in the Mediterranean Sea and eastern Atlantic waters) has increasingly frequent massive outbreaks associated to warmer winters. Variations in metabolic activities, such as respiration and excretion, are strongly temperature-dependent, with direct increment of energetic costs with jellyfish size and temperature, leading to growth rate reduction. Water temperature affects sexual reproduction through changes in the energy storage and gonad development cycles. Anthozoan life cycles depend also on primary productivity and temperature: gonadal production and spawning are tightly related in shallow populations (0–30 m depth) with the spring-summer temperature trends and autumn food availability. Overall, the energy transferred from the mother colonies to the offspring may decrease, negatively affecting their potential to settle, metamorphose and feed during the first months of their lives, eventually impairing the dominance of long-living cnidarian suspension feeders in shallow benthic habitats. In this review, we describe the already ongoing effects of sea warming on several features of cnidarian reproduction, trying to elucidate how reproductive traits and potential dispersion will be affected by the cascade effects of increasing temperature in the Mediterranean Sea.

One hundred and six specimens of the Por’s goatfish, Upeneus pori Ben-Tuvia & Golani (1989), a Lessepsian species native to the Western Indian Ocean, were collected from bottom trawlers’ catches from 2012 to 2016 on the deep shelf off the southern coast of Lampedusa Island (Strait of Sicily, Central Mediterranean Sea). Since it first appeared in Iskenderun Bay (Turkey) in 1950, the Por’s goatfish has quickly spread in Levantine Sea waters to become a commercial species used by local fisheries, while continuing its range expansion along the south-eastern coasts of the Mediterranean. Because the Strait of Sicily currently represents the westernmost sector of this species distribution area, it might serve as a stepping-stone for this species’ expansion in the western basin of the Mediterranean. Supporting this hypothesis was our finding of specimens with post-spawning gonads. The pattern of westward expansion by the Por’s goatfish in the Mediterranean Sea and its settlement in the Strait of Sicily are discussed in relation to the warming trend over the last 30years.

Leiopathes glaberrima is an important component of the deep coral forests of the Mediterranean Sea enhancing benthic biodiversity and forming an essential habitat for many marine organisms. It is a sessile species with high longevity; it is therefore highly affected by fishing impacts and has been listed as a representative taxon of Vulnerable Marine Ecoystems (VMEs). Since information on spatial distribution of L. glaberrima is still scanty and fragmented, an updated synopsis of its distribution in the Mediterranean is given, including two new records in the Strait of Sicily. On the basis of this updated information, hotspots of black coral off the Carloforte Island in the Sardinian Sea, on the Marco Bank and off the Pontine Islands in the Southern Tyrrhenian Sea, and on the Malta Graben in the Strait of Sicily are proposed for implementation of Fishery Restricted Areas.